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                                                    COASTAL ZONE INFORMATION'.@CENTER-.,

           OCE-AN-S-88-
           CONFERENCE AND EXPOSITION PRESENTED BY MTS-OES-IEEE IN COOPERATION WITH THE PORT OF'BXLTIMORE
           ALTIMORE CONVENTION CENTER, BALTIMORE, MARYLAND OCTOBER 31 -NOVEMBER 2, 1988
           DPNALD SCHAEFER, GOVERNOR OF MARYLAND, HONORARY CHAIRMAN
           A,pMIRAL PAUL A. YOST. COMMANDANT UNITED STATES COAST GUARD, GENERAL CHAIRMAN

                                     A

                                                                                                                            88-CH2585-&'

                                                                                                                                   ___too

                -,@@PROQEEDINGS
                                                                                                                               VOL       2

                                                               I'A

                                                                              Ul.

                   GC                                                 'o,
                   1001
                   .025
                   1988
                   v. 2                                                                  v.

                                                    COASTAL     ZONE   INFORMATIOW'CENTER.I.

              FERENCE AND EXPOSITION PRESENTED BY MTS-OES-IEEE IN COOPERATION WITH THE PORT OF'BALTIMORE
               IMORE CONVENTION CENTER, BALTIMORE, MARYLAND OCTOBER 31 -NOVEMBER 2, 1988
               LID SCHAEFER, GOVERNOR OF MARYLAND, HONORARY CHAIRMAN
              IRAL PAUL A. YOST, COMMANDANT UNITED STATES COAST GUARD, GENERAL CHAIRMAN

    		            OCEANS 88

                          A Partnership of Marine Interests

                                   Property Of CSC Library

                                          PROCEEDINGS

                                           Conference Sponsored by
                                          Marine Technology Society
                                                    IEEE

                                             Baltimore, Maryland
                                        October 31-November 2, 1988

                          U.S. DEPARTMENT OF COMMERCE NOAA
                          COASTAL SERVICES CENTER
                          2234 SOUTH HOBSON AVENUE
                          CHARLESTON., SC 29405-2413

                                                                 IEEE Catalog Number 88-CH2585-8

                                           Oceans '88 Proceedings

                                          Volume 1: Pages 1 to 2 74
                                          Volume 2: Pages 2 75 to 718
                                          Volume 3: Pages 719 to 1086
                                          Volume 4: Pages 1087 to 1732

                                   Copies of the Oceans '88 Proceedings are available from:

                                                     The IEEE Service Center
                                                          445 Hoes Lane
                                                      Piscataway, NJ. 0885

                                                                and
                                                 The Marine Technology Society
                                              2000 Florida Avenue, N.W., Suite 500
                                                     Washington, D.C. 20006

                  Copyright and Reprint Permissions: Abstracting is permitted with credit to the source. Libraries
                  are permitted to photocopy beyond the limits of U.S. copyright law for private use of patrons
                  those articles in this collection that carry a code at the bottom of the first page, provided
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                  All rights reserved. Copyright c 1988 by The Institute of Electrical and Electronics Engineers.

                                                                                IEEE Catalog Number 88-CH2585-8

                         OCEANS '88

                           Proceedings

                            Volume Two

                                                           Table of Contents

              PLASTICS IN OUR OCEANS: WHAT ARE WE DOING                             MESOCOSMS AS TOOLS FOR COASTAL AND ESTUARINE
              ABOUTIT?                                                              ENVIRONMENTAL RESEARCH-1

              Chairman:                                                             Chairman:
                B. Griswold                                                           G. F. Mayer
                OAR, National Oceanic and Atmospheric                                 National Oceanic and Atmospheric Administration
                   Administration
                                                                                    E. Klos                                                 1529
              J. M. Coe and A. R. Bunn                                    I         An Experimental Estuarine Salinity Gradient
              Marine Debris and the Solid Waste Disposal Crisis
                                                                                    S. W. Nixon and S. W. Granger                           1604
              D. Cottingham                                               6         Development of Experimental Ecosystems for the
              Federal Programs and Plastics in the Oceans                           Study of Coastal Lagoons

              X. Augerot                                              .1711         J. G. Sanders and G. F. Riedel                            23
              Sea Grant Faces Oceans of Plastic                                     The Use of Enclosed Ecosystemsfor the Study of
                                                                                    Cycling and Impact of Trace Elements
              K. J. O'Hara                                               12
              Education and Awareness: Keys to Solving the Marine                   S. J. Cibik, J..G. Sanders and C. F. D'Elia               29
              Debris Problem                                                        Interactions Between Insolation and Nutrient Loading
                                                                                    and the Response of Estuarine Phytoplankton
              J. R. Whitehead                                          1507
              Reducing Plastic Pollution in the Mar    'ine Environment-            MESOCOSMS AS TOOLS FOR COASTAL AND ESTUARINE
              The U.S. Coast Guardand Implementation. of Annex V                    ENVIRONMENTAL RESEARCH-11
              of MARPOL 73178

                                                                                    Chairman:
              CONTINENTAL SHELF ENVIRONMENTAL RESEARCH                                R. E. Turner
                                                                                      Center for Wetlands Resources,
              Chairman:                                                                 Louisiana State University
                W. W. Schroeder
                University of Alabama                                               A. G. Chalmers                                          1652
                                                                                    Experimental Manipulations of Drainage in a Georgia
              R. Rezak and D. W. McGrail                              1602          Saltmarsh: Lessons Learned
              Geology and Hydrology of Reefs and Banks Offshore
              Texas and Louisiana.                                                  M. R. DeVoe, M. E. Tompkins and J. M. Dean                35
                                                                                    South Carolina's Coastal Wetland Impoundment
              W. W. Schroeder, M. R. Dardeau, J. J. Dindo, P.                       Project (CWIP): Relationship of Large-Scale Research
              Fleischer, K. L. Heck, Jr. and A. W. Schultz               17         to Policy and Management
              Geological and Biological Aspects of Hardbottom
              Environments on the LMAFLA Shelf, Northern Gulf of                    R. E. Turner                                              41
              Mexico                                                                Experimental Marsh Management Systems in Louisiana

              W. W. Schroeder, R. Rezak and T. J. Bright                 22         A. G. van der Valk, B. D. J. Batt, H. R. Murkin, P. J.
              Video Documentation of Hardbottom Environments                        Caldwell and J. A. Kadlec                                 46
                                                                                    The Marsh Ecology Research Program (MERP): The
                                                                                    Organization and Administration of a Long-Term
                                                                                    Mesocosm Study

                                                                               iv.

            TECHNICAL ADVANCES IN SEAFOOD TECHNOLOGY AND                          WATER REUSE ON ONSHORE MARICULTURE AND
            SAFETY                                                                PROCESSING FACILITIES

            Chairman:                                                             Chairman-
               D. Attaway                                                           R. Becker
               Sea Grant, National Oceanic and Atmospheric                          Louisiana State University
                 Administration
                                                                                  J. M. Fox and A. L. Chauvin                            1536
            R. R. Colwell                                           1606          Deputation of Oysters in a Closed Recirculating
            New Approaches for IndiceslMonitoring Microbial                       System
            Pathogens in Seafood
                                                                                  M. P. Thomasson, D. G. Burden and R. F. Malone 70
            J. Liston                                                 52          Micro-Computer Based Design of Recirculating
            Microorgam   .sms as a Cause of Economic Loss to the                  Systems for the Production of Soft-shell Blue Crabs
            Seafood Industry                                                      (Callinectes sapidus)

            G. J. Flick, Jr.                                          56          G. E. Kaiser and F. W. Wheaton                            76
            Sea Grant Advances in Seafood Science and                             Computerized Rapid Measurement of Ammonia
            Technology                                                            Concentration in Aquaculture Systems

            S. Garrett and M. Meyburn.                                            K. Rausch, W. H. Zachritz II, T. C. T. Y-Hsieh and
            Development of New Approaches to Seafood                              R. F. Malone                                              84
            Inspection                                                            Use of Automated Holding Systems for Initial Off-
                                                                                  Flavor Purging of the Rangia Clam, Rangia cuneata
            TECHNICAL ADVANCES IN SEAFOOD TECHNOLOGY AND
            SAFETY                                                                GULF OF MEXICO CHEMOSYNTHETIC PETROLEUM SEEP
                                                                                  COMMUNITIES
            Chairman:
               G. J. Flick, Jr.                                                   Chairman:
               Virginia Polytechnic Institute                                       R. Carney'
                                                                                    Louisiana State University
            R. C. Lindsay                                             61
            Flavor Chemistry and Seafood Quality Factors                          1. MacDonald, R. Carney and D. Wilkinson                  90
                                                                                  Gulf of Mexico Chemosynthetic Communities at Oil
            H. 0. Hultin                                              66          Seeps: Estimating Total Density
            Technical Problems and Opportunities Related to
            Utilization of Our Seafood Resources                                  R. S. Carney                                              96
                                                                                  Emerging Issues of Environmental Impact to Deep-Sea
            J. P. Zikakis                                           1608          Chemosynthetic Petroleum Seep Communities
            A Biotechnological System for     the Utilization of Waste
            Products of the Seafood and Cheese Minufqctuiffig                     H. H. Roberts, R. Sassen and P. Abaron                    101
            Industries                                                            Petroleum -Derived Authigenic Carbonates of the
                                                                                  Louisiana Continental Slope
            A. P. Bimbo                                             1513
            The Production of Menhaden Surimi

                                                                              V.

               UNDERSEA VEHICLES AND PLATFORMS FOR SCIENCE                              OIL AND GAS INDUSTRIES CONFLICT
               APPLICATIONS
                                                                                        Chairmen:
               Chairman:                                                                   R. W. Middleton
                  A. N. Kalvaitis                                                          Minerals Management Service
                  National Undersea Research Program,                                      M. Holliday
                    National Oceanic and Atmospheric Administration                        National Marine Fisheries Service
               G. A. Smith and R. S. Rounds                                io6          J. Brashier                                                 136
               Scientific, Technological and Social Impact of NOAA's                    Coexistence of Fishing and Oil and Gas Industries in
               Mobile Undersea Research Habitat                                         the Gulf of Mexico
               P. J. Auster, L. L. Stewart and H. Sprunk                 1286           B. R. Clark                                                 143
               Scientific Imaging Problems and Solutions for ROVs
                                                                                        Potential Conflicts Between Oil and Gas Industry
               L. L. Stewart and P. J. Auster                            1610           Activities and Commercial Fishing
               Low Cost ROVs for Science                                                R. M. Meyer                                                 146
               R. A. Cooper and 1. G. Babb                                 112          Information on Fisheries Risk Assessment in the Alaska
               Manned Submersibles Support 2 Wide Range of                              OCS Region
               Underwater Research in New England and the Great                         R. C. Wingert                                               150
               Lakes                                                                    Geophysical Survey and Commercial Fishing Conflicts,
               R. 1. Wicklund and B. L. Olla                               119          Environmental Studies and Conflict Mitigation in the
               Field Research Programs at the Caribbean Marine                          Minerals Management Service Pacific OCS Region
               Research Center-National Undersea Research Program                       A. S. Knaster                                               156
                                                                                        The Use of Alternative Dispute Resolution in
               OCS FISHERIES AND RESOURCES                                              Resolving Outer Continental Shelf Disputes

               Chairmen:                                                                CUMULATIVE ENVIRONMENTAL EFFECTS OF THE OIL AND
                  R. W. Middleton                                                       GAS LEASING PROGRAM-I
                  Minerals Management Service
                  M. Holliday                                                           Chairmen:
                  National Marine Fisheries Service                                        J. Goll
                                                                                           Minerals Management Service
               R. W. Middleton                                             123             J. M. Teal
               Oil and Gas Industry Conflicts on       the Outer                           Woods Hole Oceanographic Institute
               Continental Shelf
               D. Christensen                                            1624           D. V. Aurand                                                161
               Outer Continental Shelf Fisheries and Resources in the                   The Future of the Department of the Interior OCS
               Northeast Region                                                         Studies Program
               R. J. Essig                                                 127          T. Chico                                                    166
               Outer Continental Shelf Fishery Resources of the                         Air Quality Issues, Environmental Studies, and
               South Atlantic                                                           Cumulative Impacts in the Pacific OCS Region
               B. G. Thompson                                            1613           R. E. Miller                                                172
               Outer Continental Shelf Fisheries and Resources in the                   Georges Bank Monitoring Program: A Summary
               Gulf of Mexico                                                           J. M. Teal                                                  177
               S. Koplin                                                   132          The Role of the Scientific Advisory Committee, Outer
                                                                                        Continental Shelf Program of Minerals Management
               The Outer Continental Shelf Fishery Resources of the                     Service
               Pacific Coast

                                                                                   vi.

            CUMULATIVE ENVIRONMENTAL EFFECTS OF THE OIL AND                        OIL AND GAS EXPLORATION-H
            GAS LEASING PROGRAM-11
                                                                                   Chairmen:
            Chairmen:                                                                J. R. Pearcy
              J. Goll                                                                Minerals Management Service
              Minerals Management Service                                            C. Welling
              J. M. Teal                                                             Ocean Minerals Co.
              Woods Hole Oceanographic Institute
                                                                                   C. A. Dunkel                                             208
            R. M. Rogers                                              953          A Qu2litative Assessment of the Hydrocarbon Potential
            Factors Contributing to Wetland Loss in the Coastal                    of the Washington and Oregon Continental Shelf
            Central Gulf of Mexico
                                                                                   J. M. Galloway and M. R. Brickey                        1611
            S. D. Treacy                                              180          The Hydrocarbon Potential of the Federal OCS,
            The Minerals Management Service Bowhead Whale                          Offshore Northern C21ifomi2
            Monitoring Program and Its Applications
                                                                                   J. Kennedy and C. Grant                                  213
            R. B. Clark                                               184          Impact of the Oil-be2ring Monterey Formation on
            Impact of Offshore Oil Operations in the North Sea                     Undiscovered Resources of Offshore C21ifornia

            J. P. Zippin                                             1615          S. Sorenson, C. Alonzo and M. Ibrahim                   1612
            Cumulative Environmental Effects of the Department                     Wilson Rock Field: A Case History
            of the Interior's Offshore Oil and Gas Program: 1987
            Report to Congress                                                     OIL AND GAS RESOURCE MANAGEMENT

            OIL AND GAS EXPLORATION-1                                              Chairmen:
                                                                                     R. V. Amato
            Chairman:                                                                Minerals Management Service
              J. R. Pearcy                                                           C. Welling
              Minerals Management Service                                            Ocean Minerals Co.
            F. R. Keer                                                188          G. M. Edson                                              219
            Geologic Characteristics of an Atlantic OCS Gas                        The Ancient Atlantic Reef Trend
            Discovery and Its Implications
            P. K. Ray                                                 193          B. J. Bascle                                             223
            Hydrocarbon Potential of the Deepwiter (600 Feet)                      The Effect of Exploration on Resource Estimates for
            Gulf of Mexico                                                         the Alaska Outer Continental Shelf
            W. E. Sweet and J. C. Reed                                202          D. Mayerson                                              229
            Correlation of Cenozoic Sediments-Gulf of Mexico                       Pre-lease Geophysical Permitting for the Pacific OCS:
            Outer Continental Shelf                                                Procedures, Problems, and Solutions

                                                                                   D. A. Steffy                                             235
                                                                                   Post-Lease Sale Exploration of the Navarin Basin,
                                                                                   Bering Sea, Alaska

                                                                             vii.

              OFFSHORE DRILLING-ENVIRONMENTAL STUDIES                                ACOUSTIC APPLICATIONS-II

              Chairman:                                                              Chairman:
                 D. Cottingham                                                          A. 1. Eller
                 National Oceanic and Atmospheric Administration                        Science Applications International Corp.

              D. K. Fran(;ois                                            241         L. C. Haines,  'W. W. Renner and A. I. Eller              295
              Environmental Studies and Impact Assessment on the                     Prediction System for Acoustic Returns from Ocean
              Atlantic Outer Continental Shelf                                       Bathymetry

              R. B. Krahl and C. E. Smith                                250         G,,. P. Vellemarette                                      298
              Developing Technologies for Offshore Oiland Gas                        P@Ogrammable Subsurface Acoustic Recording System
              Structures in Frontier and Hazardous Areas
                                                                                     D. F. McCammon                                            3o4
              OCEAN LEASING AND DEVELOPMENT                                          The Relationship Between Acoustic Bottom Loss and
                                                                                     the Geoacoustic Properties of the Sediment
              Chairman:
                 G. Pettrazzulo                                                      ACOUSTICS-NOISE
                 Technical Resources Inc.
                                                                                     Chairmen:
              S. Ashmore                                                 259            D. J. Ramsdale
              Offshore Leasing Boundaries Along the Receding                            Naval Ocean R&D Activity
              Alaskan Coastline                                                         N. Miller
              T. J. Mac Gillvray                                         262            West Sound Association
              Development and Analysis of DCF Computer Models                        W. S. Hodgkiss                                            310
              for EEZ Marine Mining                                                  Source Ship Contamination Removal in a Broadband
              M. E. Dunaway and P. Schroeder                             268         Vertical Array Experiment
              Minimizing Anchoring Impacts During Construction of                    R. J. Lataitis, G. B. Crawford and S. F. Clifford         315
              Offshore Oil and Gas Facilities                                        A New Acoustic Technique for Remote Measurement
              ACOUSTIC APPLICATIONS-1                                                of the Temporal Ocean Wave Spectrum

              Chairman:                                                              ACOUSTICS-PROPAGATION
                 A. I. Eller
                 Science Applications International Corp.                            Chairman:
                                                                                        D. G. Browning
              W. Hill, G. Chaplin and D. Nergaard                        275            Naval Underwater System Center
              Deep-Ocean Tests of an Acoustic Modem Insensitive
              to Multipath Distortion                                                D. G. Browning, P. M. Schiefele and R. H. Mellen 318
                                                                                     Attenuation of Low Frequency Sound in Ocean
              A. Novick                                                1617          Surface Ducts: Implications for Surface Loss Values
              A Shallow Water Sonar Performance Prediction
              System                                                                 W. J. Vetter                                             1540
                                                                                     On Ray Trajectories and Pathtimes for Acoustic
              R. L. Spooner                                              283         Propagation in a Medium with Velocity Gradients
              Signal Processing Using Spreadsheet Software
                                                                                     D. K. Roderick                                           1619
              J. M. Tattersall, J. A. Mingrone and P. C. King          1618          An Introduction to the Physics of Underwater Sound
              A VCR Based Digital Data Recorder for Underwater                       and Their Application to Passive Anti-Submarine
              Acoustics Multipath Measurements                                       Warfare

              L. Wu and A. Zielinski                                     287
              Multipath Rejection Using Narrow Beam Acoustic Link

                                                                                viii.

           ACOUSTICS-SIDE SCAN                                                 SEA BOTTOM PROPERTIES

           Chairman:                                                           Chairman:
              R. Walker                                                           M. Cruckshank
              USCG R&D Center                                                     University of Hawaii

           A. St. C. Wright                                       323          R. B. Perry                                            366
           The Wide Swath, Deep Towed SeaMARC                                  Mapping the Slopes of Expanding Continental Margins

           R. G. Asplin and C. G. Christensson                    329          C. de Moustier, T. Hylas and J. C. Phillips            372
           A New Generation Side Scan Sonar                                    Modifications and Improvements to the Sea Beam
                                                                               System On Board R/V Thomas Washington
           E. Kristof, A. Chandler and D. Schomette               335
           Using a Sector-Scan Sonar to Hunt for Shipwrecks                    D. E. Pryor                                            379
           Through Ice                                                         Theory and Test of Bathymetric Side Scan Sonar

           J. W. Nicholson and J. S, Jaffe                        338          S. M. Smith, J. S. Charters and J. M. Moore            385
           Side Scan Sonar Acoustic Variability                                Processing and Management of Underway Marine
                                                                               Geophysical Data at Scripps
           R. Gandy and S. Paulet                                 1620
           Realtime Side Scan Sonar Target Analysis                            R. L. Cloet                                            1636
                                                                               Implications of Using a Wide SWATH Sounding
           W. R. Abrams                                           344          System
           A Practical High Tech Advance in Side Scan Sonar
           Target Positioning and Analysis                                     SEDIMENT STUDIES-1

           AC OUSTIC DOPPLER CURRENT PROFILING                                 Chairman:
                                                                                  A. G. Young
           Chairman:                                                              FUGRO-McClelland
              H. R. Frey
              Office of Oceanography and Marine Assessments,                   S. K. Breeding and D. Lavoie                           391
                National Oceanic and Atmospheric Administration                Duomorph Sensing for Laboratory Measurement of
                                                                               Shear Modulus
           G. F. Appell, J. Gast, G. Williams and P. D. Bass      346
           Calibration of Acoustic Doppler Current Proftlers                   D. Lavoie, E. Mozley, R. Corwin, D. Lambert and
                                                                               P. Valent                                              397
           Y. Kuroda, G. Kai and K. Okuno                         353          The Use of 2 Towed, Direct-Current, Electrical
           Development of a Shipboard Acoustic Doppler                         Resistivity Array for the Classification of Marine
           Current Profiler                                                    Sediments

           D. Wilson, D. Bitterman and C. Roffer                  359          P. F. Wainwright, B. Humphrey and G. Stewart           405
           The Acoustic Doppler Current Profiling System at                    Sediment Contamination by Heavy Metals and
           AOML                                                                Hydrocarbons

                                                                           ix.

              SEDIMENT STUDIES-11                                               SATELLITE REMOTE SENSING

              Chairman:                                                         Chairmen:
                H. G. Herrmann III                                                D. E. Weissman
                Naval Facilities Engineering Command                              Hofstra University
              A. E. Hay, L. Huang, E. B. Colbourne, J.  Sheng and                 J. Gallagher
              A. J. Bowen                                           413           Naval Underwater Systems Center
              A High Speed Multi-Channel Data Acquisition System                M. R. Willard                                        162
              for Remote Acoustic Sediment Transport Studies                    Ocean Sensing Capabilities on Landsat 6
              D. G. Hazen, A. E. Hay and A. J. Bowen                419         S. W. McCandless, Jr. and J. Curlander                 479
              Design Considerations for RASTRAN-System 2                        The Influence of Packing Technologies on
              A. G. Young, L. V. Babb and R. L. Boggess             423         Environmental Application of Space-Based Synthetic
              Mini-Probes: A New Dimension in Offshore In Situ                  Aperture Radar
              Testing                                                           J. R. Benada, D. T. Cuddy andB. H. jai                 473
              K. L. Williams and L. J. Satkowiak                    428         Adapting the NSCAT Data System to Changing
              Bounded Beam Transmission Across a WaterlSind                     Requirements
              Interface, Experimentand Theory                                   W. B. Campbell and M. L. Weaks                        1626
                                                                                An Inexpensive Interactive Processing System for
              L. J. Satkowiak                                       433         NOAA Satellite Images
              Remote Sea Bottom Classification Utilizing the
              Ulvertech Bottom Profiler Parametric Source                       D. S. Bryant, A. M. Ponsford and S. K. Srivastava 485
                                                                                A Computer Package for the Parameter Optimization
              THE GREAT LAKES AS AN OCEANIC MICROCOSM                           of Groundwave Radar

              Chairman:
                L. Pittman
                Merchant Marine and Fisheries Committee,
                  U.S. Congress

              J. R. Krezoski                                        437
              Particle Reworking in Great Lakes Sediments: In-Situ
              Tracer Studies Using Rare Earth Elements

              J. R. Krezoski                                        442
              In-Situ Tracer Studies of Surficial Sediment Transport
              in the Great Lakes Using a Manned Submersible

              L. F. Boyer                                           443
              Video-Sediment-Proffie Camera Imagery in Marine and
              Freshwater Benthic Environments

              L. F. Boyer, R. J. Diaz and J. D. Hedrick             448
              Computer Image-Analysis Techniques and Video-
              Sediment-Profile Camera Enhancements Provide a
              Unique and Quantitative View of Life at or Beneath
              the Sediment-Waterface interface

                                                                            X.

            OCEAN APPLICATIONS OF REMOTELY SENSED MICROWAVE                    WATER COLUMN MEASUREMENTS-1
            TECHNIQUES
                                                                               Chairmen:
            Chairmen:                                                             R. S. Mesecar
              D. E. Weissman                                                      Oregon State University
              Hofstra University                                                  T. M. Dauphinee
              J. Gallagher                                                        National Research Council, Canada
              Naval Underwater Systems Center
                                                                               W. Kroebel                                             491
            C. Bostater and V. Klemas                              462         Results of Exact Investigations About the
            Remote Sensing of Physical and Biological Properties               Characteristics of the Extremely Fast and Accurately
            of Estuaries                                                       Measuring Kiel Multisonde and Representations About
                                                                               Its Newest Performance
            D. E. Weissman                                        1546
            The Dependence of the Microwave Radar Cross                        K.-H. Mahrt and C. Waldmann                            497
            Section on Ocean Surface Variables During the                      Field Proven High Speed Micro Optical Density
            Fasinex Experiment                                                 Profller Sampling 1000 Times Per Second with 10-6
                                                                               Precision
            W.-M. Boerner, A. B. Kostinski, B. D. James and
            M. Walther                                             454         R. Mesecar and C. Moser                                505
            Application of the Polarimetric Matched Image Filter               Multi-Sample Particle Flux Collector
            (PMIF) Technique to Clutter Removal in POL-SAR
            Images of the Ocean Environment                                    J. M. Moore, C. de Moustier and J. S. Charters         509
                                                                               Multi-Sensof Real-Time Data Acquisition and
            D. L. Murphy                                           467         Preprocessing at Sea
            Radar Detection of Oceanic Fronts
            L. S. Fedor and E. J. Walsh                           1697         WATER COLUMN MEASUREME      NTS-11
            Interpretation of SEASAT Radar Altimeter Returns                   Chairmen:
            from an Overflight of Ice in the Beaufort Sea                         J.Jaeger
            L. S. Fedor, G. S. Hayne and E. J. Walsh              1704            Honeywell Hydro Products
            Airborne Pulse-Limited Radar Altimeter Return                         K. Hill
            Waveform Characteristics over Ice in the Beaufort Sea                 Honeywell Hydro Products

                                                                               J. Wagner and R. Mesecar                               518
                                                                               A Common XBTIPersonal Computer Interface

                                                                               D. 1. Nebert, H. Saklad and G. Mimken                  1627
                                                                               CTD Data Acquisition Package

                                                                               H. Tremblay                                            522
                                                                               Hydroball-A New Expendable: Uses and Issues

                                                                           Xi.

               COMMUNICATIONS                                                       OCEAN ENGINEERING-I

               Chairman:                                                            Chairmen:
                 R. A. Buddenberg, USCG                                               C. A. Kohler
                 Office of Command and Control                                        USCG R&D Center
               R. A. Buddenberg and A. Givens                          526            R. Geminder
               Shipboard Tactical Computer: The Coast Guard's                         Mechanic Research Inc.
               Combat Information Center Modernization                              R. L. Benedict                                           577
               R. L. Moe                                               532          Destruction of Offshore Platforms by Accelerated
               Networking and Ship-to-Shore Ship-to-Ship                            Galvanic Corrosion
               Communication                                                        C. A. Kohler                                             582
               S. C. Hall                                              537          -Corrosive-Wear of Buoy Chain
               The Defense Mapping Agency's Navigation                              J. Larsen-Basse, B. E. Liebert, K. M. Htun and
               Information Network                                                  A. Tadjvar                                               1628
                                                                                    Long-Term Abrasion and Corrosion Damage to the
               COLD REGIONS OPERATIONS                                              Hawaii Deep Water Power Cable

               Chairmen:                                                            M. Briere, K. C. Baldwin and M. R. Swift                 588
                 S. Smith                                                           Collision Tolerant Pile Structures: Design Analysis
                 U.S. Coast Guard                                                   Software
                 E. Early                                                           T. Dowd                                                  595
                 University of Washington                                           United States Naval Experience with Antifouling Paints
               J. D. Crowley                                           543
               Cold Weather Effects upon Marine Operations                          OCEAN ENGINEERING-II

               S. M. Smith and D. Strahl                               549          Chairmen:
               Articulated Lights in Ice                                              J. R. Vadus
                                                                                      Office of Oceanography and Marine Assessments,
               M. Gorveatt and M. C. Yee                               555               National Oceanic and Atmospheric Administration
               Arctic Ice Island Coring Facility                                      K. Okamura
                                                                                      Special Assistant to the Minister of Science and
               COLD REGIONS MEASUREMENTS                                                 Technology, Japan

               Chairmen:                                                            A. Bertaux                                               598
                 S. R. Osmer                                                        Tapered Interface in Harsh Environment Connectors
                 USCG International Ice Patrol
                 W. E. Hanson                                                       J. F. Legrand, A. Echardour, L. Floury, H. Floch, J.
                 USCG International Ice Patrol                                      Kerdoncuff, T. Le Moign, G. Loaec and Y. Raer            602
                                                                                    Nadia: Wireline Re-Entry in Deep Sea Boreholes
               W. E. Hanson                                            561          P. K. Sullivan and B. E. Liebert                         606
               Operational Iceberg Forecasting Concerns                             Impedance Measurements of Biofouling in Seawater
               G. Steeves and S. Grant                                 567          Condensers: An Update
               An Autonomous Atmospheric Pressure Recorder for                      E. A. Fisher and H. P. Hackett                           607
               Establishing Polar Sea Surface Height                                World's First Rigid Free-Standing Production Riser
               T. K. Newbury and A. J. Adams                           573          F. EI-Hawary                                             291
               Estimated Ice-Gouge Rates on a Manmade Shoal in the
               Beaufort Sea                                                         Compensation of Vertical Displacement Components
                                                                                    in Marine Seismic Applications Using the Coupled
                                                                                    Heave and Pitch Model

                                                                               Xii.

           INFORMATION SYSTEMS-I                                                   INFORMATION SYSTEMS-III

           Chairmen:                                                               Chairmen:
              J. A. Smith                                                             C. D. Kearse
              USCG R&D Center                                                         office of Marine Operations,
              G. Williams                                                               National Oceanic and Atmospheric Administration
              Texas A&M University                                                    D. White
                                                                                      General Instrument Corp.
           H. Bhargava and S. 0. Kimbrough                           1554
           Oona: An Intelligent Decision Support System for the                    G. Samuels                                                 648
           U.S. Coast Guard                                                        A Shipboard Data Acquisition, Logging and Display
                   %                                                               System
           T. F. Pfeiffer                                            612
           A Single Board Computer Based Sail Controller                           C. V. Baker and W. T. Whelan                               650
                                                                                   Offshore Oceanographic Applications for Battery-
           M. R. Nayak                                               615           Powered, High-End Microprocessors
           On the Knowledge-Based Expert System for Marine
           Instrumentation                                                         R. Findley                                                 655
                                                                                   CIDS-A Shipboard Centralized Integrated Data
           R. J. Smith                                               618           System
           OPDIN-One Way the Ocean Community Informs
                                                                                   M  'Reynolds, R. Hendershot, M. jungck and
           INFORMATION SYSTEMS-II                                                  B. Reid                                                   1560
                                                                                   The Zeno Alliance Network: A Dual-Loop Fiber Optic
           Chairman:                                                               Instrumentation Network for Ships
              P. Topoly
              Systems Planning NESDIS,                                             MOORING
                National Oceanic and Atmospheric Administration
                                                                                   Chairmen:
           D. Stamulis and M. P. Shevenell                           623              K. R. Bitting
           The Use of WORM Optical Disks in Ocean Systems                             USCG R&D Center
           W. B. Wilson                                              629              R. Swenson
           A Method for Optimizing Environmental Observing                            Neptune Ocean Engineering,
           Networks
                                                                                   J. D. Babb                                                 660
           W. C. Sutherland                                          632           Validation of Computer Model Predictions of the
           A User-Friendly Multi-Functional CTD Software                           L2rge-Sc2le Transient Dynamic Towing Response of
           Package                                                                 Flexible Cables
           D. Hamilton and J. Ward                                   637           H. 0. Berteaux, D. E. Frye, P. R. Clay and
           On-line Access to NODC Information Services                             E. C. Mellinger                                            670
                                                                                   Surface Telemetry Engineering Mooring (STEM)
           E. Voudouri and L. Kurz                                   641           D. R. May                                                  681
           Robust Sequential m-Interval Approximation Detectors                    New Technologies and Developments in NDBC Buoy
           with Q-Dependent Sampling                                               and Mooring Design

                                                                              xiii

              OPERATIONAL OCEANOGRAPHY                                           INTERNATIONAL COUNCIL FOR EXPLORATION OF THE SEA

              Chairman:                                                          Chairmen:
                S. R. Osmer                                                         J. B. Pearce
                USCG International Ice Patrol                                       ICES Marine Environment Quality Committee
              S. R. Osmer and D. L. Murphy                           687            J. N. Moore
              International Ice Patrol Applied Oceanography                         Center Ocean Law and Policy,
                                                                                      University of Virginia
              R. L. Tuxhorn                                          691         J. F. Pawlak                                           719
              Oceanography on EAGLE Australia '88 Cruise                         A Review of the Origins, Responsibilities, Composition
              J. A. McNitt                                           696         and Main Activities of the International Council for
              United States Navy Operational Oceanography:                       the Exploration of the Sea (ICES)
              Fighting Smart with Oceanography Intelligence                      S. A. Murawski                                         726
                                                                                 An Evaluation of Shellfish Research in the
              OCEANOGRAPHY-MEASUREMENTS AND ANALYSIS                             International Council for the Exploration of the Sea

              Chairman:                                                          J. B. Pearce                                           732
                W. D. Scherer                                                    The ICES Marine Environmental Quality Committee
                Office of Oceanography and Marine Assessments,                   (MEQC): Its History and Activities
                   National Oceanic and Atmospheric Administration
                                                                                 F. P. Thurberg                                         736
              P. Clemente-Cdlon and J. Zaitzeff                      1629        The ICES Working Group on Biological Effects of
              Upwelling Monitoring Off Western Sahara                            Contaminants: A Case Study
              K. Monkelien and T. L. Murrell                         699         SEWAGE SLUDGE DISPOSAL AND MONITORING
              Windrose, PC Software for Wind Data Analysis
              M. Enomoto, T. Kawanishi and W. Kato                   703         Chairmen:
              Measurement of Luminance Distribution on the Sea                      C. Dougherty
              Surface for Comfortable Living Space                                  Environmental Protection Agency
                                                                                    G. Lotzic
              UNDERWATER PHOTOGRAPHY                                                New York City Department of Environmental
                                                                                      Protection
              Chairman:                                                          J. C, Swanson and K. jayko                             740
                E. Kristof                                                       Modeling the Impacts of CSO Treatment Alternatives
                National Geographic Society                                      on Narragansett Bay
              E. Kristof, J. Stancampianc, and A. Chandler           709         H. M. Stanford and D. R. Young                         745
              Use of a Mac  Iro-Hybrid Camera at National Geographic             Pollutant Loadings to the New York Bight Apex
              E. Kristof, A. Chandler and W. Hamner                  713         S. E. McDowell, C. S. Albro, W. R. Trulli,
              3-D as an Underwater Too]                                          W. G. Steinhauer and F. G. Csulak                     1630
                                                                                 Optimum Techniques for Tracking Plumes in the
                                                                                 Ocean: A Case Study of Sludge Plume Dispersion at
                                                                                 the 106-Mile Site

                                                                                 C. E. Werme, P. D. Boehm, W. G. Steinhauer and
                                                                                 F. G. Csulak                                          1631
                                                                                 A Monitoring Plan for Disposal of Sewage Sludge at
                                                                                 the 106-Mile Site

                                                                                 C. D. Hunt, W. G. Steinhauer, C. E. Werme, P. D.
                                                                                 Boehm and F. G. Csulak                                1632
                                                                                 Monitoring Water Quality Characteristics During
                                                                                 Dispoasl of Sewage Sludge at the 106-Mile Site

                                                                          xiv.

           MARINE MINERAL RESOURCES                                            PROBLEMS IN OUR BAYS AND ESTUARIES

           Chairman:                                                           Chairman:
             B. Haynes                                                           V. K. Tipple
             Environmental Protection Agency                                     Estuarine Program Office,
                                                                                    National Oceanic and Atmospheric Administration
           R. J. Greenwald and H. F. Hennigar, Jr.                752
           Designation of an Ocean Mining Stable Reference Area                E. M. Burreson and J. D. Andrews                       799
                                                                               Unusual Intensification of Chesapeake Bay Oyster
           R. M. Mink. B. L. Bearden and E. A. Mancini            762          Diseases During Recent Drought Conditions
           Regional Geologic Framework of the Norphlet
           Formation of the Onshore and Offshore Mississippi,                  C. F. D'Elia and P. R. Taylor                          803
           Alabama, and Florida Area                                           Disturbances in Coral Reefs: Lessons from Diadema
                                                                               Mass Mortality and Coral Bleaching
           T. J. Rowland                                          768
           Availability of Minerals Offshore Virginia                          P. A. Tester, P. K. Fowler and R. P. Stumpf            808
                                                                               Red Tide, the First Occurrence in North Carolina
           C. E. McLain                                           777          Waters: An Overview
           Ocean Mining: An Opportunity for Public-Private
           Partnership                                                         B. L. Welsh                                            1633
                                                                               Hypoxia in Long Island Sound (LIS), Summer of 1987
           R. V. Amato                                            783
           Recent Nonenergy Mineral Activity in the Atlantic                   P. Molinari                                            1609
           Outer Continental Shelf                                             EPA's Response to the Flotables Incidents of the
                                                                               Summer of 1987

           TRASH ALONG THE COAST
                                                                               THE DOLPHIN DIE-OFF
           Chairman:
             L. Swanson                                                        Chairman:
             State University of New York                                        N. M. Foster
                                                                                 National Marine Fisheries Service
           J. B. Pearce                                           786
           Events of th6 Summer of '87                                         D. R. Cassidy, A. J. Davis. A. L. Jenny and
                                                                               D. A. Saari                                            812
           L. Schmidt                                             790          Pathology of the Diseased Dolphins
           Impacts and Implications of the Summer of 1987,
           New Jersey Flotable Incidents                                       J. Geraci                                              1634
                                                                               Epidemiology of Bottlenose Dolphin Disease-U.S.
           R. E, Dennis, R. P. Stumpf and M. C. Predoehl          1569         Atlantic Coast, 1987-1988
           Environmental Conditions in New York Bight, July-
           August, 1987                                                        J. G. Meade, C. W. Potter and W. A. McLellan           815
                                                                               Statistical Characteristics of the 1987 Bottlenose
           R. L. Swanson, R. Zimmer and C. A. Parker              794          Dolphin Die-Off in Virginia
           Meteorological Conditions Leading to the 1987
           Washup of Floatable Wastes on Newjersey Beaches                     W. Medway                                              818
           and Comparison of These Conditions with the                         Results of the Dolphin Epidemic Investigation as the
           Historical Record                                                   Disease was Presented in New Jersey Specimens of
                                                                               Bottlenose Dolphins in 1987

                                                                               G. P. Scott, D. M. Burn and L. J. Hansen               819
                                                                               The Dolphin Dieoff. Long-Term Effects and Recovery
                                                                               of the Population

                                                                          XV.

               SHIPWRECK ARCHEOLOGY                                                 OIL SPILL MOVEMENT

               Chairmen:                                                            Chairman:
                 W. C. Phoel                                                          D. F. Paskausky
                 NMFS, Sandy Hook Laboratory,                                         USCG R&D Center
                   National Oceanic and Atmospheric Administration
                 J. Bonclareff                                                      I. M. Lissauer                                         842
                 House Merchant Marine and Fisheries Committee                      A.Verifled Model for Oil Spill Movement, Beaufort
                                                                                    Sea, Alaska
               J. D. Broadwater                                        824          M. Reed and E. R. Gundlach                             847
               Historic Shipwrecks: Resources Worth Protecting                      Hindcast of the Amoco Cadiz Oil Spill
               A. G. Giesecke                                          827          E. J. Tennyson and H. Whittaker                        853
               The Abandoned Shipwreck Act: A Context                               The 1987 Newfoundland Oil Spill Experiment: An
               P. J. A. Waddell                                        833          Overview
               Reburial of a l6th Century Galleon                                   E. J. Tennyson                                         857
               J. D. Broadwater                                        837          Shipboard Navigational Radar as an Oil Spill Tracking
               Supporting Underwater Archaeology with Ocean                         Too]: A Preliminary Assessment
               Technology                                                           C. M. Anderson and R. P. LaBelle                       1673
               R. W. Lawrence                                          1627         Update of Occurrence Rates for Accidental Oil Spills
               Consequences of the Abandoned Shipwreck Act:          The            on the U.S. Outer Continental Shelf
               North Carolina Example
                                                                                    DRIFT MEASUREMENT
               J. Fullmer                                              1677
               Myth and Management-The Shipwreck Management                         Chairmen:
               Act                                                                    L M. Lissauer
                                                                                      USCG R&D Center
               ART                                                                    R. Q. Robe
                                                                                      USCG R&D Center
               Chairman:
                 H. B. Stewart, Jr.                                                 A. A. Allen and C. B. Billing                          860
                 Old Dominion University                                            Spatial Objective Analysis of Small Numbers of
                                                                                    Lagrangian Drifters
               C. Olsen                                                1576
               Art and Technology, on 20th-Century Vessels                          M. J. Lewandowski                                      865
                                                                                    A Minicomputer Application to Graphically Display
               H. B. Stewart, Jr.                                      840          Tidal Current Drift
               Artists on Oceanographic Expeditions: A Neglected
               Partnership                                                          E. A. Meindl                                           871
                                                                                    Drifting Buoy Data Quality and Performance
                                                                                    Assessment at the National Data Buoy Center

                                                                                    P. J. Hendricks                                        1635
                                                                                    Drift Current Measurements from a Submarine

                                                                           Xvi.

           ECONOMICS OF MARINE OPERATIONS                                        ENVIRONMENTAL POLICY

           Chairmen:                                                             Chairmen:
             F. Olson                                                               S. Bolton
             Environmental Consultant                                               Office of Legislative Affairs,
             D. M. King                                                               National Oceanic and Atmospheric Administration
             ICF Inc.                                                               R. Dye
                                                                                    House Merchant Marine and Fisheries Committee
           M. D. Aspinwall                                           876
           Commercial Vessel Operations in the Exclusive                         R. W. Zeller                                              905
           Economic Zone: Will the Jones Act Keep Up?                            Resolving the Environmental Decisionmaking and
                                                                                 Research Dilemma
           M. W. Clark, Jr., D. P. Robinson and L. G. Antle          1690
           Economic Impacts from Coal Exports: Through the                       C. A. Crampton and R. C. Helland                          910
           Port of Baltimore and the Port of Norfolk                             A Strategy for Program Implementation

           C. D. MacDonald and H. E. Deese                           880         J. N. Leonard                                             914
           Opportunities for DevelopInent: A Growth Scenario                     Updating the Stratton Commission: A Proposal for the
           and Situation Analysis of Hawaii's Ocean Industries                   U.S. Coast Guard Ocean Survey Corps

           D. L. Soden, J. D. Reighard and W. H. Hester              891         H. E. Schultz                                             920
           Outside Influence on Port Operations: The Insider's                   National Response Mechanism
           Perspectives
                                                                                 J. S. Hawkins                                             925
           M. G. Johnson                                             896         Satellite Ocean Monitoring at Ten Years: Perceptions
           Use of Systems Analysis Techniques in Ocean                           and Realities
           Resources Development
                                                                                 P. Stang and E. Turner                                    1616
           EDUCATION AND TRAINING                                                Legal and Policy Issues at Stake in the Current 5-Year
                                                                                 Program
           Chairmen:
             Richard Asaro, USCG                                                 ESTUARINE STUDIES-1
             Office of Marine Safety, Security and
               Environmental Protection                                          Chairman:
             Thbyer Shafer                                                          D. J. Basta
                                                                                    Office of Oceanography and Marine Assessments,
           J. Morton                                                 899              National Oceanic and Atmospheric Administration
           Marine Field Projects: Teaching is the Easy Part                      S. E. McCoy                                               930
           S. Teel                                                   1582        Monitoring the Estuary
           Maritime Training and Ocean Education                                 1. C. Sheifer                                             937
           H. F. Trutneff                                            9.02        Climate, Weather, and Coastal Recreational Growth in
           The Impact of Marine Technology on Education and                      the Southeast U.S. in 1986
           Training in Marine Transportation
                                                                                 A. Stoddard                                               942
                                                                                 An Innovative Approach for the Synthesis of Large
                                                                                 Oceanographic Data Sets with Pre-Processing and
                                                                                 Post-Processing of an Ecosystem Model of the New
                                                                                 York Bight

                                                                                 J. Gerritsen                                              948
                                                                                 Biological Control of Water Quality in Estuaries:
                                                                                 Removal of Particulate Matter by Filter Feeders

                                                                             xvii.

              ESTUARINE STUDIES-H                                                  OCEAN POLICY-A MATRIX OF FEDERAL, STATE AND
                                                                                   INTERNATIONAL ISSUES
              Chairmen:
                S. E. McCoy                                                        Chairmen:
                Estuarine Program Office,                                             E. W. Cannon
                   National Oceanic and Atmospheric Administration                    USCG Governmental Affairs Staff
                D. Ashe                                                               K. U. Wolniakowski
                House Merchant Marine and Fisheries Committee                         State of Oregon

              Oral only                                                            E. W. Cannon                                             1717
                                                                                   The USCG: A Prototype for National and International
              FISHERIES AND RESOURCE ASSESSMENTS                                   Ocean Policy Implementation
              Chairman:                                                            L. A. Berney
                R. Smolowitz                                                       The Unspoken Yet Vital Partnership Between the
                National Marine Fisheries,                                         USCG Reserve and the Civilian Community at Large
                   National Oceanic and Atmospheric Administration                 C. R. Corbett                                            992
              F. L. Ames                                              961          International Oil Spill Liability and Compensation
              Improved U.S. Strategy for Fisheries Law Enforcement                 E. Hout, R. Bailey and K. U. Wolniakowski                994
              G. Reetz                                                966          Ocean Resource Management in Oregon: Pushing
              California Sea Otter: Impact Assessment and Mitigation               Open the Window of Opportunity
              D. Luo                                                  972          J. S. S. Lakshminarayana                                 1000
              Theoretical Analysis of Fish School Density                          Overview and Analysis of Coastal Zone Management
                                                                                   in the Atlantic Provinces, Canada
              R. J. Smolowitz and F. M. Serchuk                       975          D. C. Slade                                              1006
              Marine Fisheries Technology in the United States:                    Coastal States and Marine Resource Development
              Status, Trends and Future Directions                                 Within the United States Exclusive Economic Zone

              B. F. Beal                                              980
              Public Aquaculture in Downeast Maine: The Soft-She]]                 OCEAN DRILLING PROGRAM
              Clam Story
                                                                                   Chairman:
              P. H. Averill                                           1637            J. H. Clotworthy
              Development of Separator Trawl Technology                               Consultant
              FISHERIES-IMPACT STUDIES                                             P. Brown, K. Lighty, R. Met    Irill and
                                                                                   P. D. Rabinowitz                                         1012
              Chairman:                                                            Collection and Quality Control of Marine Geological
                J. Chambers                                                        Data by the Ocean Drilling Program
                National Marine Fisheries Service                                  D. Graham, B. Hamlin, B. julson, W. Mills, A. Meyer,
              H. A. Carr                                              984          R. Olivas, P. D. Rabinowitz, D. Bontempo and
              Long Term Assessment of a Derelict Gillnet Found in                  J. Tauxe                                                 1018
              the Gulf of Maine                                                    Shipboard Laboratory Support: Ocean Drilling             -
                                                                                   Program
              A. E. Pinkney, L. L. Matteson and D. A. Wright          987          P. Weiss, G. Bode, C. Mato, R. Merrill, P. D.
              Effects of Tributyltin on Survival, Growth,                          Rabinowitz, M. Angell, J. Miller, P. Myre, S. Prinz,
              Morphometry and RNA-DNA Ratio of Larval Striped                      D. Quoidbach and R. Wilcox                               1025
              Bass, Morone saxatilis                                               Core Curation: Ocean Drilling Program

                                                                              xviii.

           OCEAN ENERGY-I                                                    MARINE MAMMALS RESEARCH AND MANAGEMENT

           Chairman:                                                         Chairman:
             D. Cotter                                                         D. Swanson
             CBI Industries                                                    National Marine Fisheries Service,
                                                                                 National Oceanic and Atmospheric Administration
           P. Vauthier                                         1029
           The Underwater Electric Kite: East River Deployment               H.. H. Armstrong and K. R. Banks                     1073
                                                                             Modern Eskimo Whaling in the Alaskan Arctic
           D. E. Lermard and F. A. Johnson                     1034
           British OTEC Programmes-I OMW Floating and                        G. H. Allen                                          1079
           0.5MW Land Based                                                  Observations on the 1987 Subsistence Harvest of
                                                                             Northern Fur Seals on St. Paul Island, Pribilof Islands,
           R. K. Jensen                                        1039          Alaska
           Hydro Power from the Ocean
                                                                             R. T. Bennett                                        1083
           A. Thomas and D. Hillis                             1045          Endangered Species and Marine Mammal Protection
           First Production of Potable Water by OTEC and Its                 During Offshore Structure Removals in the Gulf of
           Potential Applications                                            Mexico

           OCEAN ENERGY-H                                                    SHIP DESIGN AND REPAIR

           Chairman:                                                         Chairmen:
             L. Lewis                                                          M. S. Canavan
             Department of Energy                                              USCG Office of Engineering and Development
                                                                               T. Colton
           D. C. Hicks, C. M. Pleass and G. R. Mitcheson       1049            Colton Company
           DELBUOY. Wave-Powered Seawater Des2lination
           System                                                            M. S. Canavan and M. D. Noll                         1087
           K. P. Melvin                                        1055          U.S. Coast Guard's New Polar Icebreaker Design
           A Wave Energy Engine and Proposals for its                        D. W. Yu and J. H. Devletian                         1098
           Development and Usage                                             Electroslag Surfacing for Construction, Restoration,
           L. Claeson                                          1638          and Repair of Ship Structures
           Recent Wave Energy Research in Sweden                             RESEARCH VESSELS
           K. Kudo, T. Tsuzuku, K. Imai and Y. Akiyama         1061          Chairman:
           Wave Focusing by a Submerged Plate                                  W. Barbee
           Y. Masuda, M. E. McCormick, T. Yamazaki and                         University-National Oceanographic Laboratory
           Y. Outa                                             1067              System
           The Backward Bent Duct Buoy-An Improved                           J. A. Chance                                         1107
           Floating Type Wave Power Device                                   Conversion of Surplus Ofifield Supply Vessels to
                                                                             Research Vessels

                                                                             C. Hamlin                                            1111
                                                                             Research Vessels: A Systems Engineering Approach

                                                                             B. L. Hutchison and S. Jagannathan                   1117
                                                                             Monohull Research Vessel Seakeeping and Criteria

                                                                             R. J. Wilber, C. E. Lea and S. E. Humphris           1639
                                                                             The SSV Corwith Cramer: Sea Education Association's
                                                                             New Sailing Research Vessel

                                                                     xix@

             SALVAGE AND TOWING                                                 SWATH SHIPS-I

             Chairman:                                                          Chairman:
               J. H. Boyd                                                         R. Dinsmore
               Booz, Allen & Hamilton, Inc.                                       Woods Hole Oceanographic Institution

             J. K. Edgar                                          1640          G. R. Lamb                                           1131
             Hazardous Materials in Marine Salvage Operations                   Relationship Between Seakeeping Requirements and
                                                                                SWATH Ship Geometry
             C. M. Kalro                                          1603
             Launch and Retrieval of a 1,000 Ton Barge Shaped                   M. Rice, E. Craig, S. Drummond and
             Vessel from a Conventional Tanker                                  C. junemann                                          1144
                                                                                Conceptual Design of an Intermediate Size
             J. Strandquist                                       1124          Oceanographic Research Ship for the University-
             Removal of the Wreck of the Ex-USS TORTUGA                         National Oceanographic Laboratory System
             THE SMALL PASSENGER VESSEL INDUSTRY-1                              R. D. Gaul, A. C. McClure and F. E. Shumaker         1149
                                                                                Design of a Semisubmerged SWATH Research and
             Chairmen:                                                          Survey Ship
               E. G, Sharf                                                      C. Kennell                                           1157
               National Association of Passenger Vessels                        Tankage Arrangement for SWATH Ships
               H. Parker
               National Association of Passenger Vessels                        SWATH SHIPS-II
             W. B. Hamner                                         1641          Chairman:
             The Future of the Tourist Submarine Industry                         K. W. Kaulum
             Oral only                                                            Office of Naval Research
                                                                                T. G. Lang, C. B. Bishop and W. J. Sturgeon          1163
             THE SMALL PASSENGER VESSEL INDUSTRY-H                              SWATH Ship Designs for Oceanographic Research

             Chairman:                                                          E. Craig and S. E. Drummond                          1169
               E. G. Scharf                                                     SWATH CHARWIN-Range Support Ship
               National Association of Passenger Vessels
                                                                                A. Galerne                                           1573
             T. MacRae                                            1125          Development of Deep Water Technology as It Relates
             The Realities of Bareboat Chartering                               to Future Salvage

             Oral only                                                          E. Craig
                                                                                Real World Experience with SWATH Design

                                                                           XX.

            SHIPBOARD TECHNICAL SUPPORT                                       AN INTERIM STATUS REPORT ON     ORGANOTINS-II

            Chairman:                                                         Chairmen:
              H. L. Clark                                                       P. F. Seligman
              National Science Foundation                                       Naval Ocean Systems Center
            H. L. Clark                                          1644           M. A. Champ
            Shipboard Technician Program     of the National Science            National Science Foundation
            Foundation                                                        K. W. M. Siu                                         1716
            J. D. Guffy, M. A. Spears and D. C. Biggs            1173         Analytical Chemistry of Butyltins
            Automated Analyses of Nutrients in Seawater with     the          T. L. Wade, B. Garcia-Romero and J. M. Brooks 1198
            Technicon TrAAcs-800 A utoanalyzer System                         Tributyltin Analyses in Association with NOAA's
                                                                              National Status and Trends Mussel Watch Program
            D. J. Murphy, E. Wilson and E. Powell                1178
            An Application of a Low Flow Current Meter to Broad               C. M. Adema, W. M. Thomas, Jr., and
            Temperature Range Estuarine Current Measurements                  S. R. Mangum                                         1656
            M. Maccio and C. Langdon                             1181         Butyltin Releases to Harbor Water from Ship Painting
            Description of Conversion of an EG&G VMCM into a                  in a Dry Dock
            MVMS (Multi-Variable Moored Sensor)                               B. Cool
                                                                              Summary and Status Report of EPA's Special Review
            AN INTERIM STATUS REPORT ON ORGANOTINS-1                          (PD14)

            Chairmen:                                                         WAVE MOTION
              P. F. Seligman
              Naval Ocean Systems Center                                      Chairman:
              M. A. Champ                                                       R. H. Canada
              National Science Foundation                                       National Data Buoy Center,
                                                                                   National Oceanic and Atmospheric Administration
            P. F. Seligman, J. G. Grouhoug and C. M. Adema
            Field Monitoring of TBT Concentrations in Pearl                   L. J, Ladner, W. B. Wilson and P. J. Kies            1202
            Harbor Correlated with Model Simulation Studies                   Lake Superior Winter Weather Station

            R. S. Henderson                                      1645         N. Lang
            Chronic Exposure Effects of Tributyltin on Pearl                  The Linear Properties of Spectra from a PitchlRoll
            Harbor Organisms                                                  Buoy

            M. H. Salazar and S. M. Salazar                      1188         E. D. Michelena and R. Dagnall
            Tributyltin and Mussel Growth in San Diego Bay                    A Computer Controlled Signal Simulator for Buoy
                                                                              Motion Sensors
            M. H. Salazar and M. A. Champ                        1497
            Tributyltin and Water Quality: A Question of                      D. Smith and F. Remond
            EnvironmentQ] Significance                                        3-Meter Directional PitchlRoll Buoy

            W. R. Blair, G. J. Olson, T. K. Trout, K. L. Jewett
            and F. E. Brinckman                                  166.1;
            Accumulation and Fate of Tributyltin Species in
            Microbial Biofilms

                                                                         Xxi.

              WAVE MEASUREMENTS                                                 UNDERWATER VEHICLES

              Chairman:                                                         Chairman:
                L. Baer                                                            R. Blidberg
                Office of Oceanography and Marine Assessments,                     University of New Hampshire
                  National Oceanic and Atmospheric Administration
                                                                                M. Higgins and R. Whyte                              1646
              H. Brown                                             1205         Controlled Depressor Towed Sensor Platform-The
              Infrared Loser Wave Height Sensor                                 U.S. Navy's Mk28 Search System

              G. Kontopidis and G. Bowers                          1207         M. Higgins, B. Lawson and B. Field                   1647
              WavePro: An Autonomous Wave Processor with Long-                  Development and Testing of a Heavy-Duty Work ROV
              Range Telemetry                                                   for 10,000 Foot Service

              F. Ziemer, H. Giinther and E. Stockdreher            1212         H. Momma, K. Ohtsuka and H. Hotta                    1253
              Measured Transfer Functions for Shipmotions in                    JAMSTECIDeep Tow System
              Natural Seaways
                                                                                J. jalbert, M. Shevenell, S. Chappel, R. Welsh and
              D. W. Farrell                                        1587         R. Blidberg                                          1259
              The Next Generation Water Level Measurement                       EAVE III Untethered AUV Submersible
              System: The Next Step in Real-Time Data for
              Navigation                                                        M. E. Cooke, S. Gittings, J. M. Brooks and
                                                                                D. C. Biggs
              WAVE ACTION ON SEA SHORES                                         Texas A&M University Remotely Operated
                                                                                Oceanographic Vehicle (TAMU-ROOV)
              Chairman:
                M. Earle                                                        UNDERWATER VEHICLE SYSTEMS AND EQUIPMENT
                MEC Systems Corp.
                                                                                Chairmen:
              M. J. Briggs and P. J. Grace                         1218            S. B. Cable
              Influence of Frequency and Directional Spreading on                  Naval Civil Engineering Laboratory
              Wave Transformation in the Nearshore Region                          R. Wernh
              D. D. McGehee and J. P. McKinney                     1224            Naval Ocean Systems Center
              Tidal Circulation Data from the Los AngeleslLong                  F. Dougherty, T. Sherman, G. Woolweaver and
              Beach Harbors                                                     G. Lovell                                            1265
              S. L. Da Costa and J. L. Scott                       1231         An Autonomous Underwater Vehicle (AUV) Flight
              Wave Impact Forces on the Jones Island East Dock,                 Control System Using Sliding Mode Control
              Milwaukee, Wisconsin                                              M, L. Nuckols, J. Kreider and W. Feild               1271
              J.Rosati III and G. L. Howell                        1239         Thermal Modelling of Electro-Mechanical Cables for
              A Hierarchical Multiprocessor Data Acquisition System             ROV Applications
              for Field Measurement of Structural Response in                   M. P. Shevenell and C. Millett                       1276
              Breakwater Concrete Armor Units                                   A LISP Environment for Real-Time Ocean Systems
              J. P. Ahrens and E. T. Fulford                       1244         S. B. Cable                                          1280
              Wave Energy Dissipation by Reef Breakwaters                       A Guideline System for the Navy's Submarine Rescue
              E. H. Harlow                                         1250         Ship (ASR) Class
              Why Breakwaters Break                                             W. J. Herr                                           1290
                                                                                AUV Technology: Development and Demonstration
                                                                                Program

                                                                            Xxii.

           MANNED SUBMERSIBLES                                               HAZARDOUS CHEMICAL IDENTIFICATION AND MANAGEMENT

           Chairman:                                                         Chairmen:
              R. W. Cook                                                       L. H. Gibson
              Harbor Branch Oceanographic Institute                            USCG Central Oil Identification Laboratory
           Oral only                                                           E. F. Batutis
                                                                               Phasesep Corp.

           DIVING OPERATIONS AND SYSTEMS                                     W. R. Cunningham                                    1321
                                                                             NOAA Fleet Hazardous Materials and Hazardous Waste
           Chairmen:                                                         Management
              W. C. Phoel
              National Marine Fisheries Service,                             L. H. Gibson and M. S. Hendrick                     1326
                National Oceanic and Atmospheric Administration              U.S. Coast Guard Oil Identification System
              J. M. Wells                                                    T. J. Haas, J.. J. Kichner and T. J. Chuba          1332
              Office of Marine Operations,                                   Course in Hazardous Materials
                National Oceanic and Atmospheric Administration

           J. K. Jeffries                                                    BUOY-BASED METEOROLOGY
           Standards and Procedures for Dry Suit Diving
           Education                                                         Chairman:
                                                                               R. Canada
           J. K. Jeffries                                                      National Buoy Center
           Thermal Guidelines for Diving Operations
                                                                             S. P. Burke and D. G. Martinson                     1335
           R. 1. Wicklund                                      1614          An ARGOS Meteorological Oceanographic Spir Buoy
           An Inexpensive Mobile Self-Contained Habitat System               for Antarctic Deployments
           for Marine Research
                                                                             D. B. Gilhousen                                     1341
           J. W. Blackwell and C. D. Newell                    1300          Methods of Obtaining Weather Data in Real Time
           Diving in Hazardous and Polluted Waters
                                                                             E. D. Michelena                                     1649
           J. M. Wells                                         1305          The Measurement of Precipitation at National Data
           The Use of Nitrogen-Oxygen Mixtures as Diver's                    Buoy Center Stations
           Breathing Gas
                                                                             R. R. Miller and R. Canada                          1650
           J. P. Fish and H. A. Carr                           1309          Mini-Drifter Test Deployment Data-Gulf of Mexico
           Integrated Remote Sensing of Dive Sites                           Spring 1988

           S. L. Merry, S. L. Sendlein and A. P. jenkin        1315          P. M. Friday, J. S. Lynch and F. S. Long            1344
           Human Power Generation in an Underwater                           Interactive Marine Analysis and Forecast System
           Environment                                                       (IMAFS): The Oceanographic Workstation of the
                                                                             Future

                                                                             D. A. Storey and W. E. Woodward                     1348
                                                                             The Global Ocean Platform Inventory

                                                                             VESSELS OF THE 80s AND BEYOND

                                                                             Chairmen:
                                                                               E. K. Pentimonti
                                                                               American President Lines, Ltd.

                                                                               P. Mentz
                                                                               Advanced Ship Operations, MARAD

                                                                             Oral only

                                                                         Xxiii.

              FACILITIES IN SUPPORT OF MARINE FREIGHT                            NAVIGATION CHARTING
              TRANSPORTATION
                                                                                 Chairmen:
              Chairmen:                                                             R. Vorthman
                 M. J. Vickerman, Jr.                                               USCG Operations Control Center, Atlantic Area
                 Vickerman, Zachary, Miller                                         M. Kumar
                 R. Katims                                                          Defense Mapping Agency
                 Container Transport Technology
                                                                                 W. M. Maynard                                         1371
              Oral only                                                          Cooperative Electronic Chart Development: The
                                                                                 GAADS Project
              NAVIGATION SYSTEMS AND OPERATIONS                                  P. W. Mushkat and C. Lamson                           1589
              Chairmen:                                                          Electronic Chart Display Information Systems:
                 G. R. Perreault                                                 Operational, Policy and Legal Issues
                 Office of Navigation,                                           N. D. Smith                                           1374
                   U.S. Coast Guard                                              Automated Nautical Data and Charting Development
                 J. Illgen
                                                                                 E. A. Soluri
              A. F. E. Fuentes                                      1651         Defense Mapping Agency's Navigational Information
              A Survey of Radionavigation System Users                           System
              L. Mehrkam                                            1352         NAVIGATION SYSTEMS
              Leading Lines for the Nineties
              G. R. Perreault                                       1356         Chairmen:
              Contract Service of Federal Aids to Navigation                        C. D. Kearse
                                                                                    Office of Marine Operations,
              R. J. Weaver and R. M. Piccioni.                      1362              National Oceanic and Atmospheric Administration
              Marine Radionavigation of the Future                                  P. Stutes
                                                                                    John E. Chance & Assoc. Inc.
              L. V. Grant                                           1365
              Federal Radionavigation Plan Overview                              J. L. Hammer III and W. R. Hoyle                      1379
                                                                                 The Continuing Need for Accurate Positioning in
              J: Hammer III and W. R. Hoyle                         1684         Naval Tactics
              The Continuing Need for Accurate Positioning in
              Naval Tactics                                                      E. F. Carter and J. Lewkowicz                         1594
                                                                                 A Computer Navigation System Using Kalmaro Filter
                                                                                 Smoothing

                                                                                 R. Gandy and S. Paulet                                1648
                                                                                 Design and Applications of SEATRAC, an Integrated
                                                                                 Navigation and Data Management System

                                                                                 D. C. Slade
                                                                                 Solar Navigation

                                                                                 A. E. Shaw III and T. E. Bryan                        1384
                                                                                 Oceanographic Applications of the ARGOS System

                                                                             xxiv.

            AIDS TO NAVIGATION SYSTEMS AND EQUIPMENT                              SEARCH AND RESCUE-SURVEILLANCE EXPERIMENTS

            Chairman:                                                             Chairman:
               T. S. Winslow                                                         W. H. Reynolds
               Office of Engineering,                                                USCG R&D Center
                 U.S. Coast Guard
                                                                                  D. Finlayson, D. Bryant, B. R. Dawe and
            T. S. Winslow, M. D. Dawe, K. R. Schroeder and                        A. J. Armstrong                                         1417
            W. A. Fisher                                            1390          Results of an Experiment to Examine Certain Human
            High-Voltage Solar-Powered Navigation Range Design                    Factors Relating to Searches Conducted with Marine
                                                                                  Radar
            J. McCaffrey
            An Alternative Hull Design for the U.S. Coast Guard                   D. Bryant, B. R. Dawe, D. Finlayson, W. Reynolds
            Bell Buoy                                                             and M. J. Lewandowski                                   1422
                                                                                  Results of Canadian Shipbome Night Search
            GLOBAL POSITIONING SYSTEM                                             Experiments
            Chairmen:                                                             B. R. Dawe, D. Finlayson and D. Bryant                  1427
               K. Nakamura                                                        Results of a Canadian Shipbome Radar Search and
               Office of the  Assistant Secretary of Defense                      Rescue Detection Experiment
               R. S. Warren                                                       D. Finlayson, B. R. Dawe and D. Bryant                  1433
               TASC                                                               Results of a Canadian Visual Search and Rescue
                                                                                  Detection Experiment
            L. D. Hottram
            Relative GPS Kinemetric Surveying and Applications                    F. Replogle, Jr.                                        1436
            for Marine Positioning                                                A New Coast Guard Search Technique
            M. J. Mes                                               1395          SEARCH OPERATIONS
            Accuracy of Satellite Survey Measurements on
            Offshore Platforms for Monitoring Subsidence                          Chairmen:
            E. M. Geyer and R. S. Warren                                             R. Q, Robe
                                                                                     USCG R&D Center
            Mission Planning Issues and Answers for GPS Users
                                                                                     B. Dawe
            SHIP OPERATIONS AND SCHEDULING                                           Nordco Ltd.
            Chairman:                                                             R. W. Berwin                                            1439
               C. Pritchett                                                       Alaska SAR Facility Archive and Operations System
               USCG R&D Center                                                    M. K. Kutzleb                                           1444
            S. Cook, R. Benway, W. Krug, M. Nestlebush. A.                        The Search for South African Airways Flight 295
            Picciolo, W. Richardson, P. Stevens and                               D. R. Paskausky, W. Reynolds, R. Gaines and
            V. Zegowitz                                             1400          R. Q. Robe                                              1605
            Volunteer Observing Ships and the U.S.                                Improving Search Success; Real-Time Collection and
            Government-A Winning Partnership                                      Transfer to User
            L. C. Kingsley, K. S. Klesczewski, J. A. Smith and                    R. Q. Robe, D. F. Paskausky and G. L. Hover             1448
            R. A. Walters                                           1405          Performance of Coast Guard Medium Range
            Comparing the U.S. Coast Guard Buoy Tender                            Surveillance (MRS) Aircraft Radars in Search and
            Performance Using Simulation                                          Rescue (SAR) Missions
            K. S. Klesczewski                                       1411          J. B. Brewster                                          1454
            Using Spacefilling Curve to Generate the Feasible                     Sea Based Aerostats (SBA): Effective *Surveillance for
            Routes for the Set Partitioning Problem                               Maritime Interdiction
            S. F. Roehrig                                           1643
            Scheduling Patrols Using a Hybrid Iriteger
            Programmingl Rule-Based System Approach

                                                                             -xXv.

              PORT MANAGEMENT AND SECURITY

              Chairmen:
                T. Robinson
                Port Safety and Security Division,
                   U.S. Coast Guard

                D. Smith
                House Merchant Marine and Fisheries Committee

              D. J. Evans, R. W. Owen and P. R. Farragut            1457
              Innov3tive Technology Applied to Maximize a Port's
              Lifeline: A Case History for the Sea Lanes of the
              Chesapeake Bay

              N. A. Marziani                                        1463
              The Multi-Agency MOU on Port Security: A Model for
              Conflict Resolution

              D. J. Sheehy and S. F. Vik                            1470
              Mitigation Planning for Port Development

              J. J. Zagel, R. T. Kilgore and S. M. Stein            1642
              Hydrodynamic and Mass Transport Modeling of Navy
              Harbors

              MARINE SAFETY

              Chairmen:
                C. L. Hervey
                USCG R&D Center

                S. Steele
                House Merchant Marine and Fisheries Committee

              F. H. Anderson                                        1598
              Awakening the Consciousness of the Boating Public
              Regarding Pollution, Intoxication, and Common Sense
              Safety of the Nation's Waterways

              A. Colihan                                            1476
              Coast Guard Recreational Boating Product Assurance
              Program

              C. L. Hervey                                          1482
              Determining Horsepower Limits on Recreational Boats

              S. Johnson and J. Veentjer                            1487
              Regulation of Passenger Carrying Submersibles

              G. L. Traub                                           1493
              Recreational Boating Accidents in Ocean Waters

                Manuscript unavailable for publication

                                                                                  Xxvi.

                                                               Authors List

           Abrams, W. R       ...............  344        Boehm, P. D       ......... 1631, 1632         Clark, M. W., jr  ............      1688
           Adams, A. j        ................. 573       Boerner, W.-M     ..............    454        Clark, R. B       ................. 184
           Adema, C. M        ...............  1656       Boggess, R. L     ...............   423        Clay, P. R        .................. 670
           Aharon, P          .................. 101      Bonetempo, D      .............    1018        Clemente-Colon, P     ..........    1629
           Ahrens, J. P       ................ 1244       Bostater, C       ................. 462        Clifford, S. F    ................  315
           Akiyama, Y         ................ 1061       Bowen, A. j       ............ 413, 419        Cloet, R. L       .................. 1636
           Albro, C. S        ................ 1630       Bowers, G         ................ 1207        Coe, J. M         ..................... I
           Allen, A. A        ................. 86o       Boyer, L. F       ............. 443, 448       Colbourne, E. B   .............     413
           Allen, G. H        ................ 1079       Brashier, j       .................. 136       Colihan, A        ................  1476
           Alonzo, C          ................. 1612      Breeding, S. K    ...............   391        Colwell, R. R     ..............    16o6
           Amato, R. V        ................ 783        Brewster, J. B    ..............   1454        Cook, S           ................... 1400
           Ames, F. L         .................. 961      Brickey, M. R     ..............   1611        Cooper, R. A      ................  112
           Anderson, C. M     ............     1673       Briere, M         ................... 588      Corbett, C. R     ...............   992
           Anderson, F. H     .............    1598       Briggs, M. j      ................ 1218        Corwin, R         .................. 397
           Andrews, J. D      ...............  799        Bright, T. j      .................. 22        Cottingham, D     ................      6
           Angell, M          ................. 1025      Brinckman, F. E   ............     1668        Craig, E          ............. 1144, 1169
           Antle, L. G        ................ 1688       Broadwater, J. D  ........    824, 837         Crampton, C. A    .............     910
           Appell, G. F       ................ 346        Brooks, J. M      ...............  1198        Crawford, G. B    ..............    315
           Armstrong, A. j    .............    1417       Brown, H          ................. 1205       Crowley, J. D     ...............   543
           Armstrong, H. H    ............     1073       Brown, P          ................. 1012       Csulak, F. G      .....  1630,1631,1632
           Ashmore, S         ................. 259       Browning, D. G    .............     318        Cuddy, D. T       ................  473
           Aspinwall, M. K    .............    876        Bryan, T. E       ................ 1384        Cunningham, W. R      ..........    1321
           Asplin, R. G       ................ 329        Bryant, D         ........ 485, 1417, 1422,    Curlander, j      ................  479
           Augerot, X         ................ 1711                                   1427,1433          Da Costa, S. L    ...............   1231
           Aurand, D. V       ...............  161        Buddenberg, R. A    ............    526        Dardeau, M. R     ................    17
           Auster, P. j       ...........  1286, 161o     Bunn, A. R        ...................  I       Davis, A. j       .................. 812
           Averill, P. H      ...............  1637       Burden, D. G      ................   70        Dawe, B. R        ........... 1417, 1422,
           Babb, 1. G         .................. 112      Burke, S. P       ................ 1335                                   1427,1433
           Babb, J. D         .................. 660      Burn, D. M        ................. 819        Dawe, M. D        ...............   1390
           Babb, L. V         .................. 423      Burreson, E. M    ..............    799        Dean, J. M        ................... 35
           Bailey, R          ................... 994     Burroughs, R. H   ............     1607        Deese, H. E       ................. 880
           Baker, C. V        ................. 650       Cable, S. B       ................ 1280        D'Elia, C. F      ..............  29,803
           Baldwin, K. C      ...............  588        Caldwell, P. j    ................   46        de Moustier, C    ..........   372,509
           Banks, K. R        ................ 1073       Campbell, W. B    ............     1626        Dennis, R. E      ...............   1569
           Bascle, B. j       ................. 223       Canada, R         ................. 1650       Devletian, J. H   .............     1098
           Bass, P. D         .................. 346      Canavan, M. S     ..............   1087        DeVoe, M. R       .................   35
           Batt, B. D. j      .................   46      Cannon, E. W      ..............   1717        Diaz, R. j        ................... 448
           Beal, B. F         ................... 980     Carney, R. S      .............. 90,96         Dindo, J. j       ................... 17
           Bearden, B. L      ...............  762        Carr, H. A        ............. 984,1309       Dougherty, F      ..............    1265
           Benada, J. R       ................ 473        Carter, E. F      ................ 1594        Dowd, T           ................... 595
           Benedict, R. L     ...............  577        Cassidy, D. R     ...............   812        Drummond, S       ........ 1144,1169
           Bennett, R. T      ..............   1083       Chalmers, A. G    .............    1605        Dunaway, M. E     ..............    268
           Benway, R          ................ 1400       Champ, M. A       ..............   1497        Dunkel, C. A      ................  208
           Berney, A          ................. 1725      Chance, J. A      ...............  1107        Echardour, A      ...............   602
           Bertaux, A         .................. 598      Chandler, A       ........ 335, 709, 713       Edgar, J. K       ................  164o
           Berteaux, H. 0     ..............   670        Chaplin, G        ................. 275        Edson, G. M       ................  219
           Berwin, R. W       ..............   1439       Chappel, S        ................ 1259        EI-Hawary, F      ................  291
           Bhargava, H        ...............  1554       Charters, J. S    ........... 385,509          Eller, A. I       .................. 295
           Biggs, D. C        ................ 1173       Chauvin, A. L     ..............   1536        Enomoto, M        ................  703
           Billing, C. B      ................ 86o        Chico, T          ................... 166      Essig, R. j       .................. 127
           Bimbo, A. P        ...............  1513       Christensen, C. G   ............    329        Evans, D. j       ............. - . 1457
           Bishop, C. B       ...............  1163       Christensen, D    .............    1624        Farragut, P. R    ..............    1457
           Bitterman, D       ..........  ..... 359       Chuba, T. j       ................ 1332        Farrell, D. W     ...............   1587
           Blackwell, J. W    .............    1300       Cibik, S. j       ................... 29       Fedor, L. S       ........... 1697,1704
           Blair, W. R        ................ 1668       Claeson, L        ................. 1638       Feild, W          .................. 1271
           Blidberg, R        ................ 1259       Clark, B. R       ................. 143        Field, B          ................... 1647
           Bode, G            .................. 1025     Clark, H. L       ................ 1644        Findley, R        .................. 655

                                                                            xxvii.

                Finlayson, D        .......... 1417, 1422,         Hazen, D. G         .................  419         Kerdoncuff,J       ...............     602
                                              1427,1433            Heck, K. L., Jr     ...............      17        Kichner, J. J      ...............     1332
                Fish, J. P          .................. 1309        Hedrick, J. D       ...............    448         Kies, P. J         ..................  1202
                Fisher, E. A        .................   607        Helland, R. C       ...............    910         Kilgore, R. T      ...............     1642
                Fisher, W. A        ...............   1390         Hendershot, R       .............      1560.       Kimbrough, S. 0      ...........       1554
                Fleischer, P        ..................    17       Henderson, R. S     ............       1645        King, P. C         .................   1618
                Flick, G. J., Jr    ................      56       Hendrick, M. S      .............      1326        Kingsley, L. C     ...............     1405
                Floch, H            ................... 602        Hendricks, P. J     .............      1635        Klemas, V          ..................  462
                Floury, L           ................... 602        Hennigar, H. F., Jr    ...........     752         Klesczewski, K     ........   1405, 1411
                Fowler, P. K        ................    808        Herr, W. J          .................  1290        Klos, E            ................... 1529
                Fox, J. M           .................. 1536        Hervey, C. L        ...............    1482        Knaster, A. S      ................    156
                Fran@ois, D. K      ..............      241        Hester, W. H        ................   891         Kohler, C. A       ................    582
                Friday, P. M        ...............   1344         Hicks, D. C         ................   1049        Kontopidis, G      ..............      1207
                Frye, D. E          ..................  670        Higgins, M          ...........  1646, 1647        Koplin, S          ................... 132
                Fuentes, A. F. E    ............      1651         Hill, W             .................... 275       Kostinski, A. B    ..............      454
                Fulford, E. T       ...............   1244         Hillis, D           .................. 1045        Krahl, R. B        .................   250
                Fullmer, J          ................. 1677         Hodgkiss, W. S      ..............     310         Kreider, J         .................   1271
                Gaines, R           ................. 1605         Hotta, H            .................. 1253        Krezoski, J. R     ...........    437,442
                Galerne, A          ................  1573         Hout, E             .................... 994       Kristof, E         ..........  335,709,713
                Galloway, J. M      .............     1611         Hover, G. L         ...............    1448        Kroebel, W         ..................  491
                Gandy, R            ............ 1620,1648         Howell, G. L        ...............    1239        Krug, W            ..................  1400
                Garcia-Romero,      B  ...........    1198         Hoyle, W. R         ..........  1379,  1684        Kudo, K            ..................  1061
                Gast, J  .....................          346        Htun, K. M          ................   1628        Kuroda, Y          ..................  353
                Gaul, R. D          ................. 1149         Huang, L            ................... 413        Kurz, L            .................... 641
                Geraci, J           .................. 1634        Hultin, H. 0        .................    66        Kutzleb, M         ................    1444
                Gerritsen, J        .................   948        Humphrey, B         ...............    405         LaBelle, R. P      ................    1673
                Gibson, L. H        ...............   1326         Humphris, S. E      .............      1639        Ladner, L. J       ................    1202
                Giesecke, A. G      ..............      827        Hunt, C. D          ................   1632        Lakshminarayana, J. S. S      .....    1000
                Gilhousen, D. B     ............      1341         Hutchison, B. L     ............       1117        Lamb, G. R         ................    1131
                Givens, A           ..................  526        Hylas, T            ................... 372        Lambert, D         .................   397
                Gorveatt, M         ................    555        Ibrahim, M          ................   1612        Lamson, C          ................    1589
                Grace, P. J         ................  1218         Imai, K             ................... 1061       Lang, T. G         ................    1163
                Graham, D           ................  1018         Jaffe, J. S         ................... 338        Langdon, C         ................    1181
                Granger, S. W       ..............    16o4         Jagannathan, S      .............      1117        Larsen-Basse, J    .............       1628
                Grant, C            ................... 213        jai, B. H           .................... 473       Lataitis, R. J     .................   315
                Grant, L. V         ................  1365         Jalbert, J          .................. 1259        Lavoie, D          ..............  391,397
                Grant, S            ................... 567        James, B. D         .................  454         Lawrence, R. W     ............        1627
                Greenwald, R. J     .............       752        Jayko, K            ................... 740        Lawson, B          .................   1647
                Guffy, J. D         ................  1173         Jenkin, A. P        ...............    1315        Lea, C. E          ..................  1639
                Gundlach, E. R      ..............      847        Jenny, A. L         .................  812         Legrand, J. F      ................    602
                Gunther, H          ................  1212         Jensen, R. K        ...............    1039        Le Moign, T        ................    602
                Haas, T. J          ................. 1332         Jewett, K. L        ................   1668        Lennard, D. E      ..............      1034
                Hackett, H. P       ...............     607        Johnson, F. A       ..............     1034        Leonard, J. N      ...............     914
                Haines, L. C        ................    295        Johnson, M. G       ..............     896         Lewandowski, M. J      .....    865,1422
                Hall, S. C          ................... 537        Johnson, S          ................   1487        Lewkowicz, J       ..............      1594
                Hamilton, D         ................    637        Julson, B           .................. 1018        Liebert, B. E      ...........  6o6,i628
                Hamlin, B           ................. 1018         Junemann, C         ...............    1144        Lighty, K          ..................  1012
                Hamlin, C           ................. 1111         Jungck, M           .................  1560        Lindsay, R. C      ................      61
                Hammer, J. L., III    .....   1379,1684            Kadlec, J. A        ..................   46        Lissauer, M        .................   842
                Hamner, W           .................   713        Kai, G              ..................... 353      Liston, J          ....................   52
                Hamner, W. B        .............     1641         Kaiser, G. E        .................    76        Loaec, G           ................... 602
                Hansen, L. J        ................    819        Kalro, C            .................. 1603        Long,F.S           .................   1344
                Hanson, W. E        ...............     561        Kato, W             ................... 703        Lovell, G          ..................  1265
                Harlow, E. H        ..............    1250         Kawanishi, T        ...............    703         Luo, D             .................... 972
                Hawkins, J. S       ...............     925        Keer, F. R          .................. 188         Lynch,J.S          ................    1344
                Hay, A. E           ..............  413,419        Kennedy,J           .................. 213         Maccio, M          .................   1181
                Hayne, G. S         ...............   1702         Kennell, C          ................   1157        MacDonald, C. D      ............      880

                                                                                       xxviii.

           MacDonald, I         ................    90        Moser, C           ................... 505         Reetz, G            ................... 966
           Mac Gillvray, T. J   ............      262         Mozley, E          ..................  397         Reid, B             ................... 156o
           MacRae, T            ................. 1125        Murawski, S. A     ..............      726         Reighard, J. D      ...............     891
           Mahrt, K.-H          ................. 497         Murkin, H. R       .................     46        Renner, W. W        ...............     295
           Malone, R. F         ..............  70, 84        Murphy, D. J       ...............     1178        Replogle, F., Jr    .............       1436
           Mancini, E. A        ...............   762         Murphy, D. L       ...........  467, 687           Reynolds, M         ...............     1560
           Mangum, S. R         ..............   1656         Murrell, T. L      ................    699         Reynolds, W         .........  1422,    1605
           Martinson, D. G      ............     1335         Mushkat, P. W      .............       1589        Rezak, R            ...............  22, 1602
           Marziani, N. A       ..............   1463         Myre, P            ................... 1025        Rice, M             ................... 1144
           Masuda, Y            ................. 1067        Nayak, M. R        .................   615         Richardson, W       ......I ........    1400
           Mato, C              ................... 1025      Nebert, D. L       ...............     1627        Riedel, G. F        .................    23
           Matteson, L. L       ...............   987         Nergaard, D        ................    275         Robe, R. Q          ........... 1448, 1605
           May, D. R            .................. 681        Nestlebush, M      ..............      1400        Roberts, H. H       ...............     101
           Mayerson, D          ................  229         Newbury, T         ................    573         Robinson, D. P      .............       1688
           Maynard, W. M        .............    1371         Newell, C. D       ...............     1300        Roderick, D. K      .............       1619
           McCammon, D. F       ............      304         Nicholson, J. W    .............       338         Roehrig, S. F       ...............     1643
           McCandless, S. W,, Jr.      ........   479         Nixon, S. W        ...............     1604        Roffer, C           ................... 359
           McClure, A. C        ..............   1149         Noll, A D          .................   1087        Rogers, R. M        ................    953
           McCormick, M. E      ...........      1067         Novick, A          .................   1617        Rosati, J., III     ..............      1239
           McCoy, S. E          ................  930         Nuckols, M. L      ..............      1271        Rounds,R.S          ................    106
           McDowell, S. E       .............    1630         O'Hara, K. J       .................     12        Rowland, T. J       ...............     768
           McGehee, D. D        .............    1224         Ohtsuka, K         ................    1253        Rusch, K            ................. @ . .84
           McGrail, D. W        .............    1602         Okuno, K           ..................  353         Saari, D. A         ..................  812
           McKinney, J. P       .............    1224         Olivas, R          ..................  1018        Saklad, H           .................   1627
           McLain, C. E         ................  777         Olla, B. L         ..................  119         Salazar, M. H       ......... 1188, 1497
           McLellan, W. A       ..............    815         Olsen, C           ..................  1576        Salazar, S. M       ...............     1188
           McNitt, J. A         ................. 696         Olson, G. J        ................    1668        Samuels, G          .................   648
           Meade, J. G          ................. 815         Osmer, S. R        ................    687         Sanders, J. G       .............    23, 29
           Medway, W            ................  818         Outa, Y            ................... 1067        Sassen, R           ................... 101
           Mehrkam, L           ...............  1352         Owen, R. W         ...............     1457        Satkowiak, L. J     ..........   428, 433
           Meindl, E. A         ............ 629, 871         Parker, C. A       ................    794         Schiefele, P. M     ..............      318
           Mellen, R. H         ................  318         Paskausky, D. F    .......    1448, 1605           Schmidt, L          .................   790
           Mellinger, E. C      ..............    670         Paulet, S          ............. 1620, 1648        Schomette, D        ...............     335
           Melvin, K. P         ............... @ 1055        Pawlak, J. F       .................   719         Schroeder, K. R     ............        1390
           Merrill, R           ............ 1012, 1025       Pearce, J. B       ............. 732, 786          Schroeder,P         ................    268
           Merry, S. L          ................ 1315         Perreault, G. R    .............       1356        Schroeder, W., W     ..........      17,22
           Mes, M. J            .................. 1395       Perry, R. B        .................   366         Schultz, A. W       ................      17
           Mesecar, R           .............  505,518        Pfeiffer, T. F     ................    612         Schultz, H. E       ................    920
           Meyer, A             .................. 1018       Phillips, J. C     ................    372         Scott, G. P         .................   819
           Meyer, R. M          ................  146         Picciolo, A        ................    1400        Scott, J. L         .................   1231
           Michelena, E. D      ............     1649         Piccioni, R. M     ..............      1362        Sendlein, S. L      ..............      1315
           Middleton, R. W      .............     123         Pinkney, A. E      ...............     987         Serchuk, F. M       ...............     975
           Miller, J            ................... 1025      Pleass, C. M       ...............     1049        Shaw, A. R., III    ............        1384
           Miller, R. E         ................. 172         Ponsford, A. M     ..............      485         Sheehy, D. J        ...............     1470
           Miller, R. R         ................ 1650         Potter, C. W       ................    815         Sheifer, I. C       ................    937
           Millett, C           .................. 1276       Powell, E          .................   1178        Sheng,j             ................... 413
           Mills, W             .................. 1018       Predoehl, M. C     .............       1569        Sherman, T          ................    1265
           Mimken, G            ................ 1627         Prinz, S           ................... 1025        Shevenell, A P. . . 623, 1259, 1276
           Mingrone, J. A       .............    1618         Pryor, D. E        .................   379         Shumaker, F. E      .............       1149
           Mink, R. M           ................. 762         Quoidbach, D       ..............      1025        Siu, K. W. M        ...............     1716
           Mitcheson, G. R      ............     1049         Rabinowitz, P. D     ...........       1012,       Slade, D. C         ................    1006
           Moe, R. L            .................. 532                                      1018, 1025           Smith, C. E         ..................  250
           Molinari, P          ................ 1609         Raer, Y            .................... 602        Smith, G. A         .................   106
           Momma, H             ................ 1253         Rausch, K          ......... ** ...  *- .84        Smith, J. A         ................    1405
           Monkelien, K         ...............   699         Ray, P. K          ................... 193         Smith, N. D         ................    1374
           Moore, J. M          ............  385,509         Reed,J.C           ..................  202         Smith, R. J         .................   618
           Morton, J            .................. 899        Reed, M            ................... 847         Smith, s. m         ............. 385, 549

                                                                                   xxix.

               Smolowitz, R. j     ..............   975         Valent, P         ................... 397        Zaitzeff, j .................        1629
               Soden, D. L         ................ 891         van der Valk,     A. G ............    46        Zegowitz, V    ...............       1400
               Sorenson, S         ............... 1612         Vauthier, P       ................    1029       Zeller, R. W   ................        905
               Spears, A A         ............... 1173         Veentjer, j       .................   1487       Zielinski, A   .................       287
               Spooner, R. L       ...............  283         Vetter, W. j      ................    1540       Ziemer, F   .................        1212
               Sprunk, H           ................. 1286       Vik, S. F         ..................  1470       Zikakis, J. P  ................      1608
               Srivastava, S. K    ..............   485         Villemarette, G. P    ............    298        Zimmer, R      .................       794
               Stamulis, D         ................. 623        Voudouri, E       ........... I  .... 641        Zippin, J. P   ................      1615
               Stancampiano, J     .............    709         Waddell, P. J. A  .............       833
               Stanford, H. M      ..............   745         Wade, T. L        ................    1198
               Stang, P. R         ................ 1616        Wagner, j         ..................  518
               Steeves, G          .................. 567       Wainwright, P. F     ............     405
               Steffy, D. A        ................. 235        Waldmann, C       ...............     497
               Stein, S. M         ................ 1642        Walsh, E. j       ........... 1697, 1704
               Steinhauer, W. G    ...........     1630,        Walters, R. A     ...............     1405
                                           1631, 1632           Walther, M        .............. I ... 454
               Stevens, P          ................. 1400       Ward, j           .................... 637
               Stewart, G          ................. 405        Weaks, M. L       ...............     1626
               Stewart, H. B., jr  ............     840         Weaver, R. j      ...............     1362
               Stewart, L. L       .......... 1286, 1610        Weiss, P          ..................  1025
               Stockdreher, E      .............   1212         Weissman, D. E    ............        1546
               Stoddard, A         ................ 942         Wells, J. M       ................    1305
               Storey, D. A        ............... 1348         Welsh, B. L       ................    1633
               Strahl, D           ................... 549      Welsh, R          ..................  1259
               Strandquist, J      ..............  1124         Werme, C. E       .......... 1631,    1632
               Stumpf, R. P        ........... 808, 1569        Wheaton, F. W     ...............      76
               Sturgeon, W. j      .............   1163         Whelan, W. T      ...............     650
               Sullivan, P. K      ................ 606         Whitehead, J. R   ............        1507
               Sutherland, W. C    ............     632         Whittaker, H      ................    853
               Swanson, J. C       ...............  740         Whyte, R          .................   1646
               Swanson, R. L       ...............  794         Wicklund, R. I    .........   119, 1614
               Sweet, W. E         ................ 202         Wilber, R. j      ................    1639
               Swift, M. R         .................. 588       Wilcox, R         .................   1025
               Tadjvar, A          ................. 1628       Wilkinson, D      ................     90
               Tattersall, J. M    .............   1618         Willard, M. R     ..............      1625
               Tauxe, j            .................. 1018      Williams, K. L    ...............     428
               Taylor, P. R        ................ 803         Williams, R. G    ..............      346
               Teal, J. M          .................. 177       Wilson, B         .................   1202
               Teel, S  ....................       1582         Wilson, D         ..................  359
               Tennyson, E. j      .......... 853) 857          Wilson, E         .................   1178
               Tester, P. A        ................. 808        Wilson, W. B      ...............     629
               Thomas, A           ................ 1045        Wingert, R. C     ................    150
               Thomas, W. M., jr     ..........    1656         Winslow, T. S     ..............      1390
               Thomasson, A P      .............       70       Wolniakowski, K. U      ..........    994
               Thompson, B. G      ...........     1613         Woodward, W. E       ...........      1348
               Thurberg, F. P      ..............   736         Woolweaver, G     ............        1265
               Tompkins, A E       ..............      35       Wright, A. St.C   ..............      323
               Traub, G. L         ................ 1493        Wright, D. A      ................    987
               Treacy, S. D        ................ 180         Wu, L   .....................         287
               Tremblay, H         ................. 522        Yamazaki, T       ...............     1067
               Trout, T. K         ................ 1668        Yee, M. C         ..................  555
               Trulli, W. R        ................ 1630        Y-Hsieh, T. C. T     .............     84
               Trutneff, H. F      ...............  902         Young, A. G       ................    423
               Tsuzuku, T          ................ 1061        Young, D. R       ................    745
               Turner, E           ................. 1616       Yu, D. W          .................   1098
               Turner, R. E        .................   41       Zachritz, W. H.   ,II  ............    84
               Tuxhorn, R. L       ...............  691         Zagel, J. j       .................   1642

                                                                                      xxx.

                                           Deep-Ocean Tests of an Acoustic Modem
                                               Insensitive to Muleipath Distortion

                                                      Winfield Hill, Gerald Chaplin, David Nergaaxd

                                                         Sea Data, Inc., A Pacer Systems Company
                                                       1 Bridge Street, Newton, Massachusetts, 02158

              Abstract                                                            by multiple sound pathways, bottom and surface scattering
                                                                                  and moving inhomogeneities in the ocean('). However the
              The concept, design and ocean testing of a new low-power            repeated observation of such degradation has obscured the
              acoustic modem is presented. The telemetry system em-               fact that sound transmission quality over direct vertical or
              ploys a novel "chirp" frequency sweep and has other fea,            slanted pathways (other than in a sound channel) may be
              tures to allow operation in the presence of multipath inter-        quite good(').
              ference. The chirp system uses fsk data modulation and              Kearney and Laufer(") demonstrated this point whil      e de-
              performs a carrier sweep starting at 9 or 31kHz, depend-
              ing upon the model, to obtain the benefits of frequency             livering a paper at Oceans '84, by playing a cassette tape
              diversity without requiring a frequency synthesizer, multi-         recording of voice and music transmitted from 1500 me-
              ple filters or a FFT analyzer. Intended for retrofittable to        ters depth to a shipboard recorder; my memory is that the
              existing instruments, the new system is designed for use in         primary degradation was due to the use of a very poor cas-
              the deep ocean and the continental shelf over distances to          sette recorder. Designers of acoustic high-resolution pos-
              6km. Ocean tests were performed in about 4000 meters of             tioning systems have long taken advantage of good direct-
              water using the low frequency version. Additional shallow-          transmission paths by detecting the axrival of short acoustic
              water tests are planned, including a typical harbor.                pulses using narrow-band (Q > 30) filters('). When used
                                                                                  at low frequencies (10kHz), these positioning systems re-
              ocean       acoustic telemetry      multipath                       quire several milliseconds of phase coherence in the leading
              frequency diversity       modem        chirp                        edge of the pulse. Short-range (< 400m) acoustic telemetry
                                                                                  systems have been constructed   (6,7) using simple frequency-
                                                                                  shift keying (fsk) modulation in the expectation of a reliable
                                                                                  acoustic path, with some success. One system transmits at
              .1. Introduction                                                    the v*ery slow rate of I bit-per-second(') to achieve up to a
                                                                                  1000m range.
              Real-time observation of data is a commonly desired capa,           2.1 Multipath. Despite the good quality of a direct path
              bility which is not commonly available in undersea oceano-          or reliable-acoustic-path signal transmission channel, most
              graphic instruments. Although convenience and peace-of-
              mind may be occaisional motivations for these desires, strong       practical underwater acoustic systems must contend with
              axguments have been made for the value of this capability(').       strong undesired signals scattered from the surface or the
              These include use in real-time operational systems, multi-          bottom. This is especially true when one of the acoustic
              year deployments (where it's impractical to wait until the          transducers is near the ocean surface. Superimposing the
              end for the data), performance monitoring, repair flexibil-         surface-scattered signals upon the direct-path signal causes
              ity and expendible instrumentation. We report here on the           fading and phase instabilities, possibly including complete
              design and initial ocean tests of a new chirp acoustic teleme-      cancellation of the desired signal for a few milliseconds from
              try method, which has simplicity and reliability properties         destructive interference. Therefore, a pulsed one- or two-
              desirable for fitting acoustic telemetry data links to existing     frequency signal, which begins with good receive quality,
                                                                                  deteriorates as multipath interference arrives.
              :undersea instrument designs.
                                                                                  As an example of simple two-frequency fsk telemetry per-
                                                                                  formance when surface and bottom scatter have a strong
              2. Background - Ocean Acoustic Telemetry                            influence, consider the experiences of Ryerson at Sandia
                                                                                  Labs('). Transmission from a 10m subsurface buoy with
              Underwater sound travelling a substantial distance in the           a slant range of 180 to 280 meters to a surface buoy was
              sea suffers from severe amplitude fluctuations and phase            desired. Water depth was 200 meters. Optimum perfor-
              distortion. Acoustic temporal incoherence may by caused'            mance was obtained only after a variety of system-tuning

                                                          CH2585-8/88/0000-275 %1 @1988 IEEE

                    changes were made. Operating frequencies were selected                   When the transmitter is straight below (A = 0 and we
                    (near 50kHz) to reduce transducer backside and side-lobe                 0), equations (2) above simplify to:
                    response and to attenuate long, multiple-reflection paths.                                  d
                    In mid-experiment, the receive transducer depth was in-                            Pj           + Vh2 + -(dt.B)2 - (h - d)               (2c)
                    creased by one meter. Also, lower error rates were achieved                              cos B
                    with a -12dB power change (0.6 watts instead of the design
                    level of 10 watts). An 85 to 90% success rate was achieved.              The first delayed surface-scatter multipath arrival occurs
                                                                                             at Td = 2d/c, when the axrival angle B = 0 (surface angle
                                                                                             = 90*), followed by more sound arriving for B > 0. The
                                                  WC           B                             first arrival delay is about 27ms for a receive hydrophone
                                                                                             depth of 20m.

                                                                                             For slanted sound paths (A > 0) equation (2a) shows that
                                                                 T                           the surface-scattered first-axrival delay time is slightly faster
                                                                   d                         than for the direct overhead case; the shortest path occurs
                                                                                             for equal angles of incidence and scatter at the surface. As
                                                                                             an example, for a transmitter in 3000m of water, to a 60m
                                     h                                                       deep hydrophone at a 2000m watch circle distance, A = 34           0
                                                                                             so the surface incident angle (given by 90'-A) is about 55'.
                                                                                             Sound scattered at 55* from the surface (B = 351 will ar-
                                                                                             rive with a 67ms delay (compaxed to 80ms for the straight-
                                                                                             below case). Straight-line sound travel has been assumed
                                                                                             throughout, even though for a slanted direct path sound
                                                                                             travel is actually slightly curved, due to refraction by the
                                                                                             sound-speed depth profile; This does not affect our conclu-
                                                                                             sions.

                                                                                             After the first multipath axrival, sound travelling longer
                                                                                             paths continues to arrive for a substantial period of time;
                    2.2 Surface Multipath. A common surface-path sit-                        this additional sound constitutes most of the multipath in-
                    uation is illustrated in figure 1. The offending surface-                terference. Some of the sound has travelled very complex
                    scattered (backside arrival) signals clearly travel a longer             pathways, involving volume scatter as well. Although the
                    path than the direct path signal and therefore take a longer             multipath signals suffer surface-scattering losses(16) of 10 to
                    time to arrive. The earliest-arriving scattered signals take             20dB, the beneficial effects of these losses are reduced by
                    a,n extra delay time (Td) to travel an extra path delay (Pd)             the large area of the surface. The desirable losses are fur-
                    as follows:                                                              ther reduced during high sea-state conditions, when acous-
                                                                                             tic surface scattering increases (e.g. see the backscattering
                                                                                             curves in ref 15 p. 264). However, for frequencies above
                                                Td = PdIC                            (1)     20kHz (e.g. 33kHz), wind velocities above 10 to 15 m/s
                                                                                             may actually cause reduced surface-scatter sound due to
                                                                                             sound attenuation by small-bubble populations in the top
                                                                                             5 meters of the ocean(17).
                      Pd =     d +,lh2+[(h-d)tanA-dtan                      -h-d
                             @os_B                                            cos A          2.3 Fighting Multipath. Several methods have been sug-
                                                                                    (2a)     gested to reduce signal degradation by multipath interfer-
                                                                                             ence. One is to use a transducer with high back rejection
                    where d is the receive transducer depth, h is the transmitter            (or use a baffle). In the 3000m example above, the first
                    depth, A is the transmitting slant angle, B is the scattered-            offending sound arrived at an angle of 145* from the trans-
                    signal receive angle (both angles axe measured from the                  .ducer forward direction (given by 180' - A,        assuming the
                    vertical) and c is the speed of sound in seawater, about                 transducer is pointed down). A second method is to cre-
                    1.5m/ms. The surface watch-circle radius (we) i          s related       ate a highly-directive receive transducer array("'). These
                    to the slant angle by we = (h - d) tan A. If the watch circle            approaches increase the cost of the system, are painful to
                    radius is known instead of the slant angle A, equation (2a)              implement at low frequencies and have limited utility for a
                    can be written:                                                          variety of reasons. Furthermore, in shallow water, directive
                                                                                             sensors may not be very helpful.
                               d + Vrh -2
                      Pd                    + (we - dtan By - Vr(h - d)2 + WC2               Acoustic transmission in shallow water is much more dif
                             cos B                                                           ficult than in deep water, since it suffers from the exis-
                                                                                    (2b)     tance of many strong sound pathways to the destination,

                                                                                         276

               iinvolving varying numbers of surface and bottom reflec-            where TS is the duration of the sweep and f, and fs are
               tions. Computer modelling(7,") indicates that for 10kHz             the starting and ending sweep frequency and M(t)          r= 0
               transmission in 200m deep water, the Direct-to-Multipath            or 1 according to the data bits. The modulation ampli-
               signal Ratio (DMR) may be as poor as 6 dB at ranges of              tude, f2, is chosen large enough, e.g. > 15OHz, to eliminate
               less than 1000m. Actual measurements in the ocean may               doppler-shift spreading problems, which will be less than
               give even poorer DMR. Higher-frequency transmissions will           40Hz (0.33Hz/kt per kHz).
               experience increased sea-water absorption attenuation for           If the receive frequency is accurately swept to match the
               the longer multiple-bounce pathways, but less than 5dB of
               improvement is calculated at 50kHz, due to this effect.             transmitter, a small receive bandwidth (constrained by the
                                                                                   data rate and the fsk 0,1 frequency shift) can be used, just
               Frequency-diversity sound transmission methods have been            as in a conventional fsk system. A small bandwidth will im-
               developed("') to solve the multipath problem. Systems               prove the signal-to-noise ratio (SNR) not only by rejecting
               with many frequency channels(",",") have been proposed,             ambient noise but also by rejecting the (delayed) multipath
               even up to 32 frequencies  (14), so that the system can switch      energy from the "old-channel" frequencies.
               to a new frequency before the multipath interference ar-
               rives. In a common approach, the frequencies in use are             In a chirp telemetry system, the effective frequency-diversity
               Ichanged every 50 to looms, allowing the multipath energy           channel usage time (T,,) can be equal to the time required
               to decay on the old channel. Since the decay time allowed           for the carrier frequency sweep to change by more than the
               before a channel can be reused is proportional to the num-          receive bandwidth (BW), as follows:
               ber of available frequency channels, this may well be a true
               case of "more is better". Of course the telemetry system                                               TS
               will become more complex, but the improved results that                                   T,, = BW   f3 - A                      (6)
               .Can be obtained in all environments are very attractive.
                                                                                   The usage time can be easily set at under 50ms (e.g. BW
                                                                                   = 30OHz, sweep 400OHz in 650ms), allowing excellent re-
                                                                         f3        jection of multipath signals.

                                                                                   As an added benefit, the new chirp telemetry approach
                                                                                   can be inexpensive, compared to other frequency-diversity
                      START BIT                                                    methods, since multiple frequencies are not required (i.e.
                                             fp                                    no synthesizer) and receive decoding can be simplified (Le
                                                                                   ,no multiple filters or FFT analyzer). To understand our
                        f,                                                         approach and the role of all the elements in the sweep wave-
                                                                                   form of figure 2, we'll start by considering how the receiver
                 f 0 1+- to -*I t,                                                 works (see figure 3).
                                                                                   3.1 Signal Description. Because a telemetry receiver
                                                                                   contains many circuit elements that consume electrical power,
               3. A New Chirp Telemetry Method                                     it's desirable to switch the power to a portion of these cir-
                                                                                   cuits. In the receiver design above, a number of components
               The new Sea Data chirp acoustic telemetry system is based           are continuously powered in order to detect the arrival of
               upon a variation of the frequency-diversity idea: use an "in-       an alert signal. These are the preamp, Al, a bandpass fil-
               finite number" of frequencies. This is achieved by sweep-           ter, BP, the fo detector and a power-control circuit (for our
               ing the telemetry carrier frequency while applying fsk data         experiment, fo = 9.0kHz). The bandpass filter is designed
               modulation (fig 2). The transmitted signal P(t) is a single         to pass signals over the entire fo to f3 range of the system
               frequency, starting at fl, and changing at a smooth rate            (a double- or triple-tuned filter) and to reject intense low-
               df Idt, plus fsk frequency shifts with amplitude f2:                frequency noise from shipping, etc (extra LF cutoffs). The
                                                                                   fo energy detector operates on a principle similar to that
                                                                                   used by many high-resolution acoustic positioning systems
                                     P(t) = cos[w(t)t]                    (3)      (5): an amplitude limiter (to establish constant power), a
                                                                                   sharp fo filter and a comparator with a time constant, work
                                                                                   together to determine if the fo energy present is above the
                                                f                                  background noise adjacent to fo by a threshold amount.
                             W(t) == 27r h + �-t + f2M(t)                 (4)
                                         (      dt                                 When the fo alert-tone energy is detected, the remainder
                      START B@IT@
                                             fp
                        fl

                                                                                   of the receiver, including the microprocessor, is turned on.
                                        df   f3 - fi                      (5)      After a short time, to, the transmitter shifts its frequency to
                                        dt      Ts                                 f, (for our test f, = fo + 60OHz), creating the data-trigger

                                                                              277

                                                                                          BP
                                                                     Al                                          F0                    POWER
                                                      _iR                                                      DETECTOR              CONTROL
                                                                                                                                                      SWITCHED
                                                                                                                                                        POWER
                                                                                         LIMITER                 F,                    SWEEP
                  tone. This trigger tone "start pulse" is detected by the                                    DETECTOR                   GEN
                  f, energy detector (sirnilar to the fo energy detector) and@.
                  .is used to start a sweep generator and voltage-controlled                                                fL0
                  oscillator (VCO). The resulting frequency ramp is designed                             MIXER
                  to precisely track the transmitter's sweep with a fixed offset,                                                   +5
                  frp, where f1F > (f3 - fo)/2 to avoid images. This ramp
                  frequency is the local oscillator (LO) input to a mixer, and.                               LP                       R2
                  .has a frequency, Ao , similar to equations (3) to (5) except                               LF
                  as follows:                                                                                             VC0
                                    A0 = At) = h + @f       t + hp                  (7)                                          Cl RI
                                                          dt
                  The resulting intermediate frequency (IF) output from the                                              CLAMP
                  mixer after IF-stage filtering is:
                                      v(t) =zz sin[27rf (t)t] + n(t)                (8)     manner to maintain the VCO output frequency near w(t)
                                                                                            in formula (9). Further filtering of the input to the VCO -
                                                                                            a varying dc voltage v(t) oc w(t) - along with ac-coupling
                                         f (t) = fIF + AM(t)                        (9)     and clamping, yields the original data-stream signal, M(t).
                                                                                            The PLL loop filter and low-pass filtering of M(t) set the
                  where n(t) is the received noise, with a noise bandwidth                  noise bandwidth, BW, of the telemetry receiver. The re-
                  given by the IF-stage bandpass. This signal is limited and                ceiver should be able to operate with very low SNRs, al-
                  applied to a frequency discriminator to track f2 and deter-               though the data error rate may not then be zero.
                  mine whether M = 0 or 1. A data precursor time delay, t,
                  in fig 2, allows the circuits to settle before data discrimina-
                  tion must start. Also a warmup time, tw = to + t1, less the               4. Mransmitter
                  fo detect time, is available for-the crystal in the receiver's            The transmitter (figure 4) helps illustrate the simplicity
                  microprocessor to s    .tart, etc.                                        of the chirp telemetry scheme. A few low-data-rate con-
                  The frequency discriminator in fig 3 is a phase-locked loop               trollable outputs from the instrument's microprocessor are
                  (PLL) circuit, which forms a tracking filter to further nar-              sufficient to operate the transmitter. These outputs include
                  @row the noise bandwidth of the receiver. The input stage                 the sweep generator power control, an enable for the output
                  of the PLL is a limiter that responds to the strongest sig-               driver as soon as the VCO is stable, a start pulse (SP) shift-
                  nal within the IF bandpass and acts to reject any weaker                  ing the frequency for a data trigger, a sweep enable (SE)::
                  signals, thereby further rejecting (quieting) unwanted mul-@'             and the data bit (DB) modulation signal. Another line sets          :
                  tipath signals. A full-wave mixer phase-detector circuit                  the sweep rate (SR) to allow optimizating the system for
                  (exclusive-OR) and the PLL loop filter act in a                           deepsea or shallow-water use.
                  noise-insensitve

                                                                         +5
                                                                 POWE

                                                                                                         BATTERY LI
                                                                                                             V8
                                                  SYSTEM                 SWEEP                                                   RI
                                                    PP                     GEN/               OUTPUT
                                                                       MODULATOR              DRIVER                               X1

                                                                     ENABLE                                     TI
                                                                     3R

                                                                     S
                                                                     P
                                                                     P                                            OF
                                                                     S
                                                                     SE
                                                                     S
                                                               TD

                                                                                       278

               At low frequencies, e.g. lOkHz, obtaining a transmit op-               4.2 Design Simplicity. Because I always miss the ab-
               erating range of 5kHz is a challenge, due to the narrow-               sence of electronic-circuit schematics at IEEE conferences,
               band nature of a tuned acoustic transducer. In figure 4,'              I'll be sure to include one here. Figure 5 shows details of
               the reactive component of transducer X1 is removed us-                 the transmitter sweep generator and serves to further illus-
               ing tuning coil L1, with a series resistor R1 to increase the          trate the simplicity of our new approach, while giving me
               frequency range. In the 9 to 14kHz experiment to be de-                a chance to dispel any concerns over drifts, tuning, etc.
               scribed, a modified ITC type 3013 transducer (which nor-
               mally has transmit-voltage-response peaks at 9 and 14kHz)              The most important component is the voltage-controlled
               was used with a 22mHy choke and a 50 ohm damping resis-                oscillator (VCO) chip U4, an Analog Devices AD537, which
               tor. A very acceptable calculated network output flatness              operates at twice the transmitter output frequency. This
               (+140�2dB/V) was obtained over a 7.5 to 14kHz range,                   VCO chip creates a very stable frequency and has low
               and verified with pulsed measurements in the local YMCA                power-supply and temperature drift coefficients (0.01%/volt
               swimming pool. If necessary, a more complex network could              and 0.03%/10 degrees C). When used with stable compo-
               be devised. When operating the system with 5kHz sweeps                 nents (capacitor C1 and resistor RIO are low-tc compo-
               at 33kHz, using a custom-designed transducer, a damping                nents), the AD537 may allow a circuit with lifetime factory
               resistor is less important.                                            calibration. The VCO follows the formula f = V3/[IO(R9
                                                                                      + RIO) C11. Here R9 sets the exact coefficient for the VCO
               4.1 Power. In the deep ocean test, the output stage con-               frequency-programming voltage, V3, which comes from am-
               sisted of a pair of VMOS transistors driving a center-tapped           plifier A3 (LM10, chosen for ImA sink capability when
               transformer with a regulated 12V input. This provided                  V,,,,t = 0.2V at the end of the sweep). This amplifier's
               about 20 watts of power into the transducer network and                summing junction allows the telemetry system operating
               yielded a modest calculated source level of +179dB re 1jUPa            parameters to be exactly ratiometrically determined by pre-
               at 1m, confirmed in the pool test. The current drain from              cision resistors RO, R1 and R2 according to the following
               the instrument battery was less than 2A during transmis-               formula:
               sion, a very acceptable level for any instrument with several
               3tacks of alkaline batteries.
               Although lower power levels may be used in practise, our                                  2f = 2k F, +        dFj                  (10)
               thought was to get good quality data on the experiment                                                          I )
               DAT tape and subsequently degrade it with noise when we                where F0 = I/RO sets the fo alert frequency, dF, = 1/R1
               tested transmit codes and receiver designs in the lab. How-:           sets the f, - fo data trigger frequency shift, dF2 = 1/R2
               aver the higher-power energy usage is not unattractive: At             sets the f2 fsk modulation level and dF3 = 1/R3 sets the
               300 baud, less than 0.1 Joules per bit is required, including          sweep rate (and hence f3). Amplifier Al (OP-20, chosen
               alert tone, etc. Since a single stack of alkaline D-cells con-         for low offset voltage) creates a reference 1-volt above the
               tains about O.5MJ of energy, it could power about 100,0M               amplifier-reference signal (also 1 volt), so that k ='R8. In
               transmissions of 50-bit data blocks.                                   ithe experiment, an electronic switch selected two values of'
                                                                                      R2 to allow-two fsk modulation levels.
                      IK       ... C2 X44(                                            Amplifier A2 (OP-90, chosen for low input current and off-
                           ,SE                                                        set voltage) is a ramp, which operates (when switch SE
                        R4                      R3                                    opens) with an integration constant r =(R4+R5)C2. The
                                                                                      integrator uses voltage source trim R6 to allow two cali-
                           +1                 28-OK                  R8
                                      OP-90                   6      YA               brated sweep rates according to the resistor ratio R4/R5
               SR       R5                                         4.99K M,
                        R6 R7         +2V               +1            >_ 0                   C13nFX440
                     2       166K 1%                             DLMIO        IR9                      12      +5
                           +1 +                       RO               200:1 F -'I
                                     Al               ---                               Emitter - Coupled        fIOK
                                                                       RIO              MULTIVIBRATOR         14
                                     OP-2               R 1            826    :
                                                                              3
                                                                                                                     2f
                               li@. 140*AOK      SID                          4                                1
                                                        RZ                    5
                                                1_@@                                                             -
                                      +1         D13                          7
                                                                 +1                     1.00 volt
                                                                          j___              once         U4    AD537
                        R4 @SE                                   VR          0.1
                           -I@
                                      np_.
                        R  -
                           r
                  R@
                        R(
                      20K      46K
                                    I%

                               1%  1OOK I-       SI
                                      +1                                      5
                                                                             $7         1.00 volt
                                                                                      'T8

                                                                                 279

                 and switch SR. The sweep generator operates on 5.0 volts             signal strength o +99dB re          near the surface, is about
                 (�5%) supply, and the entire circuit requires only two sim-          16dB louder than the wind noise for 20m/s (NSL = +59dB
                 ple calibration points, yet we're able to get our "infinite"         at 10kHz), assuming a 30OHz receiver bandwidth (+25dB)
                 frequency channels.                                                  and an isotropic receive transducer (DI = OdB).

                                                                                      5.1 Shallow water. Using 33kHz in shallow water at
                 5. Signal Propagation Loss, Noise, SNR                               10'C, 3km of range will result in about -22dB of absorption
                                                                                      loss, assuming the actual (scattered and reflected) path is
                 The expected signal-to-ambient-noise ratio (SNR) can         be      30% longer than the range. Since the sound is in a channel,
                 ,calculated (in dB) by subtracting the speading and attenu-          the spreading loss may be less than the -69dB value from
                 ation losses and the background noise level from the trans-          formula (11), say +10dB for 30m water depth (2). The
                 mitter source level:                                                 nal system SNR is similar to the case above since NSL is a
                                                                                      bit lower at 33kHz. Because 3km of range in shallow water
                                                                                      will be subjected to severe multipath interference, the sweep
                  SNR = SL - 20 log(r) - ce     r _   NSL-10log(BW) (11)              rate may increased and the data rate may be decreased to
                                              1000                                    combat this. Also, the telemetry system's processor can
                                                                                      easily allow using slower data rates, with 25ms dead peri-
                 where SL is the source level (dB re ljzPa at 1 yaxd), cor-,          ods in between each bit, to allow the immediate multipath
                 rected for the transducer directivity index, r is the range          energy to decay.
                 (yards - not kni), ce is the seawater attenuation coefficient
                 (less than IdB/km for frequencies below 15kHA, NSL is the            6. Sea Mial using a DAT Recorder
                 ambient-noise spectral level (dB re 1,uPa/N/Hz), and BW
                 is the receiver bandwidth (Hz). The equation assumes a               The experiment was performed on 16 to 17 June 1988 dur-
                 low-noise receive preamp and does not include the improve-           ing cruise OC200 of the WHOI vessel RN. Oceanus, at a
                 ment a directive receive transducer will provide in rejecting        site approximately 400 miles east of Cape Hatteras, just
                 (wind-generated) surface ambient noise, which could exceed           north of the Gulf Stream, in 3775m of water. The undersea
                 .6dB.                                                                transmitter for the experiment operated over a range of 9
                 The seawater attenuation is due to magnesium-sulfate ionic           to 14.5kHz and was installed in a Sea Data model 1665 In-
                 relaxation with an absorption coefficient of about 0.7 and           verted Echo Sounder (IES), deployed on the bottom. The
                 5.5 dB/kyd (at 100C and zero depth) for 12 and 35Hz, re-:           :receive hydrophone was the standard EG&G acoustic re-
                 spectively (see ref. 15, page 109 and ref. 22). Over the             lease deck-set sensor (an ITC 3013 transducer), suspended
                 range of 8 to 5OkHz, the absortion coefficient increases by          over the side of the ship about 18m below the surface. A
                 the square'of the frequency, decreases about 7% for each             custom-built preamp with a 5kHz 2nd-order bandpass filter
                 1000in of depth and increases about 2% for each 'C of tem-           was used with the hydrophone.
                 perature decrease. The latter two effects tend to cancel
                                                                                      To test the new telemetry system, we elected to transmit
                 each other out in the top half of the deep ocean. Applying
                                                                                      test signals from the ocean bottom to various lab-based re-
                 the formulas to expected ocean conditions yields the values          ceiver circuits via a shipboard precision audio recorder. In
                 below, which can be integrated over 'the sound propaga-'             this way we could perform receiver tests in the lab with var-
                 tion pathways to determine the absoption loss for various            ious, noise levels and different types of interference, using a
                 telemetry applications.

                      Depth (m) Temp (*C) Attenuation (dB/kyd)
                                                  @10kHz        @33kHz
                           0             20         0.65          4.5
                         3000            4          0.50          3'.3
                          6000           4          0.38          2.4                                                   d

                                                                                                SURFACE
                 When using the system in deep water, with a 5krn path, we                    SCATTERED               RECEIVE.
                                                                                                 PATH
                 can calculate a 16dB expected SNR for (poor) 20m/s wind
                 conditions, as follows: Given the TVR of the transducer                                       DIRECT
                 at +141 dB per volt, and considering a 1.5dB; loss for the                                   PATH
                                                                                        TEST
                 50ohm. tuning resistor, we can calculate an output acoustic          ROGRA
                                                                                                                                     DAT

                                                                                                                                 RECORDER

                 intensity of +178dB, for 20 watts (this was      'confirmed in
                 the pool test). We lose -74dB from 5km spreading and-                                                         6
                 5dB from attenuation (at 10kHz). The resulting calculated                           TRANSMIT
                                                                                          77777-7.77" Pr7-r777

                                                                                 280

                large variety of transmission types as they were actually.        7. System Considerations
                ,received in. the- ocean. We used a small portable 16-bit dig-
                ital audio tape (DAT) recorder (Technics mo,   del SV-MD1,        The receiver and transmitter of the acoustic modem each
                complete with a manual entirely in Japanese). Thus we             occupy one card, as does the processor. The 33kHz trans-
                were able to obtain "perfect" (90dB dynamic range, flat to        ducer is very small, 1.6-in (4cm) in diameter, and is con-
                18kHz, 0.01% time stability) digital analog recordings of         structed with an O-ring groove and 3/4-16 stud with em-
                the received hydrophone signals.                                  bedded wires, to allow it to be screwed directly into an
                                                                                  endcap. Thus, the system can easily be added to many
                During the experiment the transmitter variables were cy-          existing designs. A standalone version mounted in a small
                cled through a variety of combinations using a parameter          housing with a battery is planned as well.
                table in the microprocessor's program. The parameters in-
                cluded: data rates (100 to 360 baud), modulation index            The final telemetry system software will employ a data
                (300 and 50OHz), chirp sweep rate (10 and 40kHz/s), chan-         transmission protocol suited for systems applications, and
                nel decay "quiet times" (62ms to 14s), transmit duration (1.      error checking features. A unique code can be sent from
                to 10 bytes/record and 3 to 80 records) and the transmitted       each transmitter for identification. Controlled redundancy
                data patterns.                                                    can greatly reduce the eff or rate: block error-correction
                                                                                  codes such as the Reed-Solornon code   (21) can allow for cor-
                During the experiment the receive variables included slant        rection (after reception) of up to 15 errors within a 155-bit
                range and Dolphin activity level. Winds of 10kts and a
                                                                                  .block while achieving an 80% code rate (125 data bits).
                steady rainfall both occurred at various times during the
                experiment. The experiment was performed with the low-            Although both receiver and transmitter cards will often be
                frequency version (fo = 9kHz), since all the available com-       located at both ends of a system, creating a full underwater
                ponents (IES transmit stage, receive hydrophone and DAT           MODEM, telemetry systems can be substantially simplified
                recorder) weighed against the 33kHz version.                      if one-way data transmission is used. If stable timebase os-
                                                                                  .cillators are employed("), offset time-slot channels may be,
                Initial oscilloscope examination of the DAT tapes shows      3    established so that many undersea instruments can trans-
                to 10dB of fading after the sweep was under way (due to           mit to a central receiver (20) on a single frequency, without
                multipath?), -6 to -10dB of delayed (obvious) multipath           requiring a command for the transmission. Furthermore,
                interference and a +10 to +20dB SNR (4kHz noise band-             studies have shown(') that a one way acoustic data trans-
                width), depending upon surface conditions.                        mission system can be optimal, e.g. "Analysis of the ADTL
                                                                                  data indicated that command and retry provided only min-
                The concept of using a DAT recording to provide receiver          imal improvement in the amount of data passed without
                test signals has proven to be very useful. At this writing,       errors."
                excellent performance has been obtained playing back the
                tapes into our prototype receiver. In this fashion we will
                easily be able to optimize the performance of the receiver
                design with tests using bench instruments, e.g. the SNR can       .8. Conclusion
                be degraded with noise generators. Already, we were able to
                painlessly test the improvement that a CMOS-switch ana-           It is our expectation that considerable improvement over
                log mixer provided over a limiter/XOR-gate mixer. Further         other traditional methods will be experienced with our new
                DAT recorder ocean experiments are planned in shallow             swept-frequency telemetry, at a reduced cost. It is our hope
                water.                                                            that our work will help lead to a greater and happier use
                                                                                  of acoustic telemetry in the ocean.
                6.1 Dolphins. We experienced considerable interference
                from dolphins, who were curious about the ship and enjoyed
                playing with the hydrophone. A few dolphins used their            9. Acknowlegments
                variable-rate pulse sonar to locate and "ping" the trans-
                ducer; at closest approach they increased the ping rate to        One of us (GC) wrote some of the transmitter software
                buzz.- Like our hydrophone, the    IdolphinsIcould.hear   the     and singlehandedly (!) performed the undersea experiment,
                transmitter on the ocean bottom. Amazingly, they did a            during the wee hours when the rest of the ship was asleep,
                good job of mimicking the 9 to 14kHz sweep signal of the          while another (DN) modified the IES undersea transmitter
                telemetry! But we haven't yet decoded their transmissions         and constructed preamps and prototype receivers to ana-
                (Does anyone know, do they use ASCII code? And if so,             lyze the DAT tapes. Special,thanks are due to Kevin Boyce
                is it Isb first?). It was necessary to move the ship several      for creating a major portion of the original IES micropro-
                times, and to turn off the fantail lights. This may be an         cessor code, to Dan Frye and others at WHOI for their,
                axgument in favor of higher frequencies, such as our 33kHz        suggestions and review of telemetry system goals and to'
                version.                                                          Prof. Randy Watts at URI for his encouragement.

                                                                             281

                                                                                                                    (11) Zielinski, A. and Caldera (1985). Digital Acoustic Communications in Multi-
                                                                                                                    path Underwater Channels, Oceans '85, pp 12W1301.
                        10. References
                                                                                                                    (12) Caldera, M.K. (1987). A Multi-Frequency Digital Communication technique
                                                                                                                    for Acoustic Channel with Multipath, Oceans '87, pp 140-145.
                        (1) Parker, B.B. (1985) Real-Time Oceanographic Model Systems: Present and                  (13) Catipavic, J., Baggeroer, Heydt and Koelsch (1984). Design and Performance
                        Future Applications, Oceans '85, Proc. IEEE-MTS Conf., pp 204-214.                          Analysis of a Digital Acoustic Telemetry System for the Short Range Underwater
                        (2) Urich, R.J. (1982) Sound Propagation in the Sea, Peninsula Publishing, Los              Channel, IEEE J. Oceanic Engineering, OE-9(4), pp. 242-252.
                        Altos, CA, chapter 10-12.                                                                   (14) Gastounioties, C. and Moropoulos (1985). Programmable Deep Ocean Tran-
                                                                                                                    ceiver, Oceans '83, pp 145-149.
                        (3) Coffey, D.M. and Paquett@-flggS).--A-nuracy-ofA:cousticMultipath Timing-and-
                        Ranging Predictions over Extended Ranges, Oceans '85, pp 480-489.                           (15) Urich, R. (1983). Principles of Underwater Sound, 3rd Ed, McGraw-Hill.
                        (4) Kearney, P.O. and Laufer (1984). Sonarlink - A Deep Ocean High Data Rate,               (16) Eller, A.I. (1985). Implementation of Rough Surface Loss in Sonar Performance
                        Adaptive Telemetry System, Oceans '84, pp 49-53.                                            Models, Oceans '85, pp 494-498.
                        (5) Vijayakumar, G. (1982). Acoustic Navigation - New Microprocessor Generation,            (17) Farmer, D. and Lemon (1984). The Influence of Bubbles on Ambient Noise in
                        Oceans '82, pp 100-105.                                                                     the Ocean at High Wind Speeds, J. Physical Oceanography, 14 (11), pp.1762-1778.
                        (6) Scally, D.R., Ryerson amd Towles (1984). Acoustic Telemetry in an Automated             (18) Zielinski, A. and Wu (1988). Data Retrieval from Bottom Instrumentation
                        System for Long-Term Ocean Data in Real Time, Oceans '84, pp 748-752.                       Using Acoustic Link, Instrumentation and Measurements in the Polar Regions,
                                                                                                                    Proc IEEE-MTS Workshop, MTS, Berkeley, CA 94702, pp 283-294.
                        (7) Towles, T.L. and Hauser (1986). ATZ - An Acoustic Telemetry System for
                        Collection of Subsurface Temperature Data from a Moored Buoy, MDS '86, Proc.                (19) Hill, W. (1988). Engineering Considerations for Underwater Remote-Sensing
                        MTS Conf. on Marine Data Systems, Marine Tech. Soc., Wash. D.C., pp 178-181.                Instruments, rbid, pp 325-329.
                        (8) Cronan, P.H. and Gonsalves (19i33). ENDECO Type 1033 Directional Wave &                 (20) Bowers, G. and Lanza (1986). Data Telemetry System for Wide Array Tem-
                        Current Telemetry System, Proc 1983 Symposium on Buoy Technology, pp 292-298.               perature Sensing, MDS '86, pp 216-220.

                        (9) Jacobsen, H.P., Vestgard and Knudsen (1982). Acoustic Control System, Oceans            (21) Backes, J.L., Bell and Miller (1983). Implementation of Error Detection and
                        '82, pp 106-110.                                                                            Correction Codes for Acoustic Data Telemetry, Oceans '83, pp 167-175.

                        (10) Garrood, D.J. and Miller (1982). Acoustic Telemetry for Underwater Control,            (22) Fisher, F.H. and Simmons (1977). Sound Absorption in Sea Water, J. Acous-
                        Oceans '82, pp 111-114.                                                                     tical Society of Amexica, 62, p.558.

                                                                                                                                                                       =.mm# frequency
                          10 Hz         20              50        100 HL        euv             300           1k-         z               5         10 kHz        20           50 kHz
                                           heavy                                                                             HAIL                                                       80
                                           SHIPPING
                                         0m-o, d,e"r,at"e                                                                                                                                   NSL
                             ......... ....... .....                                                                                   30 m/s
                                                                                                                              qc-       N                                            - 70dB
                                                                                                                                       20                            light' rain
                                                                                                              I Whr                                                % 113,15 kHz peak
                                           light                                                                                       1

                                                                                                                                       10
                                                                                                                                                               ro.0.51 in/hr%%,,
                                                                                                                                                                                        60
                                                                                                                                                                         'RAIN
                                                                                                                                                               0.1
                                                                                                              0.1 ln1hr-

                                                                                                                                                                                        50
                                                                                                                                                            A
                                                                                                                                                                   IN10
                                                                                                                                                                           15
                                                                                                               L,nlhr

                                                                                                                                                                                     -40
                                                                                                              0.0 in1hr.
                               NOISE SPECTRAL LEVEL                                                                                             1 M -S             ---12                30
                               typical curves as compiled by Sea Data                                                                      1 kt)
                                                                                                                                        5

                                OdB     I pPa /Hz Y2
                                                                                                                                                       e n s Nit i v i t \y
                                                                                                                                                                                        20

                                                                                                              282

                                     SIGNAL PROCESSING USING SPREADSHEET SOFTWARE

                                                    Ronald L. Spooner

                                                  Marymount University
                                                  2870 North Glebe Road
                                                Arlington, Virginia 22207

                              ABSTRACT                                          FIGURE 1

             This paper   demonstrates that LOTUS 123, a           B8: @RAND+@RAND+@RAND+@RAND+@RAND
             trademark    of   the    LOTUS    Development
             Company, is an extremely useful tool for
             active sonar signal design. Three features                    A         B        C
             of LOTUS   are important to the effort: (1)           1   SIN WAVE PLUS NOISE
             the lotus random number generator, (2) the            2
             LOTUS cell relational copy feature and (3)            3
             the excellent LOTUS graphing capabilities.            4      DATA     NOISE
                                                                   5    SAMPLE     DATA
             The   paper  demonstrates   that Spreadsheet          6    NUMBER   SAMPLE
             Software is a powerful tool not only for              7
             accounting   and  business,   but  also    for        8           1 0.774688
             sonar signal processing.                              -

                                                               The  result is a simulation of a white
                                                               gaussian noise waveform of as many noise
                           i. INTRODUCTION                     samples as we desire. The first 13 samples
                                                               of a 200 sample noise waveform are shown
             The purpose of this paper is to show the          in column B of Figure 2. The full noise
             usefulness of Spreadsheet Software for            wavoform is plotted in Figure 3 using
             sonar signal processing. The steps consist        LOTUS graphics.
             of simulating a random noise waveform,
             constructing a signal design, and then
             performing correlation processing to find                          FIGURE 2
             and evaluate performance.
                                                                   B8: @RAND+@RAND+@RAND+@RAND+@RAND-
                        2. THE NOISE WAVEFORM

             We create an independent (approximately)                      A         B        C
             gaussian noise waveform using the LOTUS               I   SIN WAVE PLUS NOISE
             LaRAND function which generates a uniform             2
             random number between zero and one. By                3
             summing twelve of these random numbers and            4      DATA     NOISE
             normalizing, we can create a zero mean                5    SAMPLE     DATA
             unit   variance (approximately) gaussian              6    NUMBER   SAMPLE
             random variable (1).                                  7
                                                                   8           1-0.32606
             Figure I shows the procedure for the first            9           2-2.17980
             noise sample data cell where the samples              10          3-1.42729
             are numbered down column A and the noise              11          40.378947
             data samples are in column B.                         12          52.122943
                                                                   13          60.026867
             If we had to type the equation in cell B8             14          70.212809
             for each of the noise data samples the                Is          8-0.76279
             process would be prohibitively laborious.             16          90.910396
             Fortunately, however, all we have to do is            17        10 -0.28609
             to use the LOTUS copy feature and copy the            18        11 2.127792
             function to the desired number of noise               19        12 0.180714
             sample cells down column B.                           20        13 1.535139
                                                                   19-Jul-88   01:2S PM

                                             CH2585-8/88/0000-283 $1 @1988 IEEE

                                      FIGURE 3                           the    remaining   signal    sample    ce I I s. For
                          _____IIOIIE WAVEFORM                           this example we     used    two   cycles    of the
                                                                         sine wave as shown in Figure 5. Also we
                     3-                                                  included a variable amplitude gain ($T$2)
                                                                         so that the signal-to-noise ratio can be
                     2-                                                  easily changed.

                                                                                               FIGURE 5
                                                                                               SIGNAL WAVEFORM
                 n
                     D -                                                        @4

                                                                                0.6

                                                                                0.2
                       . . ........................ . ..................
                       G                    100        150       20D
                                        DATA SAMPLE                         -0.2
                                                                            --0.4
                 Note that   non-white noise can be produced                __O.G
                 by defining relationships between samples,                 -0.0-
                 such as a single step markov process, and                      -Ij
                 then copying the relationship- down the                    --@.21
                                                                                .4
                 noise sample column.
                                                                                0          50       100       ISO         200
                           3. THE SIGNAL WAVEFORM                                               DATA SAMPLE

                 Generation 'of the signal depends on the
                 desired signal waveshape. For our first                        4. THE SIGNAL + NOISE WAVEFORM
                 example we use a sine wave. The signal
                 samples are placed down column C and in                 Once   the noise and signal wavforms have
                 time sequence are placed in the center of               been generated they may be summed in
                 the noise waveform samples.The functional               column D. The result is plotted in Figure
                 form of the sine wave is shown in Figure                6 for a signal-to-noise ratio (SNR) of
                 4.                                                      OdB.

                                                                                               FIGURE 6
                                    FIGURE   4                                             SIGNAL + NOISE WAVFFORM SNR-OdB

                    C83:' +$T$2*@SIN(@Pl*(A83-$A$83)/iO)                        3

                              A                     C                           2
                    I    SIN WAVE PLUS NOISE                             W
                    2
                    3
                                                                         1      0
                    4       DATA      NOISE     SIN WAVE
                    5      SAMPLE     DATA      SIGNAL
                    6      NUMBER    SAMPLE     SAMPLE
                    7                                                           -2
                    83            76 0.621254          0
                    84            77 -1. 89134  1. 3108SO
                    85            78 -0.79248   2.493385                        0         so        100       ISO         2130
                    86            79 -1.60264   3.431850                                        DATA SAMPLE
                    87            80 -1.06422   4.034381
                    88            81 0.178056      4.242                 S. CROSS-CORRELATION PROCESSING
                    89            82 -1.50562   4.034381
                    90            83 0.097219   3.431850                 Cross-correlation processing of the signal
                    91            84 1.091418   2.49338S                 and signal    plus noise     is the process of:
                    9-,           85 -1.94063   1.310850                 (1)    overlaying   the   two   waveforms,      (2)
                    93            86 -0.50615   1.4E-18                  multiplying     the   samples,    (3) adding    the
                    94            87 0.391116   -1.31085                 products    (integrating),     (4)   dumping    the
                    95            88 0.316510   -2.49338                 result as a single number and (4) shifting
                    19-Jul-88     01:29 PM                              @one sample and repeating the process.

                 The function     was   created   by   typing the        Starting with the first       noise sample, the
                 equation in cell C83 and then copying to                crosscorrelation function is typed in the

                                                                   284

              corresponding cell of column E as shown in                               FIGURE 9
              Figure 7. Typing this function    is an error                         CORRELATION OUTPUT- SNR-OdB
              prone    process  which   if  it  had   to   be            50 -_                                7
              repeated for each data cell       would prove              40-
              Spreadsheet Software useless for signal
              processing analysis.                                       30-

                                                                         20-

                                FIGURE 7                                 1

                    E8: +$C$83*D8+$C$84*D9+$C$85*DI04
                                                                         -10

                            A         E         F                        -20
                    1   SIN WAVE                                         -;R)

                                                                         -40
                    3                                                    0        50       100       150        200
                    4      DATA       SIGNAL AND                                        DATA SAMPLE
                    S    SAMPLE   SIGNAL PLUS NOISE
                    6    NUMBER       CORRELATION
                    7                                             6. SIGNAL-TO-NOISE RATIO VARIATIONS
                    a           1 0.771082
                                                                  T-he effects     of   signal-to-noise ratio
                                                                  changes on processing performance may be
              However,  because   of  the   relational copy       examined by simply    varying   the amplitude
              features  of  the software    we only have to       on the   sine wave   signal. Figure 10 shows
              type the  function once and   then   just copy      the signal plus' noise   waveform and Figure
              it  for   the    rest of the  data cells., The      11 shows   the crosscarrelation results for
              software    automatically      indexes     each     a -3dB SNR.
              function by one sample cell as shown in
              Figure 8. (Note     that  the   use  of  the $                          FIGURE 10
                                                                                   SIGNAL NOISE ORM SNR--34B
              prevents   the   signal waveform  values   from            3
              being indexed).

                                                                         2

                                FIGURE 8

                  E9: +$C$83*Dg+$C$84*DIO+$C$85*Dll-

                                                                         a-

                            A         E         F
                  I    SIN WAVE
                  2
                  3
                  4      DATA        SIGNAL AND
                  5     SAMPLE    SIGNAL PLUS NOISE
                                                                                                               200
                  6     NUMBER       CORRELATION                                           DO
                  7            0                                                       DATA SAMPLE
                  8            1  2.867470
                  9            2  1.646376                                           FIGURE 11
                  10           3  0.644179                                          CORRELA'nONq.SNR--3d5
                  11           4  -0.34991
                  12           5  -0.62400                               141
                  13           6  -0.43120                               1
                  14           7  0.092879
                  15           8  0.797706
                  16           9  1.292642
                  17           10 1.487631                               2-
                  18           11 1.662129
                  19           12 1.690333
                  20           13 1.700339
                  19-Jul-88    03:26 PM

              The crosscorrelation processing results                 -121
              for the sine wave example with OdB SNR are              -14
              shown  in Figure 9.                                        0       60       100       1;0        200
                                                                                       DATA SAMPU
                                                                         0
                                                                         2
                                                                         4

                                                                         0

                                                              285

                                          7. SIGNAL WAVESHAPE VARIATIONS                                                                                                                FIGURE 14
                                                                                                                                                                                   CHIRP CORRELATIOMSM-Uo
                              The effects of signal waveshape variations                                                                                2a
                              (increased time-bandwidth products) can be                                                                                20
                              considered within                               the            overall system
                              simulation structure by                                        simply changing                                            la-
                              the signal waveshape. For                                      example, Figure
                              12 shows a chirp sine wave                                     substituted for                                            10-
                              the conventional sine wave                                     of the previous
                              example.                                                                                                                  a
                                                                                                                                             IL

                                                                                                                                                        0
                                                                       FIGURE 12
                                                                     CHIRP SIGNAL WAYEFORM

                                          a's-
                                          0.8-                                                                                                       -10
                                          0.7-
                                          0.0                                                                                                        -15    ................ ......
                                          0.5                                                                                                             0                   so                  100                  150                  200
                                          0.4 -
                                          0.3-                                                                                                                                             DATA SAMPLE
                              W           02
                                          0.1
                                          'a
                                   -0.1                                                                                                                                     9. REFERENCES
                                   -0.2
                                   -0.3
                                   -0.4                                                                                                     (1). W.              Mendenhall, Introduction to
                                   -0.5                                                                                                                 Probability and                         Statistics, Duxbury
                                   -0.7                                                                                                                 Press, 4th. ed., 1975.
                                   -0.8
                                          i.. . ......... .. . ..... .....
                                          0                  50                   100                 180                   200
                                                                          DATA SAMPLE

                              Figure 13 illustrates the signal plus
                              noise waveform for an SNR of -3dB. The
                              crossoorrelation results                                          are shown in
                              Figure 14.

                                                                       FIGURE 13
                                                                CHIRP SIGNAL + NOISE SNR--3dB
                                          3

                                          2 -

                                          I

                                          0

                                          -2

                                          -4
                                          0                   so                  100                  150                  200

                                                                           DATA SAMPLE

                                          8. CONCLUSIONS & CONTINUING WORK

                              The results presented above demonstrate
                              that Spreadsheet Software can be usefully
                              applied to sonar signal processing.

                              These results, however, pertain to the
                              noise              limited                 case            of sonar signal
                              processing. Future work is directed at the
                              more important and difficult case of what
                              to do when                          faced             with reverberation
                              iimiting noise.

                                                                                                                                    286

                        MULTIPATH REJECTION USING NARROW BEAM ACOUSTIC LINK

                                                                  L. Wu and A. Zielinski

                                              Department of Electrical and Computer Engineering
                                         University of Victoria, Victoria, BC, CANADA V8W 2Y2

                                                                                             If, is intensity of n-th multipath (in dB)
                                      ABSTRACT                                               Id is intensity of the direct path (in dB)

               Multipath suppression using narrowbeam link is dis-
               cussed. Two types of narrowbeam systems are com-                          Surface Mullipath          Surface
               pared: umbrella-type beam produced by linear axray
               and conical, searchlight-type beam produced by planar                          Recai@e
               array. Specular and non-specular reflections are consid-
               ered. It was shown that in both uses, linear array offers                    Bottom Multipath
               better performance in rejecting multipath than the pla-                                                                    Transmitter
               nar array with the same number of elements.

                                  INTRODUCTION                                               Figure 1: Multipath Structure
               The presence of multipath in underwater acoustic com-                  It has been shown [5] that the DMR increases with cen-
               munication channels is the major limitation to reliable,               tral frequency employed and ocean depth, and decreases
               high-rate data transmission needed in diverse applica-                 with the range. For this reason, high frequency, near
               tions.                                                                 vertical transmission from deep ocean is least affected by
                                                                                      the multipath. For example, vertical transmission from
               The multipath conditions can vary significantly depend-                a 200m depth encounters D21R = 28dB at frequency
               ing on sea state, ocean depth, type of bottom, sound                   f = 100kHz which drops to 15dB at f = 10kHz.
               velocity profile, transmitter-receiver configuration and               The onmidirectional transducers, smooth surfaces and 5
               their respective radiation patterns. Because of a rel-                 Mrayls bottom acoustic impedance have been assumed.
               atively high frequency carrier used for acoustic com-                  On the other hand, DMR can drop as low as 5dB for
               munication the ray theory can be applied to determine                  very shallow water (50m) and long propagation range
               the propagating paths linking a transmitter and a re-                  (1000m).
               ceiver. Shown in Figure 1 are primary possible paths                   Since multi-path signals generally arrive from an      .gular
               linking transmitter and receiver in an isospeed acous-                 directions different from that of the direct path signal,
               tic channel. The intensity of a particular multipath can
               be calculated taking into account the propagation dis-                 they can be suppressed by utilizing      suitable radiation
               tance, number of surface and bottom reflections and                    patterns at the transmitter and the receiver. Such pat-
               associated losses, and transmitting/receiving radiation                terns will consist of a narrow mainlobe and small side-
               patterns. The channel quality can be quantitatively ac-                lobes. The transmitting/receiving beams should be kept
               cessed by direct signal-to-multipath signal ratio. As-                 aligned along the direct path. Suppression of some mul-
               suming noncoherent multipath signals, this ratio (in dB)               tipath can lead to a substantial increase in the DMR
               can be expressed as [5].                                               [5]. In order to ease the beam's al     -ignment task, it is
                                                                                      also possible to employ a broadbeam transmitter and a
                                                                                      narrow beam receiver.
                               DMR          log @           1              (1)
                                                 Flo'-/10
                                                  n
               Where

                                                             CH2585-8/88/0000-287 $1 @1988 IEEE

                              MULTIPATH SUPPRESSION                                      The configuration shown in Figure 2b uses a relatively
                                                                                         broad conical fixed transmitting beam while the steer-
                                                       Receiver                          able receiving beam is narrow [3]. The beam alignment
                                                                                         for this configuration is less complicated. It will be
                                                                                         demonstrated that the system performance is not criti-
                                                                                         cally dependent on a transmitting bearnwidth.

                                                                                         Shown in Figure 2c is a steerable umbrella-type receiv-
                                                                                         ing beam, produced by a vertically suspended linear ar-
                                                                                         ray. Beam alignment and tracking for this configuration
                                                                                         is particularly simple. Subsequently it will be assumed
                                                                                         that a fixed, relatively broad conical transmitting beam
                                                                                         and steerable narrow (searchlight or umbrella-type) re-
                                Transmitter     (a)                                      ceiving beam are utilized.
                                                       Receiver                          The multipath signals can be admitted to the receiver
                                                                                         through the main lobe beam or through the sidelobes of
                                                                                         the radiation pattern. Sidelobe levels can be controlled
                                                                                         by proper weighting coefficients applied to each element
                                                                                         of the array. The Dolph-Chebyshev weights, for exam-
                                                                                         ple, allow for theoretically arbitrary suppression of the
                                                                                         sidelobe level [4,6,71.
                                                              P
                                                                                         The multipath signal can also be admitted to the re-
                                                                                         ceiver together with the direct-path signal through the
                                                                                         properly steered mainlobe. This will occur whenever
                                Transmitter                                              the difference between the angles of arrival of the di-
                                                (b)                                      rect and multipath signals is less than the bearnwidth
                                                        Receiver                         of the mainlobe. In order to reduce the probability of
                                                                                         this occurrence, the mainlobe should be as narrow as
                                                                                         possible.

                                                                                                    SPECULAR REFLECTIONS

                                                              L                          Let us assume that the multipath is caused by speculax
                                                                                         reflections from smooth bottom and ocean surfaces. In
                                                                                         such a situation, angles Op and f1L indicated in Figure
                                 Tra  nsmitIter                                          2b and 2c provide the correct measure of array ability
                                                                                         to reject multipath signals which might otherwise be
                                                W                                        admitted through the main lobe.
                        Figure 2: Configurations of acoustic beams                       Shown in Figure 3 is the ratio flP/nL vs the pointing
                                                                                         angle (off vertical) for arrays employing the same num-
                                                                                         ber of elements N separated by a half wavelength. 3dB
                    Three basic beam configurations depicted in Figure 2                 bearnwidth has been assumed for calculations. It can be
                    a) b) and c) are considered. Shown in Figure 2a are                  seen that the linear array has a greater capacity of mul-
                    narrow searchlight-type beams for both transmitter and               tipath suppression than the planar array for practically
                    receiver [2]. Both beam are produced     by steerable mill-          all ranges of pointing angles and array sizes.
                    tielement arrays. Although the configuration offers the
                    best rejection of ambient noise, a relatively complex                Subsequently, we will consider a situation where a multi-
                    scheme is required to steer and to track the beams. Ad-              path signal is caused by reflections from rough surfaces.
                    ditional difficulties arise from the fact that the steerable
                    transmitting beam must be able to handle the neces-                          NONSPECULAR REFLECTIONS
                    sary transmission power. This necessitates a number of
                    power amplifiers driving each element of the transmit-
                    ting array.                                                          To simplify the analysis we will assume zero sensitivity

                                                                                   288

              of the receiving array in the upper hemisphere. This                  Since the receiving array is directional, only a certain
              will allow us to neglect multipath arriving directly from             amount of scattered power will be admitted to the sys-
              the ocean surface. The ocean surface is assumed rough                 tem. This amount can be calculated by considering an
              while the bottom will be considered to be a perfect re-               intersection of the receiving beam (conical or.umbrella-
              flection as indicated in Figure 1. For such a situation               type) and the image surface as shown in Figure 5.
              the scattering from the sea surface can be represented
              by an image source as illustrated in Figure 4.                             umbralla                    S1
                                                                                         beam                                            image
                                                                                                                                         source

                                                                                                                             S 2

                                                                                                                             X

                                                                                                                                         C
                                                                                                                                          onical
                                       &Tray size                                                                                        beam

                                  N  64 49 36 25 Jr,

                C:

                C:
                                                                                        Figure 5: Intersection of the Receiving Beam
                                                                                                    and the Image Scattering Surface
                                                                                    The total mean power received from the image surface
                                                                                    is then obtained

                     0.         20*       40*        60*         so*
                                     Beam pointing angle                                P,. = 8 - f f G(O, 0, x, y, Oi, 8i) ds; i = 1, 2         (2)
               Figure 3: Compaxison of beamwidths for planar                                         'i
                            and linear arrays                                       where G (0, 0, x, y, 0j, Oj) is the intensity distribution func-
                                     Scattedng Area                                 tion of the mean power scattered in the direction (0, 0)
                                                                                    from each source point (X, Y) for a given incident an-
                    _.: . . . . . . . . . . . .
                                                                                    gle (0i, 60, si is the shaded region as shown in Figure 5,
                   ii:            is
                           ... ......
                                                                                    and    is transmission loss along surface-bottom-receiver
                                                                                    path.

                                                                                    The intensity distribution function of the scattered field
                                                                                    in various directions for a given angle of incidence has
                                                                                    been discussed in[l] For the slight surface roughness
                                                                                    (standard deviation a = O.1A) and the long correla-
                                                                                    tion distance (T = 200k here T is the distance in which
                                                                                    the spatial auto correlation coefficient C(t) drops to the
                                                                                    value e-1) only 46.8%           0.468) of the incident en-
                                                                                    ergy is reflected in the speculax direction, the remaining
                                                                                    energy is diffusely scattered in all other directions.
                                  Image Scaftedng Area
                                                                                    For rough surfaces with a = 10A and T = 200A, the
                Figure 4: Applicatio    n of Image Principle                        mean power reflected in the specular direction exceeds
                             to Rough Sea                                           37%. This means that for laxge T (gently rolling surface
             Part of the incid-ent upon surface power Pi is reflected               with long distance between hills and valleys) the spec-
             in the specular direction while the remaining power P,                 ular direction remains privileged even if the surface is
             is diffusely scattered in all directions as given by. [1]:             very rough.
                                                                                    We will compare the average multipath power received
                           P. = (1 - ii)pi      (1 - P)apt                          from the image surface by the linear array Pg and the
                                                                                    planar array P@, that is
             where Pt is transmitted power                                                       P,1    f f., G(O  0, x, y, Oi, Oi) da
                     a is transmission loss from the projector                                                                                (3)
                       to the surface                                                            PIT    f L2 G (0, 0, x, y, Oi, Oi) ds
                                  IV = 60 3. 2i M

             and       is the variance of the scattering coefficient p.

                                                                               289

                      For simplicity we will assume that the intensity distri-                                  CONCLUSIONS
                      .bution function G(-) is uniform on the image surface,
                      and therefore                                                         Reduction of multipath interference in a shallow water
                      P't      S,                                                           channel has been discussed. It is suggested that a ver-
                      P',      S2                                                           tical suspended linear array is a useful tool for shallow
                                                                                            water, middle range acoustic communications and its
                           2 tan(%L1                                                        performance is superior to that of a planax array with
                                   2 1 sin 200                                              the same number of elements.

                                @50 tan  2Oo tan 2     - 9 tan4 0. - tan 4
                                                   22'_                      20)                         ACKNOWLEDGEMENTS
                      x tan-'                5 tan2 00 - tanZ
                                                              CA21
                                                 Nrlor __r2                                 This work was supported by Natural Sciences and En-
                               sin 28o X tan-'                                              gineering Research Council of Canada Operating Grant
                           02
                            rp                         5 - r                  (4)           A6830.

                      where Ot and Op are the beamwidth of the linear and
                      planax array, respectively, 00 is the steering angle, -yt is
                      the beamwidth of transmitter, and                                     References

                                                   tan 2(a)                                  [11  Berkmann, P. and A. Spizzichino, The Scatter-
                                                        2
                                             r      tan 200                      (5)              ing of Electromagnetic Waves from Rough Surface,
                                                                                                  Macmillan, New York, 1963, pp. 137-146.
                                                                               120'          [21  Catipovic, J., A. B. Baggeroer, K. Van Der Heyat
                              N   1 x64, 8x8                     100*   110,                      and D. Koelsch, Design and Performance Analysis
                                                          001                                     of a Digital Telemetry System for the Short Range
                                                                                                  Underwater Channel, IEEE J. of Oceanic Engineer-
                                           70*                                                    ing, Vol. OE-9, No. 4, Oct. 1984, pp. @242-252.
                                                                                             [31 -Collins, J. S., and K. H. V. Booth, Simulation of
                                                                                                  Multipath Channels Terminated by Narrow Beam
                                                                                                  Non-parametric Transducers, Fourth International
                                                                                                  Symposium on Unmanned Untethered Submersible
                                                                                                  Technology, June 1985, pp. 124-139.
                                                                                             [4]  Dolph, C. L., A Current Distribution of Broadside
                                                                                                  Arrays which Optimizes the Relationship between-
                                                                                                  Beamwidth and Side Lobe Levels, Pro*c. I.R.E.,
                        20*           30*            40*           so*           60,              June 1946, pp. 335-348; May 1947, pp. 489-492.
                                          Beam pointing angle                                [51  :Howse, D., and A. Zielinski, Multipath Modelling
                      Figure 6: Comparison of Multipath Rejection for                             for Acoustic Communication, in Proc. Oceans '82,
                                  Planar and linear axrays                                        pp. 217-222.
                      The ratio PelPp changes only slightly when the num-                    [6]  Stegen,           R.          J.,            Excitation
                      ber of elements N varies. Figure 6 shows the perfor-                        Coefficients and Beamwidth of Tschebyscheff Ar-
                      mance of two types of arrays; lineax and planar with                        rays, Proc. I.R.E., pp. 1671-1674, Nov. 1953.
                      the same number of elementn (N = 1 x 64 and 8 x 8)
                      separated by A/2. We can see that. at steering angle                   [7)  Zielinski, A., Matrix Formulation for Dolph-
                      Oo = 45' and for transmitting beamwidth -Yt = 100* lin-                     Chebyshev Beamforming, Proc. of IEEE, vol. 74,
                      ear array gives 7.4dB improvement over planar array in                      no. 12, Dec. 1986, pp. 1799-1800.
                      rejecting the multipath.

                                                                                     290

                                                  COMPENSATION OF VERTICAL DISPLACEMENT COMPONENTS

                                                                 IN MARINE SEISMIC APPLICATIONS

                                                         USING THE COUPLED HEAVE AND PITCH MODEL

                                                                         FERIAL EL-HAWARY

                                                   TECHNICAL UNIVERSITY OF NOVA SCOTIA P.O.BOX 1000,
                                                            HALIFAX, NOVA SCOTIA, CANADA B3J 2X4

                                                                                             The motion's effects appear on the reflection records along
                                                                                        the  ship track as additional undulations of the sea floor and of
                                                                                        the  sub-bottom reflectors. When pitching is neglected this is
                                            ABSTRACT                                    commonly called heave effects. Removal of the vertical
                     In underwater seismic exploration   using acoustic arrays the      displacement component is an important preprocessing task for
                 aim is to determine the structure of the underwater layered            improving displays of the raw and filtered reflection data, for
                 media in terms of significant geometric and physical properties        extracting media parameters such as reflection coefficients
                 . In this method a towed body is employed to house both                and reflector depths. Partial removal of these effects can be
                 acoustic energy source and the receiver array. The reflection          done by use of estimates of the vertical source motions from
                 records received using this method, contain, undesirable noise         hydrostatic pressure and motion sensors to delay or advance
                 components due to the vertical motion of the towed body. A             the pulse firing instants relative to a clock pulse reference.
                 major portion of this component is compensated for      usinj the      This is done such that the source- bottom- sensor pulse travel
                 well known heave compensation technique. The intent        0           time corresponds to that of a source and sensor located at a
                                                                                this    constant depth relative to the mean water surface level.
                 paper is to address the issue of incorporating a more realistic
                 model for the vertical motions involved.                                    Marine hydrodynamics references such as Bhattacharya [8],
                     The towed body experiences six different kinds of motion,          Price and Bishops [9], and McCormick [10] discuss details of
                 three of which are linear and the other three are rotational           modeling the vertical displacement hydrodynamics. We high-
                                                                                        light a model of the process, which is designed for subsequent
                 about the three principal axes. None of the motions occur              Kalman filtering implementation. The model is derived in
                 singly, as they are all coupled in a manner that depends on
                 current and wave directions. For the purposes of this paper,           transfer function form, and is then cast in state-space form.
                 the relevant motions are in the vertical direction which is            The model of the vertical displacement dynamics is consistent
                 controlled by both heave and pitch effects. We highlight a             with those found in the area of hydrodynamics. Spectral
                 model of the process, which is designed for subsequent                 analysis of field records provides the basis for modeling the
                 Kalman filtering implementation. The model is introduced in            process via the transfer function, and parameter estimation
                 conventional form, and is then cast in state-space form.               techniques.
                 Spectral analysis of field records provides the basis for                   This model provides the basis for formulating the vertical
                 modeling the process via the transfer function, and parameter          displacement extraction problem as one of Kalman filtering in
                 estimation. techniques. The paper also discusses issues in             the theory of optimal linear estimation. The design of the
                 preprocessing requirements as a result of incorporating the            Kalman filter enables reducing the residual vertical dis-
                 effects of the pitch component.                                        placement effects, i.e., for delaying and advancing the
                                                                                        recording trigger on successive firings so as to effect a
                                       1. INTRODUCTION                                  smoothing or removal of such undulations. The filtering can
                                                                                        be applied to post-experiment data records, or preferably in a
                    Acoustic arrays are employed in underwater seismic                  real-time mode during acquisition of the reflection responses.
                 exploration to determine the structure of the layered media in         The Kalman filter applications are well known for some
                 terms of significant properties that aid in the exploration task       different physical situations as reported in Gelb [11] and
                 of identifying hydrocarbon formations. Conventional acoustic           Meditch [12]. Heave Component Extraction details have been
                 techniques have gained increasing use over the past several            presented in [13]. The heave motion is also of interest in buoy
                 years for marine layer identification@ and classification of           wave data analysis [14].
                 sediments. Mendel [1] gives a, tutorial introduction to the                 Compensation for source vertical displacement using
                 subject area, while [2-41 are classical treatments dealing with        Kalman filtering involves two steps. In the first a model of the
                 the theoretical foundations of the estimation process. An              vertical displacement phenomenon is obtained on the basis of
                 approach to extracting the subsurface features using a system          available data. The type of model as well as its order are
                 theoretic treatment can be found in [5]. Using the enhanced            important considerations. In early applications [15] a linear
                 acoustic signals for extracting information about the media            second order model of the heave phenomenon            was found
                 properties has also been treated in [6-7].                             satisfactory. In this step the estimation of the model
                    A deep towed array of acousti           signal sources and          parameters is an important aspect. The resulting estimation
                 hydrophone receivers are used in conducting                            software uses an iterative procedure [16]. Once a      model and
                                                                  shallow marine
                 seismic explorations. Each source imparts energy to the water          its parameters have been identified, the process      of Kalman
                 and underlying media. The source signal then undergoes                 filtering is performed. Two versions exist. In the early
                 multiple transmissions and reflections at the layers' boundaries.      implementation conventional Kalman filtering (14-15] is used
                 The towed body experiences six different kinds of motion,              satisfactorily in a majority of cases. Kalman filtering theory
                 three of which are linear and the other three are rotational           and parallel Kalman filters are applied to the exploration
                 about the three principal axes. None of the motions occur              problem using a second order model in a recent paper [17].
                 singly, as they are all coupled in a manner that depends on            Particular emphasis is given to the multi-receiver case as an
                 current and wave directions. These dynamics cause vertical             important application of array processing methodology. Parallel
                 motions of the source and sensor which are controlled by both          Kalman filtering is designed to take advantage of systolic
                 heave and pitch effects.                                               array implementation. investigations concerning higher order
                   These vertical components have the effect of a varying               model implementations are of current interest [18].
                 acoustic wave travel path to the sea floor and to the                       The paper discusses issues in preprocessing requirements as
                 sub-bottom reflectors between successive pings of the source.          a result of incorporating the effects of the pitch component in
                                                                                        compensating for the vertical displacements.

                                                              CH2585-8/88/0000- 291      $1 @1988 IEEE

                         2. VERTICAL DISPLACEMENT MOTION MODELING                                          (m -,- a .) 2 + b;@ + cz + A + e6 + hO       F(t)         (3)

                         The towed body experiences six different kinds of motion,                Here we have:
                    three of which are translational (linear), and the other three                     m=  mass of towed body.
                    are rotational about the three principal axes. The direction of
                    travel is taken as the x-axis, and the motion in this direction                    a. =added mass
                    is called the surge . The translational motion along the y-axis                    b= hydrodynamic damping force associated with the
                    is termed the sway, and the vertical or z-axis translational                           heave velocity.
                    motion is known as the heave. The rotational motion about the
                    x-axis is referred to as the roll, while that about the y-axis is                  c=F heave restoring force associated with a unit heave
                    the pitch, and finally the term yaw refers to motion about the                         displacement z(t).
                    z-axis.                                                                            d=  moment of inertia coefficient associated with the
                         None of the motions occurs singly, as they are coupled in                         angular pitch acceleration's effect on the vertical
                    a way that depends on the wave and current directions.                                 motion's force balance.
                    Decoupling the motions simplifies the analysis and is useful                       e= hydrodynamic damping coefficient associated with the
                    when motion in a plane is of interest. For the purposes of this                        angular pitch velocity's effect on the vertical motion's
                    study the relevant motion is in the vertical direction which is                        force balance.
                    controlled by heave and pitch. In this section we outline the
                    various models available for representing the vertical dis-                        h=  hydrodynamic restoring coefficient associated with the
                    placement components.                                                                  angular pitch's effect on the vertical motion's force
                    Model for Heave Qn!L                                                                   balance.
                         There are four kinds of forces acting on a submerged body                  F(t)=  exciting force in the heave direction.
                    in the heave direction.
                    I- Inertial force, given as the product of the virtual mass                        For the pitching dynamics, we have:
                    (body's mass plus the added mass term) and the vertical
                    acceleration.                                                                       (I,Y+AYY)6+B6+C0+D2+E_@+Hz=M(t) (4)
                    2- Damping force, given as the product of the damping                         Here we  define:
                    constant and the vertical velocity. This force always resists the
                    motion.                                                                            I.,= Principal axis moment of inertia of towed body.
                    3- Restoring force, which tends to bring the body back to its                   AYY = added principal axis moment of inertia of towed
                    equilibrium position and is given as the product of restoring or                       body.
                    spring constant and the vertical displacement.                                     B=  hydrodynamic damping torque associated with the
                    4- Exciting force which acts on the body. This is an unknown                           pitch velocity.
                    random function of time.                                                           C=  Pitch restoring torque associated with a unit pitch.
                         The heave-only model is a second order linear time                            D=  Mass coefficient associated with the heave's effect on
                    invariant system. This type of model has been widely accepted                          the angular torque balance.
                    to reasonably represent the vertical displacement dynamics of
                    the towed body.                                                                    E= hydrodynamic damping coefficient associated with the
                                                                                                           heave velocity's effect     on the angular pitch torque
                    Model for Pitching QILIL                                                               balance.
                         A submerged body         will experience a pitching motion                    H= hydrodynamic restoring coefficient associated with the
                    under the effect of four categories of moments, which are                              heave effect on the angular pitch torque balance.
                    similar to forces acting in the heave-only case.
                    I- Inertial moment, given as the, product of the virtual mass                   M(t)= exciting moment in the pitch direction.
                    moment of inertia (body's mass moment of inertia plus the                          The various coefficients in the hydrodynamic model are
                    added mass moment of inertia term) and the angular pitching                   evaluated either experimentally or using strip theory results
                    acceleration.                                                                 [9]. The next section treats the problem of developing a state
                                                                                                  space model of the dynamic vertical displacement process of
                    2- Damping      moment, given as the product of the damping                   the towed body.
                    moment coefficient and the angular pitching velocity. This
                    moment always resists the motion.                                               3. VERTICAL DISPLACEMENT STATE SPACE MODEL
                    3- Restorin$ moment, which tends to bring the body back to
                    its equilibrium position and is given as the product of                            Equations (3) and (4) can be manipulated to obtain a state
                    restoring or spring moment coefficient and the angular pitch.                 space model by defining the following state variables:
                    4- Exciting moment which acts on the body. This is an                                                         IX, = Z
                    unknown random function of time.
                         The pitch-only model is a second order linear time
                    invariant system.                                                                                             X2=0
                    Model for Counled Heave and EiJ&                                                                              X-3
                         Starting with a heave-only perspective, one can stipulate
                    that pitching will add a component to the vertical position at                                                X,=6
                    any point on the submersed body. The vertical position zP of
                    strip at point P which is located at a distance @ from the
                    body's center of gravity is given by:                                              As a result we have:
                                               z P = z - @ sin 0                          1                                       -@ , = X3                          (5)

                    For small pitch angle 0, we have:                                                                             -)@2 m X4                          (6)
                                                 Z, = z                                  (2)      Equations (3) and (4) are now written as:
                         Two general dynamic equations of motion in z and 0 can                   (m,aje,+bX,+cX, +d)@,"X4+hx,                           F(t)        (7)
                    .be written. The equations are coupled due to the interaction
                    between the two variables. For the heave dynamics, we have:
                                                                                                  (1YY + Ayy)X4 + BX4 + CX2 + D,@, + Ex, + Hx, = M(tX8)

                                                                                              292

                    Equations (7) and (8) couple the derivatives of the state                          4. COMPENSATION USING KALMAN FILTERING
               variables and further manipulations are required to obtain a
               canonical state space form of the heave and pitch model.                               The vertical displacement motion model of Eq. (14), can
                    It is convenient to define the state vector X using the                      be written in discrete state space form as:
               partitioned form:                                                                      x(k + I ) = 0(k + I , k)x(k) + T(k + I , k)w(k)                (16)
                                              X =    X 12                        (9-1)                The state transition matrix 0 (k+l,k) and the matrix r
                                                     IX341                                       (k+l,k) are constants and we therefore write:
               Here we have:                                                                                            x(k + I       Ox(k) + Fw(k)                  (17)
                                                                                 (9-2)                The input sequence w(k) is assumed to be a Gaussian
                                              X 12     X     I                                   white sequence with zero mean and a covariance matrix Q (k),
                                                     [X2                                         being positive semi-definite. The initial state is assumed to be
                                                                                                 a Gaussian random vector with zero mean and known
                                                                                                 covariance matrix P (0). It is further assumed that w(k) is
                                              X34    [Xj                         (9-3)           independent of x(O). The record of vertical displacement
                                                       X,                                        component is assumed to be the basis for the measurement
                                                                                                 model given by:
                                                                                                                   zp(k + I        Hx(k + I ) + v(k + 1              (18)
                    We now define the following matrices:
                                                                                                      The measurement error sequence v is assumed to be
                                M34         rn+ a.             d                 10 _ I          Gaussian with zero mean and a covariance matrix R(k).
                                               D             IYY + AYY                                Assume that measurements z(l), z(2), ..., z(j) are available,
                                                                                                 from which we like to estimate x(k), denoted by x (kjj). In
                                                                                                 filtering we have j=k, and we therefore wish to ind x (k1k).
                                            N        c       h]                (10-2)            We utilize the standard predictor-corrector form of a Kalman
                                                     H       C                                   filter given by:
                                            N14      b       e                 (10-3)            PREDICTOR
                                                     E       B                                        In the predictor stage we obtain a prediction of the state
               As a result, we write equations (7) and (8) in the vector form:                   based on the previous optimal estimate:
                               M 34'@ 34 + N 12X 12 + N34X*34 @ Fm               I I - 1                                   X'(_ ) = Ok- I X k- I (+)                 (19)
               Here we have                                                                           In addition, we obtain for the error covariance matrix
                                                     [ F ]                                                                                       )OT_,
                                              Fm=      M                       (11-2)                                    PJ1         0 k- I P J+     k               (20)
                    Equation (11-1), can be rewritten as:
                                 '@34       1 X 12 + '4 2 X34 ' M -IF          (12-1)            CORRECTOR
                                 -                               34
               Equations (5) and (6) are now written as:                                         In the corrector stage we obtain an updated state estimate
                                        i
                                               '@ 12 = X34                     (12-2)                            Xk(+) = Xk(-) + Kk(yk - HkXk(-))                    (21)

               Equations (12-1) and (12-2) express the derivatives of the
               states explicitly in terms of the state.                                               In addition,we obtain an update of the covariance matrix
               In equation (12-1) we have defined:                                               as:
                                            A, = -M341 N 12                    (13-1)                                   Pk(+) = (I - KkH@)PJ_)                       (22)
                                            A2 = _M3" N34                      (13-2)                 Here K is the Kalman gain matrix given by:
                    We now combine          equations (12-1) and (12-2) into the                                                 T    @:p@'(_)HT
               single state space equation model given by:                                                     Kk = P,(-)Hk [H                     k + Rk]           (23)
                                                  Ax + Gw
                                                                                    (14)
                                                                                                 We note here that adopting a         higher order    model to represent
               The matrix A is given by:                                                         the vertical displacement process involves           an increase in the
                                                                                                 order of computation required to perform the Kalman filtering
                                            A=[ 0, . Ij                             (15)         process.
                                                   A         A                                        The optimal estimate of the vertical displacement is given
               The matrix 0 is 2x2 with zero entries, and I is a unity matrix.                   according to equation (2), by:
               The effects of the excitation forces and moments are lumped                                                     ZP=Z-@o                               (24)
               into the matrix product G w. Equation (14) is the desired state
               space model.                                                                      In terms of the state variables we have:
                                                                                                                              ZP    X I - @X2                        (25)

                                                                                           293

                 We note here that we have to deal with a fourth order model              [7] Ferial, El-Hawary, and W.J. Vetter, "Event Enhancement
                 as contrasted with a second order model if one considers only                on Reflections from Subsurface Layered Media", IEEE
                 the heave dynamics. Knowledge of the value of @ representing                 Journal of Oceanic Engineering, Vol. OE-7, No. "Pp.
                 the distance of the source-receiver point from the towed                     51-58, IT82 .
                 body's center of gravity is also important.                              18] R. Bhattacharya, Dynamics of Marine Vehicles, New York
                     It is clear that implementing this compensation approach                 Wiley- Interscience, 1978
                 requires knowledge of the model parameters. In a practical
                 situation one can use a transfer function approach combined              [9] W.G.,Price, and R.E.E.Bishops, Probabilistic Theory 2f Shit)
                 with a least squares parameter estimator to arrive at the                    Dynamics , New York: Wiley-Interscience, 1974
                 required values.                                                         [10] M.E. McCormick, Ocean Engineering Wave Mechanics,
                                         5. CONCLUSIONS                                       New York: Wiley-Interscience, 1973
                                                                                          [11] @. Gelb, Applied optimal estimation, The Analytic
                                                                                              Sciences Corp., 1974.
                     In this paper we reviewed the basic problem of                       [121 J.S. Meditch, Stochastic Optimal Linear Estimation and
                 compensating for the vertical displacement effects. Here the
                 inclusion of the pitch dynamics results in two coupled second                Control, New York: McGraw-Hill, 1969
                 order equations in the heave and pitch components. The                   [13] F. El-Hawary, and W.J. Vetter, "Heave compensation of
                 conventional hydrodynamic equations were reviewed and a                      shallow marine seismic reflection records by Kalman
                 state space model for representing the vertical displacement                 filtering," presented at IEEE Oceans'81, Boston, MA,
                 dynamics was derived. The model is of the fourth order and is                September 1981
                 of a form suitable for Kalman filtering, implementation. The
                 application of a standard Kalman filter to estimate the vertical         [14] R.W. Severance, " Optimum Filtering and Smoothing of
                 displacement component on the basis of this higher order                     Buoy Wave Data% Journal gf Hydronautics, Vol. 9, pp.
                 model was also discussed in the paper.                                       69-74, April 1975.
                                                                                          [15] Ferial, El-Hawary, " Compensation for Source Heave by
                                         6.REFERENCES                                         use of Kalman Filter", IEEE Journal of Oceanic Engineer-
                                                                                              ing, Vol. OE-7, No. 2, pp. 89-96, 1982
                 [1] J.M. Mendel, "Some Modeling Problems in Reflection                   [16] Ferial, El-Hawary, " An Approach to Extract the
                     Seismology", IEEE ASSP, Vol.3, No.2, pp.4-17, April 1986                 Parameters of Source Heave Dynamics", Canadian Electri-
                 [2] E.A. Robinson, Multichannel Time atrjU Analysis with                     cal Engineering Journal, pp. 19-23, January 1987.
                     Digital Comi)uter Programs, Holden Day, San Francisco,               [17] Ferial, El-Hawary, K.M. and Ravindranath, " Application
                     1967.                                                                    of Array Processing for Parallel Linear Recursive Kalman
                                                                                              Filtering in Underwater Acoustic Exploration", Proceedings
                 [3] J.M. Mendel, Or)timal Seismic Deconvolution: An Estima-                  gf IEEE Oceans '86, Washington, D.C., Vol. 1, pp.
                     tion-Based Armroach, Academic Press, New Y            1983.                                   -
                                                                                              336-340, September 1986.
                 [4] E. A. Robinson, and T.S. Durrani, Geor)hvsical Signal                [18] Ferial, El-Hawary, and T. Richards, " Heave Response
                     Processing,Prentice- Hall, Englewood Cliffs, N.J.,1986                   Modeling using Higher Order Models', presented at the
                 [5] Ferial, El-Hawary, " An Approach to Seismic Information                  International Symposium on' Simulation and Modeling,
                     Extraction ", in Time atEipa Analysis 1 Theory and Practice              Santa Barbara, CA, May 1987.
                     !k, O.D. Anderson, J.K. Ord and EA. Robinson (editors),              [19) Ferial, EI-Hawary, " Image Analysis Methods From Sea-
                     Elsevier Science Publishers, Amsterdam, pp.223-238, 1985.                bed Reflections and Multiple Reflections           International
                 [6] Ferial, El-Hawary, and W.J. Vetter, "Spatial Parameter                   Journal gf Pattern Recognition and Artificial Intelligence,
                     Estimation for Ocean Subsurface Layered Media", Cana-                    Vol. 1, No. 2, July 1987.
                     dian Electrical Enpineering Journal, Vol.5, N0.1,pp.
                     28-31,1980

                                                                                       204

                                      PREDICTION SYSTER FUR ACOUSTIC 1011URZ FRCK OCEAN BATHYNETRY

                                                 L.C. Haines, W.W. Renner, and A.I. Eller

                                             Science Applications International Corporation
                                                          1710 Goodridge Drive
                                                         Mclean, Virginia 22102

                                  ABS'T13ACT                            The primary engineering challenge to this
                                                                        developuent effort was to balance the trade-
              A real-time capability to predict ocean bottom            offs between accuracy and execution time. In
              acoustic returns (reflections and backscatter)            the numerical progranming careful attention was
              has been developed for at-sea support of                  paid to the sequence in which acoustic param-
              acoustical ocean surveys. The systean operates            eters were calculated,. the manner in which
              on a HP-9.02o desk top ocaputer and provides              results were stored for later access, and the
              color screen displays of predicted bottom                 step sizes used for range and azimuth varia-
              reverberation as well as echoes from seamounts.           tion.
              Predictions are based on gridded archival data
              bases for bathymetry and sound speed profiles,            As part of the ccffnprcmise between resolution
              both of which may vary with location.            A        and conpitaticn time, a special dual resolution
              special dual resolution approach was devised to           approach was devised to provide a high-
              provide a high-resolution depiction of the                resolution depiction of the seamount returns in
              seamount returns in conjunction with a lower-             conjunction with a ladez-resolution presenta-
              resolution presentation of the reverberation              tion of the reverberation from the slowly
              from the slowly varying bottom features. This             varying bottom features. Separate calculations
              approach allows large ocean areas to be covered           are made for each of these contributions.
              in reasonable cmqxitaticn time.
                                                                                            APPROACH

                                                                        The prediction system consists of four parts:
                                                                        Data Bases, two sub-models ASEW and PMERB
                                INTRODUCTION                            that address the pkWsics involved, and the
                                                                        graphics output. There also are an auxiliary
              A real-time ccaputer based prediction System              bathymetric processing sub-model that prepares
              has been developed for caV&ing acoustic                   a semmft data base and a user-friendly driver
              returns from the ocean bottom.       An intended          menu routine.    These are represented in the
              application of such a system would be to                  overview flow diagram in Fig. 1. The bathy@
              provide b-t-situ support to acoustical surveys            metric data base presently used in the system
              of ocean bathymetry, seamount locations, and              is SYNBAPs, which provides bottom depth on a
              bottom materials as indicated by scattering               1/6-degree grid.
              properties. The system operates on a HP-9020
              desk top calculator and provides color screen             A.   Transmission loss
              displays of predicted bottom reverberation as
              well as echoes from seamounts. It operates in             The ptWsics in the system is addressed by two
              real time in the sense that calculations for              sub-models:    ASERr and REVERB.     The ASTRAL
              large ocean areas, covering 300 nmi in any                5@rstem for the Estimation of Radial Trans-
              direction, can be ocupleted in less than 30               mission Loss (AsEPT) is, by itself, a system
              min; thus, revised predictions can be made                for predicting acoustic transmission loss in
              during the course of a survey as ship locations           all directions from a fixed point location.
              change.    The currently operating version of             ASERT automatically extracts the needed bathy@
              this prediction system can acommiodate single             metry, bottom loss, and sound speed profiles
              ship surveys, in which the acoustic source and            along a 3600 fan of radial tracks about a
              receiving array are located essentially at the            fixed location.    The fixed angular step size
              same place, as well as multi-ship or similar              between radials may be assigned a value from 50
              configurations where source and array may be              to goo, depending on desired resolution and
              separated by a substantial distance in a so-              accuracy-
              called bistatic arrangement.         The system
              predictions are based on gridded archival data            Ttansmission loss calculations are made to
              bases for bathymetry and sound speed profiles,            support both the contribution from the low-
             -both of which my vary with location.                      resolution bathymetry as well as from the

                                                  CH2585-8/88/0000-,295 $1 @1988 IEEE

                  seancurts. For the bathymetric contribution,              missed. To overcome this problem the seamounts
                  transmission loss and propagation time to a               are extracted from the bathymetric data base
                  moving "target" point along the bottom are                and handled separately.
                  computed along each radial track by means of
                  the ASTRAL model.      The new ASTRAL version             rib address the seamounts a portion of the
                  containing CZ structure has been included here.           bathymetry data base is extracted to cover the
                  Surface contributions are cmVuted also, in a              entire area of interest. It is then filtered
                  similar way, so that they may be couPared to              with a low pass filter, and a pattern recog-
                  the bottom contributions. Transmission loss to            nition algorithm is used to extract the sea-
                  surface and bottom are modified to incorporate            mounts. Each seamount is modeled individually
                  the enexgy arrival angles as combined with the            using a set of parameters that are related to
                  appropriate angle dependence of the boundary              its target strength.     The large scale rever-
                  scattering kernels. - In order to estimate the            beration is =nputed from the low pass filtered
                  acoustic returns from sem=unts, transmission              version of the bathymetry using equally spaced
                  losses are canputed, simultaneously with the              radial sampling about the source and receiver.
                  above calculations, from the same fixed loca-             The radial estimates of the smoothly varying
                  tion to three additional "target" depths along            long range effects are then combined with the
                  each radial.     it is assumed here that an               discrete returns from seamounts. This process
                  effective depth for each seffimunt can be                 is illustrated conceptually in Fig. 2.
                  approximated by one of the three values                                        RESUIMS
                  selected.
                  For bistatic arrangements AsERr is called twice           Representative output plots of the bottom
                  with the acoustic source and then the receiving           acoustic returns from a bistatic survey
                  array occupying the appropriate fixed point               arrangement are illustrated in Figures 3 and 4.
                  location.                                                 The Output graphics are designed for display on
                                                                            the color screen of the HP--9020. By a separate
                  B.   Reverberation                                        routine they also may be redrawn in color on
                                                                            paper or transparencies by an offline pen
                  in REvERB the modified surface and bottom                 platter. Figure 3 is a black and white Xerox
                  transmission losses are used separately to                copy of a color plat from the pen plotter.
                  compute surface and bottom reverberation                  Figure 4, representing a different plot tech-
                  densities. The bottom contribution represents             nique, is a shaded black and white drawing.
                  only the portion attributed to the slowly
                  varying bathymetry.     The term reverberation            In Figure 3 the receiver is located at 50ON and
                  density is used to indicate a normalized                  1610W, which point corresponds to the center
                  reverberation resulting from a ore-second                 of the drawing. Me source is at 500 N, 1600
                  pulse, as received by an ideal beam, Ora-degree           W, directly east of the receiver. The effects
                  wide in azimuth.     The common Practice is to            of several small seamounts can be Observed.
                  describe bottom scattering by Lmnbertls law               The acoustic returns in Fig. 4, also for a
                  with a bottom scattering coefficient of -27               Pacific location, correspond to a source at 390
                  dB/sq yd and surface scattering by the Chapman--          N, 1280 W and a receiver 10 due west.          The
                  Harris results. The seamoant contributions are            receiver is located at the origin of the plot.
                  handjLed as distinct echoes from each of the              The drawing here. shows returns coming from the
                  seamounts.                                                Mendocino escarpment, running east and west,
                                                                            north of the receiver. (This work was jointly
                  The ambient noise field may be ccuputed by the            sponsored by the U.S. Naval Ocean Research and
                  Ambient Noise DirectlGrAlity Estimation System            Develcpnent Activity and by the U.S. Office of
                  (ANDES), which also is a part of the Prediction           Naval Research.)
                  system, using its customary shipping density
                  and errvirormiental acoustic data base.    Ambient
                  noise and surface returns are carputed    so that
                  one can identify tames when the bottom     returns
                  dominate the total received field.

                  C.   Rationale for Seamount Approach

                  Programing decisions were driven by the
                  objective to achieve reasonable accuracy within
                  a run time consistent with at-sea applications-
                  If there were no limitations an run time and
                  core storage space, then calculations could be
                  made along as many equally-spaced radials, from
                  source and receiver, as needed to include
                  seamounts. For practical reasons, however, the
                  least angular spacing allowed, at least at
                  present, is 50, and for this spacing most
                  seamounts would fall between radials and be

                                                                      296

                                                                                            ES                    BATHYMETRY PROCESSOR                                                                      BOTTOM RE-VERBERATION DENSITY

                                                                                                                  LOW PASS FILTERED
                                                                                 ASERT                                     BATHYMETRY

                                                                                                                              E;;..'T                                                                                                                                       loll        11

                                                                                                                                                                                             10     -

                                                                      F-RAPHIC OUTPUTS
                                                                                                                                                                                                                                                                    oil

                                                       FIG. 1. FIA)W DIAGRAM OF
                                                                                    PREDICTION SYSTEM                                                                                          0
                                                                                                                                                                                               co

                                                                                                                                                                                               0                    LS.4*W
                                                                                                                                                                                                                                        16T2*W                1ST01W              158-W
                                                                                                                                                                                                   200 -160 -120 -80 -40                                0        40        @O       120 160 200
                                                                                                                                                                                                                                              RANGE        (NM)

                                                                                                                                                                                             FIG.            3. BOTTOM ACOUSTIC RETURNS FOR
                                                                                                                                                                                                                          BISTATIC SURVEY GEOMETRY

                                                                                                                                                                                                        RnTTnm RFVFRRFRAT-TnN nFINSITY

                                                        0
                                                                                                                                                                                                                                                           .... .......

                                                                                            FILTER
                                                 @uo
                                                                                                                                                                                                                                                                    ki.       ... ....  iii

                               FIG. 2. REPRESENTATION OF HATHYMETRIC
                                                                                                                                                                                                                                                    .... . . .....
                                                            PROCESSING CONCEPT

                                                                                                                                                                                                                                                                                               7771
                                                                                                                                                                                               200       1'60       1'20       40         -40         6          @0         I;i,        I         ISO        200
                                                                                                                                                                                                                                             RHNGE fNM)

                                                                                                                                                                                             FIG. 4. BOTTOM ACOUSTIC                                                         RETURNS FOR
                                                                                                                                                                                                                        BISTATIC SURVEY GEOMETRY
                                                                  4.A:TAF:B-A:-SES @"BA'WI'H
                                                                                                                           Y'
                                                                          E

                                                                                                                           P
                                                                                                                              A  S FILTERED
                                                                                                                              '              y
                                                                                                                           BI@T.YMETR

                                                                                                                                                                       297

                                                               Programmable Subsurface
                                                              Acoustic Recording System

                                                                Glenn P. Villemarette

                                                           U.S. Naval Oceanographic Office
                                                         Stennis Space Center, MS 39522-5001

                   ABSTRACT                                                    signal inputs from the hydrophones and power from
                                                                               the external battery package through watertight
                   This paper describes the upgrading      of the Naval        connectors.
                   Oceanographic Office's electronics package for the
                   Moored Acoustic Vertical Array (MAVA) buoy system.          The IRIG-B TCG produces a time reference.            it
                   The MAYA can simultaneously record the outputs of           provides a  real-time clock output for use by the
                   as many as 12 hydrophones for 32 hours.        A low-       control system.   It also provides an IRIG-B output
                   power mi crop rocess or-based design was chosen for         which is recorded on a dedicated track of the
                   versatility.   The effective recording time is put          tape.
                   to maximum use with the ability to program start
                   and stop times on an event-by-event basis.                  A separate battery provides isolated power to the
                   Amplifier gains can be automatically selected               hydrophones.   This ensures a low noise source for
                   based on maximum probable peak amplitudes using             this high-gain system.
                   the automatic gain select function. The effective
                   dynamic range of ambient-noise measurements is              A 14-track analog tape recorder is used for
                   greatly increased using the prewhitening filter.            storage of the acoustic data.       It contains 9200
                   Long deployment times are possible due to greatly           feet of tape and operates at 15/16 inch per
                   reduced    power    consumption      between    events.     second. This provides about 32 hours of recording
                   Automatic testing, status reporting, and a user             time.     Two   different   record   amplifiers     are
                   friendly interface provide user confidence in the           available.    The intermediate band direct-record
                   automated system operation.                                 amplifier provides response from about 100 hertz
                                                                               to 3900 hertz.       More reliable performance is
                                                                               available using the Frequency Modulation (FM) Wide
                   INTRODUCTION                                                Band group 1 (WB1) record amplifier.       The FM WB1
                                                                               record amplifiers will accurately record data from
                   The Moored Acoustic Vertical Array (MAVA) upgrade           direct current to 625 hertz.
                   is a subsurface, bottom-moored, automatic acoustic
                   data acquisition and recording system consisting            The microprocessor-based control system performs a
                   of   a  subsurface    instrumentation    package    and     variety of system functions including hydrophone
                   buoyancy assembly supporting a multihydrophone              interface, signal conditioning and amplification,
                   array and the necessary bottom mooring cable.          A    and automatic system operation.     It utilizes user-
                   diagram of the MAVA is shown in figure 1.              A    entered parameters for start time, stop time,
                   magnetic tape recorder in the instrumentation               amplifier gains, and synchronizing tone frequency.
                   package records acoustic signals simultaneously             In addition, diagnostic features are included to
                   from each of up to 12 installed hydrophones.        The     aid  in calibration     and troubleshooting.         it
                   internal electronics is microprocessor controlled           consists of 14 type 'STD-BUS' cards enclosed in a
                   and may be programmed for a variety of prescribed           card    cage.   All cards use Complementary Metal
                   recording intervals.    During all recording cycles         Oxide Semiconductor (CMOS) components for low
                   an Inter-Range Instrumentation Group-B (IRIG-B )            power consumption.     It includes a microprocessor
                   time-code signal and a synchronizing tone are               card, a memory card, a parallel input card, a
                   recorded on two tracks of the recorder for future           serial input/output cardi six amplifier cards, two
                   synoptic analysis of acoustic data.         The major       hydrophone interface cards, a number-controlled
                   subsystems of which the MAYA is composed are the            oscillator (NCO) card, and a power-regulator card.
                   Instrumented     Pressure   Vessel    (IPV),    battery     All cards are contained in one card cage.
                   package, flotation buoy, and a hydrophone array.
                   This paper limits itself to the upgraded IPV                Automatic system operation is provided by the
                   electronics portion of the MAVA.                            microprocessor card, the memory card, the parallel
                                                                               input card, the serial input/output card, and the
                                                                               power-regulator card.      The microprocessor card
                   IPV ELECTRONICS                                             utilizes    a    National    Semiconductor      NSC-800
                                                                               microprocessor.     It executes a custom program
                   The IPV electronics are contained in a pres-                which occupies over 8000 bytes of Read Only Memory
                   surized   vessel.       It consists   of   an    IRIG-B     (ROM).   The memory card contains volatile, Random
                   Time-Code Generator (TCG), a hydrophone battery, a          Access Memory (RAM), and nonvolatile, Electrically
                   14-track    reel-to-reel   tape     recorder,  and     a    Erasable Programmable Read Only Memory (EEPROM).
                   microprocessor-based control system.       It accepts       The parallel input card allows the microprocessor

                                                                          298  United States Government work not protected by copyright

                to access the actual (REAL) time by reading the              in recording levels which are outside the dynamic
                ?utput of the time-code generator.          The serial       range of the system.     Amplifier gain can also be
                input/output card permits user interface with a              selected automatically using AGS programming. AGS
                terminal.    The power-regulator card converts the           will be discussed in the next section.
                raw battery power to the required voltages for
                STD-BUS operation.        In addition, it controls           The   Number-Controlled     Oscillator     (NCO)    card
                switching operations and provides status signals             provides a synchronizing tone for         recovery of
                to the microprocessor.       Another feature of the          data.   This card provides a sine wave output to a
                power-regulator card is its ability to reduce                dedicated track of the recorder. The      frequency of
                power consumption drastically by switching to a              operation can range from 0 hertz (off) to 32767
                low-power, SLEEP, mode when not in use.                      hertz in steps of 1 hertz.          The frequency is
                                                                             controlled by the microprocessor.       The sine wave
                Interface to the hydrophones is provided by the              is used with a phase-locked loop to synchronize
                the hydrophone interface cards.          They provide        the analog to digital-conversion sample rate.
                power to the hydrophones and modify their outputs            This synchronous recovery is performed when the
                to be compatible with the system.         Two types of       recorded data are processed.
                hydrophone interface cards are available which
                permit the use of a variety of hydrophones.                  OPERATION

                The amplifier cards provide signal conditioning              Operation   of the MAVA is controlled by the
                and amplification.     Signals are patched from the          integral   microprocessor     which   accepts     status
                hydrophone interface cards to the amplifier cards            inputs    (Ref.  table   1)   and   provides    control
                using small cables.      A single hydrophone signal          functions (Ref. table 2).       The operation of the
                may be patched to several amplifier cards for                MAVA is controlled by its custom program.           The
                recording on multiple tracks of the recorder.                MAVA program consists of two parts:        the MONITOR
                Outputs of the amplifier cards are applied to the            program and the MISSION program.          The MONITOR
                tape recorder.                                               program provides a user interface for entering
                                                                             programmed parameters, testing, and determining
                Signal      conditioning       consists      of      one     status.    The MISSION program performs the data
                microprocessor-controlled      and    three     manually     collection process. The NAVA normally operates in
                controlled    functions.      Manual    activation    of     the MISSION program mode and only enters the
                switches provides control of a 20-dB attenuator, a           MONITOR program as a result of manual interrupt by
                20-dB preamplifier, and a prewhitening filter for            the user.
                each channel. The position of the switches is
                monitored by the microprocessor and displayed to                Table 1.    Status Inputs to Microprocessor
                the   user    with    the   STATUS   command.        The
                microprocessor      can  control    the   gain   of     a    Type                          Source
                programmable    gain    amplifier    (PGA)   for    each     -----------------------------------------------
                channel.    The range of gain selection is 0      dB to      Actual (REAL) Time            Time-Code Generator
                6U dB in 6-dB steps.                                         Fault Indicator               Tape recorder
                                                                             Recorder Indicator            Tape recorder
                Manual control of a     20-dB attenuator and a     20-dB     Relay Driver Set              Power-Regulator Card
                preamplifier is available to extend the range of             Relay Driver Reset            Power-Regulator Card
                operation for various signal levels and hydrophone           Recorder Power                Main Battery
                sensitivi 'ties.  A prewhitening filter may also be          Hydrophone Power              Hydrophone Battery
                manually controlled.      The prewhitening filter is         Analog Power, +12V            Power-Regulator   Card
                used to attenuate the large signals present at low           Analog Power, -12V            Power-Regulator   Card
                frequencies to a level similar to middle and                 Peak Detector                 Amplifier Cards
                higher audio frequencies.        A simple design was         Attenuator                    Ainplifier Cards
                chosen and precision components were used to allow           Preamplifier                  Amplifier Cards
                precise estimation of the transfer function.           It    Prewhitening   Filter         Amplifier Cards
                consists of one resistor and one capacitor. It is
                a high-pass filter which provides a 6-dB/octave                 Table 2.    Control Outputs of Microprocessor
                transfer function with its corner frequency at               Type                        Controlled Device
                3959 hertz. Its transfer function is shown below.
                          Vout = Vin * 1/(1 + j(3959/F))                     SLEEP Control               Power-Regulator Card
                                                                             Recorder Power              Recorder Power Relay
                where:                                                       Hydrophone Power            Hydrophone Power Relay
                                                                             NCO Frequency               NCO Card
                j = square root of -1, F = frequency in hertz.               Amplifier Gain             Amplifier Cards
                                                                             MONITOR PROGRAM
                The PGA varies the gains on an event-to-event
                basis.    For each event, the PGA gain is selected           Interface to the user is provided by the MONITOR
                as a result of fixed gain (FG) or automatic gain             program. The user accesses the MONITOR program by
                selection    (AGS)   programming.      For fixed-gain        manual activation of an interrupt signal.              A
                programming, the operator enters       the exact gain        terminal provides the human interface.        Commands
                desired for each amplifier when       programming the        for programming, testing, and status checking are
                scheduled events.     Because of the uncertainty of          available. The commands are: CLEAR, DEPLOY, EDIT,
                signal levels, fixed-gain programming may result             HELP, LOAD, SAVE, STATUS, and TESTx.

                                                                        299

                  The HELP command enables a text message which                 During any point of the MONITOR program execution,
                  describes the available commands and tests.                   failure to activate a keystroke for a time period
                                                                                in excess of 30 minutes results in an automatic
                  The CLEAR command is used to initialize the                   branch to the MISSION program.        This will result
                  working copy of programmed EVEMTs which are stored            in a power-off of the MAVA electronics unless an
                  in volatile RAM.       The CLEAR command turns all            EVENT is to be performed.           This feature is
                  events off.                                                   provided to prevent an undesired mission failure
                                                                                if the system is accidently left operating the
                  The EDIT command provides an interactive means of             MONITOR program.
                  programming parameters of the EVENTs in volatile
                  memory (RAM).      Up to 64 entries of EVENTs are
                  allowable.    The parameters include times to       begin     MISSION PROGRAM
                  and end each event, the frequency of the NCO card,
                  and the amplifier gains for all channels.            The      The MISSION program performs the primary function
                  START and STOP times are entered as a Day,          Hour,     of the MAVA, data acquisiton.     It acquires data in
                  and Minute.     These times will be compared with             a predetermined method as defined in the user-
                  actual   (REAL) times read from the TCG.             The      programmed    EVENTs.      The  MISSION    program    is
                  frequency of operation for the NCO card is also               executed as result of      a normal power-on reset.
                  entered by the user.      The range of operation for          This power-on reset   occurs as a result of the MAVA
                  the NCO card is 0 hertz to 32767 hertz in 1-hertz             SLEEP circuit timing out and applying power to the
                  steps.    All twelve amplifier gains are entered              STD-BUS.    The MISSION program performs the pre-
                  independently. Fixed gains may be selected in the             programmed    functions     and  returns    status    in
                  range 0 dB to 60 dB in 6-dB steps. Automatic Gain             nonvolatile, EEPROM. Normal operation of the MAVA
                  Select   (AGS)   for the amplifiers may be also               results in the     following sequence, which begins
                  entered.                                                      upon timeout of    the SLEEP circuit on the power-
                                                                                regulator card.     This sequence is repeated over
                  The SAVE command stores the programmed EVENTs of              and over again.
                  the volatile memory (RAM) into nonvolatile memory
                  (EEPROM).       The   configuration    of  the     signal           Power-Up     Mission       Sleep
                  conditioning is also saved.       Finally a checksum,               Reset        Program -->  Circuit
                  modulo 256 addition of programmed EVENTs,              is                        Execution    Activate
                  performed and saved.
                                                                                The MISSION program begins     by reading the actual
                  The LOAD command provides a means of reediting                (REAL) time from the Time      Code Generator (TCG).
                  previously SAVEd EVENTs.      The LOAD command copies         It then compares the REAL time with the START time
                  the EVENTs from nonvolatile memory (EEPROM) into              for each of the PENDING events in sequential
                  volatile memory (RAM) where they can be EDITed. A             order.   A particular event will be performed if
                  checksum is performed and compared to a previously            the START time is in the range indicated below.
                  stored checksum to verify the proper storage in               This prevents a START time from being missed due
                  the EEPROM.    An error message is displayed if the           to back-to-back event programming.
                  checksums don't match.
                  The    DEPLOY   command   is   used    to    discontinue          START <= REAL < ( START + 1 hour
                  operation of the MONITOR and vector to the MISSION
                  program. The DEPLOY command is normally performed             If no events match up, the MISSION program will
                  after the EVENT program has been generated (using             conserve    power   by   de-engerizing    the       MAVA
                  EDIT) and stored in nonvolatile memory (using                 electronics. This is performed using the sleep-
                  SAVE).                                                        activate function of the power-regulator card.
                                                                                The MAVA electronics       will   wake   up   after     a
                  The STATUS command initiates a display of the                 predetermined sleep interval        has expired. This
                  system status.       The display includes the MAVA            will result in re-engerizing the MAVA.         The MAVA
                  identification message, actual (REAL) time as read            will again resume operation of the MISSION program
                  from the time-code generator, actual amplifier                as a result of a normal power-on reset.
                  switch configurations, stored EVENT program, and
                  any accompanying      error messages.        A typical        When a PENDING event is performed, its status in
                  display of the STATUS might appear as shown in                nonvolatile memory      is  immediately changed        to
                  figure 3.                                                     COMPLETED. The actual START time is also saved in
                                                                                EEPROM.   The recorder power and hydrophone power
                  The    TESTx     command    performs     any    of     13     are turned on by activating the SET relay driver
                  troubleshooting procedures as determined by the               circuitry.    Successful switching is checked for
                  suffix X.      Tests include reading status,        test      using the status register on the power regulator
                  pattern generation, and manual         control.      The      card.     The status     is then     recorded in the
                  status   of each     of the amplifier cards,         the      nonvolatile memory.     Automatic Gain Select (AGS)
                  parallel I/F (TCG I/F), and power-regulator,        card      is performed if it is required and the actual
                  can be displayed to the user. Each amplifier        card      amplifier gains are stored in nonvolatile memory.
                  can also be injected with a test pattern from the             The amplifiers are then set to the determined
                  microprocessor,     which   allows digital      trouble-      gains.    The NCO card is set to its programmed
                  shooting.    The relays can be manually controlled            frequency.    The MAVA then waits for the stop time
                  to   allow    testing   of   the    associated     driver     as determined by:
                  circuitry.    The power-reduction circuitry, SLEEP,
                  can also be manually activated.                                  STOP <= REAL < ( STOP + 1 hour

                                                                           300

               This 1-hour window was used in case of temporary            entire event execution.      The selected gains will@
               time-code generator failure. Next the actual stop           also be stored in nonvolatile EEPROM for user
               time is saved in nonvolatile memory.         Then the       verification at recovery.
               MISSION program turns off the recorder power and
               hydrophone power, checks and saves status, and              POWER CONSERVATION
               performs    a  new checksum for the nonvolatile
               memory.   It then branches back to the     beginning of     Most of the time in a typical deployment of the
               the MISSION program to recheck for any pending              MAYA is spent waiting for the REAL time to match a
               events at the new time.     If the REAL    time doesn't     programmed event start time.       Care was taken to
               meet the START TIME requirements, the      MAYA will go     reduce power consumption when the MAYA is in
               to sleep to conserve energy.                                standby. Power to the recorder and hydrophones is
                                                                           switched out when not operating using latching
               AUTOMATIC GAIN SELECT                                       relays.     Power to the electronics is greatly
                                                                           reduced by de-energizing most circuits.            This
               Automatic Gain Selection (AGS) provides a means of          removal  of power is called sleeping.
               accurately selecting the amplifier gain for a
               stationary process with known distribution.         AGS     The MAYA MISSION program periodically reduces
               results     in a    gain   selection   based   on   two     standby power by sleeping.      When asleep all power
               parameters, the peak amplitude of the actual                is removed from the STD-BUS.        A low-power timer
               output of the particular amplifier channel and a            circuit   on   the   power-regulator    card    remains
               relative    fixed   offset    entered  at   the   EVENT     energized and reapplies power to the STD-BUS after
               program.    The MISSION program performs the AGS            expiration of a preset Sleep Period.         Two sleep
               function in the first minute of execution for each          periods are available; SHORT NAP = 45 seconds and
               event.    The corresponding programmable amplifier          normal   =   11 minutes.      The sleep period        is
               gain is first set to 0 dB.         The signal at the        initially set to normal. The sleep period will be
               output of the amplifier is tested if outside the            SHORT NAP if the microprocessor determines that a
               range of +/- 0.5 Volts.       This test is performed        PENDING event is less than one hour away.          This
               about 18000 times a second for 9000 samples.        This    dual   time approach provides efficient standby
               gain remains unchanged and exits from the AGS               operation and accurate turn-on times.
               module if the number of samples exceeding this
               @ange is greater than 5.      Otherwise, the gain is        About 300 milliamperes (mA) from the main battery
               incremented by 6 dB and the process is repeated             are consumed when the STD-BUS is energized.        When
               until it exits or the gain equals 60 dB.            The     asleep, about 30 mA are required for the TCG and
               selected AGS value is then scaled by a value                sleep timer circuit.      When in standby. the MAYA
               entered by the user.     The scale factor, Bias, can        executes the MISSION program (about 0.5 seconds)
               be -12 dB, -6 db, 0 dB9 +6 dB, or +12 dB.           The     at periodic intervals.      For long deployments it
               actual   gain is limited to       the range of the          will operate in the normal sleep period most of
               amplifier, 0 dB to 60 dB.          The expected peak        the time.    Current consumed will be 30 mA + (0.5
               voltages of signals to the        recorder are shown        seconds * 300 mA /11 minutes) or about 30.2 mA.
               below.                                                      Sleeping reduces the standby current to about 10%
                                                                           of the amount required for STD-BUS operation.
                 Bias              Expected Peak Voltages                  This permits long deployment times for the MAYA.
                                   to Recorder.
                                   Probability [8995/90001                 BUILT-IN TESTING AND DIAGNOSTICS
                 AGS-12 dB         +/- 0.125V to +/-  0.25V                The MAVA performs a number of different types of
                 AGS-06 dB         +/- 0.25V to  +/-  0.5V                 automatic and manually activated tests. Automatic
                 AGS+00 dB         +/- 0.5V to   +/-  1.OV                 tests are performed during operation of MISSION
                 AGS+06 dB         +/- I.OV to   +/-  2.OV                 and MONITOR programs.      Manually activated tests
                 AGS+12 dB         +/- 2.OV to   +/-  4.OV                 are available with the TEST command described
                                                                           earlier.
               If a gaussian       distribution is    assumed [Ref.
               URICKI, we can translate the table     above for other      The MAYA performs two automatic self-tests upon
               probabilities.       A    probability    of  8995/9000      entry into the MONITOR program. They consist of a
               corresponds to a deviation of +/- 3.4 standard              RAM test and a ROM test.       The RAM test performs
               deviation units     from the mean.      Expected peak       write/read    operations    for   several     different
               voltages    for a deviation of +/- 1           standard     patterns which are written to all Random Access
               deviation are shown below.                                  Memory (RAM). The ROM test performs a checksum of
                                                                           the Read Only Memory (ROM) and compares the result
                 Bias              Expected Peak Voltages                  with the known value.      The operator is notified
                                   to Recorder.                            with an appropriate message if either test has
                                   Probability [0.683]                     failed.

                 AGS-12 dB         +/- 0.036V to +/- 0.074V                The   NAVA   checks   the   operator   inputs    during
                 AGS-06 dB         +/- 0.074V to +/- 0.147V                operation of the MONITOR program.        An erroneous
                 AGS+00 dB         +/- 0.147V to +/- 0.294V                keyboard entry from the operator results in an
                 AGS+06 dB         +/- 0.294V to +/- 0.588V                audible indication (bell) at the data terminal.
                 AGS+12 dB         +/- 0.588V to +/- 1.176V                This can arise from the operator entering an
                                                                           incorrect command or incorrect keystroke sequence
               The selected gains will remain constant for the             while operating in the MONITOR program.

                                                                       301

                       There i.s a variety of other automatic tests which                                result of improper feedback during event turn-on/
                       are performed during the operation of the MISSION                                 off or event execution.
                       program.            They     can     be     described        in     three
                       categories:           event turn-on/off and execution,                            The configuration of attenuators, preamplifiers,
                       configuration, and EEPROM checksum.                       They result             and      prewhitening           filters        used      for       signal
                       from operator error or component failure. Failure.                                conditioning is stored in EEPROM during the SAVE
                       of any test            results       in notification to the                       command.        The STATUS command compares the act7ual
                       operator.                                                                         configuration          to the SAVEd configuration                       and
                                                                                                         displays a warning message if different.                         This is
                       Automatic       tests are performed during the turn-on,                           used as a reminder to the operator.                      The operator
                       turn-off,       and execution periods for each EVENT.                             should check if the configuration is different
                       Faults detected during actual event turn-on and                                   from that.planned.
                       turn-off sequence are recorded, saved in EEPROM,
                       and indicated under control of the STATUS command.                                For all write operations to the EEPROM, a checksum
                       Faults detected during actual                 event execution are                 is generated and stored along with the EVENT
                       separately          recorded,        saved       in     EEPROM,         and,      program      data.       Any operation that reads EEPROM
                       indicated under control of the                STATUS command.            If       such as actual event execution, LOAD command, or
                       any faults are detected they                  are displayed along                 STATUS command compares actual checksum to saved
                       with the remaining status for each event.                             Such        checksum.         An incorrect checksum results in the
                       faults are recorded for each event separately.                                    setting of an EEPROM failure flag.                       This flag is
                       Items tested include analog power, hydrophone                                     also set if a write to EEPROM can not be verified.
                       power, relay drivers, and recorder status-fault                                   The status       of this flag is tested during the LOAD
                       indicators.          Items are tested at the appropriate                          command and the STATUS command.                    If it is set, an
                       instances before, during, or after the actual                                     error message is displayed to the user.
                       switching has occurred.

                       Analog power failure is set as                  a result of analog                CONCLUSION
                       power not           being detected.              Hydrophone Power
                       failure is set as a result of inappropriate                                       The upgraded MAVA electronics provides versatility
                       absence or presence of power applied to the                                       to     a    proven      data      acquisition         system.           The
                       hydrophones.           Relay driver failure is set as a                           microprocessor-based control system can adapt to a
                       result       of     incorrect       feedback       from transistor                variety of requirements.                The modular card design
                       drivers         during     event       turn-on/off         in      either         can be easily upgraded                 as requirements change.
                       energized or de-engerized states.                     Recorder fault              These are features which                are desired for all new
                       indicator and record indicator failure is set as a                                data acquisition systems.

                                                           BUOY WITH STROBE,
                                                              TRANSMITTER                                r-----?.5 nEr

                                                                                                                      teirr   MID

                                                                                                                       VM     j i

                                                                                                             SYNTAM
                                                            HYDROPHONE CABLE ARRAY                            FUM
                                                                                                                       WERY

                                                                                                              AIR WEIGHT    POSITIVE ROTATION
                                                                                                               5750 LOS.       1270 LOS.

                                                         TANDEM ACOUSTIC RELEASES

                                                                                      MOORING CABLE

                                                                                        ANCHOR

                                                       Figure 1. Diagram           of the Moored Acoustic             Vertical Array (MAVA).

                                                                                                                                                                                   TERMINAL
                                 HYDROPNONES                                                                POWER    CONTROL/STATUS                                                (USER INTERFACE)

                                                              I/F              YDROPNONEI/F                                                                                        SERIAL 1/0
                                                                                   CARD                     POINEN-REGUIATOR
                                                   1 2 3 4 6  1                    7 1 1101112                  CARD                                                                CARD
                                                   0000       0                    000000                                   1
                                                                                   I I                          I I                    @t It]
                                                                                              STU - iu-s
                                                                                                       I F_
                                        20AW                                                                           2 CH A
                                                              2 IN AMP             2 CH AMP         2 CN AMP           CUD
                                                                                                                                    101 1 '112 CN AMP                                                           -CODE
                                        a" #0                 CARD #1              0 #2             CARD #3                                CARD     5            NCO               PARALLEL INPUT  BCD      TIME
                                     cm 1        M2      CK 3       04       CNP       a        07          C1 I     CH I                  I        CN 12        CARD               CARD                    GENERATOR
                                     00        0   0     00         00       00        0.1. 00              00       00        00      00           00

                                                                                                                                                                                   C,

                                                                                                                                                                                   C1 12 6"
                                                                                                                                                                                   CN
                                                                                                                                                                                   010
                                                                                                                                                                                   CH
                                                                                                                                                                                   CK 8
                                                                                                                                                                                   CK7
                                                                                                                                                                                   CN I
                                                                                                                                                                                   CN 5COD

                                                                                                                                                                                   CN 3

                                                                                                                                                                                   CN I

                                                                                                       Figure 2. MAVA Upgrade.

                                                      Moored Acoustic Vertical                         Array                        Event 01                          Status: COMPLETE
                                                      Version 1.03, 26 October                         1987                            Start Time: 001:10:00
                                                      U.S. Naval Oceanographic                         Office                          Stop Time: 001:12:30
                                                      Stennis Space Center                                                          ELAPSED TIME= 000:02:30
                                                      Mississippi, USA                                                                 Tone (Hz): 00000
                                                      Time=016:09:32                                                                            Programmed Gains
                                                                    20-dB Attenuators                                               CHOI     CH02 CH03                CH04         CH05 CH06
                                                      CH01 CH02 CH03 CH04 CH05                                  CH06                OdB         6dB        OdB        24dB         30dB 36dB
                                                         IN         OUT            IN      IN          IN            OUT            CH07     CH08 CH09                CH10         CH11 CH12
                                                      CH07 CH08 CH09 CH10 CH11                                  CH12                OdB         6dB        OdB        12dB         OdB 24dB
                                                         IN         IN             OUT     IN          IN            IN             Event    02                       Status: PENDING
                                                                    20-dB Preamplifier                                                 Start Time: 021:10:00
                                                                                                                                       Stop Time: 021:12:30
                                                      CH01       CH02 CH03 CH04 CH05                            CH06                ELAPSED TIME= 000:02:30
                                                         IN         IN             OUT     OUT         OUT           OUT               Tone (Hz): 00000
                                                      CH07       CH08 CH09 CH10 CH11                            CH12                            Programed Gains
                                                         IN            IN          OUT     IN          IN            OUT            CHOI     CH02 CH03                CH04 CH05 CH06
                                                                    Prewhitening Filter                                             OdB         6dB        OdB        A+00 A+06 A+12
                                                      CH01       CH02 CH03 CH04                     CH05        CH06                CH07     CH08 CH09                CH10 CH11 CH12
                                                              IN       IN          IN      OUT              IN       IN             OdB         6dB        OdB        12dB         OdB 24dB
                                                      CH07       CH08 CH09 CH10                     CH11        CH12                Event    03                       Status: OFF
                                                              IN    OUT            OUT     OUT              IN       OUT
                                                                                                                                    Event    04                       Status: OFF
                                                                                                                                       through . . .
                                                                                                                                    Event 64                          Status: OFF
                                                                                                    Figure 3.             Status Display.
                       REFERENCES
                       1. Urick, Robert                       i        Principles of Underwater                                     Proceedings            1983       Symposium on Buoy Technology,
                       Sound, 3rd ed., McGra;-1H1II, Inc., 1983.                                                                    Marine Technology                 Society, Gulf Coast S                 'ection.
                       2. Swenson, R., J. Selleck, and N. Dennis, "High                                                             3. Beyer, William                 H., CRC         Standard            Mathematical
                       Performance Deep Sea Subsurface Buoy Mooring,"                                                               Tables, CRC Press, 19A.
                                                                                                                                                    SIR

                                                                                                                                                    P
                                                                                                                                                -57

                                                                                                                         303

                                      The Relationship Between Acoustic Bottom Loss and the Geoacoustic
                                                        Properties of the Sediment

                                                                Diana F. McCammon

                                                          Applied Research Laboratory
                                                    P. 0. Box 30    State College, PA 16804

                                      ABSTRACT                              The layer model chosen for this study is a
                                                                            relatively simple three fluid layer model that
                A study of the functional variations between                uses 10 geoacoustic parameters and makes several
                acoustic bottom loss from       50-1500 Hz and the          assumptions[2].      It relies upon the "hidden
                sediment geoacoustic parameters of density, sound           depths" concept which states that the regions well
                speed, thickness and attenuation has shown that             below the turning point do not affect the ray.
                simple relationships exist between certain of               The sediments are assumed isotropic, and the
                these parameters and specific angular regions of            roughness of the sediment and basement interfaces
                the loss curves.        These relationships permit          as well as multiple scattering within the layers
                bottom losses to be     estimated directly from the         is neglected.    The neglect of roughness of the
                geoacoustic    parameters   without   the   need    to      sediment may be justified because this is a total
                exercise complex layer modeling.                            energy     model  and    the   roughness     primarily
                                                                            redistributes the energy in angle about the
                                                                            specular without decreasing the total energy.
                                                                            Finally, shear wave propagation is ignored. While
                                  I. INTRODUCTION                           the effects of shear wave conversion at the water-
                                                                            sediment layer have been shown to be negligible in
                Geoacoustic modeling of the interaction between             Vidmar(31   the process     is   substantially more
                acoustic energy and the ocean floor has gained              important at the basement interface.      the neglect
                considerable favor among researchers because it is          of this loss mechanism at low frequencies and in
                presently the best method of incorporating the              thin sediments may be the primary weakness of this
                physics    of    sound   propagation,      refraction,      model.
                scattering, and boundary wave conversion into the
                bottom loss process.        This type of modeling           The required parameters for this layer model are
                consists of developing a layered profile of the             sediment density, thickness, sound speed gradient
                sediment with depth dependent attenuation, sound            and    curvature,     attenuation   and attenuation
                velocity   and density     over-laying a basement           gradient,   thin layer     density and thickness,
                halfspace.    Ray tracing techniques can then be            basement reflectivity and water-sediment velocity
                employed to compute the total energy returned to            ratio.
                the water column. This approach has been shown by
                Knobles and Vidmarl] to be quite successful at              For this model, the total energy bottom loss in
                predicting     the    bottom   returning     waveform.      the form of plane wave reflection at grazing angle
                Certainly the emergence of this type of modeling            Ow is computed by two path contributions; the
                ,has greatly improved the quality of bottom loss            reflected path and the sediment transmitted path.
                calculations for those areas of the world's oceans                               2                  2
                whose geoacoustic profiles have been constructed.           BL(Ow      10 log,,[Rw+ (Tl 3T31 RBe

                One drawback to the efficient operational usage of          Where      Rw is the reflection coefficient from a
                the geoacoustic layer model of bottom loss is that                     three-layer fluid sediment(41,
                the geoacoustic parameters do not, of themselves,
                convey a sense of the loss to be expected.                             T13 is the transmission coefficient,
                Presently, given the area of interest and its
                geoacoustic parameters, a model must be exercised                      RB   is    the   basement       reflection
                on a computer before bottom loss can be known.                         coefficient,
                Because of the complex interaction of acoustic
                energy in this layered environment, an association                     a   is   the    attenuation      of     the
                between bottom loss and the geoacoustic profile is                     compressional wave, linear in frequency
                not immediately obvious.      However, the research                    and depth,
                presented in this paper will demonstrate that
                there    are   clear    relationships   between    the                 r  is   the ray path length in the
                geoacoustic parameters and certain angular regions                     sediment.
                of the loss curves.      These relationships permit
                the assignment of a loss ranking system based on                   II  MODEL PREDICTIONS-DOMINANT EFFECTS
                the   values    of    the   geoacoustic     parameters
                themselves.                                                 To study   Eqn. (1), the bottom types should first

                                                      CH2585-8/88/0000- 304 $1 @1988 IEEE

                    be divided into two groups: those with a velocity                                                           1.0
                    ratio greater than unity and those less than                                                       :--                                   f = 1000 Hz
                    unity.           A velocity ratio greater than unity                                                                                     CS/CW= 1.015
                    predicts a critical angle Oc below which most of                                                   Z        0.8-                         K = 0.0062 dBfm/KHz
                    the energy is reflected;                          cosOc - cw/cs.                      A            Q        . -                                                                 3
                    velocity ratio less than unity will cause the                                                      FE                                    PS          VARIATION FROM 1.5 TO 5.0 gmkm
                                                                                                                       z.       0.6-
                    energy to be driven more deeply into the sediment                                                  a        -
                    making the transmitted path dominant.                                                                                                                5.0     REFLECTED PATH
                                                                                                                                0-4- 1.5
                                                Hip-h Frequencies

                                                                                                                                0.2-
                    The study will begin with velocity 'ratios greater                                                 fr-                                               2.0
                    than unity, frequencies, about 1 kHz and thick                                                                                                       1.5
                    sediments.           In Figure 1, the upper curve displays                                                  0
                                                                                                                                11            0              30          40 50   60   70      80      90
                    the energy variations in the two paths vs angle                                                                   10 L2      ANSMITTED PATH
                    with the high velocity ratio, cs/cw - X as a
                    parameter. The lower curve displays the resulting                                                           15-
                    bottom loss.               At frequencies above 200 Hz the                                                                                           1.5
                    reflected path            carries most of the energy and the,                                                                                        ---------
                                                                                                                       C@
                    position of the critical angle controls the onset                                                           10-                                      2.0
                    of loss.          The major characteristics of reflection                                                                                            2.5
                    influence the remainder of the curve and are seen                                                                                                    3.0
                    to be independent of the velocity ratio. In Fig.                                                            5-
                    2, Variations in the sediment density ps are shown
                    with a fixed high velocity ratio.                                      Here the                                                                      5.0
                    impedance characteristics of the sediment have a                                                            0                                                              -------
                    direct effect on the level of reflected energy                                                              0    10       20             30          40 50   60  7a       80     90
                    above the critical angle of 10*.                                                                                                         GRAZING ANGLE (degi
                                 1.0  1.0                                                                                 Fig. 2 Density                     variation, high     X, 1000 Hz.

                      F5         0.8                       1.1326                                                               1.0     005
                                                                                                                                                                         I = 10003
                                                                                                                                                                         m1cm
                                                                                                                                                                         PS = 2.4 g
                                 0.6
                                                           REFUCTED PATH                                              t         0.8 -.06                     C IC = 1.015
                                                                                                                                                             S W
                      Cr
                                        .0                                                                            Z
                                 0
                                 0.4
                                 .4-                                                                                  Z         0.6 -                        K VARIATION FROM .06 TO .005 dBImIKHz

                                                                                                                                         REFLECTED PATH
                                 0.2
                      <                                                                                                         0.4-
                      FF                                   TRANSMITTED PATH
                                 J                 -a---- 1. 1326                                                               -  .005
                                                                                                                                0.2-
                                 15 -                      f = 10M HZ      3                                                                      -TRANSMITTED PATH
                                                           PS = 2.4 gm/cm
                                                                                                                                  .06
                                                           K= 0.0062 dB/MIKHz                                                   0-                           - - - - - -- 6.
                                 10 -                  C   S/CWVARIATION FROM     1.0 TO 1.1326                                 10 -
                      ta-
                                 5      1.0                                                                                     5    0.06
                                                                                                                                                  0.005

                                                           1.1326

                                 0                                                                                              0
                                 0    10      20       30    40      50      60              80       90                        0     10      20             30          40 50   6D  7'0      80     90
                                                           GRAZING ANGLE (deg)                                                                               GRAZING ANGLE (deg)
                    Fig. 1        Sensitivity to velocity ratio at 1000                              Hz.-                       Fig. 3 Attenuation, high X,                      1000     Hz.

                    The more dense sediments reflect more energy                                     and            the transmitted path is important                            from   0. to 20.*
                    consequently show lower losses as expected.                                      The            grazing,         but        at           angles      above     this       region,
                    thin layer remains acoustically transparent- at                                                 reflection dominates just as in                              the high ratio
                    thickness less than a quarter wavelength; at                                                    cases shown above, as shown, for example, in Fig.
                    '@reater thicknesses it replaces the sediment as                                                4, in comparison with Fig. 2.
                    t:@e primary reflector.                   Fig. 3 contains examples
                    of           the predicted             losses      when       the       sediment                Thus we can conclude that high angle bottom losses
                    attenuation is varied for a fixed density and                                                   in thick sediments are entirely governed by the
                    velocity ratio.                                                                                 impedance characteristics of the upper layers, and
                                                                                                                    the major characteristics are predictable by
                    In the low velocity ratio cases, (less than unity)                                              density ranking alone.
                                                                                                                                       ,uu.7
                                                                                                                                                                         I
                                                                                                                                                                         P'2
                                                                                                                                                                         "0 'm"M'
                                                                                                                                                             K

                                                                                                                                                             P
                                                                                                                                                                         HZ
                                                                                                                                                                         5
                                                                                                                                                             Si             'M'  K"Z
                                                                                                                                                                         VAR ATI ON FROM 5 05     -m3
                                                                                                                                                                         I       I-   T .0 gmir

                                                                                                                                                                                 REFLECTED PATH
                                                                                                                                                                         5-0
                                                                                                                                115
                                                                                                                                                                         2.0
                                                                                                                                          M
                                                                                                                                                                         .5
                                                                                                                                           t`12

                                                                                                                                                                         .0
                                                                                                                                                                         2.5
                                                                                                                                                                         30

                                                                                                                                                                         0
                                                           LRE-F-CTEDITPrATH                                                    '06                                      *05
                                                                                                                                                                         10
                                                                                                                                                             KVAR        IAT N FROM .06 TO .005 dBImIKH7

                                                                                                                                         REFLECTED PATH

                                                            A         ED   PATH
                                                                                                                                   .0@
                                                                                                                                                             TR          P
                                                                                                                                                             ANSMI       TTED A
                                                                                                                                   06
                                                                                                                                    0. @005
                                                           /1-1326

                                                                                                            305

                               1.0                                                                                                    1.0                                   f = 1000 Hz3
                                                                  I = 1000 Hz                                                                                               PS = 2.4 gm1cm
                                                            CS1CW = 0.990                                                                           C I C = 0.990
                               0.8                                                                                                    0.8           S                       W
                                                                  K = .0062 dB/m/KHz                                       Z
                                                                                                     3                                              K VARIATION FROM .06 TO .005 dB/m1KHz
                                                            PS    VARIATI ON FROM 1.5 TO 4.0 gm1cm
                          C9   0.6                                                                                         Z          U.0 P TRANSMITTED PATH

                                                                                                                                        005
                          @5   0.4        TRANSMITTED       PATH                                                                      0.4
                                            .5                    4.0                   REFLECTED PATH
                                    4.0                                                                                                                                         REFLECTED PATH
                               0.2                                                                                                    0.2
                                                                                                                                      .01

                                  0                                                                                                   0                                               Meg
                                                                                                                                      20-
                               15                                 1.5                                                                 0.06

                          kA
                                                                                                                                      15-0.04
                               10                                 2.0                                                                      0.031
                                                                  2.5                                                                               K                       1O.M02
                                                                                                                                                    0.021                   0.0001
                          cc                                                                                                          10

                                                                                                                                      0.6
                                                         4.0                                                               Cd         5             0.005

                                  a      10      20         310   40    10      60      70      M       90
                                                            GRAZING ANGLE (deg)                                                       0                                     L
                                                                                                                                        10          20                      30 40 50 60 70    80        90
                               Fig. 4 Density               variation, low         X,   1000 Hz.                                                                            GRAZING ANGLE (deg)
                                                                                                                           Fig.       5 Attenuation variation, low X,                     1000 Hz.
                        At shallow grazing                  angles and high             frequencies,                                  Attenuation gradient variation                       is also
                                                                                                                                      shown for two cases.
                        the most important                  loss factor in the transmitted
                        path is the dissipation loss e-,r.                              This damping
                        is dependent upon the sediment attenuation and the                                                                          Low Freguencies
                        sediment sound speed profile.                         Variations of the
                        two paths vs angle and the resulting bottom loss                                              Next,           consider                              the low frequency (50       Hz)
                        are shown in Fig. 5. Here, the parameter changes                                              sensitivity in                thick sediments.                  Most of the
                        of the absorption coefficient x create a profound                                             energy that penetrates the sediment will be
                        change in the low angle losses.                                                               returned because the attenuation is very small,
                                                                                                                      making the transmitted path contribution much
                        The variation of the absorption gradient is also                                              larger.         Examples are given in Figs. 6 and 7 for
                        demonstrated for 2 values and is shown to have a                                              high and low velocity ratio cases with sediment
                        minor role.            However, variations of the sediment                                    density as a parameter.
                        sound gradient curvature and velocity ratio that
                        are not shown here also have a major effect on the                                                            1.0 TRANSMITTED PATH
                                                                           To account for all                              >-                                               f = 50 Hz
                        low angle curve behavior.                                                                                                   1 5                     C 1CW= 0.990
                        these sensitivities and obtain a suitable factor                                                                                                    S
                        for ranking the low angle losses, dissipation loss                                                            0.81                                  K = D062 dB/M/kHZ
                                                                                                                                      1                                                                 3
                        exponent or is normalized and approximated by                                                                                                       VARIATION FROM 1.5 TO 4.0 gm/cm
                                                                                                                           z          0.6                                   S
                                                                                                                           @2         4.0\\
                               KXcos (X)/gs, where x - cs/cw.                                         (2)
                                                                                                                                      0.4                                   REFLECTED PATH
                                                                                                                           Z
                        By' this equation, low angle losses are found to be                                                           4.0
                                                                                                                                      0.2                                   - - - - - - - - - - - -
                        directly proportional to the sediment attenuation,
                        inversely             proportional            to      the       sound        speed                                                                  .5
                        gradient,          and functionally dependent on the                                                          0
                        velocity ratio.               Specific details of the profiles                                                10
                        such as the curvature and absorption gradient
                        produce only second order effects.                                                                                                                                              1.5
                                                                                                                                      5                                                                 .0
                        Thus far, the preliminary conclusions are that,
                        for frequencies about 1 kHz and thick sediments,                                                                                                                                4.0
                        high angle losses can be predicted based on a                                                                 0
                        knowledge          of     the       sediment        density while                the                          a la          20                      30 40 50 60 70    80        90
                        velocity ratio, velocity gradient and sediment                                                                                                      GRAZING ANGLE Ideq)
                        absorption                  will          determine             the          major
                                                                                                                                                                            'S
                                                                                                                                                                            'C

                                                                                                                                                                            K

                                                                                                                                                                            S
                                                                                                                                                                            W

                                                                                                                                                                            V
                                                                                                                                                                            AR
                                                                                                                                                                            5
                                                                                                                                                                            P

                                                                                                                                                                            w

                                                                                                                                                                            T
                                                                                                                                                                            274

                                                                                                                                                                            10
                                                                                                                                                                            9
                                                                                                                                                                            g
                                                                                                                                                                            0
                                                                                                                                                                            H
                                                                                                                                                                            M
                                                                                                                                                                            'Cm

                                                                                                                                                                            OM
                                                                                                                                      LK            VA R I=A                N FR3.06 TO .005LdCl
                                                                                                                                      MNSMIT70 PATH
                                                                                                                                      J\
                                                                                                                                        005

                                                                                                                                                                                REF E
                                                                                                                                      .0
                                                                  2'- 0-                                                              04V
                                                                                                                                           0.       03
                                                                  2                                                                                 0                       0'=
                                                                  .5
                                                                                                                                                    K'                      0.000,
                                                                                                                                                    021

                                                                                                                                                    0. 005

                                                                                                                                      40\\-

                                                                                                                                                                            15
                                                                                                                                      4.0

                        characteristics below 20*.                                                                                    Fig. 6 Density variation, low X, 50                    Hz.

                                                                                                               306

                         1.0                                                                                 loss.       It is primarily employed in regions where
                       >.                                                                                    anomalously high             returns were recorded that could
                       U
                                                                                                             not be predicted using the measured geoacoustic
                         0.8 -                                                                               parameters of the            sediment. Densities of the thin
                                                   TRANSMITTED PATH
                                            2 0                                                              layer are higher             than the sediment to account for
                         0.6 -
                                                                                                             these anomalies.               The principal effect of this
                                                                        REFLECTED PA                         extra layer is               to replace the sediment as a
                                                                                      TH      5.0            reflecting surface when the layer thickness is
                       It 0.4-                                                                  4.5
                                                                                                             greater than 10 cm.
                                                                                                4.0

                       Q 0.2 -                                                                               Table I summarizes all these trends for high and
                                                            - - - - - - - - - - -                            low frequencies in thick sediments.

                            0
                         15                                                                                                                  Table I
                                                   f= 50 Hz                                                           Principle Sources of Energy Predicted
                                             C /C  = 1.015
                                              S    W                                                                            by the Thin Layer Model
                                                   K = .0062 d8imUz
                         10                  PS VARIATION FROM 1.5 TO 5 gm/cm3                                           T      transmission R - reflection
                                                                                               13            Angular                         Frequency Region
                            5                                                                  2.0
                                                                                                             Region               f < 200 z                          f > 200 Hz
                                                                                      -5.0
                                                                                                                                          Loss                                  Loss
                            0                                                                                0    20* Rath                mechanism              path        mechanism
                            0      10     20       30   40       50    60     70     80      90
                                                   GRAZING ANGLE Ideq)                                       Low X          T          dissipation                T        dissipation
                            Fig. 7 Density variation, high X,                     50   Hz.
                                                                                                             High X          R+T       critical angle             R          critical
                                                                                                                                       + dissipation                         angle +
                                                                                                                                                                             reflection
                   The gradual decrease in transmitted                         energy shown                                                                                  losses
                   in both figures from the peak to, 30*                       is' caused by
                   an increase in the dissipation ar as                       a result of                                                 Loss                                  Loss
                   increasing r.              The abrupt flattening above 33*                                30-90*        path        mechanism                 i)ath       mechanism
                   results because                 the    transmitted ray is now
                   basement limited.                                                                         no thin      T+R          basement reflec-           R          reflection
                                                                                                             layer                     tion + reflec-                        from
                   Despite          the      increased           importance           of       the                                     tion from sediment                    sediment
                   transmitted path, the low frequency,'                            low angle
                   behavior is caused by the                    same mechanisms as at                        thin         T+R          basement reflec-           R          reflection
                   high frequencies so that the@ 1000 Hz ranking                                             layer                     tion + reflection                     from thin
                   -system will still be valid (by velocity ratio or                                                                   from thin layer                       layer
                   dissipation loss):.

                   The high angle behavior is now; however, -clearly                                                                   Sediment Thickness
                   influenced by the transmitted path, primarily by
                   the loss combination T3lTl3RB-                      Since T31T13 - I-                     As the sediment thins, the basement will be
                   R2  13, the factors that affect the reflection                                            encountered at shallower and shallower angles.
                   coefficient will inversely affect the transmission                                        Below 200 Hz where the transmitted path is
                   coefficient,           that is,          low sediment densities                           important this will cause the angle where the
                   correspond to increased energy in the transmitted                                         curve levels out, (here referred to as the knee of
                   path.            Fortunately,            this       reversal        is      not           the curve), to be shifted toward lower angles. In
                   sufficiently strong at 50 Hz, to reorder the                                              effect, the sediment thickness determines the
                   ranking system.                 While the bottom losses for                               dividing point in angle between the two separate
                   changes in ps are much closer in value as compared                                        low angle and high angle loss mechanisms.                              These
                   to the 1000 Hz case, they can still be ranked by                                          shifts can be seen clearly in Fig. 8, where only
                   order of decreasing sediment density -as -in the                                          the sediment thickness is varied.
                   1000 Hz case.              Changes in RB as great as 3 dB
                   create at most a 1. 5 dB, variation in the high                                           A secondary effect is the lowered level of high
                   angle section of the bottom loss.                        Thus, the high                   angle loss as the sediment thins.                               This is a
                   angle behavior can be ranked using the same system                                        consequence of the shorter path through the
                   as at 1000 Hz _- namely by sediment density,                              even            thinner sediments that engenders less attenuation
                   .though reflection is no longer the dominant                              loss            of the transmitted energy. Note that the slope of
                   mechanism.                                                                                the curve rising to the knee is independent of
                                                                                                             sediment         thickness          since       it     is       associated
                                                   Thin LAyer                                                primarily with               the       transmission           coefficient
                                                                                                             properties. Only the very thinnest sediments (<80
                   The thin layer is an artificially introduced upper                                        m) show these effects above 200 Hz because, at
                   sediment layer that serves to decrease the bottom                                         higher frequencies, the transmitted portion of the

                                                                                                    307

                            15                  f = 50 HZ                                                  angle) of the average curve using the loss ranking
                                               CS) CW = 0.990                                              scheme.
                                                K =.D4 dSImikHz
                                                ps = 3.0                                                                          Ist PARAMETER                3rd PARAMETER
                             10                                                                                                   LOW ANGLE LOSS               HIGH ANGLE LOSS
                                               SEDIMENT THICKNESS VARIATION FROM 0.5 TO 1.0                                       15 -                            4
                                               SEC. TWO WAY TRAVEL TIME.
                              5                                                                                                   10-                             3
                                       0.5                                                                    BOTTOM LOSS             6                           2
                                                                                                                                  @ 5,
                                                        1.0                                                   AT I kHz                                            1
                              00      10       20  30     40     50     60     70      so    90
                                                     GRAZING ANGLE (deg)
                        Fig. 8 Various sediment thicknesses at 50                         Hz.                                     10  2nd PARAMETER
                                                                                                                                      SEDIMENT THICKNESS-LOW FREQUENCIES
                                                                                                              BOTTOM LOSS
                       energy is       much smaller and penetration to the                                    AT 50 Hz            5
                       basement is      more severely attenuated.
                                                                                                                                  0
                                         III LOSS CIASSIFICATION                                                                  0   10  20    30 40      50  60    70   80   90
                                                                                                                                                GRAZING ANGLE Ideg)
                       Based upon      the recognized dominant trends of the
                       thin layer      model, the data base parameters can be                              Fig. 9 Schematic diagram of loss classification.
                       placed in a loss ranking system that indicates the
                       relative amount of bottom loss to be expected.
                       Each set of geoacoustic parameters can be assigned                                                             IV SUMMARY
                       a designator giving a direct link to the amount of
                       loss in different grazing angle regions.                                            A thin layer of            acoustic energy interacting with
                                                                                                           the sea floor has been utilized to study the
                       For example, a ranking valid from 50-1000 Hz can                                    sensitivity of the predicted bottom loss with the
                       be constructed using a three digit designator in                                    geoacoustic parameters.               Parameters for inputs to
                       the form of a number, letter, number (ie. 4B2).                                     this model are the densities of each layer.
                       The first digit is a number corresponding to the                                    Ceoacoustic            modeling         represents           a      clear,
                       low angle losses, with the lowest number the                                        improvement in the theoretical computation of
                       lowest loss.            This category is assigned based on                          bottom loss because it contains the physics of
                       the critical angle or dissipation loss, where the                                   layer      interaction.              However,       there       is     one
                       highest velocity ratio yields the lowest loss, and                                  disadvantage to the geoacousticapproach: there is
                       for velocity ratios less than unity, the highest                                    no direct relationship between the geo-acoustic
                       dissipation loss yields the highest loss.                             The           parameters             and the      resulting       losses.            For
                       third digit, a number, corresponds to the high                                      operational use, this disadvantage is severe. The
                       angle loss level, in which low numbers indicate                                     analysis in this study reveals that the low angle
                       low losses.         This category is assigned based on                              loss mechanisms are independent from the high
                       the sediment density, thin layer thickness and                                      angle loss mechanisms.               The low angle losses are
                       thin layer density, where dense sediments yield                                     caused by losses of the transmitted ray that
                       lower losses.              The second digit,               a letter,                depend upon the sound speed ratio, sound speed
                       indicates the sediment thickness class.                            An A             gradient and the. attenuation within the sediment
                       corresponds          to     thick      sediments        while      a       D        whereas high angle losses are caused by reflection
                       corresponds to very thin sediments. The effect of                                   from the water/sediment interface and depend
                       this parameter is to cause a shift in the knee of                                   primarily on the sediment density.                      The sediment
                       the loss curves toward the origin so that class D                                   thickness affects the position in angle of the
                       curves have more propagation loss at low angles                                     change       between       these      this       regimes.           These
                       than class A curves, however, this shift only                                       generalizations enable the formulation of a loss
                       becomes noticeable at frequencies below 200 Hz.                                     classification scheme that links the geoacoustic
                       An example of the ranking system is shown in Fig.                                   parameters directly with the amount of loss to be
                       9, where 6 low angle and 4 high angle classes have                                  expected in specific angular regions.
                       been def ined.          The dashed lines demonstrate the
                       cross linking between low and high angle.                             The           Comparisons made between the predictions f the
                       lower figure illustrates the effect of sediment                                     thin layer model and the group averages using the
                       thickness classes.               As an accuracy check, some                         loss classification scheme have shown exceptional
                       3000      geoacoustic            parameter         and       frequency              agreement.             Better than 88% of 3000 cases fall
                       combinations were chosen at random and comparisons                                  within +2 dB of the average when reorganized using
                       were made between the full model result and the                                     the loss classification.
                       classification           scheme       with      simplified          model
                       result*.         The result was that an overwhelming
                       majority of bottom loss curves (better than 88%)                                        The simplified model is a least squares fit to
                       fell with +2 dB (everywhere in frequency and                                            the average loss curve of each loss category.

                                                                                                    308

                                 REFERENCES

             1.    Knobles, D. P. and P. J. Vidmar, "Simulation
                   of Bottom Interacting Waveforms," J. Acoust.
                   Soc, Am. 79(6), pp. 1761-1766 (1986).

             2.    Vidmar, P. J., "Ray Path Analysis      of the
                   Sediment   Shear  Wave   Effects   in    Bottom
                   Reflection Loss," J. Acoust. Soc, Am. 68, pp
                   639-648 (1980).

             3.    Spofford, C. W., Greene, R. R., and J. B.
                   Hersey, "The Estimation of Geoacoustic Ocean
                   Sediment Parameters from Measured Bottom Loss
                   Data," Science Applications Inc., McLean,
                   22102, Report No. SAI-83-879-wa (1983).

             4.    Spofford, C. W. , "Inference of Geo-Acoustic
                   Parameters from Bottom-loss Data," Bottom
                   Interacting Ocean Acoustics, W. A. Kuperman
                   and F. B. Jensen Ed. Plenum Press, New York,
                   p. 159-171 (1980).

                                                                   309

                                             SOURCE SHIP CONTAMINATION REMOVAL IN A BROADBAND
                                                                VERTICAL ARRAY EXPERIMENT

                                                                                    W.S. Hodgkiss

                                                                        Marine Physical Laboratory
                                                                    Scripps Institution of Oceanography
                                                                           San Diego, CA 92152

                                           A13STRACT
                  In March 1987, the Marine Physical Laboratory conducted a               kn, the HX-90 source was at approximately 105 in (350') in
                  broadband experiment 400 nmi west of San Diego in 2200 fm               depth.
                  water. A 55 element vertical array was deployed from FLIP                     The presence of the tow ship at close range presented a
                  to a depth of 305 in. During the experiment, several                    high-level, broadband contaminant in the data. The focus of
                  broadband source tows were made at close range to.FLIP                  this paper is on the use of adaptive cancellation techniques to
                  with typical CPA's on the order of 1 rimi. These data were              remove the tow ship contamination.
                  collected in order to perform cross-correlations between
                  hydrophone pairs and between beams receiving the direct and
                  surface reflected paths. The presence of the tow ship at close
                  range presented a high-level, broadband contaminant in the                          H. Adaptive Interference Rejection
                  data. The focus of this paper is on the use of adaptive noise
                  cancellation techniques to remove the tow ship contamination.                 One approach to the problem of interference rejection is
                  The adaptive processing is accomplished by treating the time            the use of an adaptive noise cancelling structure. In this case,
                  series obtained at the output of the beam pointing at the tow           a broadband beam pointing at the source ship is used as an
                  ship as the reference input to a simple adaptive noise                  interference reference. The output of this reference beam is
                  cancelling structure with each hydrophone time series (in               adaptively filtered, then subtracted from the output of one of
                  turn) treated as the primary input. After   'noise cancellation,        the array elements. This procedure is repeated for each
                  the contamination-free individual element signals then are              element of the array. The contaminant-free element signals
                  available for processing as originally intended.                        then are available for processing as originally intended.
                                                                                                The all-zero, joint process, least-squares lat tice (JCLSL)
                                                                                          structure used to accomplish the noise cancelling operation is
                                          I. Introduction                                 shown in Figure L, The reference channel process x(n) is
                                                                                          filtered to form an estimate of the negative of the primary
                        The Marine Physical Laborat    Iory conducted a broadband         channel process d(n) (often known as the desired response).
                                                                                          Of particular interest in noise cancelling applications is the
                  vertical array experiment in March 1987 approximately 400
                                                                                          residual ed(n) obtained by adding the filtered reference
                  nmi west of San Diego. The FLIP (FLoating Instrument                    channel to the primary channel.' In the application being
                  Platform) was towed out to 32 * 49. 1'N, 124' 59.2'W (water             considered in this paper, d(n) is the output of one'of the array
                  depth approximately 2200 fm) and drifted in the vertical in             elements contaminated by the source ship signature and x(n)
                  the vicinity of these coordinates for the remainder of the              is the output of the reference beam which is pointing directly
                  experiment.                                                             at the source ship. The reference beam is prevented from
                        Shortly after arriving on station, the MPL vertical array         passing signals propagating from directions of interest (i.e. the
                  was deployed to a depth of approximately 305 in (top                    surface reflected and direct paths of the source) due to its low
                  element). Of the 55 available elements across the array                 sidelobe response in those directions. The adaptive filter is
                  aperture, 50 functioned properly. Array element spacing was             attempting to generate   a good estimate of the contaminant
                  3.75 in (half-wavelength at 200 Hz).                                    present in d(n).
                        The FLIP tow ship provided sound source tow services                    The equations describing the JCLSL implemented here
                  for the experiment. During the active periods, the source ship          have been discussed in detail elsewhere and will not be
                  towed a HX-90 sound source emitting an index CW signal for              repeated [1-21. Additional discussion on adaptive least-
                  approximately 2 minutes at the beginning of each magnetic               squares lattice structures can be found in [3-51.
                  tape recording the digitized hydrophone data followed by
                  broadband (nominally 100-300 Hz) for the remainder of the
                  tape (approximately 16 minutes).
                    I   Typically, the constant-course runs began and finished      at
                  a range of 5 nmi on opposite sides of FLIP with CPA's of
                  approximately 1 nmi. With a typical source ship speed of 5.5

                                                                CH2585-8/88/0060-310 @$1 @1988 IEEE

                                         -d 0 (n)                                                                                         -^dP(n)                                                                                                          .-d i     (n)
                                                                                                                                          d
                                                                                                                                          a (n)                                                                                                                      ad
                          d (n)          + 0   d (n)                                                                                      P                                                                                    +                                     N
                                                      1 151 Stage                                 P 1h Stage                                                                                                                           d
                                   K d                                                                                                                                                                                               K
                                     0         r. (n)                                                                                     'p (n)            r,, 1(n)                                            +                                                    r(n)
                                                                                                                                                                                                 r
                                                                                                                                                                                            K    J
                                             a (n)                                                                                        P                                                                     +                                                    a(n)
                           X (n)                      L

                                 Figure Ia.          All-zero, joint process, least-squares lattice.                                                                                Figure 1b. ilk stage of the lattice.

                                                               M. Data Amalysis                                                                               Figure 6 displays power Spectra at the output of time-
                                                                                                                                                     delay beamformer beams pointing at the surface reflected
                                 Figures 2-8 are from an analysis of Tape 07052 which                                                                arrival (-16.6 * ) (top panel), tow ship arrival (-13.1 * ) (middle
                       encompasses the CPA of the first source tow. Figure 2                                                                         panel), and direct path arrival (-10.2 * ) (bottom panel)
                       displays power spectra from hydrophones *, 20, 40, and 55                                                                     calculated during the fifth segment of Tape #7052 (16384
                       calculated during the first tape segment (65536 data points or                                                                points or 13.1 s starting after 262144 points or 209.6 s with
                       52.4 s with f =1250 Hz). The line near 200 Hz is the CW                                                                       fs=1250 Hz). The broadband signal being projected by the
                                              8                                                                                                      source (approximately 100-300 Hz) is easily seen in the surface
                       signal projected by the source at the beginning of each tape.                                                                 reflected and direct path beam spectra. The additional
                       Figure 3 is vertical arrival structure of this CW signal as                                                                   bandwidth apparent (300-400 Hz) is due to a resonant peak in
                       calculated by a FFT beamformer. The direct path arrives at                                                                    the HX-90 compensating for the lowpass roll-off
                       approximately -10                     and the surface reflected path arrives at                                               characteristics in the source signal generation network.
                       approximately -16                        Note that the surface reflected path
                       arrival is on the order of 1.5 dB lower in level than the direct                                                                       Similar to Figure 6, Figures 7-8 also display power
                       path arrival.                                                                                                                 spectra at the output of time-delay beamformer beams. In
                                 Figure 4 displays power spectra from hydrophones                                                                    both cases, the top panel corresponds to the tow ship arrival
                       20, 40, and 55 calculated during the fifth segment of Tape                                                                    (-13.1 ' ) which is used as the reference input to the adaptive
                       07052 (65536 points or 52.4 s starting after 262144 points or                                                                 filter. The bottom panel in Figure 7 corresponds to the direct
                       209.6 s with f =4250 Hz). A broadband signal is being                                                                         path arrival (-10.2' ) beam formed from the array element
                       projected by tshe source (approximately 100-300 Hz) at this                                                                   time series after adaptive cancellation. It differs little from
                       time but it is not easily seen in the single hydrophone spectra.                                                              the same beam in Figure 6 which has not had adaptive
                                                                                                                                                     cancellation applied to the element time series. In contrast,
                                 Figure 5(a) displays broadband vertical arrival structure                                                           the bottom panel in Figure 8 corresponds to the time series
                       as calculated by a time-delay beamformer where the input                                                                      from array element * after adaptive cancellation. Note the
                       element signals have been bandpass filtered to 100-300 Hz.                                                         A          significant difference between this power spectrum and the
                       slice in the waterfall represents 256 beam power estimates                                                                    power spectrum from the same element prior to adaptive
                       where the output of each beam has been averaged over 64                                                                       cancellation which is displayed in Figure 4 (top panel).
                       points in time. The entire waterfall represents only 1.6 s in
                       time. Note the severe contamination of the display due to the
                       tow ship arrival (-13.1 *). Figure 5(b) displays the same data
                       after adaptive removal of the tow ship contamination. The                                                                                                                 M Summary
                       adaptive processing was accomplished by treating the time
                       series obtained at the output of the beam pointing at the tow                                                                           This paper has focussed on the use of adaptive n                                            Ioise
                       ship (properly delayed to account for propagation delay across
                       the array) as the reference input to a simple adaptive noise                                                                  cancellation techniques to remove tow ship contamination
                       cancelling structure with each hydrophone time series (in                                                                     from array element time series. A broadband beam pointing
                       turn) treated as the primary input. In this case, the JCLSL                                                                   at the tow ship was formed and used as the reference input to
                       parameters p (number of adaptive stages) and a (adaptation                                                                    a least-squares lattice adaptive noise canceller. Each
                       rate parameter) were set to p = 8 and a = 0.02. The                                                                           hydrophone time series (in turn) was treated as the primary
                       contamination-free individual element signals then were                                                                       input. The contamination-free individual element signals then
                       bearnformed yielding the results in Figure 5(b). The ability to                                                               were beamformed. The results indicate removal of the
                       remove the tow ship contamination from the individual                                                                         contaminating tow ship signature while preserving the
                       element signals is important in order to calculate meaningful                                                                 broadband transmission from the towed source.
                       cross-correlations between pairs of hydrophones.
                                           d
                                              0  n

                                               d
                                                  n

                                     d                                                                                                                                                                                                 d
                            tK
                                                                                                                                                                       @7K

                                                                                                                                            311

                         Acknowledgernents                                                                                                                                        References
                                 This work was supported by the Naval Air Systems
                         Command and the Office of Naval Research under contract                                                        [11     W.S. Hodgkiss and D. Alexandrou "An Adaptive
                         N00014-87-C-0127. Dr. Fred Fisher was chief scientist during                                                           Algorithm for Array Processing," IEEE Trans. Antennas
                         the experiment.                                                                                                        and Propagation, AP-34: 454-458 (1986)
                                                                                                                                        [21     D. Alexandrou, "Boundary reverberation rejection via
                                                                                                                                                constrained adaptive beamforming," J. Acoust. Soc. Am.
                                                                                                                                                82(4): 1274-1290 (1987).
                                                                                                                                        [3]     D. Lee, M. Morf, and B. Friedlander, "Recursive Least
                                                                                                                                                Squares Ladder Estimation Algorithms," IEEE Trans.
                                                                                                                                                Acoust. Speech. Signal Proc., ASSP-29: 627-641 (1981)
                                                                                                                                        [41     B. Friedlander, "Lattice Filters for Adaptive
                                                                                                                                                Processing," Proc. IEEE 70: 829-867 (1982).
                                                                                                                                        [51     B. Friedlander, "Lattice Methods for Spectral
                                                                                                                                                Estimation," Proc. IEEE 70: 990-1017 (1982)-

                                                                 rum

                                                      80

                                                      60

                                                      40
                                                      0     50      100    150     200      250      300     350    400     450     5@      5@      6@

                                                            1 20                                 Fr.* -y ft)
                                                      80                                                                                                                Figure 2. Power Spectra: Tape 07052.1.
                                                      60                                                                                                                          FFT 13in Width = 153 mHz.
                                                      40                                                                                                                          Calibration: dB//,uPa/*%/Hz.
                                                                                                                                                                                  Channels #1, 20, 40, and 55.
                                                      a     50      13D    150     2W       2%       3W      Y10    400     450     sm      550     bw
                                                            1 40                                 F-q-V N.)

                                                      '0

                                                      6
                                                      4:

                                                      0     50      100    150     280      250      300     350    400     450     500     550     6W
                                                            el 55                                Freq@y (Hz)
                                                      80 lit

                                                      40-

                                                      0     50      100    150     20e      250      300     Y-0    400     450     W       550     600
                                                                                                 FreqxmN (Hz)

                                                      Array RErsponGe        87052. L    Bfn #5416
                                                      1     201.26 Hz, KB indow           alpha      1.5 (above), rect wmdow (be]

                                                                                                                                                                         Figure 3. OW Signal Vertical Arrival
                                             S - 20                                                                                                                               Structure: Tape 07052.1. Sea state
                                                                                                                                                                                  5. Wind speed 18 kn. 19 March
                                                                                                                                                                                  1087, 03:50 GMT. FFT Bin Width
                                                                                                                                                                                  153 inHz. Kaiser-Bessel (a = 1.5)
                                                      -40                                                                                                                         and rectangular shading functions.
                                                      -90   -80 -70 -60   -50 -40 -30 -20 -10            e   10    20   30     40   50     60   70  60    90                      Positive angles refer to downward
                                                                                                                                                                                  looking beams. Calibration:
                                                                                                                                                                                  dB//IiPa/'\/HzDeg.

                                                      0

                                              9-20
                                                      P     Spect         ?052

                                                      -40
                                                      -90 -80 -70   -60 -50 -40      -30 -20 -10         8   10    213  30     40   Se     60   7e  80    90

                                                                                                     ANI. (dg)

                                                                                                                                   312

                                                                             @er Spectrm     8?052.5
                                                                                 a] O'l

                                                                        60
                                                                        40

                                                                             0    50     100            200     250    300     350   400     450      0     550     600
                                                                                 el f2O                             Fre*wry IHz)

                                                                        80

                                                                        60

                                                                        40

                                                                             0    50     lee    150     200     250    UO    . 350   400     450     500    550     600
                                                                                 el 40                              F-M-N (HA

                                                                        be

                                                                        40

                                                                             0    50     100    150     200     250    3M      350   40D     450     500    550     600
                                                                                 al -55                             Freq,-y (M

                                                                        80

                                                                        60

                                                                        40

                                                                             0    50     lee     150    200     250    300     35e   400     450     5M     5W      6M
                                                                                                                    Fr.q.n (Hz)

                                                                             Figure 4. Power Spectra: Tape M7052.5. FFT Bin Width = 153
                                                                                    mEz. Calibration: dB//,uPa/\/Hz. Channels #1, 20, 40,
                                                                                    and 55.

                            Rr-roy Response         87052.5 t           0 E;                                                      ArroV Pesponse - 87052. 5 1 z 0 s
                           Bundpuss FEI-tered. le@-300 Hz                                                                         Bondposs Filtered, 100-300 Hz

                                                                                                                          2

                     'F
                                 -40      -35     -30      -25               -15        L                                               40                                                                     0
                                                                                                                                                35      -301     -25        0'    45'      40'      '-5
                                                              Angle (deg)                                                                                           Angle (deg)

                      Figure 5a. Broadband Vertical Arrival Structure: Tape jW7052.5.                                       Figure 5b. Broadband Vertical Arrival Structure: Tape *87052.5.
                              Bandwidth: IOG-300 Hz . -Positive angles refer to downward                                            Bandwidth: 100-300 Hz. Positive angles refer to downward
                              looking beams. Uncalibrated. Before removal of tow ship                                               looking beams. Uncalibrated. After adaptive removal of,
                              contamination (-13.1 * arrival angle).                                                                tow ship contamination (-13.1 * arrival angle).

                                                                                                                    313

                          r     trum  87052.5
                         1BE!                              [0 014, A A
                     80                                         IT P w-r- I' I -r-

                     60 --

                     40

                                50  1 0    150  200    250    300   350     400   450    500   550     600

                                                                    Z)
                                                                    j          LIP'., Wj J,,J  LA A M
                     Be                                             NIV     PIT 17 1 f, ITV I N, IM 11' V Y07       re 6. Power Spectra: Tape 07052.5.
                                                                                                                      FFT Bin Width = 153 mHz.
                     60                                                                                               Calibration: dB//IiPa/%/Hz.
                     40                                                                                               Beams -16.6 * (source surface
                                                                                                                      reflected path), -13.1 * (tow ship),
                                510 100    150  200    250     300  350     400   450    500   550     @O             and -10.2  (source direct path).
                         Bearn                                  -9 @(H?)

                     60

                     40

                         0      50  100    150  200    250     300  350     400   450    500   550     600

                                                           Frequency (HA

                                S ctrum ?0 2.5

                         Be

                     80

                     60
                     40                                                                                          Figure 7. Power Spectra: Tape 07052.5.
                                                                                                                      FFT Bin Width = 153 mHz.
                                50  100    150   200    250    300     350  400    450   500     550   600            Calibration: dB//pPa/N/Hz.
                                                                                                                      Beams -13.1 * (tow ship) and -10.2
                                                                                                                      (source direct path) (after removal
                     80.                                                                                              of tow ship contamination)-

                     60

                     40

                         0      50  100    150   200    250    300     350  400    450   500     550   600

                                                            Frequency (Hz)

                                S ctrum - P705g.5

                     80                                                        FTVPJ IRRIVr I NI 44" 7"1 YN

                     60
                     40                                                                                    T     Figure 8. Power Spectra: Tape M7052.5.
                         0      50  100    150   200    250    300     350  400    450    500    550   600            FFT Bin Width = 153 mHz.
                                                                                                                      Calibration: dB//,uPa/\/Hz. Beam
                                                            Frequency (Hz)                                            -13.1 * (tow ship) and Channel #1
                                                                                                  i      i            (after removal of tow ship
                     80                                                                                               contamination).
                  &  60

                     40
                     @r 4tru-       8 @11125

                         S, 4S@r t r u     052.
                                      7"

                            4S&j,.t;u.   705 -5

                         0      50  100    150   200    250    300     350  400    450    500    550   600

                                                             Frequency (Hz)

                                                                                  314

                                  A NEW ACOUSTIC TECHNIQUE FOR REMOTE MEASUREMENT OF THE TEMPORAL OCEAN WAVE SPECTRUM
                                                    R.J. Lataitis, G.B. Crawfordl, and S.F. Clifford

                                                              Wave Propagation Laboratory
                                                    National Oceanic and Atmospheric Administration
                                                          Environmental Research Laboratories
                                                                      325 Broadway
                                                                   Boulder, CO 80303

                                   ABSTRACT

               A method is described that uses low-frequency
               sound (< 200 Hz) to measure the waveheight
               variancZ and the nondirectional temporal
               waveheight spectrum of a random rough surface
               such as the sea surface. The technique requires
               a vertically pointing broad-beam acoustic source
               and a colocated receiver that records the
               amplitude and phase fluctations of the back-
               scattered field. When the rms surface
               waveheight is much smaller than the acoustic
               wavelength, the temporal spectrum of the
               backscattered amplitude and phase fluctuations
               can be directly related to the nondirectional
               temporal surface waveheight spectrum.
               Typically, surface waves with wavelengths of a
               few meters or more can be probed, and the
               corresponding temporal waveheight spectrum out
               to frequencies of roughly I Hz can be retrieved.

                                1. INTRODUCTION
                                                                        Figure 1. A decomposition of the sea surface
               The temporal structure of the sea surface is             into its spatial Fourier components. (Pierson,
               usually measured using buoys and/or wave                 et al., 19551).
               staffs. A variety of acoustic techniques are
               also gaining popularity. These usually involve           The actual sea surface is the superposition of
               measurements of the backscattered power or               all surface wave components of different
               Doppler spectra, both of which contain surface           amplitudes, wavelengths, and propagation
               wave information. We describe an alternative             directions weighted by the directional surface
               method in which a single broad-beam source is            waveheight spectrum. Provided a  @ << X, each
               used to insonify the sea surface from below and          surface wave component produces a sinusoidal
               a colocated receiver is used to detect the               perturbation in the amplitude and phase of the
               amplitude and phase fluctuations of the back-            backscattered field2 as shown in Fig. 2.
               scattered field. The temporal statistics of the
               amplitude and phase can then be used to extract
               the temporal statistics of the sea surface pro-
               vided the rms surface waveheight ce << X, where
               X is the acoustic wavelength. The method is
               simple, it requires little signal processing,
               and it should provide an accurate measure of the
               nondirectional temporal waveheight spectrum over
               a broad range of frequencies.

               This method is best described by first
               considering the Fourier decomposition of the sea                      2V'
               surface illustrated in Fig. 1.  Each surface                                  2A
               wave component is a two-dimensional sinusoidal
               waveheight perturbation of a given amplitude and         Figure 2.  A point source of sound  insonifying a
               wavelength propagating in a particular direction.        single Fourier component of the sea surface.
                                                                                     2V

                                                                                             2A

               1G.B. Crawford is currently with the Department of Oceanography, University of British Columbia, Vancouver,
               British Columbia, Canada V6T IW5.

                                                  CH2585-8/88/0000- 315 $1 @1988 IEEE

                  For a sinusoidal surface wave component with a               where w = 2wf, Se(w) is the nond recti nal
                  spatial wavelength A and propagation velocity                temporal surface wave spectrum, tF(K)i  2 is the
                  V', the backscattered amplitude and phase                    transfer function relating the amplitude of a
                  perturbation pattern in an observation plane at              surfne wave component with wavenumber
                  the source is also sinusoidal and has a spatial              K = IKI - 2w/A to the amplitude of the
                  wavelength 2A and a propagation velocity 2V1.                correspondingFourier component of the
                  The factor of two is due to the diverging nature             backscattered wave perturbation pattern, and g
                  of the spherical wave field.    The perturbation             is the gravitational acceleration at sea
                  in the backscatter field is therefore merely the             level. The details of the derivation leading to
                  projection of the surface wave onto the                      Eq. (1) are presented by Lataitis et al.,3 and
                  observing plane. The amplitude of the                        are not repeated here. Their approach is based
                  perturbation is proportional to the amplitude of             on a perturbation expansion for the back-
                  the surface wave. The full backscattered                     scattered field presented by Labianca and
                  amplitude and phase perturbation pattern is the              Harper4, and a method for relating the acoustic
                  superposition of the fields scattered from all               wave to the surface wave fluctuations presented
                  of the surface wave components. In the same way              by Fuks.5 Equation (1) requires that I << kz,
                  as a buoy or wave staff measures the temporal                14a @ A, that the surface be in the Fraunhofer
                  structure of the surface by detecting the                    regfon of the source I and that the first order
                  waveheight fluctuations of each surface wave                 dispersion relation 12    gK hold for the surface
                  component as it propagates by, a single receiver             waves.
                  measures a proportional quantity by detecting
                  the corresponding amplitude and phase
                  fluctuations in the backscattered field as they
                  propagate by. We note that the frequency f
                  detected by a buoy at the surface (i.e., f - V'/A)
                  is the same as that observed at the receiver
                  (i.e., f = 2V'/2A), so that there is a one-to-
                  one correspondence between the frequency induced
                  at the surface and the frequency observed by a
                  remote receiver.

                  This paper examines the theoretical limitations
                  of this technique.   In particular we present an
                  expression for the transfer function that
                  relates the spatial structure of the surface to
                  the spatial structure of the backscattered                                                             466:0
                  amplitude and phase perturbation pattern. By
                  using the first order surface wave dispersion
                  relation we determine the range of surface wave                                        01
                  frequencies that can be observed with this                                            Z
                  technique.

                                2. THEORETICAL RESULTS

                  Consider the backscatter geometry shown in
                  Fig. 3.  A point source of sound is located a
                  distance z below the plane of the mean
                  surface. The surface waveheight E describes                  Figure 3. Scattering geometry
                  excursions of the surface about its mean level
                  and is a tunction of time t and the transverse               Equation (1) relatts the observed log-amplitude
                  position pl in the mean plane defined from the               and phase spectra C(w) of the backscattered
                  origin of coordinates located directly above the             field to the surface wave temp ral srctrum
                  source. We assume that the maximum frequency of              SESw). The transfer function IF(K)I is given
                  oscillation of the surface is much less than the             by
                  source frequency wo = kco, where k = 27/X and co
                  is the sound speed. We also assume that the                        IF(K)I' = IF (K)I 2 + IF (K)I 2,              (2a)
                  waveheights are sufficiently small so that the                                   X           S
                  scattered acoustic signal will be a narrow-band              where
                  process about %. The backscattered amplitude                                   3            J (Kp')
                  and phase fluctuations are recorded by a                           FX(K) = 2kz               0
                                                                                                    f dP'P'    2  _2
                  colocated receiver.   The sum ZM of the      power                  S             0       (p, +  z )2 1(p')
                  spectra of the log-amplitude and phase                                            Cos
                                                                                                              P7@2
                  fluctuations, where the log-amplitude is     the                                 x      [2                       (-2b)
                  natural logarithm of the amplitude normalized to                                  sin
                  the mean amplitude, is given by3                             In Eq. (2b) the integration is over the mean
                                  2              2    12,                       urface plane, Jo is the zero order Bessel
                        CM - 4k S    (W)IF(K - W /g)                           Iflunction, and I is a function describing the
                                                                               acoustic beam pattern at the surface. For a
                                                                               simple Gaussian beam pattern function
                                                                                                                          66" 0

                                                                         316

                                    _P'  2/(2z2 tan 29)
                         I(p') = e                                            (3)       between the temporal surface wave spectrum and
                                                                                        the measured power spectra of the amplitude and
                 where 0 is the half-beam width of the source or                        phase fluctuations of.the backscattered field
                 receiver whichever is narrower, Eq. (2) can be                         was presented. Our results indicate that the
                 evaluated using straightforward stationary phase                       surface wave temporal spectrum can be retrieved
                 techniques. For kz >> I we obtain          3                           for angular freque2cies W sajisf        Mg
                                              2       2       2                         0 < W < Y"2-kg [2tan e/(1+2tan 0)]          . As an
                   IF(a)  12     (1-a 2) 2e- a /[(l-a ) tan         a < 1, (4a)         examplZ we consider a situation where
                                    0                               a > 1, (4b)         a - 0.5 m typical ofa bay, inlet, or coastal
                                                                                        rigion. A system with X - 7m mounted at a depth
                 where a      K/2k. Equations (4) are plotted in                        of say 10 or 20 meters could continuously
                 Fig. 4 for kz =      60 and 8 = 90* (i.e., an                          monitor the surface wave temporal spectrum over
                 isotropic source), 0         45% and 0        15%                      frequencies 0 < f < 0.6 Hz provided a beam width
                                                                                        of 45' was used. We feel that this technique is
                                                                                        a simple, attractive alternative to existing
                          100                                                           methods for monitoring the temporal behavior of
                                                                                        the sea surface.

                           10
                                                                                                           4. ACKNOWLEDGMENTS

                                                                  0=90*                       This work was supported by the Office of
                                                                 0=45'                  Naval Research under Contract NOO014-0090.
                           0.1-
                                                                0 =150                                        5. REFERENCES
                         0.01-                                                          1 .  Pierson, W.J., Jr., Neumann, G., and James,
                                                                                             R.W. (1955). Practical Methods for
                       0.0011                                                                Observing and Forecasting Ocean Waves by
                            0.01             0.1                            10               Means of Wave Spectra and Statistics, (U.S.
                                                     a                                       Navy Hydrographic Office, Pub. No. 603)
                 Figure 4. The transfer         function IF(o,)12 defined                    p. 24.
                 in Eq. (2) plotted as a        function of a = K/2k for                2.   Lee, R.W., and Harp, S.C. (1969). "Weak
                 kz = 60 and various values of the half-beam width O@                        scattering in random media, with appli-
                                                                                             cations to remote probing," Proc. IEEE, 57,
                 The significance of the cut-off at K = 2k in                                375-406.
                 Fig. 4 for an isotropic source is that surface
                 waves with higher wavenumbers produce scattered                        3.   Lataitis, R.J., Crawford, G.B., and
                 waves that are evanescent and decay within a few                            Clifford, S.F. (1988). "A simple low
                 wavelengths of the surface. Therefore there is                              frequency acoustic technique for remote
                 no information about these         shorter surface waves                    measurement of the temporal ocean wave
                 in the backscattered field         at the source. We                        spectrum," (submitted to Jour. Acoust. Soc.
                 note also that the cut-off         frequency decreases                      Am.).
                 as the beam width narrows. This is due to the
                 reduction of the effective         field of view of the                4.   Labianca, F.M., and Harper, E.Y. (1977).
                 system which filters the contribution of the                                "Connection between various small-waveheight
                 shorter surface waves. This filtering occurs                                solutions of the problem of scattering from
                 because the shorter surface waves scatter the                               the ocean surface," J. Acoust. Soc. Am., 62,
                 incident acoustic field into larger angles and                              1144-1157.
                 eventually out of the systems,field of view. We
                 can identify the shortest surface wave from                            5.   Fuks, I.M. (1975). "Determination of the
                 which we can extract useful information by                                  parameters of ocean waves from amplitude and
                 determining where the curves in Fig. 4 fall to                              phase fluctuations of reflected radiowaves,"
                 say e 2 of their value at a = K/2k = 0.              From                   Izv., Atmospheric and Ocean Physics,lb
                 Eq. (2b) we find that this occurs when                                      1038-1046.
                 K = 2k[2tan20/(1+2tan20)]1/2. Using the first
                 order surface wave dispersion relation, this
                 translates to an Iservable         5 reqy7@cy band
                 0 < w < /2kg [2tan 0/(1+2tan 0)]

                                       3. DISCUSSION

                 We have described a simple acoustic technique
                 that uses a single broad-beam source and a
                                             7 e

                 colocated receiver to remotely monitor the
                 nondirectional temporal surface wave spectrum.
                 A transfer function describing the relationship

                                                                                 317

                                           ATTENUATION OF LOW FREQUENCY SOUND IN OCEAN SURFACE DUCTS:
                                                       IMPLICATIONS FOR SURFACE LOSS VALUES

                                                     David G. Browning and Peter M. Scheifele
                                                          Naval Underwater Systems Center
                                                               New London Laboratory
                                                           New London, Connecticut 06320

                                                                  Robert H. Mellen
                                                                Kildare Corporation
                                                           New London, Connecticut 06320

                                       ABSTRACT                                                   BACKGROUND

                The attenuation of low frequency sound in the sea            For a typical deep ocean sound speed profile,
                is pH-dependent, i.e.,      the higher the pH, the           various   modes   of   propagation   will     dominate
                greater the attenuation. In most ocean areas, the            depending on the depth of the sound source (Fig.
                value of PH changes significantly with depth so              1). sound fixing and ranging (SOFAR) propagation
                this must be included in an accurate attenuation             centers along the principal sound channel axis,
                computation.    Previous determinations of other             surface duct propagation along a surface layer,
                parameters, such as surface loss which were based            while convergence zone (CZ) propagation covers a
                on   older    attenuation    formulae,    should     be      major portion of the water column.
                reexamined. An analysis of a previously reported
                surface loss formula indicates the predicted                 Previously the same value(s) of attenuation had
                values are too high.                                         been used for all propagation modes [7], but as
                                                                             can be seen from a representative deep water PH
                                     INTRODUCTION                            profile,     different   propagation    modes     will
                                                                             experience different values of pH (Fig.            2).
                Nothing is more fundamental to sound propagation             Generally, the surface duct mode will see the
                in the ocean than the attenuation of sound in sea            highest PH and, hence, the highest attenuation;
                water. Depending on the propagation path, some-              the pH minimum is near the sound channel axis,
                times there is bottom loss, sometimes there is               thus, SOFAR propagation will have the lowest
                surface loss, and sometimes there is reverbera-              attenuation. CZ propagation will be somewhere in
                tion, but every time there is attenuation.                   between..

                Since the discovery of a new low frequency                                COMPUTATION OF ATTENUATION
                attenuation mechanism in 1965 (1], our knowledge
                has   rapidly evolved     (2]   to a comprehensive           The comprehensive attenuation formula for sea
                attenuation formula [3] based on three relaxation            water is based on three chemical relaxation
                processes of which two are pH-dependent. As a                processes:    boric    acid    (B(OH3),     magnesium
                result, the higher the value of pH, the higher               carbonate    (MgC03),    and    magnesium      sulfate
                the attenuation [4].                                         (MgS04) (see Fig. 3). The first two mechanisms,
                                                                             which are significant    at low frequencies, have
                The purpose of this paper is to present the                  been    recently    discovered     and    are     both
                impact of the latest attenuation formula on                  pH-dependent.
                surface duct propagation loss predictions and to
                revise values of low frequency surface loss [5)              The pH-dependency can be expressed in terms of a
                that were previously obtained from surface duct              "K" factor, and plots of K contours will indicate
                propagation loss measurements and are based on               the relative change of attenuation. Two examples
                older attenuation formulae [6].                              are given in Fig. 4 showing K contours at the

                                                                                                                   E

                                                                                              SOFAR MODE

                              SOUND                                                           CONVERGENCE ZONE
                               SPEED                                                           (CZ) MODE
                              PROFILE
                                                                                              SURFACE DUCT MOD

                                                Fig. 1. Sound speed profile, propagation modes

                                                                        318 United States Government work not protected by copyright

                                           0

                                           2                                                                         0

                                   Ui

                                           3                                                                              0 N. PACIFIC
                                                                                                                          0 N. ATLANTIC
                                                                                                                         Z@ IVIED. SEA
                                                                                                                             ARCTIC
                                           4 t
                                             7.6                        7.8                 8.0                     8.2                     8.4

                                                                                            pH
                                                                    Fig. 2. Typical deep ocean pH profile

                                                                  A    Al (M9SO4) + A2(B(OH)3) + A3(M9CO3)

                                                                                                f2f /(f2 + f2)
                                                                             A, = (S/35) an        n          n

                                                                  a, = 0.5 x     10-D(krn)/20         1      50 X 1 OT160
                                                                  a2 = 0-1   X 10(pH-8)               1`2 = 0.9 X 10T170
                                                                  a3 = 0.03 x     1 &H-8)             f3 = 4.5 x    1 OT130

                                                                                  I    K  = 10(pH-8)

                                                                  3-COMPONENT ABSORPTION MODEL

                                                                    DEFINE K FACTOR AS: K=10(pH.8)

                                                                           Fig. 3. httenuation formula

                                                                                            319

                                                      1:?                        ISOUnd-Channel Confou                                                                                          ISurface    onfou
                           so                    >1.2                                                        __j                   60

                                                                                                                                                         1.9

                                          1.0
                           30                   0.9                                                                                30 --\40             <2.0                       T\        -

                                                     0.8                               >_0'6                                                                                                  @1.6
                                                                                           0.7                                                                                                  1.7
                           0                                                                                                       a                        1.9
                                                                 >0.6                         0.8
                           30                                  0.7                                                                 30

                                                                                                                                                               1.8          1.7
                                                                                                                                   so                                             I           [ @=i6
                           90           60         30           0          30           60         90           UO                 90        .1     __30              0          30           60          90          120

                           60                                     @0.7                                                             60                 4__            -1.6          -

                                                            0.6                                                                                                          1.8

                           30                                      >01                                                             0
                                                                                                                                                                   !@2.0
                                                                                                     L

                                                                                                                                   0
                                  V                                  0.e   0.7                                                                                                                  N-E-j7'
                                0.8           I-N
                                                                                                                                   30                     K

                                                                     0.9

                           so                                                                                                      so
                                       120         ISO         160         150         120          90..         so                90        120         150         ISO         ISO          120          90          so
                           Fig. 4. Attenuation contours: Sound channel axis                                                              Fig. 5.        Attenuation contours: Surface

                           sound channel axis and Fig. 5 shows K contours at.                                                      attenuation that, at that time, only included the
                           the surface. The previously used Thorp Formula                                                          magnesium sulphate,relaxation.
                           corresponds - to a value of K=l, so, as can be
                           seen, this would be a low estimate for most                                                             The original propagation loss data from AMOS
                           near-surface calculation, high for some SOFAR                                                           appears to have faded into history, but if we
                           propagation.                                                                                            assume a duct thickness of 60 m and a corre-
                                                                                                                                   sponding skip distance (limiting ray) of 6.3 km,
                           To     illustrate            the        application              of      the       new                  we can work backwards.                        By adding the old
                           attenuation formula to surface duct propagation,                                                        attenuation loss to the surface loss formula to
                           a calculation is made for a duct In the Bismark                                                         get the total loss, we can present a rate-of-loss
                           Sea (8] and the result compared to experimental                                                         versus frequency comparison (Fig. 7) which shows
                           measurements (Fig. 6). The agreement is good                                                            the surface loss rate for various wave heights on
                           whereas        calculations using                     an average value                                  the top, then the new attenuation, and below that
                           (Thorp formula) would be low, and calculations                                                          the original attenuation. You can visualize the
                           done      before          approximately               1970,        which          used                  correction as the difference between these last
                           attenuation formulae without any low frequency                                                          two attenuation curves, and, very interestingly,
                           mechanism at all, would be significantly too low.                                                       this difference curve has the same shape as the
                                                                                                                                   rate-of-surface loss curves.
                                            RECALCULATION OF SURFACE LOSS
                                                                                                                                   We can, therefore, revise the formula for surface
                           in 1968 Schulkin [6] developed an expression for                                                        scattering as follows:
                           surface loss based on surface duct measurements
                           taken during the Acoustic, Meteorological, and                                                                         As = 1.0 (Fh)1/2 dB/bounce.
                           oceanographic survey (AMOS) cruises, i.e,
                                                                                                                                   Again we cannot claim that this is definitive
                                              As = 1.6 (Fh)1/2 dB/bounce,                                                          because we do not have the original data but it
                                                                                                                                   is certainly a reasonable estimate of the impact
                           which was determined using the Marsh-Schulkin                                                           that the new attenuation formula has on the
                                                                                                                                   calculation.

                                                                                                                      320

                            (dB/kM)
                       A                            BISMARK SEA pH 8.3 300C
                                                    SURFACE DUCT,&z        90m

                                        DIFFRACTION            A2

                                                                               Al 10-      --K A3

                      .01
                                                                                                        10
                                                          FREOUENCY (kHz)
                                           Fig. 6. Bismark Sea attenuation: surface duct

                                     (dB/km) SURFACE DUCT
                                    Az = 60 m
                                    pH 8.3 250C
                                                                 h(m)
                                                                    2
                          E                                         1           oo

                                                                    .5

                          0
                          _j
                          U.
                          0
                          w

                                                             NEW a                    OLD a

                            .011
                                                                                                     10
                                                        FREOUENCY (kHz)
                                                     Fig. 1. Rate-of -loss plot
                                                                               A@/

                                                                                        00-

                                                                  321

                                       CONCLUSIONS                             3.  R. H. Mellen, P. M. Scheifele, and, D. G.
                                                                                   Browning, "Global Model for sound Absorption
                        The attenuation of low frequency sound is                  in Sea Water," NUSC Scientific and Engineering
                        pH-dependent which is depth-dependent.                     Studies, Naval Underwater Systems Center, New
                                                                                   London, CT (1987).
                        For accurate predictions, you must include
                        a depth-dependent attenuation variation.               4.  R. H. Mellen and D. 0. Browning, "Variability
                        some propagation modes are more critical                   of Low-Frequency Sound Absorption in the
                        than others.                                               Ocean: PH Dependence," J. Acoust. Soc. Am.,
                                                                                   vol. 61, pp. 704-706 (1977).
                        The computation of other parameters such as
                        surface loss should be reexamined.                     5.  M.   Schulkin,    "Surface-Coupled     Losses     in
                                                                                   Surface Sound Channels," J. Acoust. Soc. Am.,
                                                                                   vol. 44, pp. 1152-1154 (1962).
                                        REFERENCES
                                                                               6.  M. Schulkin and H. W. Marsh, "Absorption of
                  1. W. H. Thorp, "Deep-Ocean Sound Attenuation in                 Sound in Sea Water," J. Acoust. Soc. Am., vol.
                     the Sub- and Low-Kilocycle-Per-Second Region,"                34, pp. 864-865 (1962).
                     J. Acoust. Soc. Am., vol. 38, pp. 648-654
                     (1965).                                                   7.  W. H. Thorp, "Analytic Description of the Low
                                                                                   Frequency Attenuation coefficient," J. Acoust.
                  2. J. R. Lovett, "Geographic Variation        Of LOW-            Soc. Am., vol. 42, p. 270 (1961).
                     Frequency Sound Absorption in the Atlantic,
                     Indian, and Pacific oceans," J. Acoust. Soc.              8.  R. H. Mellen and D. G. Browning, "Attenuation
                     Am., vol. 67, pp. 338-340 (1980)@-                            in Surface Ducts," J. ACOUSt. Soc. Am., vol.
                                                                                   63, pp. 1624-1626 (1978).

                                                                          322

                                                        THE WIDE SWATH, DEEP TOWED SEAMARC

                                                                .Arthur St. C. Wright

                                                            Williamson  & Associates, Inc.
                                                               Seattle, Washington 98109

                                       ABSTRACT                                SeaMARC I was a deep-towed device capable of full
                                                                               ocean depth with operating frequencies of 27 and
               The advantages of sea bottom 'imagery collected                 30   kHz. It was operated          by     Lamont-Doherty
               with a deep towed system'to support geophysical                 Geological Observatory and was lost at sea in
               studies of the deep seafloor for commercial and                 1984.
               research      applications     are    frequently      not
               appreciated. Of the SeaMARC family, no two            are
               alike in terms of operating capabilities and, data              SeaMARC II is a shallow-towed device capable of 10
               output. Only the privately owned Sea MARC.IA cuts               kilometer bathymetric swaths. Operating at 11 and
               across    and supports all regimes. The             paper       12 kHz, it obtains off track depths by a phase
               discusses the use of deep towed wide swath bottom               angle measuring technique. This sonar is operated
               imaging    sonar and subbottom profiler.             Data       by Hawaii Institute of Geophysics.
               examples are presented from SeaMARC IA, a sidescan
               sonar operating at 27-30 kHz to image the seafloor              SeaMARC IA is a full ocean depth system with oper-
               in swath widths up to 5000 meters.               Acoustic       ating frequencies of 27 and 30 kHz, swath capabil-
               response of the seafloor to the sidescan       and 4.5          ities from 500 to 5000 meters and incorporating a
               kHz subbottom profiler from a wide range of envir-              sub-bottom profiler and a digital             processing
               onments are examined and the -image processing                  system. It is owned by International Deep Sea
               techniques are shown.                                           Survey,    Inc. and operated by         Williamson      &
                                                                               Associates, Inc.

                                                                               SeaMARC IB was similar to SeaMARC I and was
                                  1. INTRODUCTION                              initially purchased by Lamont-Doherty but was
                                                                               subsequently     transferred       to    Woods       Hole
               The many sidescan sonars in use today for mapping               Oceanographic Institution. It was lost at sea this
               and imaging fall into two groups; one group for                 year.
               working the shallower waters, and the second for
               working to full ocean depth for a variety of                    The SeaMARC CL-X is a smaller system               which
               purposes. The SeaMARC (Sea Mapping and Remote                   operates at 150 kHz with a maximum swath width of
               Characterization) family was one of the early                   800 meters. It was developed as an experimental
               entries in the deep ocean field. Today, the name                model in 1985 and is operated by Williamson &
               SeaMARC is almost synonymous with towed sidescan                Associates, Inc.
               deep ocean imagery or swath bathymetry. These
               devices are descendants of the HSES or High Speed               The SeaMARC S is a medium depth, production
               Exploration System which was developed by a conso-              follow-on to the CL-X manufactured for Seafloor
               rtium for manganese nodule exploration in the late              Surveys International, Inc. in 1986. SSI has deve-
               seventies. (The U.S. member of this consortium was              loped a phase angle measuring system for swath
               the International Nickel Company which is not an                bathymetry which has been integrated into this
               active participant in offshore exploration at this              system.
               time.) many of the personnel associated with the
               development of the HSES subsequently formed assoc-              In addition to complete systems, IST has also
               iations that led to the development and operation               provided    arrays and primary        electronics      to
               of the SeaMARC line.                                            customers for their own further development. In
                                                                               early 1988, International Submarine Technology
               All   SeaMARC's     have    been   manufactured       by        ceased operations and sold the rights to the
               International    Submarine Technology,        Ltd.    of,       SeaMARC line to Honeywell Inc. Reportedly, more
               Redmond, Washington. There have been two general                SeaMARC's are in process at the 146neywell plant
               types; a deep-towed imaging system, and a near                  near Everett, Washington.
               surface towed swath bathymetry system.

                                                      CH2585-8/88/00oo- 323 $1 @1988 IEEE

                  . . . .... . .. . ...-                                      A variety of navigation systems have been used
                                                                              with SeaMARC IA. Two types of positioning must be
                                                                              considered;     vessel positioning, and towfish to
                                                                              vessel    positioning.     For   vessel     navigation,
                                                                              advances in electronic and satellite navigation in
                                                                              recent    years have improved the accuracy            in
                                                                              positioning.   The increase in the number of GPS
                                                                              satellites will further increase the accuracy of
                                                                              vessel    positioning.    Determining the       towfish
                                                                              position relative to the ship can be done with a
                                                                              short baseline system, or in the situation where
                                                                              the cable length is over 10,000 feet, a manual
                                                                              calculation has to suffice. The most accurate
                                                                              method is a long baseline system in which an inte-
                                                                              rrogator    on the SeaMARC towfish         queries     a
                                                                              calibrated transponder array. This removes the
                        I L1@11                                               ship from the calculation and has provided results
                                                                              to a two meter accuracy.
                            Figure 1. SeaMARC 1A towfish                      SeaMARC IA has been to sea on vessels ranging in
                                                                              length    from    120 to 350      feet.    The    basic
                                                                              requirements are that the vessel accommodate the
                                                                              personnel and equipment and be able to maintain
                                                                              track in the sea conditions expected in the survey
                                  SYSTEM DESCRIPTION                          area.   Frequently other activities in addition to
                                                                              SeaMARC operations are planned which mandates
                 The major components of the SeaMARC IA system are            additional equipment and space integration. The
                 the towfish, cable and depressor, topside handling           ship must have sufficient room for the handling
                 equipment, surface electronics package, and data             equipment, and working area for the SeaMARC IA
                 .acquisition and processing systems.     The towfish         electronics, processing equipment, and navigation
                 (Figure 1) carries the port and starboard sidescan           computers. The personnel count varies according to
                 arrays and associated electronics, the toroidal              the    requirement for on-board -processing         and
                 ,beam pattern 4.5 kHz subbottom profiler, and                evaluation, but an average SeaMARC and navigation
                 various sensors and recovery beacons. The towfish            scientific party numbers about ten. While the
                 weighs 1600 pounds in air and is slightly buoyant;           SeaMARC IA has operated in gale conditions, the
                 it tows well at speeds up to five knots. A                   limiting factor in such adverse weather has been
                 standard 0.68 inch marine coax of up to 30,000               the ability of the ship to maintain track. Bow
                 feet connects the towfish to the winch. A 1600               thrusters have been used to advantage in some
                 pound depressor is positioned three hundred feet             circumstances and are a desirable feature.
                 ahead of the towfish to eliminate towing vessel              All the equipment except the winch and crane fit
                 heave and to mitigate the effects of pilot error.            into a twenty foot long container that is easily
                 The topside handling components are a towpoint,              road transportable and can be welded to the deck
                 which resembles a half A-frame with a gallows                of     the  support vessel for a         support    and
                 block, a hydraulic winch with level wind, and a              maintenance center at sea. If necessary the system
                 crane for towfish launch and recovery. If the                is also air transportable (but it is in the
                 support vessel doesn't have a hydraulic deck                 client's better interest to find a crane locally).
                 outlet, a diesel power pack is also necessary. The           Mobilization requires two to three days with the
                 surface electronics package contains the sonar               critical path generally involving welding.
                 controls and the analog-to-digital processors.
                 Transmit    power, receiver gain,       swath     width
                 selection, pulse burst length, and bandwidth can                      SEAMARC IA OPERATING FUNDAMENTALS
                 be controlled for each sonar. The data acquisition
                 and image processing systems consist of the recor-           Tfi&key  advantage of deep-towed sidescan sonars is
                 ders, computers, video monitors and tape and disk            that all the errors associated with the water
                 decks which are used to simultaneously record and            column effects and beam spreading are eliminated
                 process the data.                                            and the Arrays are transmitting and receiving in
                                                                              the    immediate    vicinity    of   the      "target".
                 A critical component of the SeaMARC IA operation             Inaccuracies in depth measurements caused by ray
                 is the availability of tools and spare parts so              path    bending and bottom penetration by           the
                 that any casualty short of towfish-loss can be               relatively low frequencies of surface systems       and
                 overcome. Once offshore, clients take a dim view             modulation 'of return signal characteristics by     the
                 of having to suspend an operation to return to               water column are also avoided. The philosophy of
                 port for repairs. So, included in the support                this sonar is to present the best imagery possible
                 equipment are all tools that could conceivably be            and the@ operating parameters have been selected
                 required, a replacement board for surface and                accdrding'ly. In the design phase, two desired
                 subsurface systems board, many spare hardware,               capabilities for SeaMARC IA were the ability to
                 electrical, and electronic items and a complete              image large areas of seafloor in a wide swath mode
                 library of technical publications and drawings.              and the ability to find small targets in the

                                                                         324

               narrow    swath,     high    resolution     mode.      The       Swath      Altitude       Pulse Length          Bandwidth
               flexibility offered by the variable swath widths                 meters      meters        milliseconds            Hertz
               from 500 to 5000 meters provides the seafloor
               mission planner with powerful capability. In any                  500        25-125          .15, .2, .3               5000
               areal survey, the ability to obtain an initial                   1000        25-250           .3, .4, .6               2000
               wide swath look at the target area precludes navi-               2000        50-500              .8, 1.2        1000,  2000
               gational surprises and indicates those areas which               5000       125-1250       1.2, 1.6, 2.4         500,  1000
               deserve a closer look. The ability to accomplish
               both wide area and high resolution missions with                 The  bandwidths tabulated above are related to
               the same machine saves capital costs and hours at                tuning of circuits in the electronics signal proc-
               sea in recovering and restreaming equipment.                     essing section and are not the same as the mechan-
                                                                                ical   transducer array bandwidth referred              to
               The design selection ol, frequency for a sidescan                earlier.
               sonar    is dependent on the maximum swath width
               desired. Once the frequency has been selected, the               As opposed to the resolution of a sidescan sonar
               mechanics of the transducer array construction                   in the cross-track direction being set           by its
               determine the characteristic of the resonance                    operating characteristics, the resolution              and
               curve which is assigned a value known as "Q". A                  consequently the pixel dimension along track is
               lower Q means that a wider bandwidth about the                   set by vessel speed. For a given beam width, if
               center    frequency     is    available     for     signal       the vessel moves too fast a small target may be
               processing. An important point concerning resolut-               missed. But, if the vessel moves such that each
               ion of a sonar is that high resolution is not                    point is imaged several times,         and the towfish
               dependent on high frequency but rather on pulse                  is stable in pitch, roll, and heading. Then a
               duration. A sonar puts power in the water in                     small target whose return signal is slightly
               pulses, the length or duration of which determines               higher than background will appear as a short,
               the minimum size of a discernible object and the                 sharp vertical line at the appropriate range.
               shape of which determines the sharpness of the                   (Figure 2) Therefore, the along track dimension of
               return signals. The key to a short, well shaped                  a target or feature can be calculated                 from
               pulse burst is wide bandwidth. The best resolution               knowledge of the angular dimension of the beam
             ,.of an analog signal is equal to the velocity of                  width, the range to a target, and the ship's
               sound in water times the pulse width expressed as                speed.
               time with due regard for units. In a digital pres-
               entation, the best resolution attainable is the
               physical size of a pixel in the cross-track
               direction and is equal to the swath width divided
               by the    number of pixels in the      scan   line.    For
               optimum results digital and analog resolution
               should be matched.

               In the case of SeaMARC IA, the desired maximum
               swath of 5000 meters mandated a maximum frequency
               of 30 kHz. (The lower 27 kHz on the port side
               array is for the purpose of eliminating cross-
               talk.) This selection of 30 kHz also set the mini-
               mum pulse width obtainable because the lowest "Q"
               achievable with the transducer arrays dictated a
               maximum bandwidth of 6 kHz. This converts to a
               pulse duration of 0.15 milliseconds which equates
               to a pulse width of 22.5 centimeters in seawater.
               This  22.5 centimeters is the      smallest     dimension
               that can be discriminated by the analog system. In
               the SeaMARC IA operating procedures the 0.15 mill-
               isecond   pulse duration is for highest        resolution
               on the 500 meter swath. Since there are 2000
               pixels in a scan line, the digital resolution of                 Figure 2.   Zoomed image   of a small,   hard target
               the system is 25 centimeters which essentially                               (Note the 25   cm pixels)
               matches the analog resolution.

               The altitude and control settings normally used
               for the various swath widths for the SeaMARC            IA       For good imagery, returning intensity levels must
               are:                                                             be displayed in as many shades or colors as the
                                                                                human eye can discern. The SeaMARC IA Image Proce-
                                                                                ssing System     sorts incoming signals into 256
                                                                                intensity levels and displays them in 16 shades of
                                                                                gray   or other pseudo-color. The            number     of
                                                                                intensity levels assigned to any of the 16 colors
                                                                                can be varied or "thresholded" so that specific
                                                                                portions of the returning intensity level spectrum

                                                                         325

                                                                                     PROCESSED SEAMARC IA IMAGE OF THE
                                                         _'n"::                              AXIAL CALDERA
                                   A

                                                                                      JUAN OF FUCA RIDGE -NE PACIFIC

                                                                                                    I km
                                               -W-a. @&_-

                                                       7Z,

                                                                  A,

                                          @_Z
                               %

                                                                                                                                    vi

                                                                                                        . .... . .. . ......

                             Figure 3. SeaMARC 1A mosaic of the Axial Seamount Caldera in the Northeast Pacific.
                                        The image represents 2 tracklines run with a 2 km swath width.

                  can be assessed. In signal processing terms,                 Figure 3 is a SeaMARC IA mosaic of the caldera on
                  twelve bits are reserved for each pixel, but only            top of Axial Seamount in the northeast Pacific.
                  eight bits are being utilized.                               Although the rim wall, which is up to 150 meters
                                                                               above the caldera floor, dominates the image,
                                                                               other     geomorphological    features     are     well
                                 SeaMARC IA EMPLOYMENT                         expressed. The high reflectivity of the caldera
                                                                               floor on the left-most part of the image is due to
                  As offshore oil development, cable route surveys,            fresh basalt which has probably emanated from the
                  mineral   exploration, installation       of     sensor      large fissure intersecting the rim wall in that
                  platforms,     salvage    operations     and      other      area. The small cone in the lower left may be
                  engineering projects occur in progressively deeper           still building, while the collapsed remnant of an
                  water, traditional methods of obtaining seafloor             older one can be seen just above it.
                  data are proving inadequate. The high cost of
                  ocean engineering projects and the            financial      Figure 4 is a two kilometer swath image showing a
                  penalties associated with an engineering failure             seafloor fault running upwards and to the right.
                  place a high premium on finding the optimum                  In the lower left portion, sharp spires               of
                  location for a project and evaluating all the                basaltic material which project several tens of
                  potential geo-hazards.                                       meters from the seabed. Both the fault and spires
                  Conventional   hull mounted multi-beam and      shallow      should   be  considered significant    hazards to. a
                                                                               pipeline installation, cable route or a mining
                  towed sidescan interferometric sonar systems may             operation.
                  measure water depth to an accuracy of one percent
                  and can generate contour maps       of the     seafloor      Another geo-hazard, shallow gas, is depicted          in
                  which provide general indications of depths and              Figure 5. Taken on a 500 meter swath, this image
                  slopes    but   little   information    on     seafloor      shows gassy sediment at the seafloor and free        gas
                  properties.                                                  venting from the bottom. Much of the subbottom
                                                                               detail is masked in the gassy area due to differe-
                                                                               nces in acoustic velocity.

                                                                          326

                                                                                9@1
                                                                       Towfish path

                                       @iAq 1,

                                                                                                   @t,

                                   Al

                                                                                                                                             Figure 4. Image of a fault in
                                                                                                                                                                2500 m of water,
                                                                                                                                                                recorded on the 2 km
                                                                                                                                                                swath width

                                                                    2 km swath width

                                                                                                                                                   Subbottom profile of                  methane gas

                                                                                                                                                                                                   50

                                                            Towfish        path

                                                        A,                                                                                                          ax

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                                                             500    m   swath
                                                                                            "N"

                                                                                                                                            erir;_. t-r-ii

                                Figure 5. 500 meter swath of shallow methane gas. Also shown is the 4.5 kHz subbottom profile
                                                  as the towfish crossed above the degassing area.

                                                                                                                   327

                                    CONCLUSIONS

                 Records from a deep-towed sidescan sonar and
                 subbottom profiler such as SeaMARC IA supplement
                 the information available from surface systems and
                 provide the quality data necessary to plan modern
                 seafloor engineering projects. Where additional
                 geotechnical information is necessary, the SeaMARC
                 records will indicate the most promising positions
                 for   taking core samples or      conducting     ROV
                 operations. The greater costs associated with deep
                 towed operations are minor compared to the risks
                 involved in the loss of a pipeline or cable route
                 because a fault or other geo-hazard was not
                 detected and evaluated.

                                   ACKNOWLEDGMENT

                 The authors wish to thank the National Atmospheric
                 and Oceanic Administration (NOAA), Amoco Prod-
                 uction Company, and Exxon for permission to use
                 data samples presented in this paper.

                                     REFERENCES

                 1.   Kosalos, J.G. and Chayes, D.N., A Portable
                 System for Ocean Bottom Imaging and Charting;
                 published in Proceedings of OCEANS '83, Aug. 29 -
                 Sept. 1, 1983; p. 649-656.

                 2. Kosalos, J.G., Ocean Bottom Imaging,; Presented
                 at Offshore Technology conference, May 7-9, 1984

                 3. Williamson, M.E., Application of Wide Swath,
                 Deeply Towed Bottom Imaging Sonar in Geotechnical
                 Evaluation of the Seafloor; published in Current
                 Practices and New Technology in Ocean Engineering
                 - 1988   OED-Vol. 13 by A.S.M.E.

                                                                      328

                                              A New Generation side Scan Sonar

                                                 Robert G. Asplin
                                               Carl G. Christensson

                                                 Mesotech Systems Ltd.
                                           Port Coquitlam, B.C., Canada
                              ABSTRACT                                   SOME DESIGN CONSIDERATIONS
             Side Scan sonar has traditionally used a           Operating Controls
             graphic paper recording system for the             There is a tendency to use keypads and
             display and annotation of the data. A new          displays as the operating controls for
             Side Scan system specifically designed to          much of todays electronic equipment.
             use color video as the primary data                Several reasons for this approach are:
             display is described. Several design
             considerations     and    trade-offs      are      -  there are often too many variables       to
             discussed, some of which are unique to a              control to allow the use of a dedicated
             system using a video display.                         control for each function,
             A parametric Sub Bottom Profiler and               -  invalid or illogical control setting
             towfish orientation sensors are also                  combinations can be easily prevented or
             integrated into the system.                           warned against,

                                                                -  changes or special features can be
                                                                   added requiring only software
                                                                   modifications,

                                                                -  it makes for a simple, clean looking
                                                                   control panel,
                            INTRODUCTION                        -  it is inexpensive.
                                                                The main objection to this scheme is that
             The Mesotech Model 972 is a  new Color Side        it can be very frustrating to use,
             Scan Sonar with an optional Sub Bottom             especially when the control to be set is
             Profiler function.      Some of the main           buried under several layers of menus.
             features of the system are:
             - High resolution full color display               This sonar system uses dedicated controls
               (1280 x 1024 pixels x 7 bits/pixel).             in the form of conventional rotary
                                                                switches and potentiometers for all of the
             - Tape recording/playback using standard           most often used controls.           Secondary
               VHS cassettes.                                   controls are adjusted using a software
                                                                driven menu system and a simple keypad.
             - Neutrally buoyant towfish de-coupled             Choice of a Color Display
               from ship motion.
             - Sensors in the towfish to monitor                The most desirable characteristic of the
                                                                color video display is its ability to
               depth, altitude, pitch, roll and speed.          display data with a much wider dynamic
             - Dual frequency Side Scan operation (100          range than is possible with a paper
               kHz or 330 kHz).                                 recorder system.
             - Display corrections for speed and                Images are formed on the display because
               altitude of the towfish.                         the intensity of the reflected acoustic
                                                                return varies continuously within each
             - Only two conductors required in the              shot.     If the return is too low in
               cable to the towfish.                            amplitude, it will be shown in black and
                                                                will not be visible. If the return is too
             - Operation from 110/220 VAC or 20 to 50           high in amplitude, it will be clipped to
               VDC.                                             the maximum display level and information
                                                                will be lost.

                                             CH2585-8/88/0000-329 $1 @1988 IEEE

               Therefore, there is a limited range of           PITCH: over a range of      20 degrees.
               reflected signal levels which can be
               displayed.   This is the dynamic range of        ROLL: over a range of      20 degrees.
               the display.
                                                                COMPASS (optional): magnetic heading to a
               The system used here is known as an analog       resolution of 1.4 degrees.
               RGB video system, meaning that the
               intensity of the three     primary colors,       SPEED: to a resolution of 0.1 knot.
               red, green, and blue can be independently
               controlled in very small steps.    A total       DEPTH: as measured by a pressure sensor to
               of 128 return levels can   be distinguished      a maximum range of 300 meters.
               by controlling both color  and intensity of
               each pixel on the display.         This is       ALTITUDE:   as measured by a downward
               considerably more than the 8 or 16 levels        looking echo sounder in the towfish to a
               which can be distinguished on a typical          maximum range of 250 meters.
               black and white paper recorder.
                                                                Only the speed and altitude sensor data is
               The Neutrally Buoyant Towfish                    used to make corrections.to the display.
                                                                The other sensors are provided only to
               Ideally,   the towfish would be towed            verify that the towfish is level and at
               through the water at a constant   speed and      the expected depth.
               depth with no pitch, roll,        or yaw.
               However, the towing vessel is normally           Gain Control System
               subject to surface wave action which will
               result in continuously changing tension on       Reflected return signals will vary over a
               the tow cable.                                   range of more than a million to one, much
                                                                wider   than the display dynamic range.
               Figure 1 illustrates the method used in          Much of this variation is due to signal
               this system to de-couple the towfish from        loss with increasing range.    This loss is
               ship motion.    The weighted depressor on        fairly predictable and can be compensated
               the end of the armored cable will tend to        for with TVG (Time Varying Gain)
               move up or down as cable tension changes.        amplifiers.    There are two main factors
               The neutrally buoyant towfish is not             causing the loss with range:
               subject to these upwards or downwards
               forces   since    it   is    being   pulled      1) Spreading Loss
               horizontally at the end of a neutrally
               buoyant tether.                                  2) Absorption Loss

                                                                              SPREADING LOSS
                            WINCH/TOW CABLE ASSBABLY            When the sonar pulse is transmitted from
                                                                the transducer, a fixed amount of energy
                                                                is spread over a small area of water equal
                                                                to the area of the transducer face. As
                                                                the pulse travels through the water, it
                                                                spreads out over a wider area, resulting
                                                                in less energy per unit area. The energy
                                                NEUTRALLY BOUYANT per unit area will decrease as the square
                                                SIDESCAN SONAR  of the distance traveled.      By the time
                                                EQUIPPED TOWFISH some of this energy is reflected back to
                                                                the transducer, the energy level will be
                                                                reduced by a predictable            amount
                                                NEUTRALLY BOUYANT according to how far it has traveled (how
                                                TETHER          long it. took).
                                            DEPRESSOR
                FIGURE 1: TOWFISH DECOUPUNG METHOD              This loss is compensated in the towfish by
                                                                a TVG amplifier which increases its gain
                                                                at the predicted rate of loss due to
                                                                spreading. There is only one operator
               To,wfish orientation Sensors                     adjustement for this gain correction, the
                                                                START gain.     The rate of increase is
               The towfish includes several orientation         pre-set to a 20*log(range) function and is
               sensors.     Data from these     sensors is      not adjustable.
               displayed on the screen and stored on
               tape.

               The sensors measure the following:

                                                            330

                           ABSORPTION LOSS                     This is accomplished as follows:

             As the sound pulse travels through the            a)  A fixed length command block is       sent
             water, additional energy is     lost to the           from the surface to the towfish through
             water due to an effect called absorption.             the 2-wire telemetry system.          This
             The rate of loss varies with frequency as             block includes parameters to       specify
             well as with salinity and temperature.                the frequency (120 kHz or 330 kHz) and
             This loss is expressed in db/m (decibels              the desired shot interval time.
             per meter) since it is linearly
             proportional to the distance traveled.     It     b)  The towfish will continuously repeat a
             is compensated for in the sonar by a                  cycle of    sending a    sync tone to
             second TVG amplifier whose gain            is         the surface, firing the transmitter,
             designed to increase at a constant rate    or         receiving the echoed signals,          and
             slope. This SLOPE gain can be adjusted     by         simultaneously sending a TVG corrected
             the operator either up or down from the               and frequency shifted replica to the
             default values of 0.035 db/m for 120 kHz              surface.
             and 0.065 db/m for 330 kHz.      The default
             values used are representative of data            c)  A new command block is sent only if@
             from several published sources.    They tend          one of the operating conditions has
             to vary from source to source since they              changed.
             are empirically derived values.
                                                               The towfish is fitted with sensors to
                         SYSTEM ORGANIZATION                   measure pitch, roll, depth, speed through
                                                               the water, and optionally, magnetic
             The Mesotech Model 972 Side      Scan Sonar       heading.     The information from these
             System consists of the following major            sensors is   sent to the surface in fixed
             electronic components:                            length data blocks through the telemetry
                                                               system. This occurs approximately every 2
             a) Towfish Electronics Module                     seconds.

             b) Left and Right Side  Scan Transducers                  SUB BOTTTOM PROFILER SYSTEM

             c) Echo Sounder Transducer (and optional          The sub bottom profiler system uses a
               Sub Bottom Transducers)                         technique known as parametric mixing to
                                                               generate a directional low frequency
             d) Two-Conductor Cable to  surface                pulse.    A relatively low frequency is
                                                               required to acheive penetration into the
             e) Surface processor module                       bottom material.     The higher frequencies
                                                               used by the side scan system are reflected
             f) RGB color monitor                              from the bottom surface.

             g) Tape recording system consisting of a          The sub bottom system consists of two
               PCM encoder and a VHS video tape                transmitters,      each    with    its     own
               recorder.                                       transducer, and a receiver with a third
                                                               transducer.     One transmitter/transducer
                           TOWFISH MODULE                      operates at   200 kHz while the second one
                                                               operates at  210 kHz.
             The main function of the Towfish Module is
             to collect the raw sonar data and send it         The two frequencies mix in the water
             to the surface for further processing and         producing two more frequencies, the sum
             display.                                          and difference frequencies.         The sum
                                                               frequency of 410 kHz is quickly absorbed,
             The Towfish Electronics Module contains           but the difference frequency of 10 kHz is
             the acoustic transmitters, receivers with         able to penetrate the typical bottom for a
             20 log R TVG function, telemetry receiver         few meters. The receiver is tuned to 10
             and transmitter, control processors and           kHz and receives the reflected 10 kHz
             power supplies.   It is designed to operate       signals from the bottom and layers below
             on a cyclic basis at a rate given by the          the bottom.
             surface unit rather than having to be
             triggered from the surface for each shot.         The    method     is    very     inefficient
                                                               electrically, but relatively little energy
                                                               is required. A 10 kHz transmit transducer
                                                               with the same directional characteristics
                                                               would be prohibitively large for a
                                                               towfish.

                                                           331

                               TELEMETRY SYSTEM                      g) The video display controller converts
                                                                        its memory to analog RGB              video
                The telemetry system between the Surface                signals which drive the color display.
                Processor and the Towfish module uses a
                full duplex 300 baud modem system for the            h) Sensor     data    from     the    Towf ish
                down-link command block and up-link data                Module is received and displayed
                block. Frequency division multiplexing is               numerically on video screen.
                used to send the side scan, sync, and sub
                bottom     signals      to     the    surface.       i) If   the   Speed Correction mode          is
                Frequencies used are as follows:                        enabled, the firing rate and display
                                                                        scrolling rate are        modif ied       as
                   Digital Down Link           :1170Hz                  required.
                   Digital Up Link             :2125Hz
                   Right Side Scan (Up)        :  80kHz              j) If the Water Column Removal or Slant
                   Left Side Scan    (Up)      :  5OkHz                 Range Correction mode     is enabled, the
                   Sub Bottom (Up)             :  65kHz                 digitizing     rates    are  adjusted as
                   Sync (Up)                   : 100kHz                 required.
                The   telemetry       system   signals      are      In addition to its basic function of
                superimposed on     the 48     volt DC power         displaying the realtime sonar data from
                supplied from the     surface  to the towfish,       the Towfish Moduler the Surface Processor
                thus requiring      a total of only two              will also display data from the tape
                conductors in the   tow cable.                       recording system.

                                                                                   RECORDING SYSTEM
                              SURFACE PROCESSOR
                                                                     The recording system is basically a 5
                The basic      function    of the     Surface        channel audio recorder using standard VHS
                Processor is to convert the sonar signals            video tapes as the recording media.
                from the Towfish Module into an image on
                the color display.     Several processes are         A Sony PCM encoder is used to digitize two
                involved in this function:                           channels and record them on the video
                                                                     track. Two more channels use the stereo
                a) The panel controls are sensed to                  HI FI tracks on the tape.          The fifth
                   determine the desired operation mode.             channel uses the linear tracks recorded in
                                                                     mono. Normally, a standard video recorder
                b) Appropriate commands are sen-t,-t-o the           will allow use of either the HI FI track
                   Tovufish--Module "ffo establish the correct       or the linear tracks for audio, but not
                   data collection rate.                             both at the same time.     The recorder must
                                                                     be modified to allow their simultaneous
                c) When the sonar data is received at the            use.
                   surface, a second level of TVG
                   correction is applied to compensate               on playback, the PCM encoder converts the
                   for absorption loss.                              digitized data on the video track back to
                d) The   sonar    and    sync   signals     are      two analog channels.
                   converted      to    the    audio     range       The 5 channels are assigned to the sonar
                   to     allow   them     to  be    recorded        data as follows:
                   on the external recording system.
                                                                        Left Side Scan            Left PCM
                e) The sonar signals, now in the audio                  Right Side Scan           Right PCM
                   range,     are    amplitude      detected,           Sub Bottom                Left HI Fi
                   digitized, and stored in a buffer                    Sync                      Right HI FI
                   memory.                                              Serial Data               Linear
                f) The digitized data is copied from the             The serial data consists of digital sensor
                   buffer memory to the        video display         data, Surface Processor    control settings,
                   controller by the main CPU.                       and externally input RS-232 navigation
                                                                     data.

                                                                332

                           DISPLAY CORRECTIONS                   Water Column Removal

               Speed Correction                                  In an un-corrected display, the data
                                                                 plotting is started synchronously with the
               The purpose of the speed correction mode          transmit pulse.  This means that the first
               is to control the scrolling rate of the
               display such that the vertical and                section of the display will be showing
               horizontal scales are equal.     This means       returns only from the water column. If the
               that the scrolling rate (and the 'shot'           start of data plotting is delayed by an
               rate) must change with the selected range         amount equal to the height of the towfish
               scale and also with the speed of the              'above the bottom (altitude), the water
               towfish over the bottom.                          column will not be displayed.   This is the
                                                                 water column correction mode.     It can be
               In a system using a paper recorder, it is         enabled for the side scan display and
               possible, at least theoretically, to vary         independently for the sub bottom display.
               the paper advance speed continuously to           There is one small difference with the
               compensate for towing speed variation.            water column removal in sub bottom: one
               With a video system, however, it is only          meter of water column is deliberately left
               possible to increment the display by an           in the sub bottom display.     This allows
               integer number of pixels.      Even with a        the water-bottom interface to be clearly
               high resolution display such as is used           visible.
               here, increments of one pixel do not
               provide fine enough control over the              Water column removal requires the altitude
               advance speed to make an accurate speed           of the towfish to be known.     This can be
               correction with a fixed 'shot' rate. The          taken automatically from the towfish echo
               solution used in this system is to vary           sounder or it can be entered manually   with
               the 'shot' rate in very small increments          a front panel control.
               while adjusting the display advance by
               replicating an entire row of pixels where         Water Column Removal Limitations
               necessary.
                                                                 With water column correction enabled, the
               Towfish speed through the water is                water column and any targets in the
               measured by a paddle wheel sensor in the          water column will be removed from the
               nose of the towfish. Alternatively, speed         display. They can be recovered by playing
               can be entered by means of a front panel          the tape back in the un-corrected mode.
               control, or through the RS-232 interface.
                                                                 A second limitation occurs when the
               Speed Correction Limitations                      towfish altitude changes rapidly.       This
                                                                 can be caused by a change in towfish depth
               The towfish sensor measures speed through         or bottom depth.   The altitude data from
               the water, not the desired speed over the         the towfish has a four second update rate
               bottom.   Using speed through the water,          due to telemetry.     This means that the
               however, will tend to compensate for speed        display can have jagged edges near the
               changes due to winching in or out.      Speed     bottom due to instantaneous errors in
               set from the front panel or externally            altitude.
               could be set to match an average speed
               over the ground, if known, but it would           Similarly, water column correction using
               not compensate for winching.      The speed       altitude from the panel control can easily
               correction     is   thus   only    a    good      have an altitude error.    The effect will
               approximation.                                    be to remove too much or not enough water
                                                                 column. This can be used to advantage in
               A second consideration is the fact that           some cases if it is desired to simply
               the transmitting rate is varied along with        remove most of the water column and still
               the scrolling rate    to match the speed.         see the water-bottom interface.
               The transmitting      rate can only be
               decreased from the    maximum rate for a
               given range.     This means there will be
               fewer  'hits' on a target with speed
               correction enabled. Un-corrected speed
               will always give a    maximum transmitting
               rate, and thus maximum 'hits' on a target
               for any speed.

                                                            333

               Slant Range Correction                                      MASTER/SLAVE MODES

               The side scan image plotted in the              It is possible to connect two model 972
               un-corrected mode is an image created by        processor units and two displays together
               plotting each point at its slant range          in a master/slave arrangement with a
               distance from the towfish.        This can      single towfish.     In this configuration,
               result in considerable distortion in the        the master system is the processor
               plotted size of objects very close to the       connected to the towfish.       The second
               towfish relative to those further away.         system is set to the slave mode (by means
               The slant range correction mode applies a       of a front panel switch) and is connected
               geometric correction in an attempt to           to the master by means of a master/slave
               minimize this distortion.  The slant range      connector on the rear panel.      The slave
               correction takes place in two stages:           system can then be set independently to a
               First, the water column is removed as           different display mode or even to a
               described above.   Second, the sample rate      different range.
               of the side scan is varied within each
               'shot' as a function of altitude and            The master/slave configuration thus allows
               range.  The result is a side scan image         many more display combinations.           For
               with the horizontal scale representing          example, the master can be set to show
               true horizontal distance on the bottom.         left side scan data while the slave shows
                                                               right side scan data, each using the full
               Slant Range Correction Limitations              display width.

               The basic assumption of the slant range         The master/slave arrangement can also be
               correction is that the bottom is flat and       used in the tape play back mode.
               level. Since this is not always the case,
               the correction can only be considered an
               approximation.

               The slant range correction is also
               dependent on an accurate and up-to-date
               altitude from the towfish. This is needed
               for both phases of the correction: water
               column removal and sample interval
               control. Furthermore, the altitude must
               be less than 50% of the range setting for
               the correction to work properly. This is
               seldom a limitation except on extremely
               short ranges.

                             DISPLAY FORMAT

               The display can be set to any one of seven
               different formats showing any combination
               of left side scan, right side scan and sub
               bottom data.     The full width of the
               display is used in each case.            All
               displays are in the 'waterfall'         form
               whereby new data is plotted at the top of
               the display and the older data is scrolled
               down.    Scaled range markers can be
               automatically written over the data. In
               addition, a movable cursor can be placed
               anywhere on the display area and used to
               mark targets with a unique target number.

               The bottom area of the display is used for
               the menu control system and to show the
               towfish sensor data. The current settings
               of most of the menu controlled parameters
               are also shown continuously in this area,
               even if the menu for that parameter is
               'buried'.

                                                           334

                                        USING A SECTOR-SCAN SONAR TO HUNT FOR SHIPWRECKS THROUGH ICE

                                               EMORY KRISTOF & ALVIN CHANDLER, DONALD SHOMETTE

                                              NATIONAL GEOGRAPHIC SOCIETY, LIBRARY OF CONGRESS

                                      ABSTRACT                              conventional     boat towed    side-scan   search,    we
                                                                            decided to combine the search with a new search
                    Many high tech tools are used to hunt for               technique.    We used a land survey team to layout
               shipwrecks,   side-scan    sonars   and magnetometers        a search grid on      the ice, holes were drilled
               being the main ones.        These   are usually towed        through the ice and then a sector-scan sonar was
               behind boats.     The Geographic is trying another           lowered down to within 10 feet of the bottom for a
               tool from another platform.         In Lake Champlain        look.   If a target looked worthy a larger hole was
               this winter we ran a search through the ice using            cut and a MiniRover ROV deployed.
               sector-scan sonar to look for one of the Benedict
               Arnold 1776 Flotilla.    This was done as a trial to              There are several underwater archeology pro-
               gain knowledge for $everal       searches to be con-         jects that the Geographic is considering in the
               ducted in the high Canadian Arctic.      In the remote       high Canadian Arctic and in Antarctica where use
               frozen terrain of the Arctic the cost of running             of a ship as a search platform is out of the
               a search from one of the few available ships can             question.     The   search   from  the   ice  of    Lake
               be very dear.   The.cost effectiveness of combining          Champlain was a good trial run for this impending
               a flying magnetometer search with through the ice            work.   The help of local sportsmen, headed by John
               small area searches using sector-scan sonar and              LeClair, complete with Honda all terrain vehicles,
               LCROVs is being looked at by the Geographic and              ice  fishing   shacks,   ice   augers   and knowledge
               Dr. Joseph MacInnis.       This approach is evolving         supplied the framework for the expedition.             A
               out of what was learned from the success of the              local surveyor, John Deming, laid out the grid
               BREADALBANE PROJECT.     The Lake Champlain experi-          with search holes spaced at every 200 feet.
               ment,  though not producing a shipwreck, was a
               technical success that produces another method of                 Two sector-scan sonars were used, a Mesotech
               search that will prove of use in future applica-             671 supplied and operated by Lt. Robert Gwalchmai
               tions.                                                       and  PO Robert Rheel from the Navy EOD Center at
                                                                            Indian Head, Maryland, and a UDI 500 KHZ provided
                                                                            by Chris Nicholson of Deep Sea Systems.              The
                                                                            search was conducted in water up to 300 feet deep.
                    In February of '88 the National Geographic              Given the debris on the bottom, including logs,
               conducted a search for one of the gunboats used by           and the small size of the target, the 200 foot
               Benedict Arnold to slow up the British advance               spacing on    the   holes  provided for     a   lot   of
               down Lake Champlain during the fall of 1776.         The     overlapping.    Both sonars performed well in the
               presence of Arnold's small fleet on the Lake had             February cold. The topside electronics were kept
               forced the British to take the time to assemble a            out of the weather and provided some heat.           The
               larger counter fleet.      Though Arnold's fleet was         Mesotech would fit through a six inch hole, and
               destroyed it occupied the British efforts until              the UDI required a ten inch hole.      This difference
               the winter storms of 1776 forced them to retire to           didn't matter with the one foot or less lake ice,
               Montreal till the next spring.      The time bought by       but would have to be considered when drilling
               the actions on Lake Champlain was crucial to the             through six or more feet of solid sea ice.
               success of the American Revolution.      The 50 foot,
               one-masted rowing boat that we were hunting for,                  We ran a three-man survey party out in front
               the PROVIDENCE, is a sister of the PHILADELPHIA              of two two-man ice drilling parties and two three-
               that  is  on   display    in the Smithsonian.        The     man sonar parties.    When on a roll across the ice,
               PHILADELPHIA was sunk during the Battle of Valcour           holes could be imaged with less than five minutes
               Island  and raised     in  the 1930's.      The badly        between holes.   A useful way of recording the ima-
               damaged PROVIDENCE was scuttled by Arnold the day            ges was the Sony video printer supplied by Chris
               after the loss of the PHILADELPHIA as the American           Nicholson.    Half of the search area was covered
               forces retreated to the South.                               before the ice broke up.
                    Several   side-scan   searches   have been     con-          A side trip was made to Burlington Bay to
               ducted   in  the   last    few  years   in   the    area     check out the wreck of a horse ferry from 1821.
               surrounding Schuyler Island.     Don Shomette through        The  wreck   was  relocated   using the sector-scan
               his research felt that South of Schuyler was an              technique and examined by the MKII MiniRover.        Ice
               area of high probability. Instead of running a               can be a wonderful platform from which to work.

                                                     CH2585-mmooo_ 335 $1 91988 IEEE

                 The experience gained from Lake Champlain will
                 soon be put to use in much colder and remote loca-
                 tions.

                                  OK

                                                                                                                 7-

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                                                                                                                      (Top): Surveyor
                                                                                                                I     runs a grid line
                                                                                                                      South from
                                                                                                                      Schuyler Island
                                                                                                                      on Lake
                                                                                                                      Champlain.
                                                                                                          Ir "IF      (Left): UDI
                                    AAj                                                                               sector-scan sonar
                                                                                                                      is lowered
                                                                                                                      through ice.
                                                                                                                      Cable, topside
                                                                                                                      electronics, and
                                                                                                                      generator are all
                                                                                                                      hauled on a
                            x"
                                                                                                         05           trailer behind an
                                           6
                                                                                                                      ATV.
                                                     77
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                                                                            336

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             (Top): An ice fishing shack is home for the Mesotech 671 operation, being hauled behind its ATV.
             (Bottom left): Chris Nicholson reads and records the bottom signal from the UDI sectorscan sonar inside
             an ice fishing shack. (Bottom  right): Sector scan image of horse ferry on bottom of Lake Champlain.
             Bow is pointed toward center of circle.

                                                                 337

                                SIDE SCAN SONAR ACOUSTIC VARIABILITY

                                                   John W. Nicholson                   Jules S. Jaffe

                                                     Woods Hole Oceanographic Institution
                                                            Woods Hole MA, 02543

                                   ABSTRACT                                      of a given area. Variability must also be quantified
                                                                                 if meaningful comparisons of two images of the same
                                                                                 bottom taken at different times are to be conducted.
                  This paper reports the results of research conducted           Many sources of side scan sonar image variability are
                  on the inherent variability of side scan sonar imagery         already recognized. Towfish instability is a well un-
                  in order to determine the magnitude and nature of              derstood aspect of side scan sonar which causes image
                  image intensity fluctuations. Two experiments are              distortion. The departure of the towfish from constant
                  presented in which a Klein 100 KHz system is op-               velocity and attitude result in a misdirection of the
                  erated under controlled conditions which remove all            sonar beams. This can result in a complicated shuf-
                  but purely instrumental and acoustic causes of image           fling of the acquired data which, when displayed,nor-
                  variability. The result of one experiment in a test tank       mally, produces image distortion [Flemming, 1982]. In
                  is a statistical analysis of the transmitted waveform.         this paper we will consider acoustic fluctuations. Pre-
                  A second experiment conducted from the Woods Hole              vious studies have not included side scan sonar [Urick,
                  Oceanographic Institution Pier allows similar analy-           1982]. The resulting changes in side scan images as a
                  sis for the combined side scan sonar transmit/receive          result of these fluctuations would still remain after sys-
                  signal path. The results indicate that intensity fluctu-       tematic measures had been taken to minimize towfish
                  ations are multiplicative in nature and spatially and          instability and variable imaging geometry. As such,*
                  temporally uncorrelated.                                       they represent a fundamental limit to image repeata-
                                                                                 bility.
                                                                                   In order to quantify the acoustic variability of side
                          1     INTRODUCTION                                     scan sonar returns and exclude other potential sources
                                                                                 of fluctuation it was necessary to operate a sonar sys-
                  Considering the various optical or acoustic methods            tem in a manner that permitted a large degree of con-
                  for imaging large areas of the seafloor, side scan sonar       trol. The investigation of image variability was first
                  is presently the most common. Throughout three                 subdivided into two experiments. In the first exper-
                  decades of commercial use it has been a tool for ob-           iment the acoustic transmission variability was mea-
                  taining pictures of the bottom. Although images ob-            sured so that the resultant amount of fluctuation due
                  tained by side scan sonar have always been subject             to insonification could be determined. The second ex-
                  to much scrutiny, conjecture, and interpretation, ana-         periment was devised so that repeated images of the
                  lytic treatment of the imagery has been limited. How-          same bottom were obtained.This allowed examination
                  ever with increasing use of the technique, most notably        of numerous images for fluctuations. Results of the
                  as the primary means of mapping the Exclusive Eco-             first experiment indicate what fraction of overall im-
                  nomic Zone (EEZ) of the United States [Paluzzi et al.,         age variability is due solely to transmission variability.
                  1979], technical aspects which may influence side scan         The remaining fraction is intrinsic to the acoustic en-
                  sonar imagery are receiving increased attention.               vironment.
                    One aspect which has received little attention in the
                  past but warrants analysis is the inherent variability of                     2     METHODS
                  the side scan sonar process. Knowledge of this is im-
                  portant in understanding how individual sonar targets          In the test tank experiment a Klein model 422s-10lef
                  may appear then disappear during repeated surveys              100 KHz towfish was suspended in a test tank approx-

                                                           CH2585-8188/0000- 338 $1 @1988 IEEE

                 150
                                                                                                    RESULTS

                 100-
                                                                              The test tank  experiment data was analyzed in order
                                                                              to quantify variability in the transmitted waveform.
                 50
                                                                              Figure 1 is a  plot of the pressure of the transmitted
                                                                              waveform versus time. The observed waveform con-
                  0                                                           sists of a 122 KHz carrier modulated by an envelope
                                                                              which rises linearly then decays exponentially in 100
                                                                              usec. A noticeable feature of the waveform is that it is
                 50 -
                                                                              clipped at negative pressures. This is most likely due
                                                                              transducer cavitation caused by the 228 dB re I uPa
                -100
                  0       50      100      150     200     250      300       sonar source level [Clay and Medwin, 1977).
                                      t (microseconds)                          Of particular interest is the variation of total energy
                                                                              in each transmission. Knowledge of this allows deter-
                        Figure 1: Klein 100 KHz waveform                      mination of expected image intensity variation due to
                                                                              transmission power variability. The energy of each
                                                                              waveform in the set was calculated as
              imately 5 meters from a reference hydrophone. Ge-                                          128
              ometry of the tank, towfish, and hydrophone were ad-                                 E     E An?                       (1)
              justed to prevent multipath interference and assure a                                      n=1
              fixed relative orientation of all components. Only one
              of two towfish acoustic channels was operated in or-            where the p[n] are the pressure samples of each wave-
              der to prevent mutual interference. Towfish power and           form. The statistics of this distribution are shown in
              transmit key signal were supplied by a Klein model 521          table 1.
              sonar recorder. The transmitted waveform was sensed
              by the hydrophone and sent to the data gathering sys-                                mean:              77300
              tern, which consisted of an IBM PC-AT personal com-                          standard deviation:         4900
              puter containing a Data Translation DT-2851 frame                         standard deviation/mean      - 0.063
              grabber card. The frame grabber digitized each trans-
              mitted waveform sensed by the hydrophone to 8 bits
              at 500KHz and recorded the waveforms to hard disk               Table 1:   100 KHz towfish transmit energy fluctua-
              files for further processing.                                   tions.
                 In the second, or pierside, experiment the same
              sonar system was deployed from the Woods Hole                     Having characterized the temporal variability of the
              Oceanographic Institution pier. To eliminate tow-               sonar power level, the sonar transmission was decom-
              fish motion the towfish was mounted on a steel box              posed into component frequencies for spectral analy-
              beam which spanned two concrete dock pilings 10.5               sis. The mean power in each frequency bin taken as
              M above the bottom in 17 M of water. The towfish                an ensemble average over all 3500 recorded waveforms
              was mounted level with the transducer axis oriented             density is shown in Figure 2. The predominant fre-
              20 degrees below the horizontal to minimize surface             quency is the carrier at 122 KHz with a half power
              scattering. A portion of the bottom extending 100               bandwidth of 9.2 KHz. This bandwidth corresponds
              M outward from the pier was insonified. The experi-             favorably with the manufacturers advertized specifica-
              ment consisted of recording consecutive returns over a          tion of a 0.1 msec pulselength which implies a 10 KHz
              six minute period during slack tide. It was presumed            bandwidth. A significant amount of power is seen at
              that the sonar and bottom orientation remained con-             the extreme ends of the spectrum, with local maxima
              stant during this time. The image obtained from each            at 226 KHz, 241 KHz, and at the extreme frequency
              transmission was recorded on tape and later digitized           250 KHz. This region is probably the result of the
              using the same data gathering equipment as the test             generation of harmonics of the fundamental frequency
              tank experiment.                                                due to the non-linear response of water to high am-
                                                                              plitude pressure fluctuations [McDaniel, 1965]. Lesser
                                                                              energy is seen at frequencies below 122 KHz. The local
                                                                              maximum at 65 KHz is- probably a cavitation gener-
                                                                              ated subharmonic [Desantis et al., 1967]. Broadband

                                                                         339

                      14                                                           400

                                                                                   350                        o  Gaussian Distribution
                      12

                                                                                   300-
                      10

                                                                                   250-

                                                                                   200

                                                                                   150-

                      4-                                                           100

                      2                                                             50

                      -250 -200 -150 -100 -50  0   50   100  150  200   250           0      50      100     150      200     250      300
                                          frequency (KHz)                                                  intensity

                Figure 2: Mean transmission power spectral density              Figure 4: Histogram of pixel intensity for range       bin
                                                                                200, pierside experiment

                      0.35
                      0.3                                                      sonar image of 3066 rows and 1024 columns. Here each
                                                                               row corresponds to a separate transmission and each
                      0.25                                                     column a fixed range bin. In this representation the
                                                                               image coordinates (x, r) correspond to transmission
                      0.2                                                      number and range bin, respectively. The n" column
                                                                               i(x, n) of the matrix therefore represents a time series
                      0.15                                                     of the image pixel intensity or acoustic pressure am-
                      0.1 -                                                    plitude from one independent, non-overlapping region
                                                                               of the bottom, while the n   1h row i(n, r) corresponds
                      0.05                                                     to the same quantity for the n1h transmission.
                      0             n   A -                                      The probability density function of pixel intensity
                      -250 -200 -150 -100 -50  0    50  100  150  200   25(    for a given column describes the echo stability of a
                                          frequency (KHZ)                      single object or portion of the bottom. A represen-
                                                                               tative estimated probability density function for this
                Figure 3: Variance of transmission power spectral deri-        data set is shown in Figure 4, a histogram of the 3066
                sity                                                           image intensity values contained in column 200. At
                                                                               this range a strong return is received from the bottom.
                redistribution of energy across the spectrum is also an        The figure also displays a Gaussian fit to the observed
                effect of cavitation and is observed here.                      pdf. The mean and standard deviation of the Gaussiaii
                      The variance of the individual spectral components        were assumed to be equal to the mean and standard
                is shown in Figure 3. It shows a form similar to the            deviation of the data. Compared to the Gaussian dis-
                mean power spectral density in Figure 2, with peaks             tribution, the histogram contains more points at the
                in the same areas in both graphs. However the re-               center. In general, the shape of the distribution for ar-
                gion corresponding to the carrier frequency is propor-          bitrary columns is Gaussian with a slight skew towards
                tionately smaller than the regions of significant energy        intensity values below the mean. The distributions, are
                outside the carrier. This indicates that the majority           sufficiently unlike the Gaussian distribution that they
                of observed variability in total transmitted energy is          fail the chi-square goodness of fit test [Bendat and
                found at frequencies of no use to the sonar system,             Piersol, 1971].
                since these frequencies are filtered out in the record-            The mean value of each range bin n, 1(x, n), is shown
                ing process. The ratio of power standard deviation to           in Figure 5. It should be noted that time varying
                mean power in this bandwidth is 0.0201. This is ap-             gain (TVG), a side scan sonar feature that applies in-
                proximately one third the amount of variation found             creasing gain with increasing range, was disabled in
                previously in the total energy distribution.                    this experiment. Empirically Figure 5 can be divided
                      The digitized data set obtained from the pierside         into three regions. The region nearest the towfish,
                experiment may be looked upon as a single side scan             approximately the first 100 range bins, corresponds to

                                                                          340

                     300                                                         0.25

                     250                                                          0.2-

                     200-
                                                                                 0.15

                                                                                  0.1

                     100

                     50

                     a                                                 J            0
                     0      200     400     000      800     1000      1200         0      200     400      600     800     1000      1200

                                          range bin                                                      range bin

              Figure 5: Pixel intensity mean value vs. range bin,             Figure 7: Pixel intensity Coefficient of Variation (V)
              pierside experiment                                             vs. range bin, pierside experiment

                     30                                                       is defined as
                                                                                                    V =   O'i(x,n)                   (2)
                     25-                                                                                  %'(x, n)
                     20 -                                                       The mean value of V is approximately 0.08, with a
                                                                              range from 0.04 to a peak of 0.14 which occurs at bin
                     15-                                                      400.
                                                                                To further evaluate the nature of image intensity
                     10                                                       fluctuations the joint statistics of the 1024 columns
                                                                              i(x, n) were evaluated. Of interest is the spatial cor-
                     5                                                        relation of fluctuations in different range bins. One
                     'Li                                                      technique for evaluating this correlation consists of
                     0     200     400      600     800     1000      1200    computing the correlation coefficient [Papuolis, 1984]
                                         range bin                            between pairs of range bins n, and n2. The correlation
                                                                              coefficient
                                                                                                            Orn, n2
                                                                                                 CnIn2 - @                           (3)
              Figure 6: Pixel intensity standard deviation vs. range                                       0-n 1 0-n ,
              bin, pierside experiment                                        is the ratio of the covariance of the two range bin    in-
                                                                              tensities to the product of the variances of the two
              ranges of 10 M or less and is generated by volume re-           range bins.  *
              verberation. This is because the towfish was mounted             Figure 8 is a plot of the co        rrelation coefficient
              10.5 M above the bottom. The region between range               for range bin 300 versus all range bins. Note that
              bins 100 and 600 contains the portion of the bottom             C300,300 = 1 as Would be exvected, while all othee val-
              with the most intense returns. The spiky nature of this         ues fall between +/- 0.4. This shows that the inten-
              region is due to the differences in backscatter strength        sity fluctuations of data set range  .bin 300 are weakly
              between the various bottom subregions represented by            correlated with the fluctuations in other bins.
              i(x, n). After column 600 the signal is greatly attenu-
              ated and increasingly noisy.                                     The acoustic transmission power fluctuations ob-
               .A plot of pixel intensity standard deviation o-,,, ver-       served in the test tank experiment are a possible cause
              sus range bin number is shown in Figure 6 and is seen           of the weak but wide range correlation of intensity fluc-
              to follow the same trend as Figure 5. This indicates            tuations between the various range bins in the data
              that the fluctuations in i(x, n) are a constant fraction        set. Since scattered echo intensity is directly propor-
              of the mean. This is seen to be approximately true in           tional to the intensity of the insonifying transmission
              Figure 7, a plot of the coefficient of variation V [Urick,      and all range bins during one transmission cycle are
              1982] versus bin number. The coefficient of variation           insonified by the same acoustic transmission, pixel in-

                                                                         341

                    0.8                                                               0.8

                    0.6                                                               0.6

                                                                                      0.4--
                    0.4                                                            0

                    0.2

                      0                                                                0                                      4

                    0.2                                                               -0.2

                    -0.4                                                              0.4
                      0       200     400      Boo      800     1000      1200          0       200      400     600      800      1000     1200
                                             range bin                                                         range bin

                 Figure 8: Correlation coefficients, range bin 300, pier-          Figure 9: Correlation coefficients, range bin 300, pier-
                 side experiment                                                   side experiment, compensated data

                 tensity variations due to transmission power fluctua,             for any row n. 7 is the mean intensity of the, im-
                 tions can be expected to be correlated. Total'energy              age as a whole. After removing row-wise image inten-
                 in each transmission was not measured during this ex-             sity fluctuations the previous analyses were performed
                 periment, but an estimate based on the total energy               again. Figure 9 shows the effect of this compensa-
                 contained in each row i(n, r) provides- satisfactory re-          tion on C300,n- Compared to the uncorrected case the
                 sults. The total energy of each row is calculated as              degree of correlation between column 300 and other
                                           3066                              7     columns is significantly reduced, indicating that trans-
                                                0(n, r)                   (4)      mission fluctuations are a probable cause of the weak
                                     E,, =  E                                      correlation of pixel intensity fluctuations for a given
                                           n=1                                     transmission or side scan sonar image line. This lack
                 The statistics'for this energy distribution are shown in          of correlation leads.to the conclusion that the inten-
                 Table 2. The ratio of standard deviation to'mean is               sity fluctuations observed at various ranges in a side
                                                                                   scan sonar image are essentially independent, in the
                                                                                   absence of change in the imaged topography.
                                      mean:                3,74"                      'Range bin mean, standard deviation, and coefficient
                              standard deviation:           127                    of variation analyses were repeated on the row equal-
                           standard deviation/mean         0.0'140                 i:zed matrix , however the results of these analyses
                                                                                   showed that the equalization process did not change
                 Table 2: Row energy statistics, pierside experiment               these parameters to the same degree that        it changed
                                                                                   C.In2. This lack of perceptible change indicates that
                 larger than the 0.0201 measured in the test tank ex-              the temporal fluctuations in pixel intensity for a side
                 periment. The increased fluctuation is not unexpected             scan sonar image are largely independent of transmis-
                 considering the round-trip pathlength to the region of            sion energy fluctuations and cannot be attributed to
                 maximum intensity in this experiment was as much as               them.
                 200 M as compared to 5 meters in the test tank ex-                   One final analysis of the pierside data was the com-
                 periment. The additional interaction of the acoustic              putation of the power spectral density (PSD) of the
                 transmission with the medium is the probable cause.               fluctuations of the column intensity sequences i(x, n).
                   Information about the transmission fluctuations can             The power spectral density of fluctuations in range bin
                 now be applied to the data set in order to equalike it            400 are shown in Figure 10. Outside of a narrow spike
                 and remove the effects of these fluctuations. The data            centered around DC which was caused by an overall
                 matrix is scaled on a row by row basis, creating a new            increasing trend in intensity with time, the spectrum
                 matrix with elements P(x, r) such that                            is fairly flat. This implies that the intensity fluctua-
                                      1024                                         tions are uncorrelated temporally.
                                      1: V(n, r)
                                      r=1

                                                                              842

                    12
                                                                                               REFERENCES
                    10-

                     8
                                                                                [1] J. S. Bendat and A. G. Piersol. Random Data:
                                                                                    Analysis and Measurement Procedures. Wiley-
                                                                                    Interscience, New York, 1971.

                                                                                [2] C. S. Clay and H. Medwin. Acoustical Oceanogra-
                     2-                                                             phy. John Wiley and Sons, New York, 1977.
                     0.                                                         [3] P. Desantis et al. The use of subharmonics. J.
                     -2.5 -2 -1.5 -1 -0.5 0         0.5  1    1.5   2    2.5        Acoust. Soc. Am., (46):514, 1967.
                                           frequency (Hz)
                                                                                [4] B. W. Flemming. Causes and effects of sonograph
                 Figure 10: Power spectral density, range bin 400                   distortion and some graphical methods for their
                                                                                    manual correction. In W.G.A. Russell-Cargill,
                                                                                    editor, Recent Developments in Side Scan Sonar
                                                                                    Techniques, Central Acoustics Laboratory, Univer-
                          4     CONCLUSIONS                                         sity of Cape Town, Cape Town, South.Africa, 1982.

                                                                                [5] 0. H. McDaniel. Harmonic distortion of spheri-
               This research indicates that there is a          significant         cal sound waves in water. J. Acoust. Soc. Am.,
               amount of fluctuation in side scan sonar acoustics and               (38):644, 1965.
               therefore in the images obtained. The lack of tem-
               poral or spatial correlation of the observed fluctua-            [6] Peter R. Paluzzi et al. Computer rectification
               tions shows that the fluctuations are not due primar-                and mosaicking of side-looking sonar images. In
               ily to transmit power fluctuations. In the absence of                Eleventh Annual Offshore Technology Conference
               other influences such as towfish instability or changes              Proceedings, Houston, Texas, May 1979.
               in imaging geometry, fluctuations of up to 14% were              (7] A. Papoulis. Probability, Random Variablesi and
               observed for images of identical bottom features. The                Stochastic Processes. McGraw-Hill, New York,
               fluctuations are approximately Gaussian distributed.                 1984.
               The fluctuations are nearly a constant percentage of
               mean intensity and indicating that this is a multiplica-         [8] R. J. Urick. Sound Propagation in the Sea. Penin-
               tive rather than additive effect. This implies that if               sula, Los Altos, California, 1982.
               intensities in a side scan image are compensated to
               produce the same mean intensity throughout a nearly
               constant amount of fluctuation is observed throughout
               the image.

                    ACKNOWLEDGEMENTS

               We would like to acknowledge those who provided
               fu'nding, equipment, and facilities for this research; in-
               cluding Marine Imaging Systems, The Massachusetts
               Commonwealth Centers for Excellence, The National
               Science Foundation, Martin Klein, and The United
               States Geologic Survey Division of Marine Geology.

                                                                          343

                                      A PRACTICAL HIGH TECH ADVANCE IN SIDE SCAN SONAR
                                                TARGET POSITIONING AND ANALYSIS

                                                        William R. Abrams

                                                       Seaquest Associates
                                           .Division of Structured Technology Corp.
                                              Box 312, Mystic, Connecticut 06355

                                   ABSTRACT                          InTAC Description
                it    is  the   intent of     this paper     to      Acoustic digitizer technology, forms        the
                present     and discuss a revolutionary              basis   for this patented method of target
                system for analyzing Side Scan Sonar                 positioning     and analysis.       Two high
                records. This system is called InTAC                 resolution transducers mounted on the
                (Instant      Target    Analysis Computer).          side scan sonar recorder,        an acoustic
                InTAC enhances target analysis in two                pen source and a microprocessor are the
                ways. The first speeds up the analysis               system elements.
                procedure by avoiding         tedious manual
                measurements of a sonar contact.            The      The InTAC system is compatible with any
                second enhancement is the ability of                 commercially available side scan sonar.
                InTAC to       determine the position in             With several     "clicks" of its pointing
                latitude and longitude          of     a sonar       devic.e  (the acoustic pen)     one may de-
                target.    This position can then be used            termine a target's position only or its
                to guide submersibles or divers to the               position and size.
                exact      location     of the. target for
                investigation     or recovery       purposes.        The    InTAC transducers         (microphones)
                This    instant  target analysis       is per-       mounting bracket       is installed on      the
                formed realtime,      thus avoiding costly           side scan. sonar recorder and does not
                project delays.                                      interfere   in any way with normal opera-
                                                                     tion of the side scan sonar. Installa-
                                                                     tion averages less than an hour for most
                           OLD ANALYSIS TECHNIQUE                    systems.
                                                                     The software for each InTAC is designed
                Historically      Side    Scan Sonar      (SSS)      for a specific model and make of side
                target position and analysis could only              scan on which it will operate.        Specific
                be done during a post-processing opera-              model characteristics       are taken into
                tion   after     the  SSS  record had      been      consideration such as       size of paper,
                removed from the recorder.        Each target        altitude correction,      speed correction,
                of   interest required mechanical scale              and number of channels.
                measurements of the anomaly, as well as
                SSS fish position and heading at       time of       When the InTAC is used in the "on-line"
                contact for resolving position         or posi-      mode,   a navigation computer input is
                tion and size.       Analysis of       multiple      required.         The navigation computer
                contacts was a time consuming          task and      supplies realtime side scan position,
                subject to error.                                    heading and altitude      at specific inter-
                                                                     vals to the InTAC via a serial inter-
                           NEW ANALYSIS TECHNIQUE                    face.   This data is stored by InTAC for
                Background                                           use when a target is marked.
                                                                     Marking of a target is accomplished by
                Just      prior   to the space         shuttle       touching the acoustic pen to a selected
                Challenger explosion, Seaquest engineers             target on the sonar record.           Touching
                (now a division of Structured Technology             the acoustic pen to the target generates
                Corp.)   developed a SSS target analysis             an acoustic burst and at the same time
                system which may be used on-line or                  starts a clock in the microprocessor.
                during post-processing.       The new devel-         The    microphones detect        the      short
                opment,    named InTAC, was first used               acoustic    burst    ("click")   and measure
                during the search for Challenger debris
                at Cape Canaveral, Florida.

                                                 CH2585-8/88/0000- 344 $1 @1988 IEEE

             the range to the pen.      The pen's x,y
             position on the sonar trace is then
             calculated by the microprocessor using
             triangulation with a temperature com-
             pensated resolution of 0.01 cm.        The
             microprocessor then using a "history" of
             the position data previously sent by the
             navigation computer calculates the exact
             real world position of the marked tar-
             get.    This InTAC calculated position
             takes into consideration the time lag
             between the time the target was detected
             by the sonar and the later time it was
             marked by the operator.   It also takes
             into    consideration the altitude and
             heading of the sonar at the time of
             detection by the sonar.       The target
             height, width and length may also be
             calculated with a few more pen "clicks".

             The InTAC provides the option of saving
             marked target data to the floppy disk
             and/or outputting it to a printer.      In
             addition to this permanent storage, when
             a target is marked, InTAC will transmit
             the target data back to the navigation
             computer via the RS-232 interface. This
             allows a marked. target to be instanta-
             neously stored by the navigation com-
             puter and plotted on a tactical display.

             In summation,   InTAC provides a unique
             way to accurately position and analyze
             side scan sonar targets realtime thereby
             making target data immediately available
             in a printed and/or tactical display
             presentation.

                                                        345

                                             CALIBRATION OF ACOUSTIC DOPPLER CURRENT PROFILERS

                                 Gerald F. Appelll, Joel Gast2 . Robert G. Williams1, and Patricia D. Bassl

                                         1. NOAA National Ocean Service      2. RD Instruments
                                            6001 Executive Blvd.                9855 Businesspark Ave.
                                            Rockville, MD 20852                 San Diego, CA 92131

                                      ABSTRACT                           tow tank calibrated EG&G Vector Measuring Current
                                                                         Meters (VMCM). Intercomparison results provided
                Acoustic Doppler current profilers are widely used       unacceptable uncertainties during the Charleston
                within the oceanographic community for scientific        Harbor survey and other methods were sought.
                research, engineering analysis and routine current
                surveys. They have the ability to profile the            The requirement for RADS calibration is not unique
                water column over a relatively large range and           to NOS and was recently reviewed at the World Ocean
                provide high resolution of the current field.            Circulation Experiment (WOCE) workshop in early
                However, an effective and practical calibration          1988. The conclusion drawn at the workshop was
                technique for the determination of current measure-      that a complete calibration and characterization is
                ment accuracy of these instruments is not                an involved process. It requires a combination of
                established. Field intercomparisons are used as          theoretical analysis, laboratory tow tank testing,
                crude methods of achieving confidence in the             and in-water testing in operational environments.
                measurements but yield mixed results depending on        An important part of this overall RADS calibration
                the environmental conditions.                            and characterization is to develop the capability
                                                                         for routine velocity calibration of RADS under
                The National Ocean Service of  NOAA has recently         controlled conditions. This paper discusses
                conducted tests and established a laboratory             preliminary results of our efforts to evaluate the
                calibration technique for Doppler current pro-           feasibility of accomplishing in water DCP cali-
                filers. A cooperative effort established with    the     bration to a precision consistent with the DCP long
                manufacturer, RD Instruments, assessed the tech-         term accuracy specification of 0.2 percent +/-0.5
                nique and the instruments' performance. Several          cm/s. Our approach.was:
                systems ranging in operating frequencies from 300
                to 1200 kHz were tested and calibrated at the David        Perform calibration tests on several RADS systems
                Taylor Research Center (DTRC) tow carriage faci-           in the DTRC tow tank. Assess the degree to which
                lity. A 1200 kHz system was characterized by the           accuracy can be determined and use the results
                manufacturer through a series of laboratory tests          as a baseline for evaluating a lake calibration
                and navigation runs on a calibrated lake course.           facility.
                This unit was then tested at DTRC for comparison
                purposes. Calibrations of both bottom track and            Develop and evaluate a lake calibration facility
                water track velocity were performed at speeds from         to assess the accuracy to which RADS can be
                0 to 300 cm/s. Sources of error were investigated          calibrated,using a moving barge navigation tech-
                by NOAA and the manufacturer. Test results, cali-          nique.
                bration data, methods and procedures are discussed.
                                                                           Develop and evaluate techniques of measuring
                                                                           critical DCP parameters that affect accuracy in a
                                                                           laboratory environment - specifically, transducer
                                   1. INTRODUCTION                         beam parameters such as angle and geometry.

                The use of Remote Acoustic Doppler Sensing (RADS)          Compare the test results of these three tech-
                systems by the National Ocean Service for current          niques.
                surveys of harbors and estuaries required the
                development of calibration methods. The RADS             The main results to date are of the initial DTRC
                consists of a Doppler current profiler (DCP) and         calibration tests, therefore, this paper will focus
                all of the associated signal processing, data            on presenting the results and conclusions from
                transmission and recording systems. It had been          these tests. Also, it is not within the scope of
                generally believed that DCP's could not be cali-         this paper to discuss RADS system operating
                brated in tow tank facilities because of acoustic        characteristics and terminology. The reference
                reflections from the walls and bottom of the basin.      section cites background literature for further
                The initial attempt to satisfy NOS's calibration         reading.
                requirements was by in-situ intercomparisons with

                                                                    346 United States Government work not protected by copyright

              2. DTRC CALIBRATION TESTS                                  transferred to a second Compaq 286 for analysis and
                                                                         production of graphical displays. Adjustments were
              A test of an RD Instruments 1200 kHz DCP was               made to the test plan based on the interpretation
              conducted in the Circulating Water Channel at DTRC         of the results.
              in mid 1987. The system was bottom mounted at 3-
              meter depth in an upward looking mode. Although a          These tests were successful in establishing the
              rigorous test was not performed, the system                feasibility of the tow basin calibration concept.
              provided a good indication of velocity in two              A formal program was established to calibrate all
              1-meter depth bins. The results suggested that             DCP's used by NOS for surveys. A total of nine
              laboratory calibrations may be possible in a large         systems all manufactured by RD Instruments were
              facility. Thus, a test plan was prepared to                involved: six 1200 kHz units, two 600 kHz units and
              conduct experimental tests in the towing basin at          one 300 kHz unit.
              DTRC. This is a much larger facility and offered
              an accurate speed measurement and control system.          Initial DCP parameter settings were explored to
                                                                         optimize the system performance and obtain high
              The first DTRC tow basin tests were conducted on    a      quality data. The DCP was initially set up to
              RD Instruments 1200 kHz DCP, serial number 0217,    at     record single ping ensembles for the determination
              DTRC during the week of November 10-13, 1987. The          of standard deviation (standard deviation is not
              system was attached to the vertical rails of the           computed in the DCP). The bin width was 1 meter,
              carriage and the transducers were submerged to a           the blanking distance (The programmable distance
              depth of about 30 cm (Figure 1). The DCP is                between the transducer and the first bin) was set
              typically configured with 4 beams oriented 30              to 0.5 meter and the number of bins of data
              degrees off vertical in 90-degree azimuth incre-           recorded was 14. The time between ensembles was 1
              ments. In the azimuth plane, beams 1, 2, 3, and     4      second and a minimum of 100 ensembles was recorded
              are positioned at 0, 180, go, and 270 degrees,             per test speed. Radial beam coordinates were
              respectively. Mechanical alignment of the trans-           recorded plus header data, echo amplitude and
              ducers was performed to assure that tilt errors            spectral width. Tilt attitude was adjusted and
              were less than 1 degree. The characteristics of            mechanically measured to within +/-1 degree.
              the towing basin are:                                      Single ping ensembles require that data be trans-
                                                                         ferred after each-ping. This limits the ping rate
                  basin length 275 meters                                that can,be achieved. The low ping rate resulted
                  basin width 15 meters                                  in a slow response of the DCP to tow carriage
                  basin depth 6 meters                                   velocity changes.
                  fresh water environment at ambient temperature
                  carriage speed range 2.5 to 750 cm/s                   The second series of tests was conducted with the
                  estimated speed measurement uncertainty +/-0.1         DCP set up to record 20 ping ensembles at a ping
                  cm/3                                                   rate of 5 per second. The other parameters
                             RADS CALIBRATION                            remained the same. This set up improved the
                                                                         response of the DCP to carriage velocity changes.
                                                                         A minimum of 12 ensembles were collected per test
                                                                         run, depending on tow speed.

                                                                         Tests were performed with the beam 3 and beam 4
                                                                         pair aligned into the tow direction. Data were
                                                                         first acquired under no-tow conditions in still
                                                                         water. The tow carriage was then accelerated to
                                                        RADS             the desired speed and then DCP sampling was
                                                                         started. After 12 ensembles we stopped sampling
                 ARRIAGE                                                 and changed the carriage speed for the next test
                                                                         run. We then repeated the procedure. Tests were
                                                                         conducted in both east and west tow directions at
                                                                         tow speeds up to 200 cm/s. We also conducted low
                                                                         speed threshold tests at 2.5 cm/s. Repeatability
                                                                         runs were made in each tow direc tion. Tests were
                                        WATER
                                       CHANNEL                           repeated with the beam 1&2 pair aligned into the
                                                                         tow and at a 45-degree angle to the tow.
              Figure i. Sketch of DTRC Tow carriage facility. snowing two
              beams from a PADS unit.                                    RD Instruments personnel participated in a second
                                                                         series of tests conducted in February of 1988.
              A Compaq 286 personnel computer recorded data    and       Another 1200 kHz unit, serial number 229, was used
              controlled the DCP. Software was developed to              for these tests. The test procedures were further
              communicate with the DCP to set operating para-            optimized to get bottom track data and include
              meters and control sampling. DCP data and tow              percent good and status in the data stream. We
              carriage speed were recorded on the 20 Mbyte hard          changed the ensemble size to 100 pings and the time
              disk in ASCII format. Software then unpacked the           between pings to 0.11 seconds, or 9 pings per
              data, applied algorithms to transform data into            second. Four profile pings were obtained for every
              engineering units, and set up specified files for          bottom track ping.
              analysis. After each test run, data files were

                                                                    347

                 The next series of tests were conducted in April of
                 1988. We used a tow basin at DTRC that provides an
                 additional 183 meters of towing length.      Once
                 again, RD Instruments personnel participated.
                 Seven instruments were calibrated during a five day
                 period. We fixed the transducers at a 45-degree
                 tow angle for all the tests. This procedure saved
                 time and allowed calibration of both beam pairs.

                          3. LAKE AND TANK CALIBRATION TESTS

                 Laboratory tests were performed on a 1200 kHz DCP,
                 serial number 0181, at the tank facilities of RD
                 Instruments in March of 1988. The tests were                                   ........
                 designed to measure the effective beam angles    of
                 the system.   Beam misalignment will result in
                 velocity scale factor errors. The angle of peak
                 power of each beam was measured as well as an
                 integration of each beam through angles of 5
                 degrees (in 0.2 degree increments) on either    side                                *A
                 of the peak power point. Finally, the included
                 angles between beams, 1&2 and 3&4 were measured.
                 This facility is a tank of fresh water that has a
                 transducer positioning (azimuth and elevation)
                 system at one end and a calibrated receiving/trans-
                 mitting transducer at the other. The transmit path
                 is 2.4 meters long. The measurement accuracy of                                             f
                 this facility was determined to be +/-0.15 degrees
                 in measuring the absolute pointing angle of an                     RD Instruments pontoon boat for lake
                 individual beam. Measurement accuracy of included                    calibration with a DCP protruding
                 angles was determined to be +/-0.10 degrees.                              through the test well.

                 A navigation course on a San Diego lake was                  Calibration of a DCP at one velocity consists of
                 surveyed by RD Instruments in March of 1988. The             two traverses of the course at a constant velocity
                 purpose of this course was to determine whether a            on reciprocal headings. Water velocity in the lake
                 DCP could be calibrated using a moving barge                 varies from near zero to 2 cm/s, depending on depth
                 navigation technique. The lake is a fresh water              and time of day. The reciprocal runs average out
                 reservoir that is about 1500 meters long by 500              this water movement. Serial number 0181, a 1200
                 meters at its widest point. Its depth varies to       a      kHz unit, was used to establish procedures and
                 maximum of 30 meters. Two courses were surveyed,             determine the best operating parameters for the
                 one 600 meters long and the other 1025 meters long.          lake. Initially there were differences in distance
                 Conventional surveying methods were used in laying           traveled between bottom track and water track of up
                 out the course and existing landmarks (trees,                to 0.5 percent. This was traced to a signal "skew"
                 telephone poles, etc.) were used to provide                  error in the system that affected only the water
                 starting and ending markers. Flags were installed            track performance. The system's processing filter
                 at either end of the course as bearing aids. The             was altering the center of power of the returned
                 length of each course was checked with theodolite/           Doppler backscattered signal. Signal processing
                 infrared distance measurement equipment (DME). The           algorithms were modified and the result was an
                 theodolite was fixed on land and a cluster of                agreement between bottom track and water track of
                 corner reflectors mounted on the barge. The                  within 0.15 percent. The modification is described
                 distance to each marker was determined by posi-              in a pending paper authored by Terry Chereskin of
                 tioning the barge at the markers. Repeated                   Scripps Institute of Oceanography, Eric Firing of
                 measurements confirmed the length of each course to          the University of Hawaii, and Joel Gast of RD
                 be within 1 meter of the surveyed values.                    Instruments.

                 RD Instruments bought a pontoon boat (the     barge)                        4. CALIBRATION RESULTS
                 and rigged it with the necessary power, computers,
                 and fixtures to accommodate a DCP (see photograph).          The initial DTRC tests conducted in November of
                 Specialized software was written to integrate DCP            1987 focused on the performance of the system in
                 velocity, resolve it into earth coordinates and              the test facility. The decay in signal echo
                 compute the distance between the starting and end            amplitude was investigated through 128 bins to be
                 points. This distance is computed for each bin of            sure that succeeding pings were not being con-
                 the water profile as well as for bottom track.               taminated by reverberation echoes from the previous
                                                                              ping. Figure 2 shows a profile of the first 14
                                                                              bins as the signal bounces within the facility
                                                                              basin. The first 4 bins yield clean data and the
                                                                              fifth apparently is contaminated from side lobes.
                                                                              The sixth bin shows a large increase in echo
                                                                              amplitude caused by reflection of the beams

                                                                        348

                     directly from the concrete bottom. The remaining                               kHz DCP's in November, 1987, and again in February,
                     bins of data are reflected from the bottom bounce                              1988, showed first bin echo amplitude levels of
                     of the signal. Measured velocities in the first                                from 35 dB to 40 dB. These measurements are
                     four bins were relatively similar. Bin 5, however,                             referenced to the receiver noise level in the DCP
                     showed significantly lower velocities due to side                              processing bandwidth. The normal levels measured
                     lobe contamination. It was determined that we                                  in field operations are in the range of 60 dB to 90
                     could ping at a rate of 9 times per second and                                 dB. The DCP has a receiver that includes an AGC
                     receive  clean profile data in the first 4 bins.                               function to keep the signal at a constant level.
                          0                                                                         The AGC is preset, at the beginning of a ping, to
                                                                                                    an echo amplitude of 90 dB to initialize the
                          I                                                                         receiver gain for a nominal echo amplitude level.
                          2                                                                         The AGC then adjusts throughout the ping as the
                                                                  Side lobe                         signal falls off with increasing range (depth).
                          3                                       from bottc,                       The rate of change of AGC reflects the rate of
                     -j;  4                                                                         change of the echo. This is normally proportional
                     L                                                                              to range squared in the first few bins. The AGC
                     R    5-                                                                        rate was observed to be higher than expected in the
                          6   __99iiqti                                                             basin.     This indicates that it was "recovering"
                                                                                                    from the difference between the preset value and
                          7                                                                         the actual echo amplitude.
                     c
                          a                                                                         We decided to increase the scattering level of the
                                  Reflected                       Side lobe                         basin to closely approximate ocean scattering
                     Z    9       Signal                          f am wall                         conditions.       This was accomplished by dispersing
                        io                                                                          pulverized limestone in the water. The idea was
                        il                                                                          that the limestone would disperse slowly over the
                                SURFACE                                                             basin but eventually would dissolve and not con-
                        12          - ---- -------------------------       ------------             taminate the facility.            Fifty pounds of pulverized
                                                                                                    limestone was scattered over 270 meters of basin
                        13                                                                          length during the initial tests. The echo ampli-
                        14   -                                                                      tude, as measured by serial number 0181, increased
                             0            20            40             66             80            to nearly 60 dB.         The velocity calibration results
                                                                                                    with this unit improved dramatically. A comparison
                                             Mean Backscatter (dB)                                  of this data to that taken by RD Instruments is
                                                                                                    covered in a later section.
                     Figure 2. DTRC DCP Tests - Nov.12-13, 1987.       Backscatter
                     profile of 22 test runs.                                                       Additional units were tested using the limestone to
                                                                                                    increase echo amplitudes. Serial number 0262, a
                     Performance anomalies were noticed in the initial                              600 kHz system, improved also, but still had speed
                     November tests. In still water conditions without                              errors approaching 6 percent. This was an improve-
                     tow carriage movement the DCP indicated a velocity                             ment from the previous 60 percent error. The echo
                     of 4 to 5 cm/s. Movement of the tow carriage to a                              amplitude for this system was lower than that for
                     threshold velocity of 2.5 cm/s resulted in a                                   the 1200 kHz systems (48 dB vs. 60 dB). The
                     reduction of indicated velocity tonear the actual                              limestone scatterers are apparently better seen at
                     velocity. Continued increase in speed resulted in                              higher frequencies. We do not know if the 600 kHz
                     the DCP speeds being lower than the actual tow                                 system would improve at higher echo amplitudes.
                     carriage speed.                                                                The 300 kHz system did not respond to the limestone
                                                                                                    and backscatter amplitudes remained low.
                     Tests conducted     in February of 1988 confirmed                the
                     results of the November tests. It also showed that                             ERROR VELOCITY
                     different 1200 kHz systems exhibited similar
                     performance characteristics.                                                   Beam differences and error velocity was explored as
                                                                                                    an indicator of system performance. Beam dif-
                     In April of 1988 seven systems were tested in the                              ferences are computed by the addition of opposing
                     DTRC facility. Speed calibration data on the 12DO                              beam velocities. Ideally, for horizontal motion
                     kHz DCP's was worse than the previous 2 systems.                               and no DCP tilt, opposing beams see the same
                     Serial number 0181, the unit calibrated by RD                                  velocity, opposite in sign. Therefore, in the tow
                     Instruments, performed in a similar manner in that                             basin beam differences should be near zero.
                     the measured speed was significantly lower than the                            Although the DCP was mechanically adjusted to
                     actual tow carriage speed. Attempts at calibrating                             within 1 degree of tilt and there was no vertical
                     the 600 kHz and 300 kHz units resulted in poor                                 velocity, beam differences were significant. On
                     velocity performance in all bins.                                              serial number 0181, average opposing beam dif-
                                                                                                    ferences were from 4 to 6 cm/s. Expected beam
                     ECHO AMPLITUDE                                                                 differences for a 1 degree tilt and 30 degree beam
                                                                                                    angles are approximately 6 percent of the hori-
                     We speculated that the poor velocity performance                               zontal velocity component along the beam pair
                     might be due to abnormally low echo amplitude                                  direction. Thus, because of the sensitivity to
                     levels. The basin water is very clear with few                                 tilt, beam differences are not good indicators of
                     acoustic scatterers. Tests conducted on the 1200                               system performance.

                                                                                            349

                   Error velocity, which is computed by subtracting                                                  TABLE 2
                   the opposing beam differences of the orthogonal
                   beam pairs, should be a much better velocity                                                  Barge Velocity
                   quality indicator. For symmetrical beams, error                                      Bin      80 cm/s       120 cm/s     200 cm/s
                   velocity should always be zero, independent of
                   tilt, as long as the water flow across the four                                                 Average Error in cm/s
                   beams is horizontally homogeneous. Observed error
                   velocities when forward velocity errors were small                                   1        -0.5          -0.1
                   ranged from -2.5 cm/s to +2.5 cm/s, and were not                                     2          0.0         -0.2         -o.6
                   correlated with speed. When forward velocity                                         3        -0.2          0.0          -0.4
                   errors were larger than 5 cm/s, error velocity was                                   4        -0.1          0.1          -0.5
                   generally larger, Thus, error velocity showed                                        5        -0.4          -0.1         -0.4
                   promise as an indicator of the errors. However,                                      6        -0.2          -0.2         -0.2
                   more analysis is required to understand and                                          7        -0.2          -0.1         -0.4
                   calibrate "error velocity" as an indicator of the                                    8          0.0         0.0          -0.4
                   actual velocity error.                                                               9        -0.1          0.1          -0.1
                                                                                                        10       -0.1          0.0            0.0
                   PERCENT GOOD                                                              Bottom track        -0.2          -0.2         -0.3

                   The percent good criteria was not always a good                               Errors indicated      are     in cm/s for  serial
                   indicator of the quality of the data. It would                                number 0181, 1200 kHz unit, on calibrated
                   generally flag problems in bin 1 but would not                                lake course. Each data point consists of
                   indicate bad data in bins 3 or 4 despite low signal                           averaged reciprocal runs on the course to
                   and large speed errors.                                                       average out water movement.

                   SPEED                                                                    These data are plotted along with the DTRC data in
                                                                                            Figure 4. Figure 5 shows serial number 0181
                   Calibrations of both bottom track and water track                        results with and without limestone.
                   in 3 bins were performed on all systems. Figure 3
                   is a plot of the residual errors in the measurement
                   of speed from serial number 0181 and 0268, 1200 kHz
                   systems in bins 2, 3, 4 and bottom track. Table 1                                                 0
                   summarizes the error statistics from the plot data.
                   This data is for the condition where echo amplitude                           4      ---% -------- ----------------- -----------------
                   had been increased with limestone.                                                   0        8             0                    0
                                              TABLE 1                                       Z                    +

                        ERROR          WATER TRACK           BOTTOM TRACK                   L               +
                        STATISTIC        BINS 2,3,4                                         OL          +        +
                                                                                            L
                                             cm/s                 cm/s                      W           F   +
                        AVERAGE             -1.1                  -0.2
                                                                                                                                                    +
                        STD. DEV.            1.0                   0.6                      CL                   +   +
                        MAXIMUM              0.5                   0.5                           -2-
                                                                                                                     +                +
                        MINIMUM             -3.8                  -1.7                      L)
                                                                                                                                      +

                   For comparison purposes        an EG&G VMCM was       calibrated                                                             +
                   at the DTRC facility acquiring data simultaneously
                   with a DCP. The results of calibrations on all 4                              -3-
                   rotors at speeds of from 20 to 200 cm/s revealed an                                                                              +
                   average error of -3.3 cm/s and a standard deviation                                  DCP minus CARRIAGE SPEED DATAI
                   of 2.2 cm/s.

                   Serial number 0181 was tested by RD Instruments and                           -4-
                   by NOAA to determine the feasibility of calibrating                                  0   50      100     150     200       250     300
                   an instrument in a lake environment. The instru-
                   ment was set up the same in both the lake tests and                                           Tow Carriage Speed (cm/s)
                   the DTRC tests of April. The orientation of the
                   beams was, however, different. For the lake tests,                                              +     BINS 2-4
                   beam 3 was oriented forward while the beams were                                                0     Bottom Track
                   oriented at 45 degrees to the direction of motion                                             ---------- Zero Error
                   for the DTRC tests. The lake results on this unit
                   are summarized in Table 2.          This data was taken                   Figure 3. DTRC 1200 KHz calibration errors. Data is from
                   with beam 3 forward.                                                      two systems were limestone was used to keep the echo amp-
                                                                                             litude above 40 dB. Zero tow speed data is not displayed.
                                                                                             Data points represent and average approximately 10 ensembles.

                                                                                     350

                          0.2-                                                                    Several bottom track runs indicated a scale factor
                                                                                                  error of approximately -0.16 percent. The DTRC
                                                                                                  data indicated a bottom track scale factor error
                          0.0  ------------  -----------------------------------------            of approximately -0.21 percent. We expected a
                                                                                                  larger scale factor at DTRC because of the dif-
                                                            +                                     ferent beam orientation (see Velocity Scale Factor
                                                                                                  below). The average of the water track errors in
                         -0.2-                    a         0                                     Table 2 is -0.18 cm/s. The average of the water
                                                                                                  track errors measured at DTRC was -0.66 cm/s for
                                                                                                  five tests ranging in velocity from 1.5 cm/s to 102
                     r
                         -0.4-                                                                    cm/s.
                     cc
                     0
                     a:                                                                           The two 600 kHz systems exhibited larger errors
                         -0.6-                                                                    with a -4.9 emls worst case bottom track error and
                                                                                                  -10.7 cm/s worst case water track error. The echo
                                                                                                  amplitude for these systems with limestone was less
                                                                                                  than 50 dB. It is not known whether the accuracy
                         -0. a- K-                                                                would improve if the echo amplitude were increased.
                                                                                                  No attempt was made to calibrate a 600 kHz unit on
                                                                                                  the lake. The significant result is that all
                         -1.0                                                                     systems display a negative error at all flow speeds
                               6    36     e6     96      120   150   180    210    240           and a positive zero offset.

                                                  SPEED (cm/s)                                    VELOCITY SCALE FACTOR

                                          +       Lake Water Track                                The DCP error consists of two components:                      scale
                                          0       Lake Bottom Track                               factor and bias.          The scale factor is the slope of
                                                  OTRC Water Track                                the least-squares curve fit to the data.                    Bias is
                                          A       OTRC Bottom Track                               the intercept of the best straight line to the
                                       ---------- Zero Error                                      Y-axis.      The primary cause of velocity scale factor
                                                                                                  errors is believed to be due to the effective beam
                                                                                                  pointing angles. The beam pointing angles of
                     Figure 4. Comparison of      lake and DTRC test results on                   serial number 0181 were measured by integrating
                     serial number 0181. 1200     KHz system. Lake data is the                    each beam through +/-5 degrees on either side of
                     average of 10 bins; OTRC     is the average of 3 bins.                       the beam peak.         The beam width is about 2 degrees.
                                                                                                  The results of this test show an effective beam
                          4                                                                       pointing angle that was inward (toward the group
                                                                                                  center) of the peak by an average of 0.02 degrees
                          3-                                                                      for the four beams. This is small compared to the
                                                                                                  angle measurement capability of the facility
                          2-                                                                      (+/-0.15 degrees), but it does indicate that errors
                                                                                                  due to non-symmetrical beams is probably small
                                                                                                  (<O.l percent).

                     C_                                                                           The included angles, beams 1 to 2 and beams 3 to 4
                     0    0- ----- ----------                 -----------   ----------
                     C_                                                                           were measured. The difference between these
                     C_
                     LU                                                                           angles was measured to be 0.31 degrees with the
                     CL  -I-
                     U                                                                            beam 1-2 pair having the larger angle. Although
                     M                                                                            the absolute measurement accuracy is believed to be
                         -2-                                                                      +/-0.10 degrees, the difference measurement is
                                                            0                                     expected to be more accurate. As a result, we
                         -3                                                                       would expect to see a scale factor change of 0.47
                                                                         0                        percent between beam pair 1-2 in the direction of
                                                                                                  motion and pair 3-4 in the direction of motion.
                                0                           50                      160           This was tested by taking the unit to the lake
                                                                                                  course and performing two calibrations, rotating
                                        Tow Carriage Speed      (cm/s)                            the transducer 90 degrees between the two.                      The
                                                                                                  difference in calibrations was measured to be 0.56
                               *    BIN 2                   +   Limestone added'                  percent using bottom track.              As expected, the beam
                               *    BIN 3                   X   Limestone added                   1-2 pair had the higher scale factor.
                               11   BIN 4                       Limestone added
                               0    Bottom Track            0   Limestone added                   In the tests conducted at DTRC, the beams were
                         ---------- ZERO ERROR                                                    oriented 45 degrees to the direction of motion.
                                                                                                  The larger included angle between beams 1 and 2
                                                                                                  should result in a larger scale factor of
                     Figure 5.   OTRC calibration of RD S/N Oi9l: with and with-                  approximately 0.28 percent when compared to the
                     out limestone. Errors shown are the ensemble averages for                    lake navigation data that was run with beams 1 and
                     each speed minus the tow carriage speed.                                     2 at 90 degrees to the direction of motion.

                                                                                           351

                 UNRESOLVED DCP PROBLEMS                                    overall calibration. Accuracy of facilities must
                                                                            be improved. Work on DCP's with frequencies other
                 There are several problems that remain unresolved.         than 1200 kHz must be done. Finally, when scale
                 First, each DCP tested exhibited positive biases at        factors are calibrated in controlled circumstances,
                 zero velocity. This bias disappeared with the              the effects of different ocean environments must be
                 slightest velocity (2.5 cm/s). Laboratory and lake         determined through analysis, simulation, and
                 testing by the manufacturer didn't duplicate this          in-water testing.
                 problem. It may be related to the low echo
                 amplitude and that is being investigated at the
                 present time.                                                                 6. REFERENCES

                 Second, the errors experienced when the echo               1.   Mero, T. N., G. F. Appell, and D. L. Porter,
                 amplitude was low is not well understood. It is                 "Sea-Truth Experiments on Acoustic Doppler
                 reasonable to expect that the low levels we                     Current Profiling Systems," Proceedings of
                 experienced (30 dB below normal) might cause the                Oceans 183, Marine Technology Society, San
                 DCP some difficulty. However, we expected the                   Francisco, California, August 1983.
                 percent good output to eliminate the data that was
                 in significant error. We found this to be the    case      2.   Appell, G. F., "A Real-Time Current Measure-
                 for Bin 1 where the data good output flagged                    ment System," Sea Technology, February 1984,
                 problems. Bins 2 through 4, however, were not                   Volume 25, Number 2.
                 flagged as bad despite large speed errors.
                                                                            3.   Magnell, B. A., "Fall 1983 Acoustic Doppler
                 CALIBRATION PROBLEMS                                            Profile Measurements and Sea Truth Inter-
                                                                                 comparison Experiment at Ambrose Light, New
                 Scale factor and bias differences between the lake              York," Technical Report to NOAA, EG&G Washing-
                 and DTRC need to be resolved. The different beam                ton Analytical Services Center, Inc., 1984.
                 orientations between the two tests on serial number
                 0181 do not account for all the differences. The           4.   Magnell, B. A., "Delaware Bay Intercomparison
                 accuracies of the calibration methods must be                   Experiment, Fall 1984,"Technical Report to
                 improved in order to allow a calibration to the DCP             NOAA, EG&G Washington Analytical Services
                 specification of 0.2 percent +/-0.5 cm1s. The lake              Center, Inc., 1985.
                 course is believed to be accurate within 1 meter
                 (0.16 percent). There is an additional error of            5.   Appell, G. F., T. N. Mero, J. J. Sprenke, and
                 positioning on the starting and ending marks for                D. R. Schmidt, "An Intercomparison of Two
                 the navigation technique. Repeated runs suggest                 Acoustic Doppler Current Profilers," Pro-
                 that this is also on the order of 1 meter. The                  ceedings of Oceans 185 Marine Technology
                 velocity uncertainty at DTRC is believed to be on               Society, San Diego, California, November 1988.
                 the order of 0.1 cm/s. The DTRC error is a per
                 sample error, the lake error is for the entire             6.   Woodward, W. E. and G. F. Appell, "Current
                 distance travelled. Error velocity data needs to                Velocity Measurements Using Acoustic Doppler
                 be re-examined and correlated with beam angle dif-              Backscatter: A Review", IEEE Journal of
                 ferences. Other frequency DCP's need to be                      Oceanic Engineering, January 1986, Vol.OE-11,
                 compared between the two facilities. Future                     No.1,PP-3-6.
                 testing, both by RD Instruments and by NOAA at DTRC
                 will be geared to resolving these problems.                7.   Woodward, W. E., D. L. Porter, G. F. Appell,
                                                                                 Proceedings of the Acoustic Doppler Current
                                    5. CONCLUSIONS                               Profiling Symposium, U.S. Department of
                                                                                 Commerce, NOAA Report, 1984
                 Significant progress has been made toward per-
                 forming velocity calibration of DCP's to precisions        8.   Appell, G. F., T. N. Mero, R. G. Williams,
                 approaching instrument specifications. Tow tank                 W. E. Woodward, "Remote Acoustic Doppler
                 facilities like DTRC can be used in those cases                 Sensing: Its Application To Environmental
                 where the echo amplitude can simulate the ocean                 Measurements," Proceedings of ASME's Current
                 environment. The tow tank can also be used to                   Practices and New Technology
                 verify other procedures such as calibration on lake             in Ocean Engineering Symposium, New Orleans,
                 facilities. The feasibility of performing calibra-              February 23-28, 1986.
                 tions on a lake having small currents has been
                 established. It has been shown that such a                 9.   Chereskin, T., E. Firing, J. Gast, pending
                 facility has the capability of detecting small                  paper dealing with the identification and
                 changes in transducer beam pointing angles.                     screening of filter skew and noise bias
                 Laboratory measurements on transducer beam para-                errors in acoustic Doppler current profiler
                 meters can provide meaningful calibration data.                 measurements.
                 This data can then be used to provide scale factor
                 corrections to the DCP. Bottom track can be used           10,  Firing, E. (1988) WOCE Tropical Workshop
                 to calibrate velocity scale factors. This has the               Report, in press.
                 practical advantage of not having water current
                 variability. It also has inherently lower
                 variances that result in more accurate measure-
                 ments. There is, however, much to do to achieve

                                                                       352

                                          DEVELOPMENT OF A SHIPBOARD ACOUSTIC
                                                       DOPPLER CURRENT PROFILER

                                                                1           1                  2
                                                Yoshifumi Kuroda, Gentaro Kai and Kiyonori Okuno
                                      1                                                 2
                                       Japan Marine Science and Technology Center       Japan Radio Co., Ltd. Laboratory
                                        2-15,Natsushima,Yokosuka,237,Japan              1-1,Shinorenjaku,5, Mitaka, Tokyo, Japan

                                    1     ABSTRACT                                     transmitter-receiver unit was carried out, then comparison
                                                                                       between the ADCP and RCM was performed. These results
               A shipboard long range acoustic Doppler current profiler                of the open sea tests are discussed in Section 5.
               (ADCP) was developed, which can measure vertical pro-
               files of ocean currents and acoustic backscattering strength                       3 SYSTEMDESCRIPTION
               in 32 layers up to a depth of 400m, and track the sea bot-
               tom up to a depth of 1000m. In  the development of this                 The ADCP's principles is well known [2],[3]. The acoustic
               ADCP, we aimed to develop an acoustic transducer mod-                 pulses are scattered by particles drifting in the water, and
               ule(70kHz, phased array type) for the measurement of the             the Doppler shift frequency which is proportional to the
               open ocean currents, and introduce all advanced signal pro-             relative velocity between the ship and the water occurs in
               cessing method based on the auto-correlation function to               a received signal. Conversely speaking, the Doppler shift
               derive the mean Doppler shift frequency from the received               frequency call be converted into the relative velocity. The
               acoustic signal. And then, in order to confirm the per-                depth of each measuring layer is determined by the delay
               formance of the ADCP, the transducer and transmitter-                 time between pulse transmission and pulse receiving.
               receiver unit were tested in the open sea. Furthermore,
               the comparison between the ADCP and Aanderaa current                    TABLE 1        Fundamental specifications of the developed
               meters (RCM) was carried out in the Kuroshio current on                 system.
               the east side of the lzu Ridge. These results showed that                  measurable items                  current direction, velocity
               the system has capability of measuring the ocean current                                                     scattering strength
               velocity and the scattering strength up to a depth of 400m.               range of detectable current       400 meters
                                                                                          measurable layers number          32 layers
                                                                                          range of detectable sea floor     1000 meters
                              2 INTRODUCTION                                              velocity resolution               1 cm/sec
                                                                                          acoustic frequency                70 kHz
               Shipboard acoustic Doppler current profilers (ADCP) which                  beam configuration                4 beams (JANUS type)
                                                                                          beam angle to the vertical        � 300
               can  measure remotely vertical current velocity profiles un-              beam width                        50
               der a ship have been developed recently in  several countries.             pulse width                       7.5-30 msec
               In Japan, conventional ADCPs are used as ship navigation                   pulse intermittence               1-5 sec
               and fishing instruments which measure the currents up to                  measuring layer thickness         5-50 meters
               one or two hundred meters in depth at several measuring                   averaging time                    30-600 sec
               layers. And a multi-layer ADCP for the coastal region has
               been developed and used to measure a tidal current around
               a  narrow strait[l]. And as a next step, a development of an           The specifications of the ADCP are shown in TABLE 1, and
               ADCP for the open sea was required to reveal the current                the block diagram of the ADCP system is shown in Fig.l.
               structure of the Kuroshio and other deeper currents.                    The ADCP system consists of six units. The transducer
                                                                                       unit has two modules which transmit 70kHz four acous-
               The development  of a  long range ADCP for the open ocean               tic beams in a JANUS configuration. The ship navigation
               is presented in this paper. The ADCP system is described               unit has LORAN-C and GPS receivers which input the ship
               in Section 3. The developments of the 70kHz transducer                  speed to the earth into the signal processor unit. This ship
               module of phased array type and an advanced signal pro-                 speed enables the ADCP to calculate the current velocity
               cessing method based on the auto-correlation are presented             to the earth when the ADCP fails to track the sea bottom.
               in Section 4. The performance test of the transducer and               The signal processor unit derives the current velocity and

                                                              CH2585-8/88/0000-   353 $1 @1988 IEEE

                   SHIP NAVIGATION UNIT                                      DISPLAY UNIT
                    - - - - - - - - - - - - - - - - -
                      GYRO                         GPS                                             147
                                                                  CRT
                     COMPA S       LORAN-C

                                                                             MOUSE
                  L                                       J

                                                                 MICRO-                                            . . . . . .
                                                               COMPUTER      KEYBOARD
                                    SIGNA PROCE       T

                                                                                      -7
                                                              FEARTRI-67GE
                                           RECEIVER
                                                             _L_M_T __j
                                      ...... [T@RANSMIT
                                               TER
                  TRANSDUCER UNIT L - - - - - - - - -    J  L                         J
                                   TRANSMITTER-RECEIVER UNIT              RECORDING UNIT

                                Fig.1   Block diagram of the ADCP system.

                 the scattering strength profiles from the received acoustic
                 backscattering signals. The display unit consists of a iiii-
                 cro computer, Which is used to input measuring parameters
                 with a, niouge tool and display measured data on a CRT in
                 real time. The recording unit has a cartridge magnetic tape            Fig-2   Transducer unit consisting of two modules.
                 recorder(1/4 inch,38. Mbytes).
                        4 SYSTEM DEVELOPMENT                                      4.2  SIGNAL PROCESSING
                                                                                  Figure 4 shows a, raw Doppler shift signal of the Fore/Aft
                 4.1 TRANSDUCER MODULE                                            beanis in the open sea getting directly from the receiver
                 A transducer module of phased atray type which can trans-        unit of the ADCP. And the auto-correlation function cal-
                                                                                         5
                 init a, pair of acoustic bearns of 70kHz was developed. The
                 ADCP uses two transducer modules to transmit two pairs
                                                                                      El                               A1\q v
                 of beanis of For'e/Aft and Port/ Starboard. The transducer                _\j                       _V
                 'unit Consisting of two modules is shown in Fig.2. The               >
                 square shaped transducer module consists of 800 pieces                                                    U@       G24
                                                                                              104.)           C TIM11,(-)
                 25 x 32 elements) of transducer elementg, whose dimension        (a)                          rmpw j W
                 is 40 x 33 x 14 cin. The beani pattern of a module is shown
                 in Fig.3. The beani axigles are � 301 to the vertical and the
                 beani width is 5o. And the side lobes are depressed under
                 15dB to the two rilain lobes.

                                                                                                          ...02  lool   o-6    ooos    D.,
                                                                                                               TIME LAG

                                                                                             WT

                                                                                          MH                102               iz6
                                                                                                                                      [42.
                                                                                  (b)    (637.)               E Don i

                                                                                                         o.oz   Qoo4   0.o6    okos

                                                                                                           TIME LAG(-)
                                                                                  Fig.4  Doppler shift signal in the open sea, and the auto@
                 Fig.3   Acoustic beam pattern of the phased array type           correlation function. (a) signal from 104-156in depth, (b)
                 transducer module.                                               signal from 637-702m depth.

                                                                             354

                                 QUADRATURE I    A/D                   COMPLEX                            MAIN CALCULATOR
                                  PHASE          CONVERTER            AUTO-CORRELATOR             ,Re(R(AT))
                                 DETECTER
                                                                                                     (R(T))tan-1(:I@-/R],-
                        SIG.              x    LPF     A/D       DELAY                         f       x2                       MEAN
                                                                           CONJUGATE                                            FREQ.
                                                                           MULTIPLIER                        +
                                          x     LPF    A/D                                    j        X2       JR(
                        REF.                                                           INTEGRATOR
                                    900                                                    f                          AT         2
                                                                                                                  IR 0)
                                                                     MULTIPLIER                                                 VARIANCE
                                                                             x2                        JR(O)j

                Fig.5 Flow diagram of the signal processing based oil the          correlation is shown in Fig.5. The resolution of the ad-
                auto-correlation function.                                         valiced signal processing was compared with the zero cross
               culated Loin the signal is shown together, At the measuring         iiiethod. The results are shown in Fig.G. The zero cross
               time the ship was kept straight at a speed of about 6knots.         method is successful in deriving the Doppler mean frequency
               Generally the Doppler shift frequency of 111z corresponds           when the SIN is 6 dB, but it fails ill that when the SIN
               to 2.14ciii/sec. The frequency of the signal ill Fig.4a is          decreased. Oil the other hand, the advanced signal process-
               about 140Hz, therefore, the relative current velocity is esti-      ing is successful up to the value of -6dB, furthermore, the
               inated as about 300ciii/sec. That seems to be a reasonable          variance of the derived values at S/N=GdB is smaller than
               value. In that case, the signal scattered at the shallower          that by the zero cross method. Therefore, it call be said
               ra.lige (104-156111 depth), and the SIN of the signal seems         that the method used in this ADCP shows all filiprovernelit
               to be very large. Therefore, it is easy to decide the Doppler       of SIN by 12dB.
               frequency from the received signal. On the other hand the
               depth becanie deeper, the signal became more complicated                           5 OPEN SEA TEST
               as shown in Fig.4b (637-702m depth). Thus it is difficult
               to estimate the velocity from these low SIN signal.                 5.1 TEST OF TRANSDUCER AND
                                                                                          TRANSMITTER-RECEIVER UNIT
               In order to derive the mean frequency from these signals, all
               advanced processing method based oil the auto-correlation                     139E                          140E
               function [4] was introduced instead of the zero cross method
                                                                                                                      lz@.i Bay
               used ill [1]. The signal processing flow using the auto-
                                                                                                                          Soso Pen.,

                                                                                          35N        Sagami Bay
                        0.75

               (a)

                        0.25
                                                                                                       0,hima Is.

                        0.00.
                          ,a.         I.50        200  'H21   250          Sao
                                              FREDUENCY                                                               Mooring Site

                        2.00.
                                                                                                     A
                                                             zero-CrOss
                        0.75.  auto- correlation

                                                                                                          Miyake I
               (b)

                        0.25                                                               14N                      Traverse section

                                                                                                                    ikura Is.
                        0.001-
                          i0o         16          -00         no           Sao
                                              FMMNC@ (HZI                          Fig.7   Test sea, area.
               Fig.6    Comparison between the resolution by the auto-             The hatched square shows'the     area where the transducer
               correlation method and that by the zero-cross iliethod. The         system tested, the triangle shows the mooring site of the
               model signals consisted of 20OHz Doppler shift frequency            R-CM, and the thick solid line shows traverse section of the
               with white noise, (a) S/N=6dB, (b) S/N=-6dB.                        Kuroshio current.

                                                                              355

                   The transducer unit and trallsinitter-receiver unit were tested           5.2 COMPARISON BETWEEN ADCP
                   ill 1984 ill the Sagami Bay near Tokyo) (Fig.7). The result is                  AND RCM
                   shown ill Fig.8. There was a large value in the receiver out-
                   put near the depth of 1000m, which was thought to show                    The deck units and transducer unit of the ADCP ill the test
                   a, strong sea bottom reflection. It shows that the ADCP                   are shown ill Fig.9,10 and 11. Before the comparison, the
                   has, the ability to track the sea bottom up to 1000in or                  dependence of the standard deviation of the Doppler shift
                   more. Furthermore, the receiver output level of -15dB at                  frequency (i.e. breadth of the spectrum of the received sig-
                   the water depth of 500m was sufficiently large to derive the              lial) on the pulse width and measuring layer thickness was
                   Doppler frequency, because it was much greater than the                   measured using the ADCP ill the open sea, under the vari-
                   background noise level of -25dB. Thus, it was confirmed                   ous values of the two parameters. Figure 12 shows that the
                   that the transducer systern has stifficient capability to de-             ,standard deviation was increased when the pulse width or
                   tect the water backscattering signals.                                    the measuring layer thickness was decreased. Especially,
                                                                                             the standard deviation was rapidly increased where the
                                                                                             ineasuring layer thickness was 51n, and the velocity profiles
                                                                                             (not          became complicated than the other. Conse-
                                                                Pulse 30rnsec
                                                                                             quently, the measuring layer thickness shorter than 10ill is
                     M                                          Freq. 70KHz
                                                                                             not appropriate for this ADCP.

                                                                                             In order to confirm the performance of the ADCP, the corn-
                                                                                             parison between the shipboard ADCP and the moored Aan-
                     -2                                       sea bottom reflect.ion         deraa current ineters (RCXI) was carried out ill 1987 at Izu
                                                                                             Ridge. The mooring site is shown in Fig.7, at which the
                                    -1 5dB                                                   depth was 800111 and the strong current of the Kuroshio
                                                                                             was expected. The mooring consisted of five current me-
                                    -2'5dB
                             backgroun noise level                                           ters at 30, 140, 250, 375 and 500m depth. The experimental
                                                                                             conditions of the four test cases are shown in Table 2. In
                                    R5)  ( 520) (U      ('e5)      (1iZ                      the Case 1,2 and 3, the ship ran by the surface buoy of the
                                            Depth (m) '                                      mooring within a distance of 50-100in at a speed of 5knots
                          Fig.8    Received signal level ill the open sea.

                             17777"M

                                                                                                               Fig. 11   Fish shaped housing containing
                                                                                                               two transducer modules, which was Exed
                                                                                                               oil the port side of a ship at the same
                                      5d @@

                      Fig-9 Ship navigation, signal            Fig.10     Display and receiver unit.           depth as the ship bottom.
                      processing and transmitter-
                      receiver unit.

                                                                                         356

                    and measured the current profiles. In the Case 4 the ship                                           0                    RCM - . ROCP - x              RCM - o ADCP - x
                                                                                                                                             IiiiiiIIIIIIII Jill[          11 11
                    was drifted near the site. In these cases, the reference ship
                                                                                                                                             x C,                                                          eb
                                                                                                                                             x                             x
                                                                                                                                             x                             x
                    speed was inputted from LORAN-C. The sampling time of                                                                    x                             x
                                                                                                                                             x                             x
                    the RCM was 1 minute, and that of the ADCP was also 1                                               125                  xx                            x
                    ininute with the pulse intermittence of 2,5sec. The results                                                              .0                                                            10
                                                                                                                                             x                             x
                    of Case 2 and Case 3 are shown in Fig.13. The values of                                          '0                      xx                                 Ix
                                                                                                                                               x                                                  x
                                                                                                                                                                                                  x
                    the current velocity obtained by the ADCP and the RCM                                            0  250                  -0      x                                            x
                                                                                                                     r@                      x                                                    x
                    at shallower depth than 140m were greater than 60cm/sec                                                                  X,                                                   x
                                                                                                                                             x                                                    x
                    and coincided with each other. And the both direction also                                                               x x                                                  xx       20
                                                                                                                     c-                      x                                                    x
                    coincided with each other. Thus, the coincidence of the two                                      LU                      x                                                    x
                                                                                                                        375                  -b,                                                  y
                                                                                                                                                                                                  X0
                    vertical profiles is an evidence that the ADCP system sat-                                                               x                                                    x
                                                                                                                                             x                                                    x
                                                                                                                                             x                                                    x
                    isfies the initial ahn as shown in Table 1. The results of the                                                           x                                                    x
                                                                                                                                             x                                                    x
                                                                                                                                             x                                                    x        30
                    four cases are drawn together in FigA4. That figure shows                                           500                  , I'-X' ''-, I...I                    I I 1 14,
                    the some variance around the solid line. It is difficult to ex-                                                          0so           100             0       180            360
                    plain the cause clearly, but we can consider some reasons as                                                             VELOCITY CM/e                 DIRECTION              deg
                    follows. The accuracy of the reference ship speed obtained
                    by the LORAN-C which was worse than the ADCP's; the
                    space averaged area by the ADCP was wider than that by                                              0                    CM q0CP x                     RCM     HDCP           x
                    the R-CM as the measured value by ADCP was averaged                                                                           rTT7-r-r
                    over the area among the four beams and the area along the                                                                xx                            x
                                                                                                                                                                           x
                                                                                                                                             x                             x
                    ship track during the mean time, on the other hand that                                             175                  xx0                           C@
                    ky the RCM was only averaged around the mooring; or the                                                                                                x
                                                                                                                                             x                             x                               10
                                                                                                                                             x                                                    x
                    direction sensor of the RCM might respond slower than the                                        L                       x                                 0                  X@
                                                                                                                     M                       x                                                    x
                    ADCP to weak currents. Therefore the variance did not                                            -0                      x )e                                  x
                                                                                                                     0S 350                  x                                                    x
                    show necessarily the accuracy of the ADCP. Lastly the tra-                                                                                                     0              xx
                                                                                                                                             x                                                    x
                    verse of the Kuroshio current using ADCP was successfully                                                                x                                                    x        20
                                                                                                                                             -x
                    measured and depicted in Fig.15.                                                                                         x                                                    xx
                                                                                                                     U-1 525                 xb                                                   x
                                                                                                                                             x                                     x
                                                                                                                                             X,                                    x
                                                                                                                                             x
                                                                                                                                             xx                                    x                       30
                                   30                                                                                   700                  [....1'1114,11111,11          1 ... xxlx I I 1       11 ....IA
                                              0                                                                                              0-50          100             0       180            360
                                                                   pulse width (@c)                                                          VELOCITY CM/8                 DIRECTION              deg
                                              E3
                               0    20 -                           7.5
                                                      0        015    a
                                                                      A
                                                              A 22.5                                                 Fig. 13                 Comparison between the velocity profiles by the
                                                      A               0
                                                      13           30                                                ADCP and the RCM. (a) Case 2, (b) Case 3
                                    10 -
                                                                   45

                               LO
                                    0                                  1       1                                     (a) so                  velocity                      (b)  direction
                                      0               10              20              30
                                                layer thickness (m)
                                                                                                                        60                   -                             70                     a
                    Fig.12 Standard deviation of received Doppler shift fre-

                                                                                                                                                                           so
                    quency versus rneasuring layer thickness for various pulse                                       U  40 -
                    widths.                                                                                                                                      d4C

                                                                                                                        20                                                 go
                    TABLE       2 . Parameters of the four test cases for conipari-
                    son between the ADCP and the RCM.                                                                                        20 40   60     so                LO                  100 270  360
                                                                                                                                             RCM                                   RCM
                        parameter                     Casel        Case2     Case3          Case4
                        ship speed (knot)             5            5         5                drift                  Fig.14 Scatter plots oftheADCP and the RCM data,.                                 (a)
                        pulse width (rnsec)           15           22.5      30                 30                   velocity (b) direction, solid circles show larger value than
                        layer thickness (m)           10           15        20                  15                  15clillsee obtained by the R.CM and triangles show smaller
                        depth range (M)               15-335       22-502    30-670 32-512                           than that.

                                                                                                             357

                                        40
                                        80
                                     120
                                     160
                                     200
                                     240
                                     280                                                                                            N
                                 E-  320                                               Mi
                                 a4                                                                                                     E
                                     360
                                     400
                                                                                                                                     50CM S
                                     440
                                                                                                      m      I I    I I I /A    I I.
                                     480

                                330055      46    N                                                                             34 0  22 96       N
                                139 42     , 1    E       Fig.15 Traverse section-of the      Kuroshio current over the         1350 39 18        E
                                                          Izu Ridge, the, solid lilies represent velocity vector. The pa-
                                                          railieters were used the same with Case3 in Table2.
                                  6 CONCLUSIONS                                                     7 ACKNOWLEDGMENTS

                  A long range ADCP has been developed, which can measure               The authors wish to thank to Mr. M.Gondou, Mr. Y.Asada
                  ocean current profiles and acoustic backscattering strength           and Mr.S.Maisuzawa for their great contribution to com-
                  in 32 layers tip to a depth of 400111. In the development the         plete the work. Mr. T.Tsuchya and Mr. Y.Ainitani are
                  followings were performed.                                            thanked for their assistance testing the transducer inodule,
                  (1) The 7OkHz transducer module of phased array type has              and Mr. M.Katou is also thanked for his computer draw-
                  been developed for measuring the open sea current.                    ing. And the members of the system design committee
                  (2) The advanced signal processing method based oil the               for this project are acknowledged for their valuable discus-
                  axito-correlation function was introduced. The method iiii-           sions and advises. This work was supported by the Science
                  proved the capability to derive the mean Doppler shift fre-           aild Technology. Agency in Japan under the special coor-
                  quency. It was confirmed the S/N become better l2dB than              dination funds for "Research oil the development of new
                  the zero cross method which we had been used.                         oceanographic research systems"
                  (3) The capability of the transducer and transinitter-receiver
                  unit were tested in the open sea. The received signal level
                  at the 500m depth was lOdB greater than the background
                  noise level.                                                                           8    REFERENCE
                  (4) The comparison between the ADCP and the RCM was
                  carried out in the Kuroshio current. The vertical current             (1) K.Okiilio,Y.Tstiji,S.Hisaiiioto,M.Okino and T.Einura,
                  profiles by the ADCP coincided with that by the RCM. And              1983, Three-Dilliensional Current and Scattering Strength
                  the traverse measurement of the Kuroshio was performed                Distribution Mapping System, Proceedings of Oceans'83,
                  successfully.                                                         301-305.
                                                                                        (2) F.D.Rowe and J.W.Young, 1979, An Ocean Current
                  From these results we consider that the ADCP has capabil-             Profiler Using Doppler Sonar, Proceedings of Oceans'79,
                  ity of measuring the open sea current. And the ADCP will              292-297.
                  be made use of by JAMSTEC as follows, the R/V NAT-                    (3) T.M.Joyce,D.S.Bitteriiiaii,Jr. and K.E.Prada, 1982,
                  SUSHIMA will be equipped with the ADCP in Dec.1988,                   Shipboard Acoustic Profiling of Upper Ocean Curreiits,Deep-
                  and the R/V YOKOSUKA which is a new mother ship of                    Sea Research, 29, 903-913.
                  a submersible research vessel for deep ocean has launched             (4) G.Kai,Y.Kuroda,S.Matsuzawa and K. Okuno, 1987,
                  July. 1988 and been equipped with the advanced ADCP.                  A Ship-niounted Acoustic Doppler Current Profiler, Pro-
                  The ADCPs are hoped to make clear the currents around                 ceedings of Toyohashi International Conference on Ultra-
                  Japan and in the Pacific.,                                            sonic Technology, 195-206.

                                                                                   358

                             THE ACOUSTIC DOPPLER CURRENT PROFILING SYSTEM AT AOML

                                 Doug Wilson, David Bitterman, and Carol Roffer
                             National oceanic and Atmospheric Administration (NOAA)
                          Atlantic Oceanographic and Meteorological Laboratory (AOML)
                                  4301 Rickenbacker Causeway, Miami, FL 33149

                            ABSTRACT                           doppler    shift    in   frequency    of     the
                                                               backscattered acoustic energy to estimate
                The  design and performance of the data        water speed relative to the ship in each of
           acquisition     and logging system of the           63 depth bins.   The Ametek DCP 4400 115 kHz
           Acoustic Doppler Current Profiler on the            ADCP installation on the Researcher (now
           NOAA Ship Malcom Baldrige are described.            the Malcom Baldrige) is located in a sea
           The     accuracy      of    absolute     current    chest  on a flat section of     the hull, near
           measurements is limited by our ability to           the keel about 40% aft. This installation
           determine ship movement and orientation.            has   shown little reduction         in signal
           Methods of processing TRANSIT satellite and         quality at high speeds or in rough seas.
           Global Positioning System navigational data         The   original DEC PDP 11/23 instrument
           are     evaluated.    methods    of precisely       controller/acquisition     system has since
           determining the ADCP transducer alignment           been replaced by a DEC microVAX II.            A
           relative to the ship are described and              schematic block diagram of the system is
           results shown.                                      shown in figure 1.
                                                                   Operator interaction with the system is
                           INTRODUCTION                        through    the CRT, which       also displays
                                                               operating parameters, single ping data, or
                AI paper in OCEANS 183 described.the           averaged profiles. The system is normally
           initial installation and early performance          run with a pulse length of 9.6 msec ( a
           assessments of an Ametek-Straza DCP 4400            nominal depth bin width of 6.4 meters) and
           3-beam acoustic doppler current profiler            a   ping rate of 1.76 sec.           The major
           (ADCP) on the NOAA Ship Researcher         Since    departure from suggested system default
           that time the profiler has been run roughly         parameters (based on early sea trials) is
           180 sea days per year, primarily in@ the            that the profile detection signal to noise
           equatorial Pacific ocean and the Caribbean          ratio is kept low (2 db), so that very few
           Sea.    This paper will focus on techniques         profiles    are rejected by       the system.
           developed to convert the basic ADCP product         Originally, doppler data from each ping
           (very many noisy single-ping profiles of            were stored.      Analysis    of this       data
           water velocity relative to a moving ship)           confirmed     the     manufacturer's       error
           into a useful oceanographic data set. ACIML
           scientists and other oceanographers have
                                                        '  t        CRT          500 MEGABYTE       9TRACK
           used   these   data   for large   scale Curren         TERMINAL          DISK
           mapping,      volume     transport      studies,                         DRIVE         TAPE DRIVES
           horizontal      momentum    and    heat      flux
           estimates,     and bulk     studies. of      eddy
                                                          2                         DEC
           viscosity    coefficients (Morrison    (1987)                                            DECNET 0
                                       88)3                                      MICROVAX 11        DECI
           Wilson and Leetmaa        (19    ; Leetmaa    and                        CPU           TO  K UNIT
           Wilson (1985   )4 ). The uses planned   for the
           data set determine the processing methods
                                                                   CESIUM
           to    some   extent;   we   generally    require        CLOCK        AMETEK STRAZA     TEMPERATURE
           current     estimates   on  moderately     large                       DCP 4400          SENSOR
           spatial    scales,  so   that ADCP    and    ship                     PROCESSOR
           navigation data can be averaged       for  10 to                                         SHIP'S
           30   minutes and mapped to grids     of 5  to 25                                      GYROCOMPASS
           kilometers by 10'meters.                                               AMPLIFIER         (HEADING)
                                                                                     TT
             ADCP INSTALLATION AND    DATA ACQUISITION                             3 BEAM
                                                                                 TRANSDUCER

                 Basic ADCP theory and operation are
                                                                   SATNAV

                                                                     t

                                                                    GPS

                                                                                  I t

           well described by Pinkel (1@80)5.             The   Figure 1.      Schematic diagram of the ADCP
           hull-mounted unit transmits a 115 kHz pulse         controller    acquisition system on the NOAA
           downward and outward, and measures :the             Ship Malcom Baldrige.

                                                            350, @ United States Government work not protected by copyright

                 estimates       (ping-to-ping standard errors of                  between          satellite    fix    locations.           The
                 32   cm s-1 at 6.4 m bin width).                Data from         difference       between locations is attributed
                 each ping is now           rotated from the          ship's       to a mean current            at the reference          level
                 reference frame to a fixed geographic frame                       (figure          2). These    currents       are added to
                 using an instantaneous heading value from                         the shear profiles to give one minute
                 the    ship's gyrocompass,           and    36 pings (63          averaged absolute currents, which are dead
                 seconds)        are averaged for storage to tape,                 reckoned again          to get accurate profile
                 lowering        the   expected        error      for     the      positions.
                 ensemble mean to about 5 cm s-'.                                        This       approach works well              but has
                  I Each         output       record       contains       the      limitations.            A     bad      satellite         fix,
                 one-minute averaged ADCP data (north                     and      especially if it closely follows another
                 east     components       for    63   bins     and bottom         fix,     can produce large errors in reference
                 track),     number      of    good samples        per bin    '    velocity.        Satellite fixes are not used if
                 output time,         parameter settings, average                  they have low or high elevations, require
                 ocean       temperature,       and all         navigation         excessive           iterations          for        position
                 information       received during the            averaging        determination,         or occur within         20 minutes
                 interval.       This can include up to 7 LORAN C                  of a previous good fix.                 Satellite fixes
                 or   GPS fixes.         An output       record is       1152      producing        'unreasonable,        reference       level
                 bytes    and up to five days may be stored on                     velocities       are also deleted.            The smaller
                                                                                   range of realistic velocities at 150 m
                 a   1200 foot,       1600 BPI,       9.track       magnetic       makes this a much easier field to edit than
                 tape.                                                             ship      speed       itself.        Reference         level
                      On     the present system, the            one minute         velocities       are spline fit           or averaged in
                 ,averaged data are also written to a disk                         space or time to produce a smooth field.                     A
                 every       two      hours     for near-real            time      fore/aft         transducer misalignment can cause
                 calculations of longer averages of absolute                       a     cross-track       bias     in    reference       level
                 currents.          With    the ADCP        controller /           velocities       and must be corrected before
                 acquisition       program locked in memory, the                   final       calculations        are    performed         (see
                 microVAX can also process the ADCP data                           Calibration).         Figure 3 shows an example of
                 from disk, log and plot data                from the CTD          reference level velocities from a cruise in
                 deck     unit,     and    run other        routine data           the Eastern Pacific.
                 analysis and      display programs.                                     Satnav position accuracy is dependent
                                                                                   on a proper estimation of ship speed during
                                 ADCP DATA PROCESSING                              a fix.           The ADCP provides speed input
                                                                                   (relative        to some subsurface reference
                      Principal ADCP data processing tasks                         level) to the satellite navigator for this
                 include further averaging to reduce the                           purpose.         An alternative would be to store
                 error in shear profiles, and estimating                           actual satellite Doppler data and reprocess
                 ship's speed to correct shear profiles to                         it using ADCP measured ship speed.
                 absolute velocity. The latter is dependent                              The major drawback to using satellite
                 on the type of navigation data available.                         navigation only is that the horizontal
                 very little of our work takes place in                            resolution of the absolute velocity field
                                                                                   is      limited       by     the distance           between
                 water shallow enough to estimate ship's                           satellite        fixes.       while this can make
                 speed by ADCP bottom tracking. When bottom                        accurate surveys of high horizontal shear
                 tracking is possible, the system is run in                        regions (fronts, for instance) impossible,
                 alternate        mode, where alternate                 pings      it is adequate for larger scale current
                 sample bottom and water doppler shifts.                           mapping applications.
                 information from each TRANSIT satellite fix
                 is stored, as are the most recent GPS fix
                 and      a mean LORAN-C position for each
                 one-minute ensemble. Additionally, all GPS
                 fixes (up to seven per ensemble) are stored
                 when     available.        When     LORAN      C  data      is              ........... TRUE COURSE      DEAD RECKONED COURSE
                 available, it may          be substituted for GPS.
                 Since most of our work is done outside
                 LORAN C coverage areas, and its accuracy is                                                              DEAD
                 generally less than that of GPS, we will                                           .................     RECKONED
                 discuss only techniques for estimating ship                         SATHAV                               POS
                                                                                      POS I
                 speed from GPS and satellite navigation.                                                                         DISPLACEMENT
                        The      primary source of ship navigation                                                                VECTOR
                 information          is    the      TRANSIT        (Satnav)                          MEAN REFERENCE    ..................
                 satellite       system.      Satnav fixes are stored                                 CURRENT VECTOR        SATNAV
                 in the ADCP data record at their output                                                                     POS2
                 time. Besides time and position, satellite
                 elevation and number of iterations required
                 to converge on a position are stored. One
                 minute averaged ADCP velocities relative to                       Figure 2.             Difference between ADCP dead
                 some deep reference level (around 150 m)                          referenced           and      satnav       positions        is
                 are integrated to dead reckon ship position                       attributed to current at reference level.
                                                                                                                          DEAD
                                                                                                                          RECKONE1
                                                                                                                          POS

                                                                                360

                             The ADCP System includes a Trimble                                                        averaged over each ADCP output interval;
                     4000A              Global        Positioning System                              (GPS)            this            speed          is used for               referencing when
                     locator as a navigation input. When three                                                         available.
                     or      four satellites are in view, the system                                                                   Preliminary,               near          real-time                data
                     provides               continuous position,                          time,           and          processing can be performed on the two-hour
                     ,speed values.                   Presently this                    is 8 to             12         disk            files at           sea,             although satnav speed
                     hours per day, but will ultimately be at                                                          determination can only be updated to the
                     all        times.            The unit is                  often augmented                         last            satellite           fix.            Generally all                 data
                     with a cesium frequency standard to provide                                                       tapes from a cruise are                             consolidated into a
                     accurate               time           input            when          only            two          sin,(jle disk                  file. for            final           processing.
                     satellites are in sight.                               This can increase                          During this phase, ADCP                             output times (based
                     GPS coverage by 4                    to 6 hours per day.                                          on the controller's clock) are corrected to
                            GPS output to the ADCP system is every                                                     agree with GPS times.                                 This is important
                     10      to 15          seconds, and                 the following are                             for dead reckoning between satellite fixes,
                     stored             in    the       GPS data               block on              tape:             and             for referencing profiles when the ship
                     time, latitude, longitude, altitude, speed                                                '       @is. maneuvering.                        After ship speeds are
                     heading,               number of satellites,                                 and a                determined                     for each             one minute                    ADCP
                     dilution               of precision               (DOP) value.                    Best            average,                       they are used to                reference the
                     estimates              of position accuracy are 7 to 15                                           shear           profiles           - GPS            or      LORAN C               take
                     meters                 (for             optimum                constellation                      precedence over satnav when available.                                               The
                     configuration and satellite elevations, and                                                       absolute                       velocities           are further averaged
                     accurate               altitude and time values in 2 and                                          over            10 to          30 minutes,            depending on                   the
                     3    satellite modes); accuracy                                  is reflected                     ultimate spatial resolution desired.                                            These
                     in     the         DOP value.                    Dockside            tests have                   -are            the            'basic units, of processed ADCP
                     shown         that 20 meters                     is a reasonable                    RMS           data.           They are often mapped onto regular
                     value.             Mean ship speed estimates based on                                             horizontal / vertical                               grids for               display
                     positions              10 minutes                apart would have an                              (see figure 5).
                     estimated error of 4 cm s                                     This accuracy                                       220-
                     can be approached by editing position fixes
                                                                                                                                           GPS        POSITION
                     during processing to eliminate very bad
                                                                                                                                                                                        A
                     positions,                and        by      estimating                the        mean                                           10 minute differen
                     position               of    a     1     minute ADCP record by                                                    200 . .......... 2 minute
                                                                                                                                                                differen
                                                                                                                                                                           ce
                     fitting a curve to all fixes obtained
                     during that interval.
                            Ship speed and heading output have .01
                                                                                                                                       180-
                     knot and 0.1 degree                          resolution.                 Velocity
                     accuracy (at zero acceleration) is quoted
                     at 10 cm s                       rms error.                 Thus 2 minute
                     averaging              (at    5 fixes / minute) lowers the                                                        160
                     expected speed error to 3 cm s-1, better
                     than               the      speed            based            on         position                                 220-
                     differentiation                    over          the      same          interval.                                   GPS VELOCITY
                     For      the standard secondary averages of ten                                                                                  10 minute mean
                     or fifteen minutes, the expected errorsare                                                                        200 . ..........2minute mean
                     about the same, but speed averages are less
                     affected               by outliers (figure, 4).                                       In
                     practice, the instantaneous velocities are
                     edited based on acceleration and DOP, and                                                                         180-

                     10 N-                                    . . . .                    . . .                                         160 - F'. ...... ......... ......... ............
                                                                                                                                       220-
                                               <
                                                                                                                                         ADCP BOTTOM TRACK

                         0                                                                                                                            10 minute mean
                                                                                                                                       200 . ..........2minute  mean
                                                                                   100 CM/S                            E
                     10 S                                                                                                              180-
                        140     W                  120 W                      100    W                    80   W
                                                         West Longitude

                                                                                                                                       160            ........  ........   ...... ..............
                     Figure 3.              Current velocities at 50 meters                                                            0              10  20               30    40          50          60
                     determined             by ADCP dead                    reckoning between                                                             Time in Minutes
                     satellite fixes, October - November 1987.
                     Vectors            begin at midpoints                          between             fix            Figure          4.             various estimates of ship speed
                                                                                                                                                      u
                                                                                                                                                      minute @MeCn
                                                                                                                                       @2.              "lute   Mea        n.

                     positions.                 Note presence                     of          tropical                 based           on GPS         information and ADCP bottom
                     instability waves in zonal sections.                                                              tracking.

                                                                                                               361

                     al   ADCP'Eastward Velocity                                        ADCP vs Pegasus
                     0-   3 N October 1987                                              Least Square Fit 0-200 rn
                                                                                     0

                   50-
                                                                                   100                   DEC 1983 U

                 100                                                                                     DEC 1983 V

                                                                                   LUU                   MAR 1986 V
                 150

                                                                                   300
                 200
                     140           130            120           110
                                                                                   400
                     b)   ADCP Northward Velocity                                      0      25     50     75     100
                     0-   3 N October 1987                                                Standard   Error cm/s

                                                                         Figure 6.         Standard   error of difference
                   50-                                                   between Pegasus and ADCP shear profiles,
                                                                         aligned for best fit over the upper 200
                 100,                                                    meters. From the Florida Straits.
                                                  0

                                                   0
                 150-                                                        During      studies     of    the Equatorial
                                                                         Undercurrent      in     the    eastern Pacific,
                               W
                                                                         comparisons       were     made    between      ADCP
                                                                                                                              7
                 200                                           .0( -     measurements     and moored current meters.
                     140           130            120           110      The ADCP value was the mean of all'data
                                                                         within + 7.5 miles along the equator of the
                                                                         mooring location; the current meter value
                                                                         was a 24-hour average. The mean (standard
               Figure 5.          (a) Zonal and (b) meridional           deviation) of the velocity differences over
               velocity   fields at 30 N, October 1987.          All     69 comparisons in the upper 160 meters were
               profiles      were   referenced using TRANSIT             3.3   (14.1)     cm  s'I  for   eastward and      1.5
               satellite     data;   fifteen minute       averages       (9.4)   cm s-1 for northward velocity.          Most
               were mapped to a         0.25 degree x     10 meter       of   the larger differences     1occurred     in the
               grid for contouring.                                      high shear (up to .03 s ) regions above
                                                                         the EUC core, where differences from the
                                                                         nominal     mooring      depths      could     change
                                                                         eastward velocity significantly. The mean
                                                                         (standard deviation) U difference at 160
                      ADCP ACCURACY AND CALIBRATION                      meters was -.6 (13.1) cm s-      I ; at 250 meters
                                                                         it     was   -18.5. (10.8) cm            s- 1.  most
                     .Differences in time and space scales               measurements. to date suggest that 200
               make comparisons between ADCP data and                    meters is the maximum depth of accurate,
               other current measurements difficult.               In    measurements for this installation.
               OCEANS 1836, agreement was shown between                       Given a high enough level of back-'
               individual Pegasus and ADCP profiles to                   scattered      energy     for    adequate signal
               depths exceeding 250 m. Further studies of                processing, the inherent random error in
               several hundred such comparisons revealed                 the doppler current speed estimate can be.
               that    the   two   profiling methods      agree to       reduced    to    reasonable    levels     (  < 2    cm
               within about 5 cm s-1 when shear profiles                 s-1 ) by averaging for as little as five
               are least-square fit in the upper 200 m                   minutes.         Longer        averaging,       when
               (figure 6), but agreement rapidly decreases.              appropriate to the fields being             sampled,
               below 200      meters.      In a    comparison      of    reduces    this still     further.     The   primary
               absolute    velocities at      9 stations      across     obstacle    to accurate current measurements
               the Florida Straits (fipure 7), the ADCP                  is contamination by ship motion.             The net
               measured     about 10    cm s-     lower than      the    effects    of nearly periodic oscillations of
               Pegasus       in    the    northward       velocity       the   ship's     fore/aft,    port/starboard, and
               component,     but  the two agreed on the small           vertical axes        (roll,   pitch, yaw)     due to
               mean     deep westward velocities            in the       wave action are small and can also be
               eastern Straits.                                          reduced by averaging.          Larger biases       are

                                                                     362

                       0-                                                               introduced into the sy                 stem by transducer
                         a                                                              misalignment           -   the    transducer coordinate
                               _5   0
                                                                                        system is rotated relative to that of the
                   50                       Ao                                          ship - or by individual beam misalignments
                                                                                        within the transducer assembly.
                                        .5                     0                              At a ship speed of 10 knots, a 10
                                                      .5                                misalignment of the transducer about the
                   100.               0                                                 yaw axis introduces a cross track velocity
                                                                                        error of 9 cm S                        The error due to
                   ISO-                                                                 pitch-axis          misalignment is smaller and
                                    5                                                   takes the form of a constant multiplier.
                                                                                        Fortunately,           misalignments            are       nearly
                                                                                        constant characteristics of an installation
                   200                                                                  and can be estimated and corrected for
                       80.0        79.8          79.6           79.4         79.2       during data processing.
                       0-                                                                  . For this calibration discussion we will
                         b                                                              use the coordinate transforms and equations
                                 .5                                                                                       (1988)8       and modified
                                                       0                                derived        by Joyce
                   50'                                                                  slightly by Pollard and Read (1988)'. The
                                                                                        ship position is determined and the current
                                                            0                           velocity         desired in a true coordinate
                   100'                                                                 system (X,Y) with X and Y positive eastward
                                                                                        and northward. The ADCP unit lies in an
                                                                                        (X',Yl) system, rotated @ 0 clockwise. A
                              .5                                                        factor A scales velocities in the ADCP
                   150-
                                      0          0                                      reference        frame      and     includes effects            of
                                                                    -10                 pitch         misalignment             (proportional            to
                   200                                                                  (cosE))-'            (U1,V1)       are       east  and      north
                       80.0        79.8          79.6           79.4         79.2,      velocities         in the (X',Yl) frame,              found by
                                                                                        vector decomposition of the ADCP velocities
                       0-                                                               using heading from the ship's gyrocompass.
                       .C
                                                                                        Subscripts (w,d,s) refer to the velocities
                                                                                        of water (current relative to the ground),
                   50-
                                       180                                              doppler (velocities obtained from the ADCP,
                                                                                        relative         to the ship), and ship (the
                                                                                        absolute velocity of the ship).                             These
                   100-                        160                100                   three         quantities       are     connected by the
                                                         120         so                 equations:
                                                 140
                   150-          60   120                                               UW = Us       + A ( U  d Cos           +     Vd sin
                                                                                        V = V         + A (-U sin              + V      Cos
                                                                                         W                                           d
                   200
                       80.0        79.8          79.6           79.4         79.2             The     simplest calibration              method     is   t o
                       0-                                                               compare       bottom track (U          d) to    U determined
                       .d                                                               from precise location measur&ments (GPS,,
                                                                                        LORAN C). This eliminates U so that
                                       180                                                                                           W
                   50-                                                                        tan-' <V U             U -V > /        <U U + V -V >
                                                                     80                                   d            d    S           d          d
                                              60    140                                 A     -<U     -U. + V     V@> / <(U )        2  + (V )  2> coso
                   100-                                                                               d        d                 d          d
                                                       10                               where         < > represents time-averaged values,
                                                             100
                                                                                        generally         over a          calibration run               at
                   1550          60                                                     constant course and speed.
                                                                                              Long straight runs in shallow water
                                     00                                                 with          accurate position information are
                                      I
                   200                                                                  surprisingly           rare        for       large research
                       80.0        79.8          79.6           79.4         79.2       vessels.         Immediately           following      the ADCP
                                                                                        installation in the Researcher in 1982,
                                                                                        four 20 - 40 minute runs comparing bottom
                                                                                        track to LORAN C estimated 0 =                   -2.67* (a
                                                                                                                                        10
                                                                                        0.79), A= 1.0000 (Daubin, 1983)
                Figure 7.               Mean currents in the Florida                          This value of @ appeared to overcorrect
                Straits,          December         1983.        (a)     Eastward        when applied to actual data sets.                     A simple
                velocity,         Pegasus       (b) Eastward velocity,                  method        of misalignment                estimation        was
                ADCP         (c) Northward velocity,                     Pegasus        adopted that utilized existing data and did
                (b) Northward velocity, ADCP. Based on 12
                repeated sections of continuous ADCP data
                and 9 discrete Pegasus locations.

                                                                                   363

                            not     require          special           calibration                runs.           in       the AOML             logging         system          is that no
                            Since    reference velocities                       at depth were                     values         of heading are                 stored in the ADCP
                            routinely estimated as a                          residual between                    data          files.          Rosro           (1985)11            described
                            satnav        fixes        and         ADCP dead                reckoned              typical          gyrocompass errors; while latitude
                            position, they were consistently biased due                                           and           velocity             errors            are          routinely
                            to ADCP misalignment.                   Using the assumption                          compensated,                  the   acceleration error                        (or
                            that over the course of many cruises there                                            Schuler          oscillation) is                  a complex damped
                            should be no             correlation between                      current             oscillation which changes with,each course
                            velocity         at reference depth                          and ship                 change and may have an amplitude of a
                            heading, the estimated reference velocities                                           degree or more.                 The solid line in figure 8
                            (usually at              200    m) were           decomposed into                     shows         the estimated f, based on the second
                            along/across             ship     track           components.             For'        half of a north-south calibration run, as a
                            ten     cruises          in       1983/84         this        showed a                function of time following the 1800 turn to
                            misalignment             (sin-' <cross-track component                                north.           The dashed              line       is the estimated
                            of  reference            velocity> / <ship speed> ) of                                gyrocompass                   error      due      to      accelerations
                            -1.50      +      0.5.           This         value         gave more                 during           the          1801       course         change.               The
                            reasonable           results           and was used until                             assumptions                   made       for        reciprocal                run
                            further           calibration                 runs        could             be        calibrations                  (constant current velocities)
                            performed.                                                                            become less              likely as the runs become long
                                "Water track" runs in 1986                            centered on
                            a   value        of t = -1.25*.                         Water track
                            calibration assumes                    that       currents remain                              -3.0                 -2.0               -1.0                   0.0
                            constant during.the course of a run that
                            crosses an area several times at different                                                     0
                            headings; f and A are determined such that
                            they minimize the current differences among                                                                         ........................................................
                            tracks.        The equations for 0 and A are the                                           100-                             ......
                            same    as for bottom track,                      with velocities                                          rotation
                            U   and U            replaced by the corresponding
                                                                                                                                       constant
                            d
                            differences from their ensemble averages:                                                                                 .... ..............
                            @=tan_'<SV     d   -SU   B-SU  d  -Vs>/<SU        d.  &U,+&V      d.   &V,>                200             ............ ... ............
                            A=-<6U -SU +&V .&V >                     <(&U )     2 +(6V )      2  >Cost                 300
                                    d       S        d                        d            d                               0.98                 0.99                1.00                 1.01
                            where 6U =       U - <U>.
                             I Since water track                     calibration            requires
                            course        changes, the method                           is easily                 Figure 9.                     Depth dependence of 20 minute
                            contaminated by ship heading errors. The                                              mean t and           A during a water-track calibra-
                            ship's gyrocompass reading at the time of                                             tion run in November 1987.
                            each ping is used to rotate from transducer
                            reference frame to earth reference frame
                            for ping ensemble averaging. An oversight                                                      0.

                                                                                                                           0.5-

                                 0.0-
                                                                                                                       c   0.4-
                                                                                        calculated                     0
                                                                                        measured
                                -0.5                                                                                   @2  0.3-
                                                                                                                       0
                            fn
                                                                                                                           0.2

                                                                                                                           0.1
                                 1.5                                                          . .....
                                                                                                                           1.00-
                                                                                                                                       A        .989            .002
                                -2.0 -1 r r ...
                                       0         10        20          30       40          50         60              C
                                                                                                                           0.99
                                                       Minutes following turn                                          C
                                                                                                                       0

                                                                                                                           0.98
                            Figure 8.            Estimated misalignment angle                           of                      0               30              60            90              120
                            transducer assembly (t) vs. time after 1800                                                                              Time in      Minutes
                                                                                                                                                ........................
                                                                                                                                           tion
                                                                                                                                       rota st
                                                                                                                                       con      ant

                                                                                         me
                                                                                            a

                            turn in calibration run (solid line),                                      and
                            predicted gyrocompass error (dashed line).                                            Figure 10.               Calibration            constants t and A,
                            Error is the sum of the Schuler damped                                                versus           time in              minutes,             based on a
                            oscillation and an empirically determined                                             bottom-track                       GPS calibration run in
                            linear slope.                                                                         November 1987.

                                                                                                            364

             enough to let the oscillations disappear.                          REFERENCES
             In the absence of better ship heading
             information     (presently    available,     but   1 .  Bitterman,   D.  and D.    Wilson,    1983.
             costly)     the    next   version    of     ADCP        Ocean      Current   Profiling     with    a
             acquisition software will store heading so              Shipboard Doppler Acoustic Backscatter
             that    a   first     order   correction     for        System.    IEEE Proceedings of OCEANS
             acceleration    error may be made during                183, pp. 27 - 31.
             processing.                                        2.   Smith, Orson P. and J. M. Morrison,
                 A new ADCP transducer was installed for             1987.   Shipboard ADCP Data Applied to
             one  cruise only in October 1987.       A deep          Transport     Studies   in    the  Eastern
             water calibration run had to be cut short               Caribbean.    abstract in EOS, Trans.
             and was again contaminated by gyrocompass               Amer. Geophys. Union 68(44), p 1305.
             errors   (figure    9).  This   run  showed a      3.   Wilson,    D.  and A.      Leetmaa,   1986.
             strong depth dependence in the estimated                Acoustic Doppler Current Profiling in
             misalignment, especially below 170 meters,              the Equatorial Pacific in 1984.
             suggesting weak returns below this level.               to appear in J. Geophys. Research
             A constant speed bottom-track/GPS run was          4.   Leetmaa, A. and D. Wilson, 1985. Near
             made later in this cruise to estimate the               Surface Circulation Patterns in the
             misalignment. Values derived from this run              Eastern Equatorial Pacific.        Progress
             (@ = .37 + .1 , A - .989 + .003; see figure             in oceanography 14, pp. 339 - 352.
             10) were used on the entire data set.              5.   Finkel, R., 1980.       Acoustic Doppler
                                                                     Techniques.    In Air-Sea Interaction,
                      SUMMARY AND FUTURE PLANS                       Instruments and Methods, F. Dobson, L.
                                                                     Hasse, R. Davis, eds. pp. 171 -200.
                 In   theory    and    in practice,       the   6.   Bitterman,   D.  and D.    Wilson,    1983.
             ship-mounted ADCP instrument is capable of              ibid.
             measuring current shear profiles with an           7.   Wilson, D. and A. Leetmaa, 1988. ibid.
             accuracy acceptable to most oceanographic          8.   Joyce,    T.,     1988.      On    in-situ
             applications.      Factors    which     further         "calibration"    of shipboard      ADCP's.
             degrade absolute measurement accuracy are               Submitted to Journal of Atmospheric and
             dependent     primarily     on     installation         oceanic Technology.
             characteristics and processing methods, in         9.   Pollard, R. and J. Read, 1988.             A
             particular measurements of the alignment                method   for calibrating       shipmounted
             and relative motion of the transducer and               Acoustic Doppler Profilers, and the
             true    reference     frames.     This     paper        limitations        of      gyrocompasses.
             describes how we at AOML are routinely                  Submitted to Journal of Atmospheric and
             dealing with these problems. Individual                 oceanic Technology.
             institutions are independently developing          10.  Daubin, S., 1983.       Effects of Ship
             their shipboard ADCP installations, each                Notion on the Output of a Tribeam
             with different constraints, and there is a              Acoustic . Doppler Current       Profiling
             recognized need for information flow within             System. Technical Report DSC TR 02-83,
             the ADCP user community.                                Daubin Systems Corp., Key Biscayne, FL.
                 one factor emphasized in our approach               45 pp.
             has been to record as much high-quality            11.  Kosro, P. M., 1985. Shipboard Acoustic
             navi.gation data as possible, in an easily              Current Profiling During the Coastal
             accessible format. By utilizing features                Ocean   Dynamics Experiment.       Scripps
             like   the ADCP/satnav link,        an atomic           Institution of oceanography 85-8, 119 p
             frequency    input    for    GPS,   and    high
             resolution (up to seven per minute) GPS and
             LORAN   C position logging, we maximize
             navigation input and quality.        Navigation
             data    is    extensively     edited     during
             post-processing;      this    is   made    more
             efficient   by compatibility between our
             controller/logger      and    our     lab-based
             processing computers.
                 The next generation of shipboard ADCP
             acquisition and processing software will
             integrate   the    ADCP/navigation      logging
             system with a microVAX based shipwide data
             acquisit:ion    system.    This   will     make
             gyrocompass    and other attitude        sensor
             information available for post-processing,
             and provide a framework for other updated
             sensors. New sensor emphasis would be on a
             deeper-reaching ADCP transducer and a more
             stable gyrocompass or other ship's heading
             indicator.

                                                            365

                                    MAPPING THE SLOPES OF EXPANDING CONTINENTAL MARGINS

                                                         Richard B. Perry

                                             NOAA National Ocean Service (N/CG224)
                                                    6001 Executive Boulevard
                                                       Rockville. MD 20852

                                 ABSTRACT                             covering waters out to 600 meters deep. Plans
                                                                      for the next year include a Norfolk-based Class
                Modern mapping systems, such as GLORIA which          III NOAA ship to be equipped with a multi-beam
                provides imagery over a wide area, and Sea Beam       system capable of operating to 1,000 meter
                which provides swaths of detailed soundings,          depths.    As of July 1988 the NOAA multi-beam
                allow us to take a new look at sea floor              surveys, which utilize precise navigation
                morphology on and near the base of continental        systems, have provided total coverage of
                and insular slopes. Sediments are transported         approximately 45,000 square nautical miles of
                down the slopes in canyons, as well as in             the sea f loor in the EEZ.        These data are
                gravity slides, with much of the material             gridded at 250-meter intervals and are
                winding up in large fans.      These sedimentary      contoured for 1:100,000-scale maps using Radian
                deposits subsequently are uplifted, expanding         Corporation CPS-1 routines. With the exception
                the continental margins seaward.      One set of      of small     areas around Cordell Bank off
                uplift structures with possible economic              California and Loihi Seamount off Hawaii, the
                potential, which can be defined by Sea Beam in        data remain classified at the request of other
                great detail, is a large field of diapirs in          agencies.
                the Gulf of Mexico north of the Sigsbee
                Escarpment.    Examples of uplift along the           The NOAA surveys are coordinated closely with
                tectonical ly- active northern California and         the Geological Survey of the U.S. Department of
                Oregon-Washington coasts also are discussed.          the Interior (USGS).      A joint project office
                It is concluded that       the uplift of the          has been established by NOAA and the USGS, with
                tectonically-active areas  results from material      staffing by personnel from both agencies. The
                pushing up from below,     generally associated       USGS has concentrated on reconnaissance surveys
                with earth expansion.                                 using the GLORIA long-range side-scan system,
                                                                      and atlases showing the GLORIA images off the
                             INTRODUCTION                             West Coast (EEZ-SCAN F34 Scientific Staff, 1986)
                                                                      and the Gulf of Mexico and Eastern Caribbean
                The National Ocean Service (NOS) of the               Areas (EEZ-SCAN 85 Scientific Staff, 1987) have
                National Oceanic and Atmospheric Administration       been published.        The atlases contain a
                (NOAA) is continuing its program to survey the        description of the GLORIA system, which can
                Exclusive Economic Zone (EEZ) using multi-beam        image a swath of the sea f loor up to 60 km
                echo sounding technology.     The survey systems      wide.     They also show seismic reflection
                and processing methodology have been reported         profiles, which are very useful to marine
                at several previous OCEANS conferences (Hill          geologists in interpreting the GLORIA imagery
                and Lockwood, 1987; Matula, 1986; Perry, 1982;        and Sea Beam maps.
                Perry, 1985, Pryor, 1985).      An NOS plan for
                mapping the EEZ (National Ocean Service, 1987)        This paper will describe some of the mapping
                which describes the survey systems and areas to       results, but it will of course suf fer by not
                be covered is available by contacting the             being able to show the classif ied Sea Beam
                writer.                                               data. As a substitute for the Sea Beam maps,
                                                                      seismic reflection profiles from the USGS and
                There are four NOAA ships working at least part       others will be used to illustrate some of the
                of their field seasons with the EEZ survey            major points concerning uplift off the West
                program.   NOAA has equipped two Seattle-based        Coast.    By comparing features covered by both
                Class I ships (SURVEYOR and DISCOVERER), and          Sea Beam and GLORIA in the Gulf of Mexico we
                one Norfolk-based Class II ship (MT. MITCHELL)        can get a better appreciation of the strengths
                with Sea Beam systems. The Sea Beam system can        and the weaknesses of the,two systems, as well
                cover a swath equal to approximately 75 per           as how they complement each other.       It should
                cent of the water depth with 16 beams.         The    be realized that both GLORIA and Sea Beam are
                Seattle-based Class III NOAA Ship DAVIDSON     has    used as general reconnaissance mapping tools,
                the Bathymetric Swath Survey System            for    and that more detailed investigations are

                                                                   366 United States Government work not protected by copyright

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                                                                  90*

                                                         0       200  400   600 KILOMETERS
                                                         i       II   II   I I
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                           Figure 1. Generalized bathymetry           (in meters) and subsea features
                          of the Gulf of Mexico. From EEZ-SCAN 85 Scientific Staff, 1987.

             needed for resource development and scientific           sediment cover increases with proximity to the
             studies.    A major focus of the paper will be           Upper Mississippi Fan as evidenced by the
             the author's interpretation of the origin of             structures having gentler relief on the western
             some coastal margins which have been surveyed            side of the survey area in the vicinity of the
             by Sea Beam.     Some of the ideas relative to           Fan.   The surveys were run in water depths
             uplift on an expanding earth differ from                 ranging from about 800 to 1900 meters.
             conventional concepts of underthrusting at
             continental margins on an earth of a fixed               A check with the GLORIA atlas covering the same
             size, and they should be regarded as those of            area (Sheet 16, EEZ-SCAN 85 Scientific Staff,
             the author rather than as an official NOAA               1987) showed that the GLORIA system had picked
             position on the subject.                                 up portions of some, but not all of the
                                                                      circular structures.      The GLORIA side-scan
                            GULF OF MEXICO                            images, which cover a wide swath of sea floor
                                                                      from a single tow fish, depend upon sea bottom
             The NOAA Ship MT. MITCHELL began Sea Beam                features with good reflectivity. The result is
             surveys in the Gulf of Mexico in 1988.           The     that GLORIA tends to pick up the portions of
             first surveys were over the Upper Mississippi            the circular structures       which are oriented
             Fan (see Figure 1), and there were problems in           approximately perpendicular to and close to the
             getting a good echo return from the gas-charged          sound source, but gets a weak return from
             Mississippi Fan sediments.       Similar problems        portions of the circular structures that are
             are common on the shelf and upper slope near             oriented approximately parallel to and are
             the Mississippi River.       The vessel was then         remote from the sound source. The overlapping
             shifted to the east in the       area between the        Sea Beam swaths, which are generated from a
             Upper Mississippi Fan and the    Desoto Canyon.          ship passing almost directly above the
                                                                      circular structures, give an excellent
             Every once in a while a systematic survey                quantitative data set to map the features. The
             program will turn up something very interesting          trade-off is that Sea Beam may take weeks to
             when it is least expected, and the MT. MITCHELL          cover an area that GLORIA can image in a single
             hit the jackpot.        The survey shows many            day.  The GLORIA imagery also is excellent in
             approximately circular structures ranging in             showing the areal extent and transport
             size from 2.5 to 9 nautical miles in diameter.           mechanisms of sediments which have been moving
             In a few cases the circular structures abut,             down the continental slope into the deeper
             sometimes with deformation of each structure,            waters of the Gulf.
             and a small canyon between them. The largest
             circular structure has a scarp of about 300              The circular structures were interpreted in the
             meters on its southern side, and it rises a              GLORIA atlas as diapirs, similar to ones to the
             total of 500 meters from the sea floor on the            west of the Upper Mississippi Fan which have
             south to its intersection with the continental           been confirmed by drilling to be salt domes. A
             slope on the north.        Many of the circular          discussion of the regional geology in the
             structures are covered by a ramp of sediments            GLORIA atlas indicates that loading of Tertiary
            Jeading down from the continental slope onto              sediments onto an underlying salt layer of
             the top of the structure.          The amount of         Jurassic age has resulted in diapiric intrusion

                                                                  367

               by the salt.    The GLORIA atlas shows a large         closer look be taken at two areas where those
               area on the continental slope north of the             sediments are being uplifted, (1) an area off
               Sigsbee Escarpment to be covered with diapirs,         northern California just to the south of the
               presumably of salt origin. . The atlas also            Mendocino fracture zone, and (2) an area of the
               points out that seismic profiles across the            lower slope off the Oregon-Washington coast.
               escarpment by Amery (1969) suggest that a wedge
               of salt is overriding sediments that were              The Gorda Escarpment represents the face of a
               deposited in the deep waters of the Gulf.              raised block of sea floor, the Mendocino Ridge,
               Sweet (1986) reports that certain                      on the south side of the Mendocino fracture
               undercompacted shales in the central and               zone of f Cape Mendocino.    The Mendocino Ridge
               western parts of the Gulf have deformed in a           has extended the continental margin for more
               manner similar to the salt, and are responsible        than 60 nautical miles off Cape Mendocino. A
               for some of the ridges, swells, and diapirs.           seismic profiles of the uplifted block is shown
               We thus have a general picture of salt and             in Figure 2. The block has been shoved upward
               shale structures moving upward through the             by forces acting from below, producing an
               sediments which have come down the continental         escarpment on the order of 1,000 meters in
               slope, lifting the sediments as they go, and at        elevation. There are no indications that the
               the same time the edge of the salt expanding           Mendocino Ridge block is overriding the sea
               outward as it overrides the deeper sediments in        f loor to the north.     In fact, the Mendocino
               the Gulf.                                              Ridge block appears to be permanently welded to
                                                                      the King Mountain area to the east, with little
               While it has been known for many years that the        evidence that the San Andreas fault passes
               continental slope in the Gulf of Mexico, has           between them.    There is considerable historic
               many salt domes, it was not realized until.now         seismic activity along the Gorda Escarpment,
               how effective Sea Beam can be in defining              supporting the idea that the Gorda Escarpment
               uplift structures of that type.           If maps      may be continuing its uplift.
               showing the structures could be released, they
               might assist private industry in targeting             Note that the sediments on the back side of the
               areas for detailed geophysical investigations.         block in Figure 2 are being dissected by
               Because there is an existing satellite                 valleys.    These are canyons, including the
               navigation system with 24-hour coverage, it            Delgada and Vizcaino Canyons, which apparently
               should be possible for Sea Beam to map the             have formed  during and since the raising of the
               large area of diapirs located to the north of          block. The   Sea Beam maps show that the canyon
               the Sigsbee Escarpment.           The petroleum        systems bear no apparent relationship to the
               discoveries on several Green Canyon blocks             river systems an the adjacent land, where the
               suggest that the deeper waters of the Gulf of          King Mountains rise from a steep cliff near the
               Mexico may be very promising.           While the      shoreline.    There are some incipient canyons
               present price of oil and the cost of deep-water        forming part way down the continental slope,
               production may not add up for immediate                with no connection to other drainage patterns.
               development, long-range prospects look good.           Few canyons head all the way in at the
                                                                      coastline, but those that do, such as Delgada
               Good bathymetric maps will be needed not only          Canyon, appear to intercept the longshore
               as a framework for detailed geophysical surveys        sediment transport and then carry the material
               and pipeline routings, but also for related            seaward down the canyon. The canyons carrying
               scientific studies. In addition to their well-         more material tend to have well-developed U-
               known presence on ocean ridges, there are              shapes, with almost flat, gently sloping
               reports of chemosynthetic organisms (vent-type         floors.    Noyo Canyon cuts into the uplifted
               communities) in the Gulf of Mexico (Brooks.and         block, and then heads along the strike of the
               others, 1985; Grassle, 1985).       These include      San Andreas fault as it passes along the edge
               some at a petroleum seep at 700 to 800 meters          of the continental shelf off Fort Bragg.
               on the Louisiana slope, and some    at a depth of
               3266 meters at the base of the Florida                 The point is that in a geologic sense there is
               Escarpment. It is possible that'methane which          relatively recent, probably currently-active,
               is collected into commercial hydrocarbon               uplift of the continental margin along the
               deposits is derived both from normal biogenic          northern California coast.        The uplift is
               processes in sediments and from non-biogenic           extending the continental margin seaward. That
               processes deep within the earth. Since uplift          uplifted area is being dissected by young
               structures provide conduits for fluid migration        canyons whose patterns bear no relationship to
               upward, as well as structural traps, it is             the drainage on shore.
               important that we map them.
                                                                      Shifting northward to the Oregon-Washington
                               WEST COAST                             continental margin, there is both a continental
                                                                      shelf and an extensive lower slope area
               The GLORIA imagery (EEZ-SCAN 84 Scientific             dominated by a series of ridges which roughly
               Staff, 1986) and Sea Beam maps for areas off of        parallel the strike of the continental margin.
               California, Oregon, and Washington have                The ridges generally tend to be higher in
               provided good definition of canyons and slumps         elevation on the eastern, or landward, side of
               which are transporting sediments down the              the area. Where the trend of the continental
               slopes. It is appropriate in this paper that a         margin changes, the trend of the ridges

                                                                   368

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                                                  Figure 2. Seismic profile of the Mendocino                                               Ridge off Cape
                                                  Mendocino. From EEZ-SCAN 84 Scientific Staff, 1986.

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                                                between 46* 501 and 470 201. Seconds are two-way travel times.
                                                Portion of Sheet 26, McClain and others, 1984.

                                                                                                        369

                changes, with the ends of the ridges                    fluids, and gases generated deep within the
                interfingering much like interfingering                 earth.   These are the same fluids which are
                spreading centers on an ocean ridge.             The    being discharged at spreading centers on ocean
                uplifted nature of these ridges is shown in the         ridges, where large plumes of discharged
                seismic profiles taken off the Washington coast         material have been found during the last few
                in Figure 3 (From McClain and others, 1984).            years. Because similar materials are rising at
                Note the incipient uplift beginning in the              uplifting continental margins, there should be
                offshore ocean basin sediments in the top               increasing reports of vent-type chemosynthetic
                profile.                                                communities as we study the base of continental
                most of the sediment movement across the area           margins in greater detail.
                of ridges tends to go from basin to basin in            The concept of an expanding earth has of course
                gaps between ridges. Other sediments move down          been around for a long time, and it has been
                the major distributary canyons such as Astoria          .summarized in books such as those by Carey
                Canyon off the Columbia River.           Once the       (1976).   The reasons for the earth expansion
                sediments reach Cascadia Basin they are carried         are not clear.        Reconstructions of the
                along the trend of the continental margin by a          fragments of the earth's crust into Pangaea can
                series of sea channels, and then deposited in           reduce the earth to 80 per cent of its present
                the basin near the foot of the slope.           This    size in the late Triassic-early Jurassic (Owen,
                trapping of sediments near the foot of the              1976). Others have reconstructed the fragments
                continental slope results from the tilt of the          on an earth 75 per cent of its present radius
                sea floor upward toward the Gorda and Juan de           (Kenneth Perry, personal communication).
                Fuca Ridges. The GLORIA images show large areas         OCEANS '88 is probably not an appropriate forum
                of sea floor near the Juan de Fuca Ridge to be          for an in depth discussion of such concepts,
                almost devoid of sediment cover.                        but it should be pointed out that there are
                                                                        certainly other alternatives to sea floor
                The boundary of the continental margin                  spreading on an earth of fixed size.
                apparently is advancing seaward (westward) by
                uplifting the thicker sediments near the foot           The implication of an expanding earth model is
                of the slope into a succession of ridges, each          that the sea floor basins, which have all been
                one forming further to the west.        The uplift      formed 'since the Triassic, are relatively
                probably results from major regional tectonic           passive elements which are created at spreading
                forces, and not from salt or shale diapirs.             centers as the earth increases its
                Griggs and Webster (1986) however, do report            circumference. Younger sea floor is formed on
                some shale "pillows" on seismic profiles in the         an earth of greater diameter, so older sea
                Coos Bay, Newport, and Astoria areas, as well           floor will be found at greater'ocean depths.
                as elongate shale diapirs penetrating upward to         This is quite the opposite of the notion that
                the sea floor in the Willapa area.                      older sea f loor cools so that its depth is
                                                                        proportional to the square root of its age.
                           PROCESSES OF UPLIFT                          Since the sea f loor closest to the Oregon-
                                                                        Washington margin is older than that to the
                The uplift of the salt and shale diapirs in the         west near the Gorda and Juan de Fuca Ridges,
                Gulf of Mexico is relatively straight forward.          the sea floor slopes upward toward those
                It.is a matter of less dense materials rising           Ridges.   That sea floor is just sitting there
                slowly toward the surface while the loading of          passively as the earth expands, and it is not
                sediments provides hydrostatic pressure. Most           being fed under the west coast of North America
                of the salt diapirs in the Gulf are roughly             on a "conveyor belt". The sea floor near the
                circular, suggesting the absence of regional            continental margin, where the sediments are
                tension or compression that might align the             thickest, may be dropped down due to loading
                diapirs into linear ridges.                             from sediments and from the newly-upthrust
                The uplift along the Mendocino Ridge, as well           ridges moving onto it.
                as the Oregon-Washington coast, results from            There is an overthrust of sorts as the
                broad regional forces.       The writer believes        continental margin expands by uplift over the
                that the dominant horizontal forces acting in           adjacent ocean basin.      The earthquakes along
                the crust and upper mantle near the uplifted            the classic Benioff zone (Benioff, 1955)
                ridges is tension acting perpendicular to the           reflect the movement of the continental block
                trend of the ridges.         The tension allows         upward over the oceanic block. The result is
                segments of the earth's crust to push upward            compressional seismic first-motions along the
                during earth expansion, with the linearity of           Benioff zone, much as in the underthrust model.
                the features being determined by the stress             This means that those who would make a case for
                field.    The same tensional and uplift forces          underthrusting at continental margins and
                have formed most of the relief in the western           island arc trenches have the sense of motion of
                United Stater., pushing up the Rocky Mountains.         the blocks correct, but that there is no long
                As the blocks are thrust up near the surface of         "conveyor belt" pushing material beneath the
                the earth, they may overthkust and fold                 continents or island arcs. Uplift results not
                adjacent sediments and rocks.                           frcm underthrust material, but rather from new
                The uplift probably comes from magma, other             material moving upward as the earth expands.

                                                                    370

                            CONCLUSIONS                           EEZ-SCAN 85 Scientific Staff, Atlas of the U.S.
            Sea Beam maps and GLORIA images are excellent         Exclusive Economic Zone, Gulf of Mexico: U.S.
            tools for studying the development of                 Geological Survey Miscellaneous Investigations
            continental slopes, particularly when used with       Series I-1864-A, 1987, 104 p.
            other data such as seismic reflection profiles.
            Sea Beam can be used to map large areas of            Grassle, J.F., Hydrothermal vent animals-
            diapirs in the Gulf of Mexico. The diapirs on         Distribution and Biology: Science v. 229, no.
            the lower part of the continental slope north         4715, 1985, p. 713-717.
            of the Sigsbee Escarpment are of considerable
            long-range economic interest because of               Griggs, D. and Webster, F., Pacific in United
            potential petroleum development. The uplift of        States Outer Continental Shelf Basins - Maps
            the diapirs in the Gulf is raising up the lower       and Descriptions: U.S. Department of the
            slope, and at the same time the salt wedge is         Interior, Minerals Management Service, OCS
            apparently encroaching on the deep ocean basin        Report MMS 86-0048, 1986, p. 26.
            sediments, thus expanding the continental             Hill, G. and Lockwood, M., Seafloor Exploration
            margin.                                               and Characterization - Prerequisite to Ocean
            The uplift of the Mendocino Ridge has extended        Space Utilization:      OCEANS 187 Conference
            the continental margin more than 60 nautical          Proceedings, Marine     Technology Society/IEEE,
            miles westward near Cape Mendocino.,           New    Halifax, 1987.
            canyons are forming on the back side of the           Matula, S.P., Using     Exclusive Economic Zone
            block forming the Mendocino Ridge.           Those    Digital Swath Data to Select Effective
            canyons which head near shore, such as Delgada        Bathymetry: OCEANS 186 Conference Proceedings,
            Canyon, are able to intercept the longshore
            sediment movement and they tend to be wider,          Marxne Technology Society/IEEE, Washington,
            with U-shaped valleys and gently sloping              1986, p. 136-140.
            floors.                                               McClain, K.J., Peper, J.S. and Holmes, M.L.
            The uplift of a series of linear ridges on the        Single Channel Seismic Reflection Records of
            lower slope off the Oregon-Washington coast is        Western Washington Margin and Cascadia Basin,
            expanding the lower slope westward. . It is           in Kulm, L.D. and others (eds.), Western North
            postulated that the uplift of those ridges, as,       American Continental Margin and Adjacent Sea
                                                                  Floor off Oregon and Washington: Atlas 1, Ocean
            well as the Mendocino Ridge, results from             Margin Drilling Program, Regional Atlas Series:
            tensional forces acting normal to the major           Marine Science International, 1984, Sheet 26.
            trend of the features, at the same time that
            there is uplift from within the earth. It also        National Ocean Service Plan for Mappi      ng the
            is postulated that the uplift is associated
            with earth expansion.                                 Seafloor of the United States Exclusive
                                                                  Economic Zone, 1988-92: National Oceanic and
                            REFERENCES                            Atmospheric Administration, U.S. Department of
                                                                  Commerce, 1987, 51 p.
            Amery, G.B., Structure of the Sigsbee Scarp,          Owen, H.G., Continental Displacement and
            Gulf of Mexico: American Association of               Expansion of the Earth During the Mesozoic and
            Petroleum Geologists Bulletin, v. 53, no. 12,         Cenozoic: Philosophical Transactions of the
            1969, p. 2480-2482.                                   Royal Society of London, v. 281, no. 1303,
            Benioff, H., Seismic Evidence for Crustal             1976, p. 223-291.
            Structure and Tectonic Activity: Geological           Perry, R.B., Scientific and Hydrographic Use of
            Society of America Special Paper 62                   the Bathymetric Swath Survey System: OCEANS '82
            (Poldervaart, A. ed.), 1955, p. 61-74.                Conference Proceedings, Marine Technology
            Brooks, J.M., Kennicutt, M.C. II, Bidigare,.          Society/IEEE, Washington, 1982, p. 396-401.
            R.R., and Fay, R.A., Hydrates, Oil Seepage, and
            Chemosynthetic Ecosystems on the Gulf of Mexico       Perry, R.B., Mapping the Exclusive Economic
            Slope: Eos, v. 66, no. 10, 1985, p. 106.              Zone: OCEANS 185 Conference Proceedings, Marine
                                                                  Technology Society/IEEE, Washington, p. 1193-
            Carey, S.W., The Expanding Earth: Developments        1197.
            in Tectonics 10, Elsevier, Amsterdam, 1976, 488       Pryor, D.E., Overview of NOAA's Exclusive
            P.                                                    Economic Zone Survey Program: OCEANS '85
            EEZ-SCAN 84 Scientific Staff, Atlas of the            Conference Proceedings, Marine Technology
            Exclusive Economic Zone, Western Conterminous         Society/IEEE, Washington, 1985, p. 1186-1189.
            United States:       U.S. Geological Survey
            Miscellaneous Investigations Series 1-1792,           Sweet, W., Gulf of Mexico in United States
            1986, 152 p.                                          Outer Continental Shelf Basins - Maps and
                                                                  Descriptions: U.S. Department of the Interior,
            EEZ-SCAN 85 Scientific Staff, Atlas of the U.S.       Minerals Management Service, OCS Report MMS 86-
            Exclusive Economic Zone, Gulf of Mexico: U.S.         0048, 1986, p. 11-18.

                                                              371

                                              MODIFICATIONS AND IMPROVEMENTS TO THE SEA BEAM SYSTEM
                                                                  ON BOARD RIV THOMAS WASHINGTON

                                                                         C. de Moustier, T. Hylas and J.C. Phillips

                                                                            Scripps Institution of Oceanography
                                                                            Shipboard Computer Group, A-023
                                                                                 La Jolla, California 92093

                                                ABSTRACT                                          During this time, the engineers and the technicians of SIO's Ship-
                                                                                                  board Computer Group (SCO), who operate and maintain the system,
                          A Sea Beam multibeam bathymetric survey system has been 1       ,n      began to modify some of the components of the system to improve
                     operation on board the R/V T. Washington of the Scripps Institution          reliability and performance as well as to facilitate the maintenance
                     of Oceanography since December 1981. In response to operational              tasks. In the last four years, the improvements to the operation and
                     requirements, the engineers of the Shipboard Computer Group at               maintenance of the Sea Beam system have been tied to an upgrade of
                     Scripps have implemented a number of modifications to the system's           the shipboard computer from an IBM 1800 to a DEC VAX- 11/730
                     Narrow Beam Echo-Sounder and to its Echo Processor. These                    system, henceforth referred to as VAX.
                     include the design and construction of a digital pitch compensator,               In the following we discuss the design philosophy adopted for
                     the ability to use a variety of sensors for vertical reference, the          logging the bathymetric data output by the Sea Beam system on the
                     design and constniction of hardware test equipment, of an interface          VAX, and its implications for expansion with new hardware or addi-
                     to the shipboard DEC VAX-I1n30 computer for data logging and                 tional interfaces. We then describe the implementation of the new
                     for automation of start-up procedures as weU as for performance
                     monitoring. Some of the modifications have prompted the manufac-                                              TERh
                                                                                                                                    EN
                                                                                          to
                     turer of the Sea Beam system, General Instrument Corporation,
                     upgrade the system they have delivered in the past 4 years to match              R   ROLL                                  ECLIPSE
                     the con-esponding improvements implemented at Scripps and which                                S/D                                                0
                     could prove useful to Sea Beam operations on other ships.                                   CONVERTER                                CONTOURS     U)
                                                                                                                                                                       (A
                                                                                                                                             ---- RT6--V'              U.1
                                                                                                                                                                       0
                                                                                                                                              CONVEFITER               0
                                                                                                                          CONT                                         M
                                                                                                                                  &                                    CIL.
                                            I INTRODUCTION                                                          KEY     TIMI                 ECHO                  0
                                                                                                                                              PROCESSOR
                                                                                                                                             RECEIVERS (16)
                          A Sea Beam bathymetric survey system, manufactured by the                                                      KEY
                     General Instrument Corporation (GIC), was installed on board
                                                                                                                                                             SWATH
                     R/V T. Washington of the Scripps Institution of Oceanography                   HEADIN              T
                                                                                                     GYRO             F  E                                   PLOTTER
                                                                                                                                            E
                     (SIO) in the fall of 1981. This system is a multibeam echo-sounder
                     designed to measure depth on 16 discrrte beams, with 2 2/30 angular
                     resolution, and produce a swath of contours along the ship's track. it                 DIGITAL              VERTICAL,     BEAM LINE       TEST
                                                                                                             PITCH      ITCH   PO , STBD        DRI           SIGNAL
                     consists of two main components: a narrow beam echo-sounder and                      COMPENSATOR          RE VERS            (16)       GENERATOR
                     an echo processor (Fig. 1). The echo-sounder consists of two huu-                                                                                 cc
                     mounted transducer arrays, installed at right angle to each other in a                 POWER              MECHANICA                               LU
                                                                                                           AMPLIFIER             POLL                                  0
                     T configuration, their associated signal generator, pitch androll com-                                                                            Z
                                                                                                        1      (20)          C                BEAMFORMING
                     pensators, timing unit, power amplifiers, preamplifiers, and beam-                                                          MATRIX
                     forming network. The echo-processor utilizes a Data General                                            RO    ROLL           (4 X 40)
                     Eclipse S- 130 real-time computer for the digitization of the echo sig-                                     SERVO                                 0
                     nals received and detected on each beam, for bottom detection and                                                        PREAMPLIFIERS
                     tracking, for geometric correction (roll and refraction), and for com-                                                       (40)
                     puting depths and horizontal distances to be displayed as an instan-                                                                              W
                     taneous depth profile or contoured and output to a swath plotter.
                     More extensive descriptions of the Sea Beam system and its opera-                                                                                 0
                                                                                                                                                                       cc
                     tion are found inRenard and Allenou [11, Farr [2] and de Moustier
                     and Kleinrock [3].                                                                                                                                Z
                          Following acceptance tests and sea trials in December of 1981                                    1>
                     aboard the R/V T. Washington, the system has been in operation an
                     average of 180 days per year over the past seven years, with rela-           Figure 1. Block diagram of the Sea Beam system with its two main
                     tively Ettle down time due to system failure. Several failures of the        sub-systems: a Narrow Beam Eacho Sounder and an Echo Processor.
                     pitch compensation unit occun-ed in, the first two years of operation.       Elements in the shaded areas are peripherals and external sensors.

                                                                       CH2585-8/88/0000- 372        $1 @1988 IEEE

                    components designed by SCG which include a digital pitch compen-                                                        VAX
                    sator, a sound source synchronizer and test equipment for system
                    calibration. Finally, we discuss the modifications that have
                    improved the reliability of the system and facilitated the operator's
                    tasks such as an automated parameter initialization procedure and                                                      GPlB
                    enhanced output capabilities, the ability to use various vertical refer-
                    ence sensors, and a capability to record the acoustic waveforms
                    received on each of the 16 preformed beams.
                                                                                                                        STD
                                II DATA LOGGING AND PROCESSING                                                          BUS

                                                                                                                      34                 SPEED
                         During each transmission cycle, the Echo Processor in the Sea                          WORDS                                          SPEED
                    Beam system computes depths and cross-track distances from the                                                                               LOG
                    sealloor echoes received on each of the 16 preformed beams. These
                    data are displayed on an oscilloscope as an instantaneous depth
                    profile across track, as well as on a swath plotter as a contour chart.              Figure 2. Data flow from Sea Beam to the VAX via the STD-GPIB;
                    In addition the data are sent to a data logging system. In this section,             buses.
                    we describe the current hardware which conveys the data from the
                    Echo Processor to the Data Logger aboard the RIV T. Washington.                      Beam's Echo-Processor sends 34 words (i.e. up to 16 depths and 16
                                                                                                         horizontal distances as well as time in minutes within the hour) and
                    Sea Beam to VAX Interface via STD-GPIB Bus                                           ships heading in a bit parallel, word serial format. That is, a 16 bit
                         The data logging option sold by GIC only consists of two mag-                   word is transmitted in parallel and all 34 words are transmitted seri-
                    netic tape drives. An additional computer is required to merge the                   ally. Three handshake signals associated with the Data Logger output
                    bathymetric data output by the Sea Beam system with the ship's                       board ensure the proper synchronization of the data to the Sea Beam
                    navigation data in order to produce a contour map in geographic                      STD Interface board.
                    coordinates. As the R/V T. Washington was already equipped with                            Another function of the Sea Beam STD interface is to output
                    an IBM 1800 real-time computer configured to log and process the                     the ship's speed to Sea Beam. This is done by sending a digital
                    ship's navigation and underway geophysical data (i.e. magnetics,                     representation of the ship's speed to the STD bus from the VAX via
                    gravity), SIO opted to use this computer to log and process Sea                      GPIB. This information is then changed into the proper analog vol-
                    Beam data as well. In February 1984, the IBM 1900 was replaced by                    tage by a digital-to-analog converter and sent to Sea Beam for use in
                    a DEC VAX- I In30 computer system [4].                                               the real time swath chart record. The rest of the hardware on this
                         The front end of the VAX system has microprocessor con-                         interface is used for address decoding and timing needed for com-
                    trolled input/output devices utilizing the IEEE 961 Standard (STD)                   munication with the Z80 microprocessor.
                    bus protocol in conjunction with an IEEE 488 General Purpose Inter-                                             III NEW DESIGNS
                    face Bus (GPIB) bus controller (Fig. 2). The STI) bus is an 8 bit
                    data bus controlled by a Z80 microprocessor. Data from a variety of
                    sources are transferred over this bus in an 8-bit parallel format under                    The Z80 microprocessor architecture described in Section II
                    control of the microprocessor and stored in local memory until inter-                has been used in the design of two new components discussed in this
                    rogated by a GPIB controller in the VAX. The controller subse-                       section: a pitch compensator and multiple sound source synchron-
                    quently sends these data to disk storage through a separate STI) to                  izer. Retaining the same microprocessor architecture had the advan-
                    GPIB interface. In this manner the VAX is free to perform higher                     tage of simplifying maintenance, as spare parts would be inter-
                    priority tasks before polling the individual STD bus devices for their               changeable between the various data acquisition systems and the
                    data [4], [5].                                                                       new components, and of capitalizing on the programming expertise
                         The choice of the STD bus architecture to route Sea Beam data                   already acquired for the Z80 microprocessor.
                    to the VAX was prompted by a larger real-time data acquisition
                    scheme involving several other underway geophysical measurements                     A Microprocessor Controlled Pitch Compensator
                    (e.g. gravity, magnetics, single channel seismics) as well as the                          The transmitter array of the Sea Beam system consists of 20
                    ship's navigation (e.g. Loran C, Transit Satellites, dual-axis Doppler               projectors mounted along the ship's keel. The array is electronically
                    speed log) [6]. This architecture has the advantage of providing a                   steered to compensate for the pitching of the ship. To accomplish
                    versatile instrument interface and data buffering system independent                 this, a pitch compensator alters the phase of the input signal fed to
                    of the main computer [4]. li also allows the addition of new sensors                 each projector relative to the center of the array, projector #10. This
                    without affecting the performance of the main computer, and the                      method ensures that the maximum response axis of the transmitted
                    choice of sensors is not limited to those which have internal data                   radiation pattern remains aligned with true vertical.
                    buffering capability. By comparison, computers installed by the                           The system originally installed on the R/V T. Washington used
                    NECOR group in support of Sea Beam operations, and tasked only                       a mechanical pitch compensator in which a synchro signal represent-
                    with acquisition and processing of Sea Beam data and the ship's                      ing the ship's pitch angle was fed to a control transformer driving a
                    navigation data, rely on sensors providing a serial RS-232C output                   servo motor in a one speed closed servo loop. The servo motor was
                    [7). The Sea Beam STD interfa       cc uses line receivers and differen-             mechanically coupled to a gear train which was connected to 20
                    tial drivers on its data lines to ensure a high immunity to noise for                resolvers. Each resolver was geared so that when a pitch synchro
                    the data flow. The data flow between Sea Beam and the Data Logger                    signal was input, the resolver turned accordingly and output the
                    is illustrated in Figure 2.                                                          proper phase adjusted signal to each o          'f the twenty projectors.
                                                                                                         According to GIC, very few problems had been reported on similar
                                                                                                                                                                STD
                                                                                                                                                                BUS

                                                                                                                      34
                                                                                                                       S
                                                                                                                 JORD

                         Every transmission cycle, the Data Logger output board in Sea                   units installed in other ships equipped with a Sea Beam system or

                                                                                                  373

                     only with a narrow beam echo-sounder. However, many hours of                           Each counter is loaded by it's own LOAD command from the
                     maintenance and down time were incurred because of failure of the                software to an initial count value. A 3.112448 MHz clock signal is
                     pitch compensator on the R/V T. Washington. The gear train con-                  then gated on by a Modified Sonar Key (MSK) and they commence
                     nected to each resolver would easily slip and bind causing failure of            counting. The Modified Sonar Key is a signal created in software
                     the compensator or, far worse, subtle inaccuracies of the output sig-            which limits the length of the pulse sent to the transmitter to 7ms to
                     nals. In addition, the device's small physical dimensions (12x3x4                prevent damage to the transmitter power amplifiers. The counters
                     inches) made it difficult to repair or adjust, particularly in a sea-            are wired as divide by eight so that by using the high order bit on
                     going environment. For this reason SCG decided to design and build               each counter, a 12,158 Hz output is obtained. The resulting square
                     a digital pitch compensator that would perform the same task                     wave is then gated with MSK and the signals at the output of the
                     without the problems associated with a mechanical design.                        counter boards are passed to the filter board. The filter board is
                          The design had to meet the same input-output criteria as the                comprised of 20 switched capacitor filters which were selected for
                     mechanical compensator did. To accomplish this we use an elec-                   their stability and accuracy. The filters change the 12,158 Hz square
                     tronically controlled system based on a Z80 microprocessor and the               wave output by the counter boards into a 4.5v p-p sine wave. This is
                     STD bus. As shown in Figure 3, the resulting design requires six cir-            d .one to remain compatible with the original system which requires a
                     cuit boards:                                                                     sine wave input to the transmitter shaper amplifiers. These
                     (1) a Central Processor Unit board which contains the Z80 micropro-              amplifiers then output a signal to the transmitter power amplifiers,
                     cessor and associated hardware used to control the operation of the              which send a 7ms burst of 12,158 Hz energy to the projectors.
                     system. It also contains memory devices for permanent and tem-                         This digital pitch compensator was first tested on the R/V T.
                     porary storage of inforniation.                                                  Washington in 1984, and became an integral part of the system in
                     (2) a Syncliro to Digital Converter board which converts the pitch               August 1985, greatly improving the Sea Beam system's reliability
                     signal supplied by the vertical reference (Fig. 1) from synchro to               and decreasing system down time. The simple replacement of STD
                     digital format. This information is then used by the processor to out-           bus modules in the compensator has also decreased repair time on
                     put angle and counter delay values.                                              the system. In parallel with SCG's efforts, GIC also developed a
                     (3) a Display board which outputs pitch angle obtained from the pro-             digital pitch compensator to replace the mechanical unit. All the Sea
                     cessor to a LED display on the front panel of the compensator                    Beam systems delivered by GIC since 1985 are equipped with a digi-
                     drawer.                                                                          tal pitch compensator.
                     (4, 5) two counter boards accepting delay values from the processor
                     as input to 20 counter circuits which output a 12,158 Hz square wave             Multiple Sound Source Synchronizer
                     for each of the 20 projectors. One counter board contains counters                     During geophysical surveys carried out with the R/V T. Wash-
                     for channels 1-10 the other contains counters for channels 11-20. In             ington, a 3.5 kHz subbottorn profiler, a one or two channel seismic
                     addition one of the counter boards has the necessary circuitry                   profiler and the Sea Beam system are often operated simultaneously.
                     required to synthesize a 12,158 Hz square wave.                                  This creates conflicting transmit-receive sequences and these sys-
                     And (6), a filter board which changes the square waves output by the             tems interfere with each other. The Sea Beam system is affected the
                     20 counters to sine waves required to drive the transmitter shaper               most by such interferences as its bottom tracking algorithm may lock
                     amplifiers.                                                                      on an interfering signal for a series of transmit cycles and generate
                           The system is run by software installed in permanent memory                erroneous bathymetry or artifacts in the contours which could be
                     on the CPU board. This software is. divided into three sections: a               mistaken for a bottom feature [3]. Experience has shown that opera-
                     control program, a counter delay table and an angle display table.               tor intervention to avoid interference, by slewing sound sources
                     The function of the software is to wait for a sonar key from Sea                 away from each other, usually happens after the fact. Moreover,
                     Beam's timing logic and, upon receipt, read the pitch angle informa-             over rough terTain the task becomes rather demanding when more
                     tion from the synchro-to-digital (S/D) converter. This angle is then             than two sound sources are involved. When the Sea Beam system is
                     used to index a lookup table containing the appropriate phase delays             operated in conjunction with the 3.5 kHz subbottom profiler,
                     to be loaded into each of the 20 counters on the counter boards. The             interferences between the two systems can be avoided by simply gat-
                     software also uses a lookup table containing angle values to output a            ing out the 3.5 kHz transmission during a Sea Beam reception win-
                     pitch angle to a LED display.                                                    'dow. Such a solution only requires a very simple circuit, however it
                                                            PITCH
                                                           ANGLE                                      SEA BEAM                                               612158 Hz
                                       PITCH              DISPLAY                                       SONAR                                                SINE WAVE
                                     SYNCHRO                                                              KEY                                                TO
                                       INPUT                                                                                                                 TRANSMITTER
                                                                                                                                SQUARE WAVE INPI-1
                                                                                                                        12158 Hz                  JT         SHAPER
                                                                                                                                                             AMPS

                                                                                                        COUNTER              COUNTER                 FILTER
                                    SYNCHRO                                         Z80                  CARD                   CARD                  CARD
                                         TO               DISPLAY                   CPU                      1                     2
                                      DIGITAL                                                           Channel               Channel               Channel
                                                                                                          1-10                  11-20                 1  -20
                                                                                    A&
                                                                                                                        1
                                                                                                                        21W    z
                                                                                                                        7                                    AM
                                                                                                                 @R           C1
                                                                                                            JNTE                                 [LFILTER
                                                                                                                                                      CARD

                                                                                       STD BUS

                                                                    Figure 3. Architecture of SIO's digital pitch compensator.

                                                                                                 374

                  is inadequate whenever a third sound source is also operated simul-             to facil itate the calibration of the transmitter power amplifiers and to
                  taneously.                                                                      measure the response of the Echo Processor receivers.
                        To deal with this problem, SCG designed and built a multiple                    To calibrate the transmitter power amplifiers, the most vital
                  sound source synchronization box, also know as "Synch Box", which               piece of test equipment is a digital storage oscilloscope (DSO) with a
                  schedules the firing rates of the three sound sources according to              built-in GPIB interface. A DSO is necessary to be able to verify the
                  selectable priority assignments and to timing parameters computed               shape of the 7 ms CW transmit pulse as well as to measure the phase
                  by a Fortran program running on the VAX. As this system is                      difference between the outgoing voltage and the return current in
                  described in detail by Phillips et al [81, only a brief overview of its         each power amplifier. Taking advantage of the DSO's ability to
                  components is given here.                                                       digitize, save a waveform and transfer it to a host computer, SCG
                        The hardware of the Synch Box uses the same Z80 micropro-                 developed a simple procedure to perform the calibration. The square
                  cessor and STD bus system described above, and it consists of three             wave output of each power amplifier is run through a 12 kHz
                  circuit boards (Fig. 4). (1) a CPU board containing the Z80                     bandpass filter box built in house and digitized with the DSO. These
                  microprocessor, EPROM firmware for the application program and                  data are then sent to the VAX through the GPIB/STD interfaces for
                  RAM memory for system management functions, as well as an                       analysis. Currently, the values of the 20 projector channels are
                  upgraded 4 MHz crystal oscillator with an accuracy of 5 parts per               entered into a Fortran program which calculates the output power
                  million. (2) an input-output board which orchestrates the events                corresponding to the measurement, and each channel is determined
                  associated with each sound source under control of the firmware.                to be either in or out of specifications and adjusted accordingly. We
                  And (3) a display interface board which displays the most current               intend to remove the filter box from this operation and use digital
                  center beam depth measured by the Sea Beam system on a 5-digit                  filtering programs on the VAX to perforin the same function. This
                  LED readout as well as transmit events for each of the sound sources            procedure proved far more reliable and accurate than one       'based on
                  on individual LED's. A continuous two-way communication takes                   visual readings from an analog or non-storage oscilloscope.
                  places between the Synch Box and the VAX acting as a host. The                        SCG also built an echo delay generator to perform the neces-
                  firmware checks the status of the various sound source systems and              sary tests on the Echo Processor receivers. This device contains a
                  relays the information to the scheduling algorithm running on the               12,158 Hz oscillator, matching the transmit frequency of the Sea
                  VAX. It also controls the triggering of source and graphic recorder             Beam system, and presetable counters and amplifiers. After ter-
                  events by loading counters with the appropriate delay parameters                minating the hydrophone inputs with a resistor network, the delays
                  calculated by the scheduling algorithm and passed by the VAX.                   and amplitudes specified by the manufacturer are set in the device,
                        This system has been operational on the R/V T. Washington                 and the response of each receiver is checked for accuracy following
                  since the winter of 1987. When all three sound sources are in opera-            the procedure recommended by GIC. This device has greatly
                  tion, the seismic system, having the most rigid firing rate require-            simplified the method of insuring accurate response of the Echo Pro-
                  ments, is given first priority, the Sea Beam system comes next and              cessor receivers.
                  the 3.5 kHz subbottorn profiler is last. Once the initial parameters                                   IV MODHICATIONS
                  have been loaded and the scheduling program started, the Synch Box
                  operation requires no further operator intervention.                                       modifications described in this section have been imple-
                                                                                                  mented to (1) facilitate the task of the operator and reduce the poten-
                                                                                                  tial for error by streamlining the Sea Beam start-up procedure, and
                                                 VAX                                              by expanding the output capabilities of the system; (2) improve the
                                                                                                  system's reliability by being able to switch one of three vertical
                                                                                                  reference sensor online, and by alleviating a problem affecting the
                                                     RS-232C                                      accuracy of the ship's roll information received by the Echo-
                            r--------------- ----------------                                     Processor, and (3) give access to the acoustic signals at the output of
                                                                                                  the beamformer to allow their recorftg for further analysis.
                                                 Z80
                                                 CPU               CENTER BEAM                    Downloading of Sea Beam Initialization Parameters
                                                                     DEPTH(M)
                                 STD                                                                    The operator's console provided by GIC to communicate with
                                 BUS           DISPLAY             0                              the Eclipse computer in Sea Beam is a DECwriter printing terminal,
                                                                                                  serving both as keyboard for parameter entry and as printer for out-
                                                  1/0                                             put of system messages by the Eclipse computer. On the RIV T.
                                                                                                  Washington, this console has been replaced by a direct RS-232C
                                                                                                  connection to the VAX. Console messages sent by the Eclipse com-
                            -------------                ------- -----------                      puter are now saved in a log file on the VAX and echoed on a Gra-
                                                   3*5 kHz SEISMICS                               phOn CRT terminal with an attached Okidata printer for optional
                                                                                                  hard-copy output. A switch-box was added to allow this terminal to
                                          SEA BEAM                                                be used with either the Sea Beam Eclipse processor or the VAX host
                                                                                                  computer and serve as a laboratory checkpoint to monitor the status
                  Figure 4. Architecture of SIO's multiple sound source synchronizer.             of a variety of equipment.
                                                                                                        With this setup and a UNIX* C-shell script, it was relatively
                  Test Equipment                                                                  simple to automate the procedure required to initialize the Sea Beam
                        To ensure   the continued optimum performance of the Sea                  system by downloading a parameter file from the VAX to the Eclipse
                  Beam system, a    regular maintenance schedule must be observed                 computer. The parameters in this file include the Leg number, the
                  requiring test procedures and measurement equipment. In general:                date, the time of day, the ship's draft and a sound velocity profile
                  SCO's engineers use the test procedures recommended by GIC, how-                consisting-of up to 10 pairs of depth and sound velocity. With the
                  ever specific test equipment and procedures were developed in-house             UMX is a trade mark of AT&T Bell Labs.

                                                                                             375

                     DECwriter terminal these parameters had to be entered sequentially                of failure or malfunction of the data logger, an archive copy is kept
                     at the keyboard, and typing errors meant having to start the sequence             on microfilm. For this reason, a second Complot DP-1 plotter was
                     from the top. This fact becomes noteworthy when it is realized that               connected in parallel to produce a continuous duplicate copy of the
                     the procedure must be followed not only when the system is first                  swath output, thereby granting the investigator unlimited shredding
                     turned on or rebooted after a crash, but every time a new sound velo-             privileges on the working copy.
                     city profile must be entered to account for changing oceanographic                      As mentioned above, plotting of the contoured Sea Beam data
                     conditions, as well as every few days to reset the Sea Beam clock                 in a geographic reference frame requires that these data be merged
                     which is known to drift about 20 seconds per day.                                 with the ship's navigation. On the R/V T. Washington, this opera-
                           Once the parameter file in the VAX has been satisfactorily                  tion is performed by the VAX computer, and the data are plotted on
                     edited, the automated initialization method requires minimal user                 one of the two CalCornp 965A belt-bed plotters linked with the com-
                     input, and the dialogue between the VAX and the Eclipse computers                 puter. There is no direct connection between the Sea Beam system
                     is displayed on the terminal and the printer for verification. With the           and these plotters. During Sea Beam operations, one of the plotters
                     terminal switch in the "Sea Beam" position the operator executes the              is dedicated to plotting, with a few minutes delay, a swath of seafloor
                     start-up program for the Echo Processor: 'COMM'. Switching the                    contours along the ship's track in a geographic reference frame.
                     tenninal back to "VAX", the operator then executes the UNIX C-                    Parameters such as chart scale and contour interval are user select-
                     shell script 'RUN.loadsb' which sends the intialization parameters to             able. The other plotter is used for Sea Beam chart making in the
                     the Eclipse computer. A shorter C-shell script 'RUNsvp.time' is                   post-processing phase. This involves editing and processing the
                     used whenever it is only necessary to change the time or the sound                ship's navigation and remerging it with the Sea Beam data. Further
                     velocity profile [9].                                                             information on the real-time and post-processing tasks associated
                           This automated procedure has been a great improvement by                    with Sea Beam is found in Moore et al, [61 and Charters [101. Also
                     reducing the potential for operator error as well as the time required            note that a similar plotting arrangement is used in the NECOR Sea
                     to change parameters during a survey hence minimizing data loss.                  Beam operation [7).
                     Output Enhancements                                                               Vertical Reference System
                           The Sea Beam system comes with a limited array of output                          Because the acoustic arrays of the Sea Beam system are
                     devices and supporting features. Although it has the required driving             mounted in a fixed position on the ship's hull, the system needs an
                     circuitry to support 2 graphic recorders, I step-driven swath plotter,            accurate vertical reference to compensate for the roll and pitch
                     I analog storage oscilloscope, and 2 LED displays for depth read-                 motions of the ship. As mentioned in Section III, pitch compensa-
                     outs; only the storage scope and one LED display are standard equip-              tion ensures that each of the 20 projector output pulses are properly
                     ment. The remaining devices must be purchased as optional equip-                  phase shifted with respect to the center of the array, to align the max-
                     ment. On the R/V T. Washington, the output devices added in sup-                  imurn response axis of the transmitted acoustic radiation pattern with
                     port of Sea Beam operations include a graphic recorder, two swath                 vertical. Likewise, the seafloor echoes received at the hydrophone
                     plotters and two belt-bed plotters.                                               array must be corrected for the ship's roll so that (1) the Narrow
                           The current graphic recorder is an EPC Labs model 3211 with                 Beam Echo Sounder portion of the system can output the proper
                     32 kilobytes of built-in memory. This graphic recorder is used to                 beams to the port, starboard, and vertical receivers and (2) the Echo
                     display the acoustic return received either on the vertical beam, or on           Processor computer can compute the correct depth and cross track
                     a selected port or starboard beam, or for one of the combinations of              distance for each beam.
                     all port beams, all starboard beams or all beams port and starboard.                    The Sea Beam system's specifications call for a vertical refer-
                     If a second graphic recorder were added it would be limited to the                ence which outputs. pitch and roll information in a synchro format
                     vertical beam display only.                                                       with  an accuracy of one tenth of one degree. Aboard the R/V T.
                           The memory feature of the graphic recorder plays an important               Washington, one of three sensors can be selected for this task: (1) a
                     role in the implementation of the Synch Box described in Section III,             vertical reference gyroscope (Kearfott-Singer) which was purchased
                     as it allows keying at non-specific times [8). During Sync Box                    with the Sea Beam system to serve as its source of vertical reference,
                     operations the graphic recorder is configured for use with an external            (2) the gimbaled table of an Anschutz gravimeter and (3) the vertical
                     record trigger. When Sea Beam is the only sound source in use, the                reference unit of a Bell Aerospace BGM-3 gravimeter. A sensor is
                     recorder is set to its internal trigger mode and the EPC edge pulse is            selected by connecting the appropriate jumpers in a gyro junction
                     used for Sea Beam keying. Both the 3.5 kHz subbottom proffier and                 box.
                     the single channel seismic system use the same model of graphic                         The Kearfott-Singer gyroscope is the most "sea-worthy" verti-
                     recorders so that plenty of replacements and spares are available.                cal reference because it is not as adversely affected by rapid 180
                           The Sea Beam system delivered to SIO in 1981 included one                   course changes or rough sea-states (>4) as the gravimeter references.
                     Houston Instrument Complot DP- I plotter to display a near real-time              It contains all the necessary electronics to provide the proper synchro,
                     swath of contoured Sea Beam data. This swath display includes the                 output to the system. It requires 115v-400 Hz for its operation and it
                     bottom contours, time, course, and contour interval. In addition, the             has internal transformers which provide the necessary step down to
                     rate of advance of the paper is a function of the ship's speed supplied           26v-400 Hz needed by the system for reference. Its only significant
                     to the Eclipse computer as described in Section II. This display is a             drawback is its limited mean-time between repairs: one year of con-
                     very useful tool during the conduct of a survey as it provides the                stant use, after which the gyroscope's rotor bearings must be
                     investigator with near real-time seafloor based navigation while fol-             overhauled at the factory at a cost of $50,000, with delivery times
                     lowing geological features of interest or positioning the ship prior to           exceeding 6 months. For this reason this gyroscope is now only used
                     instrument and vehicle deployments as well as for coring and dredg-               as a back-up unit and in rough sea states. We do not plan to have
                     ing operations. However, because this display does not contain any                this unit repaired the next time it fails.
                     geographic information, to follow seafloor features often requires                      As a substitute source of vertical reference, we used the gyrot-
                     cutting and reorienting the strip of paper to match the current ship's            able of an Anschutz gravimeter which was already installed on the
                     heading. As this swath plot. would be the only data available in case             R/V T. Washington. The gyrotable had two synchro devices giving

                                                                                                   376

                  pitch and roll information, so we only had to provide these synchros            three high power operational amplifiers, one amplifier for each wind-
                  with the proper rotor input signals and the Sea Beam system with a              ing SI, S2, and S3. The amplifiers are wired as voltage followers so
                  26v 400 Hz reference from an external transformer. This system                  that the input voltage is equal to the output voltage and is in phase
                  worked well for several years but the need for frequent manual fine             for each respe ctive winding. Sufficient voltage sources (+,-.24Vdc)
                  leveling of the gyrotable and constant maintenance due to its 20                are provided to insure linearity over the entire input range, apprDxi-
                  years of age as well as the gyro's inability to re-erect itself quickly         mately 22Vp-p. Output filter capacitors are also included to prevent
                  after drastic course changes were severe drawbacks. In February of              spurious noise from affecting signal accuracy.
                  1987, the gravimeter system was replaced by a Bell Aerospace                          This modification has proved very effective in assuring the
                  BGM-3 unit; however the gyrotable portion of           *the system still        accuracy of the input roll signal and the ease of switching between
                  remains on board as an emergency vertical reference source.                     any of our vertical reference sources.
                        The new gravimeter currently provides our primary source of               Acoustic Data Acquisition
                  vertical reference for Sea Beam. It is mounted in a small case on
                  free moving gimbals aligned to true vertical by two independent                       The ability to make, for every transmission cycles, 16 discrete
                  gyroscopes, one for roll and one for pitch. The gravimeter was                  acoustic measurements with an angular resolution of roughly 2 2/3*
                  delivered with two resolvers mounted on the case to sense gimbal                within an angular sector of about 40' centered on the ship's vertical
                  position. We built an interface to convert the output of these                  axis is the basis for the distinct advantage of a multibearn echo-
                  resolvers into the required synchro signals, and to provide the rotor           sounder such as Sea Beam over a single point depth sounder,
                  input signal for the resolvers and a 26v4OO Hz reference signal for             whether wide or narrow beam. Such simultaneous acoustic measure-
                  Sea Beam. At present this scheme is working well but the gyro dev-              ments contain much more information than is necessary for bathy-
                  ices used in the BGM-3 gravimeter also have a mean time between                 metry. However, there is no internal provision in the Sea Beam sys-
                  repairs of about 18 months with delivery schedules of 9 months and              tem to preserve the acoustic information received, and the signals
                  cost in excess of $ 10,000.                                                     once processed for bathymetry are discarded. In 198 1, when the Sea
                        In order to meet the vertical reference requirements of the Sea           Beam system was installed on the R/V T. Washington, the Marine
                  Beam system at a substantially lower cost, we are in the process of             Physical Laboratory (MPL) at SIO explored ways to preserve this
                  installing a Datawell PIRO-120 sensor on the R/V T. Washington.                 acoustic information. A set of buffer amplifiers were built to tap the
                  The interface between this sensor and the Sea Beam system uses a                detected and rectified envelopes of the beamformed echo signals
                  Z80 microprocessor and technology similar to that described in Sec-             received on the 16 beams. These signals were sent differentially to a
                  tion III for other components of the Sea Beam system designed by                special purpose acoustic data acquisition system where they were
                  SCG.                                                                            digitized and recorded on magnetic tape for further processing [10].
                                                                                                        Acoustic data recorded with this system have proved invalu-
                  An Input Buffer Amplifier for the Mechanical Roll Compensator                   able to assess the performance of the Sea Beam system and to
                        The Narrow Beam Echo Sounder portion of the Sea Beam sys-                 explain the cause of artifacts that were sometimes found in the con-
                  tem contains a mechanical roll compensator. This device couples a               toured bathymetry output by the system [3]. The addition of buffer
                  specified beam or combination of beams from the 16 preformed out-               amplifiers at the output of the receivers in the Echo Processor also
                  puts of the beamformer to one or more of the pon, starboard and                 highlighted a 1 MHz noise endemic to the Echo Processor. This
                  vertical receivers for output to a graphic recorder and to a digitized          problem was successfully alleviated by adding capacitors to the
                  vertical beam depth display. A roll servo system, consisting of an              buffer amplifiers. Since then, GIC has released a Sea Beam applica-
                  input synchro, a servo amplifier and a servo motor in a closed servo            tion note advising the addition of a capacitor on the backplane of the
                  loop, takes roll synchro data from the vertical reference sensor. It            Echo Processor receivers. Duplicates of the buffer amplifier boards
                  rotates a shaft which moves the roll compensator plates to the correct          were also made at MPL and given to the NECOR Sea Beam group
                  position, thus coupling the proper beams to the receivers.                      who installed similar acoustic data acquisition capabilities on the
                        Due to the mechanical nature of the system, wear on the gear              R/V Conrad and Atlantis 11.
                  train and friction of binding of the compensator plates can cause a                   For seafloor acoustic backscattering investigations, the acoustic
                  non zero servo error which is coupled back through the control                  data recorded in this fashion proved only partly adequate as sidelobe
                  transformer and loads the input signal. This can cause gross errors in          interference inherent in the multibearn geometry affect the returns.
                  the roll angle data as, well as subtle errors which are difficult to            This situation is particularly damaging in the near-specular beams
                  detect. In addition, the roll input control transformer is highly induc-        were sidelobe interference and bottom return overlap. As only the
                  tive and has a low input impedance, resulting in a significant phase            envelope of the returns was recorded, there was no way to separate
                  shift (up to 20') between the reference and output windings depend-             sidelobe interference from bottom return; to do so requires that the
                  ing on the the vertical reference sensor used.                                  full waveform be available [ I 11.
                        This problem required careful attention because roll data are                   For this reason, in 1985, the MPL data acquisition system was
                  also used by the Eclipse computer to compensate for the ship's roll             redesigned to allow preservation of the amplitude and the phase of
                  while calculating depths and horizontal distances. Given that the               the echoes received. This is done by tapping the signals at the output
                  output synchros could not be changed, our first modification was to             of the beamformer, where they are still in audio form, and by base-
                  provide a phase shift (RC) network which matched the reference                  banding and quadrature sampling to obtain the in-phase (1) and qua-
                  phase to that of the output. Although functional, this method proved            drature (Q) components of these signals. The resulting 32 channels
                  impractical because of the need to reconfigure the input wiling                 (16 complex channels) are then digitized at approximately 1 kHz per
                  whenever a different vertical reference sensor was used, and subtle             channel, and recorded on magnetic tape. This complex acoustic data
                  roll errors could still happen if any loading occurred.                         acquisition scheme, described in greater detail by de Moustier and
                        A buffer amplifier circuit, installed between the roll angle input        Pavlicek [121, has been used successfully aboard the R/V's T.
                  and the roll compensator synchro, provided a better fix to the prob-            Washington, Atlantis 11 and the French Oceanographic Vessel Jean
                  lem. This prevents any synchro loading from affecting the input and             Charcot. Complex acoustic data derived from this system have also
                  allows us to use any of our vertical references without the need for            confirmed the fact that Adaptive Noise Cancelling technique were
                  any external phase shift network or rewiring. The circuit consists of           well suited to remove the sidelobe interference and give access to

                                                                                           317

                     seafloor acoustic backscatter measurements with the anticipated                                            V111 REFERENCES
                     angular resolution of roughly 2 2/3' [131.
                                                                                                      [1] Renard, V. and J. P.Allenou, Sea Beam multi-beam echo-sounding
                                              V CONCLUSIONS                                           in "Jean Charcot" Description, evaluation and first results
                          In spite of the problems encountered during the first two years             Intemational Hydrographic Review, LVI(l), pp. 35-67, 1979.
                     of operation of the Sea Beam system, which led to the modifications              [21 Farr, H. K., Muldbeam bathymetric sonar Sea Beam and
                     described in this paper, the system has proved very reliable. This fact          Hydrochart, Marine Geodesy, 4(2), pp. 77-93, 1980.
                     is a tribute to the designers of the system as most of the Narrow                [3] de Moustier, C. and M. C. Kleinrock, "Bathymetric artifacts in
                     Beam Echo Sounder sub-system delivered to SIO had remained                       Sea Beam data: how to recognize them, what causes them", J. Geophys.
                     unchanged since it first came out in the mid 1960's. The                         Res., Vol 91, No B3, pp. 3407-3424,1986.
                     modifications made to the system installed on the RIV T. Washing-                [4] Abbott J.L., S.M. Smith, J.S. Charters, P.G. Downes, T. Hylas,
                     ton have reduced the need for maintenance or repairs as well as facil-           R.L. Moe, J.M. Moore and D.V. Stuber, Scripps seagoing computer
                     itated the task of the operator. Although these modifications are                centers: real-time data acquisition and processing, IEEE Proc. 4th
                     specific to the SIO system, the automated parameter intialization, the           Working Symposium on Oceanographic Data Systems, pp. 123-129, 1986,
                     multiple sound source synchronization, the buffering of the roll input           [5] Charters J.S., SIO Sea Beam software documentation, Shipboard
                     and the improvements in calibration procedures can be adapted to                 Computer Group A-023, Scripps inst. of Oceanog., La Jolla CA 92093,
                     other Sea Beam installations that include a data logging computer.               unpublished document, 1986.
                          The modifications described in this paper remain relatively                 [61 Moore, J. M., J. S. Charters and C. de Mounier, Multi-sensor
                     benign as they were intended to improve the existing system rather               realtime data acquisition and preprocessing at sea, Proc. MTS-IEEE
                     than design a new one. By today's standards [14] the Sea Beam Sys-               Oceans'88 Conf., Baltimore Maryland, 1988.
                     tem will need to undergo more drastic changes to meet the needs of               [71 Tyce R.C., S. Ferguson and P. Lemmond, NECOR Sea Beam data
                     the oceanographic community for wider swath widths and finer                     collection and processing development, NITS Journ., Vol. 21 No. 2,
                     angular resolution. This will require modification of the acoustic               pp. 80-92,1987.
                     arrays and the use of digital beamforming techniques.                            [8] Phillips J.C., J.L. Abbott and C. de Moustier, Multiple sound
                                        VI ACKNOWLEDGEMENTS                                           source synchronizer for seafloor surveying, OTC #5867, Proc.
                          The development work reported in this paper has been funded                 Offshore Technology Conference, Houston Texas, 1988.
                     in part under the Accelerated Research Initiative on multibeam sys-              [91 Smith S.M., J.L. Abbott and J.C. Phillips, Scripps Sea Beam start
                     tems sponsored by the Office of Naval Research (ONR), Contract                   up procedure and downloading of terminal entry parameters, SIO
                     N00014-86-G-0142, N00014-85-G-0104 (SCG) and N00014-79-C-                        Geol. Data Center, Sea Beam Series No. 5. internal
                     0472 (MPL); and from SIO Institutional funds. The Sea Beam Sys-                  unpublished repoM 1987.
                     tem installed on the R/V T. Washington was purchased with an ONR                 [101 de Moustier, C., Sea Beam Acoustic Data Acquisition System,
                     grant, Contract N00014-80-C-0440, matched equally with trust funds               Technical Memorandum 379, Scripps Institution of Oceanography, San
                     from SIO. J. L. Abbott directed and was actively involved in the                 Diego, CA, 1985
                     development work done by the Shipboard Computer Group. Under                     [IlldeMoustier,C. "Beyond bathymetry: mapping acoustic
                     his guidance the main contributors to the hardware development                   backscattering from the deep seafloor with Sea Beam", J. Acoust.
                     were P. Downes, T. Hylas and D. Stuber for the STD data acquisition              Soc. Am., Vol 79, No 2, pp. 316-331, 1986.
                     system, P. Downes for the digital pitch compensator, J.C. Phillips, T.           [121 de Moustier C. and F.V. Pavlicek, A fully transportable Sea Beam
                     Hylas and D. Stuber for the Synch Box, and T. Hylas for all the other            complex acoustic data acquisition system, OTC #5514, Proc. Offshore
                     modifications to the Sea Beam system. The Sea Beam acoustic data                 Technology Conf., Houston Texas, pp. 269-274, 1987.
                     acquisition work done at MPL was initiated by R.C. Tyce and pur-                 [131 Alexandrou D. and C. de Moustier, Adaptive noise cancelling applied
                     sued by C. de Moustier and F.V. Pavlicek who have developed the                  to Sea Beam sidelobe interference rejection, IEEE J. of Oceanic
                     necessary hardware and software, with significant software contribu-             Eng., Vol. 13 No. 2, pp. 70-76,1988.
                     tions by R. M. Lawhead. We thank E. Ford for typing and format-                  [ 14] de Moustier C., State of the art in swath bathymetry survey
                     ting and J. Griffith for the art work.                                           systems, in Current Practices and New Technology in Ocean
                                                                                                      Engineering, G.K. Wolfe and P.Y. Chang Eds, ASME OED-Vol. 13,
                                                                                                      pp. 29-38,1988.

                                                                                               378

                                   THEORY AND TEST OF BATHYMETRIC SIDE SCAN SONAR

                                                   Donald E. Pryor

                                      Office of Charting and Geodetic Services
                                               National Ocean Service
                                   National Oceanic and Atmospheric Administration
                                              6001 Executive Boulevard
                                              Rockville, Maryland 20852

                              ABSTRACT                        corresponding to any point in the side-scan
                                                              image.-
            Bathymetric, or interferometric, side scan-
            sonars offer great improvement over
            conventional hydrographic and bathymetric             PHASEDIFFERENCE  DsInO
            techniques because their broad swath makes            BETWEEN RECEIVERS 2nA
            it possible to survey an area more                    D = ARRAY SEPARATION
            efficiently, their high spatial resolution            A= ACOUSTIC WAVELENGTH
            makes it less likely to miss an obstruction
            or feature, and their image output gives
            valuable information about the bottom
            composition. Accuracy and data processing
            improvements have appeared necessary before
            such systems are accepted for routine                        TRANSDUCER
            operational use. A theoretical model of                      ARRAYS
            the phase measurement errors which limit
            accuracy has been developed. Tests of a
            shallow-water bathymetric side-scan sonar,
            the Bathyscan 300, were conducted in
            August, 1987, in the Chesapeake Bay. The
            results of those tests, as well as the
            performance demonstrated by other
            bathymetric side-scan sonars, are compared
            to the predictions of the model.

                           1. INTRODUCTION,
                                                                 Bathymetric Side-Scan Sonar Technique
                                                                               Figure 1
            The National Ocean Service (NOS) is
            responsible for mapping and charting of the       Systems of this type can be towed near the
            waters around the United States. Surveys          surface at the same speeds that hull-
            conducted to meet this responsibility must        mounted systems are operated. They can
            be done efficiently, they must meet               provide complete coverage of the seafloor
            international accuracy standards, and they        over swaths of 3.4, and perhaps as much as
            must be adequate to withstand legal               10, times the towfish altitude. High
            scrutiny in liability cases. Bathymetric,         frequency versions can operate in water
            or interferometric, side-scan sonar systems       depths as shallow as 10 meters or less.
            offer substantial potential improvements          The spacing between conventional survey
            over current techniques in a wide variety         lines can be increased and still provide
            of conditions.                                    greater confidence that all natural
                                                              features and obstructions to navigation
            The basic interferometric technique uses  a       have been detected. In deeper water, low
            pair of transducers which are very similar        frequency versions can reach to 6,000
            to those used for conventional side-scan          meters or deeper.   The broad swath width
            systems. A pulse is transmitted just as in        of these systems means that the rate of
            a conventional system. In addition to             area coverage by a survey ship can be four
            monitoring the amplitude of the returning         times (or more) greater than with today's
            echo, the phase difference between these          multibearn systems. In addition to
            two transducers is monitored. This phase          providing more complete and efficient
            difference indicates the direction of             coverage, bathymetric side-scan systems
            arrival of the echo at any instant. From          also provide bottom backscatter imagery
            the angle and time, depth can be computed         indicating bottom composition.

                                                        379 United States Government work not protected by copyright

              The disadvantages of this technology, as of         systems is now offered by Honeywell. These
              recently, have been that the accuracy did           systems evolved from equipment developed
              not meet international standards and that           for manganese nodule exploration and the
              the large amounts of data produced could            search for the Titanic. International
              not be processed efficiently. Progess is            Submarine Technology (IST), the Hawaii
              being made in both areas. As a                      Institute of Geophysics (HIG) and Seafloor
              contribution to this progess, NOS sponsored         Surveys International (SSI) all made
              the development of a theoretical model of           important contributions to the development
              the accuracy of bathymetric side-scan               of the bathymetric capability. The newest
              systems. In addition, in order to obtain            version of SeaMARC is being developed in
              direct experience, a field test of a                cooperation with Texas A&M University
              shallow-water version was conducted in              (TAMU). The characteristics of the
              August of 1987.                                     Bathyscan 300 and the SeaMARC systems are
                                                                  shown in table 1.

                              2. BACKGROUND                       These systems are not yet available "off-
                                                                  the-shelf". However, the SeaMARC II
                                                                  (offered now as Honeywell's series 12) and
              The first experiments with the                      the SeaMARC/S (offered as Honeywell's
              interferometric technique for seafloor              series 150) have seen extensive operational
              mapping were conducted in the 1960s (see            use in recent years. They have clearly
              Chesterman et al, 1967 and Lowenstein,              developed beyond the research phase.
              1970). Research continued through the
              1970s and 1980s at a number of locations
              around the world. The BASS system was                           3. THEORETICAL MODEL
              built in the United Kingdom (Denbigh,
              1979). The SeaMARC II system was built in
              the United States (Blackinton and Hussong,          The accuracy of a bathymetric side-scan
              1983). The IDSS system was built in West            sonar system is affected by many of the
              Germany (Kolouch, 1984). The TOPO-SSS               same factors that limit the accuracy of
              system was built in Norway (Klepsvik,               multibeam systems. The most important of
              1984). The technique has been employed in           these common factors are errors related to
              Canada (Caulfield, 1984) and the Soviet             sound velocity and errors related to the
              Union (Aleksandrov, 1983).                          sonar attitude. The other large factor in
                                                                  a multibeam, system is the error in
              Recently, the first systems of this type            estimating the travel time for an echo to
              began to be available as commercial                 return in a given beam. The travel time
              products. The Bathyscan 300, offered by             error is related to the transmit pulse
              Bathymetrics, Ltd., is a direct descendant          length, the composite transmit-receive
              of the BASS system and other work done in           beamwidth, the signal-to-noise ratio, and
              the United Kingdom. The SeaMARC family of           the shape of the seafloor within the beam.

                                                            Table 1
                                                Bathymetric Side-Scan Systems

                       System                SeaMARC           SeaKARC           SeaMARC       Bathyscan 300
                                            Series 12         Series 70        Series 150

                      Developer              IST/HIG          IST/TAMU           IST/SSI         Bathymetrics

                     Max. Depth               6,000             2,000               300               60
                  Below Towfish  (m)

                   Frequency (kHz)            11/12              72                 150               300

                  Max. Swath Width
                                (m)          10,000             2,000             1,000               200
                (% towfish altitude)           340               340                340               700

                 Towfish Length (m)            5.5               2.5                 2                  2

                 Towfish Weight (kg)          1750               150                204               180

                 Max. Tow Speed (kt)           10                10                  6                  8

                  Number of Systems             1               under                1                  1
                       Fielded                              construction

                                                            380

              In an interferometric system, the error
              source analogous to travel time in a
              multibeam system is that of estimating the                when (p TE which caused the broadest
              direction of arrival from the phase                       distriKution. when Tl=n/2 it was found
              difference between the transducers. The                   that the interference not only broadens the
              relationship of this error to the design                  distribution, producing a standard
              parameters of the sonar is not well known.                deviation of:
              Several investigators have considered this                                       a=1.5/,/(S/I)
              problem. The consensus starting point is
              the probability density function of the                   but also shifts the mean of the
              phase difference as derived by Ol'shevskii                distribution away from the direction of the
              (1967):                                                   wanted signal by:
                        1-IRi2             (P)+TEP/2+(j_p) 1/2 ]
              f(d(p)= ----------  [Psin                                 A program was written by Science
                     2Tx(l_p2)3/2                                       Applications International Corporation
                                                                        (SAIC, 1987) to incorporate this result
                  for jd(p-4j<TE                                        into an overall performance prediction for
                                                                        bathymetric side-scan sonars. The user
                  and 0=jRjcos(dT-W                                     specifies both the system design parameters
                                                                        and the operating environment. This model
              where dT is the phase difference, Vt is its               includes not only the depth errors related
              mean value, and R is the crosscorrelation                 to phase estimation, but also those related
              coefficient. This is a peaked distribution                to sonar attitude and sound velocity. The
              whose width increases as the                              program also calculates the errors in
              crosscorrelation decreases.                               positioning soundings produced by the
                                                                        specified system.
              The crosscorrelation coefficient is                       Figure 2 is a representative result of this
              difficult to obtain in circumstances of                   program. For this particular run:
              interest. Alexandrou (1987) considered          the         Sonar Design
              cases of homogeneous volume reverberation                         frequency: 300 kHz
              and single surface boundary reverberation                         transducer width: 0.44 cm
              which indicate how the crosscorrelation                           receiver spacing: 5 cm
              depends on receiver seperation and                                receiver tilt angle: 200 below
              orientation. Gapper and Hollis (1985)                                 horizontal
              demonstrated the dependence of the                                attitude errors: 0.10 rms (roll,
              crosscorrelation on signal-to-noise ratio                             pitch and yaw)
              and the autocorrelation of the transmit                           towfish depth error: 10 cm rms
              waveform. Klepsvik (1984) showed that the                         sound velocity error: negligible
              crosscorrelation can be factorized to                       Environment
              include the dependence on both the transmit                       water depth: 50 m
              pulse and the reverberation                                       towfish depth: 10 m
              characteristics. Additional effects,                              bottom type: sand
              primarily interference produced by back-                          wind speed: 10 knots
              scattering from surfaces other than the
              seafloor, are recognized as limiting
              factors.   Multipath interference involving             Depth Error (1.25 WAY)
              reflections from the sea surface is the
              reason that coverage is limited to 3.4                  Coverage (m 2/see) 513
              times the water depth in the SeaMARC
              systems. Glint, or interference produced
              by multiple strong reflectors on the
              seafloor, can also have an important effect
              on the phase distribution (Blackinton,
              1986).

              Denbigh (1987), in an effort sponsored by
              NOS, developed a relationship between the
              probability density function of the phase
              difference and the signal-to-interference
              ratio, S/I. The interference was assumed
              to arrive from a direction different from
              the desired signal and which would cause a                          Dis tance (25 R/div)
              phase difference, @pj, between the two
              receivers. He showed that the width of the
              probability distribution of phase                         Theoretical Model Performance Prediction
              differences, expressed as a standard                                          Figure 2
              deviation, could be approximated by:
                                                                      --Measurements were -a-l-lowed-to -be-aver-aged-

                                                                381

              over a 10 square meter area as the system         was orders of magnitude greater. The final
              moved at 5 knots. The figure shows that           form of the data was as a 5 meter grid.
              the rms errors remain below 1% of the water       The rms difference between the gridded data
              depth out to a range of 100 meters. To            from the two sets of lines was about 0.2
              meet international standards, which require       meters. Data analysis has not yet been
              that the total error not exceed 1% of the         completed but the differences with respect
              depth or 0.3 meters (whichever is greater)        to the conventional echo-sounder data
              with a probability of at least 90%, the           appear to be no greater than the
              range would be restricted to about 75             differences between the two grids.
              meters. These parameters are close to the
              specifications and typical operating              The second portion of the tests, designed
              conditions for the Bathyscan 300. The             to examine survey suitability, was to cover
              model's prediction is in general agreement        a larger area over the range of conditions
              with the manufacturer's specification. The        available within the Chesapeake Bay. The
              model indicates only small dependence on          area chosen was 1 mile by 5 miles in extent
              bottom type, but strong dependence on wind        and included water depths from 9 to 50
              speed. The model's predictions for other          meters. Operations were conducted as a
              systems are close to the manufacturer's           routine survey as much as possible.
              specifications and to the results of              Conventional echo-sounder data was gathered
              operational experience.                           simultaneously. Figure 3 is a stacked-
                                                                profile perspective plot of the results of
                             4. FIELD TESTS                     this portion of the tests. The survey
                                                                lines in this area were also spaced by 70
              Field tests of the Bathyscan  300 were            meters. The work was completed in 3 1/2
              conducted from the NOAA ship  Rude during a       days of routine operations. The towing
              two-week period during July and August of         depth was maintained at 3 meters. Adequate
              1987 in the Chesapeake Bay. The Bathyscan         returns were obtained out to ranges of 100
              300 was viewed both as an example of a            meters except in a small region in the
              bathymetric side-scan sonar and as a              deepest part of the survey area. A 5 meter
              promising tool for surveying of harbors and       grid was produced from the data and the
              harbor approach areas. The tests were             plot drawn from this grid. Random
              divided into three phases to test accuracy,       variations are clearly not greater than a
              suitability for surveying, and capability         few tenths of a meter. Comparison with the
              for detection of obstacles.                       conventional echo-sounder data showed
                                                                differences of up to 1 meter which extended
              The first portion, designed  to check             over fairly large areas of the grid. These
              accuracy, was run over a generally flat           appear most likely attributable to errors
              bottom in approximately 12 meters of water.       in the towfish depth. A combination of
              A 3/4 mile square area was surveyed with          information from a pressure sensor, an
              two sets of perpendicular lines. Data from        accelerometer and adjacent swath data is
              the standard conventional echo-sounder, a         used to establish this depth.
              Raytheon DSF-6000N, was collected
              simultaneously for intercomparison. The           The third portion of the tests was designed
              Bathyscan system was towed at a depth of 3        to examine the capability of this type of
              meters and a speed of about 5 knots. The          system to detect obstacles to navigation.
              normal 300 depression angle was reduced to        Several objects which had been investigated
              200 to get better coverage in this depth of       by other means were used for targets. The
              water. Ranges consistently exceeded 70            most useful data came from the wreck of a
              meters and typically exceeded 100 meters          pile driving barge. The dimensions of the
              which is the manufacturer's specification.        barge were 60 feet by 25 feet. It had been
              This is more than 10 times the altitude of        investigated using conventional side-scan
              the towfish above the bottom. There was no        sonar and divers. The bathymetric data
              evidence of degradation of the output at          from the Bathyscan system forms an image
              the range at which surface-bottom                 which shows the scouring that has taken
              interference would be received. An                place around the wreck. When the
              apparent penalty for this immunity to             discontinuity in the bottom profile at the
              interference which permits long range             edge of the hull is less than a few feet,
              operation is a gap in coverage directly           the bathymetric data maintains track and
              beneath the towfish. To fill this gap the         produces an image of the wreck itself. By
              line spacing was reduced from the full            adjusting the spatial averaging to trade
              swath width of 200 meters to 60 and 70            off accuracy for spatial resolution and
              meters for the two sets of lines. This            also by adjusting the ping rate and tow
              also insured substantial overlap between          speed, the system can be made to detect
              lines of data which is important in the           smaller objects.
              processing of Bathyscan data. The area
              coverage rate was slightly less than that         Weather conditions during the tests were
              of a conventional system which would              consistently good. Within that limited
              typically be run at 10 knots and 50 meter         range of conditions the system performance
              line spacing, but the density of coverage         appeared independent of wind speed contrary

                                                          382

             to the model's prediction. The bottom
             material in the test areas ranged from soft                      6. REFERENCES
             mud to sand. The ranges achieved by the
             system were clearly dependent on the type
             of bottom. Mid-water targets, probably            Aleksandrov, A. A. et al. (1983), "Study of
             biological, which were very common in the         Sea Bottom Characteristics by Side-Looking
             area could also disrupt the system                Phase Sonar", Oceanology, 23, 3, 378-381.
             performance but controls available  to the
             operator were generally able to reject            Alexandrou, Dimitri (1987), "Computer
             these effects.                                    Simulations of Bathymetric Side Scan
                                                               Sonar", oceans '87 Proceedings, 1168-1174.
             The Bathyscan system proved to be robust
             and well-engineered. No major problems            Blackinton, J. Grant (1986), "Bathymetric
             were encountered in set-up or field               Mapping with SeaMARC II: An Elevation-Angle
             operations. The experience and results   of       Measuring Side-Scan Sonar System", Ph.D.
             the tests suggested that improvements could       dissertation, University of Hawaii.
             be made in the towfish depth sensor, the
             interface with the positioning system, and        Blackinton, J. G. and Hussong, D. M.
             the real-time displays. It appears                (1983), "First Results from a Combination
             possible to design a system to be towed at        Side Scan Sonar and Seafloor Mapping System
             higher speed and to provide some form of          (SeaMARC II)II, Offshore Technology
             coverage in the near vertical. Two weeks          Conference Proceedings, 4478-4484.
             following the tests had been planned for
             data processing. The task could not be            Caulfield, D. D. et al. (1983), "Stereo
             completed during that time however the            Side-Scan as a Complement to Echo Sounding
             processing software has since been                for High Resolution Bathymetric Studies",
             considerably improved. The tests provided         USN/SEG Three Dimensional Data Symposium.
             evidence that it is possible for this type
             ofd system to meet international accuracy         Chesterman, W. D. et al (1967), "Acoustic
             standards. The ranges that were achieved          Surveys of the Sea Floor near Hong Kong",
             indicate that it should be possible to            International'Hydrographic Review, 44, 1,
             design a system based on this technique           35-54.
             which would be capable of much higher area
             coverage rates than conventional systems.         Denbigh, P. N. (1979), "A Bathymetric Side
             The high spatial resolution data produced         Scan Sonar", Ultrasonics International 179
             by such a system will prove to be of great        Conference Proceedings, 321-326.
             value.
                                                               Denbigh, P. N. (1987), "Bathymetric
                                                               Sidescan Sonar; A Study of its Suitability
                              5. SUMMARY                       for the Charting of the Sea Bed",
                                                               unpublished report for NOS under contract
                                                               #50-DGNC-6-00203.
             Bathymetric side-scan sonars have
             demonstrated considerable promise for             Gapper, G. R. and Hollis, T. (1985), "The
             hydrographic and bathymetric surveying.           Accuracy of an Interferometric Sidescan
             The technique has been shown to be                Sonar", Proc. Inst. Acoustics, 7, 3, 126-
             applicable to shallow harbor areas as well        131.
             as the deep ocean. A theoretical framework
             for prediction of their performance has           Klepsvik, John 0. (1984), "TOPO-SSS: Real
             been established. The development of              Time Bathymetric Mapping with a Side Scan
             models and operational hardware will              Sonar", HYDRO 184 Proceedings, 42-49.
             continue. This technology is likely to
             play an important role in surveying in the        Kolouch, Dieter (1984), "Interferometric
             near future.                                      Side Scan Sonar, A Topographic Seafloor
                                                               Mapping System'11, International Hydrographic
                                                               Review, 61, 2, 35-49.

                                                               Lowenstein, Carl D. (1970), "Side Looking
                                                               Sonar Navigation", J. Institute of
                                                               Navigation, 17, 1, 56-66.

                                                               01'shevskii, V. V. (1967), Characteristics
                                                               of Sea Reverberation, (Consultants Bureau,
                                                               New York).

                                                               SAIC (1987). "Theoretical Analysis of
                                                               Bathymetric Side Scan Sonar", unpublished
                                                               report for NOS under contract #50-DGNC-6-
                                                               0203.

                                                         383

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                                           Bathyscan 300 Survey Data
                                                  Figure 3

                                                   384

                          PROCESSING AND MANAGEMENT OF UNDERWAY MARINE GEOPHYSICAL DATA AT SCRIPPS

                                                                 Stuart M. Smith, James S. Charters and J. Michael Moore

                                                                      Scripps Institution of Oceanography, Code A-023
                                                                             University of California, San Diego,
                                                                                     La Jolla, CA 92093

                                              ABSTRACT                                                    In 1984 the IBM 1800 machines were replaced by Vax
                  'Underway marine geophysical data           (navigation, depth; Sea               lln30s for shipboard processing and the shore processing and
                  Beam, magnetics and gravity) collected on Scripps cruises are                     data management consolidated onto a compatible Vax 11/750 at
                  processed and displayed at sea or on shore on Vax computers                       Scripps. Most computer code was modified or rewritten for the
                  under the UNIX BSD 4.3 operating system. An on-line Master                        interactive terminal and disk Me environnient provided by these
                  Abstracts file allows users to search a data base containing more                 computers and the UNIX(*) operating system (Berkeley,BSD
                  thari 1300 cruise legs from Scripps and other sources by geo-                     4.3).
                  graphic region or data type. Sea Beam archive procedures and a                          In the following sections, we first describe how the pro-
                  tape archive index are briefly described.                                         cessing and management system has been implemented under
                                                                                                    UNIX. We then discuss the processing procedures for data col-
                                         1. INTRODUCTION                                            lected on a single cruise followed by an explanation of multiple
                        The Scripps Institution of Oceanography (SIO) currently                     cruise data management After a brief outline of Sea Beam data
                  operates 4 research vessels to support sea-going research pro-                    archiving, we end with a description of the options available to
                  grams in all oceanographic disciplines. In the field of marine                    plot the specified data.
                  geophysics, underway data (navigation, depth, magnetics and
                  gravity) are collected continuously at sampling rates ranging                               2. DATA MANAGEMENT UNDER UNIX
                  from seconds to minutes over the duration of a cruise leg, typi-                        The UNIX operating system has proved an excellent
                  cally 30 days. The resulting amount of data becomes rapidly                       environment for the amount of data processing and archiving
                  overwhelming and a system has been developed, at SIO to pro-                      done by CDC, once the early difficulties were past on the learn-
                  cess and manage underway marine geophysical data collected on                     ing curve due to the terse, sometimes obscure and "trees but no
                  SIO ships or obtained from other sources.                                         forest" documentation. Programs are coded in Fortran-77 with
                        The system had its origins in the early 1960s when H.W.                     occasional "C" subroutines. UNIX C-shell scripts have been
                  Menard, one of the pioneers of sea floor topography analysis,                     written for user interface, for chaining together UNIX utilities
                  encouraged the senior author to look into computer processing of                  and programs and for job scheduling. Input and output redirec-
                  the Institution's bathymetric data. Magnetics were added in                       tion with pipes and filters add to the flexibility. There are a
                  1968 in a crash program to digitize these data because of the                     number of tools provided with UNIX, such as 'grep' to list lines
                  exploding interest in sea floor spreading. In 1981, a Sea Beam                    that do (or do not) contain a target pattern; 'awk' for pattern
                  multibeam echo sounder was installed on SIO's principal geo-                      scanning and processing; a 'sort' command-, and 'cat' to con-
                  physical research ship, the R/V Thomas Washington. Procedures,          ,         catenate files. The inverted tree directory structure, few file
                  for processing and archiving this new influx of data (up to I                     naming restrictions, the use of wildcards and the ease of moving
                  Mbyte per day of survey) were included in the system. Gravity,                    between directories all enhance the processing environment.
                  previously processed for relatively few cruises, was added in                     The UNIX definition of a file as a simple stream of bytes is a
                  1987 when a new gravity meter was installed on the Thomas                         significant advantage compared to other operating systems which
                  Washington.                                                                       require that various kinds of files be defined with different for-
                        Responsibility for data archiving, as well as the mainte-                   mats and modes of access.
                  nance and development of the data management system was                                 Most files in the system are in ASCII character mode (with
                  assumed by the Geological Data Center (GDQ when it was esta-                      lines defined by new line characters) to take advantage of the
                  blished in 1970. Extensive programming support has been                           environnient, screen editor and tools provided by the operating
                  provided by the Shipboard Computer Group (SCG). Both                              system. By local convention, lines with a V" character in the
                  groups are now part of the Ship Technical Support Division of                     first column are comments and are ignored by the processing
                  SIO.                                                                              programs. This scheme has proved very useful and flexible for
                        In past years, various parts of the system have resided on                  headers, file documentation and processing notes that become
                  different computers: Control Data 1604 and 3600, Burroughs                        part of the file instead of being lost in a separate file or notebook.
                  7600 and IBM 1800. The IBM ma@hines were the seagoing                             Files which are large and require little direct human interaction
                  computers on the larger Scripps ships from 1967 to 1984. Reli-                    are in binary integer mode for compactness and computational
                  able, but out of date and punch card based, they were the first                   efficiency. Floating point mode is not used for data storage to
                  installation of general purpose computers in continuous oper-
                  tion on academic research ships.                                                (*) UNIX is a trade mark of AT&T Bell Laboratories.
                                                                                            385 Unites States Government work not protected by copyright

                         reduce machine compatibility problems.                                                                   SIO NAVIGATION PROCESSING
                                                                                                                                                                               W
                              For clarity, the data flow charts that illustrate this paper                                                                        oran
                         show only the main program names and files. In fact, most pro-
                         grams are called by UNIX C-shell scripts and may have addi-                                                                               lora
                         tional terminal input as well as ancillary list or status files.
                                                                                                                                              ........ Z@iv(
                                                                                                                                          mag  av..                         file. cs.Vdratv
                                                                                                                                            fit :::: SAM f                        s a@c
                                   3. SINGLE CRUISE LEG PROCESSING                                                                                                             110
                              The underway (u/w) collected on SIO ships and managed
                         by GDC include the ship's navigation and geophysical data:                            gps-interp      navrtv          msetrtv         reformat        veccsospd
                         magnetics, gravity and depth (single point and multibeam bathy-                                        (set)                        'awk' script
                         metry). An overview of the hardware and software used for the
                         real-time acquisition and logging of these data has been given by                                      transit                         Loran
                         Abbott et al., [11 and Moore et al., (2]. In this section, we                                        file: saida                     file: lordta
                         expand on these narratives with a description of the post-                         GPS - 1 m riffle                   transit                         Imin avg
                         processing and management procedures applied to the navigation                        file: gpsdta                 file: msatdta                     file: csespd
                         and u/W geophysical data from a single cruise.
                              At sea, files containing data with GMT time from each sen-                       decimate                                        decimate         nevrtv
                         sor or instrument are dumped to tape approximately every two                          'awk' script                                  'awkl script       (csesp
                         days by SCG personnel using the UNIX 'tar' tape archive utility.
                         By convention each log file, and other files produced in process-
                         ing, are named by concatenating the type of logged or processed
                         data and an end date suffix (e.g. MGpfile.88mai,06 for logged                              GPS - 0 min.                      Loran               'significant"
                                                                                                                  file: goscita. 10min           file:                     cse1spds
                         magnetic data Me ending on 6 March 1988). All files are for-                                                                lordta. lomin       file: cspdta
                         matted in ASCII character mode unless otherwise stated.
                         Navigation
                              As seen on the flow chart in Figure 1, the ship's navigation                                          merge
                         is derived from Transit Satellites, GPS or Loran-C for position,                                         (unix utility)
                         from a dual-axis Doppler speed log for speed and from a gyro-                                                                               nav integration
                         compass for heading. The characteristics of the data derived                                screen           fixes                              fIxPI
                         from these sensors and the corresponding processing programs                                 EDIT        file: sardta
                         listed on the flow chart are as follows:                                                                                               P nterfile
                         TRANSIT SATELLITE: Log file 'satfixes' contains position                                                                              file nav1st
                         fixes received on a dual frequency ITT Transit Satellite receiver
                         at intervals ranging from 20 minutes to six hours. Program                                                            Figure I
                         Inavrtv' converts the data from each fix into a one line record in
                         Me 'satdta' which is inthe input format for fixes required by the                     minute average and puts the result into file 'csespd' in the same
                         navigation integration program 'fixpi'. As a backup, fixes from a                     format. This file in turn is input to program 'navrtv(cse)' which
                         single frequency Magnavox receiver are logged in file                                 calculates "significant" course and speed points which are put in
                         'MSAinpf' and converted to another file 'msatdta' by program                          Me 'cspdta'. (A "significanf' point occurs if the dead reckoning
                         Imsatrtv'.                                                                            (DR) position of a given point falls outside a circle with a radius
                                                                                                               of 0.02 nautical mile from the position obtained by extrapolating
                         GLOBAL POSITIONING SYSTEM (GPS): Log Me 'GPTinpf'                                     the previous course and speed.)
                         contains fixes received on a Trimble GPS receiver that is set to                      NAVIGATION INTEGRATION: The 'cspdta' and 'satdta' files
                         output fixes at 10 second intervals. Program 'gps-interp' inter-                      are next input to a much modified version of program 'fixpi',
                         polates between fixes, when necessary, to produce a one line                          received a number of years ago from the Lamont-Doherty Geo-
                         record at exact one minute intervals. This line is written to file
                         'gpsdta' which is further decimated to 10 minute intervals by a                       logical Observatory of Columbia University. This program
                         UNIX 'awk' script into file 'gpsdta. I Ontin'.                                        linearly interpolates positions of course and speed changes
                                                                                                               between consecutive fix pairs and outputs the integrated naviga-
                         LORAN: Log file 'loran' contains fixes received on a Trimble                          tion to a 'navIst' list file (which has proved to be a good naviga-
                         Loran-C receiver at 7 to 10 second intervals. A UNIX 'awk'                            tion export format) and to a binary 'navbin' file that is used
                         script converts the data into the input format for fixes in file                      internally on the Vax for further processing. In the 'navbin' Me,
                         'lordta' which is further decimated to 10 minute intervals by                         time is stored in "UNIX seconds" (i.e. time in seconds since I
                         another script into file 'lordta.10min'.                                              January 1970) rather than in multiple time units. In order to pro-
                         FIX MERGING: Fixes from the above files, which share a com-                           cess historical data collected prior to 1970, we have modified the
                         mon format, are merged and sorted by time into a combined                             UNIX system's utilities for time conversion so they can handle
                         'satdta' file using the UNIX 'sort' utility. An experienced opera-                    negative seconds. Latitude and longitude are each stored as two
                         tor must then select the best subset of fix data using the screen                     16 bit integers (minutes North of the South pole or minutes East
                         text editor, a process that may require up to an hour for data col-                   of the Prime Meridian) and as parts of a minute times 10,000.
                         lected over a two day period.                                                         This method allows a resolution of position to 18 cm on the
                         COURSES AND. SPEEDS: Log file 'csespd.raw' (binary                                    earth's surface while avoiding floating point round off or
                         integer) contains 10 second averages of courses and speeds sam-                       conversion problems.
                         pled at one second intervals from the ship's gyrocompass and the                      NAVIGATION EDITING: Once courses and speeds are free of
                                                                                                                                                                                 ccsospd

                                                                                                                                trarts@
                                                                                                                              file. sa

                         2-axis Doppler speed log. Program 'veccsespd' calculates a one                        errors, bad or questionable fixes are removed until the output

                                                                                                        386

                       shows drifts varying smoothly between consecutive pairs of                                                           $10 U1W GEOPHYSICAL DATA PROCESSING
                       fixes. Producing a satisfactory navigation file may take 3 or 4
                                                                                                                            M
                       runs of the integration program and require several hours of
                       knowledgeable human interaction for two days of navigation                                                                                                          ea earn apt
                                                                                                                                6 sec. total field                                                          les
                                                                                                                                                           1 sec metelloounts            -16 sec. P1
                       data.
                                                                                                                                                                      twile      4.
                                                                                                                                                               file: G
                                                                                                                                                                      vpfjje
                       Geophysical Data
                              The magnetics, gravity and depth data flow are illustrated                                                            X
                       in Figure 2 in the same format as used for the navigation.
                       MAGNETICS: Log file 'MGpffle' (binary integer) contains
                       magnetic total field readings received from an EG&G                                                          magrt                      beilgray                        sbcrtv
                       Geometrics magnetometer at six second intervals. Program
                       'magrtv' calculates one minute averages and puts the results in                                                                                                         depth
                       file 'mag.uwts' (magnetic underway time series).                                                             magnetic                    gravity                    vertical beam
                                                                                                                                  1 min avg.                   I min avg.                   I min avg.
                       GRAVITY: Log file 'GVpfile' (binary integer) contains one                                                file: ma_q.uwts              file: gravuwts                 file:  d@qpxwfs
                       second interval counts received from a Bell Aerospace BGM-3                                                                EDIT                           EDIT
                       gravity meter. Program 'bellgrav' applies a recursive 25 pole
                       filter and a 148 second time delay to filter the short period ship
                       accelerations and puts one minute values in file 'grav.uwts'.
                       DEPTH: For cruises when the Sea Beam multibeam echo                                                        navigation                    UWmerg
                                                                                                                                                             Cale mag. grav
                       sounder is operating, the Sea Beam log file 'SBrtm' contains 34                                           file: navbin              free-air anomalies
                       data words (up to 16 depths, 16 horizontal distances, heading and
                       time) per ping cycle (one to 16 seconds, depending on ocean
                                                                                                                                                                                     U Cho
                                                                                                                                                                                                            profit
                                                                                                                                                                                     List time
                                                                                                                                                                                                            r
                       depth). The average value of depth measured on the vertical                                                                                  U/W
                                                                                                                                                                                     List time,
                       beam is extracted over one minute intervals by program 'sbcrtv'                                                                        merged data
                                                                                                                                                                                     Zia gaps               P
                                                                                                                                                               file: uwmrg                                  ip ti
                                                                                                                                                                                          rro               a
                                                                                                                                                                                                            aip ti
                       into file 'dep.uwts'. Note that only the vertical beam depth                                                                                                         rs              hi
                       measured with the Sea Beam system is used here, This is done                                                                                                                             ....... ..
                                                                                                                                                                                                            ...... ..............
                                                                                                                                                                                                            @i .. .. ... .
                                                                                                                                                                                                            profil
                       to conform to existing geophysical data exchange formats
                                                                                                                                                                                                            pot
                       (MGD77) as described below. Management of the full set of Sea                                                                                                                            ........ .
                       Beam data is discussed in Section 5. For legs without Sea Beam,                                                                           Figurce 2
                       depths are manually scaled from a depth recorder trace at five
                       minute intervals and the values typed directly into a 'dep,uwts'                                   merging by subtracting the Gravity Reference Formula (GRS 67)
                       Me with the help of script 'enterdepths'.
                                                                                                                          and adding the E6tvos cortection to the measured gravity value.
                       GEOPHYSICAL DATA EDITING: The 'uwts' files are the                                                 ARCHIVING, REPORTS AND MICROFILMING: After edit-
                       archived form of the data time series and they share a common                                      ing, the processed files, containing approximately two days of
                       format. Each record contains the date (year, month, day) and six                                   data of each type, are concatenated and the final files named by
                       pairs of time (hours, minutes, seconds) and data value. Each file                                  file type and cruise ID (e.g. uwmrg.TUGA02WT for the u/w
                       is passed through two editing procedures. Program 'uwchek'                                         merge file'of Tortuga, leg 2 on R/V Thomas Washington). The
                       lists times when data errors or gaps exceeding user defined limits                                 final time series, navigation and merged files are copied to tape
                       occur, whereas program 'tvprof' produces a proffle of data value                                   (2 copies) using the 'tar' utility. A report is prepared containing
                       vs. ship time on a CRT screen or on a hardcopy dumped to the                                       track charts, a Sample Index and profiles of depth, magnetic and
                       printer. Errors are then edited with the UNIX 'vi' screen editor.                                  free-air anomaly. The Sample Index is a first level interdisci-
                       DATA MERGE WITH NAVIGATION: The 'uwts' files for                                                   plinary index which gives the begin/end time and position of all
                       depth, magnetics and gravity are merged with the 'navbin' navi-                                    records, samples and measurements collected on the cruise leg.
                       gation file by program 'uwmerg' to produce a single 'uwmrg'                                        The original u/w recorder records and the Sea Beam swath plots
                       merge file. (An ancillary file also lists any time errors that'may                                 are microfilmed onto 35mm continuous flow microfilm to pro-
                       have gone undetected in earlier processing). Each record in the                                    vide easy access to these data without compromising the original
                       merge file contains time and position stored in the same fashion                                   records.
                       as described above for the 'navbin' file, depth (two-way travel
                       time in seconds times 10,000), magnetic total field and anomaly                                                4. MULTI-CRUISE DATA MANAGEMENT
                       (in nano-Tesslas times 10) and measured gravity and free-air                                              The 'uwmrg' files form the principal u/w data archive. In
                       anomaly (in milligals times 100).
                                                                                                             I .          order to manage these data, we use a program to search an on-
                              During the merge process, the magnetic anomaly is calcu-                                    line abstract file and have utilities to assist users in uploading
                       lated by subtracting the International Geomagnetic Reference                                       files from tape to disk as illustrated in Figure 3. We have also
                       Field (IGRF) value for the appropriate position and date from the                                  developed an index for locating magnetic tapes in the GDC
                       measured value. The magnetic field is calculated at the comers                                     archives and methods for data exchange with other institutions.
                       of a one degree square containing the first position and, as long                                  UNDERWAY MERGED DATA ARCHIVES: The 'uwmrg'file
                       as the ship remains in that square, the field is calculated by inter-                              for each cruise leg, typically one month long, is about I Mbyte
                       polation of the comer values. This method requires considerably                                    when data are stored at intervals of one minute of ship time.
                       less computation than calculating the field at each point. The                                     Files for older cruises, when data were manually digitized from
                       maximum difference observed between the direct and interpo-                                        the records at 5 minute intervals, are correspondingly smaller.
                       lated method is 2.7 nTesslas.                                                                      The archives hold more than 500 files of Scripps cruises for legs
                              The gravity free-air anomaly is also calculated during                                      going back to the late 1950s. Although GDC does not attempt to

                                                                                                                  387

                                   BID U/W DATA IMPORVEXPORT, ABSTRACT AND SEARCH                                                    The 'DOsearch' program generates a hit file list of all
                                                                                                                              cruises satisfying user supplied criteria of geographic location
                                                                                                       MGD77                  and data type. The 'abstract.header' file is first searched for
                               Tape           tar            u merge                                   (Import)               bounds overlap of each cruise with the area specified and for
                             Archives        udlity         file: uWmrg                                                       types of data if also requested. if the header for a cruise passes
                                                                                                                              the tests, then the 'abstract.data' for that cruise is examined to
                                                                                                       header                 determine if an abstract line segment passes through the search
                                     abstracter                                       uwmrg to         Ile: mgdhd             area. If depth, magnetic or gravity data are also specified, the
                                                                                      mgd77    ..........                     data flags for that segment are also examined and must be true
                                                                                                                              for a hit. The search hit file can, in turn, be input to scripts
                                                                                      MGD77                                   'DOmake.uwtar.ffles' and 'DOload.uwtar.tapes' to make tem-
                                     entarcrulss                                       xport)                                 porary script files of 'tar' commands and user prompts for tape
                                                             adittapold
                                                                                            . . .....                         loading. If a large number of cruises are to be plotted, script
                                                                                                                              'DOmake.infile.lines' produces lines formatted for the 'unlot,
                                                                                                                              input command file.
                                                                               DO                      CRT
                                                                                 absplot
                                                                                                       plats                  RVIPORT/EXPORT: The MGD77 format is the standard for
                                                                              quick Index
                                                                                 plots
                                                                                                                              exchange of navigation, vertical beam depth, magnetics and
                                                                                                                              gravity between academic institutions and for transmission to
                                                       DOsearch
                               11stabscru                by area                                                              and from the National Geophysical Data Center [4]. MGD77
                                                       or data type                                                           files received from these and other sources are input to program
                                                                                                                              'fmgd77' to produce a Me in the 'uwmrg' format (Figure 3).
                             Usts ot headers                      search                                                      The magnetic anomaly can optionally be recalculated using the
                             (arid absbr.data)                   hit file             DO make. IntIle.111nes                  most up to date IGRF reference field. For export, program
                                                          DOMake.uwtarmiss                  Icf     0'                        'tmgd77' generates a disk file in MGD77 exchange format using
                                                                                              '--@'-_.Waaalln-d )
                                                                                             coffi,.:                         the 'uwmrg' file and a 'mgdhd' (MGD77 header) file as input. A
                                                                                               file
                                                                                                                              script dumps MGD77 files to tape and provides listings of header
                                                                temp.flies       DOload.uwtar.tapas                           records, file sizes and other tape statistics.
                                                                                                                              TAPE ARCHIVE INDEX: In addition to the 'uwmrg' tapes
                                                                Figure 3                                                      described above, GDC currently archives over 1000 reels of
                                                                                                                              magnetic tape of data from Scripps cruises logged by SCG as
                             duplicate the holdings at the National Geophysical Data Center                                   well as other types of marine geophysical data, such as gridded
                             (NGDC), throughout the years data from other sources have been                                   bathymetry, heatflow and data sets from the Deep Sea Drilling
                             acquired in response to requests by Scripps students and staff                                   Project. A relatively simple but effective index has been
                             bringing the total number of cruise legs to over 1300. These                                     developed to keep track of these tapes. Each tape reel has one
                             data, totalling nearly 500 Mbyrtes, currently reside off-line on                                 record in a 'tapeindex' data file with fields for reel ID, tape
                             thirty six 1200-foot reels of 9 track magnetic tape, one copy in                                 name, type of contents, data format (ASCII, EBCDIC, etc), crea-
                             the computer room and a backup in the archives.                                                  tion date, location codes and contents. A user executes the script
                             ON-LINE ABSTRACTS: Each 'uwmrg' merge file is input to                                           'DOfind.tape' with a target text such as a Reel ID, cruise name
                             program 'abstracter' which generates an 'abstr' Me containing a                                  or word in the contents field and the UNIX utility 'grep' win list
                             header record and times and positions of selected points. The                                    all lines containing the target. A secondary script examines the
                             header has the latitude/longitude bounds of the cruise and flags                                 location codes in the hit list and provides an expanded storage
                             indicating the types of data present in the merge file. Points are                               location description.
                             selected such that lines between abstract points deviate from the
                             track by no more than 5 nautical miles. A flag is set for each                                     5. SEA BEAM DATA PROCESSING AND ARCHIVING
                             data type (depth, magnetics or gravity) that is present on a given                                      Sea Beam data are processed and archived separately from
                             segment between abstract points. A typical 30 day cruise leg is                                  the other u/w data. Only the basic data flow (Figure 4) and
                             represented by several hundred abstract points, a compression to                                 archive procedures are outlined here. Details of the processing,
                             about one percent of the original merge file.                                                    plotting and navigation adjustment programs have been
                                   Each 'abstr' file is, in turn, input to program 'entercruise'                              described by Cha@rters [3].
                             which loads it to the Master Abstracts consisting of two files:                                         Program 'sbpfx' merges the Sea Beam data contained in a
                             'abstract.data' and 'abstract.headers'. The header is appended to                                'SBrtrn' log file with the integrated navigation in a 'navbin' file
                             the 'abstract.header' file with pointers to the location of the data                             to generate a Sea Beam merged 'SBint' file. This latter file, nor-
                             that are added to the 'abstract.data' Me. Entries in the                                         mally one to two Mbytes in size for two days of ship time, is the
                             'abstract,header' can be modified by programs 'edittapeid' to                                    standard archived form of Sea Beam data. The merged file is run
                             add the tape id on which the 'uwmrg' file is stored and 'editda-                                 through a checking program, 'sbchek', that lists begin/end times,
                             tacoll' to toggle flags for other types of data collected on the                                 gaps, errors and geographic boundaries of the data and appends
                             cruise but not contained in the 'uwmrg' file, such as Sea Beam,                                  summary information to a file kept for each cruise leg. The
                             3.5kHz depth and seismic reflection.                                                             merged Mes are dumped to archive tapes with the 'tar' utility
                                   The Master Abstracts can be input to a number of different                                 and can be exported to other institutions with another, more gen-
                             programs: 'listabscru' for abstract data listings of a known                                     eral, 'dd' utility. At present there is no standard format for
                             cruise; 'DOabsplot' for quick index plots of the whole leg on a                                  exchanging Sea Beam data but ad hoc exchange of well docu-
                             CRT screen; the 'uwplot' program described below; and a search                                   mented data in the various formats used by the data producing
                             program.                                                                                         institutions has worked reasonably well.

                                                                                                                      388

                                              510 SEA BEAM' DATA ARCHIVING                                                                       6. PLOTTING DISPLAYS
                                                                                                                                Maps and. profiles are the modes of u/w data display most
                                                                                                                         frequently requested- by data center users. Geologists prefer to
                                                                                                                         work with large size hardcopies so plots are usually done on
                                                                                                                         drum or belt-bed pen plotters. Both plot programs described
                                                                    fx               navigation                          below, as well as the 'sbcontour' program mentioned in the Sea
                                                                    B with
                                                            Inte r led nav.         file: na@bin                         Beam section, use an ASCII text input command file (icf) for
                                                                                                                         specifying plot commands. Although the 'icf` files differ in
                                       sbchek                                                                            detail for each program, they share many parameters and an
                                      che k for                                                 SB Input
                                  begirdernd times,                                                                      overall common structure. Command lines contain a keyword
                                    boundaries,            Sea Beam wit                         Command                  usually followed by one or more parameters in fme-field format
                                    gaps & errors             navigation                           File
                                                             file: Silint                                                (e.g. "BOUNDS 12N 5S 121W 119W"). Comment lines can
                                                                                 sbcontauf                               be included to document parameters or for notes about the plot.
                              Cruise Leg              tar                        Sea Beam
                                SB File              utility                      Contour                                UWPLOT: The 'uwplot' program plots ship tracks and data from
                                Summary                          dd                 Plots                                one or many cruises on Mercator projection at scales ranging
                                             Archived           utility                                                  from world-wide coverage to very detailed surveys (Figure 5).
                                            SB files                                                                     Tracks can be annotated with a choice of time ticks and
                                            on tape            Export              SB Plot           ta!
                                                              SB files              File             Will                date/time labels as detailed as one minute or left unannotated.
                                                               on tape                                                   Depth, magnetic total field and anomaly, and measured gravity
                                                                       Hardcopy Plots              Archived              and free air anomaly may each be profiled or printed along track
                                                                       (I 6"/deg. scale)           SB Plots              in any of four colors. Profiles values may be projected to a
                                                                       Achived all GDC             on tape               specified azimuth as is most often done for interpretation of
                                                                                                                         magnetic anomaly lineations. To plot data values with program
                                                        Figure 4                                                         luwplot', the input files must be in the 'uwmrg' format. If only
                                                                                                                         tracks are required, the input source may be a mixture of merge
                                                                                                                         files, binary navigation 'navbin' files, individual 'abstr' abstract
                             The Sea Beam merged files are used mainly for input to the                                  files or the Master Abstracts. High or low resolution coastlines
                      Sea Beam contouring program 'sbcontour' which produces                                             may also be specified.
                      UNIX standard plot files of Mercator projection maps with Sea                                             Other types of data or annotation, such as station numbers,
                      Beam contours plotted along the ship's track (across track swath                                   pon names, heatflow values, navigation fixes or plot boundaries
                      width is approximately 314 of the ocean depth). An input com-
                      mand file (icf) contains parameters for grid annotation and scale,                                 represented by symbols, lines or text may be added to the plot
                      contour intervals, etc., as well as optional commands to displace                                  from one or more 'token' files. Each record in a 'token' file con-
                      different segments of the track relative to each other in order to                                 tains a pen up/down flag; symbol type, height and color, plus
                      adjust for imperfect navigation. The adjustment process can be                                     optional text height, color and content. Although the 'token' for-
                      complicated and time consuming depending on the complexity                                         mat is bulky for some types of data (a plot boundary requires 4
                      of a survey and therefore is not routinely done on the standard                                    records), this disadvantage is outweighed by the convenience of
                      archived data. For archiving purposes, a set of plots at a scale of                                dealing with only one such format in the plot program and the
                      16 inches per degree of longitude are generated for each cruise                                    ease with which such files can be generated by scripts from other
                      leg. One set of hardcopy plots is produced for the chief scientist                                 sources.
                      and another retained at the data center. The plot files are also                                   UWPROF: The 'uwprof' program profiles u/W data versus dis-
                      stored on tape for making future hardcopy pjots,. a.procedure. that                                tance along the ship's track or versus distance projected to a
                      has proved more convenient and cost effective than regenerafing                                    specified azimuth. Ship time can be annotated along the x axis
                      the plot files each time they are requested.                                                       and multiple consecutive plots, each having a fixed distance, can

                                                                                  SIO IJ/W DATA                       PLOT DISPLAYS

                                                    U/W PLOTS                                                                                          U/W PROFILES

                                                       Mhster                                                                                                    prof
                                                     Abstracts                   token                                                                  u/w data profiles                  uwproficl'
                                                                                                                                                                                           uyy
                                  UWMrg                                          file(s)                                                                  vs. ship track                 put =cPrVmica,ds
                                   file(s)                                                                                     ct>                           uw
                                                                                                 UWPI000f                                                    distance
                                                                                             (input command
                           nzbin                       Uwplot                                        file)                                                       NIX                Hardcopy Profiles
                                                 plots tracks and/or
                             i e(s)                                                                                                                             plot
                                                 printed or profiled
                       09>                             u1w data                                                                                                file(s)              CRT
                               Alternate
                              Input files                UNI                  Hardcopy plots
                                                          plot
                                                          file                CRT

                                                                                                                  Figure 5
                             ,Tvbin@

                                                                                                               389

                      be generated for a cruise leg with one execution.

                                            7. CONCLUSIONS
                           Although the system for processing data from Scripps
                      cruises and the management of the multi-cruise data base meets
                      most current institutional requirements, there is always room for
                      improvement. Navigation needs to be upgraded from one minute
                      to one second time resolution and modified to work in the full
                      coverage GPS environment expected to be operational within the
                      next few years. Methods should to be developed to resolve the
                      present conflict between precise positioning needed for Sea
                      Beam bathymetry and smoothly varying velocities required for.
                      gravity data. User access to the multi-cruise data base would be
                      greatly improved by storing the merged data on-line on high
                      capacity optical disk.

                                         ACKNOWLEDGMENTS
                            University of California curatorial funds supported S.
                      Smith for system design, programming and implementation.
                      Financial support for much of the programming done by J. Char-
                      ters and M. Moore was provided by the Scripps Industrial Asso-
                      ciates. Many improvements in processing methods have resulted
                      from the suggestions of GDC staff members U. Albright, G.
                      Psaropulos and W. Smith. C. de Moustier critically reviewed the
                      manuscript, E. Ford formatted this paper and J. Griffith drafted
                      the illustrations.

                                              REFERENCES

                      [1] Abbott, J. L., S. M. Smith, J. S. Charters, P. G. Downes, T.
                      Hylas, R. L. Moe, J. M. Moore, and D. V. Stuber, Scripps Seago-
                      ing Computer Centers: Real-time Data Acquisition and Process-
                      ing, IEEE Proceedings 4th Working Symposium on Oceano-
                      graphic Data Systems, pp 123-129, San Diego, CA, Feb. 1986.

                      [2] Moore, J. M., J. S. Charters and C. de Moustier, Multi-
                      sensor Real-time Data Acquisition and Preprocessing at Sea,
                      Proceedings MTS-IEEE Oceans'88 Conf., Baltimore, Maryland,
                      Nov. 1988.

                      [3] Charters, J. S., SIO Sea Beam Software Documentation,
                      Shipboard Comp. Group, Scripps Inst. of Oceanography, La
                      Jolla CA, unpublished document, 1986.

                      [41 The Marine Geophysical Data Exchange Format - MGD77,
                      KGRD NO. 10, National Geophysical Data Center, Boulder, CO,
                      1917.

                                                                                          390

                                DUOMORPH SENSING FOR LABORATORY MEASUREMENT OF SHEAR MODULUS

                                                            *Samantha K. Breeding
                                                                 +Dawn Lavoie

                                               *SYNTEK Engineering & Computer Systems, Inc.
                                         +Naval Ocean Research and Development Activity - Code 363
                                                   Stennis Space Center, Mississippi 39526

                                    ABSTRACT                               the dynamic modulus of solid propellants, but
                                                                           this new technology has potential for use in
               The shear modulus of a sediment is directly                 other applications and materials. The need for
               related to shear wave velocity, an essential                an accurate laboratory method for determining
               geoacoustic parameter not easily measured in                the dynamic shear modulus of carbonate
               the laboratory. Further, both shear modulus and             sediments under varying pressures led to the
               shear wave velocity       are a function of the             application of the Duomorph technique in
               effective stress on a     sediment. The objective           sediments.
               of this research is to develop a simple
               laboratory test procedure to measure the shear              DUOMORPH SENSING AND LABORATORY METHODS
               modulus of a sediment under controlled loading
               conditions. To do this, a Duomorph has been                 The Duomorph sensor, app. 2.54 cm diameter,
               constructed similar to ones designed by Briar               consists of a thin steel plate sandwiched
               et al. (1). Compressional wave velocity has                 between two peizoceramic crystals with a
               been measured using the NORDA compressional                 metallic strain gage adhered to the center of
               wave       transducers      before      and      after      each crystal (Figure 1).         The peizoceramic
               consolidation to validate   the Duomorph results.           crystal is a low power electromechanical
               Initial results indicate     that the concept is            transducer capable of converting electrical
               feasible and continued testing is planned.                  energy to mechanical energy and vice versa.
                                                                           The application of an alternating current
                                INTRODUCTION                               across     the    individual     layers     of    the
                                                                           peizoceramic crystals causes one layer to
               The United States Navy is interested in the                 expand while the other contracts.                 The
               measurement of shear wave velocity and shear                deflection of the crystals is in a dish-shaped
               modulus of marine sediments for acoustic and                manner.
               engineering purposes. Shear wave velocity and
               shear modulus are both a function of effective                                  STRAIN GAGE
               stress.    To produce results close to in situ                                    lzz=@
               values, a laboratory procedure that reproduces
               the estimated effective stress state of the in                               WP
               situ sediment should be used, such as                       PIEZOCERAMIC           STEEL                   +
               consolidation testing.      Currently, the bender           CRYSTALS
               element shear wave transducers used by the                                     tp                           V
               Navy are only designed           to operate under
               ambient pressure. Therefore, Duomorph sensors
               designed to measure shear modulus have been                                    STRAIN GAGE
               fabricated based on ideas originated by Briar
               et al. (1).                                                     P POINTS IN THE DIRECTION OF POLARITY
               The Duomorphs as originally designed by Briar,              Fiqure 1.    Schematic of a Duomorph wired in
               et al. were used as On situ sensors to measure              parallel.

                                                                      391   United States Government work not protected by copyright

                                                                                point.    The Duomorph is then embedded in
                              zV                                                sediment and placed in a Consolidation
                                                                                chamber. As -loads are added, the consolidation
                                                                                of the sediment is noted according to standard
                                                                                procedures (2). Duomorph strain measurements
                                                                                are made after completion of consolidation
                                                                                under each load increment and used in
                                                                                calculations to determine the shear modulus of
                                                                                the sediment at each load increment.

                               scoy              T
                                                                                                     DESIGN

                                                                                Two prototypes were built, one with a .020 cm
                  Figure 2.     Photograph   from  the  oscilloscope of         thick steel plate and one with a .008 cm thick
                  the transmitted signal     to the Duomorph (top)              steel plate.     Both prototypes used 350 ohm
                  and the received signal from the Duomorph                     resistance metallic strain gages with a .152
                  (bottom) after being processed.                               cm    gage length, a .254 cm grid width, an
                                                                                overall length of .381 cm, and an overall width
                  The deflection of the Duomorph changes the                    of .254 cm.       They are an "EA" type which
                  resistance of the strain gages which are                      measures up to 5% strain.          The piezocera.mic
                  connected to a wheatstone bridge in a strain                  crystals used were a G-1278 type, fired silver
                  indicator, in a half bridge configuration.          The       with a thickness of .279 cm and a diameter of
                  dynamic output from the          strain indicator is          2.54 cm.
                  amplified,     filtered    and     passed     to     an
                  oscilloscope to obtain a         photograph of the            After the strain gages were carefully adhered
                  dynamic strain (Figure 2).          This     laboratory       to the crystals, the crystals were adhered to
                  setup is depicted in Ficlure   3.                             the steel plate forming        a    sandwich.      Thin
                  To use the Duomorph, the strain gage reading of               wires were carefully soldered to the crystals,
                  the Duomorph is obtained       in air as a reference          the steel plate, and to the tabs on the strain

                                                   AMPLIFIER                                         OSCILLOSCOPE

                                                        OUT
                                                         IN                                                     CH 1   CH2
                                                                                                                 f
                                                                         DYNAMIC
                             CONSOLIDATION                               0U-rPU'r              RECEIVED SIGNAL
                             TEST                                                I
                                                                     STRAIN
                                                                     INDICATOR
                                                                     P- S+ S_ (B                  our
                                              J DLIOMORPH                                          IN   FILTER

                                    GROUNDEDON                                             WAVETEK
                                    SHIELDED
                                    CABLE                                                    OUTPUT

                                                                                      TRANSMIFIFTED SIGNAL
                                   Fiqure 3.     Diagram of the laboratory setup for obtaining the dynamic
                         2v\i-

                                  strain from the Duomorph.

                                                                           392

                 gages.     This configuration constitutes the                  where:
                 instrument called a Duomorph. The Duomorph
                 was then   coated with a combination of Resin                  a is the radius of the -Duomorph, and
                 184 and    186 to protect the     'wires and gages             D    is the disk flexural rigidity,
                 from moisture when embedded in sediment.

                        DATA REDUCTION OF DUOMORPH DATA                                            hm 3 (EM - E,) + Eh3             (5)
                                                                                           D
                 Reduction of the      Duomorph data follows          the                             12 (1 - v2)
                 method devi  sed by Briar et al. (1). The wave
                 form displayed on the oscilloscope represents
                 the amount of dynamic strain detected by the                   where: v is Poisson's ratio for the Duomorph
                 strain gages.      This strain was used in the                 (v =.495 for the Duomorphs used in this
                 following equation to determine the modified                   research).
                 moment ratio:
                                                                                The shear modulus, G, is calculated from (5):

                              Mc          (e/ea)    k,              (1)                                  E'                         (6)
                                                                                              G
                              Mo            1   k                                                     2 (1 + v)

                 Where:                                                         The shear wave velocity, Vs, is calculated
                                                                                from (4):
                 e   is the strain in sediment under a     load,                                               -1/2                 (7)
                 ea  is the strain in air, and                                                Vs = [G
                 k'  is a constant dependent on disk        design (for
                 the Duomorph with a .020 cm steel plate, k
                 -.664)

                                                                                  METHOD USED TO CHECK DUOMORPH RESULTS

                 1      1 - 3phz(hz + hm) (2 + Emhm/Ezhz)           (2)         The values of shear moduli calculated from the
                                                                                Duomorph data are compared to values obtained
                 k        h2 [1 + (Em/Ez - 1) (hm/h)3                           from a standard method of determining shear
                                                                                modulus to check the validity of the Duomorph
                                                                                results (4).
                 where:
                                                                                The standard method used to determine the
                 hz is  the thickness of    the PZT crystals,                   shear     modulus       of  a   sediment       involves
                 hm is  the thickness of    the steel plate,                    measuring the compressional wave velocity
                 Ez is the tensile modulus of the PZT crystals,                 before      and     after   consolidation.          The
                                                                                compressional      wave velocity can then be
                 Em is the tensile modulus of the steel plate,                  interpolated for intermediate load increments.
                 h is the thickness of the entire sandwich, and                 The specific gravity is determined by a
                                                                                weight/volume technique (3).                From the
                                                                                specific gravity, the dry density can be
                                     (1/2) (1 + hm/hz).             (3)         calculated,       assuming      a   fully     saturated
                                                                                condition.        After a sample           has      been
                 The modified moment ratios are used to                         consolidated (2), the results of the void ratio
                 determine the modulus,     IM, from a nomograph                versus log of effective stress graph are used
                 generated from quasi-static analysis (1).          The         to    calculate       av,   the     coeffiecient       of
                 elastic modulus, E', is calculated by the                      compressibility,      for each      load     increment
                 following equation:                                            (Figure 4):
                                     E' = M D     a3,               (4)   393                         av = Ae / Ap,                 (10)

                                                                               4.6e+6.

                                                                            CM
                                                                            X  4.4e+6 -
                                                                            z
                                                                                              CALCULATED
                     -0.9-                                                  u) 4.2e+6 -
                   0                                                                         SHEAR MODULUS
                      0.8
                                                                            D  4.0e+6
                   Q  0.7                                                   0
                                                                               3.8e+6 -
                   0  06-
                   >
                                                                                                                DI )OMORPH
                      0.5-                                                  W  3.6e+6
                                                                            X                                     DATA
                                                                            Cl)
                      0.4-                                                              1                                     i
                                                                               3.4e+6
                                 1       10     100    1000   10000                    10         100           1000       10000
                          VERTICAL EFFECTIVE STRESS (kPa)                               VERTICAL EFFECTIVE STRESS (kPa)
                Figure 4.    The void ratio versus log of vertical          Fiqure 5.    Graph of shear modulus obtained
                effective    stress     curve    generated       from       from Duomorph experiment compared to shear
                consolidation data.                                         modulus calculated from a standard method.

                where:                                                      where:

                Ae is the change in the void ratio between two              G is the shear modulus,
                load increment, and                                         p is the dry density,
                Ap is the change in the pressure between two                VP is the compressional wave velocity at a
                load increment.                                             load, and
                                                                            K is the bulk modulus.
                The bulk modulus, K, is calculated from av and
                the initial void ratio, eo (2,4).                                               RESULTS

                              1C= av          + eo)                         The shear moduli determined from the
                                                                            measured Duomorph data and the shear moduli
                The shear modulus, G,       is calculated from (5):         calculated from the standard method using p,
                                                                            V    and K are graphed versus the vertical
                              G = (p V      2 - K    3/4),       (12)          p
                                          p                                 effective stress in Figure 5.       The values from

                                 Table 1.     Listing of values calculated from consolidation test and
                                 compressional wave transducer, tests.

                                   P             e            av            1C          Vp           G
                                   kN/m2                      1 /kN/m2      1 /kN/m2    m/s          N/m2

                                         0.0    1.0398        -             -           1629         -
                                       17.1      .9808        3.45E-3       1.69E-3     1630         3,730,000
                                      51 .4      .9528        8.15E-4       4.OOE-4     1632         3,740,000
                                      119.9      .9093        6.36E-4       3.12E-4     1637         3,770,000
                                      257.0      .8584        3.71 E-4      1.82E-4     1646         3,810,000
                                      531.2      .7941        2.35E-4       1.15E-4     1'666        3,900,000
                                   1079.0        .7197        1.36E-4       6.65E-5     1704         4,080,000
                                   2175.0        .6264        8.52E-5       4.18E-5     1781         4,460,000
                                   4605.0        .4892        4.89E-5       2.39E-5     1951         5,350,000

                                                                       394

                              Table 2.    Shear wave velocities calculated using the shear modulus
                              from the Duomorph data and the standard method.

                                Standard Method           Duomorph Technique        Percent Difference
                                   G           Vs              G          VS          G        Vs
                                (N/m2)         (m/s)        (Nlm2)     (m/s)          %        %

                              3,740,000        44.6       3,630,000    44.0           2.7      1.4
                              .3,750,000       44.7       3,630,000    44.0           3.0      1.5
                              3,770,000        44.8       3,590,000    43.8           4.8      2.5
                              3,820,000        45.1       3,630,000    44.0           4.7      2.4
                              3,900,000        45.6       3,810,000    45.1           2.3      1.1
                              4,090,000        46.7       3,790,000    45.0           7.2      3.7
                              4,460,000        48.8       4,190,000    47.0           7.5      3.8

              -the consolidation test and      the  compressional      modulus and shear wave velocities                of
              wave     velocity  tests   that  were    used    to      sediments under effective stresses of interest
              calculate the shear moduli using the standard            to geotechnical engineers.     The advantage of
              method are listed in Table 1. The shear wave             the Duomorph sensor is that it can be placed
              velocities calculated using the shear moduli             directly into a consolidation test, whereas, the
              from both methods are listed in Table 2.                 NORDA bender element transducers for
                                                                       measuring     compressional and shear wave
                                                                       velocity are limited to testing samples before
                                  DISCUSSION                           and after consolidation testing.

              The values of shear modulus and shear wave
              velocity determined from         the Duomorph                              ACKNOWLEDGMENTS
              experiment are within 2.3% to 7.5% and 1.2% to
              3.8%, respectively, of the values calculated             This project was supported by Naval Ocean
              from the standard method. The Duomorph data              Research and Development Activity funding at
              has    slight   fluctuations     in   the     data.      Stennis    Space Center,       Mississippi.    The
              Fluctuations occur because       the strain wave         contribution of Messrs David Young who built
              from the oscilloscope isn't      always a stable         the Duomorphs and John Burns who provided
              wave; sometimes, it has          a tendency to           electronics       support       is     gratefully
              fluctuate due to background      laboratory noise.       acknowledged.
              The camera speed was set to      1/15 of a second
              in attempt to capture a clear wave. In spite of
              the fast shutter speed, the signal photographed                            REFERENCES
              was not always at the same point of
              fluctuation;    and,    therefore,    the   strain       (1) Briar, Herman P., Bills, Kenneth W., and
              measurements varied       slightly.                      Schapery, Richard A., "Design and Test of the
                                                                       Operational In-Situ Gage for Solid Propellant
                                                                       Surveillance",    Air Force Rocket Propulsion
                                 CONCLUSIONS                           Laboratory, 1976.
                                                                       (2) Bowles, Joseph E., Engineering Properties
              The values of shear modulus      and shear wave          of Soils and Their Measurement, McGraw Hill
              velocity obtained from the Duomorph technique            Book Company, third edition, 1986, pp.
              are within the range of values determined from           107-128.
              the compressional and shear wave velocity                (3) Lambe, T. William, Soil Testing for
              techniques. Therefore, Duomorph sensing                  Enaineera, John Wiley & Sons, Inc., 1951,
              provides a valid method of determining shear             p.15-21.

                                                                  395

                (4) Hamilton, Edwin L., "Elastic Properties of     (5) . Timoshenko, S., and Goodier, J. N., Theor
                Marine Sediments", Journal of Geophysical          of Eta       McGraw Hill Book Company, Inc.,
                Research, Vol. 76, No. 2, January 10, 1971, p.
                581.                                               1951, p. 9.

                                                              396

                             THE USE OF A TOWED, DIRECT-CURRENT, ELECTRICAL RESISTIVITY ARRAY FOR THE
                                                       CLASSIFICATION OF MARINE SEDIMENTS
                                                                         Dawn Lavoie
                                                                        Edward Mozley
                                                                        *Robert Corwin
                                                                       Douglas Lambert
                                                                         Philip Valent
                                                     NORDA, STENNIS SPACE CENTER, MS 39529
                                                        *409 Sea View Drive, El Cerrito, CA 94530
                                         ABSTRACT                                     A prototype, direct-current (DC), electrical resistivity
                                                                                      array which can be towed in the marine environment
                                                                                      was fabricated and field tested in the Mississippi
                        The direct-current (DC) electrical resistivity                Sound in the fall of 1987. RASCL acoustic data were
                 method has been used for a variety of offshore                       collected concurrently for comparison of the two
                 geophysical, geotechnical investigations.             Model          techniques. Ground truth data were acquired using a
                 studies indicate that the DC technique is feasible for               conductivity, temperature, and depth (CTD) profiler
                 sediment classification and layer structuring. A                     for water column measurement and a hydroplastic
                 prototype array was built to test the hypothesis that                gravity corer and vibrocorer for sediment sampling.
                 such a technique can be used while in an underway                    The purpose of this paper is to describe the DC array
                 mode in the marine environment. A 60 m, inverted                     and the results of the field trials in the Mississippi
                 Schlumberger array was towed both on and off the                     Sound.
                 seafloor with electrode spacings appropriate for a
                 penetration depth of 10 m below the seafloor. Three                                       BACKGROUND
                 different bottom types, mud, gassy mud, and sand,
                 were surveyed in the Mississippi Sound using the                     Electrical resistivity, the reciprocal of conductivity, is a
                 array. Ground truth was provided with an acoustic                    measure of the ability of a solution, solid or mixture to
                 seafloor classification system, CTD casts, and                       resist the flow of electric current (2).           In most
                 numerous sediment cores.           Data were analyzed                sediments, the porosity and salinity of the pore fluids
                 using SUBVERT, a modification of a University of                     is more important in determining the resistivity than
                 California, Berkeley, inversion routine adapted for                  the mineral grains comprising the sediment. The
                 an IBM-PC AT. Both the layering structure of the                     seawater pore fluid of marine sediments provides the
                 upper sediment and lateral variability of sediment                   ideal medium for the conduction of electric current
                 types were adequately defined by the DC technique.                   With the resistance of the formation inversely related
                                                                                      to the porosity and degree of saturation (3).

                                     INTRODUCTION                                     Archie (4) established a quantitative relationship
                                                                                      between the porosity and electrical resistivity of a
                 The United States Navy is interested in the problem                  sandstone. He defined formation factor (F) as the
                 of remotely classifying and characterizing sediments                 ratio of the resistivity of the saturated sandstone to
                 in terms of their physical properties from an                        the resistivity of the pore fluid
                 underway platform.         Two basic techniques are                                         F = ps / pw,                       (1)
                 presently under development, acoustic and
                 electrical. The acoustic technique has been used                     where ps is the resistivity of the sandstone and pw is
                 successfully in a number of areas using the NORDA
                 Remote Acoustic Seafloor Classifier (RASCL) (1).                     the resistivity of the pore fluid.         From this, he
                 However, acoustic penetration is limited in regions                  established the relationship between formation factor
                 where gassy sediments predominate or where highly                    and porosity
                 reflective sediments overly "less reflective"
                 sediments. In addition, the RASCL acoustic system                                           F = 0-m,                           (2)
                 requires at least 3 m of water below the transducer; it
                 is not effective in shallow-water, nearshore                         where 0 is the effective porosity and m is a constant
                 environments. These bottom environments, which                       that represents the slope of the line depicting the
                 occur often on continental shelves, prove to be                      relationship between F and 0 when plotted on log-log
                 amenable to investigation by direct-current, electrical              paper (4). Subsequent workers (5, 6, and 2), have
                 resistivity technique. In other shelf environments with              found that the form of Archie's equation
                 greater than 3 m of water the two systems provide
                 complementary seafloor information.                                                         F = ao -m,                         (3)

                                                                               397 United States Government work not protected by copyright

                  where a and m are constants related to sediment type                               MISSISSIPPI SOUND EX  PERIMENT
                  with values close to 1 and 2 respectively, results in
                  predicted porosities close to experimentally measured
                  porosities for terrigenous, consolidated and relatively
                  low porosity rocks with low clay content.
                                                                                            RASCL               I I   M  1 2 1 A B 1'2 3 N
                                                                                                                              V V X.,
                  Because marine sediments generally have lower                         LAYER 1                       54                4 1  1 7
                                                                                        LAYER 2'.'*.*
                  porosities and pore fluids of higher salinity than
                  terrigenous sediments, formation factors and absolute                @@YER I
                  resistivities are generally lower in marine sediments
                  than for similar sediments on land.               Measured            BASEMENT         INVERTED SCHLUMBERGER ARRAY
                                                                                                     ELECTRODE SPACINGS: (m) GROUND TRUTH:
                  resistivities for marine clays, silts and sands overlap to                         M1N1  3.0        COPIES
                  some degree; thus there is no unique relationship                                  M2N2  4.4        SUBBOTTOM
                                                                                                     M3N3  6.4         CLASSIFIER
                  between sediment resistivity and sediment type (3).                                M4N4  9.4        Cm
                  However, given a reference point in a known bottom                                 M5N5  13.7
                                                                                                     M6N6  2GO
                  type, changes in sediment type are identifiable and                                M7N7  29.4
                  can be predicted from measured resistivity.                                        AB/2  0.4
                  In this study, no attempt was made to determine                     Figure 1.      Illustration of the configuration of the
                  unique values for a and -m to calculate porosity values             towed, inverted Schlumberger array used to
                  for sediments within the Mississippi Sound. Instead,                measure sediment resistivity in the Mississippi
                  initial porosity calculations made from measured                    Sound.
                  apparent resistivities are based on the formula
                                            1.2 F -.69                       (4)      re.lieve the connecting wires of towing stress and
                                                                                      minimize cable stretch.
                  It was developed by Boyce (6) as a generic form of
                  Archie's Law and is based on porosities measured           on       The current transmitter system included an AC power
                  sediments from the Bering Sea with a composition                    source, a power supply and control unit and a switch.
                  similar to much of the sediment in the Mississippi                  The AC power source was a 6 kW gasoline-powered
                  Sound.                                                              generator that provided 110 VAC output. The power
                                                                                      supply and control unit included a Variac variable
                                                                                      transformer, a voltage multiplier circuit that stepped up
                                   ARRAY DESCRIPTION                                  the input voltage to a maximum of about 800 VAC and
                                                                                      a rectifier circuit that transformed the AC voltage to DC.
                  The prototype DC system included an electrode cable,                Maximum output of the unit was 800 VDC or 4 amps
                  a current transmitter, and a data acquisition system.               DC or 2 kW, whichever was reached first.
                  Modeling results of an earlier study indicated that the
                  electrode cable in an inverted Schlumberger                         The DC output of the control unit was fed into a
                  configuration could be used to resolve subseafloor                  normally open, high capacity, manually operated
                  layers and sediment properties to a depth about 1/3 to              double pole, double-throw, switch that was used to
                  1/4 the array length with a resolution of about 1 m (3).            reverse the polarity of the DC current output to the
                  Since the longest vibrocore that could be recovered                 current electrodes.
                  was 3 m, the array length was constructed so that the
                  maximum electrode spacing was less than 30 m                        Output current, electrode potential and pressure
                  (Figure 1). The electrode cable consisted of one pair               transducer output were measured with liquid-crystal
                  of current electrodes for transmitting electrical current           display (LCD) digital multimeters (Beckman Industrial
                  into the sea water and seven pairs of potential                     model DM800). Resolution on the 200MV range was
                  electrodes for measuring voltages generated by this                 10 microvolts and accuracy was +/- 0.05% of the
                  current. The electrodes were arranged in an inverted                measured value. Current measurements were made
                  Schlumberger array. The distance AB/2 from the array                in the 10A range, with a resolution of 1 mA and
                  center to the center of each current electrode was 0.4              accuracy of +/- 0.75% of the measured value. Data
                  m.    The corresponding distances, MN/2, for the                    rate was 2 points per second.
                  potential electrodes were 1.5, 2.2, 3.2 4.7, 6.85, 10.0
                  and 14.7 meters from the array center to the outer tip of
                  each electrode. This roughly logarithmic electrode
                  spacing resulted in equally spaced data points on the                                    FIELD METHODS
                  log log plots used for data interpretation. The cable
                  also included a pressure transducer so that standoff                The field platform was the FIN KIT JONES , a 20-m,
                  distance from the seafloor could be determined.                     wooden hull, diesel powered vessel. The resistivity
                                                                                      array was towed directly behind the ship with the
                  The cable jacket was abrasion resistant polyurethane                center of the array approximately 65 m behind the
                  plastic. A kevlar stress member was incorporated to                 center of  the ship. This towing configuration allowed
                                                                                       7YER MlCL'@@

                                                                                398

                 the cable to be towed     along the seafloor in shallow          data, it is relatively easy for an experienced interpreter
                 water, and within 2 m of the seafloor in water over 6 or         to roughly estimate layer parameters by inspection of
                 7 m deep.                                                        the plot of apparent resistivity vs. electrode separation;
                                                                                  however, for seafloor resistivity data, the presence of
                 In addition to the resistivity system, ancillary equipment       the overlying water makes it much more difficult to
                 included LORAN C navigation (Internav) , a CTD                   obtain such initial estimates by inspection of the field
                 system (SeaBird Electronics, Seattle, WA.), RASCL                data curve. Because such estimates are required for
                 subbottom classifier (Honeywell ELAC, Kiel, FRG.) for            input to the inversion routine used, an empirical
                 acoustic measurements and a vibrocorer for bottom                stripping procedure was devised for removing the
                 sampling.     Both LORAN systems were checked                    effect of the water layer and transforming the seafloor
                 Foritinuously to verify the ship's position. The RASCL           apparent resistivity readings to those which would
                 is a high resolution seismic system which has the                have been observed had the water layer not been
                 capability to measure echo strength both quantitatively          present. The basis for this process is the assumption
                 and qualitatively in ten time windows.           For this        that the seafloor and the sea water act as resistors in
                 experiment, the system used a 15 kHz transducer and              parallel, so that the measured apparent resistivity is
                 was adjusted so that each time window corresponded               equivalent to the parallel combination of the seafloor
                 to a sediment depth increment of 0.4 m. The system               and sea water apparent resistivities.          Since the
                 applies algorithms based on multilayer acoustic theory           apparent resistivity of the water layer can be calculated
                 to compute acoustic impedance for the ten depth                  from its known resistivity and thickness, the "stripped"
                 increments in the seafloor. This impedance profile is            seafloor resistivity values are easily calculated. (7). An
                 then used to predict sediment structure and various              inversion routine, SUBVERT, is used to determine the
                 physical properties including porosity (1). The CTD              layered structure corresponding to a given set of
                 data and cores were used for ground truth both to                resistivity values for Schlumberger and Wenner
                 calibrate the RASCL and compare with the direct                  expander arrays. The primary limitation of SUBVERT
                 current interpretations.                                         is that a maximum of four layers can be resolved. This
                                                                                  usually includes the water layer above the array, one
                                                                                  or two subbottom layers, and an infinite half space
                      DATA REDUCTION AND INTERPRETATION                           basement.

                 Several computer programs written at the University of
                 California, Berkeley, have been used to reduce the                                   FIELD RESULTS
                 measured field data (7). SUBRED is used to calculate
                 apparent resistivity values from measured field data for         Three test sites in the Mississippi Sound were chosen
                 each potential electrode pair. For onshore resistivity           for their differing bottom types (Figure 2). Results from

                                           05'               890              55'              50'               45'

                                                                                  BILOXI

                                         GULFPOFTr
                                                       t
                                                       N
                                                                                       DEER ISLAND SITE
                                     20'                                               (SANDY CLAY)

                                                             MISSISSIPPI                           SOUNO

                                     15'
                                                                                                          loc.

                                                                                                     HORN ISLAND SITE
                                                   .2   .8  TIRIANGLE                                (MED. SAND)
                                                     .7    (GASSY MUD)
                                  30c10' i        _____j

                                        Figure 2. Location map of the sites surveyed in the Mississippi Sound.

                                                                             399

                                                                                                                   STATION 6

                                                                                                                   % (by weight)
                                                                                                   0       10      20        30     40      50

                                                                                                0
                                                        U

                                                   5
                                                   Z
                                                                                             -762

                                             A
                                             4    j",
                                                   -P
                                                                                          U)
                                                                                          E

                                                   A

                                                          . . ...                            -1.73

                    Figure  3.  RASCL record of       Station  6 with several
                    subbottom    reflectors within 4  mbsf.   Note flat echo
                    strength lines indicating the system had "pegged out"                    -2.62
                    due to shallow water depths.

                    three stations within the Deer island and Horn Island                                            Coarse sand
                    sites are reported here. Results from the Triangle will                                          Medium sand
                    be presented in a later paper.                                                                 In Fine sand
                                                                                                                   0 v. fine sand
                    The Deer Island site is a shallow water, sandy-mud                                             0 silt
                    bottom environment. The offshore barrier islands,                                              10 clay
                    including Horn Island, in the Mississippi Sound are
                    migrating westward over a mud bottom. The Horn                      Figure  4.     Results     from five discrete grain size
                    Island Site was chosen because bottom sediments                     analyses, Station 6, Deer Island, Mississippi Sound.
                    were expected to be sands to an unknown depth, and
                    it was hoped that the resistivity array would delineate a
                    less reflective layer below the surface sediments.                  A comparison of core       and array results is presented in
                                                                                        Figure 5 as porosity       plotted against depth in meters
                    Station 6, 3.5 krn south of the western end of         Deer         below the seafloor mbsf.
                    Island (Figure. 2), is known from core analyses       to be         Station 9 is located within the Horn Island site (Figure
                    fairly representative of the Deer Island stations. Water            2). Water depth (CTD) was 7.3 m. The RASCL
                    depth is known from CTD casts to be 2.9 m and the                   analog. record shows good acoustic penetration, about
                    sea floor is relatively flat, as can been seen from the
                    RASCL profiles (Figure 3). Because the water depth
                    was less than the required 3 m below the transducer,                                 TABLE 1: STATION 6
                    the amplitude of the echo strength returns was                      --------------------------------- --------------------------------------
                    clipped." RASCL was unable to compute an accurate                                layer         Pa      z       F
                    acoustic impedance and thus not able to predict
                    sediment type or porosity at this station.         Avisual                               (ohm-m)      (m)             W
                    description of the core indicates the sediment to be a
                    dark grey, organic, sandy mud that is fairly
                    homogeneous down hole. Grain size analyses done                     Underway:        1         0.659  0.44     2.56     62.69
                    at five discrete intervals down the core are presented                               2         0.487  4.04     1.89     77.25
                    in Figure 4 and indicated sandy clay at the surface,                                 3         2.300  -        8.54     27.32
                    and clayey sand to fine sand below.
                                                                                        Stationa[y@      1         0.665  0.52     2.64     61.43
                    A listing of apparent resistivity values (Pa) and layer                              2         0.482  4.08     1.91     76.70
                    thicknesses (z) derived from SUBVERT, formation                                      3         2.150  -        8.53     27.43
                    factors (F), and porosities calculated using Boyce's (6)
                    formula for resistivity data acquired while underway
                    and stationary is presented in Table 1.                             --------------------------------------------------------------------------

                                                                                  400

                                TABLE'2: STATION 9                                                      STATION 6

                ------------------------------------------------------------------------
                                                                                      0-
                             law        Pei     z        E      0
                                        (ohm-m)          (M)     M                   -1
                Underway:       1       0.212   1.310                                       core measurements
                                2       0.739@  0.642:,. 3.47   50.83                  2-
                                3       1.000   -        4.74   41.03
                                                                                 E
                Stationa[y:     1       0.651   0.537    2."89'. 57.73                -3-
                                2       0.725   5.79     3.22   53.60                      underway
                                3       1.050   -        4.66   41.47                                        .4-- stationary
                                                                                      -4-

                ---------------------------------------------------------------------  -5-

                                                                                     -6
                4 m, into a fairly "soft" bottom with a( dipping reflector at          20      30      40      50      60      70       80
                about 2 meters below sea floor mW (Figure 6). This                                         Porosity (%)
                location is assumed to be a fill channel. Echo strength
                return indicates the sediments to be silty sand over a           Figure 5. Values of porosity measured from       Core 6
                fine sand. Actual grain size distribution for three              and calculated for underway and stationary resistivity
                discrete samples is presented in Figure 7. Table 2 lists         measurements, plotted against depth in meters
                apparent resistivities (Pa in ohm-m), layer depths in rn         below the seafloor.
                (z), formation factors (F), and calculated porosities (0)
                in percent using Boyce's formula (6). A compadson of
                RASCL interpreted porosities, array interpreted                                                    . . . . . .
                porosities, and measured porosities from the Station 6                                                            0
                                                                                                                            OvtF  0,
                core are presented in Figure 8.

                Station 10B is located within   the Horn Island site but
                away from the channel filled area of Station 9. Station
                10B is located on a sloping bottom in 9.54 rn of water.
                RASCL penetration is 2 m or less and echo strength
                returns indicate a "harder" or more reflective bottom
                than Station 9 (Figure 9).               RASCL bottom
                characterization is a silty sand over a finfe sand.
                Vibrocore recovery was poor with about 0.6 mi of very
                clean, medium sand retrieved. Laboratory measured
                porosity, RASCL porosities, and underway and
                stationary array calculated porosities are compared in                                                            "41 4
                Figure 10. The data from which DC porosity was
                calculated are presented in Table 3.

                                TABLE 3: STATION         11013
                 ------------------------------------------------------------------------ Figure 6. RASCL record of Station 9. Penetration is
                                19=     Pa        z      F        0               about 4 mbsf. Echo strength return indicates a "soft"
                                        (ohm-m)          (M)      M               bottom with a dipping reflector at about 2 mbsf.

                 Underway:      1       .216      9.10   water
                                2       .243      0.43                                                 DISCUSSION
                                3       .832             3.85     47.32
                                                                                 Station 6 was an ideal site to test the DC array
                 Stationary:    1       .227      10.2   water                   because the water was shallow, the array stayed on
                                2       .847      00     3.73     48.37          the seafloor, andAhe water-sediment interface and
                                                                                 subbottom layering structure were fairly horizontal.
                 ------------------------------------------------------------------------- The RASCL record indicates subbottom reflectors at
                                                                                             ore  easuremen
                                                                                                 m           ts

                                                                                             derway
                                                                                                             4-- stationary

                                                                            401

                                          STATION 9                                   approximately 1, 2, and 3 mbsf. The existence of these
                                         % (by weight)                                layers is substantiated by core analyses. Porosity
                                  0      20     40     60     80                      measurements generally increase to about I mbsf,
                                                                                      decrease from 1 to 2.5 mbsf and then increase to the
                                                                                      bottom of the core at 3 mbsf. Porosity interpreted from
                                                                                      array data suggests an increase in porosity between
                                                                                      the surface and 1 mbsf, then a layer of lower porosity
                             .127                                                     to about 4 mbsf. Underway and stationary data are
                                                                                      both good at this site. The number of layers that can
                                                                                      be resolved are limited by the inversion software to
                                                                                      four. Because these constraints exist, information
                            U)
                            M                                                         below 1 rn has been averaged to provide the
                            E                                                         interpretation of a surface layer to 1 mbsf, a deeper
                                                                                      layer of higher porosity than the surface layer, and
                            CL .94
                            CD                                                        then a basement layer of much lower porosity than
                                                                                      either of the upper layers.

                                                                                      Data from station 9 presented some difficulties in
                                                                                      interpretation of the underway data because the array
                                                                                      was off the bottom. The final inversion of data resolved
                             1.57                                                     the water into two layers, 7.03 m and 1.31 m, the array
                                                                                      presumably riding 1.3 m off the bottom. Again with the
                                                                                      software limitations, only two sediment layers were
                                                                                      able to be resolved: a surface layer of about 0.6 m of
                                                                                      sediment of 50% porosity and a basement layer of
                                         M coarse sand                                unknown thickness of 43% porosity. Stationary data
                                         0 medium sand-                               provided more resolution of the subbottom since the
                                         IM fine sand                                 array was actually lying on the bottom. However,
                                         * very fine sand                             interpreted values of resistivity and porosity were
                                         * silt                                       significantly higher than core, RASCL, or underway
                                      I M  clay                                       interpretations (Figure 8). Stationary data was taken
                                                                                      with the ship rolling at anchor. Generally the signal to
                     Figure 7. Results of grain size analyses from three              noise ratio and data quality was poor under these
                     discrete samples from core 9. Depth is in meters                 conditions leading to less reliable interpretations.
                     below the seafloor. Legend indicates grain size.

                                              STATION 9                                                                               0
                                                                                                                              -n
                                                                                                                                  '2
                            Underway array 1.3m                                                              4e,
                            f bollo *aler
                                m;
                            resolved Into 2
                            layers:
                                                             CTD
                            rho          -M     (U)
                                  .2249  ohm
                            o 2   2119  ohm-m   7.03M  7.32M 7.3m                                                                  4

                                                                                                                                              2.

                                                1.31m     V     V seaflo,,
                                                                                                          :A       el,@7 @-,@OA
                               Depth     Co.
                               (mbst)
                                      RASCLV (U) (S)
                                                                                      11         71111 11, 11

                                                                                      V

                                    10                                                                                                  W
                                     30    40     60    so     70
                                                                                                                             _77
                                                Porosity         (nol to scale)                                       77777- 77-

                     Figure 8.    A  comparison of RASCL           interpreted         Figure 9.  RASCL record from Station 10B.       Note that
                     porosities, measured core porosities, and underway                echo strength return indicates a more           reflective
                     and stationary array interpreted porosities.                      bottom than at Station 9. Penetration is only about 2
                     Underway data indicates stand off distance from the               mbsf at Station 10B.
                     bottom.
                                  OEM

                                              7(u)

                                                                                 402

                                                                                 Schlumberger array was able to retrieve resistivity
                                                                                 data of sufficient quality to resolve water depth and
                                        Station 10B                              gross layering structure within the subbottom. The
                                                                                 resolution and bottom layering structure is limited by
                                                     I Sea surface               the inversion software used, not by the DC array or
                                                       undmy army 1.14 rn        configuration.
                            depth               10.2m  off t@ottorn; water
                            We'*,                (S)   resolved Inlo 2 layers:
                            W         9.54M 8.38m        hO@21)):.216 Ohm-nn     Array data can give resistivity values which can be
                                                         ;ho .243 ohm-nn         converted to formation factors that accurately indicate
                                                                                 different sediment types. It is necessary to make a
                                                                                 judgement call and use formulas relating formation
                           Wth       _DJ                      SeAfloor           factor and porosity for particular sediment types. A
                           (mbso A2                                              general, non-unique formula such as the Boyce
                                    C re 4!@L) 1
                               @.3 (33,9%,@ (35%1S                               formula will lead to increasingly large errors as
                                         .4      13.4
                               4.4          %       MSCL (54%)                   sediment types grade into medium sands with little
                               0.5,                                              clay or silt content.
                               0.67@  30   40    50   60   70                    It is evident that it is not necessary to take stationary
                                          Porosity (%)        (not to wale)      data since the underway data are as good or better
                                                                                 than 1he stationary data. This is possibly because the
                                                                                 ship rolled considerably while at anchor and the signal
                                                                                 to noise ratio was higher than while underway.
                Figure 10. A comparison of         RASCL interpreted
                porosity, core measured porosities, and underway                 The towed array is ideally suited for shallow water use;
                and stationary array interpreted porosities. The array           with a thinner water layer to resolve, resolution within
                Was off the bottom while underway; the water is                  the subbottom becomes better.        The DC resistivity
                resolved into 2 layers.                                          technique provides valuable complementary data
                                                                                 when used in conjunction with an acoustic
                                                                                 classification system.
               The interpretation of array data from Station 10B was
               frought with similar problems because the array was
               not only off the bottom, but the bottom was sloping,                              ACKNOWLEDGMENTS
               thus the array was not parallel to the bottom. With the
               water resolved into two layers equalling 9.54 m of
               water, the same water depth as measured by CTD, the               Support for this study was provided by the Office of
               underway array data provided us with bottom                       Naval Technology, Oceanographic Support Block,
               formation factors of 3.85, very close to those reported           Project RM35685. The authors wish to thank the crew
               by other workers for sands (8). Similarly, with the               of the R/V Kit Jones for field support and Frank
               stationary data,     a formation factor of 3.73 was               Carnaggio and John Burns of NORDA for excellent
               calculated. Using the Boyce formula, porosities of                electronics support.
               47% and 48% were calculated, considerably different
               from measured core porosities.         Using a formula
               derived by Beyer (8) for quartz sands, F = 0-1.26,                                    REFERENCES
               porosities of 34.5% and 35% are calculated for the
               Station 10 sediments. It is therefore important to                1 . Lambert, D.M.: "A New Computerized Single
               realize that formation factors are indicative of sediment         Frequency. Seaf loor Classification System", in: Current
               type. Appropriate formulas relating porosity to                   Practices and New Technology in Ocean Engineering,
               formation factor for particular types of sediment must            eds. G.K. Wolfe, and P.Y. Chang, ASME, 1988, pp 99-
               be used.        RASCL-interpreted porosities are                  105.  .
               considerably different from measured porosities. The              2. Erchul, R.A.: "The Use of Electrical Resistivity to
               correlation factor used in RASCL algorithms to                    Determine Porosity of Marine Sediments", Ph.D.
               correlate acoustic impedance and porosity is not as               Dissertation, University of Rhode Island, Kingstown, Rl,
               well defined for clean sands as for sediments                     1972, 86 p.
               containing significant amounts of silt and clay.
                                                                                 3. Valent, P.J., E.D. Mozley, and R. F. Corwin, "Rapid
                                                                                 Underway Sediment Classification by Electrical
                                                                                 Methods", NORDA Report 211, Stennis Space
                                   CONCLUSIONS                                   Center, MS, 39529, 1987, 72 p.
                                                                                 4. Archie, G.E.: "The Electrical Resistivity Log as an
               The use of a towed, DC array to delineate subbottom               Aid in Determining some Reservoir Characteristics":
               layering and characterize sediment is highly feasible             Am. Inst. Mining Metall. Petroleum Engineers Trans.,
               in the marine environment.               The inverted             v. 146,1942, pp 350-366.

                                                                           403

                   5. Winsauer, W.O. and McCardell, W.M.: "Ionic                 7. Corwin, R. F.: "Model Study and Computer
                   Double-Layer Conductivity in Reservoir Rock": Am.             Programs for Modeling and Interpretation of Seafloor
                   Inst. Mining Metal[. Petroleum Engineers Trans., v            Direct-Current Electrical Resistivity, Measurements",
                   198, 1953, pp 129-134.                                        prepared under Contract No. N00014-87-C-6012,
                                                                                 NORDA, Stennis Space Center, MS, 39529, 1987,
                   6. Boyce, R.E.: "Electrical Resistivity of Modern             104 p.
                   Marine Sediments from the Bering Sea",          Ph.D.         5. Beyer, J.H.: Unpublished report retained by R.F.
                   Dissertation, San Diego State College, San Diego,             Corwin, 406 Sea View Drive, El Cerrito, CA, 94530,
                   CA, 1967,172 p.                                               1971.

                                                                          404

                                              SEDIMENT CONTAMINATION BY HEAVY METALS AND HYDROCARBONS

                                                             P.F. WAINWRIGHT', B. HUMPHREY2, G. STEWART3

                                             1. Seakem Oceanography Ltd. P.O. Box 2219,2045 Mills Rd., Sidney, B.C., V8L 3S I
                                                        2. Seakem Oceanography Ltd., 28 Block C, St. Michael, Barbados
                                             3. Canada Department of Indian and Northern Development, Yellowknife, N.W.T.

                                                                                                 monitoring programs may suffer from changes in design
                                               ABSTRACT                                          or inconsistencies in sampling and analytical methods.
                 Results of the analysis of contaminant data from marine sediments at            Complex statistical procedures may be required and
                 exploration shoTebases collected between 1982 to 1984 by the Beaufort           specific hypotheses of concern may not be testable. To
                 Sea Shorebase Monitoring Program are presented here. Analyses                   facilitate use by regulators, it is desirable that statistical
                 determined that the dataset was not suitable for conventional statistical       analysis of monitoring results be robust but easily
                 methods and that inter-laboratory variance was confounded with                  interpreted. This paper presents the analysis of data from
                 variance between years. A method was developed based on relations               the Beaufort Sea Shorebase Monitoring Program and
                 between sediment grain size and contaminant concentrations. Stations            describes a method which was found to be both robust
                 where contaminant concentrations exceeded the relation's prediction
                 interval were identified as outliers and an index of contamination based        and easily interpreted.

                 on the magnitude of the departure from the prediction interval was
                 used to display their distribution on maps.                                                               MONITORING

                                          INTRODUCTION                                           The Beaufort Sea Shorebase Monitoring Program was
                                                                                                 initiated in 1982 in response to both public and
                 The Department of Indian Affairs and Northern                                   government concerns regarding oil and gas related
                 Development (DIAND), as the lead federal agency, has                            industrial development along the Tuktoyaktuk Peninsula
                 the legislated mandate (the DIAND Act) to manage                                (Figure 1). The program was developed and funded
                 Canada's northern resources. This involves promoting                            jointly by government and industry. The goal of the
                 development of resources while ensuring proper                                  program is to provide a time series sampling of
                 environmental management, which is particularly                                 concentrations of metals and hydrocarbons in marine
                 important in the arctic because of the role that renewable                      sediments near shorebase developments, and to monitor
                 resource harvesting plays in the life style of northern                         possible changes in concentrations of these substances.
                 natives. Monitoring is considered an integral part of the                       Field sampling was carried out in 1982, 1983, and 1984.
                 environmental management process. It plays an essential                         Through the Northern Oil and Gas Action Program
                 role in providing feedback to the decision-makers about                         (NOGAP), the samples from all three years have been
                 the appropriateness of environmental controls and                               analysed, and data reports documenting the sampling,
                 mitigative technology. Monitoring programs may also                             analytical techniques, and analytical results have been
                 create an information base - in this case, contaminants                         produced (Thomas et al. 1983, Arctic Laboratories
                 associated with support bases for offshore oil and gas                          Limited 1984 and Nuclear Activation Services Limited
                 exploration and development. Howeveri long term                                 1986). Summary reports have been prepared for the 1982-

                                                                     CH2585-8/8810ooo- 405         $1 @1988 IEEE

                                                                                                                                134" W                                                                                130, w

                                                                                                                                                                                                            + lig     /120
                                                                                                                                                                                                      + lie
                                                                                                                                                                                              + 117                   /123
                                                                                                                                                                                                                      ++ 122 121

                                                                                                                                                                                114                                                        70"N
                                                                                                                                              109                                                         190         a
                                                                                                                                + 88 B7 I0B,+I              + H2 4@10                         McKINLEY
                                                                                        + 89                                    +                                                             BAY
                                                                                                                                +       + 107         + III
                                                                                          +90                                   7-     TUFT     POINT
                                                                                     (,Zr  +91                                  +7           2
                                                                                                                                82, +83   /3               UHUTCHIS@OON
                                                                                                                                BI- 4@   31                   BAY                                                     CQ3 <2
                                                                                                                                C> I-- +  31

                                                                                                                                \ib         TOYAKTUK
                                                                                                                                   0   HARBOUR

                                                                                                                                                                                                                      pprox. 25 km.       I

                                                                                                                                Flpre Ia. Locations of 1982 - 1984 stations, Tuktoyaktuk Peninsula nearshore zone.

                                                                                                                                133-W                                                                 132-30-W                                                            132-W

                                                                                                                                                                                                                      +

                                                              TU.TOYAKTUX
                                                              HAMLET OF                                                         17
                                                                                                                                14 @
                                                                                                                                DEW 15                                                                                                                                         +54
                                                                                                                                LIN                                                                                                                                           lo"
                                                                                                                                I

                                                                                                                                wc +a +is
                                                                                                                                ONE 21                                                        TUFT POINT                   Ai               +41         +4
                                                                                                                                CAN.AR ESSO                                            IT?                                               HUTCHISON
                                                                                                                                GULF4                                            +35               1                                   '51 SA@
                                                                                                                                BE IL                                                + 36
                                                                                                                                                                                          +

                                                                                                                                +20                                         +33
                                                                                                                                + 29
                                                                                                                                  .pp..                                                                                               (17                               M--.,
                                                                 Fill- Ili. Locefloom of 1992-1984innions, Tktyakwk Hwbo-                                                                             RpmLd. Locsti- of 1992 -1984 nations, HutdAmin Bay and Tuft Folm.

                                                                                                                                        131. W
                                                                                                                                      +?I

                                                                                                                                                                                                      HEAMICHEL
                                                                                                                                   +70                                                                ISLAND          UH
                                                                                                                                                                                                                      ++,`@ 1.2
                                                                                                                                                                                                                      \Ili\. + 101
                                                                                                                                +0                           - 70-M                                                   96-+ +-R
                                                                                                                                                                                                                      + 91 + IOD
                                                                                                                                +79 +j"                                                                               \gs
                                                                                                                                +n +78                                                                                     495
                                                                                                                                +50 76'+0                                                                             STOK
                                                                                                                                P
                                                                                                                                +                                                                                     POINT
                                                                  + III               So 62                                     C;, VLAND+ 75+
                                                                                                                                74 +75+

                                                                                                                                64 +73

                                                                                                                                +72                                                                                                                       94
                                                                                                                                +66                                                                                                                  KING + 93
                                                                                                                                                                                                                                                     POINT

                                                                                                                                           appros. 5 Ion,

                                                                         Film le. Locations of 1982-1984 slatimem, McKinley Bay.                                                                   FIgarete. [Locations of 1992-1994 stations, Yukon Coast (Henchal Basin
                                                                                                                                                                                                                      new King Poim@

                                                                                                                                                                406

              83 data (Yunker 1986) and the 1982-83-84 data                     sediment collected. Therefore, statistical analysis was
              (Wainwright and Humphrey 1988). A similar monitoring              restricted to observations with concurrent grain size
              program was carried out in the nearshore Beaufort Sea             determinations, resulting in exclusion of about 40% of the
              area in 1984 (Can Test 1984). The four data sets include          contaminant observations.
              samples from 124 stations.
                                                                                Relationships between contaminant concentrations and
                                  DATA ANALYSIS                                 grain size were then determined (Figure 2) and the
                                                                                residual values from the contaminant to grain size
              Yunker (1986) determined that the       1982-83 data were         regression relations were analysed. The relationships
              unsuitable for detailed parametric      statistical analysis      were better for some contaminants than for others (Table
              without applying data transformations and other                   1). It was apparent, by inspection, that the residuals were
              manipulations. Differences in sampling design, and                normally distributed for each laboratory and year
              sampling and analytical methods between data sets often           analysed, implying that remaining variance was caused by
              limit possible approaches to statistical analysis of data.        intra- and inter-laboratory analytical variance. This was
              Individually and in combination, the data are often               subsequently shown using statistical tests. An example is
              neither normally distributed nor homogeneous. For this            chromium, an element which adheres closely to the grain
              study, the entire data set was examined to identify an            size relationship. A histogram of the residuals plotted by
              approach or methodology that would permit                         laboratory (Figure 3) indicates that residuals from
              simplification of statistical analysis and interpretation.        individual laboratories, and therefore years, appear to be
              Data may be analysed in relation to a reference data set if       normally distributed.
              the study data set and the reference data set represent the
              same population. The pooled data may then be examined                                          TABLE I
                                                                                                       Coeffleleals of determination from
              for outliers (anomalous values) relative to some                                   I..t q.am revv"Jon analygis Ron" percentage clay
              characteristic and the residuals examined for the effects of                                         C@Mclmt
                                                                                                                       of
                                                                                                                  determinn ion
              year and location. The approach adopted here was to                                      Contaminant     (0) t
              assume that the data belonged to a single population. This                             Barium            603
              population was then characterized and examined for                                     Cadmium           60.9
                                                                                                     Otornium          78.7
                                                                                                     Copper            769
              deviating observations or outlieTS.No reasons were found                               Lead              25'.8
                                                                                                     Mercury           74.6
                                                                                                     Nickel            73A
              to discount the assumption of a single population when                                 S.m Mkanes        31'7
                                                                                                     Surn PAHs         32.8
              using the Shorebase data and the nearshore data.                                       Zim               as

                                                                                                                           9
              Previous workers had observed a relationship between                                                         9
                                                                                                                            II   Y-a75U-2&8
              sediment grain size and contaminant concentration                                                             f    A0787
                                                                                                               R       'a0       -356
              (Adams et al. 1980, Dossis and Warren 1980), in samples                                           o -R
                                                                                                                 y
                                                                                                                       A'  E A
                                                                                                                  A@ E   a
              from the Canadian Beaufort Sea (Yunker 1986, Hoff and                                OF J R    A
                                                                                                  RI R al    E    A    .6%
                                                                                               NN j            A               u
              Thomas 1986, Arctic Laboratories Limited and LGL Ltd.                          R
                                                                                                  A
              1987) and in the Alaskan Beaufort Sea (Boehm et al.
              1985, 1986). We examined the available data sets for this
                                                                                                                 an      an     100
              relationship and found that the contaminants of interest                                    x ew
              were determined primarily by the grain size of the

                                                                             407

                   Samples with contaminant concentrations in excess of the                           OUTLIERS BY CONTAMINANT
                   value predicted by the grain size relations plus a 99%
                   prediction interval were then identified. Maps of outliers             Outliers were defined as observations with a magnitude
                   were plotted for each contaminant (e.g. Figure 4).                     either higher or lower than the range of magnitudes which
                   Inspection of the resulting maps identifies an association             statistically characterized the distribution of the data. The
                   between industrial activity and sites of outliers. Many of             range of magnitudes which characterized the data
                   the outliers identified are associated with loading docks or           distribution may be calculated as a confidence interval or
                   sites of dredging activity.                                            prediction interval.

                                                                                          For each contaminant, the degree of contamination was
                                                                                          calculated as:

                                                                                              Di @ (Co - Cu)       Cm
                                                 @J:                                      where:
                                                                                              Di = degree of contamination for contaminant i;
                                    Figuml Frequency diaribuden, of mid,ah for ch-niu, (Cr),  Co =  concentration observed;
                                                                                              Cm= mean concentration of contaminant i from the
                                           +    *+                                                  data used to determine the grain size relation;
                                                      p                                             and
                                                        +                                     Cu    upper boundary of the prediction interval from
                                                                                                    the grain size relation calculated as follows:

                                                                                                     + tcx/2 * s [ I + 1/n +    %clay - %claym )2
                                                    +                                     CU     CP
                                                   +                                                                SS%clay
                                                                                          S2 =(SSC-jo@-SSC%clay)/(n-2)
                    The environmental significance of anthropogenic inputs                and
                    was assessed by determining an index of contamination,
                    which was mapped in the same way as the contaminant                          Po + (A, -%clay)
                    outliers. This index of contamination is the sum of the               CP
                    deviations from the grain size relations for each                     where:
                    contaminant. At the outset of the data analysis it was
                    envisioned that an environmental risk index would be
                    determined. However, risk indexes were not determined                     po and #1 are the regression coefficients;
                    as a relatively arbitrary "toxicological factor" would have               %Clay      = percent clay observed;
                    to be determined for each contaminant. The maps of                        %Claym     = mean percent clay from the data used to
                                                                                                            determine the grain size relation;
                    contaminant deviations and index of contamination were
                                                                                              n          = the number of observations on which the
                    sufficient to identify and interpret areas of risk. The
                                                                                                            grain size relation is based;
                    question of what magnitude of contaminant index should                    s2         = estimated variance of the random error;
                    cause concern was not addressed for the same reason.
                                                                                              SS%Clay       sum of squares for percent clay;

                                                                                     408

                   SSC           sum of squares for the contaminant;                   reference areas were produced in which the type and size
                   SSC%Clay =sum of squares of the cross-product:                      of symbols represent the magnitude of the index of
                                 contaminant x percent clay;                           contamination. In these maps a circle presents a value of
                   t,Z/2       = critical value of t for probability a; and            1>0, where the size of the circle is related to the
                   CP          = concentration of contaminant predicted                magnitude of 1, and crosses indicate values of I=O.
                                 by the regression relation.                           Stations are labeled with the contaminants considered as
                                                                                       outliers.
               All values of Di less than zero are considered to be zero,
               as a negative value for Di requires that the concentration              The maps demonstrated that the majority of the observed
               observed is less than that predicted by the grain size                  outliers were found in Tuktoyaktuk Harbour and
               relation. The index of contamination is then calculated by              McKinley Bay. There were also some outliers in
               summing the values of Di for all contaminants measured                  Kugmallit Bay (cadmium) and Hutchison Bay (copper
               for that sample:                                                        and mercury). The pattern of outliers for McKinley Bay
                                                                                       and Tuktoyaktuk Harbour were different.
                                         I       Di)
                                               i                                       Simple deviation from expected values does not
               The resulting index, 1, will be zero if the concentrations of           necessarily imply anthropogenic input. For hydrocarbons,
               all contaminants observed are less than, or equal to, the               the patterns of specific compounds must be examined. If
               prediction interval for probability                                     the CPI is high, it is likely that the source was biogenic,
                                                                                       not anthropogenic. The compositional pattern of the
               Two values of a were considered and evaluated, 5% and                   alkanes and PAHs as determined by gas chromatography
               1%, which correspond to 95% and 99% prediction                          should be examined for all hydrocarbon outliers.
               intervals. Figures 5 and 6 present maps of the index of                           ENVIRONMENTAL SIGNIFICANCE
               contamination derived from 95% and 99% prediction
               intervals respectively. The 99% prediction interval was                 The degree of contamination (D) and index of
               selected because it gives results which are consistent with             contamination (I) values greater than zero indicate that
               expectations (that the foci of contamination are the active             observed concentrations were in excess of those predicted
               shorebase areas), because falsely concluding that a station             on the basis of sediment grain size. It cannot be assumed
               is contaminated is undesirable, and because departure
               from the prediction interval does not necessarily imply                 that values greater than zero result in negative. effects on
                                                                                       the environment, but rather that values of I greater than
               environmental impact. It is preferable to adopt the more
               conservative value.                                                     zero imply some risk of environmental effects.

               The geographic distribution of the index of contamination               Thomas et a[. (1986) reviewed information on ecological
               (I) (based on the 99% prediction interval) is presented in              effects of contaminants and concentrations of concern.
               map form (Figures 7 to 10). Mapping was performed                       Concentrations of concern are generally available for
               using ESLMap, a software mapping package developed by                   water column exposure but are limited for sediments. In
               -ESL Environmental Sciences Limited. This software                      Canada, the only criteria for sediments are from the
               allows the data to be displayed interactively on detailed               Ocean Dumping Control Act (ODCA) applicable to "bulk
               maps of variable scale, with symbol sizes and types                     wastes" and thus to sediments when disposed pursuant to
               determined on the basis of criteria defined. by the                     the Act. The ODCA specifies limits for only mercury,
               operator. Detailed maps of the embayments and                           cadmium and petroleum-related compounds: cadmium -

                                                                                409

                                                                                                                                       132'.                                                                       Ise..                                                                          J32- W

                                               0-
                                                                                                                                                                                                         0
                                               +

                                                                                                                                                                     p7,      70-N                                                                                                                                                      70- N
                                                                                                       0,+ +1               44+        +                             'a                                                                                                                                                .
                                                                                                + ++                  +    +                          Q7                                                                                                                                                               Is
                                                                                                    +                  +                                                                                                                                  + ++                 +               ++
                                                                                                                       +
                                                                                            A                     0
                                                                                                                                                                     Q7                                    +                                             C?
                                                                                                                                       to                                                                                                                                                      A
                                                                                                                                                                                                                                                                                   0                                   Is
                                                                                                                16
                                                                                   o                                                                                                                                                                                           16

                                                                                                                                                                     pp-. 50 lan.                                                                                                                                      aps,a,. 50 lort.

                                                             Ftipars S. Map of distribution of Index of contannination (1) hued on 95%                                                                                Flipin 6. Map of distribution of index of contarnination (1) bound on 99%
                                                                         lnedietion intemal.                                                                                                                                      pdiction 1.1-1.

                                                                                                                                                      Is,- w                                                                                             153-W

                                                                                                                                                                            L-st                                                            +           *+ q
                                                                                                                                                                                                                                                                    zo,
                                                                                                                                                                                                                                                  Ph               0-

                                                                                                      +        Cu.Cd.ln+
                                                                                       a It                     4@# `+          +                                                                                                                                              OrApb
                                                                                                                                   +                                                                                                                                           Alt
                                               +                      +                             C         'A

                                                                                                                  +                                                                                                                                                                                                                      Go' 30' N
                                                                                                                                                      o                                                                                                                        +                                       0
                                                                                                                                                      +.: .11M.      "dic-                                                                                            C1. Alt                                          +
                                                                                                                                                      A I            a.-                                                                                                                                               Alk
                                                                                                                    0 DO. Alt                         a.             ho'l-                                                                                                                                             0: ba'Wra
                                                                                                                                                      Cd             d.l..                                                                                                                                             eadral..
                                                                                                                                                      C,                                                                                                                                                               C,
                                                                                                                                                                     Car'Call In                                                                                                                                       -.I..
                                                                                                                                +                     C              -r                                                                                           +                                                    Cwpor
                                                                                                                                                      No             anarcur
                                                                                                                                                      NI             fa
                                                                                                                                                      PAW ="                                                                                                                                         .                 PAN: 4wan PAN
                                                                                                                                                                     PAM
                                                                                                                                                      Ph             load                                                                                                                                              'ad
                                                   ,Ppmx, 5 Um.                                                                                       Z.                                                                                                                          up-.. 2 kon,                         sine

                                                              Fightell.                                                                                                                                                   Fillorre 7. map or distribution of Index of ecrataraluation (1) for Tuktoyakluk
                                                                                                                                                                                                                                     HA,b-,.

                                                                                 132- 301 IN                                                                         132-W                                                                     134- W

                                                                                                                                                                                                          +

                                                                                                                                                                                                            +
                                                                                                                                                                                                                                                                                      +

                                                                                                         +                                     0 CA                                                                                                                                       +

                                                                                                                                                      +                                                                                                                                   0 Cd

                                                               +                                                                       +              0
                                                                   +      +                                         +                                 +              Wind- ix.d'.-Aths                                                                                                         +                       +         pradl. W
                                                                       +                                                                              A": Zon -1                                                                                                                                                       :lk: sous I Ch"ah
                                                                                                                                                                     on                                                                                                                                                sodral..
                                                   usurer. 5 Am.                                                                                      Cd             ..d.A.                                                                                                                                            n. Act,
                                                                                                                                                      cr                                                                                                                                                               Cr eltraml,
                                                                                                                                                      a                                                                                                                                                                cu.
                                                          +                                                                                           c              cup;p.,  GV40-N                                                                                           /C'   jCd                               No . eapps,
                                                                                                                                                      No             ashr-,                                ans- 10 AM.                                                                                                 ahar@
                                                                                                                                                      Air            atk.,                                                                                                                                             PSI       .1
                                                                                                                                                                     PAN                                                                                                                                               PAN: Mwe" PAN
                                                                                                                                                      Ph                                                                                       0
                                                                                                                                                      Zn                                                                                       4                                               n
                                                               Fliparell. M.frofdistribution of Index ofconlannination (1) for Hutchison Bay.                                                                             nitsumlit Mpofdistrlbudonorinduofmmffdmdm([) Far KuSchallit Bay.
                                                                                                                                                                                                            +                                                                         ++0-
                                                                                                                                                                                                                                                                                          +       +                    0
                                                                                                                                                                                                                                                                                               +                       Ask-

                                                                                                                                                                                                                                                                                                                       Cd
                                                                                                                                                                     on
                                                                                                                                                                                                                                                                                                                       u

                                                                                                                                                                                                                                                                                                                       tharn     PAN
                                                                                                                                                                                                                                                                                                                       C

                                                                                                                                                                                                                                                                                                                       land
                                                                                                                                                                                                                                                                                                                       Ana
                                                                                                                                                                                                                                                                                                                       PA
                                                                                                                                                                                                                                               40                                              n

                                                                                                                                                                                        410

                   0.6 ppm, mercury - 0.75 ppm, petroleum-related                               does not indicate that environmentally significant changes
                   compounds - 10 ppm of hexane soluble substances.                             to the sediments have occurred, but that some detectable
                                                                                                changes were occurring in the two major shorebase
                   No concentrations of mercury in our data approached the                      embayments.
                   ODCA limit. Sixty-one observations of cadmium
                   exceeded the ODCA limit with a maximum observed                                                   -REFERENCES
                   concentration of 1.01 ppm. The upper boundary of the
                   95% prediction interval exceeded the ODCA limit of 0.6                     Adams, D.D., DA. Darby a     nd RJ. Yuong. 1980. Selected analytical
                   ppm at a value of about 38% clay. It must be expected                          techniques for characterizing the metal chemistry and geology of
                   that cadmium concentrations will exceed the ODCA limit                         fine-grained sediments and interstitial water. In: R.A. Baker
                                                                                                  (editor). Contaminants and Sediments, Volume 2. p. 3-28.
                   where the sediments are of fine texture. This result
                   suggests either that there may be an environmental risk                    Arctic Laboratories Limited. 1984. Beaufort Sea coastal sediment
                   associated with fine sediments in the Beaufort Sea or that                     reconnaissance survey: A data report on 1983 geochemical
                   the ODCA limit for cadmium is not applicable (i.e., is too                     sampling. Report for Environmental Protection Service,
                                                                                                  Yellowknife, NWT; (unpublished manuscript) 39 p.
                   low). With respect to the limit for petroleum-related
                   compounds, 244 of 249'observations of hexane-extractable                   Arctic Laboratories Limited and LGL Limited. 1987. Beaufort sea
                   compounds exceeded the ODCA limit of 10 ppm.                                   ocean dumpsite characterization. Report for Environmental
                                                                                                  Protection Service, Yellowknife, NWT; (unpublished manuscript)
                                                                                                  100 p. + appendices.

                                              DISCUSSION                                      Boehm, P.D., E. Crecelius, W. Steinhauer, M. Steinhauer, S. Rust and
                                                                                                  J. Neff. 1985. Beaufort Sea monitoring program: Analysis of trace
                   The method developed in this project was easy to use and                       metals and hydrocarbons for outer continental shelf (OCS)
                                                                                                  activities - Year I results. Report by Battelle New England
                   will be easy to maintain over time. The data are held in a                     Research Laboratory for Minerals Management Service, Alaska
                   dBase IH+ data-base, and the calculations are performed                        OCS Region; (unpublished manuscript) 162 p.
                   using a spread-sheet program such as Lotus 1-2-3. The
                   method clearly indicates deviations from expected                          Boehm, P.D., E. Crecelius, W. Steinhauer, M. Steinhauer and C.
                                                                                                  Tuckfield. 1986. Final annual report on Beaufort Sea monitoring
                   contaminant concentrations in Beaufort Sea nearshore                           program: Analysis of trace metals and hydrocarbons from outer
                   sediments. Any future determinations can be added to the                       continental shelf (OCS) activities (Contract No. 14-12-0001-30163).
                   data-base and, if they do not represent outliers, can be                       Report by Battelle New England Research Laboratory for Minerals
                   included in the baseline set of data. Any new data which                       Management Service, Alaska OCS Region; (unpublished
                                                                                                          ript) 238 p.
                   deviate significantly will be flagged by a value of the index
                   of contamination greater than zero.                                        Can Test Ltd. 1985. Chemical analysis of samples collected for
                                                                                                  Beaufort Sea nearshore monitoring program, 1984. Report for
                                                                                                  Environmental Protection Service, Yellowknife; (unpublished
                   The method appears to be sufficiently robust to                                manuscript) 96 p.
                   accommodate differences in analytical and sampling
                   methodology and differences between laboratories. Any                      Dossis, P. and L.J. Warren. 1980. Distribution of heavy metals between
                                                                                                  the minerals and organic debris in a contaminated marine
                   improvement in consistency between methods will be seen                        sediment. In: R.A. Baker (editor). Contaminants and Sediments,
                   as increased sensitivity, but the present results appear to                    Volume 1. p. 119-39.
                   be sufficiently sensitive to detect the influence of                       Hoff, J.T. and DJ. Thomas. 1986. A compilation and statistical analysis
                   anthropogenic activity and to identify areas of                                of high quality Beaufort Sea sediment data with recommendations
                   contamination.                                                                 for future data collections. Report by Arctic Laborat ,ories Limited
                                                                                                  for Environ   'mental Protection Service, Yellowknife, NWT;
                   Ile analysis of the monitoring results from 1982 to 1984                       (unpublished manuscript) 118 p.

                                                                                          411

                 Nuclear Activation Services Limited. 1986. Beaufort sea Shorebase
                     monitoring program; data report on 1984 geochemical sampling.
                     Report for Department of Indian Affairs and Northern
                     Development, Yellowknife, NWT; (unpublished manuscript) 122 p.

                 Thomas, D.J., P.F. Wainwright, B.D. Arner, and W.H. Coedy. 1983.
                     Beaufort Sea coastal sediment reconnaissance survey: A data
                     report on 1982 geochemical and biological sampling. Report by
                     Arctic Laboratories Limited for Environmental Protection Service
                     (Yellowknife), Dome Petroleum Limited, Esso Resources Canada
                     Limited and Gulf Canada Resources Inc., Calgary, Alberta;
                     (unpublished manuscript) 459 p.

                 Thomas, DJ., W.S. Duval, and W.E. Cross. 1986. Development of a
                     monitoring program for contaminants in Tuktoyaktuk Harbour,
                     NWT A report to the Environmental Protection Service,
                     Yellowknife, NWT 68 p.

                 Wainwright, P.F., B. Humphrey. 1988. Analysis of sediment data from
                     the Beaufort Sea Shorebase Monitoring Program, 1982 to 1984.
                     Environmental Studies Research Funds Report Number
                     090.Ottawa, 147 p.

                 Yunker, M.B. 1986. Final report; 1982-83 Beaufort Sea Shorebase
                     monitoring program; Statistical analysis and recommendations for
                     future programs. Report by Dobrocky Seatecb Ltd. for Indian and
                     Northern Affairs Canada, Yellowknife, NWT; (unpublished
                     manuscript) 165 p.

                                                                                         412

                                            A HIGH SPEED MULTI-CHANNEL DATA ACQUISITION SYSTEM    1
                                           FOR REMOTE ACOUSTIC SEDIMENT TRANSPORT STUDIES

                                      A.E. Hay 2, L. Huang, E.B. Colbourne, J. Sheng and A.J. Bowen

                                       Department of Physics, Memorial University of Newfoundland,
                                                      St. John's, Nfld.Canada AlB 3X7

                                  Department of Oceanography, Dalhousie University, Halifax, N.S. Canada

                                    ABSTRACT                             systems which exploit the frequency dependence of
                                                                         the scattered sound and which can be used for both
               A multi-frequency, multi-beam   acoustic system for       backscatter and forward scatter measurement.
               tethered near-bottom sediment concentration and
               size profile measurement In the the ocean has been        We have therefore adopted from the beginning a
               developed.  EXADAC,   the data acquisition and            multi-channel approach to system design which
               control section of the system, is described. The          incorporates at least three acoustic frequencies
               system at present operates with 4 acoustic beams          and    a    choice   between    several     multi-beam
               and 3 frequencies: 1.0, 2.25, and 5.0 MHz. The            geometries. This represents a significant advance
               data acquisition system consists of a CAMAC crate,        over earlier acoustic        devices   for suspended
               a PC/AT-compatible microcomputer and a 9-track            sediment concentration profiling, which have been
               streaming tape drive. The CAMAC crate contains            restricted to a single frequency In any given part
               several data acquisition and control modules,             of the water column (1-4). Previous multi-beam
               Including:  a programmable four-channel        12-bit     devices have been developed to measure suspended
               transient recorder, a programmable clock, and a           sediment concentration (5) and suspended sediment
               GPIB  interface controller.     Typical     4-channel     concentration and size (6), but must be physically
               operating characteristics are: total range, 1 m;          raised or lowered to obtain profiles.
               range resolution, 2 cm; transmitted pulse length,
               20 ps; pulse-to-pulse interval, 12 ms; acquisition        One of the principal technical difficulties in
               rate for 4-ping ensemble-averaged backscatter             developing multi-channel profiling systems Is the
               profiles for four channels, 2 Hz. The system has          high data rate. Typically, a range resolution of
               been used in two field experiments. Typical data          order 1 cm is needed. Resolving the detailed
               are presented.                                            temporal structure of the suspended sediment
                                                                         concentration field in the nearshore zone requires
                                                                         that ensemble-averaged backscatter profiles be
                                 1. INTRODUCTION                         obtained 5 to 10 times faster than the highest
                                                                         frequency wave involved In transporting sediment,
               In November 1986 funding was received to Initiate         which is typically of order 1 Hz. Assuming 100
               a joint project between Memorial University of            range bins, which Is equivalent to a 1 m range
               Newfoundland and Dalhousie University to develop          interval at 1 cm resolution, and 12-bit samples, a
               acoustic systems for sediment transport studies in        four-channel    system    would   therefore    produce
               the nearshore zone and on the continental shelf.          roughly I Gbyte of data per day. A further
               The project acronym is RASTRAN: Remote Acoustic           constraint    Is    that   consecutive     backscatter
               Sediment TRANsport measurement.                           profiles be averaged to eliminate the purely
                                                                         statistical variations    in signal amplitude which
               The principal initial objective of the RASTRAN            occur   even    in  the   absence of     changes     in
               Project  is   to  obtain   accurate    profiles    of     concentration (2). The data acquisition system
               suspended sediment concentration and   concentration      must therefore perform at least the arithmetic
               gradients in the bottom 1 m of        the ocean at        necessary    to  produce    the    "ensemble-averaged"
               sampling frequencies approaching 10 Hz. In order          profiles mentioned above. In addition, there is
               to distinguish contributions to the scattered             the requirement that the data acquisition system
               signal due to variations in suspended sediment            be   flexible    and expandable,     to    accommodate
               concentration from those due to particle size             additional channels as the need arises.
               changes, it is in our view necessary to develop
               1                                                         We are developing two different RASTRAN systems.
               RASTRAN Project Contribution No. 1                        System 1 Is connected to an above-water data
               2                                                         acquisition and control system, and is Intended
               On sabbatical leave at DELFT HYDRAULICS, P.O. Box         primarily for use In the nearshore zone. System 2
               177, 2600 MH Delft, The Netherlands                       Is designed to be completely submersible and
                                                                         autonomous. It Is Intended primarily for use on

                                                    CH2585-8/88/0000. 413 $1 @1988 iEEE

                 the continental shelf.                                      2.1 Mesotech Acoustic Sounder Modules

                 There have been two field deployments of System 1:          The Model 810 acoustic sounders were produced by
                 at Queensland Beach, Nova Scotia In 1987; and at            Mesotech Systems for this project. They are based
                 Bluewater Beach, Georgian Bay, Ontario in 1988,             on the company's existing line of small immersible
                 Each has    resulted    In successful      continuous       echo sounder modules, with Improvements to the
                 deployment with the system in        the water and          transceiver to permit: synchronous generation of
                 operating for periods of 3 to 4 weeks. The                  the transmitted pulse; jumper selectable values of
                 Queensland Beach deployment was      a test of the          output power, transmitted pulse length, and TVG
                 prototype   system    using    only   one    acoustic       (time-variable gain) schemes; and a choice of
                 frequency. Three frequencies and four different             at least three frequencies including 1, 2.25, anci
                 acoustic beams were used at Bluewater, making this          5 MHz.
                 to  our    knowledge   the    first   time   that    a
                 mul t I -frequency, multi-beam acoustic backscatter         The  acoustic    sounder   modules   consist   of    a
                 system has been successfully deployed for sediment          transceiver   and    single   element    piezoceramic
                 transport studies In the nearshore zone.                    transducer mounted in an immersible pressure case
                                                                             (Figure 2). The modules are powered and triggered
                 In this paper we describe the data acquisition and          externally.   The signal received after pulse
                 control section which solves the data handling              transmission is heterodyned down to 455 kHz, which
                 problem for System 1.      A companion paper (7)            Is the frequency of the receiver output. More
                 describes the design considerations for System 2,           detailed     specifications      and      performance
                 which is still under development.                           characteristics of the modules will be presented
                                                                             in another article.

                                 2. RASTRAN SYSTEM  1                        2.2 EXADAC: The Data Acquisition System

                 The complete System 1 is sketched    in Figure 1. It        The data acquisition and trigger generation system
                 consists of the above-water data     acquisition and        has been developed as part of the RASTRAN Project.
                 trigger generation system which is connected via            It has been given the name EXADAC, which stands
                 armoured   multi-element     (coaxial   and     single      for EXpandable Acoustic Data Acquisition System.
                 conductor) cables to the Mesotech Model 810
                 acoustic sounder modules described below. The               A photograph of the system Is shown in Figure 3,
                 coaxial elements are used for the signals and the           and a block diagram In Figure 4. It is based on a
                 trigger pulses. the single elements are used for            LeCroy model 1434A CAMAC crate, which provides a
                 24 VDC power. At present, four Mesotech acoustic            rapid    transfer   data   highway    between     data
                 sounders can be deployed on two armoured cables at          acquisition modules and a GPIB interface to the
                 distances from the beach up to 300 m.             This      host  computer.    The data acquisition modules
                 limitation is due to the present cable length.              consist of a LeCroy model 6810 programmable

                                     455 KHz SIGNAL
                                                                 ENVELOPE                      EXADAC
                                                                 DETECTORS           No

                                                                                              FUNCTION
                                                                                              GENERATOR

                                                                          TRIGGER
                                                                          PULSE

                                       MESOTECH       810'S
                                   68                    h

                                                  Figure 1. Block diagram of RASTRAN System I

                                                                        414

                                                                          user. These data are stored In the 6810's internal
                                                                          memory, and are downloaded between triggers via
                                                                          the CAMAC crate and GPIB interface           to the
                                                                          computer.

                                                                          The   6810  transient     recorder  is  capable    of
                                                                          digitizing at a maximum rate of     5 MHz in single
                                                                          channel operation and at 1 MHz in four-channel
                                                                          mode, with 12-bit resolution. The   digitizing rate,
                                                                          input voltage range, and pre-      and post-trigger
                                                                          windows are among the programmable features of the
                                                                          system. For our applications,       which typically
                                                                          involve transmitted pulse lengths of 20 ps, the
                                                                          digitizing rate is usually 200 kHz, and the
                                                                          post-trigger window length 1 to 2 ms.

                                                                          The acoustic sounders are triggered at a rate of
                                                                          80 Hz. This rate Is 80% of the maximum rate quoted
                                                                          by the manufacturer, and is slow enough that
                 d"Y
                                                                          contamination    by    surface-to-bottom     multiple
                                          "j,
                                                                          reflections has  not yet been a problem     even in
                Pry,    1"r

               Figure 2. The Mesotech      810 acoustic sounder,
               showing transducer and under water connector.
                                                                                          ff'Ps P
                                                                                           A'
               high-speed, 12-bit resolution, 4-channel transient
               recorder, and a model 8501 programmable clock also
               made by LeCroy. Data Is transferred from the crate
                                    -compatible microcomputer and
               to an 8 MHz     PUAT
               stored after processing on a Thorne/EMI model 9900
               9-track streaming tape drive. Data are displayed
               using colour graphics either as time series of
               backscatter at selected ranges or as acoustic
               Images colour-coded with respect to backscatter
               amplitude, intensity or concentration.

               As presently configured, up to four separate
               acoustic   sounder    modules   can   toe   triggered
               simultaneously and the four received signals
               digitized simultaneously using EXADAC. The system                                           MS
               Is        limited in principle to four units.
                   not
               Additional channels can be accommodated by adding
               another transient recorder to the CAMAC crate. The
               system can also be operated with 1, 2 or 3 as well                                               -ENNOMM
               as 4 channels. We describe four-channel operation
               below.

               The acoustic sounders are triggered under    computer
               control. The trigger pulse is generated by a
               command to the programmable clock in the CAMAC
               crate, which Is then used to activate a Wavtek                                        VF
               function generator capable of driving the lines to
               the sounders (Figure 1).

               The output signal from each sounder module, after
               being passed through an envelope detector to
               eliminate the 455 kHz carrier (Figure 1), is fed
               into one of the four input channels on the 6810
               transient recorder. The transient recorder is
               begins digitizing when it receives the trigger             Figure   3.   Photograph    of   the   EXADAC    data
               pulse from the function generator (Figure 4): that         acquisition system. The LeCroy Model 1434A CAMAC
               is, at the same time the acoustic sounders are             crate is at the top. Below it are, in descending
               triggered.   All   four   channels   are    digitized      order, the Thorn/EMI streaming tape drive,        the
               simultaneously during a preset time window (or             envelope detectors,    the computer chassis,      the
                  I @

                  ONNIMW

               equivalently, a range window)      selected by the         function generator and the DC power supplies.

                                                                     415

                                                         INPUT                          6810
                                                          SIGNALS
                                                                                   TRANSIENT
                                                                   TRIG   IN        RECORDER

                                                       FUNCTION                                              CAMAC
                                                       GENERATOR                                             BACK-
                                                                   TRIG OUT             8501                 PLANE
                                                                                        CLOCK

                                   COLOUR                  PC /AT                       GPIB
                                   MONITOR                                         CONTROLLER

                                                         9-TRACK
                                                    STREAMING TAPE
                                                           DRIVE

                                                           Figure 4. EXADAC: B   lock diagram

                  water as shallow as 2 m. In the 12 ms interval                 larger directly addressable memory sizes currently
                  between    triggers     the   digitized, backscatter           available In 32-bit 80386-based machines should
                  profiles for the four channels are downloaded from             allow us to increase the acquisition rate by at
                  the 6810 to the computer and stored in an array. A             least the desired factor of three.
                  user-selectable number of consecutive backscatter
                  profiles, usually four, are averaged to to yield a
                  single ensemble-averaged profile. At this point                                3. FIELD EXPERIMENTS
                  further averaging of the data is performed over
                  each range bin. The width of the range bins are                RASTRAN   System    1,   using    EXADAC    for    data
                  also   selectable    by   the   user.    Finally,    the       acquisition,   has been deployed in two field
                  ensemble- and bin-averaged profile is written                  experiments,   one at Queensland Beach, N.S. in
                  either to the hard disk or to a RAM disk.                      October 1987,  and one at Bluewater Beach, Georgian
                                                                                 Bay, Ontario   In May and June 1988. During both
                  It has been necessary to develop our own special               experiments    independent    measurements    of     the
                  purpose data acquisition and processing software               velocity field, pressure and suspended sediment
                  to perform these operations. We now have a fully               concentration were made in parallel as part of a
                  operational package which permits us to acquire                second joint   project with B. Greenwood of the
                  individual      acoustic      backscatter       profiles       University of Toronto and one of us (AJB). The
                  simultaneously from 4 channels over a range of                 independent    suspended    sediment     concentration
                  about 1 m with 2 cm range resolution      at a minimum         measurements were made using Optical Backscatter
                  Intervals of 12 ms. Four ping ensemble-averages of             Sensors (OBS's).
                  these backscatter profiles are acquired at a
                  maximum rate of 2 Hz.                                          At Queensland we successfully demonstrated that
                                                                                 the Mesotech modules and the EXADAC system could
                  Although the 2 Hz ensemble-averaged profile                    be used to monitor wave-induced resuspension of
                  acquisition rate for four channels represents a                sand in the field. Preliminary analysis of the
                  respectable achievement in our view, and is we                 Queensland data shows that the RASTRAN and OBS
                  believe unmatched by any other system, it is                   results are comparable. A typical example of these
                  slower than would be desirable for certain types               data is shown in Figure 5. It can be seen that
                  of study. The limitation on speed is the 8 MHz,                sediment   is lifted into suspension primarily
                  16-bit microcomputer. The faster clock speeds and              during the passage of wave groups, consistent with

                                                                            416

              previous studies using OBS's alone to measure                as possible (about 15 cm maximum horizontal
              sediment concentration(B). This effect Is more               separation between transducers). The other 2.25
              obvious in the RASTRAN data from the Queensland              MHz unit was deployed about 2 m farther offshore
              experiment, apparently because the sensitivity of            from the first. Data was collected during six
              the OBS's was set too low. This difference in                storm events, and Is being processed now to test
              sensitivity accounts for much of the difference in           the capability of the three-frequency system to
              the overall structure of the two concentration               discriminate between concentration and size.
              time series in Figure 5. The differences In the
              detailed structure are due to the faster sampling
              rate for the OBS, and to differences In the                               4. LABORATORY EXPERIMENTS
              detected volume and the spatial separation of the
              two instruments (0.6 m horizontal distance).                 EXADAC is used in the laboratory as well as In the
              Nevertheless, It Is gratifying that the absolute             field. A special purpose tank has been constructed
              values of the RASTRAN and OBS concentrations are             to perform acoustic calibrations of the Mesotech
              comparable.                                                  acoustic sounders, to calibrate their response as
                                                                           a function of suspended sand concentration and
              We have also been able to obtain time series of              size, and to test standard targets. EXADAC is used
              bottom position from the RASTRAN data from                   to acquire and process the calibration data.
              Queensland. The bottom position varies with time             Calibration    experiments     can     be    performed
              by �2 cm, consistent with sand ripples (which                simultaneously on three Mesotech modules     operating
              during this experiment were a few cm high at the             at different frequencies. The complete     System 1,
              RASTRAN location) changing form or migrating                 including Mesotech modules,        cables,    envelope
              through the sound beam.                                      detectors and EXADAC, can also be assembled and
                                                                           tested in the laboratory facility. This ability to
              At Bluewater we deployed 4 Mesotech modules: two             use the same system in the lab and in the f ield
              2.25 MHz units, one I MHz unit and one 5 MHz unit.           has proved to be very valuable during software
              As mentioned above, ensemble-averaged backscatter            development and system checkout prior to,the field
              profiles with 2 cm range resolution were obtained            experiments.
              simultaneously from these 4 instruments at a rate
              of 2 Hz. The 1 and 5 MHz modules, and one of the
              2.25 MHz modules, were mounted as close together

                              LO

                                                                    A.     NAh A A A
                                                      WVV7     vqp V@ qf@pjq

                              LO

                                                                                                                 cc

                              co                                                                                     0

                                                                             A                 AA
                                            1.0         2.0           3.0          4.0         5.0          6.0
                                                                MINUTES

                              Figure 5. Suspended sediment concentration approximately 8 cm above bottom and
                              wave data from Queensland Beach, Nova Scotia In October, 1987. From top to
                              bottom: on-offshore component of velocity; OBS sediment concentration;            and
                              RASTRAN sediment concentration.

                                                                     447

                                     5. CONCLUSIONS                                Profiling System," Proc. Coasta-l Sediments '87,
                                                                                   (New York: ASCE), 236-249.
                  EXADAC Is a multi-channel data acquisition and                  5
                  triggering     system   developed     for    use     with        Schaafsma, A.S. and W.J.G.J. der Kinderen, 1986.
                  high-frequency    acoustic     transceivers.     It     is       "Ultrasonic     Instruments     for    the    Continuous
                  presently      capable     of     acquiring        4-ping        Measurement of Suspended Sand Transport," Proc.
                  ensemble-averaged backscatter profiles over a I m                IAHR Symp.   2n Measuring Techniques Ln Hydraulic
                  range interval with 2 cm range resolution and                    Research,    A. C. E.   Wessels,    Editor      (Balkema,
                  12-bit    data    resolution     on    four     channels         Rotterdam), 125-136.
                  simultaneously at a rate of 2 Hz. The system Is                 6
                  readily expandable to accommodate more channels.                 Crickmore,   M.J., I.E. Shepherd, and P.M. Dore,
                                                                                   1986. "A     Field Instrument for Measuring the
                  EXADAC has proved to be a versatile tool. It has                 Concentration and Size of Fine Sand Suspensions,"
                  been used In two field experiments as part of the                Proc. Intl. Conf. on Measuring Techniaues of
                  RASTRAN Project for which It was developed. It Is                Hydraulics Phenome        In Offshore, Coastal and
                  also  used     in  the    laboratory     for    acoustic         Inland Waters   '   London, U.K. 9-11 Apr.          1986,
                  calibration work and data processing, including                  425-441.
                  acoustic image analysis.                                        7
                                                                                   Hazen, D.G., A.E. Hay and A.J. Bowen, 1988.
                  While the 2 Hz averaged profile acquisition rate                 "Design    Considerations for RASTRAN System 2,"
                  is satisfactory for many types of sediment                       Proc.   OCEANS '88, Companion to this paper.
                  transport study, rates three to five times faster               8
                  are desirable and are expected to be achievable by               Hanes, D.M. and D.A. Huntley, 1986. "Continuous
                  replacing the present 8 MHz PC/AT-compatible host                Measurements of Suspended Sand Concentration In
                  computer with a 32-bit 20 to 25 MHz machine.                     a    Wave    Dominated     Nearshore       Environment,"
                  Future developments will include upgrading the                   Continental Shelf Res. 6, 585-596.
                  system with such a machine, and increas-ing the
                  number of data channels.

                  Acknowledgements

                  This work was funded by a Natural Sciences and
                  Engineering Research Council of Canada (NSERC)
                  Group Strategic Grant to AEH and AJB for the
                  RASTRAN Project, and an NSERC Strategic Equipment
                  Grant to AEH for EXADAC. We thank Mesotech Systems
                  Ltd., Rayonics Scientific Inc., and to LeCroy for
                  their assistance and cooperation throughout this
                  project. We thank the technical support staff and
                  graduate students from Dalhousie University and
                  the University of Toronto for their assistance in
                  collecting the data in Figure S. AEH is grateful
                  to DELFT HYDRAULICS for their support                 and
                  hospitality while this paper was being written.

                                         REFERENCES
                  IYoung, R.A., J.T. Merrill, T.L. Clarke, and J.R.
                  Proni, 1982.     "Acoustic Profiling of Suspended
                  Sediments In the Marine Bottom Boundary Layer,"
                  Geophys. Res. Lett. 9, 175-178.
                  2Hay,  A.E.9    1983.    "On   the   Remote     Acoustic
                  Detection      of  Suspended     Sediment     at     Long
                  Wavelengths," J_. Geophys. Res. 88, 7525-7542.
                  3Hess, F.R. and K.W. Bedford, 1985. "Acoustic
                  Backscatter System (ABSS): The Instrument and
                  Some   Preliminary Results, "        Mar.   Geol.     66,
                  357-379.
                  4Libicki, C., K.W. Bedford, R. Van Era III and
                  J.F. Lynch, 1987. "A 3 MHz Acoustic Sediment

                                                                             418

                                                        DESIGN CONSIDERATIONS FOR RASTRAN - SYSTEM 2'

                                                                    D. G. Hazen, A. E. Hay* and A. J. Bowen

                                                   Department of Oceanography, Dalhousie University, Halifax, NS B3H 01
                                            *Physics Department, Memorial University of Newfoundland, St. John's, NF All) 3X7

                                             ABSTRACT                                           et al. (2) have been used successfully by several groups; however,
                         Estimation and prediction of sediment transport on                     they still have the drawbacks of being intrusive, although they
                         the continental shelf is an important problem in fields                are very small, and sampling only at discrete points above the
                         such as fisheries, pollution control, pipeline burial,                 (presumed) location of the bed. Video techniques have been used
                         and well-head maintenance. This paper discusses                        to monitor experiments, but have trouble seeing beneath the top
                         the design of an autonomous, multi-beam, multi-                        of the sediment cloud and measuring distances above the bed.
                         frequency acoustic backscatter suspended sediment                      The acoustic backscatter approach has several advantages over
                         profiler which builds on knowledge gained in deploy-                   other methods in that it is a remote sensing technique. The
                         ing a shore tethered version. This new system will                     instrument is mounted over the area of interest and transmits
                         allow direct measurement of sediment concentration                     high frequency acoustic pulses which are scattered by suspended
                         profiles in the bottom 1m of the ocean at a rate of 10                 particles in the water column.
                         profiles/sec, in bursts, over a 2-3 week deployment.
                         Ancillary data such as flow velocity, temperature and                  The major problems of this approach are:
                         pressure will also be recorded.                                           1. Possible contamination by bubbles and biological scatter-
                                                                                                      ers.
                                        1. INTRODUCTION                                            2. Variations in the speed of sound (and thus time to distance
                                                                                                      conversions) due to temperature changes or high concentra-
                The measurement of suspended sediment near the sea floor is a                         tions of suspended sediment or bubbles.
                problem which has challenged engineers and scientists for sev-                     3. The problems of 'inverting' the backscattered signal to re-
                eral years. Reliable suspended sediment profiles under various                        cover concentration profiles. This requires the ability to
                wave conditions are of primary interest to coastal engineers and                      account for signal losses due to scattering, absorption, and
                geomorphologists as a tool to help understand the mechanics of                        spherical spreading. (Libicki et al. (8) provides a review of
                shoreline dynamics. These profiles may also be used in other                          these problems.).
                conditions to help predict sediment transport rates on the con-                    4. Calibration. Tamura and Hanes (9) provide an illustra-
                tinental shelf. Successful predictions of these rates could in turn                   tion of the difficulties of providing repeatable calibrations
                be used to predict pollution spreading rates or nutrient fluxes for                   of backscatter intensity versus concentration.
                fisheries research.
                Non-acoustic approaches used to measure sediment in suspension                  -Several groups have been working with var       .iou.s types of acous-
                fall into several groups: pumped sampling, sediment traps, opti-                !tic backscatter instruments. Young et al. (10) describes a 3
                cal transmission, optical backscatter, and video. Several of these              MHz acoustic concentration meter (ACM) system, which has
                were reviewed by Huntley (7). Pumped samplers suffer from two                   been used at several locations off the East coast. Hay and Hef-
                problems. The first problem is they sample only from discrete                   fler (4) describe the design considerations for the Acoustic Sus-
                heights above the bed, which can result in undersampling the                    pended Sediment Profiler (ASSP) which was to have been built
                structure of a complex sediment cloud, and the second is the lo-                by the National Research Council of Canada as part of the Cana-
                gistical problems involved in maintaining them over a deployment                dian Coastal Sediment Study (C'S') in 1983-1985. Crickmore et
                lasting several weeks. Sediment traps are useful for determining                al. (1) describes another system which simultaneously measures
                net fluxes but have the disadvantage of being inherently unidirec-              attenuation, backscatter and forward-scatter from a sediment
                tional and ra@se serious questions about flow disturbance. Optical              cloud moving between two pairs of heads. Hanes and Vincent
                transmission devices (transmissometers) have been used success-                 (3) briefly describe a low crst 3 MHz system under development
                fully to measure turbidity in the water column but are also rela-               at the University of East Anglia and Libicki et al. (8) describe
                tively large and, again, flow disturbance becomes a problem near                another 3 MHz system which they have used in the Great Lakes.
                the sea floor. However, they do have the advantage of providing                 All of these systems have the disadvantage of being only single
                an effectively continuous output in a convenient, electronic, form.             frequency devices and therefore requiring a priori assumptions
                Optical Backscatter devices, such as those described by Downing                 about sediment size distributions before further analysis can take
                                                                                                place. They are also limited in the speed and amount of data
                                                                                                which can be gathered and must be tethered to a shore station.
                1RASTRAN Project Contribution No. 2

                                                                   CH2585-8/88/0000- 419 $1 @1988 IEEE

                    Some of the most recent work with acoustic backscatter systems                           -I    ROM
                    is described in a companion paper by Hay et al. (5) which de-                          256K     64K
                    scribes the Remote Acoustic Sediment Transport (RASTRAN)
                    System', developed as part of a joint effort between Memorial                         T
                    and Dalhousie Universities. Hay describes the system as used in            V2, 0
                    .the lab and at two field locations, where it operated tethered to a       MPU                                 _ilp Parallel InterfaceIto Data Logger
                    sfiore-based computer system. This paper describes the plans for
                    RASTRAN- System 2: a self-contained version including data                             sl-
                    loggers, etc. for deployment on the continental shelf for 2-3 weeks                    MPU
                    at a time.                                                                             UP1452                       Detectore
                                                                                                                            Mux
                                      2. THE RASTRAN SYSTEM                                                          A/D             Background
                                                                                                                     ADC816
                    The RASTRAN system is composed of a number of sensor heads                                       I M11.          sensors
                                                                                                                     10 bits         (u, v, P, OBS)
                    (single frequency acoustic sounders), manufactured by Niesotech                                                                 mesotech Hea&
                    Systems Ltd., coupled to a data acquisition and control corn-9uter
                    and sensors for ancillary data. For System 1, these heads were
                    connected by a 300m cable through an envelope detector to a
                    CAMACTIM crate high speed data acquisition system and an AT                   Figure 1 - RASTRAN - System 2 Block Diagram
                    compatible personal computer.
                                                                                             however, will allow a radio link or an interface to the TUDATS
                    The second phase of the project is to design an autonomous ver-          hard wired system (6) to be used instead.
                    sion of the system, capable of being deployed for up to a month
                    at continental shelf depths. As shown in Figure 1, the system            2.1 Sensors
                    will consist of a battery power supply, a Digital Data Acquisition
                    and Control (DDAC) module, and a module to store or transmit             The system will be primarily concerned with acquiring data from
                    the data. The primary focus of this phase of the project is to put       up to four Mesotech Model 810 acoustic sounders. These im-
                    together a system using a data logger. The modular approach,             mersible sounders, as shown in Figure 2, are in an aluminum and

                            @

                               0             0

                                                                                                                                          OW     4 AA46T

                               0
                           A

                                                                                                                                         V

                                                                                                                                             arc

                                               0

                                              @1
                                                                                                                                     ,:I.r.u.d
                                                                                                                                       v,
                                                                                                                                                    Mesoted,

                                                            Figure 2 - Mesotech Model 810 Acoustic Sounder

                                                                                        420

                  polyvinyl chloride (PVC) enclosure. Each contains the high fre-                                                                     /  <      Data
                                                                                                                            DDAC
                  quency circuitry required to transmit a pulse of pre-determined
                  length and amplify the returned (backscattered) signal. The re-                                                                                            Cable
                  turned signal is output on a 455 kHz IF caxrier for the next stage                                                       Temperature                       to Shore
                  of the signal conditioning process. The system uses sounders with                                                      -OBS
                  frequencies of 1.0, 2.25 and 5.0 MHz and beam widths of 2.9' to                                                        - Pressure      <       --t rlare
                  3.6". These sounders were used successfully in System 1.                                                                  Roto@ u, v
                                                                                                                                         - EM u, @
                  The remaining sensors will be used to record ancillary informa                                                         - mrsot@,h Heads
                  tion and obtain independent estimates of sediment concentration.
                  The first of these sensors is a small array of Optical Backscatter
                  (OBS) probes, manufactured by HR Labs for Downing & Asso-
                  ciates. These are the latest version of the probes described by
                  Downing et at. (2) and provide an estimate of suspended sedi-                                           Figure 3 - DDAC Block Diagram
                  ment concentration over a small 1.3 crn' volume, in front of the
                  probe. The OBS probes will be mounted near the cone illumi-
                  nated by the Mesotech heads and will be used as an independent
                  estimate of concentration.                                                           sounders, acquiring ancillary data, conducting data transfers to
                                                                                                       the data logger and controlling power to the A/D converters,
                  Other sensors include pressure and thermistor probes for depth,                      sensors and data logger.
                  wave height, and temperature measurement along with a Marsh-
                  McBirney model 512 electromagnetic current meter, and a slower                       The final part of the digitizer hardware to be described is the sig-
                  response, rotor-type current meter for determination of both                         nal conditioning required to detect the envelope of the received
                  mean currents and wave orbital velocities.                                           signal. Two alternatives have been designed and tested. The sim-
                                                                                                       pler design is for a rectifier detector which follows the envelope
                  2.2 The DDAC Module                                                                  of the amplitude modulated (AM) IF signal from the Mesotech
                                                                                                       heads. The disadvantage of this design is it loses phase informa-
                  The Digital Data Acquisition and Control module, as shown in                         tion which may be of interest in attempting to recover velocities
                  Figure 3, is responsible for both digitizing data streams from                       from Doppler shifts in the returned signal. The other, more com-
                  the various sensors and controlling other devices in the system.                     plex, design is a synchronous demodulator which preserves phase
                  The DDAC is built around a number of cards on a STD bus sys-                         but requires the application of modulus function at some later
                  tem. The system includes an 8MHz CPU, 256k RAM, Real Time                            stage in the process for simple backscatter calculations. (The
                  Clock, 64 k EPROM, and a custom digitizer board. The STD bus                         amplitude modulated signal is, in effect, "over modulated" with
                  system is capable of being placed in a low power "sleep" mode                        the amplitude of the signal occasionally exceeding that of the
                  to reduce battery drain. The control program will be written in                      carrier). We have not yet decided which design is best for our
                  C, compiled and stored in EPROM.                                                     application.
                  The digitizer board is designed around a slave microprocessor                        The sampling program, as shown in the modified Warnier-Orr
                  and a very high speed Analog to Digital (A/D) converter module,                      diagram in Figure 4, after initialization, consists of running re-
                  capable of 1 Msamples/sec. The actual speed required is 200k                         peated sampling bursts on an hourly basis. Data is sampled in
                  samples/sec for each of the four Mesotech heads to preserve the                      bursts because the system cannot log (or process) the data fast
                  100 kHz signal bandwidth. Data from the A/D converter is trans-                      enough to maintain continuous sampling for over 15..minutes.
                  ferred via Direct Memory Access (DMA) to a buffer in RAM. The                        In addition, continuous sampling would shorten the deployment!
                  slave processor is an Intel UP1452 running at 16 MHz, executing                      length of the system dramatically.
                  assembly language code stored in EPROM. The slave processor
                  also acts as an intelligent 1/0 controller, triggering the Mesotech
                                                                                                                                 - Run 10 profiles
                                                                                                                                   (< 10ms each)
                                                                                                                                 - compile avg. profile
                                                                                                     Acquire profile            -  (Apply inversion
                                                                     - Power up A/D, etc.          - Read OBS                     algorithm)
                                                                     - Acquire data at             - Acquire ancillary            Bin average profile
                                         Power up                      5-10 Hz for                   data (every 2nd
                                         initialization                - 15 min                      time through)
                                         Sampling cycle              - Store data                  - Store in RAM
                                         (loop time                    from buffer to                buffer
                                            1 hr)                      data logger                 - Wait for next pass
                                                                     - Go to 'sleep' until
                                                                       next burst

                                                                            Figure 4 - DDAC Program Flow

                                                                                                421

                     The sampling bursts consist of gathering sets of 5 to 10 pings and                                 4. ACKNOWLEDGEMENTS
                     ensemble averaging them to produce 10 averaged profiles per sec-
                     ond. It is hoped that by sharing the tasks between the master                   The work on the RASTRAN project, Systems I and 2, has been
                     and slave processors, inverting and bin averaging the data can                  funded by a Natural Sciences and Engineering Research Coun-
                     also be done in real time. In addition, data from the OHS probes                cil of Canada (NSERC) Strategic Grant. Figure 2 is provided
                     will be acquired at 10 samples/sec and the other ancillary instru-              courtesy of Mesotech Systems Ltd. of Port Coquitlam, BC.
                     ments at a lower rate of 2.5 or 5 samples/sec. This data is stored
                     in RAM until the buffer is full. The buffer fills in approximately                                       5.REFERENCES
                     15 minutes. At this stage, sampling is stopped and the A/D and                    1. Crickmore, M.J., I.E. Shepherd and P.M. Dore, 1986. "A
                     sensors powered down. The master CPU then performs any re-                           Field Instrument for Measuring the Concentration and Size
                     maining processing required and transmits the buffer through the                     of Fine Sand Suspensions" Proceedings of the International
                     slave to the data logger. When the data has been transferred,                        Conference on Measuring Techniques of Hydraulics Phe-
                     the system goes into a low-power "sleep" mode until the next
                     sampling burst is required.                                                          nomena in Offshore, Coastal & Inland Waters, p. 425-442.
                                                                                                          Bedford, U.K.: BHRA, the Fluid Engineering Centre.
                     2.3 The Data Logger                                                               2. Downing, J.P., R.W. Sternberg and C.R.B. Lister, 1981.
                                                                                                          "New Instrumentation for the Investigation of Sediment
                     The data logger is being designed around a 240 Mbyte Write                           Processes in the Shallow Maxine Environment", Marine Ge-
                     Once-Read Many (WORM) optical disk drive, as shown in Fig-                           ology 42, 19-34.
                     ure 5. This drive has higher capacity and fewer moving parts                      3. Hanes, D.M. and C.E. Vincent, 1987. "Detadled Dynamics
                     than conventional 1/4 inch tape cartridge systems. The drive is                      of Nearshore Suspended Sediment", Proc. Coastal Sedi- .
                     controlled by a PC bus controller card which, in turn, is con-                       ments '87,285-299. New York: ASCE.
                     nected to a low power PC compatible system on a passive PC                        4. Hay, A.E. and D. Heffier, 1983. Design Consideration for
                     bus backplane. Details on the design will be reported in a future                    an Acoustic Sediment Transport Monitor for the Nearshore
                     paper as the design matures.                                                         Zone, Report C2S24, 37 pp. Ottawa: National Research
                                                                                                          Council Canada.
                                                                                                       5. Hay, A.E., L. Huang,      E.B. Colburne, J. Scheng and A.J.
                                                                                                          Bowen, 1988. "A High Speed Multi-Channel Data Acqui-
                                                                                                          sition System for Shore-based Acoustic Sediment Transport
                        V401                256k                Parallel                                  Studies", Proc. Oceans '88, Companion to this paper.
                         CPU                RAM                1/0                                     6. Hazen, D.G., D.A. Huntley and A.J. Bowen, 1987.
                                                                                  to DDAC                 "UDATS: A System for Monitoring Neaxshore Processes",
                                                                                                          Proc. Oceans '87, 993-997.
                                                                                                       7. Huntley, D.A., 1982. In Situ Sediment Monitoring Tech-
                            J                                                                             port C2S2-1, 35 pp. Ottawa: National Research Council
                                                                                                          niques: A Survey of the State of the Art in USA, Re-

                       Disk                    WORM      Drive                 WORM                       Canada.
                                                                                                       8. Libicki, C., K.W. Bedford, R. Van Era III and J.F. Lynch,
                       256k                    Controller                      Drive                      1987. "A 3 MHz Acoustic Sediment Profiling System",
                                                                                                          Proc. Coastal Sediments '87, 236-249. New York: ASCE.
                                                                                                       9. Tamura, T. and D.M. Hanes, 1986. Laboratory Calibration
                               Figure 5 - WORM Drive Data Logger                                          of a 3 Megahertz -Acoustic Concentration Meter to Measure
                                                                                                          Suspended Sand Concentration, Technical Report 86-004,,
                                                                                                          87 pp. Miami: University of Miami, Rosensteil School of
                                              3. CONCLUSIONS                                              Maxineand Atmospheric Science.
                                                                                                       10. Young, R.A., J.T. Merrill, T.L. Clarke and J.R. Proni, 1982.
                     The design work on RASTRAN-Systern 2 is progressing. The                             "Acoustic Profiling of Suspended Sediments in the Maxine
                     new system will allow the simultaneous          acquisition of profiles              Bottom Boundary Layer", Geophysical Research Letters,
                     from up to four acoustic sounders operating at three different.                      9(3), 175-178.
                     frequencies at a rate of approximately 10 profiles/sec. This data.
                     will be stored, along with that from ancillary sensors, on a high
                     capacity data logger over a 3 to 4 week deployment. RASTRAN
                     - System 2 will be a significant advance over existing systems in
                     terms of both the speed and storage capacity of the data collec-
                     tors and the number of acoustic sounders which may be attached
                     to the system.
                     The development plan is for bench testing by January 1989 and
                     deployment as part of the instrument array at the Stanhope '89
                     experiment in October-November 1989 at Stanhope Lane, P.E.I.
                     The significant problems remaining are those of interpreting the
                     data and inverting the backscatter profiles to obtain concentra-
                     tions.
                                          @
                                               6k

                                                M
                                              A               @@to DDAC

                                                                                               4@2

                                                     MINI-PROBES: A NEW DIMENSION IN OFFSHORE IN SITU TESTING

                                                                                       I

                                                                   Alan G Young, Lowell V. Babb, Ronald L. Boggess

                                                                                       Fugro-McClelland Inc.
                                                                                       Houston, Texas

                                                ABSTRACT                                                              HISTORICAL PERSPECTIVE

                                                                                                   In an earlier publication on Underwater Soil Sampling,
                   Acquiring geoscience data about the near-seafloor sediments                     Professor I. Noorany predicted that "the practice of under-
                   is fundamental to using this natural resource. Tradition-                       water sampling and testing is presently in a state of flux
                   ally, gravity corers have been used to sample the ocean                         and there is much promise orl%veloping better and more
                   sediments.    Sample recovery is usually very shallow unless                    efficient systems in the future.  "       In reviewing how this
                   special purpose, expensive systems are deployed. Acquiring                      technology has evolved since he made this prediction, the
                   in situ data using push-in probes has been developed in                         efficient systems he predicted are now available.
                   recent decades. Existing probes are approximately 3.5 cm in
                   diameter and require deployment of large seafloor mechanisms                    The evolution of geotechnical sampling methods and in situ
                   (10,000-20,000 kg)       to achieve significant penetrations.                   testing devices used offshore today is important in under-
                   Use of such devices from inexpensive vessels is generally                       standing today's technology and in developing an apprecia-
                   not practical.                                                                  tion of how much progress has been made in the area of geo-
                   Recent development of a series of miniature             probesis                technical investigations since the mid-70's and early 80's.
                                                                                                   Basically, the development of the equipment available today
                   described. Because of the small probe size, pushing mecha-                      evolved through the activities of three different groups:
                   nisms are also scaled down (1,000 kg typical). Handling                         (1) Oceanographic and Geologic Research Centers, (2) Naval
                   equipment onboard oceanographic research vessels is suitable                    Research Centers, and (3) Geotechnical Engineering Service
                   for deployment of the self-contained mini-probe systems.                        Companies.
                   Installation of the systems on remotely-operated-vehicles
                   also appears feasible.      Penetrations to 12.2 m have been                    The methods of operation used for geoscience sampling and
                   achieved.                                                                       in situ testing employed today depend upon whether the
                                                                                                   system is to be deployed downhole or used in a seafloor mode
                                             INTRODUCTION                                          of operation. The mode of operation in turn depends upon
                                                                                                   the depth of interest for the particular application or
                   There are a large variety of marine activities planned for                      need.    For deep penetrations (greater than 10 m), downhole
                   the U.S. Exclusive Economic Zone and other oceanic areas                        sampling and in situ testing are performed in conjunction
                   that will require geological and geotechnical data to                           with drilling equipment.       For shallow penetrations (less
                   describe the properties of the seafloor sediments. The data                     than 10 m), self-contained units or equipment mounted on a
                   requirements will vary from only a few meters for small                         tethered seafloor platform or submersible vehicle is most
                   shallow foundations and cables to depths to 200 m for deep                      widely used.
                   foundations such as the piles supporting massive offshore
                   platforms. There are a number of different methods depend-                      Since 1947, when the first geotechnical investigations were
                   ing upon the depth of interest and water depth to acquire                       performed from temporary platforms in about 6 m of water for
                   these data at the site for the proposed activity.                               the U.S. petroleum industry, improved technology has evolved
                                                                                                   that has allowed drilling and sampling to be performed from
                   Traditionally, geological and geotechnical data were ob-                        vessels that can accommodate the move into deeper water.
                   tained by performing laboratory tests on samples acquired by                    Anchored barges eventually took the place of the temporary
                   a self-contained gravity sampler or a downhole sampler oper-                    platforms and were used extensively until 1962 when a port-
                   ated through the bore of a drill pipe advanced by a rotary                      able drilling rig was first mounte        n an oilfield supply
                   drilling rig.  In the last decade, there has been much                          vessel, as described by McClelland.M
                   greater reliance on in situ testing devices that can be
                   deployed from seafloor platforms, submersibles, or used with                    The shift to water depths greater than 200 m, the difficult
                   traditional drilling equipment. The purpose of this paper                       logistics associated with anchoring, and the increased use
                   is to describe a new "concept" and system available for                         of specialized in situ testing equipment brought forth, in
                   performing in situ testing which overcomes many of the dif-                     the mid-1970's, the use of dynamically-positioned geotechni-
                   ficulties of previous systems. A primary advantage of the                       cal drill ships such as. the M.S. Bucentau . In some cases,
                   new system is that now a small oceanographic vessel can                         oilfield drilling vessels have been used for geotechnical
                   deploy the equipment, allowing more widespread and cost-                        investigation; however, high operational costs have fre-
                   effective collection of geoscience data.                                        quently caused this to be a prohibitive option.

                                                                     CH2585-8/88/0000- 423 $1 @1988 IEEE

                    The most inexpensive method for obtaining samples of marine                                                                BASIC CONCEPT
                    sediments has been the self-contained tool such as the
                    gravit.j (or drop) core sam@@jr as described by Hvorslev                         and         Examples of a standard-sized probe and a mini-probe are
                    Steton 3) and Kullenberg.                 Most of these samplers are                         shown in Figure 1. The mini-probe is 1.27-cm-diameter and
                    limited to penetration depths of 10 m or less. However, a                                    the larger probe is 3.55-cm-diameter.                   Both probes are
                    deepsea gravity corer has been constructed in sizes capable                                  called friction cone penetrometers. Each contains two load
                    of obtaining "Tples up to 45 m in length as described by                                     cells that measure resistance to penetration as the tool is
                    Hollister et al.                                                                             pushed into the soil. Two measurements, the tip resistance
                                                                                                                 and the sleeve friction, are recorded continuously as the
                    A number of sampling and in situ testing systems that would                                  Orobe is pushed into the seafloor sediments. By analyzing
                    operate from either tethered platforms or submersibles were                                  the tip and sleeve data as a function of depth, valuable
                    developed in the 1950's and 1960's. Tethered platforms yg1d                                  information on the sediment behavior can be determined.
                    for sampling include: (1) the U.S. Navy's                         TIPOS,
                    (2) the University of Rhode I@IqRd's DOSP,R?the Dutch                                        The data signals are usually recorded on a PC-compatible
                    Geological Survey's Woff II.                   The Lehigh University's                       computer. Plots of the tip and sleeve data versus penetra-
                    Underytter Tower,                  and Woodward-Clyde Consultants'                           tion can be generated in the field.
                    MITS(I        were tethered platforms that had the capability to
                    perform in situ vane and cone penetrometer testing.                                          Probes like the above example are connected to a thrusting
                                                                                                                 rod which is jacked into the soil. Most thrusting rod
                    In situ testing equipment operated from a deepsea submers-                                   systems are composed of one-meter long threaded connecting
                    ible that was        e-. geloped during the samt,4Y       eriod included:                    rods.    These rods are made up as the probe penetrates or a
                    (1) UL      I -Z@,         (2) the Deep Quest,              and (3) the                      pre-strung length of rods is supported by a guideline
                    AlvinvW
                                 Geise and Kolk describe a system that can be used                               system. The new mini-probe thrusting rod is formed by a
                    from a manned submersible to perforr@,T situ testing and                                     continuous long rod which is coiled as shown in Figure 2.
                    sampling to seafloor penetrations of 1 m.

                    A wide variety of seafloor testing systems were developed in
                    the 1970's that allowed in situ testing to be performed to
                    penetrations up to 35 m.               In situ vane testing and cone
                    penetrometer testing were performed with systems as follows:
                    (1) McClelland's Stingray, (2) Fugro's Seacalf, (3) Fugro's
                    Seasprite, (4) McClelland's Starfish, (5) Fugro's Seaclam,
                    and (6) McClelland's Halibut. These systems, developed                                                                                                           N
                    primarily for the geotechnica             troleum industry,         ve
                    been docume?61 by Young, 11% Ndberg, a al,                                                                                                                                  _J
                    Young et al,          and McClelland. 11-03                                                                                                                       S,

                    In more recent years, improved equipment for tethered plat-
                    forms was developed that would allow in situ testing to be
                                                                                                                                                                                  i2_    @,,,r%
                    performed in deepwater. The XSP-40 was developed and tested
                    by the Naval Civil Engineering Laboratory capable of per-                                                                 offl,  A
                    forming tests to 12-m ftq@h.                In 1984, the SEALION as
                                                                                                                                           V
                    described by van der Wal               was developed and tested by the
                    Netherlands Council of Oceanic Research. It could be oper-
                    ated as an automated piezoeone probe system in water depths
                    up to6,000m. The system was designed to perform tests to
                    seafloor penetrations up to 5 m.
                                                                                                                                                            -7

                                          7
                                                               72-
                                                                                                                                                                             Ne 4@rl@
                                                         9F
                                                     eo
                                                                                                                 FIGURE 2.       COILED THRUSTING ROD AND MINI-PROBE

                                                                                                                 The thrusting rod is inserted into a hydraulic ram jacking
                                                                                r
                                                                                                                                                                                        -probe
                                                                                                                 system. By actuating a rod chucking device, the mini
                                                                                                                 rod is straightened and thrust into the soil. At the con-
                                                 AX:
                                                 All
                                                                                                                 clusion of a push, the chucking mechanism is reversed and
                       & "r, f          @0,@Jypk@e jKi-pr,
                                                         ego,
                                                                                                                 the rod is jacked out of the soil and re-coiled. The
                        @A* --J W,;61                      RJ
                        A,_                  -4-           Ar                                                    thrusting unit is shown in Figure 3.

                                                                                                                 The major advantage of the mini-probe system is its compact
                                                                                                                 size.    Since the probes and rod are small, the force and
                                                                                                                 reaction weight required to penetrate the soil are also
                                                                                                                 small. A typical system weighing 1,000 kg has penetrated as
                                                                                                                 deep as 12.2 m. In certain soils, penetrations exceeding
                                                                                                                 18 m are projected. An added benefit of the small size is
                                                                                                                 the low power requirement which makes battery-powered
                    FIGURE 1. CONE PENETROMETERS: MINI-PROBE AND                                                 syste ms quite feasible.
                                   STANDARD SIZE UNITS

                                                                                                            424

                                                                                                                                        , _7
                                                                                                                                              _Vf @J

                                                                                                                                     01

                                                                           @A

                                                                                                             -PROBE SYSTEM MOUNTED ON 4-WHEEL
                                                                                          FIGURE 4.     MINI
                                                                                                       DRIVE LIGHTWEIGHT TRUCK

                FIGURE 3. MINI-PROBE THRUSTING UNIT WITH
                             20-FOOT ROD                                                                 NAUTILUS CONE PENETRATION TEST

                                                                                                       MINT RESISTANCE @-                  15,
                The major disadvantage of the mini-probe system, compared to                PENETRA7[ON     200      400      600      Sao         RATIO
                                                                                           FE@T         UIE FR@MO@ I - - -                 @SF     , ,
                standard-sized probes, is limited penetration. This limita-                        0                 10       15       20          2 4 %6 8
                tion is related to the inherent stiffness of the thrusting
                rod.   While standard systems have penetrated in excess of
                90 m, the maximum mini-probe penetration is expected to be
                18 m.                                                                                       ------

                                   MINI-PROBE VARIATIONS

                The example mini-probe described above is but one variation
                                                                                                                                                   n
                of available probes. Additional probes have been developed.

                The piezocone penetrometer measures the pressure of the pore
                fluid in the formation. Combining the pore pressure and tip
                resistance data can improve the determination of soil type.
                The standard-sized pie@yTnes have been in widespread use
                since the late 1970's.         Miniature versions are now
                available.
                                                                                                            7;
                                                                                                  25
                Mini-probes have also been designed to acquire soil vapor
                samples. This device requires a vacuum that is generated at
                the ground surface to pull vapor samples from the soil.
                This mini-probe is widely used in the investigation of                            30
                hazardous waste sites. A modification of this probe allows
                the collection of a pore fluid sample for chemical analysis.

                                                                                                  35
                A probe to measure acoustic properties of the soil is
                presently under development. Another mini-probe to measure
                soil resistivity has been conceived. Many other types are
                possible and will allow exploitation of the mini-probe tech-                      40
                nology.

                           MINI-PROBE DEPLOYMENT SYSTEMS
                A mini-probe system deployed on the front of a small four-                FIGURE 5. EXAMPLE DATA PLOT
                wheel drive truck is shown in Figure 4. Three vehicles of
                this type are in daily operation in the U.S.A. Primary uses
                of the truck-mounted mini-probe systems are vapor sampling                A mini-probe system has also been mounted on the flotation
                and friction cone penetrometer testing. An example of cone                vehicle shown in Figure 6. In this application, 180 sepa-
                penetrometer data is shown in Figure 5. Data from the tip,                rate coff )tests were performed along a chain of barrier
                sleeve, and friction ratio are presented as a function of                 islands. 5     Because of the vehicle's configuration and
                depth of penetration.                                                     light weight, it could be towed between the islands. A

                                                                                       425

                   question that often arises concerns the fatigue life of the                By incorporating self-contained data recording and hydraulic
                   coiled rod.   For this project, about 170 tests were per-                  power systems, the Nautilus can be deployed in even deeper
                   formed with the same rod.                                                  water. A single line mechanical cable can be used to deploy
                                                                                              the system from small oceanographic research vessels as
                                                                                              illustrated in Figure 8.   Alternately, a deepwater mini-
                                                                         IF                   probe can be installed on a remotely-operated-vehicle (ROV).
                                                             4P W,I      Jp                   This concept is shown in Figure 9. The benefits of this
                                                                                 Z5
                               A;  S                                                          application are use of the ROV's data and power systems and
                                                                  "'A
                               If                                                             some
                                y                                                                  manueverability independent from the mother ship.

                     @(-r 4
                                                                                                              Handling
                                                                                                                                    Hoisting
                                                                                                              Frame
                                                                                                                                    System

                                                                         v

                                                                                a

                   FIGURE 6. MINI-PROBE SYSTEM MOUNTED ON A
                               FLOTATION VEHICLE

                   In water depths of approximately 30 in, a mini-probe system
                   has been waterproofed and installed on a submersible plat-
                   form. This device, called Nautilus, is shown in Figure 7.                                           Nautilus
                   In this configuration, hydraulic power is provided from the                       A
                   surface through adualhose. Data signals are transmitted
                   to the surface on an electrical cable. Ballasting the
                   system is accomplished by varying the quantity of lead
                   weights.   This device has most often been deployed from a
                   floating barge.                                                                               Geotechnical Probe

                                                                                              FIGURE 8. DEPLOYMENT OF A MINI-PROBE SYSTEM FROM
                                                                                                          AN OCEANOGRAPHIC RESEARCH VESSEL

                                             &

                                                                                                                                                    VIDEO CAMERA

                                                                                                REMOTELY                                         MANIPULATOR ARM
                                                                                                OPERATED
                                                                                                VEHICLE

                                                                                                               MINI-PROBE
                                                                                                               MECHANISM

                                                                                              FIGURE 9. MINI-PROBE INSTALLED ON A
                                                                                                          REMOTELY-OPERATED VEHICLE

                   FIGURE 7. SHALLOW WATER MINI-PROBE SYSTEM

                                                                                          426

                                            CONCLUSIONS                                        10. McClelland, B. and Ehlers, C.J., "Offshore Geotechnical
                                                                                               Site Investigations." Chapter 9. Planning and Design o
                 The patented mini-probe systems show           great promise for              Fixed Offshore Platform . B. McClelland and M.D. Reifel,
                 extending the use of in situ soils data. The high cost of                     Eds. New York: Van Nostrand Reinhold Co., 1986,
                 operating dynamically-positioned vessels to support drill-                    pp. 224-265.
                 ing, sampling, and testing activities will limit the oppor-
                 tunities to acquire geoscience data in deepwater areas'                       11. Noorany, I. Underwater Soil Sampling and Testin , San
                 because of the high daily costs. Project cost savings can                     Diego State College, San Diego, California, 197 1.
                 be particularly realized in the frontier deepwater environ-
                 ment through the use of small oceanographic vessels.                          12. Ibid, p. 12.
                 The new system offers many advantages over previous systems                   13. Ibid, p. 13.
                 including:     (1) deployment from any type of vessel,
                 (2) rapid repetition of testing from site to site, and                        14. Noorany, I. "Offshore Sampling and In Situ Testing:
                 (3) rapid dismantling and transportation to any area of the                   1981 Update." Updating Surface Soundings. 1985.
                 world.                                                                        15. Preslan, W.L., Lourie, D.E., and Boggess, R.L. "A Cone
                 Although the depth of penetration is limited compared to                      Penetrometer for Beach Reconnaissance." Proceedings.
                 much larger predecessors, widespread use of the tool is                       Beagh Preservation Technology conference. Gainesville, FL.
                 expected to cover a majority of the research and technical                    March 23-25, 1988.
                 requirements for the activities planned in many marine
                 areas. Any activity requiring knowledge of the seafloor                       16. Richards, A.F., McDonald, V.J., Olson, R.E., and Keller,
                 sediments to depths approaching 18 m can benefit from this                    G.H. "Under-water Soil Sampling, Testing, and Construction
                 new technology.                                                               Control." Special Technical Publication 501. American
                                                                                               Society for Testing and Materials, Philadelphia, PA, 1972.

                                                                                               17. van der Wal, J., Bergen Henegouw, C. van, Hoogendoorn,
                                                                                               H.G. and Richards, A.F. "Sealion: A Snellius-II Expedition
                                                                                               Automatic System for In Situ Geotechnical Testing in Water
                                                                                               Depths of 6000 m." Oceanology. London: Graham and
                                           BIBLIOGRAPHY                                        Trotman, 1986, pp. 241-246.
                                                                                               18. Young, A.G "Marine Foundations." Chapter 14. The
                 1. Geise, J.M. and Kolk, H.J. "The Use of Submersibles for                    Handbook of Coastal and Ocean Enpaineering. J. Herbich, Ed.
                 Geotechnical Investigations." The Design and Operation of                     Houston: Gulf Publishing Co., 1989.
                 Underwater Vehicles. Undon: Society for Underwater Tech-                      19. Young, A.G, McClelland, B., and Quiros, G.W. "In Situ
                 nology, 1983, P. 13.                                                          Vane Shear Testing at Sea." Presented at the ASTM Inter-
                 2. Hollister, C.D., Silva, A.J., and Driscoll, A. "A Giant                    national Symposium on Laboratory and Field Vane Shear
                 Piston-Corer." Journal of Ocean Engineering. Vol. 2, 1973,                    Strength Testing, Tampa, FL, 1987.
                 pp. 159-168.                                                                  20. Zuidberg, H.M. and Richards, A.F. "Sampling and In Situ
                 3. Hvorslev, M.J. and Stetson, H.C. "Free-fall Coring Tube;                   Geotechnical Investigations Offshore." First Shanghai
                 A New Gravity Bottom Sampler." Bulletin, Geological                           Symposium on Marine Geotechnology and Nearshore/Offshore
                 Society of America. Vol. 57, 1946, p. 935.                                    Structures. Claney, R.C. and Farg, H.Y., Eds. Special
                                                                                               Technical Publication, American Society for Testing and
                 4. Inderbitzen, A.L. and Simpson, F. "A Study of the                          Materials, 1986.
                 Strength Characteristics of Mining Sediments Utilizing a                      21. Zuidberg, H.M., Schaap, L., and Beringen, F. "A Pene-
                 Submersible." Special Technical Publication 501. American                     trometer for Simultaneously Measuring Cone Resistance,
                 Society for Testing and Materials, Philadelphia, PA, 1972,                    Sleeve Friction, and Dynamic Pore Pressure." Penetration
                 pp. 204-215.                                                                  Testin . Proceedings of the Second European Symposium on
                 5. Inderbitzen, A.L., Simpson, F., and Gross, G., A Compari-                  Penetration Testing, ESOPT 11, Amsterdam, May 24-27, 1982,
                 son of In Situ and Laboratory Vane Shear Measurements.                        pp. 963-970.
                 Lockheed Ocean Laboratory Report 681703, Lockheed Missile
                 and Space Company, 1970.

                 6. Kullenberg, B. Deep-sea Coring. Swedish Deep-Sea Expe-
                 dition Report No. 4, 1955,,p. 35.

                 7. Lambert, D.N., "Submersible Mounted In Situ Geotechnical
                 Instrumentation." Geo. Mar. Let . Vol. 2, 1982, pp. 209-214.

                 8. Lewis, L., Nacci, V., and Gallagher, J. "In Situ Inves-
                 tigations of Ocean Sediments." Proceedings, Civil Engineer-
                 ing in the Oceans 11, ASCE Conference, Miami Beach, FL,
                 December 10-12, 1969.

                 9. McClelland, B. "Techniques Used in Soil Sampling at
                 Sea." Offshore. Vol. 32, No. 3, March 1972, pp. 51-57.

                                                                                          427

                                         BOUNDED BEAM TRANSMISSION ACROSS A WATERISAND INTERFACE,
                                                                EXPERIMENT AND THEORY

                                                             K. L. Williams and L. J. Satkowiak

                                                              Naval Coastal Systems Center
                                                          Physical Acoustics Branch, Code 2120
                                                               Panama City, FIL 32407-5000

                                        AB STRACT                              solid layers.
                 A series of measurements were made to investigate the         The predictive capabilities of the SAFARI program were
                 effect of a water/sediment interface on a propagating         tested as part of an experiment designed to examine
                 acoustic signal. Under nearly laboratory conditions           the effect of a water/sediment interface on the
                 data were collected mapping out the sound pressure            propagation of both linear and parametric beamS.4 In
                 field in a homogeneous sand sediment for a 20 kHz             the following, we first describe the experimental
                 linear source. The data were taken at grazing angles          arrangement and data reduction methods in Section 11.
                 that ranged from well-above to weil-below the critical        in Section 111, we present a brief overview of the
                 angle for the sediment. Based on data collected, in-          theoretical underpinnings of the SAFARI program and
                 sediment pressure field contours were obtained. These         -its implementation in the present work. Then, in
                 contour plots are compared with theoretical                   Section IV, we compare the SAFARI and experimental
                 predictions calculated using the SAFARI model (H.             results and in Section V we conclude.
                 Schmidt and F. B. Jensen, J. Acoust. Soc. Am., 77, 813-
                 825 (1985)). Agreement between SAFARI and                                         11. EXPERIMENT
                 experimental pressure field contours represent an
                 experimental confirmation of the SAFARI code.                 'The measurements were made under nearly laboratory
                                                                               conclitions at the Admiralty Research Establishment
                                                                               ,Bincleaves Acoustic Range tank facility in the United
                                                                               Kingdom. A schematic of the facility is given in Fig. 1.
                                                                               The 10m x 3m x 2m tank consisted of a steel frame with
                                                                               fiberglass walls. The tank itself was level to within 30
                                                                               over its entire length. The transducer mounting
                                                                               allowed complete control over the height of the array
                                    1. INTRODUCTION                            and the direction it was pointed. The transducer was
                                                                               mounted on a full tilt-and-pan mechanism that gave
                 The propagation of acoustic energy across water/              angular accuracy to within 0.30. The tilt-and-pan
                 sediment interfaces is of interest in any situation where     mechanism was attached to the bottom of a remotely
                 one wants to examine sub-bottom features. The use of          controlled telescoping arm (which was accurate to
                 the plane wave transmission coefficient to characterize       within 0.3 cm). The telescoping arm mechanism was
                 this propagation suffers from one fundamental flaw-           attached to a platform that allowed forward,
                 real transducers are not infinite in extent. ;Th@             backward, left, and right movement. The platform
                 bounded nature of real transducers implies that there is      was able to move 5 meters in a given direction with an
                 a spectrum of plane wave components incident onto             accuracy of about 0.5 cm. The versatility of the
                 the water/sediment boundary in any experimental               positioning system allowed one to "point" the acoustic
                 arrangement and it is useful to have knowledge of the         beam very accurately. it was felt that the location of
                 transmitted field structure as well as the transmitted        the center of the acoustic beam on the surface of the
                 level. The theoretical methods needed to attack this.         sedimentwas known to within 5 cm.
                 problem have been known for many years.1 However,
                 the mathematics is rather involved and if one desires an      Eighteen in-sediment hydrophones and one in-water
                 extension to cases where there are sediment layers            hydrophone were employed in the experiment. The
                 analytical analysis quickly becomes infeasible.               hydrophones were 2.2 cm ceramic spheres with a
                                                                               nominal sensitivity of -202 dB're IV/pPa. The beam
                 Recently, the analytical methodology of Ref. 1  hasbeen       patterns from each hydrophone indicate nearly
                 implemented numerically.2.3 This Seismic and Acoustic         symmetric response.     The in-sediment hydrophones
                 Fast-field-program for Range Independent                      were held in position by a lattice of quarter inch kevlar
                 environments (SAFARI) is a full wave solution which           ropes secured through holes drilled in the sides of the
                 allows an arbitrary number of layers (the version used        tank. The divers were able to adjust the hydrophones
                 allows up to 24 layers) each of which,may be a vacuum,        both laterally and vertically to within 1 cm of their
                 an attenuating liquid, or a viscoelastic solid. An            planned positions. Acoustic ranging was used to verify
                 amplitude and phase shaded vertical array of                  the hydrophone positions (Ref. 5). The tank was then
                 compressional sources may be placed in the liquid and         carefully filled with a well sorted sand of 250 micron

                                                                          428 United States Government work not protected by copyright

                    diameter and leveled by careful scraping. The surface                                        where
                    of the sand was visually inspected periodically by
                    trained divers and leveled as needed (diver                                                                                         2         2
                    measurements indicated the water/sand interface was                                                                           (V +h
                    within 10of horizontal).
                    The data were taken utilizing th.e HP 101/102                                                                                    V + k        2)A =0
                    transducer5 which was driven linearly utilizing a 4-cycle                                                                                     nn
                    sinusoid signal from an HP-3314A signal generator                                                                                             2
                    amplified by an ENI 1140A power amplifier. The 20 kHz                                                                               2         WPn
                    beam generated had a beam width of about 200 with                                                                                h  n         + Pn
                    sidelobes that were about 35 clB down from the main                                                                                           n
                    lobe and located at 25o off the main lobe. The sound
                    pressure level (SPQ of the transducer was measured                                                                                  2         W2Pn
                    using the in-water hydrophone located on the                                                                                        k
                    landward side of the tank. The SPL was measured to be                                                                               n         Pn
                    171 clB (rel 1pPa) at a range of 4.7 meters,                                                                                                                                  (2)
                    approximately the transclucer-to-secliment distance
                    that was maintained during data acquisition. By                                              In these equations, Xn, Pn, and Pn are the LamO
                    utilizing the two buried hydrophones at the landward                                         constants and density of the nth layer, and w is the
                    side of the tank the se iment sound velocity was                                             radial frequency. (Note that (Dn and An, being solutions
                    measured to be 1677 m/s with an attenuation of 9.8                                           of the homogeneous wave equation, don't include
                    dB/m.                                                                                        contributions from any point sources.                                       These
                                                                                                                 contributions are handled separately3 as discussed
                    The in-sediment sound field data were taken by                                               below).
                    illuminating the central probe field at a selected angle,
                    then by shifting forward and backward (maintaining                                           Use of the Hankel transform then allows one to obtain
                    the same incident angle), the sound pressure field in                                        integral representations of the potentials in terms of
                    the sediment was "mapped" oUt.4 The signal from a                                            up and down propagating conical waves
                    given hydrophone was amplified (Tektronix 502
                    Differential Amplifiers), filtered (Krohnhite (3202)),
                    averaged and digitized (Nicolet 4096B with a 4562                                                                                   _C'       (8) Z
                    digitizer plug-in), and stored (HP9826). The in-                                                           (r, z)         A   We     n        + A + (s)ea"( 8) z sd (rw) ds
                    sediment sound pressure levels were determined from                                                                                                 n              1)
                    the measured peak-to-peak voltages accounting for
                    individual transducer sensitivity and amplifier gains.
                    From the discrete point sound pressure levels, pressure                                                A,(r,z)=           B   We - On(s) z + B + Weprz(s @'31 .4 (m) ds
                    contour lines were extracted using WAR routines6 that                                                                                               n              0         (3)
                    fit the data with splines under tension. The data
                    presented will be in the form of equal sound pressure                                        where
                    level contour lines.

                                                      111. SAFARI                                                                                 a (S) = VS      2 _   h2
                                                                                                                                                     n                  n
                    The SAFARI program is a numerical implementation of
                    the method described by Ewing, et. al.1 This section                                                                          On(s) = %IS     2 _   k2
                    gives a brief description of the concepts used in SAFARI.                                                                                           n
                    The reader is referred to Refs. 1-3 for a more complete                                      and s is the horizontal wavenumber and the
                    discussion including the numerical implementation                                            coefficients
                    technique.                                                                                                                    A     A+,B-,B+
                    The medium to be examined consists of n horizontally                                                                                                                         (4)
                    stratified layers which are isotropic, homogeneous, and                                      are functions of s.
                    viscoelastic. Time harmonic compressional sources
                    located at the r = 0 position of a cylindrical coordinate                                    A solution for the total potential in any layer requires
                    system r, 0, z are allowed. The particle displacements in                                    that the field produced by all the sources in that layer
                    the nth layer can then be written in terms of                                                be included. For any compressional source at r = 0, the
                    displacement potentials (Pn, An as                                                           potential produced in an infinite medium with the
                                                                                                                 material properties of the nth layer is
                                                       I 11@             (r aA
                                          Wn (r, z)     az    -   r ar        dr                                                        (r,-,)          e         1.    s J (rs) ds
                                                             a         a'A                                                                        10              a"(s)                          (5)
                                                             - +
                                                              ar        a raz                                    where zs is the source depth. Inclusion of multiple
                                                                                                                 sources requires only a sum of such sources.

                                                                                                          429

                  The potentials at any position in any layer are                   the parametric experiments where the amplifier
                  determined via Eqs. 3 and 5 if one knows the values of            problems were not present (Ref. 4).
                  the coefficients in Eq. 4 for all s values. These values are
                  determined in principle by the boundary conditions at             Another indication of agreement between experiment
                  each interface.     In practice, efficient and stable             and theory can be obtained by examination of the
                  numerical computation of these coefficients requires              dashed and solid straight lines in Fig. 2. Using the data
                  care.3 After determination of the potentials, the                 points input into the NCAR routine, the horizontal
                  particle displacements can be determined via Eq. 1.               position of the maximum pressure was established at
                  Furthermore, the values of the stresstensor (viscoelastic         four depths within the sediment. The dashed line in
                  solid) or pressure (attenuating liquid) can be                    the experimental plots is the best fit line to these
                  determined at any position from the potentials.                   points. The dashed line has been transferred over to
                                                                                    the theoretical results where it can be compared with
                  To obtain results for comparison with the experiments             the solid line which is its theoretical counterpart.
                  in Section 11, we placed an array of sources in a water
                  half space such that the incident grazing angle as well                               V. CONCLUSIONS
                  as the angular separation and relative strength
                  between the primary and secondary lobes of the                    The experiment discussed here is novel in its physical
                  incident beam conformed to the experimental                       range for these types of frequencies. This is due to the
                  arrangement. Preliminary investigation showed that                extent and homogeneity of the sand layer as well as the
                  the theoretical results for in-sediment pressure                  lack of confining walls in the water column. The data
                  contours were not significantly different if we used an           thus allow an unique test of theoretical predictions.
                  attenuating liquid model of the sediment instead of a             The results indicate the utility of the SAFARI code in
                  viscoelastic solid model with realistically low values of         examining transmission of bounded beams across
                  shear wave speed.4 Therefore, in the comparisons                  water/sediment interfaces. Furthermore, they indicate
                  between experiment and theory to be shown next, the               that inclusion of the shear degree of freedom is not
                  theoretical results use an attenuating liquid sediment            essential for prediction of the pressure contours within
                  model with wave speed and attenuation as given in                 unconsolidated sand sediments. As a note of caution,
                  Section 11.                                                       however, if the sediment cannot be treated as infinite
                                                                                    the inclusion of the shear degree of freedom can
                     IV. COMPARISON OF THEORY AND EXPERIMENT                        become important.4,7

                  The in-sediment longitudinal wave speed given              in                          VI. REFERENCES
                  Section 11 along with the measured in-water
                  longitudinal speed of 1510 m/sec implies a critical               1. W. M. Ewing, W. S. Jardetzky, and F. Press, Elastic
                  grazing angle of 25.80. With this in mind, the grazing            Waves in Layered Media (McGraw-Hill, New 7-ork,
                  angles chosen in the experiment were 51.9o, 28.8o,                1957), Chap. 4.
                  25.80, and 20.1o thus including both pre- and post-
                  critical angles. In a!l the plots shown, the origin has           2.  H. Schmidt and F. B. Jensen, "A Full Wave Solution
                  been placed where the center of the incident beam                 for Propagation in Multilayered Viscoelastic Media
                  strikes the water-sediment interface. All contours are            with Application to Gaussian Beam Reflection at Fluid-
                  in relative clBs.                                                 Solid Interfaces," J. Acoust. Soc. Am. 77, 813-825 (1985).

                  Theoretical results using SAFARI are shown on the left            3.  H. Schmidt and F. B. Jensen, "Efficient Numerical
                  hand side of Fig. 2 for incident grazing angles of 51.9o,         Solution Technique for Wave Propagation in
                  28.8o, 25.8o, and 20.10. Only the incident portion of             Horizontally Stratified Ocean Environments," Rep. SM-
                  the total field in the water is shown. The right hand             173, SACLANT ASW Research Centre, La Spezia, Italy
                  side of Fig. 2 shows the experimental results at the              (1984).
                  corresponding angles. Examination shows "excellent"
                  agreement in overall contour shape between                        4. K. L. Williams, L. J. Satkowiak, and D. R. Bugler,
                  experiment and theory except in some portions of the              "Linear and Parametric Bounded-Beam Transmission
                  20o data where the signal to noise ratio was low.                 Across a Water/Sediment interface - Theory,
                  Proper prediction of location and amplitude of the                Experiment, and Observation of Beam Displacement,"
                  secondary lobe within the sediment relative to primary            Submitted to J. Acoust. Soc. Am.
                  lobe is apparent.
                                                                                    S. D. R. Bugler, UTH Technical Memo, 66/87, A.R.E.
                  Fig. 2 also shows, as curved dotted lines, the levels of          Portland, U.K., 1987.
                  the pressure contours within the sediment relative to
                  the maximum pressure of the incident beam at the                  6.  More information on NCAR routines can be
                  interface. In this regard, agreement between theory               obtained by writing National Center for Atmospheric
                  and experiment is not quite so impressive. The levels             Research in Boulder, Colorado.
                  seen in the experiment are always lower than predicted
                  by SAFARI. However, it is very possible that this is due          7.  P. J. Vidmar, "Ray Path Analysis of Sediment Shear
                  to amplifier problems experienced while performing                Wave Effects on Bottom Reflection Loss," 1. Acoust. Soc.
                  the linear source experiments. This may have made the             Am. 68, 639-648 (1980).
                  peak levels in the incident beam lower than what had
                  been measured when the source characterization
                  experiments were performed. In support of this
                  contention, / we found much better agreement in

                                                                               430

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                                                                                           ...... -5 dB
                                    5 dB                                                          15 dB
                       1.5F       -i5 d
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                          0.0                                                    5     0.0                                                   5.5

                                    HORIZONTAL DISTANCE (M)                                          HORIZONTAL DISTANCE (M)

                  Fig. 2. Theoretical and experimental results for                     and their experimental counterparts are shown on the
                  transmission of a linear beam across a water/sand                    right hand side. The incident grazing angles are (a)
                  interface. Theoretical pressure contours generated by                51.90 (b) 28.80 (c) 25.8o (d) 20. 1 o.
                  SAFARI are shown on the left hand side of the figure

                                                                                  432

                                               REMOTE SEA BOTTOM CLASSIFICATION UTILIZING THE
                                               ULVERTECH BOTTOM PROFILER PARAMETRIC SOURCE

                                                                    L. J. Satkowiak

                                                            Naval Coastal Systems Center
                                                        Physical Acoustics Branch, Code 2120
                                                             Panama City, FIL 32407-5000

                                     ABSTRACT                                system consists of a control and receiver unit, a power
                                                                             amplifier, a power supply for the power amplifier, and
             Computer algorithms were developed to extract                   a transducer. The profiler uses a parametric transmitter
             certain marine sediment properties utilizing the                to enerate a low frequency acoustic beam which has a
             Ulvertech Bottom Profiler system. A series of normal            wi3e bandwidth and a narrow beamwidth, to give high
             incidence bottom reflectivity measurements was made             resolution sub-bottom information. The generation of
             over six test tracks. The test tracks were precise paths        the low frequency acoustic waves in a parametric
             that varied in length from 0.1 to 0.5 miles long over           transmitter is accomplished by exciting a transducer
             sediments that ranged in composition from hard sand             with two frequencies separated by the required
             to stiff clay to soft mud.       Each track was well-           difference (low) frequency. The non-linear nature of
             characterized by several core samples. The Ulvertech            the water will cause the two waves to interact
             system uses a parametric source that has its primaries          producing a sum and difference frequency. The
             at about 200 kHz with the difference frequency                  difference frequency is of main interest to
             selectable, either 5, 10, 15, or 20 kHz. The algorithms         investigations requiring sub-bottom penetration. In
             developed make use of the acoustic information                  the current study the Ulvertech profiler output two
             contained in the returns from both the primary and              primary frequencies, one at 200 kHz and the second at
             difference frequency to extract estimates of the                220 kHz thus generating difference frequency of 20
             density, grain size, and shear strength of the top 1-2          kHz.
             meters of sediment. Some sample data as well as a
             description of the algorithms will be presented.                The Ulvertech profiler was chosen for this research for
                                                                             the following reasons:

                                                                                  1. A narrow beamwidth at a low frequency can
                                                                             be obtained from a relatively small transducer. The
                                 1. INTRODUCTION                             narrow beamwidth allows only a small section of the
                                                                             bottom to be sampled on any given ping. The footprint
             A subject generating a ?ireat deal of interest is the           on the bottom of the 20 kHz signal is only about 60
             remote sensing of Sur cial sediment properties,                 centimeters in 10 meters of water. The small footprint
             surficial referring to the first 1 to 2 meters of sediment.     minimizesthe effect of multiple scattering paths.
             For example, identifying regions of a water requiring
             dredging requires a knowledge of the density and                     2. The beam has essentially no sidelobes. This
             possibly the grain size of the surficial sediments.             helps eliminate multiple scattering paths.
             Marine construction may require a determination of
             the bearing or shear strength of the sediment. Core                  3.  Both the high and low frequency signals are
             sampling can provide these data but it is time                  available on the receiver side. The high frequency
             consuming, area specific (the core may only represent a         primary signals are used to give a precise detection of
             localized sediment), and relatively expensive. The              the first mud/water echo and also to trigger the time
             current work was und.ertaken to acoustically identify           varying gain forsub-bottom low frequency signal.
             sediment properties using an expeditious, inexpensive,
             and accurate method. A series of normal incidence               The main disadvantage to a parametric source is the
             acoustic backscatter measurements was made in the               high powers required to obtain acceptable source
             Panama City, Florida, area. Core samples provided the           levels. However, modern high power FET's have made
             necessary ground truth used to extract the                      the design of high power amplifiers relatively cheap.
             relationships between echo return and sediment
             properties.                                                     'in order to measure the beamwidth and frequency
                                                                             distribution of the difference frequency, the transducer
                                  2. EXPERIMENT                              was calibrated in the Naval Coastal Systems Center
                                                                             Acoustic Test Facility. The maximum amplitude of the
             The Ulvertech Bottom Profiler                                   signal of the primary (200 kHz) signal was measured to
                                                                             be 229 dB (re 1pPa @ 1m) with a beamwidth of 2.50
             The bottom classifier developed uses the Ulvertech'             measured at the 3dB points. The 20 kHz difference
             Bottom Profiler (UBP) as an acoustic source. The UBP            signal was measured to have a source level of 192 clB

                                                                          433 United States Government work not protected by copyright

                   (re 1pPa @ im) with a bearnwidth of 3.00. The signal              instead of using peak voltage values, the signals were
                   levels were more than adequate to overcome any                    summed over time, thus reflecting the total acoustic
                   signal loss occurring due to spreading loss, absorption           energy returning to the transducer. Each channel or
                   in the water column,ambient noise, and/or bottom loss.            time slice was corrected for background (noise) by
                   The absence of sidelobes helps eliminate the effect of            subtracting off a background contribution.                The
                   multiple scattering paths. In order to investigate the            ma nitude of the background contribution was found
                   relationship between sediment shear strength and the              by flitting the "non-peak" area with a straight line. We
                   change in shape of the return pulse it is important to            found a very strong correlation between the h h
                                                                                     frequency signal and the density and grain size of i@
                   eliminate any spurious pulse stretching due to multiple                                                                     t e
                   scattering paths.                                                 surficial (first 5 to 20 centimeters) sediment. The
                                                                                     following relationships were determined:
                   The Test Sites
                                                                                          Grain size (phi units)
                   A series of five test tracks, precisely defined utilizing                   9.0785 - 7.5951 * LOG 10 (Summed signal)
                   readily identifiable shore reference markers as well as
                   their LORAN-C coordinates, were set up in the Panama                   Density(g/cm3)
                   City area bays and in the nearby Gulf of Mexico. The                        -0.04586 + 0.9258* LOG 10 (Summed signal)
                   length of these tracks varied from 0.1 to 0.5 miles long.
                   The sediment types varied from hard sand to stiff clay            The   low frequency signal (20 kHz) penetrates the
                   to soft mud. Each track was well characterized by                 sediment more deeply and allows sampling via changes
                   several core samples. The ana sis of these cores                  in the magnitude of the signal, of the density and grain
                   N
                    ielded information on the         sellment grain size            size of the sub-surface sediment as a function of depth.
                     nsity, water content, porosity, and soun velocity as'           By breaking the low frequency return into equal time
                   a function of depth in the sediment. The core sample              bins corresponding to vertical "layers" of the sea floor
                   analysis techniques used and the results of the analyses          one can obtain a density and grain size profile. The
                   can be found in Reference 1.                                      following relationships were extracted relating the
                                                                                     summed signal in the first of the equal time bins to the
                   Data Acq u isition                                                grain size and density:
                   The data were taken utilizing the UBP transducer as                    Grain size (phi units)
                   both a transmitter and receiver. The output from the                        2.392 - 5.166*LOG10 (Sum-sig-1)
                   UBP receive side was filtered, rectified, amplified, and
                   fed into a Nicolet 4094 Digital Oscilloscope with a                    Density (g/CM3)
                   Model 4562 dual channel digitizer. The 4562 was set to                      0.729 + 0.6641*LOGlo(Sum-sig-1)
                   digitize at a rate of 500 kHz to avoid any possible
                   aliasing problems. The Nicolet d       19 itizer was set to       where Sum-sig-1 is the summed signal in the first time
                   average over a fixed number of pings and then                     bin, corrected for background.
                   transmit the data to an HP-9020 computer for storage.             There is at least one complication; one needs to correct
                   The effect of any platform instability was reduced by             the return signal magnitude for the effects of
                   using the bottom return to trigger the digitizer. The             attenuation in the sediment. A series of empirical
                   cligitization of the signal would begin approximately             relationships relating the grain size of the sediment to
                   2-4 milliseconds prior to receiving the return signal.            the attenuation has been derived by Hamilton
                   The cligitization of the signal would continue for 6-8            (reference 5). Since the high frequency signal is
                   milliseconds after the cessation of the return pulse.             essentially sampling just the upper few. centimeters of
                                                                                     the sediment, the density and grain size values
                   The acoustic data were taken on two separate dates                determined from this data can be used to correct the
                   about one month apart. The first set of data was                  magnitude of the signal in the first time bin of the low
                   analyzed and algorithms relating the properties of the            frequency pulse. The density/grain size determined
                   return echo with the core sample (ground-truth)                   from that low frequency time bin can be used to
                   sediment properties were derived. The second set of               calculate the estimated attenuation for correcting the
                   measurements was made to confirm the algorithms                   next time (sediment layer) bin. The procedure is
                   developed. A description of the algorithms and a                  repeated iteratively until the magnitude of the signal
                   discussion of the results follow.                                 drops below an arbitrarily set percentage of the
                                                                                     maximum amplitude. In this manner the grain size and
                   Density and Grain Size Determination                              density of the sediment can predicted from the acoustic
                                                                                     return as a function of depth in the sediment.
                   The density and rain size of sediments can be related
                   to the magnitUe of the normal incidence acoustic                  Shear Strength Determination
                   echo. This type of relationship has been demonstrated
                   by several authors (references 2-4). In the data                  It was found that the shear strength of the sediment
                   acquired using the UBP, there is acoustic echo                    and the magnitude of the signal, or even the summed
                   information in both the high (primaries) and low                  signal discussed above, do not correlate well. However,
                   (difference) frequency channels. The acoustic data                the  shear strength does correlate well with the shape,
                   recorded consisted of both the high and low frequency             in particular with the decaying edge or tail of the low
                   signals that were digitized and averaged on separate              frequency return signal. The decaying part of the
                   channels of the Nicolet but with a common trigger.                signal, or tail, can be quantified in several ways. In the
                                                                                     current investigation two methods were employed
                                                                                     with nearly equal success. One can fit the averaged

                                                                                434

               return signal (envelope) with a Gaussian shape with a              Table 1. A comparison of sediment properties
               decaying exponential tail and correlate the change in              determined from core sample analysis versus estimated
               the decay time constant with the shear strength.                   from acoustic return.
               Alternately, one can determine the width ofthe return
               pulse at the points where the pulse exceeds some
               fraction (arbitrarily chosen to be 1/e) of the maximum                                   FROM                     FROM
               and correlate the ratio of the return to outgoing pulse                             CORE SAMPLE            ACOUSTIC RETURN
               width with the shear strength. Both methods yielded                      SITE
               good correlations with about the same standard error                             Grain Size Density Grain Size Density
               of estimate, however the latter method requires less
               computational time and is easier to implement than                               (phi units) (g/CM3) (phi units) (g/CM3)
               the former. The second method yields the following
               relationship:                                                             G4        2.44         2.00        2.15         2.01
                   Shear Strength (g/Cm3)                                               S6-11  1   8.50         1.37        8.21         1.28
                        698.9*exp [-0. 17104* (Width -ratio) I                          S6-2       8.67         1.18        9.00         1.19
               where the Width-ratio is the time width ratio of the                    WP_1        9.01         1.23        8.30         1.27
               return pulse to that of the outgoing pulse. Note that                   WP-2        8.97         1.25        8.46         1.25
               since the total width of the signal is used, the -shear
               strength determined in this manner is "averaged" over                   WP-3        9.02         1.19        8.33         1.27
               the depth of penetration of the acoustic signal.
                                                                                        B14        2.42         2-00        2.23         2.01
                            3. RESULTS AND CONCLUSIONS                                 BB-1        6.22         1.50        6.76         1.43
               Two of the test tracks, denoted BU and G4, had                                      6.70         1.24        5.20         1.66
               sediments composed 'of- medium sand with grain
               diameters on the order of 180 to 250 microns. Site WP
               sediment consisted of a very soft silty-clay with a small
               percentage of sand at the start of the test track. Site BB         Since the 56 site has such a dynamic range in sediment,
               and HB contained sediments that ranged from a clayey-              it was chosen for displaying the predictive capability of
               sand to a sandy-clay with average densities ranging                the algorithms. Figures la, 1b, and ic show the
               from 1.3 to 1.7 g/cc and grain sizes ranging from 15 to            predicted density, grain size, and shear strength as a
               150 microns. However, due to the close proximity of                function of distance along the track. The letters
               the Hathaway Bridge, the Port of Panama City, and the              plotted indicate the data from three separate passes
               shipping channel it was difficult to maintain station for          along the track. Note the reproducibility of the data
               track HB and the data were non-reproducible from one               from set to set. Also shown are the results of the core
               test run to the next and was not used in the analysis.             sample analysis for comparison. The data agree well at
               Track S6 proved to be the most interesting site. The               the two core sample locations and qualitatively agrees
               track extended from near a marina out to a shipping                with the historical nature of the track, harder
               channel. The sediment near the marina was dominate                 sediments at the two ends and relatively soft in the
               by a sand fill placed prior to construction of the clocks.         middle.
               Moving away from the marina the sediment became a
               soft silty-clay (mud) until one approaches the dredged             In summary, a series of normal incidence acoustic
               channel where the sediment becomes a stiffer clayey-               measurements were made using the Ulvertech
               sand or a sandy-clay.                                              Parametric Bottom Profiler as a source. Algorithms
                                                                                  were derived, utilizing the dual frequency nature of
               Table I contains a comparison, as function of test        site,    the source, relating properties of the acoustic return
               of the p reclicted (based on acoustic return) grain       size     with sediment characteristics determined from core
               and density versus the values extracted from the          core     samples. Tests indicate that the UBP source and the
               samples. These predicted values were determined from               algorithms derived provide a relatively fast and
               the first time bin of the low frequency return and                 accurate method to remotely characterize marine
               represent the first 20 to 30 centimeters of sediment. In           sediment.
               general, the predicted values for the sediment density
               and grain size agree quite well with the values
               determined from the core sample analysis., Entrapped
               gas, noted in the core sample analysis, on the BB track
               caused some fluctuations in the data on that track. The
               presence of entrapped gas causes a stronger return
               from the sediment thus yielding a higher. value for the
               density and grain size. However, the changing shape of
               the low frequency signal combined with a relatively
               unchanging high frequency signal provides an
               indication of this phenomenon occurring.

                                                                             435

                                          4. REFERENCES                                                   Site S6 Bottorn Classifier Test
                  1. C. Ingram et. al., Marine Geological Laboratory                             2.0            1    1      1               1     1    1
                  Report #640, Naval Oceanographic Office, August                                1.9  -<-Channel                            Marina --- >
                  1986.                                                                       -  1.8  -
                  2. K. Winn, G. Becker, and F. Theilen, "The                                 M
                  Relationship Between Sediment Parameters and the                               1.7  -
                                                                                                                 FIGURE 1A
                  Acoustic Reflectivity of the Sea-Bed," from Acoustic
                                                                                              mo 1.6  -
                  and the Sea-Bed edited by N. G. Pace, University Press,
                  Bath UK, 1983.                                                              >1 1.5  -
                  3. R. Faas, "Analysis of the Relationship Between                              1.4  -
                  Acoustic Reflectivity and Sediment Porosity,"
                  Geophysics, Vol. 34, No. 4,1969.                                               1.3-

                  4. A. Kaya, A. Tsuchiya, and M. Nishimura, "Acoustic                           1.2-
                  Precise Measurement of Physical Properties of Floating                                                    J
                  Soft-Mud Sediment " from Acoustics and the Sea-Bed                             1.1  -                            X-Core Sample Data
                                                                                                                                   I.J.K-ciassirier Test Data
                  edited by N. G.. Pa@e, Bath University Pres          s, Bath UK,               1.0.
                  1983.                                                                          11
                  5. E. L. Hamilton, "Geoacoustic Modeling of the Sea                            10 -<-Channel                              Marina-->
                  Floor," J. Acoust. Soc. Am., 68 (5), Nov. 1980.
                                                                                                  9-
                                                                                                                   x
                                                                                                  8   -

                                                                                                  7-

                                                                                                  6-

                                                                                                  5-

                                                                                                  4   -              FIGURE 1B

                                                                                                  3-

                                                                                                  2-                               X-Core Sample Data
                                                                                                                                   1,J,K-Ciassifier Test Data

                                                                                                 300

                                                                                              N  270 -<-Channel                             Marina-*

                                                                                                 240-

                                                                                                 210-

                                                                                                                   FIGURE IC
                                                                                              MO 180-
                                                                                              0
                                                                                                 150-

                                                                                                 120-

                                                                                                 90-
                                                                                              M
                                                                                                 60-

                                                                                                 30-                 1             X-Core Sample Date
                                                                                                                                   1,J,K-Classifier Test Data
                                                                                                  0                                   1     1     f    I
                                                                                                          1    2     3      4   5    6      7     8    9 10
                                                                                                               Position      (Arbitrary Units)

                                                                                                      Figures IA, 1B, JC show the predicted density, grain
                                                                                                      size, and shear strength, respectively, as a function
                                                                                                      of position along test track S6. The letters, I, J,
                                                                                                      and K, indicate the results from three separate data
                                                                                                                   FIGURE IC
                                                                                                                   GURE IA V
                                                                                                                                              j

                                                                                                                                   X_C.,e Sample

                                                                                                                                        j

                                                                                                                            j       -C3.r. Sample
                                                                                                                                   X
                                                                                                                                   I.J,K-Cl .. Ifier

                                                                                                      acquisition passes along the track. The letter X
                                                                                                      indicates the values of the sediment Droperties
                                                                                                      determined from core samples (ground-truth).

                                                                                     436

                              PARTICLE REWORKING IN GREAT LAKES SEDIMENTS: IN-S17U TRACER STUDIES
                                                    USING RARE EARTH ELEMENTS

                                                       John R. Krezoski

                                                 Center for Great Lakes Studies
                                               University of Wisconsin-Milvaukee
                                                       Milwaukee, WI 53201

                                                                      (2,3,12). Mechanisms and rates of reworking have
                                  ABSTRACT                            further been determined from laboratory microcosm
                                                                      studies using natural sediments spiked with
               Pollen grain distributions and radioactive             conservative elements or radioactive tracers (see
               fallout horizons observed in sediment cores            reviews in 8,9,13). These techniques have provided
               collected over the past decade have served as          significant insight into sediment reworking
               tracers of sediment reworking and burial rates         processes but they suffer from the following
               for both the marine and lacustrine                     inherent drawbacks: (1) Data from palynological
               environments. Errors associated with the               and radionuclide studies, which are
               analysis of these cores, attributable to               geochronological in nature, are time-avexaged over
               blogenic sediment reworking and shipboard              tens of years or more, making it difficult to
               handling, have necessitated the development of         interpret recent (S 30 yr.) events; (2)
               more precise techniques to measure sediment            Radionuclide and pollen horizons are subject to
               transport rates. We utilize a rare earth               sediment focusing where net loss or gain of tracer
               element tracer technique, which takes                  can be a function of grain size, resuspension
               advantage of the high neutron-capture cross-           events, and lateral transport phenomena; and (3)
               section of samarium oxide, and neutron                 Laboratory microcosm studies are conducted under
               activation analysis, to trace the burial and           highly idealized conditions and are likely to be
               lateral transport rates of surficial sediments         unrepresentative of in situ conditions. For
               in the littoral (SCUBA diver depths) and               example, the sediment reworking rates measured in
               profundal (manned submersible depths) of the           microcosms without sedimentation (e.g. 8) are
               Great Lakes. The results of these                      likely to be quite different from natural reworking
               measurements aid in determining the mass               rates. Thus, accurate descriptions of in situ
               balance of contaminants in the lakes.                  sediment reworking and transport processes in the
                                                                      Great Lakes and coastal marine environment are
                              1. INTRODUCTION                         still largely unavailable even though such
                                                                      information is very important in determining the
            Sediment reworking and transport processes in the         mass balances and final resting places of
            profundal Great Lakes and coastal marine                  contaminants and other anthropogenic components
            environments are important features that influence        that have been added to marine systems.
            post-depositional distributions of pollen grains,
            diatom frustules, and atmospherically-derIved             An alternative but virtually unused approach for
            radionuclides which are used to interpret the             determining profundal or pelagic sediment reworking
            sedimentary record and determine recent                   and transport rates Is through In situ tracer
            sedimentation rates, regional historical events,          experiments, using environmentally safe but easily
            and fates of organic contaminants in the respective       detectable tracers, of grain size and density
            environments (1-4). Considerable attention has            identical to the fine-grained sediments being
            been-focused on understanding modes and rates of          studied. Marine and freshwater investigators have
            post-depositional sediment reworking in the Great         employed this technique by placing colored
            Lakes and marine environments with the result that        particles, microspheres or other materials at the
            most theoretical models describing particle               sediment-water interface and monitoring their
            dynamics or reconstructing the history of pollutant       movement over time. By microscopically examining
            input to the marine systems, based on sediment            particle distributions in infaunal fecal material
            profiles, include surficial sediment reworking            and in sediment cores taken from the study areas,
            terms (1,2,5-11).                                         much has been learned about benthic organism
                                                                      feeding and life habits and sediment redistribution
            Present knowledge  of sediment redistribution and         processes (13-17).
           .reworking In the Great Lakes and other aquatic and
            marine systems stems largely from comparative             A serious drawback to this technique has been the
            studies of pollen-grain or radionuclide                   Inability to accurately follow a tracer once It is
            distributions preserved in the sedimentary record         diluted by the surrounding sediment (see 13).

                                                 CH2585-8/88/0000- 437 $1 @1988 IEEE

                  After several days, the labeled particles become               8046.581W), at 125m depth (24).       This location was
                  harder to find and estimates of their densities                selected because the sediments were known to be
                  become increasingly difficult and time consuming.              fine-grained, the area was representative of other
                  Thus, long-term studies using this technique have              profundal regions of the Great Lakes where blogenic
                  not been possible and errors in estimates of tracer            reworking had been reported, and it was one of the
                  particle densities in reworked sediments have been             few regions in Lake Superior known to support
                  high.                                                          standing stocks of benthos which approximate those
                                                                                 found in profundal regions of the lower Great Lakes
                  In order to overcome the problem of tracking the               (25).
                  tracer particles, to increase the precision of the
                  in situ tracer technique, and to automate sample               The objectives of the experiment were to: (1)
                  analysis, Krezoski (18) developed a radiometric                carefully place a thin layer of REE tracer at the
                  technique using selected lanthanide series (rare               sediment-vater Interface in an area of undisturbed
                  earth) elements as sediment tracers.      Rare earth           fine-grained profundal sediments; (2) leave the
                  elements (REE's), which axe found naturally in                 study area and allow the marked sediments to react
                  soils and sediments in trace quantities, are non-              to ambient conditions for a pre-determined length
                  hazardous, readily detectable analogs of fine-                 of time; (3) return to the site later to collect
                  grained sediments.    Moreover, because of their high          undisturbed sediment samples, and (4) analyze
                  neutron-captuxe cross-sections, they can be                    tracer distributions in sediment cores taken from
                  detected at nanogram quantities when examined by               within and around ("I m radius) the marked area to
                  instrumental neutron activation analysis (INAA: see            determine rates of lateral and vertical transport
                  19).                                                           of the tracer compound.

                  Another difficulty that currently impedes use of in            The REE tracer was prepared as a pellet
                  situ tracer techniques in deep water is the need to            encapsulated in a cylindrical cake of ice (see 26).
                  relocate and return to a precise sediment study                This method permitted the tracer to be carried to
                  site. Most in situ tracer experiments have been                the lake bottom without any loss and allowed the
                  conducted with the aid of divers and thus have been            tracer particles to be gently deposited at the
                  limited to relatively shallow, diver-accessible                sediment-water interface as the ice melted (Fig.
                  depths (@30 m). Use of this tracer technique by                1).
                  divers in the high-energy littoral waters of
                  Sturgeon Bay, Lake Michigan (see 18) was severely
                  compromised by resuspension of the sediments by
                  wind-generated waves (20,21). Additionally, the
                  sediments at these locations are primarily coarse-
                  grained deposits. Thus, very little information is
                  available on In situ infaunal and physical
                  reworking of fine-grained deposits at profundal
                  depths OtI00 m). Application of deep submergence
                  research vehicle (DSRV) technology, however, makes                                                 15 cm
                  in situ tracer studies at profundal depths readily
                  possible. DSRV's are quite useful and are becoming
                  increasingly available for limnological and marine
                  research and have been shown to be effective tools
                  for work in pelagic environments (22). Highly
                  sophisticated manipulator arms and underwater video                                20 Cm
                  and photographic systems permit sample collection
                  and underwater observation which was never                     Figure 1. Schematic diagram of rare earth element
                  available before (23). Additionally, underwater                  tracer pellet.
                  acoustical beacons can permit return to exactly the
                  same site on the order of years later. This paper              To begin the experiment, the frozen pellet was
                  presents the results of an in situ REE tracer study            carried to the lake bottom by the DSRV Johnson-Sea-
                  conducted in a profundal region of Lake Superior               Link II and was placed on the lake floor. An
                  using a DSRV to determine actual sediment burial               underwater beacon (37 kHz acoustical pinger; Helle,
                  and transport rates In a fine-grained depositional             Inc.) was deployed 0.5 m from the pellet. While
                  basin and evaluates the utility of tracer                      the pellet was still frozen (00 minutes after
                  experiments at profundal depths using REE and DSRV             deployment), control sediment samples were
                  methodologies.                                                 collected -3 m away from the study site (7.6 cm
                                                                                 diameter, DSRV Alvin style punch cores) and a
                                      2. METHODOLOGY                             precise fix on the study site was obtained with the
                                                                                 aid of acoustical positioning (Honeywell Hydrostar)
                  The sediment tracer study was conducted in the Ile             and loran C navigation (North Star 7000) systems
                  Parisienne depositional basin, a major north-south             aboard the surface support vessel, the R/V Seward
                  trough, in southeastern Lake Superior, 40 km                   Johnson.
                  northeast of Sault Ste. Marie, Michigan (46     0 43,131H

                                                                             438

             After 23 days, the DSRV was re-deployed at the Ile
             Parisienne station where it descended to the bottom
             near the acoustical beacon. Using an on-board
             sonar system to home in on the pinqer, the DSRV
             maneuvered to the tracer pellet location and                                                7+0.4
             collected eleven undisturbed punch cores.        On                                5.8+0.3
             shipboard the cores were sectioned in I cm                                16.5+0.8
             intervals and frozen for analysis ashore.                                                   1.9+0.1
                                                                                                             3.9+0.2
             In the laboratory, the core sections were       dried,                                         20+0.1
             weighed (�0.1 mg), and evaluated by instrumental
             neutron activation analysis (INAA) at the                                                     CENTER
             University of Wisconsin-Madison Reactor Lab and the                          10.7+0.5        60.1+3.0
             University of Wisconsin-Milwaukee Center for Great                                           30.5+1.5
             is5es Studies as described by Krezoski (26).       The
                Sm gamma ray activity (tl/2=46.8 h; u=5820tlOO
             Barns) was measured using a Canberra Series 80
             multichannel analyzer and a GeLi detector (see 19).
             Calibration standards indicated that the gamma
             spectrometer had a counting efficiency of 0.3%.                Figure 2. Schematic representation of samarium
                                                                              distribution pattern at REE study site after 23
                           3. RESULTS AND DISCUSSION                          days. Center of figure represents location of
                                                                              tracer pellet. Vectors indicate compass     1
             Deployment of the REE tracer pellet and pinger at                direction and concentration of Sm (Ag*g ) in
             the beginning of the experiment was successful and               cores collected I m from the center.
             from the control cores collected at the site, the
             natural background concentration of Sm in the                  Advective transport of the tracer material which
             sediments was found to be 5.5 gg    .g  . This result          was deposited responded to bottom currents which
             falls within the range predicted by Helmke (19) and            were not detectable by the DSRV1s current meter
             indicates that the 4.3 g of Sm (5 g SM203) added to            (located -2 m above the sediment-vater interface;
             the study site via the tracer pellet increased the             calibrated �0.1 kt) or the observer's eye.
             final concegtratioi of the experimental sediments
             to 1.7 x 10 pg'   94 -   Thus, the tracer sediments            Advective transport of the tracer particles can be
             contained -3 x 10 greater Sm than the surrounding              shown, assuming the flux is one-dimensional, by:
             sediments and, as planned, the tracer sediments
             could be distinguished from surrounding sediments                                dC/dt = 2(dC/dz)
             by the observation of Sm concentratirs which
             exceeded the background of 5.5 pg*g                            where a-is the velocity of particle movement
                                                                            (cm'sec ), C is the concentration of excess tracer
             At the end of the 23 day experiment the Johnson-               (samarium) In the sediment, t is the elapsed time
             Sea-Link If landed within 90 m of.the_jinger and               of the experiment (23 days) and z is the distance
             began moving toward it at -0.1 km hr. . At -5 m                from the tracer pellet to the punch core sample
             distance the pinger and marker line became clearly             location (-1 m). The velocity, 2, is thus
             visible and at -2 m distance the DSRV halted and               proportional to dC/dt and dC/dz. From linear
             the eleven core samples were taken. Two cores were             least-squares analysis_  T! tie data, it was found
             collected within -3 cm of the polypropylene line               that 4C/dt=-0.085 gg*g     s   and dC/dz=-49.9
             marker (to sample the remains of the tracer pellet)            gg*g-L'm-1 (see 26). Thus, the average particle
             and the remaining nine cores were collected around             velocity of the REE particles was found to be 0.17
             the perimeter of a "2 m diameter circle                        cm*s
             circumscribing the tracer pellet (Fig. 2). A
             twelfth core sample 5) was lost when it's check                It is apparent that the ice pellet technique needs
             valve malfunctioned.                                           to be more fully developed or an alternative
                                                                            methodology must be employed (e.g. 27) and that a
             A Sm Inventory was calculated to determine the      mass       sensitive current meter must be deployed close to
             of initial tracer pellet disbursed over the study              the experiment so that advective transport
             area (see 26).    Compared with the original mass of           processes can be distinguished from eddy-diffusive
             Sm in the tracer pellet (4.3 g), it was apparent               processes and anomalies in mass balance
             that at the end of the 23 day experiment slightly              determination can be correlated with physical
             less than 1% of the Sm originally placed at the                events.
             study site was accounted for. Subsequent work with                              4. ACKNOWLEDGMENTS
             an ROV has shown that uneven ice pellet melt may
             have occurred such that the pellet, when mostly                I wish to thank D.N. Edgington, J.V. Klump, G.E.
             dissolved, becomes detached from the small                     Glass, L.F. Boyer, R.A. Cooper, W. Cooper, T.M.
             counterweight and floats up the I m marker line.               Askew, and R.M. Oven for their helpful suggestions.
                                                                            P.A. Helmke and R.J. Cashvell provided me with
                                                                                    *@� 0 4
                                                                                                         19+ 0.1
                                                                                                             3 9 � 0 @2

                                                                        439

                 critical information on instrumental neutron                    10.  Robbins, J.A. 1986. A model for particle-
                 activation analysis techniques. This research was                    selective transport of tracers in sediments
                 supported by grants from the U.S. Environmental                      with conveyor belt deposit feeders. J.
                 Protection Agency (CR813538-01-0), the University                    Geophys. Res.- 91(C7):8542-8558.
                 of Wisconsin Sea Grant Program (R/MW-38-PD), the
                 NOAA National Undersea Research Program and the                 11.  Christensen, E.R., and Bhunia, P.K. 1986.
                 Center for Great Lakes Studies, University of                        Modeling radiotracers in sediments:
                 Wisconsin-Milvaukee.                                                 Comparison with observations in Lakes Huron
                                                                                      and Michigan. J. Geophys. Res, 91(C7):8559-
                                      5. REFERENCES                                   8571.

                  1.   Guinasso, N.L., and Schink,    D.R., 1975.                12.  Davis, R.B. 1974. Stratigraphic effects of
                       Quantitative estimates of biological mixing                    tubificids in profundal lake sediments.
                       rates in abyssal sediments. J. GeoRhys. Res.                   Limnol. Oceano9r. 19:466-488.
                       80:3032.
                                                                                 13.  Fisher, J.B., Lick, W.J., McCall, P.L., and
                  2.   Robbins, J.A., and Edgington, D.N. 1975.                       Robbins, J.A. 1980. Vertical mixing of lake
                       Determination of recent sedimentation rates in                 sediments by tubificid oligochaetes.
                       Lake Michigan using Pb-210 and Cs-137.                         Geophys, Res. 85:3997-4006.
                       Geochim, Cosmochim. Acta. 39:285-304.
                                                                                 14.  Aller, R.C., and Dodge, R.E. 1974. Animal-
                  3.   Robbins, J.A., Edgington, D.N., and Kemp,                      sediment relations in a tropical lagoon
                       A.L.W. 1978. Comparative lead-210, cesium-137                  Discovery Bay, Jamaica. J. Mar. Res. 32:209-
                       and pollen geochronologies of recent sediments                 232.
                       of lakes Erie and Ontario. Quat. Res. 10:256-
                       278.                                                      15.  Winston, J.E., and Anderson, F.E. 1971.
                                                                                      Bioturbation of sediments in a northern
                  4.   Swackhamer, D.L., and Armstrong, D.E. 1986.                    temperate estuary. Mar. Geol. 10:39-49.
                       Estimation of the atmospheric and
                       nonatmospheric contributions and losses of                16.  Self, R.F., and Jumars, P.A. 1978. New
                       polychlorinated biphenyls for Lake Michigan        on          resource axes for deposit feeders. J. Mar.
                       the basis of sediment records of remote lakes.                 Res. 36:627-641.
                       Environ. Scl, Technol. 20:879-883.
                                                                                 17.  Jumars, P.A., Self, R.F.L., and Nowell, A.R.M.
                  5.   Schink, D.R., and Guinasso, N.L., Jr., 1978.                   1982. Mechanics of particle selection by
                       Redistribution of dissolved and adsorbed                       tentaculate deposit feeders. J. Exp. Mar.
                       materials in abyssal marine sediments                          Ecol. 64:47-70.
                       undergoing biological stirring. Am. Jour. Sci.
                       278:687-702.                                              18.  Krezoski, J.R. 1985. Particle reworking In
                                                                                      Lake Michigan sediments: In situ tracer
                  6.   Robbins, J.A., McCall, P.L., Fisher, J.B., and                 measurements using a rare-earth-element.
                       Krezoski, J.R., 1979. Effects of deposit                       Abstr. 28th Conference on Great Lakes
                       feeders on migration of 137-Cs in lake                         Research, Milwaukee, WI.
                       sediments. Earth Planet. Sci. Lett. 42:277-
                       287.                                                      19.  Helmke, P.A. 1982. Neutron Activation
                                                                                      Analysis. In Methods of Soil analysis, Part
                  7.   Christensen, E.R. 1982. A model for                            2. Chemical and Microbiological Properties.
                       radionuclides in sediments influenced by                       (2nd edition)-, eds. A.L. Page, R.H. Miller,
                       mixing and compaction. J. Geophys. Res,                        and D.R. Keeny. Am. Soc. Agron.-Soil Sci. Soc.
                       87(Cl):566-572.                                                Am., Agronomy Monograph no. 9.

                  8.   Krezoski, J.R., Robbins, J.A., and White, D.S.            20.  Thomas, R.L., Kemp, A.L.W., and Lewis, C.F.M.
                       1984.  Dual radiotracer measurement of                         1973. The surficial sediments of Lake Huron.
                       zoobenthos-mediated solute and particle                        Can. J. Earth Sci. 10:226-271.
                       transport in freshwater sediments. J. GeophZl,
                       Res. 89(B9):7937-7947.                                    21.  Sly, P.G., and Thomas, R.L. 1974. Review of
                                                                                      geological research as it relates to an
                  9.   Krezoski, J.R., and Robbins, J.A. 1985.                        understanding of Great Lakes limnology. J.
                       Vertical distribution of35eeding and particle-                 Fish. Res, Board Can, 31:795-825.
                       selective transport of       Cs in lake sediments
                       by lumbriculid oligochaetes. J. Geophys. Res,             22.  Rechnitzey, A.B. 1986. On the upward trend in
                       90(C6):11999-12006.                                            manned submersible use. Sea Technol. 27:10-13.

                                                                            440

             23.  Cook, R.W. 1986. Underwater Imaging: One
                  user's perspective. Sea Technol, 27:29.

             24.  Thomas, R.L., and Dell, C.I. 1978. Sediments
                  of Lake Superior. J. Great Lakes Res. 4:264-
                  275.

             25.  Dermott, R. 1978. Benthic diversity and
                  substrate-fauna associations In Lake
                  Superior. J. Great Lakes Res. 4:505-512.

             26.  Krezoski, J.R., 1989. Sediment reworking and
                  transport in eastern Lake Superior: In-situ
                  rare earth element tracer studies. J. Great
                  Lakes Res. (in press).

             27.  Tudhope, A.W., and Scoffin, T.P. 1987. A
                  device to deposit tracer sediment evenly on
                  the deep sea bed. J. Sed. Petrol. 57:761-762.

                                                                 441

                                  IN-SITU TRACER STUDIES OF SURFICIAL SEDIMENT TRANSPORT IN THE GREAT LAKES
                                                           USING A MANNED SUBMERSIBLE

                                                                John R. Krezoski

                                                         Center for Great Lakes Studies
                                                       University of Wisconsin-Milvaukee
                                                              Milwaukee, WI 53201

                                       ABSTRACT                             deployment. The results demonstrated that not
                                                                            only were the depths far from q917t (calculated
                  Rare earth element (REE) tracer "pellets" were            bottom currents were -17 cm*sec    , but also that
                  fabricated by mixing -5 g samarium oxide and/or -2        deep submergence research vessel techniques are
                  g europium oxide with 250 ml natural (wet), fine-         continuing to open the doors to exciting and
                  grained sediment, freezing the mixture (in -1 cm          detailed studies of geochemical processes and
                  x -10 cm diameter cakes) and encapsulating them In        animal-sediment interactions at the sea floor In
                  weighted, 15 ca x 20 cm diameter cylinder of Ice.         fine-grained depositional areas. The implications
                                                                            of this work are that well established theories
                  In initial studies (1985) using samarium as a             regarding seafloor properties and processes,
                  tracer, a pellet was deployed on the floor of   the       especially In the Great Lakes, are being
                  Ile Parlsienne basin (125 m depth) of eastern   Lake      challenged and that commonly held beliefs
                  Superior using the Johnson-Sea-Link II (JSL 11).          regarding the ultimate fates of those toxic and
                  As the ice melted, most of the samarium, a stable,        hazardous materials which bind to fine-grained
                  high neutron capture cross section REE, added at a        sediments will have to be more closely
                  concentration approximately lOE4 greater than             scrutinized.
                  found naturally In Great Lakes sediments, settled
                  to the lake bottom and permitted tracking of in-
                  situ sediment transport in response to biogenic
                  and physical disturbances at the profundal depths.
                  The labeled area was marked by a -1 m strand of
                  weighted polypropylene line, and a 37 kHz
                  acoustical beacon was placed approximately 1 m to
                  the east of this point.

                  Tventy-three days after tracer deployment the
                  study site was reoccupied by the JSL II and 11
                  punch cores (7.6 cm diameter), collected from
                  within and around the labeled area, were sectioned
                  in I cm intervals to 10 cm and were analyzed by
                  neutron activation analysis. High resolution
                  gamma spectroscopy of the labeled sediments
                  revealed that little reworking had occurred during
                  the 3.3 vk period but suggested that longer term
                  studies were necessary and could be successful in
                  the quiet depths.

                  Subsequent studies (1986-1988), in the same region
                  of the Great Lakes, indicated that, indeed, the
                  labeled area could be relocated and sampled on the
                  order of two years later. In these studies, dual
                  tracers (Sm and Eu) were used (three.replicate
                  pellets) and a pinger with a three-year battery
                  pack was deployed. Moreover, careful loran-C and
                  Satnav coordinate measurements aided greatly in
                  relocating the study area.

                  Tventy-four punch cores were collected and
                  detailed photographic and video Images were taken
                  in July, 1988, 2 years and 10 days following

                                                      CH2585-8/88/0000-442 $1 @1988 IEEE

                                      VIDEO-SEDIMENT-PROFILE CAMERA IMAGERY
                                 IN MARINE AND FRESHWATER BENTHIC ENVIRONMENTS

                                                  Larry F. Boyer

                           Dept. of Geosciences, and Center for Great Lakes Studies
                                       University of Wisconsin-Milwaukee
                                    P.O. Box 413, Milwaukee, Wisconsin 53201

           In-situ video-sediment-profile camera           provides views of the sediment-water
           (VSPC) images will be displayed, "captured"     interface (SWI) that no other tool can
           using a combination of manned submersible       provide, coupled with the precise choice
           sampling techniques, and innovative charge-     of sampling provided through manned
           coupled-display technology. These live          submersibles. The VSPC has already been
           images provide an intimate perspective of       significant in designing sampling strategy
           benthic sedimentary structures, processes,      in the investigation of biogenic
           and dynamics from two very different            disturbances (biogenic sedimentary
           benthic regimes. Imagery from 350m in the       structures, ie. burrows, etc.) and their
           Caribou Island Basin of Lake Superior (1986     effects on infaunal community structure in
           dives) will be compared to that from 750m       the Great Lakes (380m) and on the southern
           depths on the upper continental slope off       New England upper continental slope (4,5).
           southern New England. Details of the            These images complement and enhance our
           mesotopographic relief (mms-cms) at the         traditional sampling methods. Future high
           sediment-water interface (SWI), epi- and        resolution direct image capture and
           infaunal organisms, their densities and         manipulation will allow quantitative
           spatial distributions may be addressed          analysis of these images.
           through this technique. Megabenthic burrow
           structures were easily identified from the
           sub, and the physical and biogenic                            PURPOSE AND GOALS
           sedimentary microstratigraphy were then
           examined in detail with the VSPC system              The purpose of this presentation is to
           down to 15-20cm within the sediments.           exhibit live video VSPC imagery from two
                                                           profundal environments. As such, this paper
                                                           represents an extended abstract, as the
                                                           real focus impact is in the viewing of the
                           INTRODUCTION                    images. The utility of these VSPC
                                                           techniques for studying larger megafaunal
                There exists a need for  detailed          and infaunal.biogenic sedimentary
           qualitative and quantitative   information,     structures in deep marine and freshwater
           derived from all possible complimentary         environments is demonstrated.
           techniques, on the nature of the physical,
           biological, and chemical properties of the
           sedinent-water interface, and the processes                      STUDY SITES
           that occur at or in close proximity to this
           critical benthic interface (1). This                 These studies were conducted in two
           boundary between fluid and sediment is a        locations. The first location, sampled in
           crucial one, as it is an active region of       1985,186, and 188, is the Caribou Island
           transport, resuspension, and deposition of      Basin in Lake Superior, approximately 8.5
           materials that are processed, mixed, and        nautical miles WSW of Southwest Bank (Lat
           altered physically and chemically by a          47 12.031N, Long 86 04.801W, Figure 1) in
           diverse suite of benthic organisms (2). The     350m depth (6,3). In this area, sediments
           video-sediment-profile camera is yet            above Precambrian bedrock consist of tills
           another tool enhancing our perspective of       and glacial gravels, glacial clays, and
           this interface (3).                             post-glacial clays draped with a thin
                                                           veneer of recent fine-grained lacustrine
                Video-sediment-profile camera (VSPC)       sediments and organics (7). This area
           imagery provides the only real-time in-situ     contains numerous biogenic sedimentary
           view of qualitative and quantitative            structures created by deep-water sculpin
           structures and processes indeep marine and      (Myoxocephalus thorpsoni, Figure 2) and the
           freshwater environments in concert with         burbot (Lota lota, Figure 3) (8). The
           manned submersibles. This technique             second site is an upper continental slope

                                          CH2585-8/88/0000- 443 $1 @1988 IEEE

                                LAKE SUPERIOR
                                                             in a zone from 653-1290m where the red crab
                                    P                        Geryon Quinquedens is the dominant
                                                             megafaunal invertebrate both in terms of
                                                             density and biomass (9). The surface of the
                                                             sediments on the upper slope is
                                                             characterized by many mounds and shallow
                                                             depressions (Figure 5). The most common
                        WISCONSIN                            features are produced by Geryon, and may
                                                             include depressions and complexes up to a
                                                             meter in diameter (10,11,12). This species
                                                             is known to actively burrow into the
                                                             sediment seeking shelter and food (13) and
                                                             can significantly alter the physical and
                 1 10 20 30 40 KM         ONTARIO            biological structure of the seafloor.

                                             4.                     Zp,

                                                                     @A, @F,
                                 on

                                       A.

                                            01

              Figure 1. General and specific dive
              locations for VSPC studies in Lake
                                                                                       2",
              Superior, USA.

                                                             Figure 3. Burbot (Lota lota)   trench-like
                                                             burrow system found in the Lake Superior
                                                             dive area shown in Figure 1. Burbot in
                                                             residence: fish is approximately 50cm in
                                                             total length.

                                                                                                CAPE CW

                                                                                             HOLE

                           v

              Figure 2. Bottom microtopography  from the
              Lake Superior dive site shown in  Figure 1.
              Dish-shaped burrows are produced  by the
              deep-water sculpin (Myoxocephalus
              thompsoni) in approximately 350m water
              depths. "Burrows" are about 8-15 cm
              diameter.
                                                             Figure 4. Dive site on the old DOS station
              bottom station off southern New England        location on the upper continental slope off
              (Figure 4), located approximately 100 miles    southern New England in approximately 750m.
              equidistant from Martha's Vineyard, Block
              Island, and the tip of Long Island, at a
              depth of 750-800m. This site sits squarely

                                                           444

                                                                      MATERIALS AND METHODS

                                                                All of the experimental dive work was
                                                            conducted using Harbor Branch Oceanographic
                                                            Institution's vessels, the R/V Seward
                                                            Johnson and the DSR/V Johnson Sea Link II.

                                                                The total VSPC system includes the
                                                            prism with an aluminum "skin", handles,
                                                            radon lights, a CCD camera, waterproof
                                                            housing and cable terminations, cable
                     _71
                                  -! 1/ -0                  system, control panel, a 411 black and white
                                                            SONY Watchman, a broadcast quality JVC
                                                               -VHS VCR with audio dubbing, remote
                                                            mini
                                                            control, and 20 minute cassettes (Figure 6)

            Figure 5. Red crab (Geryon quinquedens)
            burrow complexes typical of those examined
            with the VSPC at the dive site shown in           VIDEO PROFILE CA@IERR SYSTEM
            Figure 4. Burrow complexes may be as much
            as one meter across; burrow openings are            CONTROL PANEL    THROUGH
                                                                                                VICEO
            typically 10-15cm in diameter.                                                      SEDIMENT-
                                                                                                111@11E
                                                                                                  M.RA,SYST:M
                                                               d..

                                                                                                      Ik-

                       PREVIOUS VSPC STUDIES

                                                                                                    d
                A low-resolution, CCD VSPC system
            designed specifically for use with manned        RECOROE
            submersibles was deployed as a prototype on       MICROPHONE REMOTE CONTROL soNy
                                                                              IATCHMRN
            NOAA's NURP-UCAP Lake Superior dive
            projects in 1985 and 1986. This system
            provides instantaneous in-situ information
            on the SWI, and aids in the precise             Figure 6. Schematic of prototype VSPC
            sampling with tube cores, box cores,            system, with components connected as in
            enabling deployment of in-situ                  operation aboard the submersible.
            manipulative experiments in known sub-
            surface sediment conditions. Specifically,
            vertical and horizontal heterogeneity in
            sediment thickness, general bioturbational           Deployment of the VSPC is similar to
            features, and major sedimentary structures      the sequences involved in taking a sub-
            were visible from primary imagery in real       operated box core, except that the prism
            time, on scale from tens of centimeters to      must go in as orthogonally to the SWI as
            approximately one centimeter (3,14).            possible. The VSPC is lifted clear of its
                                                            receptacle and placed carefully above a
                 In 1987, deployments in a much  larger     selected area of the seafloor to be
            scale bioturbational system allowed             sampled. The prism is lowered into the
            detailed observation, video observation and     sediment gently; with all power, lights,
            image enhancement of red crab burrow            and VCR system and monitor on, both the
            complexes off the southern New England          observer and the sub pilot can see the
            upper continental slope (11,15). In 1988,       prism entering the sediment directly from
            through NURP-UCAP support, we have              the sphere and also from the view of the
            increased the resolution with a SONY XC-77      internal CCD camera. Therefore,
            CCD (570h x 475v TV lines), enhanced our        immediately apparent if the system works,
            image acquisition and storage with a            and real-time, in situ observation of the
            TRUEVISION MS Targa ICB board and TIPS          SWI can be recorded. Information on time,
            software, and our ability to quantitatively     sample number, locality, and other
            analyze the imagery with IMAGEPRO software.     parameters can be added to the VSPC
            This VSPC work confirms the concept that a      original tape on the audio track and this
            detailed view of the SWI and local benthic
                                                                R

            environs requires information from many         information can be cross-referenced with
            complimentary techniques.                       the main sub VCR audio tape record (3).

                                                         445

                                 RESULTS                        Center for Great Lakes Studies, University
                                                                of Wisconsin-Milwaukee.
                    During 12 dives with  the DSR/V Johnson
               Sea Link I to 750 m on the southern New                           REFERENCES
               England upper continental slope, and 7
               dives with the JSL II in Lake Superior we        (1)  Rhoads, D.C., and Boyer, L.F. 1982.
               were able to "dissect" the burrow                The effects of marine benthos on physical
               structures of the red crab (Geryon               properties of sediments: A successional
               cruinqueden@q) and the V-shaped, flared          perspective. p. 3-52. In P.L. McCall, and
               burrows of the burbot (Lota lota) by             M.J.S. Tevesz [eds.], Animal-sediment
               sequentially coring with tube cores and box      Relations. Plenum Press.
               cores down the axes of these systems, and
               inside and outside of the biogenically           (2) McCall, P.L., and M.J.S. Tevesz.
               influenced areas (4,5,12). At the same           (eds.) 1982. Animal-Sediment Relations:
               tine, we obtained live, in-situ VSPC             Plenum Press.
               imagery. The VSPC system was deployed in
               the same locations, or the same sequence of      (3)  Boyer, L. F., and Hedrick, J. A.
               locations in similar burrow complexes, as        1989. Submersible-deployed video-sediment-
               were the samples from the coring transects.      profile camera system for benthic studies
               A video excerpt from the dive sequences in       (Special Lake Superior submersible
               Lake Superior and The New England Slope          symposium: Jour. Great Lakes Research).
               will illustrate the microtopographic relief
               and textural details created by these two        (4) Boyer, L.F., Grassle, J.F.,
               bioturbators at the SWI as well as the           Whitlatch, R.B., and Zajac, R.N. 1988. Red
               details of their respective burrow               crab bioturbation on the Southern New
               complexes.                                       England Slope: The L.A.S.S.E. project. East
                                                                Coast Benthic Ecology Meetings, Abstracts
                                                                with Programs, April 8-11, Portland, ME.
                                 SUMMARY
                                                                (5) Whitlatch, R.B., Zajac, R.N., Boyer,
               1)   The VSPC images provide  a unique and       L.F., and Grassle, J.F. 1988. The effects.
               complimentary perspective of  the profundal      of the Deep sea red crab (Geryon)
               sedimentary habitat.                             Disturbance on the southern New England
                                                                upper continental slope. East Coast Benthic
               2)   Video images provide real-time              Ecology Meetings, Abstracts with Programs,
               information on the spatial heterogeneity of      April 8-11, Portland, ME.
               the SWI, and thus allow for choice in
               selectively sampling the profundal benthic
               environment from manned submersibles or          (6)  Boyer, L.F., and Whitlatch, R.B.
               ROVs at critical scales.                         1989. Organism-sediment relationships in
                                                                the Caribou Island Basin, Lake Superior,
               3)   The VSPC system, in  conjunction with       U.S.A. (Lake Superior submersible
               the sub, allows examination of the micro-        symposium: Jour. Great Lakes Research).
               structural details of physical and biogenic
               sedimentary features that are sparsely           (7)  Matheson, D.H. and Munawar, M. 1978.
               distributed.                                     Lake Superior Basin and its development.
                                                                Jour. Great Lakes Res. 4(3-4):219-263.
               4)   vsPc images should not replace other        (8) Boyer, L.F., Cooper, R.A., Long,
               sampling techniquesf but rather be used as       D.T., and Askew, T. 1989. Bioerosion and
               a unique and very complimentary view of          shelter formation by the burbot Lota lota
               benthic systems.                                 in the deep basins of Lake Superior. (Lake
                                                                Superior submersible symposium:Jour. Great
                                                                Lakes Research).
                             ACKNOWLEDGEMENTS
                                                                (9) Haedrich, R.L., G.T. Rowe, and P.T.
                    Ocean Instruments provided the VSPC         Polloni. 1980. The megabenthic fauna of the
               prototypes, NOAA's NURP-UCAP the ship and        deep-sea south of New England. Deep-Sea
               sub crews of the R/V Seward Johnson and          Res.
               DSR/V1s Johnson Sea Link I and II, the
               University of Wisconsin provided                 (10) Grassle, J.F., H.L. Sanders, R.R.
               photographic and cartographic services.          Hessler, G.T. Rowe and T. McLellan. 1975.
               This work was funded in part by the              Patterns and  zonation -- a study of the
               University of Wisconsin Sea Grant Institute      bathyal megafauna using the research
               under grants from the National Sea Grant         submersible Alvin. Deep-Sea Res. 22: 457-
               College Program, NOAA, U.S. Department of        481.
               Commerce, and from the State of Wisconsin.
               Federal Grant NA8YAA-D-0065, Project R/MW-
               38-PD. NURP-UCAP PSA grant 1987,188. This
               article is contribution # 325 from the

                                                              446

            (11) Wigley, R.L., and R.B. Theroux. 1981.
            Atlantic continental shelf and slope of the
            United States--Macrobenthic invertebrate
            fauna of the middle Atlantic Bight region--
            Faunal composition and quantitative
            distribution. U.S.G.S. Prof Paper 529-N,
            198 pp.

            (12) Boyer, L.F., and McCall, P.L. 1988.
            Video-Sediment-Profile Camera (VSPC)
            perspectives of Red Crab burrow systems.
            East Coast Benthic Ecology Meetings,
            Abstracts with Programs, April 8-11,
            Portland, ME.

            (13) Valentine, P.C., J.R. Uzmann, and
            R.A. Cooper. 1980. Geology and biology of
            Oceanographer submarine canyon. Mar. Geol.
            38:283-312.

            (14) Rhoads, D.C., and Germano, J.D.,
            1986, Interpreting long-term changes in
            benthic community structure: a new
            protocol. Hydrobiologia. 142:291-308.

            (15) Boyer, L.F., R.J. Diaz, and J.A.
            Hedrick. This issue. Computer image
            analysis techniques and video-sediment-
            profile camera enhancements provide a
            unique and quantitative view of life at or
            beneath the sediment-water interface.

                                                        447

                         COMPUTER IMAGE-ANALYSIS TECHNIQUES AND VIDEO-SEDIMENT-PROFILE CAMERA
                                 ENHANCEMENTS PROVIDE A UNIQUE AND QUANTITATIVE VIEW
                                  OF LIFE AT OR BENEATH THE SEDIMENT-WATER INTERFACE

                                       Boyer, L.F.1, Diaz, R.J.2, Hedrick, J.D.3

                       1. Geol. Dept. & Centr. Grt. Lakes Studies, UWM, Box 413, Mil, WI 53201
                                2. V.I.M.S., William and Mary, Gloucester Pt., VA 23062
                             3. Ocean Instruments, 5312 Banks Street, San Diego, CA 92110

              A video-sediment-profile camera system for       providing in-situ sediment sampling
              in-situ imaging of bottom sediments has          strategy, however, the resolution of the
              evolved in 3 stages: (1) A low-resolution        stored imagery was poor (2). In 1986
              (280h x 350v) CCD system with 1/211 VHS as       deployments, optical enhancements and
              the storage/viewing medium; (2) enhanced         manual digitization of the images provided
              optics and manual digitization of the            a much better, yet still low-resolution
              stored images; and, (3) a higher                 picture of the benthic sedimentary
              resolution CCD (570h x 475v) system--images      structures in Lake Superior (2). In 1987,
              are recorded on broadcast-quality 1/211          VSPC deployments were in a much larger-
              tape, captured frame-by-frame on a               scale bioturbational system, which allowed
              TRUEVISIONTM image capture board and             detailed observation, video documentation
              altered with TIPSTM and IMAGEPROtM               and image enhancement of red crab (Geryon
              software. The VSPC was used in Lake              quinquedens) burrow complexes at 750m off
              Superior in 185, 186,and 1188 to probe           the southern New England upper continental
              burbot (Lota lota) biogenic structures, and      slope (1,3,4,5).
              in 1987 on the upper continental slope   off          In our 1988 dive sequences, examining
              so. New England to dissect red crab (Geryon      burbot (Lota lota) trench systems in 350m
              quinguedena) burrows. Two image sequences        in the deep basins of Lake Superior, we
              are analyzed for contrast and dynamic            increased the video resolution with a SONY
              range, then contrast enhancement, and            XC-77 CCD (570h x 475v) camera module. In
              histogram equalization were applied to           addition, we have enhanced our image
              enhance sedimentary structures.                  acquisition and storage with a TRUEVISIONTM
                                                               M8 Targa image capture board (ICB) and
                                                               TIPSTM software, and our ability to analyze
                                                               the imagery with IMAGEPROTM software.
                              INTRODUCTION                          In this paper, the original video
                                                               images will be displayed to illustrate the
                   This paper very briefly describes the       narrow ranges of contrast and low dynamic
              developmental stages and deployments made        range present in both the Lake Superior and
              with a prototype charge-coupled-display          New England Slope sediments. After
              (CCD) video-sediment-profile camera (VSPC)       analyzing grey scale ranges to pinpoint the
              system, specifically designed for use with       range necessary to maximize image contrast,
              manned submersibles (1,2). The major             the images will be enhanced through
              thrust of this work was to examine the           histogram equalization. In the future, RPD
              original in-situ video images within             area, depth, and the size of physical and
              biogenic sedimentary structures from two         biogenic sediment structures, etc., can be
              selected profundal marine and lacustrine         calculated from the images after these
              environments (1,2,3,4). The original video       enhancements. Video-sediment-profile
              was captured frame-by-frame, and then            camera (VSPC) imagery provides the only
              enhanced and manipulated.                        real-time in-situ view of qualitative and
                   The VSPC imaging system has undergone       quantitative structures and processes in
              three stages of prototype development. A         deep marine and freshwater environments in
              low-resolution (280h x 350v TV lines) B&W        concert with manned submersibles (1,2).
              CCD, fitted to a custom housing,
              incorporating a solid acrylic prism, was                         STUDY SITES
              successfully deployed from the DSR/
              Johnson Sea Link II in 1985 at 350m in the            These studies were conducted in two
              Caribou Isia_@d Basin of Lake Superior           locations; the Caribou Island Basin in
              (1,2). This real-time video imagery of           Lake Superior, and an upper continental
              conditions at and below the sediment-water       slope bottom station off southern New
              interface (SWI) was extremely useful for         England (1,2,6). These areas contain

                                             CH2585-8/88/oooo- 448 $1 @1988 IEEE

           numerous biogenic sedimentary structures--       inside the burrow. The burrow and internal
           Lake Superior has burrow complexes and           sedimentary features are extremely
           trenches created by the burbot (Lota lota);      difficult to discern due to low contrast
           a zone from 653-1290m on the slope contains      and dynamic range in the ambient sediments.
           depressions and complexes up to a meter in       Figure 2c is an histogram of grey scale
           diameter, created by the red crab (Geryon        dynamic range and spread (ie. max of 0-256
           quinquedens). These organisms can                levels) in the burrow sediments along a
           significantly alter the physical and             profile transect. Note the very narrow peak
           biological structure of the bottom               (low contrast range), yet relatively high
           sediments (l,2,3,4,5,6,7).                       values per index (dynamic range within the
                                                            available grey level). To enhance the
                      MATERIALS AND METHODS                 internal features (Figure 2d), histogram
                                                            equalization multiplies each pixel's grey
                All of our experimental dive work was       level from the original image by an
           conducted using the Harbor Branch                algorithm where each pixel's range in the
           Oceanographic Institution's DSR/     Johnson     image is stretched over as large a segment
           Sea Link I and 11 (1,2). The total VSPC          of the 256 levels as possible, and the
           system is illustrated in Figure 1    (1,2).      dynamic range is smoothed (IMAGEPROTM,
           Deployment of the VSPC is similar to the         Media Cybernetics). Fluidized sediment
           sequences involved in taking a sub-              fill, infaunal burrow structures, and the
           operated box core, except that the prism         average mixed depth (as confirmed in X-rays
           must go in (and remain precisely) at right       and cores) are now visible.
           angles to the plane of the SWI (1,2).                 The next sequence of VSPC images
                video images were recorded in real          documents a burbot trench at 300m in Lake
           time in the front sphere of the sub. The         Superior(Figure 3a-g). This sequence
           tapes (1985-86) were then played on a            illustrates the trench edge morphology from
           broadcast quality VHS system, filtered,          the surface down to the internal burrow
           and the raster images were photographed          fill structure at the base of the trench.
           with 35mm Ektachrome, and finally                Once again, the original image of the
           printed.These photo images were digitized        internal structure of the trench bottom
           by hand at 1/411 by 1/411 grid scales, and       sediments is examined (Figure 3a-d). In a)
           reproduced at scale usinga Zenith 158 PC         The sides of the trench and the fluid
           and a Prodesign II CAD program (2). Video        reworked fill material are visible looking
           images from 1987 and 1988 dives were             toward the shallow end. The upper portion
           replayed directly into the TRUEVISIONTM          of the burbot trench is visible in b),
           Targa M8 Image Capture Board. The video          where the left side of the photo shows the
           was captured frame-by-frame at 1/30 second       sharp edge of the excavation--the VSPC has
           and analyzed with IMAGEpROTM scientific          not penetrated the bottom of the trench
           imaging software, specifically for grey          even at 18-20 cm deeper than the SWI. The
           scale range or overall image contrast, and       lower portion of the trench excavation is
           dynamic range of the available grey              visible in c). The left side shows the
           levels. Then, an appropriate histogram           further penetration of the VSPC into the
           equalization algorithm (IMAGEPROTM Manual,       excavated trench, with the bottom sediments
           version 1.06.05, Media Cybernetics) was          just visible at the lower portion of the
           used to change the spread of the image           image, and in d), the image of the internal
           contrast. These images can then be edited,       burrow/trench sediments displays the 'IV"
           with text and graphicsMplaced directly on        shaped cut of the trench excavation filled
           them, with HALOVISIONT software (Media           with sediments. This image was then
           Cybernetics).                                    analyzed for grey level contrast and
                                                            dynamic range (Figure 3e). Note the
                              RESULTS                       extremely narrow grey level contrast range,
                                                            yet high dynamic range. Then the image was
                Figures 2a-d, and 3a-g show two             enhanced (Figure 3f) and mapped onto the
           examples of the utility of the VSPC system       original image (Figure 3g). The enhanced
           coupled with image enhancement and               image shows fluidized burrow sediment fill,
           manipulation techniques. Figure 2a-d             reworked and mixed/transported infilling
           documents the VSPC imagery through a   red       sediment, the sharp boundary between
           crab burrow and into the internal                sediment and the overlying water, and
           sediments. Figure 3a-g illustrates a             between the infilling sediments and the
           sequence of VSPC images through the burbot       original excavation in the highly cohesive
           trench system down into the underlying           post-glacial clays.
           post-glacial clays.
                Figure 2a illustrates a red crab
           burrow opening. The highly textured surface
           sediments sculpted by the crab chelae and
           legs are visible around the undercut burrow
           excavation. Interior burro   fill is just
           visible below. Figure 2b i( the original
           VSPC image from SWI, down 15-20cm deep

                                                          449

                                SUMMARY                                       REFERENCES

                   The utility of the VSPC and image          (1) Boyer, L.F. this issue. Video-Sediment-
              analysis techniques opens new avenues for       Profile Camera imagery in marine and
              studying the structures, organisms, and         freshwater benthic environments. OCEANS 88.
              processes at and beneath the sediment-water
              interface in marine and freshwater              (2)  Boyer, L.F., and Hedrick, J.A. 1989.
              profundal environments.                         Submersible-deployed video-sediment-
                                                              profile camera system for benthic studies
                                                              (Special Lake Superior submersible
                           ACKNOWLEDGEMENTS
                                                              symposium: Jour. Great Lakes Research).'
                   Ocean Instruments provided the VSPC        (3)  Boyer, L.F., and McCall, P.L. 1988.
              prototypes, NOAA's NURP-UCAP the ship and       Video-Sediment-Profile Camera (VSPC)
              sub crews of the R/V Seward Johnson and         perspectives of Red Crab burrow systems.
              DSRI Is Johnson Sea Link I and _I1, the         East Coast Benthic Ecology Meetings,
              University of Wisconsin provided                Abstracts with Programs, April 8-11,
              photographic and cartographic services.         Portland, ME.
              This work was funded in part 1py the
              University of Wisconsin Sea Grant Institute     (4) Boyer, L.F., Grassle, J.F.,
              under grants from the National Sea Grant        Whitlatch, R.B., and Zajac, R.N. 1988. Red
              College Program, NOAA, U.S. Department of       crab bioturbation on the Southern New
              Commerce, and from the State of Wisconsin.      England Slope: The L.A.S.S.E. project. East
              Federal Grant NABYAA-D-0065, Project R/MW-      Coast Benthic Ecology Meetings, Abstracts
              38-PD. NURP-UCAP PSA grant 1987,188. This       with Programs, April 8-11, Portland, ME.
              article is contribution # 326 from the
              Center for Great Lakes Studies, University      (5) Whitlatch, R.B., Zajac, R.N., Boyer,
              of Wisconsin-Milwaukee.                         L.F., and Grassle, J.F. 1968. The effects
                                                              of the Deep sea red crab (Geryon)
                                                              Disturbance on the southern New England
                                                              upper continental slope. East Coast Benthic
                                                              Ecology Meetings, Abstracts with Programs,
                                                              April 8-11, Portland, ME.

                                                              (6) Boyer, L.F., and Whitlatch, R.B.
                                                              1989. Organism-sediment relationships in
                                                              the Caribou Island Basin, Lake Superior,
                                                              U.S.A. (Lake Superior submersible
                                                              symposium: Jour. Great Lakes Research).

                                                              (7) Boyer, L.F., Cooper, R.A., Long,
                                    _0
                                                              D.T., and Askew, T. 1989. Bioerosion and
                                   - Ww
                                    ZA4                       shelter formation by the burbot Lota lota
                                                              in the deep basins of Lake Superior. (Lake
                                                              Superior submersible symposium: Jour. Great
                                                              Lakes Research).

              Figure 1. The VSPC system. The system
              includes the prism with an aluminum "skin".
              handles, radon lights, a CCD camera,
              waterproof housing and cable terminations,
              cable system, control panel, a 411 black and
              white SONY Watchman, a broadcast quality
              JVC mini-VHS VCR with audio dubbing, remote
              control, and 20 minute cassettes.

                                                          450

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              Figure 2a-d. VSPC Sequence through a red crab burrow interior  captured frame-by-
              frame on a TRUEVISIONTM Targa M8 board. Screen resolution 512  x 480, 35mm
              ektachrome/interneg/to B&W print. a) Red crab burrow opening.  Average diameters
              typically 10-15cm. The highly textured surface sediments are visible around the
              undercut burrow excavation. Interior burrow fill just visible below. b) Original VSPC
              image from SWI down 15-20cm deep inside the burrow. The burrow and internal
              sedimentary features are extremely difficult to discern due to low contrast and
              dynamic range in the ambient sediments. c) Histogram of grey scale dynamic range and
              spread in the burrow sediments along a profile transect. Note the very narrow peak,
              yet relatively high values per index. d) Histogram equalization of the original image.
              (IMAGEPROTM, Media Cybernetics). Fluidized sediment fill, infaunal burrow structures,
              and the average mixed depth (as confirmed in X-rays and cores) are now visible.

                                                        451

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               Figure 3a-d. Sequence of VSPC images in a burbot trench. This sequence illustrates the
              .trench edge morphology from the surface down to the internal burrow fill structure at
               the base of the trench. a)View of the trench at the SWI through the "eyes" of the
               VSPC. The sides of the trench and the material are visible. b) The upper portion of
               the burbot trench. The left side of the photo shows the sharp edge of the excavation,
               the VSPC has not penetrated the bottom of the trench at 18-20 cm. c) The lower portion
               of the trench excavation. The left side shows the further penetration of the VSPC into
               the excavated trench, with the bottom sediments just visible at the lower portion of
               the image. d) The VSPC image of the internal burrow/trench sediments with the 'IV',
               shaped cut of the trench excavation visible filled with sediments.

                                                         452

                  Burbot Trench systems
                  Deep interior structure

                                              water J

                   fluidiied
                       muds

                                       fill
                           e=&41 Una
                               efte

                  post-glacial clays
            g)

             Figure 3e-g. Sequence of VSPC images in a burbot trench. This sequence illustrates the
             trench edge morphology from the surface down to the internal burrow fill structure at
             the base of the trench. e) The grey level contrast and dynamic range of the internal
             sediments of the burbot trench. Note the extremely narrow grey level contrast range,
             yet high dynamic range. f) The enhanced image of the internal structure of the burbot
             trench. g) The enhanced image with fluidized burrow sediment fill, reworked and
             mixed/transported infilling sediment, and the sharp boundary between sediment and the
             overlying water, and between the infilling sediments and the original excavation in
             the highly cohesive post-glacial clays.

                                                       453

                                     APPLICATION OF THE POLARIMETRIC MATCHED IMAGE FILTER (PMIF) TECHNIQUE TO
                                             CLUTTER REMOVAL IN POL-SAR IMAGES OF THE OCEAN ENVIRONMENT

                                 Wolfgang-M. Boerner, Alexander B. Kostinski, Brian D. James, and Matthias Walther

                                         Communications Laboratory (m/c 154), Dept. of Electrical Eng. &
                                            Computer Sci., University of Illinois at Chicago, SEL-4210,
                                                    840 W. Taylor St., Chicago, IL/USA 60680-4348

                                         ABSTRACT                                 recently. Such data, taken with the NASA/JPL
                                                                                  CV-990 dual-polarization L-band (1.225 GHZ)
                                                                                  SAR (Synthetic Aperture Radar) system, have
                    We focus on       image contrast       optimization           been made     available to us.          Here,    we
                    between two rough surface classes, which is                   investigate the potential        of a      strictly
                    based strictly on polarimetric filtering and,                 polarimetric image filteri   ,ng which takes full
                    therefore,     no   digital     image    processing           advantage of the matrix data provided on a
                    techniques are employed.        The approach is               pixel by pixel basis, and complements the
                    tested on a complete polarimetric synthetic                   existing scalar contrast optimization           and
                    aperture radar image of the San Francisco Bay                 speckle reduction techniques.        We wish to
                    area (NASA/JPL CV-990 L-band POL-SAR data).                   stress from the outset that our goal is
                    Optimal transmitted polarizations are found                   contrast optimization (with the corresponding
                    for each image pixel and the results are                      speckle reduction)      without the      help    of
                    analyzed statistically via a set of joint 2D                  incoherent averaging over pixels or "looks",
                    histograms.    This is done for both of the                   because of the corresponding loss of spatial
                    rough surface classes. The image response to                  or temporal resolution.        At first glance,
                    the "optimal" incident polarization is then                   speckle reduction      is    impossible     without
                    simulated digitally by adjusting the receiver                 incoherent averaging but further consideration
                    polarization according to the modes of the                    shows that it is so only for scalar data.
                    histograms.      The corresponding images are                 Indeed, taking "projections" onto the receiver
                    computed and displayed with s   Iignificant image             direction in the polarization space decreases
                    contrast improvement.                                         amplitude fluctuations and an image appears
                                                                                  less speckled. The goal of this paper is to
                                                                                  find such a       choice of the      polarization
                                                                                  projection which makes a given rough surface
                                                                                  @lass least speckled and, by doing so, to
                                                                                  improve the image contrast between two given
                                     1. INTRODUCTION                              classes.
                   This. paper addresses the problem of coherent                  The paper is structured as follows: a brief
                   image contrast optimization between two rough                  @escription of basic polarimetric definitions
                   surface classes.      We focus on such contrast                is provided in Section II, while in Section
                   which    is    due   to    the   differences      in           III the image data are described and the
                   polarimetric scattering from one rough surface                 precise problem formulation is given.            In
                   to another.     The novelty of this problem is                 Section IV,     our three-stage      polarimetric
                   due to the combination of coherent imaging and                 optimization    procedure     is   outlined     and
                   polarimetric       scattering.        The    former            implemented for each image pixel. In Section
                   introduces speckle reduction as a major issue                  V, we make the transition from the single
                   while the latter provides the full scattering                  pixel result to a combined description.           A
                   matrix      (i.e.,      complete      polarization             statistical analysis of the results is given,
                   information) per   image pixel. The second and                 and the images are displayed and discussed.
                   equally important task of this work is to                      The operation of the polarimetric matched
                   develop efficient      statistical     tools     for           filter is summarized in Section VI.         Section
                   polarimetric image data analysis and speckle                   VII contains concluding remarks.
                   reduction techniques.
                                                                                      II. ESSENTIAL POLARIMETRIC DEFINITIONS
                   Speckle has long been recognized as the main
                   problem of coherent imaging (l)- and many                      Following (2), we define the origin of the
                   processing techniques have been advanced to                    coordinate system at the receiving antenna
                   overcome it.      The vast majority of these                   terminals with the +2-axis directed toward the
                   techniques, however, are of a.scalar nature                    target (pixel) as shown in Fig. 1. Note that
                   simply because vector/matrix imaging data are                  in   SAR    applications     the   receiver     and
                   so sparse and have become available only very                  transmitter are      co-located    but   may     be

                                                         CH2585-8/88/0000- 454 $1 @1988 IEEE

                   different antennas so that the situation is                        new basis.      With these definitions we now
                   slightly bistatic. The reflected �R and the                        proceed to describe the polarimetric SAR image
                   transmitted E       waves,       together with      the            data and to       formulate the problem           more
                                     T                                                precisely.
                   antenna "height" h          (polarization of        the
                   receiving antenna @5hen used as transmitter                            III. IMAGE DATA DESCRIPTION AND PROBLEM
                   (2)), can all be written as plane waves                                                 FORMULATION
                   [lal   9T     (E  2+ E2 )@[cos ' + sinYT ej@T y^1                  The 4096 x 1024 SAR image of the San Francisco
                                     TI    T2       YTX                               Bay area (6,7) is shown in Fig. 2a for
                                                exp Jj(wt - kz + aT)J                 horizontal      transmitter        and       receiver
                                                                                      polarizations (HH).      The brightness of each
                                                                                      pixel is assigned according to the total
                   [lb)          (E2 + 4 )@[cos         + siny ej@R Y]                received energy in the horizontal channel.
                                     R              YRx        R                      The data was taken with a dual-polarized
                                     x      y . exp fj(wt + kz + aR)l                 antenna and a four-channel receiver system so
                                                                                      that a complete scattering matrix was measured
                                                                                      for each image pixel.        The radar wavelength
                   (1c]          W + h2) [cosyhx + sinyh ej@h, Y@]                    was 24.5 cm and the resolution (size of each
                                     X   y                                            pixel size) was about 10m x 10m (see (6) for
                                            exp, (j(wt - kz + ah))                    more details).      The image texture can be
                                                                                      roughly classified into three main categories:
                   where in all equations y =_ tan-1     (EY/Ex), and                 man-made structures (ships, the bridge, urban
                                                                                      area, etc.), vegetated area (park), and the
                   and m are the relative and absolute phases,                        ocean region.       All three classes can be
                   respectively (2).        From here on, we will                     considered rough at 24.5      cm according to the
                   operate with       the expressions        in     square            Rayleigh criterion        (1).       This      surface
                   brackets, written as complex normalized 2D                         roughness leads to a random modulation of
                   vectors (also known as Jones vectors (3) in                        phase of the reflected wave which, in turn,
                   optics and spinors in quantum mechanics (.4)),                     produces image speckle (1).
                   e.g.,
                                                                                      Any kind of averaging is likely to smoothen
                               COSYT                                                  the image and reduce speckle. As an example
                                                                                      of averaging in polarization space, the span
                   ET       sinyT ej@                                                 of [S] image (sum of the magnitudes of all
                                      TI            EV IT-                            four scattering matrix elements) is shown on
                   when usual assumptions about a linear passive                      Fig. 2b.        The   image is essentially          an
                   medium     are    employed,      the     input-output              incoherent superposition of the four separate
                   polarization ellipse characteristics of                a           polarization images obtained per pixel and,
                   target (image       pixel) are      given by       its             therefore, a      noticable speckle         reduction
                   scattering.matrix defined as                                       (relative to the HH image) is not surprising,
                                                                                      (8).   As was mentioned above, this paper
                   (21       ER = [SIET                                               focuses on      contrast optimization         without
                                                                                      incoherent averaging of any kind.
                   where [S] is a 2 x 2 complex matrix,       and o;r   is            Since a     complete      scattering     matrix     is
                   set to zero by the choice of the time origin                       available for every pixel of each of the three
                           Finally, the voltage at the receiving                      categories, one can simulate the response of
                   antenna terminals as a function of transmitter                     the area to any transmitted polarization E        T by
                   and receiver polarizations is given by                             calculating E   R via [2).        Furthermore, the
                   (31       V = t   T     tT[S]FT                                    response of the image can also be simulated
                                                                                      for an arbitrary receiver polarization h via
                                                                                      [3]. Both equations must be implemente-a for
                   where superscript T denotes the transpose           (as            each pixel      of the entire        image.       The
                                                                                      brightness is then assigned to each pixel
                   opposed to hermitian conjugate - see (2,           pp.                                          T    * T
                   1471-1473), and (5)         for details).          For             according to P =- V V   =  (h ER) (h E          stands
                   reference,.we also include the transformation                                                              R
                   properties of [S] and V from one polarization                      for complex conjugate).             Such    numerical
                   basis    to    another     using . a      similarity               simulations were recently carried out by the
                   transformation for    [S] to [S] as discussed in                   JPL group (6,7), demonstrating the ability of
                   (2, pp. 1471-1473),                                                polarimetric      adjustment     to     substantially
                                                                                      improve image contrast.       our goal here is to
                   [4a]      [S], = [U1_l   ISHUI                                     develop an algorithm for the search of optimal
                                                                                      image contrast via the combination of our
                                                                                      recently developed Three-Stage-Procedure (TSP)
                   [4b]      V = V - h'    T(U]  T[U]E.1     TE                       which is described in the following section,
                                                             _R                       and a subsequent statistical analysis of the
                                                                                      set of polarization eigenvectors computed with
                   where [U] is the unitary            change-of-basis                the TSP for each pixel. Again, we emphasize
                   matrix and primes indicate quantities in the                       that our algorithm must not include               any

                                                                             4

                     incoherent..... averaging      and/or      smoothing            [7b]      V = h TE
                     procedures because of the corresponding loss                                     _R    0-
                     of information, e.g., temporal (phase) or
                     spatial resolution. In this paper we focus on                   In terms of   imaging applications, one expects
                     finding    such    transmitter     and     receiver             a given pixel to look relatively "bright" when
                     polarizations that allow significant ocean                          corresponds to the largest           eigenvalue
                     clutter removal for better contrast with the                    h
                     urban     area    and    ship/man-made     structure            (maximal energy density) and h is adjusted
                     identification. The      method and implementation              according to [7a], while the aajustment [7b]
                     of the optimal polarization search for a                        ensures    that    the    pixel     looks     "dark",
                     single pixel are briefly described in the next                  especially when supplemented with the choice
                     section, after which        we proceed to        the            of minimal E    T,opt.      These     observations,
                     statistical      analysis    of    the     results.             together with the statistical considerations,
                                                                                     constitute     the    basis    of    pixel-by-pixel
                               IV. THE THREE-STAGE PROCEDURE                         polarimetric image filtering.
                     The TSP addresses the following problem (see                          V. STATISTICAL ANALYSIS OF OPTIMAL
                     (2,5) for more details): For a given pixel                                  POLARIZATIONS AND IMAGING
                     (i.e., known scattering matrix), find such
                     transmitting and receiving polarizations, for                   Even  within a single rough surface class
                     which the received power is maximal (minimal).                  (e.g., ocean),      there is      a     considerable
                     In mathematical terms this means: find E     T and              variability in polarization properties               of
                     h such that P       A = ItT    [S]E 12  is optimal              pixels in any given patch and we, therefore,
                                                        T                            must introduce a statistical description at
                     for a given [S], subject to the constraints                     this stage.     we assume that the two terrain
                     JJhJJ = JJfTJJ                                                  classes are sufficiently different in their
                                                                                     polarimetric     responses      so    that      their
                     The TSP accomplishes this in three         separate             statistics do not "overlap" significantly.
                     stages (2):                                                     Then, with      proper statistical       tools,      a
                                                                                     "threshold" can be found such that the TSP can
                     Stage 1) The energy density in the         reflected            be used to "darken" not just one pixel but a
                     wave (before it has reached the receiver) is                    majority of pixels in a given class.
                     optimized as      a function       of   transmitted
                     polarizations via the following           eigenvalue            In order to gain insight into the polarimetric
                     problem                                                         response of      various     terrain    and     ocean
                                                                                     categories, we have performed Stage 1 of the
                     [5)       J[G] - X[IIJE  T,opt = 0                              TSP for each pixel of two chosen segments of
                                                                                     ocean and urban areas.        Let us consider the
                                        +                                            ocean vs. city contrast enhancement as a
                     where [G] a (S] (S] is by          construction a               specific application.       In order to minimize
                     hermitian matrix for any (S] (+ stands for                      the ocean return or to maximize the city
                     hermitian conjugate), [I] is the identity                       return, the minimum energy eigenvector is
                     matrix, and      �T,opt    is     the   eigenvector             computed for each pixel of the ocean patch and
                     corresponding to      the     largest     (smallest)            the maximum energy eigenvector is computed for
                     eigenvalue                   giving the largest                 @he city patch. The eigenvectors correspond-
                                  Xmax (\min)                                        ing to        , x     are computed according to
                     (smallest) energy density.        The eigenvalues                         'tin   max
                     are always real (they correspond to              the            [5) for each pixel and expressed in the form
                     measured values of energy density in the                        (2, p. 1400)
                     reflected wave) and the eigenvectors             are
                     orthogonal because [G] is hermitian (9).                        [8a) ET,Opt                                p - EY/EX
                     Stage 2) At this stage, the polarization       state                           fil -+Po*)
                     of the reflected wave is computed using the                     where p is the complex polarization ratio (3).
                     known ET,opt                                                    After the eigenvectors         are computed,         we
                     (61       ER        [S]E                                        express them in terms of the more convenient
                                 ,opt         T,opt*                                 ellipticity c and tilt T coordinates which
                                                                                     describe, respectively, the "fatness" and the
                     Stage 3)  Finally, the   receiver polarization is               inclination of the polarization ellipse. They
                     adjusted  to ensure that all of       the      power            are defined (3, p. 35) as
                     contained in E R,opt (reflected wave) is either                 [8b]       s = 1/2 arcsinJ21m(p)/(l-pp*))
                     absorbed or rejected,        depending    on     the
                     application. The former is accomplished with                    [8c]       T = 1/2 arctan[2Re(p)/(l-pp*)J.
                     the choice
                                                                                     Thus, an optimal polarization state which
                     Pal       h - E                                                 makes a given pixel darkest (brightest) is
                                     R                                               characterized by two         numbers, e and          T.
                                                                                     Naturally, one would like to choose                  the
                     while the latter   requires that                                incident polarization in such a way as to make
                                                                                     most ocean pixels dark if our goal is to

                                                                             456

                  contrast urban area against ocean or             to           image). The ocean area is quite a bit more
                  enhance visibility of ships at sea.       To this             speckled than on Fig..5a and the contrast with
                  end, we present in Figs. 3a-b joint              2D           the urban area is lower. on the other hand,
                  histograms (c and T) for the two surface                      there    is   a     better    contrast     between
                  categories of interest: statistics of minimal                 park/vegetated area and the urban          region.
                  eigenvectors are presented for the ocean, and                 Thus, the results of the JPL group (6)     as well
                  maximal eigenvectors for the urban           area.            as our experiments clearly show that       a much
                  Each patch contains 40,000 (200 X 200) pixels                 improved contrast can be achieved          between
                  so that the statistics are quite good.         Both           man-made, vegetated and ocean areas with the
                  histogram modes are near the linear vertical                  proper choice of    polarization.     Of course,
                  (c = 01, T = 900) polarization. Thus, if the                  when the rough surface is such that the
                  transmitter is adjusted to produce vertically                 scattering    is    polarimetrically     isotropic
                  polarized waves (relative to the direction of                 (i.e., there is       no spatial      polarization
                  propagation), the majority of the ocean pixels                dependence), this   technique cannot work (one
                  will have relatively low scattered energy,                    such example is       a random sea       surface).
                  while the  majority of city pixels will reflect               Fortunately, such cases are rather unlikely
                  strongly.   Once the optimal transmitted field                and all of the data available to us indicate
                  is chosen  and the scattered field is computed,               that real terrestrial rough surfaces exibit a
                  one can    use a similar procedure for the                    very strong polarization dependence.       Even an
                  receiver   adjustment.     In Figs. 4a-b,        we           ocean    surface    is   often    modulated      by
                  present the s-T histograms for the scattered                  well-defined internal wave patterns which show
                  fields of the two regions.      These histograms              up clearly in POL-SAR images.
                  were constructed by letting the incident wave
                  be vertically polarized and by computing the                  A sequence -of one-dimensional image brightness
                  scattered field of each pixel via Eq. 6.                      distributions  in Fig.6 illustrates the effect
                  Again, the two histograms peak around the same                of various stens of the above Drocedure on the
                  vertical polarization state and the ocean                     ocean and city patches, separately.            One
                  distribution is more pronounced. In fact, the                 notices a gradual improvement in contrast
                  ocean incident and scattered field histograms                 between the two categories as indicated by the
                  are quite similar which leads one to conclude                 decreasing overlap area       and better      peak
                  that most of the scattering matrices of the                   separation.       This    suggests    that     the
                  ocean region are "flat plate-like" identity                   h-adjustment is responsible for most of the
                  matrices. This behaviour is consistent with                   clutter removal,  as can also be seen on       the
                  Bragg scattering assumed to be the dominant                   actual images of  Figs. 5a and 5b. Note       that
                  physical mechanism of the ocean scattering                    identical uniform grey scale assignments      have
                  (6). The urban area histograms, on the other                  been used for all images so that the effects
                  hand, differ because   the scattered field does               are entirely polarimetric.
                  not have a peak at     horizontal polarization.
                  The fact that this     peak vanishes seems to                    VI. SUMMARY OF THE POLARIMETRIC MATCHED
                  disagree with the      assumption of      dihedral                             FILTER STRATEGY
                  corner reflectors (6) as the basic scattering
                  elements of the urban area., Indeed, in such a                In this section, we summarize and quantify the
                  case, the scattering matrix (having entries +1                approach outlined in the previous paper in a
                  along   the    diagonal    and    0   along     the           series of well-defined steps. Again, consider
                  off-diagonal) would produce a mild peak at                    the suppression of ocean clutter for optimal
                  horizontal polarizations      which would       not           contrast with man-made structures such as
                  disappear.                                                    ships, etc. we perform the first two steps of
                                                                                the TSP, and display the "typical" statistics
                  If the receiver is adjusted to horizontal                     of the ocean and urban area patches in a form
                  polarization, most of the energy of ocean                     of joint bivariate histograms of transmitted
                  pixels will be rejected because the receiver                  fT and received E R fields as is shown in Figs.
                  is perpendicular to the sharp histogram mode                  3a,b and 4a,b. we then identify the modes of
                  at vertical polarization.         The urban area              the two distributions E     and E and adjust h
                  will not be affected as much      because of the                                     -T         R
                  much larger spread.      when the brightness is               so that the "majority" (i.e., histogram peak)
                                                                                of the "unwanted" patch pixels "darken".       For
                  assigned according to P = V V (V is computed                  instance, if h is adjusted in such a way that
                  from Eq. 3), the image in Fig. 5a results.                    the peak    i-n the    ocean distribution       E
                  compared with the original HH image, this near                                                                  R
                  HV image has better contrast: the average                     satisfies
                  brightness ratio between the urban and the                    191      V          T
                  ocean areas increases; but, because of the                              peak      -ER,peak @ 01
                  fact that the two modes are not separated in
                  the polarization space, the urban area has
                  lost some structure.        Note, however, that               it is ensured that the majority of the ocean
                  most of the ocean speckle has been "filtered                  pixels will appear "black" on the actual
                  out" with the proper choice of polarization,                  image.
                  yet, without     significant effect       on    the
                  man-made structures.                                          The following procedure (see Fig. 7), which is
                                                                                a  statistical      extension   of    the     TSP,
                  The image of Fig. 5b was computed for the                     constitutes the polarimetric matched filter
                  vertical polarization of the receiver (near VV                for coherent imaging:

                                                                        457

                    1a) the energy density of each pixel is                     conjunction with the polarimetric enhancement,
                        maximized (minimized) as a function of                  should be directed towards the increase in
                        the    transmitted , polarization.        The           peak   sharpness    of    the   re@evant     field
                        corresponding eigenvectors,    !@T   , are found        distributions (e.g., N X N block averaging,
                        from Eq. 5 as in Stage 1 of TSP;                        discretization,     and   quantization,     etc.).
                                                                                Here, however, we concentrate strictly on
                    1b) the joint bivariate histograms       of ET (e           polarimetric        enhancement          methods.
                                                                                Furthermore, the polarimetric image contrast
                        and T) are constructed for           all rough          improves with the separation of the histograms
                        surface classes of interest;                            in the polarization space (two "spikes" with
                                                                                no overlap would correspond to a "black and
                    lc) the transmitted field E   T  is adjusted to             white" image with an ideal contrast). In this
                        either the peak of the minimal eigenvector              respect, the TSP was not successfull because
                        pdf of the unwanted region (e.g., to                    the scattered field histograms of ocean and
                        reject ocean clutter) or to the peak of                 the urban    area (Figs. 4a       and 4b)     are
                        the maximal eigenvector pdf of the region               approximately at the same c and T.        Another
                        of interest (e.g., bridge, urban         area,          approach would be to choose the transmitting
                        etc.). The choice depends on the relative               field in such a way as to maximize the peak
                        sharpness of the modes;                                 separation of the scattered field histograms.
                                                                                This approach is currently under investigation
                    2a) the scattered field         is computed   for           in our laboratory and preliminary results
                                                 R                              based on Monte-Carlo simulation of structures
                        each pixel for the E   T chosen in Step   1c,           in Rayleigh noise indicate better contrast
                        see Eq. 6 in Stage 2 of TSP;                            (relative to TSP) I but less efficient speckle
                                                                                reduction.
                    2b) as in Step lb, the joint (c and T)                      We wish to state here that an immediate
                        histograms of the scattered field E      Rare           objective of the research is to establish a
                        constructed.    The     histogram    mode    is         "tool-kit"   of     matrix   image     processing
                        identified.                                             techniques,, designed specifically for        the
                                                                                handling of polarimetric scattering matrix
                    3a) the receiver polarization h is adjusted                 data on a pixel-by-pixel basis. Consequently,
                        via Eqns. 7a or 7b to either match or                   we did not emphasize either the modeling or an
                        mismatch the polarization of the histogram              interpretation of     polarimetric      scattering
                        mode found in Step 2b;                                  patterns beyond some very basic          physical
                                                                                arguments based     on flat     plates,     corner
                    3b) P = V V (received power) is computed for                reflectors, Bragg scattering, etc.
                        each pixel as P           (JE        (hTE )
                           T[S]   * T              - -R      --R                                 ACKNOWLEDGEMENT
                        (h     ET) (h [S]E T    and the      resulting          This work was supported in part by the US Army
                        image is displayed.                                     Research    office    under     Contract      DAAK
                                 VII. CONCLUDING REMARKS                        21-84-C-0101, the US Office of Naval Research
                                                                                under Contract US ONR N00014-80-C-0773 and
                    The potential of complete polarimetric methods              N00019-85-K-0483, by      the   US   Naval    Air
                    for    radar   imaging     has    already     been          Development      Center      under       Contract,
                    convincingly demonstrated by the JPL group                  N62269-85-0383, and by the US        Army     Fort
                    (6.7). In this paper, we have attempted to                  Belvoir Research, Development and     Engineering
                    quantify and organize a search for optimal                  Center   under    Contract     DAAR-70-87-P-2565.
                    image contrast into a systematic polarimetric               Computations     were  carried    out    on   the
                    filtering method. In addition, no incoherent                UIC-EECS/CL     VAX-11/750   research    computer
                    pixel/look or spatial averaging was allowed.                facilities sponsored by equipment grants ONR
                    We have accomplished this by combining the TSP              N00014-80-C-0073E, ARO-DAAG 29-85-002, and by
                    search for     optimal     polarizations     on   a         the University of Illinois at Chicago Research
                    pixel-by-pixel    basis    with    a     subsequent         Board and Engineering College.
                    statistical     analysis     of          polarization       We wish to thank and acknowledge the interest
                    eigenvectors (versus surface category), and                 shown in our polarimetric research by Henry W.
                    the digital   adjustment of the polarimetric                Mullaney, Hans Dolezalek, Robert J. Dinger,
                    variables E T and h.    We find the preliminary             Wolfgang Keydel, Otto Kessler, James W. Mink,
                    results (Figs. 3-7) promising.                              Walter Flood, and Lloyd W. Root.

                    The effectiveness of our strategy depends                   We also wish to thank Drs. Charles Elachi,
                    sensitively on the sharpness of the relevant                Diane Evans, Jakob van Zyl of the CAL-TEC Jet
                    histogram peaks because such a           sharpness          Propulsion Laboratory, Pasadena, Ca., who made
                    reflects similarity      of    the       polarimetric       available the JPL/CV-990 L-band poL-SAR data
                    scattering behaviour of all the pixels within               sets of the San Francisco Bay area used in
                    a given class.         Therefore, other      image          this paper.
                    processing    techniques,     when       used    in

                                                                         458

                                        REFERENCES

                   (1)    J.C. Dainty, (ed.), Laser Speckle and
                          Related Phenomena,      Topics in Applied
                          Physics,     Vol.9,     Springer       Verlag,
                          Heidelberg, 1975.

                   (2)    A.B. Kostinski and      W-M. Boerner, "On
                          foundations of radar    polarimetry," IEEE
                          Trans.    Antennas     Propag.     AP-34(12),
                          1395-1404 (1986); H. Mieras, "Comment,"
                          IEEE Trans. Antennas Propag. AP-34(12),
                          1470-1471 (1986); A.B. Kostinski           and
                          W-M. Boerner,       "Reply," IEEE       Trans.
                          Antennas Propag. AP-34, (12) 1471-1473,
                          Dec. 1986

                   (3)    R.M.A.    Azzam.      and  N.M.       Bashara,
                          Ellipsometry      and   Polarized       Light,
                          North-Holland, Amsterdam, 1977.

                   (4)    E. Merzbacher, Quantum Mechanics, John
                          Wiley, 1961, Ch. 13.                                                               (a)
                   (5)    A.B. Kostinski and W-M. Boerner, "on the
                          polarimetric     contrast      optimization,"
                          IEEE Trans. Antennas Propag. AP-35, No.
                          8, 988-991, Aug. 1987.

                   (6)    H.A. Zebker, J.J       van Zyl, and D.N.
                          Held, "Imaging r@dar polarimetry -from
                          wave synthesis," J. Geophys. Res. 9,(Bl),
                                                                                                                                  -7
                          683-701, 1987.

                   (7)    N. Donovan, D. Evans, and D.     Held (eds),
                          NASA/JPL Aircraft SAR Workshop Proc.
                          (JPL, Pasadena, CA, Feb.           4-5,1985),
                          iPL-publ. 85-39, Jan. 15, 1985.
                                                                                                                                -.7
                   (8)      W-M. Boerner, Polarization microwave
                          Holography: An Extension of Scalar to
                          Vector    Holography     (invited),       1980
                          International         Optics        Computing
                          Conference, SPIE's Techn. Symp. East,
                          Washington, DC, April 9, 1980, Session
                          3B, Paper no. 231-23, Proceedings, pp.
                          188-198, 1980.
                   (9)    G. Strang, Linear        Algebra and       Its                                    (b)
                          Applications, Academic Press, New York,
                          1976. Academic Press, New York, 1982.
                                                                                    Fig. 2. Synthesized    Images: (a) HH Element of
                                                                                    (S] and (b) Span of    (S].
                                                                                    Speckle in these.coherent images is due to
                                                                                    random phase modulation associated with
                                                                                    surface roughness. The span image (b) has
                                                                                    less speckle than the HH image (a) because
                                                                                    span [S] = IS  HH12  + Is HVI2 + ISVHI 2 +  IS,12
                                                                                    is an incoherent average of four images.
                                                                                    Sixteen uniformly spaced gray scale levels
                                                                                    have been used to cover the voltage values in
                                                                                                   -3.5    -1.5
                                                                                    the range [10         10    1 on a logarithmic
                                                                                    scale.

                    Fig. 1. Arrangement of      Coordinate System for
                    Polarimetric SAR.

                                                                           459

                                                              17
                                                J

                                                                                                        '1@71

                                                                                                      (b)

                 Fig. 3. Histogram of optimal Transmitted Polarizations: (a) ocean Region and (b) Urban Region.
                 Optimal eigenvectots were computed for each pixel of the 200 x 200 ocean and urban regions (see
                 Step 1 of the PMF). These eigenvectors were histogrammed in ellipticity c and tilt T
                 coordinates (see Eq. [8]). Minimum energy eigenvectors were found for ocean pixels and maximum
                 for urban pixels. The mode (peak of histogram) location indicates that at E       T Of  c = 0* and -r
                 900 (vertically polarized), a majority of ocean pixels will respond weakly. Fortunately, the
                 modes of (a) and (b) are the same and, therefore, the majority of city pixels will respond
                 strongly to the same polarization.

                                       (a)                                                             (b)

                  Fig. 4. Histogram of Scattered Polarizations: (a) Ocean Region and (b) urban Region.
                  The scattered field E  R was computed for each pixel of the 200 x 200 ocean and urban regions;
                  the transmitted polarization was chosen in accord with Fig. 3. These scattered Polarizations
                  were histogrammed in ellipticity c and tilt T coordinates (see Step 2 of the PMF). The ocean
                  mode at e = 00 and T = 900 indicates that a majority of ocean pixels are mismatched by
                  adjusting h to e = 00 and t = 00. Because the two modes coincide, an appreciable portion of
                  the urban region will also be mismatched. However, the large spread of the urban histogram
                  still leads to significant contrast improvement.

                                                                        460

                                                                                                                                                                                                                      J

                                                                                                                                                                                                                      A

                                                                                                                                                                                                                      44

                                                                                                                                                                                                               '-  flo

                                                                             (a)                                                                                                                     (b)

                               Fig. 5. Synthesized Images: (a) ocean Polarization mismatched and (b) ocean Polarization
                               Matched.
                               In (a), the ocean was mismatched by adjusting                                                   ET to        the peak of Fig. 3a (C                               01, T = 90*) and
                               by adjusting h orthogonal to the peak of Fig. 4a (c =0*, T = 00). In (b), the ocean was
                               matched by adjusting                       ET    as before, while adjusting h to the peak of Fig. 4a (c = 0", T = 901).
                               Note that the ocean vs. urban contrast is much higher in (a) than in (b). Sixteen uniformly
                               spaced gray scale levels have been used to cover the voltage values in the range
                               [10-3-5,10-1.5               ] on a logarithmic scale.

                                                                                                                                                                                           I SELECT REGION I
                                                                                                                                                                                           I (OCEANIURBAN) I
                                                               CITY
                                                                                                                                                                                                            01
                                                                                                                                                                                  FC-ONSTRUCT POWER MATRIX I

                                       VOLTA IGE BRIG4HTNESSILOGI                          VOLTAIGE 51IG4HTNES5 -2 (LOG)
                                                                                                        (b)                                                                       I OPT-IMIZE ENERGY DEN,1ITY
                                                                                                                                                                                       (MAX OCEANIMIN V               W AN

                                                                                                                                                                                                            ."". - T,-.
                                                                                                                                                                               I  HIS                     IDENTIFY MODE

                                                                                                                                                                                  I COMPUTE-SCATYERED FIELD

                                                                                                                                                                               r-HISTOGR-AM &             IDENTIFY"
                                             .6     .4      .1                         -6       4       -4     .3
                                      VOLTAGE BRIGHTNESS (LOG)                            VOLTAGE $RIGHTNESS (LOG)
                                                    W                                                   (d)                                                                                           ADJUST RECEIVER
                                                                                                                                                                            E@M.S.ATCH OCL NIMAICH URBAN)
                               Fig. 6. Effect                  of    PMF on         Image Brightness
                               Distributions:                  (a) HH Reference, (b) optimal
                               Reflected Energy (see Step 1 of the PMF), (c)                                                                                                               I-fFFR- 0 D U C EIMAGE
                               ocean Matched, and (d) ocean Mismatched (see
                               Step 3 of the PMF).
                               All voltage values are normalized by the                                                                                    Fig. 7. PMF Flow Chart                           with Applications to
                               transmitted energy and, therefore, their                                                                                   Ocean vs. Urban Contrast Enhancement.
                               logarithms are negative. The decrease in
                               relative overlap area between (a) and (d)
                               indicates contrast enhancement. Also, note
                               that the decrease in variance of the ocean
                               distribution between (a) and (d) signifies
                               speckle reduction.
                                                               C
                                    L -1

                                                                                                                                       461

                              REMOTE SENSING OF PHYSICAL AND BIOLOGICAL PROPERTIES OF ESTUARIES

                                              Charles Bostater, Vic Klemas

                                  University of Delaware, College of Marine Studies
                                                 Newark, Delaware 19716

                                ABSTRACT

                 Estuarine remote sensing instruments               In general, we can safely say that
                 are described with respect to state           interestuarine comparisons have and will
                 of the art capabilities.        Remote        probably continue to rely upon spatial
                 sensing studies of estuaries can be           and temporal resolution less than that
                 considered as being of two different          required for intraestuarine comparisons.
                 types:   estuarine intercomparisons           For, example,, current       inter estuary
                 (between     estuaries)  and    intra-        comparisons    have   relied    upon AVHRR
                 estuarine (within estuary assess-             satellite data with a spatial resolution
                 ments).       Current   research has          of   greater, than      a  kilometer. The
                 allowed initial efforts of estuarine          frequency of satellite overpasses used in
                 intercomparisons    of light atten-           such analyses are based upon daily to
                 uation    and   suspended sediments.          monthly temporal frequency. For example,
                 Remote sensing can provide inputs to          figure 2 shows the results of comparing
                 math- ematical      models   used for         14 different coastal estuarine and near
                 research and management of estuaries          coastal water areas after 17 images were
                 and near coastal waters.        The in        atmospherically    corrected using NOAA,
                 situ optical profiling approach is            NESDIS atmospheric corrections according
                 transferable    to   other estuarine          to Stumpf (1,2).      Approximately 85% of
                 studies.                                      the varibility     of    light attenuation
                                                               estimated     from    these    images    was
                                                               statistically associated with physical
                                                               characterisitcs of the estuaries (i.e.
                                                               water    depth,     freshwater     velocity,
                                                               average wind speed, amplitude of the
                                                               tidal current, a scale for the tidally
                                                               rectified    residual    circulation,    and
                   1.       INTRODUCTION                       bottom sedimnet type).

                   Remote sensing of    estuaries can be
              conceptualized as being applied to two
              types    of     analysis   questions,    as             Intraestuarine    comparisons     rely
              indicated in figure 1.           These are       upon, and     generally    require,   remote
              interestuarine (between estuaries) and           sensing    data   with    higher    spatial,
              intraestuarine     (within    an   estuary)      temporal,     radiometric     and    spectal
              comparisons.       At a national level,          resolutions in order to resolve dynamic
              government agencies are interested in            processes occurring on smaller space and
              comparisons between estuaries in order to        time �cales. Low flying aircraft sensors
              help provide      information   for making       have an important role in both types of
              regional or national policy decisions.           analysis efforts.
              The information requirements for these
              types of    comparisons is unique from
              assessments    concerning   a    particular         2. REMOTE SENSING INSTRUMENTATION
              estuary, subestuary drainage area, water
              segment, or water mass boundary such as a        Existing satellite sensor systems aboard
              front between water masses with different        SPOT and      Landsat  mss (multispectral
              optical signatures.                              scanner) or TH (thematic mapper) systems
                                                               can provide the spatial resolutions for

                                            CH2585-8/88/0000- 462 $1 @1988 IEEE

                                         Estuarine Intracomparisons
                                                              I                                       Liuing Resources/
                                 Land Estuarine Tributary Estuary Water                            P Biological Production
                                 Use Habitats Outputs                   Plumes Quality                      Assessments
                                                                             Estuarine
                                                                        Intercomparisons

                                 Figure 1.           Conceptualization of estuarine and interestuarine
                                 comparisons.

               estuarine intracomparisons, but they lack                                At the same time, data from remote
               the      temporal       resolution       needed for               sensing       instruments          is    becoming        a
               studies that          rely      upon     a temporal               valuable asset in filling temporal and
               frequency of less than 2 weeks. Even                              spatial data gaps used in the application
               this estimate is optimal                since cloud               of      research      and      natural        resources
               cover     typical          prevents      use       these          management models.             Figure 3 indicates
               satellite images more than              2-3 times a               the     different        types of mathematical
               season.       The AVHRR sensor onboard the                        models and types of inputs that remote
               Tiros N series              of NOAA satellites                    sensing       instrumentation can currently
               provides the one or two times a day                               provide for estuarine and near coastal
               coverage needed for studying the dynamics                         ocean assessmnets.              Past research has
               of estuaries. Except for extremely large                          documented the capability of providing
               estuaries and near coastal waters, this                           land use from remote sensing satellite
               instrument        lacks     the      footprint         or         platforms.         The technology exists for
               spatial resolution            as     well      as the             determination of salinity using microwave
               spectral          resolution       necessary         for          radiometry as described by Swift (3).
               detailed          estuarine       intracomparisons.               At     this       time,      sea    surface        water
               This     instrument        lacks      the spectral                temperature is one of the few remote
               resolution (only 2 visible channels) in                           sensing       variables routinely processed
               the       visible           portion         of       the          from AVHHR imagery.             Recent research by
               electromagnetic spectrum that would allow                         Stumpf            (1,2)         and           estuarine
               application of sophisticated multichannel                         intercomparisons by Bostater et. al. (4)
               inverse algorithms.                                               have documented the advances and possible
                                                                                 routine       use     of     AVHRR       imagery for
                                                                                 suspended sediment (seston) and light
                                                                                 attenuation estimation in estuarine and
                                                                                 near coastal waters.               Hardisky, Klemas
                                   ro 3@ M 0@ M     a 0  N W -N O@ -4            and Daiber (5) have shown the ability to
                        CAPE COD                                  ...            estimate        wetland      biomass and stress
               LONG ISLAND SOUND                                                 detection which can be of value                      for
                        RARITAN  >             0                                 permit      activities         within       state    and
                        DELAWARE                                                 federal programs.              Remote sensing of
                   u.CHESAPEAXE                                                  SAV's (submerged aquatic vegetation)                 has
                   M.CHESAPEAXE                                                  also been described by                  Ackleson     and
                   L.CHESAPEAKE                           CD                     Klemas (6).             Table 1 indicates            the
                   T.CHESAPEAKE                                                  performance-        of     remote      sensing       for
                                                                                 estuarine studies. This table summarizes
                        POTOMAC                                                  the     results       of     a     conference        (7)
                   RAPPAHANNOCK                                                  concerning remote sensing of estuaries
                           JAMES                         T                       and represents a general consensus on the
               ALBEMARLE SOUND                           01                      state of the art with respect to sensors
                   PAHL ICO SOUND                                                for     coastal         ocean       and       estuarine
                           MEUSE                                                 applications.

                                    1985 IMAGES        1.984 IMAGES

                                                                                 3. DELAWARE BAY REMOTE SENSING
               Figure         2.           Dimensionless           light             RESEARCH-OPTICAL MODEL INVERSIONS
               attenuation       (k/k max) for 14 estuarine
               and      near     coastal       water bodies for                        Ongoing research in Delaware Bay is
               selected images during spring 1984, 1985                          designed to provide the first estuarine
               along the Middle Atlantic coast of the                            and near coastal waters data base for
               US.                                                               optical characteristics of Case II and

                                                                          463

                                           aters            Hydrod9nmaic                 ate u I it9
                                           Node I  Runoff      Models istribution            81    onstituen

                                           Land Use            Tidal
                                           Vegatation          circulation                    Living Resources
                                           Cover               Local Currents                       Models
                                           Sail                                                            in"ct On Living
                                           Properties          Fronts'plumes                                arine Resources
                                           IEtc.               Surface Salinity          Suspended  Sed.
                                                               Surface Wate
                                                               Temperature               -Chlorophyll     Habitat Quality
                                                               wind Fields               -Pollution       Uariables
                                                               tc.                       Plumes           Wetlands And      t9
                                                                                         Dredging         Marsh Pmductiui
                                                                                         Water Temp.      H9droacousticStoc]k
                                                                                         Etc.             Assessments
                                                                                                          SAV's
                                                                                                          Fixed Platform
                                                                                                          Remote Sensing
                                                                                                          From Bridges
                                                                                                          Etc.

                                   Figure 3.'       Description of estuarine models and Model inputs that
                                   can be derived from remote sensing techniques.

                                                                                   measurements of reflectance or upwelled
                                                                                   radiance from below the water surface.
                    Case 111 (8) waters and associated water                              These models are then inverted in
                    quality indicator variables.                                   order to estimate state variables which
                                                                                   can be used for mapping purposes or for
                           During the last 2 years          a series of            inputs for estuarine and near coastal
                    estuarine,         near     coastal        water     and       water modeling efforts, as indicated in
                    continental shelf             cruises      have been           figure 5.
                    conducted.         During these cruises '(Which
                    are scheduled to coincide               'with optimal                 Thus, remote sensing provides the
                    satellite overpass conditions) in situ                         background for           assessments and atlas
                    high resolution optical profiles have                          .(maps)        information       for     considering
                    been conducted along with water chemistry                      impacts on          living      marine resources.
                    and algal primary productivity.                      The       Figure 6 shows the conceptual approach
                    optical       data     collection          (profiling)         used in the current and proposed research
                    scheme is outlined in figure 4.            '' optical          for      estimating       state variables from
                    spectra (400-1100 nm) are calculated from                      remote sensing instrumentation.
                    downwelling (Ed)           and     upwelling (Eu)
                    measurements above and 'below.the water
                    surface.                                                              Edo -1,      t EUG
                           This in situ data              provides the
                    necessary          optical         spectrums         for         Z=O                      Air Water Interface
                    calculation of light attenuation (k),                                   Edz,,,
                    backscatter            (b)        and      irradiance            z=JL
                    reflectance      (R)   spectra, which can then                                     'rEuz
                    be related to          water concentrations such                 z=2                                  Ez=Eoe
                    as chlorophyll, suspended sediment or                            z=3
                    tracers'of freshwater (such as gelbstoff)                                          t
                    into near coastal waters for estuarine                                                                     Edo
                    ,fronts and plume detection.                                     z=4               t                  2k=ku+kd
                           These       measurements            allow     Ithe        z=i               t                  ku=kd
                    development and testing of              new improved                                                    B=Rd2k
                    optical models based upon               a variety of             B=bw+bjLC IL+B2C2+B iC i
                    solutions and          approximations         to the             1k=kw+kjC1+k2C2+kiCi
                    radiative transfer problem. As indicated
                    in figure 4, the goal of this basic
                    research is to provide the algorithms for
                    relating water properties to aircraft,                         Figure 4.        Delaware Bay in situ light
                    shipboard, in situ or satellite sensor                         measurements and analysis framework.

                                                                             464

                                 Develop Improved Optical Models.
                                For Organic/Inorganic Constituent
                             Mapping Using Optical/Biological/Chemical
                                          Shipboard Data

                            Analysis of AVHRR,MSS,TM
                           Time Series and Ship Data           Use Satellite Data To Map
                             to Determine Spatial &          Organic/Inorganic Const   ' ituents
                             Temporal Variability of          By Inverting Algorithms And
                         Ph9sical/Biological Properties Performing Atmos. Corrections
                                of Delaware Ba4

                                         Determine State   Variables Of Estuaries
                                           By Remote Sensin To Estimate Their
                                                           E Yq
                                       Susceptibility To     v irommental Degradation
                                       And Changes In Living Resources Production
                                     Delaware,Chesapeake,Potamac,Albemarle,Pamlico
                                     ,Hudson/Haritan,Long Island,Mobile, Others

                        Figure 5.    Conceptualization and approach for optical model
                        development, data collection, and estimation of state variables
                        for estuarine comparisons.

               4. MULTILEVEL REMOTE SENSING
                                                                           5. SUMMARY
                 The above discussion has focused on               Estuarine    .remote   sensi.ng has a
            satellite sensors and       in   situ data       unique role to play in estuarine and near
            collection    efforts.      Remote sensing       coastal water research and management.
            instruments that need greater attention          This role has been and will continue to
            are sensor systems which canbe flown             become more useful as new instrumentation
            from low altitude aircraft.        To date,      can    be. applied,     and   tested     with
            NASA and NAVY research and development           concurrent in situ water column studies
            funding has been utilized to develop             and routine monitoring programs. Dynamic
            these type of systems for ocean color.           small scale features. and effects upon
                                                             living marine resources can        also be
                 These systems have been used to             assessed with new instrumentation that is
            assess the optimal bands for detection of        becoming available to marine scientists.
            water   column    constituents.       Recent
            advances in instruments such as charged
            couple device (CCD) multispectral video
            cameras or other similar detectors need                    6. REFERENCES
            to   be     given   multiuse     development
            considerations     by  agencies.       These     1. Stumpf,     R., Application of AVHRR
            instruments can provide the capability to        Satellite data to the study of sediment
            cover large scale areas in a short time          and chlorophyll in turbid coastal water,
            period (hours to minutes), as well as for        NOAA Technical Memorandum NESDIS AISC 7,
            studying    small   scale    processes    in     1987, 50 pp.
            estuaries.
                                                             2.   Stumpf,     R.,  Remote    sensing of
                                                             suspended sediments in estuaries using
                  In addition, such devices have the         atmospheric and'compositional corrections
            potential for serving as fixed platform          to AVHRR data, Proc. 21st Inter. Symp.
            optical    ground   truth    stations    for     Rem. Sens. of Env., Ann Arbor, M1, 1987,
            satellite sensor systems as well as for          18 pp.
            calibration purposes.    They can also*can
            be designed for use aboard ships as well         3.   Swift,    C.,   microwave radiometer
            as aircraft,     enabling remote sensing         measurements of Cape Cod canal, Radio
            techniques to be conducted under various         Science, Vol. 9, No. 7, 1974, pp. 641-
            sky and cloud conditions.                        653.

                                                         465

                                                Veg.& Biomass Coast- Bottom                Susp. Susp.     Chloro-                       Curr
                                            Plat- Land & Veg.     line    Feat. Depth      Sed.   Sed.     phyll     Oil   Surf. Water   Circ:   Wave    Surf.
                          Sensor            form  Use  Stress Erosion SAV        Profiles  Ptrns. Concen.  Concen. Slicks Temp. Sal.     Ptrns. Spectra Winds

                          Film Cameras      A       3       1         3     3        2         2       1       1       2       0     0      2        2       1
                                            S       2       1         2     2        1         2       1       1       1       0     0      2        2       1

                          Multispectral     A       3       2+        3     3        2         3       2       2+      3       0     0      2        2       1
                          Scanners          S       2       2         2     2        2         3       2       2       2       0     0      2        2       1

                          Thermal IR        A       1       1         1     0        0         1       0       0       3       3     1      2        0       1
                          Scanners          S       0       0         0     0        0         1       0       0       1       3     0      2        0       1

                          Laser             A       0       0         1     3        3         1       0       0       1       0     0      0        3       1
                          Profilers         S       0       0         1     1        1         0       0       0       0       0     0      0        2       0

                          Laser             A       11      0         1     0        1         1       2       3       3       1     1      1        0       0
                          Fluorosensors     S       0       0         0     0        0         0       1       1       1       0     0      0        0       0

                          Microwave         A       1       0         1     0        0         1       1       1       3       3     2      2        1       3
                          Radiometers       S       0       0         0     0        0         0       0       0       1       2     1      1        0       2

                          Imaging Radar     A       2       1         3     0        1         1       0       0       3       1     1      2        3       2
                          (SAR or SLAB)     S       1       0         2     0        1         0       0       0       2       0     0      1        2       1

                          :CODAR (Radar)    G       0       0         0     0        0         0       0       0       0       0     1      3        2       2

                          RADS(Acoustic)    Q       0       0         2     3        2         2       1       0       1       0     0      2        1       0

                          UW Camera         G       0       0         2     3        2         2       1       1       1       0     0      1        0       0

                          Rating                                                                  Platform
                          3 - Reliable (Operational)                                              A - Aircraft   (Medium or Low Altitude)
                          2 - Needs Additional Field    Testing                                   S - Spacecraft (Satellite)
                          1 - Limited Value (Future Potential)                                    G -  Ground (Boat,or Field)
                          0 - Not Applicable

                                              Table 1.         Estuarine remote sensing instrument capability - state
                                              of the art consenus (7).

                     4. Bostater, C., et.al., Remote sensing                                     7. Klemas, V., Thomas, J. P., Zaitzeff,
                     of       suspended             sediment          and        light           J. B., eds, Remote Sensing of Estuaries,
                     attenuation            for        estuarine         and near                US GPO, 1987 0-181-100(72341), 1987, 250
                     coastal waters - CASE III water types,                                      PP.
                     (submitted for publication), Aug. 1988,
                     23 pp.                                                                      S. BUkata, R. P., Jerome, J. H., Bruton,
                                                                                                 J. E., Particulate concnetrations in Lake
                     5. Hardisky, M. A., Klemas, V., and                                         St. Clair as recorded by a shipborne
                     Daiber, F. C., Remote sensing salt marsh                                    multispectral optical monitoring system,
                     biomass          and      stress         detection,            In:          Remote Sens. Env., 1988, pp. 201-229.
                     Advances in space research,                          Vol. 2.
                     COSPAR, Pergamon Press, London, 1983, pp.
                     219-229.

                     6. Ackleson, S. G., Klemas, V., Satellite.
                     remote         sensing         of submerged aquatic
                     vegetation in lower Chesapeake Bay, In:
                     Remote Sensing of Estuaries, US GPO 1987
                     0-181-100(72451), 1987, pp. 199-218.

                                                                                           466

                                                       RADAR DETECTION OF OCEANIC FRONTS

                                                                Donald L. Murphy

                                                            INTERNATIONAL ICE PATROL
                                                      Avery Point, Groton, CT 06340-6096

                                      ABSTRACT                               second is a description of a 1986 experiment in
                                                                             which SLAR images were compared with IR data and
             In recent experiments, the Ice Patrol compared                  in     situ   measurements.      Data     from   a    third
             radar images of the ocean with satellite infrared               experiment, conducted in 1987, are still being
             imagery, and hydrographic and drifting buoy data                analyzed and the results will be reported later.
             collected at the sea surface.             The radar, a
             side-looking airborne radar (SLAR), is a real                                           BACKGROUND
             aperture radar that operates in the X-band.            The
             SLAR    can    detect    the    sharp   thermal      fronts     Since 1983, Ice Patrol has used SLAR as its
             associated with warm     eddies. However, the results           primary instrument for iceberg reconnaissance.
             of the experiments       show that interpreting SLAR            During the iceberg season, typically March through
             images    in the absence of supporting data is                  August,      IIP  flys    approximately      80    iceberg
             difficult.     This instrument is most useful when              reconnaissance patrols.        Each flight is about
             used in conjunction with other data sources, such               3200km in length and covers 65,000 sq. km, a small
             as drifting buoys and AXBT's.                                   portion of the Ice Patrol operations area.

                                                                             The SLAR is a Motorola AN/APS-135, an X-band (3cm
                                                                             wavelength), real aperture radar that scans the
                                    INTRODUCTION                             sea surface in a plane normal to the flight path.
                                                                             The radar image from both sides of the aircraft is
             Since its formation in 1914, the International Ice              displayed on a CRT that produces a continuous
             Patrol (IIP) has tracked icebergs in the North                  negative image on photographic film.           The radar
             Atlantic,    warning mariners of the danger to                  data are not recorded digitally.             Navigational
             navigation.    Circulation in IIP's operations area             information      from     the     aircraft's     inertial
             (40*N to 52*N, 39*W to 57*W), which is east and                 navigation system is printed directly on the
             south of Newfoundland, Canada, is dominated by two              film.    The SLAR system polarization is         vertical
             major      currents.        The     first      'is     the      (VV) and is   not selectable.
             southward-f lowing, cold and relatively fresh (<
             2*C and < 34.3 ppt) Labrador Current            (LC);  the      The U. S. Coast Guard has two SLAR systems
             second is the northeastward-f lowing, warm and more             installed     on   its   long-range    patrol    aircraft
             saline (> 12*C and > 35.5 ppt) North Atlantic                   (HC-130).     During the iceberg season one of the
             Current (MAC).                                                  HC-1301s is deployed to Newfoundland on alternate
                                                                             weeks.
             A knowledge of the boundaries and areal extent of
             the LC and MAC, and their associated eddies is                  Routine IIP patrols are flown at an altitude of
             useful in predicting iceberg movement, a major Ice              8000 ft (2438m), which permits the radar to map a
             Patrol task.     Satellite infrared (IR) imagery of             lOOkm-wide swath of the sea surface, 50km on each
             the ocean's surface has been used with great                    side of the aircraft.         This is the same swath
             success in many parts of the world's oceans to map              width as the operational mode planned for RADARSAT
             thermal gradients and, thus, infer circulation.                 and approximately the same resolution ( 30m).
             However, persistent clouds and fog in the IIP                   RADARSAT's scan mode permits coverage of a 500km
             region restrict the use of IR detection of oceanic              swath with a 100m resolution.
             features to a few images per month, which is of
             limited use for operations.            Active microwave         Airborne     and   satellite    imaging    radars     have
             systems (radars), which also have the ability to                demonstrated the ability to detect the surface
             map oceanic features (1), can penetrate clouds and              manifestations of oceanic fronts associated with
             fog, making them an attractive alternative to the               eddies and the Gulf Stream, and internal waves.
             IR sensors.                                                     Several investigations (2, 3, and 4) documented
                                                                             the ability of the SEASAT synthetic aperture radar
             Two examples are presented.           The first is a            (SAR) to detect such features.           LaVoilette (5)
             comparison between a SLAR-observed front on 28                  compared imagery from the SEASAT SAR, with imagery
             April 1985 and IR imagery of 26 April 1985. The                 from an earlier, less powerful version of the IIP

                                                      CH2585-8188/Oooo- 467    $.1 @1988 IEEE

                   SLAR, and satellite IR imagery.           The results of          Oceanic f rOnts .    The detection of the f ront was
                   the experiment, which was conducted in the UP                     unimpeded' by the clouds and fog.            However, the
                   operations area, showed that both radars could                    SLAR image does not give quantitative information
                   detect the fronts seen in the IR images.                          about the thermal gradient ..on the sea surface.
                                                                                     What was lacking was a surface measurement program
                   Imaging radars map         the   sea-surface      roughness       to document the meteorological conditions, water
                   through Brags scattering (1), which for the 3-cm.                 mass characteristics, and current information. An
                   wavelength and incidence angles of the           UP SLAR,         Ice Patrol SLAR experiment in 1986 addressed these
                   results    in    a    sensitivity     to    ocean      waves      needs.
                   approximately 2-cm long.         As a result, the UP
                   SLAR imagery of the ocean is essentially a map of                                         April 1986
                   the distribution of these 2 em-long waves; the
                   SEASAT SAR was sensitive to 30-cm, wavelengths                    in April and   May 1986 Ice Patrol conducted a study
                   (6).    on both radars, differences in surface                    east of the    Grand Banks of Newfoundland in which
                   roughness are indicated on the radar image as                     SLAR images   of the sea surface were compared with
                   tonal changes.      Thus, there are light and dark                in    situ     hydrographic     data,     drifting      buoy
                   areas on the images that correspond to differences,               trajectories, and an AVHRR image (8).           The study
                   in the reflected radar energy.                                    focused on a warm-core eddy spawned from and
                                                                                     interacting with the NAC, which is an extension of
                   Interpretation       of   the    images     requires      an      the Gulf Stream (east of about 50*W).
                   understanding     of    how    wind     stress,     current
                   gradients, temperature, salinity, etc. modulate                   Four    aerial    SLAR    surveys,     at    approximately
                   capillary and short gravity waves on the ocean                    one-week intervals, provided radar images of the
                   surface; but, our understanding is poor. Lichy 2jt                sea surface in the study area.          The first survey
                   al (7), who tracked a warm core ring using SEASAT                 (26   April    1986)     covered   127,000    sq km and
                   SAR data, found that within the warm water there                  identified a site to conduct the hydrographic
                   was a more intense radar return than from the                     study.   The three subsequent flights (2, 9, and 17
                   surrounding area.     But much additional research is             May 1986) focused on the hydrographic study area,
                   required before radar images can be interpreted                   each mapping 56,000          sq km with overlapping
                   with confidence.                                                  coverage.

                                           April 1985                                on the last day of the experiment the AVHRR on
                                                                                     NO&A 9 provided the only useable T.R. image of the
                   The first example is a comparison             between the         area.
                   SLAR-observed north wall of the Gulf Stream and
                   satellite infrared (IR) data,            as analyzed by           A photo mosaic of the 26 April       SLAR survey (Figure
                   NOAA's National Environmental Satellite and Data                  3) shows what we interpret as the WAC, appearing
                   Information System (NESDIS).                                      as a dark region along the southern and eastern
                                                                                     edge of the image.       Over most of the image, the
                   Figure I shows a simplified reproduction of NOAA                  boundary between light and dark areas is sharply
                   interpretation of a Advanced Very High Resolution                 defined.    However, its shape is complex and not
                   Radiometry (AVHRR) image south of Newfoundland,                   easily explained. The area enclosed by the white
                   Canada.   The analysis, a composit based on images.               box was the site of a 68 station bydrographic (26
                   taken on 25-26 April 1985, shows a warm-core eddy                 April - 3 May 1986) survey; during which CTD
                   interacting with the Gulf Stream in the vicinity                  (conductivity, temperature, and depth) casts to
                   of 41*H, 50*W. The inset shows the interpreter's                  about 1000 m were taken along ten north/south
                   worksheet on which is marked the location of the                  transects.
                   Gulf Stream's north wall.
                                                                                     Figure 4 shows the distribution of sea surface
                   An Ice Patrol SLAR reconnaissance flight mapped a                 temperature, showing a sharp thermal front that is
                   portion of the region two days after the AVHRR                    nearly     coincident       with    the      SLAR-observed
                   image was taken.      on the date of this patrol (28              boundary.    As in the     previous example, the dark
                   April 1985) the sea surface was obscured by clouds                area indicates the presence of warm water.               The
                   and fog, preventing the collection of IR images.                  hydrographic      survey     Iidentified      the     water
                   The SLAR image (Figure 2) shows a sharp tonal                     properties as     those   of NAC origin       (T > 12*C,
                   boundary that is conincident with the IR-observed                 salinity > 35.5 ppt).          The combination of the
                   north wall at 50*W longitude.            Figure 3 is a            hy0rographic.      data      and      trajectories        of
                   negative image, thus the dark area is a region of                 satellite-tracked buoys showed that this feature
                   high radar return (i.e., radar bright). This area                 was a meander of the NAC that was developing into
                   of high radar return marks the warm Gulf Stream                   a warm-core eddy.        Henceforth, the feature is
                   waters.     This result is consistent with the                    referred to as an eddy, although determining
                   findings of Lichy et al.           (7), who tracked A             exactly when the feature developed a closed
                   warm-core   ring using SEASAT     SAR data, that within           circulation is not possible from the data.
                   warm water there was a more intense radar return
                   than from the surrounding area.                                   Following the evolution of the eddy over the
                                                                                     three -week period of observation was difficult for
                   The results of this simple comparison demonstrated                two reasons:      first, the inability of the SLAR
                   that the UP SLAR had some promise as an                           imagery to provide a closed boundary on all of the
                   instrument that could be used to detect major                     flights, and second, the complexitiy of an eddy

                                                                                468

              interacting with the NAC and trapped against the              definition.
              Grand Bank and the Labrador Current. The location
              of the northern and eastern boundaries of the eddy            The 1986 study illustrates the importance of
              was well def ined on both 26 April and 2 May SLAR             research that blends remote sensing with in-situ
              surveys; however,     in neither survey were the              sampling,   with the goal of studying oceanic
              western and southern   boundaries,well defined.               processes.   Without the SLAR we could not have
                                                                            located the   fronts as easily, nor recognized the
              The 9 May SLAR survey provided the most complex               spatial and   temporal variability of the system.
              and   ambiguous     images   of    the   study.      The      Without the   in-situ sampling, the imagery would
              northernmost    frontal   location    remained   nearly       have   been   another   opportunity    for    'unfounded
              unchanged.    However,. this survey provided the              speculation.
              first good image of the southern portion of the
              feature.                                                                            REFERENCES

              The 17 May SLAR survey, conducted on the last day             1. Robinson, I. S.,   1985. Satellite
              of the experiment, provided the most remarkable                     Oceanography:   An Introduction for
              image (Figure 5).     By this date trajectories of                  Oceanographers  and Remote-Sensinx
              sate 11 ite-tracked drifters had confirmed that the                 Scientists. West Sussex, England: Horwood
              feature    bad   the    characteristic     anticyclonic             Limited. 455pp.
              .(clockwise)  circulation of a warm-core eddy.       The
              SLAR image    shows an eddy with a complex shape              2. teal, R. C., P. S. DeLeonibus and I. Katz,
              interacting   with the NAC.       Along the southern                1981. Spaceborne Synthetic Aperture Radar
              boundary of   the eddy is a sawtooth-pattern with a                 for Oceanography. The John Hopkins
              peak-to-peak separation of 35km and a height of                     oceanographic studies, No. 10. The Johns
              20km.    As   on other     dates, not all of the                    Hopkins University Press, Baltimore, MD,
              boundaries are clearly     defined, particularly the                215pp.
              western boundary. As a     result, it is difficult to
              estimate the size of the eddy based solely on the             3. Fu, L. And B.   Holt, 1982. SEASAT Views Oceans
              StAR imagery; the best size estimate is 160 by 80                   and Sea Ice  with Synthetic Aperture Radar.
              km.                                                                 Publication  81-120, Jet Propulsion
                                                                                  Laboratory,  California institute of
              May  17 was the only cloud-free day during the                      Technology,  Pasadena, California, 200pp.
              three-week experiment.     An AVRRR image from the
              NOAA 9 satellite taken 8 hours before the SLAR                4. Hayes, R. M.,   1981. Detection of the Gulf
              image, shows an excellent agreement of the frontal                  Stream, in Spaceborne Synthetic Aperture
              boundaries (Figure 6).       In addition, the SLAR                  Radar for Oceanography. The Johns Hopkins
              boundaries are as sharp as those seen on the IR                     oceanographic Studies, ed. by R. C. Beal.
              imagery.                                                            The Johns Hopkins University Press,
                                    CONCLUSIONS                                   Baltimore, MD, p. 146-160.

              SLkR imagery is difficult to interpret but can be             5. LaVoilette, P. E., 1983. The Grand Banks
              used   with    other    data   to    gain    a   better             Experiment: A Satellite/Aircraft/Ship
              understanding of oceanic processes.       in addition,              Experiment   to Explore the Ability of
              because SLAR and SAR imagery portray similar                        Specialized  Radars to define Ocean Fronts.
              features, the more we learn about SLAR now, the                     Report 49.   Naval Ocean Research and
              better prepared we will be to interpret satellite                   Development  Activity, NSTL Station, MS
              and airborne SAR imagery when it becomes routinely                  39529, 12 .6 pp.
              available.
                                                                            6. Vesecky, J. F. and R. H. Stewart, 1982. The
              The use of aircraft-borne SLAR, and eventually                      observations of Ocean Surface Pheonomena
              satellite-borne     SAR,    in    determining      ocean            Using Imagery from the SEASAT Synthetic
              circulation near the Grand Banks holds great                        Aperture Radar: An Assessment. Journal of
              promise for improving IIP operations.           However,            Geophysical Research, 87(C5):3397-3420.
              the work in interpreting radar imagery of the
              ocean surface has only started.       Experiments such        7. Lichy,D. E., M. G. Hattie, and L. J. Mancini,
              as that described here mist be repeated several                     1981. Tracking of a Warm Core Eddy, in
              times with a broad range of oceanic features.                       Spaceborne Synthetic Aperture Radar for
              Ultimately, the combination of active microwave                     Oceanography. The Johns Hopkins oceano-
              imagery, air-deployed drifting buoys, and AXBT's                    graphic Studies, ed. by R. C. Beal. The
              will permit IIP to gather the required near                         Johns Hopkins University Press, Baltimore,
              real-time data.                                                     MD, p 171-182.

              IIP SLAR data suffer somewhat from the inability              8. Thayer, V. B. and D. L. Murphy, 1988. SLAR
              to record digital radar data aboard aircraft.                       observations of ocean Fronts East of the
              This is not important for the major features, such                  Grand Banks of Newfoundland. Proceedings,
              as the obvious tonal signal that marked the Gulf                    Ilth Annual Canadian Conference on Remote
              Stream in the first example and the eddy in the                     Sensing. Waterloo University, Waterloo,
              second.    However,    for   more   subtle     features,            Ontario, Canada (In Press).
              digital processing would have provided better

                                                                      469

                                     70'       G5*        so,       53'       50'       43,
                                                                                             so*

                                     GS - GL41 Stream
                                     WE - Warm-core
                                        E(d*dy

                                                                              r
                                            C

                                                                   GS - -   CS

                                                                                             40*

                                             Nr WALL

                   Figure 1.  Reproduced National Earth Satellite Service (NESDIS) product from April 26, 1985.
                   Inset  NESDIS worksheet from 25-26 April 1985.

                                                       422ON

                                       N

                                                   M,                                  490OW
                                                         42DON 4950V

                                                     >

                                               A
                                  @GS   GL
                                     WM
                                         41 SU
                                        1
                                          arm,=
                                        E

                                                                            CE

                  Figure 2., A segment of SLAR film from an Ice Patrol reconnaissance flight of  28 April 1985.
                  Warm Gulf Stream water appears dark.

                                                                470.

                             7-7@

                                      7

                                                                                                    ";t;@3
                                                               77@7-1@"'- ttzQ@11-t

                                                                                            z,K

                  Figure 3.  Photomosaic constructed from SLAR survey of 26 April 1986.     The area enclosed by the
                  black box is the area of the hydrographic survey.

                                     46 N

                                       +

                                                   0     0                0    0
                                     45.
                                                   0                                           13'
                                                                               0    0    0

                                              0          0                          0   0
                                     45 N                                                        13*
                                       +                 0          0     0

                                              0                            0
                                                                               0             leo-
                                    44.5 N                                           120
                                       +                   120

                                     44 N

                                             40 W             47 N             46 W            45 W
                                   @z

                  Figure 4. Sea surface (0.5-1.0m) temperature   distribution based on the first phase (27 April    3
                  May) hydrography.

                                                                  471

                               IGP
                                                         War
                                   2W
                                  P_-'?'                  - --''
                  451ON-
                                W-0

                           r--#, -d- e

                           )Ef PAV
                                         01

                                                                                       7

                 43*40'N-

                       4930 w                                                    47PS6 W                                                   45*30'W

                                          Figure 5. Photomosaic constructed from SLAR survey of 17 May 1986.

                       Figure 6. Infrared image from the Advanced High Resolution Radiometer on. board NOAA 9 on 17 May
                       1986

                                                                                  472

                               ADAPTING THE NSCAT DATA SYSTEM TO CHANGING REQUIREMENTS

                                            J.R. Benada, D.T. Cuddy, B.H. Jai

                                         Radar Science and Engineering Section
                                                Jet Propulsion Laboratory
                                           California Institute of Technology
                                            Pasadena, California ?110? USA

             ABSTRACT:    NSCAT is a spaceborne, 8-beam            process it to wind speed vectors, deliver
             scatterometer which will measure ocean                the processed data to the principal inves-
             backscatter. The backscatter measurements             tigators and archive the data.
             are processed on the ground to oceanic
             wind vectors.     Vector winds will be re-               2 MISSION & INSTRUMENT DESCRIPTION
             trieved over 90% of the ice free, global
             oceans every two days for a three year                2. 1 Mission
             mission.    The Data System is a non-real-            The nominal NSCAT 'mission will provide
             time ground based science data processing             wind speed measurements over 90% of the
             system. It ingests backscatter telemetry,             ice-free, global oceans every two days.
             processes it to wind vectors, archives and            The wind speed root-mean-square           (rms)
             distributes the wind vector data and other            accuracy is the greater of 2 m/s or 10%
             products. Brightness temperatures from an             from 3 - 30 m/s.     The wind-direction rm5
             on-board microwave radiometer are used for            accuracy is 20 degrees in the 'same wind
             estimating atmospheric water.        The pro-         speed  range.      The spatial      resolution
             ducts are delivered to a Science Team                 required is 50 km.       The instrument is
             composed   of   oceanographers,     meteorolo-        designed for a circular, polar, sun syn-
             gists, climatologists and other scien-                chronous orbit with a nominal altitude of
             tists.    This paper describes the Data               E330 km.
             System, particularly the changes to the
             baseline design in response to changes in             The satellite bus is unknown at this
             requirements. The new requirements are in             writing.    Originally, the scatterometer
             five areas: 1) telemetry data source, 2)              was to be one of the instruments on the
             data catalog, 3) hosting Instrument Opera-            Navy's NROSS satellite with a launch in
             tions, 4) definition of data granularity              1991.    However, the NROSS program was
             (revolutions) and 5) Science Team data                cancelled in 19B7.     The NSCAT project is
             needs. The Science Team requirements are:             in the process of investigating and evalu-
             a) need for new or revised products, b)               ating other options.
             need for different delivery volume and
             schedule and c) need for electronic com-              2.2 Instruments
             munication among team and with the pro-               The instruments of interest to the project
             ject.                                                 are the scatterometer, of course, and the
                                                                   Special Sensor Microwave/ Imager, SSM/I,
                                                                   both described below.

                            1 INTRODUCTION                         2.2.1 Scatterometer
                                                                   The scatterometer is an 14 GHz active
             NSCAT '(NASA Scat terometer) 1,2 is a space-          radar which measures the normalized ocean
             borne, active radar which measures the                radar   backscatter    cross-section      (go).
             surface backscatter of the earth oceans.              Eight tran5mit/receive fan beam antennas
             These measurements are used to calculate              illuminate the earth in three different
             surface wind vectors with a resolution of             directions on each side of the subsatel-
             50 kilometers. Wind vectors are retrieved             lite track.      The antenna illumination
             over most of the worlds open oceans every             pattern on the earth is shown in Figure 1.
             two days. From these winds, the Principal             Antennas 2 and 5 are actually dual anten-
             Investigators (PI's), including         oceano-       nas with different polarizations.          The
             graphers, meteorologists and climatolo-               other antennas are single polarization.
             gists,   will,   for examplex     study wind          In the 350 km inter-swath gap centered on
             forcing of ocean currents, detect meteoro-            the subsatellite track, a. data cannot be
             logical features, and perhaps predict the             used for wind retrieval.
             occurrence of an El NiPio.         This paper
             describes the ground-based Data System                The 8 antennas are individually fired in
             which will ingest instrument telemetry,               a set sequence which is completed in about

                                               CH2585-8/88/oooo-473 $1 @1988 IEEE

                4 seconds.   The return signal is received                  the satellite ephemeris calculation.
                before the next antenna fires.         The re-
                ceived signal for each antenna is proces-              (d)  Decommutation and DN-EU conversion -
                sed on board using range gating and dop-                    unraveling of spacecraft telemetry.
                pler filtering of the backscatter power to                  DN-EU conversion is the conversion of
                generate a set of 25 measurement areas on                   instrument Data Numbers into Engi-
                the ocean surface called Cr, cells.     Each a.             neering Units, e.g., from spacecraft
                cell has a spatial resolution of roughly                    counts to the value of received power
                25km x 25km.                                                in watts.

                As the instrument flies along, it measures             (e)  Nadir location - calculation of the
                the backscatter of a patch of ocean from                    nadir point from the satellite ephem-
                three different directions and two dif-                     eris.
                ferent polarizations.        These different
                measurements are necessary to estimate the             (f)  Cell location  'and geometry - calcula-
                wind direction and to improve the wind                      tion of the earth surface location
                speed estimate.                                             and shape of each a. cell in an anten-
                                                                            na beam illumination pattern.           The
                2.2.2 SSM/I                                                 cells are roughly in a line, running
                The Special Sensor Microwave/ Imager (SSM/-                 out from the nadir point.
                I) is the same instrument as is currently
                flying an DMSP-FB.     It is a passive, scan-          (g)  Flag land and ice - The instrument
                ning instrument which measures the inci-                    cannot be used to measure winds over
                dent radiation, on the SSM/I, at 19, 21,                    or near land or ice.      Each cr, cel 1 is
                35 GHz from roughly circular footprints                     flagged based on a fixed land map and
                along the scan. Each scan is an arc cent-                   a temporally varying ice map.
                ered on the nadir point and extending
                almost to the edges of the scatterometer               (h)  Flag excess atmospheric absorption
                swath.   The SSM/I scan includes data in                    The instrument cannot be used to
                the scatterometer inter-swath gap.           The            measure winds in areas of large at-
                instrument also has an 85 GHz channel                       mospheric absorption. This is usual-
                which NSCAT does not use.         The surface               ly due to large amounts of atmospher-
                brightness    temperatures,    Tb,   at    those            ic liquid water, namely clouds and
                frequencies can ,be calculated.       The Tb's              rain.    The SSM/I data is used for
                which are co-located with scatterometer                     setting flags. The SSM/I Tb foot-
                sigma-o measurements are used to calculate                  prints (usually more than 1) must be
                the atmospheric absorption due to water.                    co-located with one a. cell and the
                This is used to set an "excess absorption"                  flag determined.
                f lag in the data to indicate that the
                scatterometer measurement at that location             (i)  a. calculation - this is the normal-
                is seriously degraded.                                      ized radar backscatter, corrected for
                                                                            instrument and antenna effects. Rms
                3 DATA SYSTEM FUNCTIONS & ORIGINAL DESIGN                   errors are also calculated.

                The Data System has three basic functions              (j)  a. grouping - the a.'s are grouped
                which correspond to a partitioning among                    into ground-track based Wind Vector
                three subsystems: ingestion, processing,                    Cells (WVC's) in preparation for
                and archiving and distribution.                             vector wind retrieval. The WVC's are
                                                                            the cells of a 50kmx5Okm grid running
                3.1   Ingestion and Processing                              parallel to the ground track.            The
                                                                            grid extends slightly beyond the far-
                3.1.1   Function%                                           thest possible cross-track distance
                The following     are   the basic      functions            for a a. cell.
                necessary to ingest and process the scat-
                terometer data:                                        (k)  Vector wind "retrieval" - a calcula-
                                                                            tion based on an algorithm estimating
                (a)   Telemetry ingestion - read telemetry                  the wind speed and direction which
                      tape, check for errors, merge with                    would produce the observed collection
                      previous data and check for missing                   of U0, s in the WVC.       This normally
                      data.                                                 produces 2 to 4 solutions with a
                                                                            likelihood     calculated      for    each.
                (b)   UTC time convertsion - convert the                    These solutions generally have very
                      instrument timetag into UTC (Univer-                  similar wind speeds but widely dif-
                      sal Time Coordinated).                                ferent direction.     In fact, frequent-
                                                                            ly two solutions will have wind di-
                (c)   Cut into revs - A "rev" is one satel-                 rections about 180 degrees apart.
                      lite orbit . The revs are based on a
                      set of rev start times generated from            (1)  Vector selection - this step takes

                                                                    474

                   the solutions and probabilities for                 engineers.
                   the WYC from the wind retrieval and
                   selects   one   wind     speed-direction      (e)  Provide information exchange utility
                   solution.   The algorithm looks at the             - for communication among the PI's
                   neighboring cells     to help in      the          and between PI's and the Data System
                   selection.                                         staff.

              An additional processing step is the pro-          3.2.2 Original Design
              duction of a two day vector average global         The archive and distribution design as-
              wind map. The format and contents of this          sumed that the users, mainly the PI'sv
              map are under study at this time but it            would want to select their data interac-
              will not affect the rest of the functions          tively over dial-up or network connec-
              discussed here.                                    tions.    Having selected the data, the
                                                                 PI's would want it delivered electroni-
              It is important to notice the two differ-          cally or by mail (tape) as soon as pos-
              ent organizations of the data.        One is       sible, normally within one or two days.
              based on the antenna beam illumination             Basically, these are the services sup-
              pattern, or "beam". The other is based on          plied by the NASA Ocean Data System,
              the Wind Vector Cell or WVC.     The data is       NODS.   The plan was to use NODS software
              organized by "beam" up to "cro Grouping".          on a dedic'ated NSCAT computer and only
              From that point on, the data is organized          make slight modifications to accommodate
              by WVC.   This is shown in Table 1.                NSCAT project data.

              The SSM/I data is organized by scan. The                 4 NEW OR ALTERED REQUIREMENTS
              data are cut into revs but otherwise unal-
              tered.    The Tb footprint location and            During 1987, several new or changed re-
              geometry are included in the incoming              quirements came to light.     Some, such as
              data. Thus the data is sufficient for co-          items 4.1, 2 and 4, arose from design
              locating with a. cells and calculating the         considerations.    One, 4.3, came from the
              atmospheric absorption.                            project.   The rest, all of 4.5, came from
                                                                 the PI's. This was based on their better
              3.1.2 Original Design                              understanding of their own needs and of
              The original    ingestion   and    processing      the original Data System design.
              subsystem design included the following
              features which bear particularly on the            4.1 Data Source Uncertainty - Due to
              new requirements considered later:                 cancellation of NROSS, we were not able
                                                                 to define the format, data time span,
              (a)  Division of the functions between the         delivery frequency or transfer method for
                   ingestion and processing subsystems           telemetry data.     However, we could not
                   as shown in Table 1.                          hold up ingestion design.

              (b)  The original data level definitions           4.2 Data Catalog
                   shown in Tables 1 and 2A.                     A catalog functions as a bookkeeper for
                                                                 the data handled by a subsystem.         Each
              (c)  A "rev" was defined as starting at            Data System subsystem has its own catalog
                   the northward going equator crossing.         which keeps information about all        the
                                                                 data types it handles. For example,      the
              (d)  The Data System provided no SSM/I             ingestion subsystem catalog contains     the
                   data to the PI's.                             information about external       inputs  and
                                                                 level 1.0 data.     The relevant parts of
              3.2  Archive and Distribution                      this must be transmitted to the proces-
                                                                 sing subsystem for it to know what data
              3.2.1 Functions                                    is ready to be processed.
              The following are the basic    functions of
              the data archive and distribution:                 Originally, the communication among these
                                                                 three subsystems was to be done once per
              (a)  Archive all project data - all data           day covering the last 24 hours.    This was
                   necessary to reproduce the data prod-         due to the subsystems' heterogeneous com-
                   ucts.                                         puter   environment   and   DBMS   software.
                                                                 Thus, the information is up-to-date only
              (b)  Deliver data to permanent archive -           when the information file is transferred.
                   i.e. NASA Ocean Data System.
                                                                 4.3 Host Instrument Operations
              (c)  Receive orders from PI's     which data       The project identified a need for a JPL
                   set was needed and for which time             based   Instrument   Operations    facility.
                   interval.                                     This is a non-real-time function which
                                                                 will monitor instrument performance and
              (d)  Distribute data to PI's    and project        trends.   It will also generate parameters

                                                            475

               to be loaded on the on-board processor.                 from SSM/I data for comparison with
               The real-time monitoring and communication              NSCAT winds and for estimating wind
               with the satellite and instrument will be               in the inter-swath gap.
               at the project or spacecraft operations
               control center.    The project wanted this         4.5.2    Different delivery volume and
               activity on the Data System as it would be         schedule
               the only local, NSCAT-dedicated computer
               facility operational during the mission.           (a)  The capability to provide routine
                                                                       delivery of    large data sets pre-
               4.4 Data Granularity                                    scribed in advance. Monthly delivery
               Overlapping of revs necessary to retrieve               would be satisfactory.
               winds greatly complicates processing,
               reprocessing and cataloging. The revs are          (b)  Retain the ability to request data
               defined based on the nadir location but                 many months old, but with a frequency
               the NSCAT instrument "looks" forward and                and volume expected to be small.
               backward of the nadir point by hundreds of
               kilometers (with respect to the direction          (c)  No need existed for an on-line re-
               of flight).     Likewise the SSM/I scans                quest or capability to provide selec-
               always aft of the nadir point. Thus, with               ted subsets of data quickly.
               revs beginning at the equator, a rev of
               Level 2.0 data (WVC data) contains data            4.5.3   A need remained for an electronic
               from three different revs of Level 1.5             communication between P.I.'s and with the
               (beam data) and two different SSM/I revs.          project for information and mail.

               4.5 Science Team Requirements                                      5 REDESIGN

               4.5.1  New or revised data products                The following are the changes made in the
               The PI's wanted some changes in the data           Data System in -response to the require-
               type to be delivered to them.     These were       ments given above.
               suggested by advisory committees and were
               discussed with the project in terms of             5.1 Ingestion Redesign
               practicality.                                      5.1.1 Isolation of external interface
                                                                  Because we knew the basic content of the
               (a)  Some PI's wanted to retrieve winds            incoming data, we defined an intermediate
                    from the calculated u.'s. These ex-           level which we could specify completely.
                    isted in Level 1.5.       However, the        The: ingestion subsystem could now be
                    large size of this file (over 500             designed from that point on.           Later,
                    MB/day) made this impractical. Also,          after the external interface was speci-
                    Level  1.5 is organized by antenna            fied, a conversion module would be writ-
                    "beam" and uD's must be grouped into          ten to convert from the true input to the
                    WVC's   for wind    vector    retrieval.      intermediate level.
                    Thus,  a smaller volume product ar-
                    ranged in WVC's was needed.                   5.1.2 Redefinition of Level 1.0
                                                                  Decommutation and DN-EU conversion at JPL
               (b)  The wind vector product that was to           are traditionally part of the data inges-
                    be delivered, Level 2.5. contained            tion process.   Those functions were added
                    only   the selected    wind    direction      to the ingestion subsystem.     The defini-
                    based on the ambiguity removal al-            tion of Level 1.0 was changed according-
                    gorithm.   The PI's wanted all direc-         ly.  See Tables I and 2B.
                    tional ambiguities delivered in addi-
                    tion to the selected wind vector.             5.2 Data Catalog
                    With such a product, investigators            A distributed DBMS was adopted for the
                    could re-select wind direction based          catalogs.    This will keep the catalogs
                    on another algorithm or ancillary             up-to-date in all three subsystems. In-
                    data (such as in situ).                       stead of transferring catalog information
                                                                  once a day, the catalog information about
               (c)  A requirement was generated to deli-          the products will be transferred to a
                    ver SSM/I    data colocated with a      a     subsystem   whenever    the   products    are
                    data, in order to make atmospheric            transferred.   In other words, the minimum
                    corrections instead of the flagging           information which is needed by the recei-
                    done by the Data System. Furthermore          ving subsystem will be redundantly stored
                    it was desired to have an SSM/I pro-          in   both the generating and receiving
                    duct compatible with the Level 2.5            subsystems.
                    wind vector product.        This would
                    allow    calculation of wind speeds           5.3 Host Instrument Operations
                                                                  Inasmuch as the ingestion function was
                                                                  relatively low in computer loading, it

                                                              476

             was a suitable place to host Instrument                  production and archiving.       However,
             Operations.    The ingestion functions can               no "on-line" selection and generation
             be completed in four to six hours, leaving               for users.    Users submit a request
             ample time for expected Instrument Opera-                (by mail) which is filled by the team
             tions activities.    Even during periods of              and sent to the user on tape.
             high activity, such as a instrument anoma-
             ly, normal ingestion can keep pace on an            (c) No on-line requests-- There is no
             altered schedule.                                       need for an outside user interface.
                                                                     Further, there is no need for rapid
             5.4   Data Granularity                                  subsetting in order to limit user
             The revs were redefined as beginning (and               connect time.     This greatly reduces
             ending) at the southernmost latitude. The               archive sophistication.        A fairly
             ao s in this region cannot be used for                  simple file cataloging system, where
             wind retrieval because of the presence of               data is stored by revs, is suffici-
             land and ice.   Thus, usable data from one              ent..   Because the phone or network
             rev   never overlaps the adjacent revs.                 line to this subsystem is no longer
             This redefinition resulted in no loss of                needed, system security is improved.
             wind  vector data.
                                                                 5.5.3 Need for electronic communication
             5.5         Science Team Requirements               The need for communications among PI's
                                                                 and with the project for information and
             5.5.1  New or revised data products                 mail will be met by off-the-shelf elec-
             The revised level definitions are illus-            tronic bulletin board and electronic mail
             trated in Table I and summarized in Table           software. This provides a low cost, low
             2B.   Details of the changes are presented          maintenance   system.    Inasmuch as there
             below.                                              is no electronic connection to the sub-
                                                                 systems it provides good security for the
             (a)   Level 1.7 - Writing minimum data out          system.
                   immediately after binning, produces
                   a low volume (100MB), binned a. data                         6 CONCLUSION
                   product with little additional pro-
                   cessing.                                      As a result of the design changes, we now
                                                                 have a Data    System which is simpler,
             (b)   Level 2.0 changed - Level .2.0 was            especially in  the data archive and dis-
                   redefined to be all wind vector solu-         tribution subsystem.     The Principal. In-
                   tions but with a "check mark" on the          vestigators have data types which more
                   solution selected by the Data System          closely match their needs and give them
                   algorithm.                                    the flexibility they want.    The design of
                                                                 the Data System is now complete and im-
             (c)   SSM/I Tb and <Tb> - Providing the             plementation will begin soon.
                   original SSM/I Tb data cut into revs
                   satisfied the need for a product                          7 ACKNOWLEDGEMENT
                   compatible with a. data.    We defined
                   a new product, SSM/I <Tb>-, in which          The refined Data System design was the
                   the Tb's are averaged over a WVC.             product of a multidiciplinary design     team
                   This averaging was done for the en-           lead by Steve Gunter.       Members of the
                   tire scan including the inter-swath           team included Dan Bonbright, Gloria      Con-
                   gap-  This was organized in exactly           ner, Robert Insley, Chris Leng and the
                   the same way as the Level 2.0 data.           authors.
                                                                 We would like to thank the other members
             5.5.2  Different Delivery Method                    of the NSCAT Data System Team for their
                                                                 assistance with the overall design and
             (a)   Standing Orders method preferred -            their work in software development.
                   Most data will be requested by PI's
                   with a standing order which is sent           The work described in this paper was
                   in advance and infrequently changed.          carried out by the Jet Propulsion Labora-
                   Immediately after level data produc-          tory, California Institute of Technology
                   tion, the data specified by the order         under-contract with the National Aeronau-
                   is extracted to disk or tape.      When       tics and Space Administration.
                   a sufficient volume of data for a PI
                   is collected or a time limit (one                           8 REFERENCES
                   month) is passed, the data is shipped
                   on tape.                                      1.  Martin, B D, Freilich,    M H, Li F Kv
                                                                 Callahan, P S, "An overview   of the NSCAT-
             (b)   "Historical" archive - The archive            /NROSS Program," Proceedings of a Work-
                   and distribution subsystem still must         shop on ERS-1 Wind and Wave Calibration,
                   handle historical requests, i.e.              Schliersee, FRG, 22-6 June, 1986 (ESA SP-
                   those that arrive well after data             262, Sept. 1986)

                                                            477

                                                                                                                                                            TABLE 2A
                         2.       Callahan, P S, Benada, J R,                                       "NASA                                      ORIGINAL DATA LEVELS
                         Scatterometer Data Processing System -
                         Features for Validation," ibid.                                                                  LEVEL              ORIGINAL DEFINITION
                                                                                                                          LO                 Rev oriented NSCAT telemetry
                                                                                                                                             data (This is raw data, i.e.,
                                                                                                                                             without any conversion.)

                                                                                                                          L1.0               Rev oriented, decommutated, EU
                                                              SUBSATELLITE                                                                   converted, and nadir point lo-
                         ANTENNA 6                            TRAC K                                ANTENNA I                                cated NSCAT data in engineering
                                                                                                    ANTENNA 2                                unit.
                                                           45--             _45'                                          L1.5               Rev oriented data reduced                                     to
                                                                            -65'
                                                                                                                                             normalized                backscatter                   cross
                                                                                                                                             section, earth located sigma-0
                                                                                                                                             cells with all geometry param-
                                                                %                                                                            eters for each cell, and flags
                                                                                   REFERENCE                                                 for the ice and land.
                                                                                   CELLS                                  L2.0               Rev oriented Wind Vector Cells.
                                                                                                                                             (with wind directional ambigu-
                                                           5!_                                                                               ities). The data is stored in 50
                                                                                                                                             km grid form.
                         ANTENNA 5                         45!._            _45'

                                                                                                                          L2.5               Rev oriented WVCS with only
                                                                                                                                             selected solution included.
                         ANTENNA4- LEFTWINDVECTOR                           RIGHT WIND VECTOR ANTENNA 3
                                         SWATH                              SWATH
                                                               175    175           600 k----@                            L3.0               Non-rev oriented wind map.
                                      -        600 k--Km +            k@

                         Figure 1 NSCAT Antenna Pattern                                                                                                     TABLE 2B
                                                                                                                                                    NEW      DATA LEVELS

                                                                                                                          LEVEL                             NEW DEFINITION

                                                              TABLE I                                                     LO                 Deleted
                         FUNCTION                             LEVEL                     SUBSYSTEM
                                                              ORIG          NEW         ORIG NEW                          L1.0               The same as the old definition
                                                                                                                                             except that the data is not
                                                              LO.0                                                                           nadir located.
                         Telemetry ingest                                               I         I
                         UTC time convert                                                                                 L1.5               No change.
                         Cut rev's                            L1.0                      I         I
                         Decom and DN-EU                                    LI.V        P                                 L1.7               Sigma-0 cells grouped in sub-
                         Nadir location                                                           P                                          track-grid                 ("binnned")                  form,
                         Cell location                                                                                                       i.e.,          the same form as Wind
                         Flag land, ice                                                                                                      Vector Cell.
                         Flag absorption
                         a. calculation                       L1.5          L1.5                                          L2.0               Combination of original Level
                         a. grouping                                        L1.7                                                             2.0 and 2.5 data, i.e., a check
                         Wind retrieval                       L2.0                                                                           mark will be made on the selec-
                         Vector selection                     L2.5          L2.0                                                             ted ambiguity while the rest
                                                                                                                                             ambiguities will be kept in for
                         I = Ingestion Subsystem                                                                                             reference.
                         P = Processing Subsystem
                                                                                                                          L2.5               Deleted

                                                                                                                          L3.0               No change
                                                                            -4
                                                                               5 @o

                                                           41 t-

                                                           To
                                     @U@FT'WIN.VEC R                        RIGHT NWIN._V@CMR
                                             1H
                                            .................. __           . . ......... ........

                                                                                                                  478

                                THE INFLUENCE OF PACING TECHNOLOGIES ON ENVIRONMENTAL
                                 APPLICATION OF SPACE-BASED SYNTHETIC APERTURE RADAR

                     Samuel W. McCandless, Jr.                            Dr. John Curlander

                      User Systems Incorporated                        Jet Propulsion Laboratory
                           4608 Willet Drive                             4800 Oak Grove Drive
                      Annandale, Virginia 2,2003                      Pasadena, California 91109

                             ABSTRACT                                          TABLE 1
                                                                           SPACE-BASED SAR
            space-based synthetic aperture radar (SAR)              PACING TECHNOLOGY ASSESSMENT
            sensing of ocean and polar regions began
            with the NASA SEASAT system in 1978.             ELEMENT              STATUS
            Since   then,    ocean   applications    have
            continued with space shuttle flights and         Exciter             Supports applications
            free-flyer satellites.    Each of these SAR                          requirements.
            systems have been applications limited due
            to technology driven design constraints          Transmitter         Available T/R modules &
            such as on-board recording (SEASAT, SIR-                             tubes over a wide range
            A), and data collection rate limits (SIR-                            of frequencies.
            A, SIR-B).       Recent breakthroughs in
            relevant    technology   areas   permit   re-    Antenna             Area & tolerance
            evaluation of SAR system architectures                               available to meet user
            and   design   approaches.       Innovations                         needs.
            include optical/digital on-board image
            processors,      advanced   magnetic     tape    Receiver            Bandwidth adequate for
            recorders      and    data     compression                           applications.
            algorithms.     This paper explores SAR                              calibration needs
            pacing technology areas       in terms of                            improvement.
            projected capabilities that will produce
            the most benefits for ocean users.               A/D Converter,      Data rate limitations
                                                             Data Recorder,      can reduce swathwidth,
                                                             Downlink.           coverage, dynamic range
                        SAR SYSTEM ELEMENTS                                      and range resolution.

            oceanic application of space-based SAR is        Image Processing    Does not support,real
            currently limited in the areas of data                               time application.
            rate conversion, storage, downlink and                               Processing choice and
            image processing, as shown in Table 1.                               location (space or
            This   barrier     can   affect    important                         ground) can limit
            performance values such as swathwidth,                               dynamic range,
            dynamic range, range spatial resolution,                             calibration
            sensitivity and real time application.                               sensitivity, range
                                                                                 resolution, etc.
            Several of the SAR subsystems can be
            eliminated from consideration as pacing
            technologies.   For most historic, planned       These subsystems    can be arranged in a
            and projected designs the portions of the        variety of ways.     Regardless of how the
            SAR from the radar transmitter through the       steps are performed, each can impose
            radar receiver can be eliminated as pacing       significant limits on SAR application.
            technologies.                                    Image signal processing can be performed
                                                             on-board (preceding the recording and
            The basic pacing technologies for space-         downlink steps) or on the ground.        Both
            based SAR are:                                   options will be discussed.

                - Analog to digital (A/D) conversion                       A/D CONVERSION
                - On-board image processing
                - On-board data recording                    If the data is to be processed digitally,
                - Data transmission to the ground            as is the current U.S. preference, it must
                                                             be sampled and converted from analog to
                                                             digital form, as shown inFigure 1.

                                           CH2585-8/88/0000- 479 $1 @1988 IEEE

                Following      the     analog-to-digital                          HIGH RATE RECORDER
                conversion of the video signal produced by
                the SAR receiver, the digital data stream            The high rate recorder system must be
                is typically time expansion buffered to              capable of recording at data rates of 50
                reduce the instantaneous data rate to a              Mbps and above with a recording capacity
                lower sustained rate which is continuous             of at least 8 Gbytes (about 20 minutes of
                over the interpulse period.                          operation) to handle even the simplest SAR
                                                                     system   (e.g.,    single   channel,    50    km
                For most SAR applications that require               swath).    For the multiple channel, wide
                high precision estimation of the echo                swath, multi -polarization SAR required to
                power, an 8 bit ADC is needed to prevent             meet future observation requirements, an
                significant saturation or quantization               order of magnitude better performance is
                noise in the sampled data.       A 300 MHz\ 8        needed.     To date, the most advanced
                bit ADC manufactured by Tetronix is                  recorder flown in space, manufactured by
                currently operationally used in airborne             Odetics Corporation,      is capable of a
                radar systems.        Techniques have been           maximum record rate of 60 Mbps with a
                developed for adaptive selection of the              maximum capacity of 8 Gbytes and a BER of
                four most significant bits from the 8 bit            10-7. This system has been flown on SPOT,
                ADC output to reduce the effective data              on the Shuttle with SIR-B     'and is planned
                rate.   A threshold level (or exponent) is           on upcoming SAR satellites such as JERS-1.
                calculated to accompany a block of data
                based on the average power in that block.            The , recording technique used in the
                This technique, referred to as Block                 Odetics and most ground recorders (e.g.,
                Adaptive   Quantization (BAQ), can reduce            Honeywell     HD-96)    is    called     linear
                the data  rate by a factor of 2.       The BAQ       recording, where as many as 42 parallel
                technique is being used by the NASA-JPL              longitudinal tracks have been packed onto
                Magellan Venus Radar Mapper and the                  a one inch wide tape.            The helical
                Shuttle    Imaging     Radar    SIR@C,     both      recording format can realize 600 tracks
                scheduled  for early 90s operation.                  per inch producing a significant increase
                                                                     in packing density.       The helical format
                A large amount of work has been devoted to           Schlumberger Industries model PV6410 (MIL
                another     data     reduction       technique       STP 2179) is capable of 240 Mbps                a
                identified as pre-image data compression.            capacity of 50 Gbytes at a BER       of <1;_10
                However, this area is   much less promising.         (Reference 1).       This machine is being
                Using    noiseless      (lossless)       coding      utilized in military combat           aircraft,
                techniques, such as a Huffman code to                helicopters, and ships.       It is   currently
                eliminate redundancy in the data, will               undergoing testing by NASA for use with
                yield no  more than a    20 to 30% reduction         SIR-C.
                in data volume.         This limitation is
                primarily due to SAR "speckle noise"                 Although high rate recording systems are
                effects.     Lossy coding techniques for             still a factor of 2 less than what is
                reducing the data volume/rate of the raw             required for projected SAR systems, the
                signal data, include a prototype system              compact size (1.3 ft.3), low power (0.3
                developed    by    Unisys.       This , system       KW) and light weight (66 lbs) of high rate
                implements a vector quantization fixed               recorders permit multiple systems to be
                code-book algorithm implementation.            A     flown on a single platform.         It appears
                prototype is capable of handling data                that over the next decade these systems
                rates of 100 Mbps and above.        Preliminary      will increase in performance even above
                testing    demonstrates that compression             current    specifications and        that the
                ratios of 4 to I can be achieved with                recording    technology will       not be       a
                little degradation in the resulting image            significant       limitation      in     future
                quality, however, this was done only for             spaceborne SAR systems.
                airborne X-band SAR data.           More work
                remains to prove that this is a viable                    OPTICAL IMAGE SIGNAL PROCESSING
                technique for spaceborne applications.
                                                                     An analysis of the current and future
                Following the buffering/coding stage to              technology as it relates to the signal
                reduce the peak data rate (typically by a            processing of SAR data must consider both
                factor of 4) the data stream passes into a           optical and digital computing systems. In
                data steering network.          This network         addition to the historic limitations of
                routes   the    signal   to    any of three                       processors, such as weight,
                destinations:       1)  On-board high rate           power    and    environmental      limitations
                recorder system; 2) SAR signal processor             (radiation      shielding,       outgassing),
                for image formation; or 3)             Downlink      consideration must also be given to system
                transmitter system for relay to a ground             control,    image    calibration,     processor
                station.                                             flexibility     and   reliability      (graceful
                                                                     degradation) issues.

                                                                 480

             The early versions of ground-based SAR              dynamic range of only 30dB can be achieved
             processors, some of which are still in              which is too small for high precision,
             operation today, were analog (optical)              calibrated SAR image processing.
             systems utilizing a laser light source
             with a series of lenses to perform the              Although tremendous strides have been      made
             two-dimensional    convolution processing.          in electro-optical computing over the      last
             Typically, film is used for both the input.         decade, major technological advances are
             and output media.        optical processing         still required before these systems can
             systems feature high throughput (real-              compete with digital computers in terms of
             time) relative to a digital processor, but          image quality and performance.          However,
             are constrained in terms of the dynamic             the potential       advantages     of    optical
             range of the film, limitations of the               systems for on-board SAR processing are
             lenses for high resolution imaging and              tremendous.     Specifically, the high speed
             swath width limitations.                            ADC and buffers shown in Figure 1 can be
                                                                 eliminated from the SAR system and the
             Recent technology advances in the,field       of    signal can be routed directly to the
             electro-optics         have   resulted        in    optical processor which in turn generates
             improvements in state-of-the-art optical            the image nearly instantaneously.          This
             computing.   A functional block diagram of          image is captured on a digital CCD and
             an optical SAR processor is shown in                routed to the downlink processor for
             Figure 2.      Specific advances include;           transmission to a ground receiver before
             available    semiconductor    light    sources      the satellite has. passed from reception
             (LEDs,   laser diodes)       that    are  more      range.
             reliable than previous light sources,
             acousto-optic devices      (AOD)   that have        Considering the size of the engineering
             improved     for   input     spatial. , light       community working in optical computing
             modulation use and semiconductor detector           today, it is reasonable to assume that a
             arrays (charge coupled devices -.. CCDs)            high performance spaceborne SAR processor
             that replace the film (Reference 2). With           will become     technically feasible within
             todays   technology    it   is   feasible to        the next decade.
             construct a real-time, compact, power
             efficient optical computer to perform on-                 DIGITAL IMAGE SIGNAL PROCESSING
             board processing of SAR imagery. However,
             improvements must still be made in the              The   tradeoff in digital versus optical
             area of performance,        flexibility      and    processing is typically performance for
             reliability.                                        throughput.     Digital signal processing is
                                                                 not theoretically limited in terms of the
             The performance in terms of the image               dynamic range, swathwidth, or resolution
             pixel   resolution will be limited by               that the processor can achieve but rather
             factors such as aberrations in the optics,          by the quality of input signal data and
             mechanical/electronic stability and light           the ancillary data such as platform
             source coherence.       Resolutions on the          ephemeris,,attitude and sensor calibration
             order of SEASAT SAR     (25m) are achievable        data.      It is fair to say that the
             with todays technology, but an order of             processing      algorithms/techniques        are
             magnitude    better    resolution     is    not     sufficiently mature today such that they
             currently feasible.      Additional problems        contribute little or no degradation to the
             exist with the light source.        Since the       resultant image quality.      The major issue
             duration of the light source pulse must be          in    implementing    an   on-board      digital
             shorter than the inverse BW df.the signal           processor ,is in- achieving the necessary
             to avoid range smearing, extremely short            computational     power within       the   size
             pulses (in the 10 nanosecond range) must            weight and power limitations of the
             be used.     This presents a problem with           platform.
             coherence    and    gain   transients     that
             effectively degrade the resolution.       This      Recent gains in semiconductor technology
             problem could be overcome if a pulsed gas           using    VHSIC   Gallium    Arsenide     (GaAs)
             laser were used, but this            is only        circuitry and advanced Complementary Metal
             currently feasible for a ground processing          Oxide Silicone (CMOS) devices produced
             system.      The    other major      area     of    with     Silicon      On-Insulator       (AOI)
             technology improvement is in the CCD array          architecture,      bode well       for major
             technology.      Currently CCD chips are            performance gains in the near future.
             limited in   width to 1000 elements.      This      Looming on the horizon is the potential of
             limitation   can be overcome by interfacing         superconductivity       revolutionizing      the
             a number of chips to realize a wide range           microelectronics industry. Superconductor
             swath, however, the time bandwidth product          research is on-going to greatly increase
             of the AOD may then become a constraint on          the    cycle - time      through      improved
             the    swath   width.       Another severe          junctions.
             limitation of existing CCD arrays is the
             dynamic range. Without special cooling to
             reduce the dark current, a reliable

                                                             481

               The state-of-the-art in terms.of currently        the requirements on the digital downlink
               available or near operational technology          and the ground data handling systems.
               primarily utilizes CMOs circuitry which
               exhibits      excellent        speed/power                      DIGITAL DOWNLINK
               characteristics     (Reference   3).       For
               spaceborne    systems,   a   64K    radiation     With recent technology advancements in
               hardened RAM and a 16 bit radiation               digital telecommunication systems, wide
               hardened microprocessor (8OC86RH) are to          bandwidth    digital     links   have   become
               be used in the Mars Observer satellite.           commonplace.    The NASA Tracking and Data
               One   of    the most    advanced processor        Relay Satellite (TDRS) has two 150 Mbps
               candidates for space use is the IBM Common        communication     channels    for   a    total
               Signal Processor' (CSP) developed for the         capacity of 300 Mbps.       To increase the
               Advanced Tactical Fighter (ATF) program           link capacity or equivalently the system
               and    used    in  conjunction    with     the    bandwidth requires an increase in power to
               Westinghouse Ultra Reliable Radar (URR)           offset the commensurate increase in noise.
               (Reference 4).    The architecture consists
               of a number of processing elements each           Considering the potential of on-board data
               rated at 125 MFLOPS contained in a module         processing    and   compression    the    next
               with 32 Mbytes memory.     The system can be      generation of direct downlink systems and
               configured with a number of modules each          data relay satellites should be able to
               interfacing into a common data network            handle data rates on the order of 0. 5 to
               achieving a maximum p@erf ormance of 1, 8         1.0 Gbits/sec, which even after error
               GFLOPS.     The CSP uses CMOs technology,         correction    coding    is   equivalent     to
               does not    require special cooling and is        instantaneous rates of 8 Gbits/sec coming
               currently constructed with 6 x 9 in.              from the SAR ADC (Reference 6).             As
               boards (2   ft.3 volumey.   Considering that      previously     reviewed,     the    recorder
               this system is within a factor of 4 of            technology to capture such a data stream
               what is required for SEASAT real-time             is currently available.        A number of
               processing, it is highly probable that the        recorders, each with a 240 Mbps capacity
               technology will soon exist for spaceborne         could be interfaced in parallel to achieve
               high resolution real-time SAR processing.         the desired capacity.

               An,alternative approach for the SAR signal                     GROUND DATA SYSTEM
               processor architecture is to. develop a
               custom chip taking advantage of the highly        It is reasonable to conclude that existing
               repetitive nature of the SAR pr       ocessing    IC technology and data networks (using
               algorithm.   The range processing could be        fiber   optics)    make    the  question    of
               performed with an.analog device (such as a        feasibility of real-time ground processing
               SAW filter) before digitization as shown          mute.   The pertinent question is not the
               in Figure 3. Following the ADC, a azimuth         feasibility of such a system, but rather
               correlator chip could be designed that            what is the optimal architecture and what
               does not require a corner turn of the data        systems exist or are under development? A
               from a range file to an azimuth file.             number of     organizations    have    already
               The most efficient algorithm for this type        built custom   signal processors with GFLOP
               of   implementation    is the time-domain         computation   capabilities.      Specifically,
               approach where the azimuth correlation is         the Advanced Digital SAR Processor (ADSP)
               a convolution,operation (Reference 5).       A    designed and built by NASA/JPL to support
               custom chip is required that performs             the Magellan Venus Radar Mapper and the
               resampling     for. the    range    migration     Shuttle Imaging Radar (SIR-C) has been
               correction     fo-llowed    by    a   complex     demonstrated to be capable of 6 GFLOPS.
               multiplier for the reference function
               weighting and an accumulator          (complex    An architecture with dedicated pipeline
               adder with memory for one range line) .           processing modules, custom designed to
               This chip would be replicated for each            perform a specific function will reduce
               element     in   the   synthetic     aperture     system reliability, since a failure will
               followed by a multiplexer to recombine the        typically halt all processing.            This
               data.    This approach does not appear to         architecture is used in the ADSP.       It is
               represent     any  significant    technology      capable of extremely high computational
               drivers, although this chip has never been        rates when the pipeline is full, but
               fabricated.                                       relies on every module to be functioning
                                                                 for the system to be operational (i.e., no
               The signal processor should also be               graceful degradation).
               followed by a compression subsystem which
               performs spatial compression of the SAR           The IBM CSP represents an alternative
               imagery.       Studies   have    shown    that    approach using multiple identical boards
               compression ratios of 20:1 are achievable         for each type of processing (e.g., FFT,
               with little degradation in the image              memory, complex interpolators) and routes
               quality.    This would significantly reduce       the data using a high speed switch to each

                                                             482

             board as required in the processing                   A more achievable specification for the
             algorithm.         One    drawback     to    this     calibration within the next ten years is
             architecture is the extremely high data               0.2 to 0.3 dB. This will require internal
             rates at the data transfer node. However,             calibration signals to characterize the
             this    system does        feature      graceful      amplitude and phase characteristics of the
             degradation at the computational board                system (including the antenna) over the
             level.                                                entire      signal     bandwidth.            This
                                                                   information must then be input to the
             A third potential architecture is the                 processor     to   modify    the     appropriate
             concurrent processing system such as the              processing parameters in near-real-time.
             Massively Parallel Processor (MPP)
             developed by Goodyear for the NASA Goddard            High     precision      GPS    and     attitude
             Space    Flight     Center    (GSFC)    or    the     determination      are   also    required      for
             Hypercube developed by Caltech/JPL. These             estimation of the Doppler parameters and
             systems consist of a large number of                  the antenna boresight.           All of these
             identical microprocessors each with local             elements are technically feasible but have
             memory.        The microprocessors are                yet to be incorporated into an
             interconnected       to each       other with         operational system.
             different configurations for each
             application.     For example, the MPP is a                              REFERENCES
             planar array with each microprocessor
             communicating with its nearest neighbor.              1.   "Digital Helical Scan Cassette
             The     Hypercube       permits        multiple            Recorder", Schlumberger Fairchild
             interconnection schemes such that any                      Weston Systems, Inc., Recorder
             processor can communicate with any other.                  Division, Sarasota, Florida, Product
             As the microprocessor technology improves,                 Announcement, 3-88.
             this type of architecture becomes more
             desirable due to its high redundancy,                 2.   Psaltis, D., K. Wagner, "Real-Time
             system reliability and flexibility.                        optical Synthetic Aperture Radar (SAR)
                                                                        Processor", optical Engineering,
                                 SU14MARY                               9/10-82.

             The current state-of-the-art and expected             3.   Bursky, D., "Tackle Real-Time DSP with
             future developments in data handling and                   CMOS Chip Set", Electronic Design,
             on-board signal processing were presented                  3-31-88.
             at a     functional module level.             The
             analysis     indicates    that    the     primary     4.   "IBM Will Deliver Initial common
             technology driver is in the spaceborne                     Signal Processor to Air Force",
             image signal processor.       optical, digital             Aviation Week and Space Technology,
             or combination hybrid designs can be                       7-4-88.
             considered for space-based
             implementations.                                      5.   Assal, H., J. Vesecky, "Spaceborne SAR
                                                                        Azimuth Processor VLSI Implementation
             If an on-board     processor is implemented,               Assessment", Stanford University,
             this system could be followed by a data                    Scientific Report D909-86-1, 12-86.
             compression system that would reduce both
             the data rate and volume by a factor of at            6.   Pritchard, W.', "Satellite
             least 20. This would alleviate any issues                  Communications - An overview of the
             regarding the capacity of available high                   Problems and,Progress", Proc. of the
             rate recorders and downlink systems.                       IEEE, Vol 65, no. 3, pp. 294-307.

             The only area of lingering concern is the
             control of the processor and the data
             calibration. The requirement that the SAR
             must be capable of discerning small
             changes in the radar cross section is an
             extremely difficult specification to meet
             in the laboratory, not to mention in
             space.     A rule of thumb is that the
             calibration accuracy is inversely
             proportional to the resolution. Thus, the
             higher the resolution, the poorer the
                                  4formance.
             calibration per                          Typical
             specifications      for planned       spaceborne
             systems (e.g., SIR-C) are on the order of
             0.5 to 1.0 dB for the relative calibration
             (stability)     of   the   system.       It     is
             difficult to make a measurement to better
             than 0.1 dB.

                                                               483

                     F)GURE    I     FUNCTIONAL BLOCK DIAGRAM OF                                     SAR
                                     MULTI-CHANNEL SPACEBORNE RADAR                                  IlF
                                     SYSTEM WITH ONBOARD PROCESSOR                                   OUTPUT

                                                                                                       SAW        X      LPF        AOC
                                                                                                       FILTER                                                     v
                                                                                      0
                                                                                      A                                                     AC       AC          AC
                                                                  =BUFFRl                                                                                         N
                                                                        ER/           T
                               RCVR                               Coo FE              A                     A                                1        2
                                                                         r
                                                                  CODING                                                 AZ REF FUNC
                                                                                      s                                  @GENERATOR
                                                                                      T                                                                   ----

                               RCVR                               BUFFER/             E
                                                                  CODING              I           RANGE
                                                                                      N.          MIGRA71ON       INTERPOLAT ON                   MULTI-PLEXER
                                                                                      N
                               RCVR                               BUFFER/
                                                 ADC                                  T
                                                                  CODING              W                                                               OUTPUT IMAGE
                                                                                      0                            com
                                                                                      R           REF FUNC         MUL  IPLY
                                                                                      K                                                  B

                                                                                                                         +
                                          A   -----------  ON-BOARD
                                          T
                                          A  -4  ---------0PROCESSOR
                                                                                                                        A
                                                                                                                        C;
                                          T                                                                             c

                                                         OAT
                                                          COMPR
                                                                                                                            OUTPUT
                                          N
                                          Z                                                         FIG     3 ARCHITECTURE FOR:
                                          T
                                          w                 GH RATE                                         A) HYBRID ANALOG/ DIGITAL TIME DOMAIN SAR CORRELATOR
                                          0
                                          R                                                                 B) AZIMUTH CORRELATOR       AC   CHIP
                                          K

                                                        DOWNLINK TRANSMITTER

                                 SAR VIDEO SIGNAL SHIFTED TO CENTER OF ADD BAND

                                                                                                                                                  S   (t)

                                     LIGHT                        COLLIMATING                          FOCUSING                           ACOUSTO
                                     SOURCE                  P.       LENSE             --------  0      LENSE                            OPTICAL@
                                                                                                                                          DEVICE

                                     MATCHED                                                                  CCD                             OUTPUT
                                     FILTERING                                MASK                            OUTPUT                          IMAGE
                                     (3 LENSES)
                                                                                                       @
                                                                                                       'TPUT            PL,
                                                                                                       SAW
                                                                                                       FILTER

                       FIG        2             FUNCTIONAL BLOCK DIAGRAM OF OPTICAL SAR PROCESSOR

                                                                                            484

                                         A COMPUTER PACKAGE FOR THE PARAMETER OPTIMIZATION OF GROUNDWAVE RADAR

                                              D.S. Bryant, A.M. Ponsford and S.K. Srivastava

                                                               NORDCO Limited

                                     ABSTRACT                                 their differing Doppler shifts.

                 The increasing popularity and diverse
                 applications of groundwave radars operating                  A typical example of a groundwave radar is
                 in   the   HF band    has   necessitated      the            shown in Figure 1.     An omni-directional, or
                                                                              wide beam, antenna is used on transmission,
                 development    of   a   generalized     computer
                 simulation package.                                          to   "floodlight"     the   desired      sector.
                                                                              Directional information of the reflected
                 This paper describes such a software package                 target signal is then obtained, on reception,
                 and shows how it can be used at the design                   using a wide aperture, phased array, antenna.
                 stage to optimize the many radar parameters                  Effective target detection, in the presence
                 for   a  particular    application.        These             of sea clutter returns, involves the coherent,
                 applications may vary from the remote sensing                integration of the echo over a period of time
                 of the sea state to an early warning system                  which is dependent upon the type of target
                 for the detection of low flying aircrafts.                   being interrogated.   For a ship target, with
                                                                              a Doppler frequency within the Doppler
                                                                              spectrum of the sea, a coherent integration
                                                                              period in the order of hundreds of seconds is
                          1. REVIEW OF GROUNDWAVE RADAR                       required.   For the detection of a high speed,
                                                                              low flying, aircraft, whose Doppler frequency
                 Over-the-horizon groundwave radars        utilize            lies well outside the Doppler spectrum of the
                 the low attenuation rates of vertically                      sea, the coherent integration time can. be
                 polarized HF electromagnetic waves when                      reduced to the order of tens of seconds.      The
                 propagated over the conductive sea surface.                  remote sensing of the sea state however,
                 These waves will be scattered from objects                   requires long Dwell times in the order of
                 having a substantial vertical dimension and                  tens of minutes.
                 the resulting radar return will have a
                 precise Doppler frequency shift that is                      Typically the radar will be required to cover
                 proportional to the radial velocity of the                   a specified angular sector in a given period
                 target.  In addition, the sea surface acts as                of time.    A single narrow beam scanned in
                 a  spatially distributed       collection of                 azimuth, as in microwave radar, is therefore
                 scatters for which the radar return will                     non-ideal.   This is because of the need to
                 typically be greater than that of the targe   t.             maintain a sufficient search rate to ensure
                 Discrimination between the target echoes and                 the early detection of new targets and the
                 the sea echo is achieved on the basis of                     accurate tracking of known targets whilat

                                                   CH2585-8/88/0000- 485 $1   @1988 IEEE

                     still allowing a sufficient dwell time to                    these   Bragg    returns    that    information
                     eliminate the clutter return.     The HF radar               concerning the ocean currents and surface
                     must therefore use multiple beam synthesis                   wind direction can be obtained.               The
                     techniques to cover the desired surveillance                 backscatter from a target will also have a
                     area.                                                        Doppler frequency shift which is proportional

                                                                                  to the r   adial component of the target
                     operation in the spectrally congested HF band                velocity.    Doppler frequency shift      for a
                     dictates that the radar is compatible with                   variety of target radial velocities, as a
                     the narrow band communication user.           The            function of radar carrier frequency, are
                     radar   must    be   designed    to    minimize              plotted in Figure 2.
                     interference both t o, and from, other users.
                     To control spectral spread the envelope of                   The ability of a groundwave radar to track
                     the transmitted pulse is shaped.      since the              ships   using    multiple     beam     synthesis
                     bandwidth of transmission is regulated at HF,                techniques, has been demonstrat  -ed by Ponsford
                     the range resolution will be in the   Iorder of              et al; 1987.
                     several km's.

                     To maximize the operational range of the                              2. GENERAL OVERVIEW OF MODEL
                     radar it is necessary that the receiver has
                     atmospheric noise level sensitivity.           To
                     avoid losses associated with beamforming at                  The necessity  to optimize the design of an HF
                     the radar carrier frequency and to maximise                  groundwave radar has led to the development
                     the sensitivity of the radar, each array                     of a generalized  computer simulation package.
                     element must be allocated its own receiver.                  Barrick (1972) has developed models for the
                     The adoption of this approach has the                        first and second orders of the backscattered
                     additional advantage of increased flexibility                radar cross section of the ocean surface.
                     offered by post-detection beam synthesis.                    Using the concept of generalized functions,
                     This in turn requires that the receiving                     Walsh   and    Srivastava      (Walsh;    1980,
                     channels must now be matched in both gain and                Srivastava;    1984,   Walsh   et   al;   1986)
                     phase characteristics to a degree of accuracy                developed a similar model for the         ocean
                     consistent with the specified b    eam patterns              clutter.   However, their second order    model
                     (Ponsford et al; 1988).                                      consists of three parts.     The first part of
                                                                                  second order represents the case where both
                     The radar distinguishes between targets and                  first order and second order scatterings
                     clutter returns by spectral analysis of the                  occur on the angular section (defined by the
                     backscattered signal.      The clutter return                receiving system beamwidth) of the circular
                     from the sea surface has a characteristic                    annulus (defined by the range resolution).
                     Doppler spectrum.    The dominant contribution               The second part of second order represents
                     is produced by scatter from surface water                    the case where the first scattering occurs at
                     waves with a wavelength exactly one half of                  the transmitting     point and     the    second
                     the radar signal wavelength and which are                    scattering falls on the angular section.      The
                     moving either directly towards, or directly                  third part of second order represents the
                     away from, the observing radar.              This            case where the two scatterings occur off the
                     condition is referred to as Bragg resonant                   angular section.   A geometrical illustration
                     scattering     by    analogy      with     X-ray             of  the   three   second    order    parts    for
                     crystallography.    It is from the analysis of               omni-directional transmission and reception

                                                                        4.86

                is given in Figure 3.                                                  antenna coupling losses, etc.)
                                                                                     - pulse length
                A cross section model for the target has also                        - pulse repetition frequency
                been developed by Walsh (Walsh et al; 1986),                         - antenna array height above sea
                which makes      extensive     use  of    Fourier                      level
                techniques in order to solve Maxwell's                               - system noise level
                equations for different physical targets.
                                                                                ii)  Environmental Parameters
                Models have also been implemented to
                describe:    the   radio    noise   level,    the                    - orientation of sea with respect
                propagation loss 2      and the wave height                            to radar
                spectrum.      The   propagation loss model                          - surface current, speed and
                employed has been adapted from Walsh et al;                            direction
                1986, and Rotherham; 1981.                                           - swell magnitude, period and
                                                                                       direction

                               3. COMPUTER MODEL

                The software structure consists of a series                     iii) Target Parameters

                of subroutine modules linked together by a
                main controlling program.      These subroutines                     - target speed and direction
                are called where needed via a menu driven                            - target cross section

                screen.

                                                                             b) System Characteristics:         This module
                The software package is broken into the                         implements    the   antenna gain      in    the
                following subroutine packages:                                  appropriate form.

                a) input Parameters                                          c) First Order and Second Order Sea Clutter:
                b) System Characteristics                                       This module utilizes a model designed to.
                c) First and Second Order   Sea Clutter                         calculate. first and second order sea
                d) CCIR Radio Noise (atmospheric and man                        clutter on a Doppler basis.
                   made) Level Calculation
                e) Propagation Loss Calculation                              d) Calculation of CCIR Radio Noise      Level
                f) Generation of Wave Height Spectr   um                        This. module generates external noise
                g) Output Options                                               levels (ie., man7made, atmospheric and
                                                                                galactic)     utilizing     standard      CCIR
                A brief description of each of the above                        algorithms and data (CCIR, 1982).

                follows:
                                                                             e) Propagation Loss:     A standard spherical
                a) Input Parameters                                             earth propagation model        is   used    to

                                                                                account    for  diffraction     around     the
                   i)  System Parameters                                        earth' s surface.      A modified surface
                       - radar carrier frequency                                impedance is used to account for the
                       - peak transmitter power                                 effects of ocean waves on the transmission
                       - antenna (array) gain                                   loss.
                       - horizontal beamwidth   (3 db)
                       - system losses (cable   losses,

                                                                      487

                                                                                                     REFERENCES
                   f) Generation of Wave Height Spectrum: A wave
                      height spectrum is generated based on the                   Barrick, D.E., (1972) REMOTE SENSING OF THE
                      sea state characteristics provided.         The                 SEA STATE BY RADAR, in Remote sensing of
                      actual model utilized is one developed by                       the Troposphere edited by V.E. Deit, US
                      Pierson    and   Moskowitz     (1964),    with                  Government Printing Office.
                      cardoid directional distribution.                           C.C.I.R.  (International Radio Consultative
                                                                                      Committee) (1982), WORLD DISTRIBUTION AND
                   g) output Options- The outputs provided are                        CHARACTERISTICS OF ATMOSPHERIC RADIO
                      listed below and are illustrated in
                                                                                      NOISE, Report # 322, Geneva, 78 pp.
                      Figure 4.                                                   C.C.I.R. (International Radio Consultative
                        i)   A Doppler spectra of the                                 Committee) (1982), MAN-MADE RADIO NOISE,
                             received signal                                          Report # 258-4, Geneva, 177-183 pp.
                        ii)  A Doppler spectra of the                             Pierson, W. J.  and Moskowitz, L. (1964).         A
                                                                                      PROPOSED    SPECTRAL    FORM    FOR FULLY
                             normalized cross section of
                                                                                      DEVELOPED WIND SEAS BASED ON THE
                             each component of the sea                                SIMILARITY. THEORY OF S.A. KITAIGORODSKII,
                             clutter and the total sea                                J. Geophys. Res., 69, 5181-5190 pp.
                             clutter, and                                         Ponsford, A.M., and Bagwell, D.J.,, (1988),
                      iii) A target visibility profile                                RECEIVER DESIGN FOR HF GROUNDWAVE RADAR,
                             as a function of range.                                  IEE Int. Conf. 'HF Radio Systems and
                                                                                      Techniques", Conf. Pub. 284, 254-258 pp.
                                                                                  Ponsford, A.M., Bagwell, D.T., Money, D.G.,
                                                                                      and Gledhill, M.H., (1987), PROGRESS IN
                   The computer simulation package has been
                   extensively tested against published data                          SHIP TRACKING BY HIP GROUNDWAVE RADAR, IEE
                   (Wyatt et al.,      1985).    The two    .separate                 Int. Conf. 'Radar 87', Conf. Pub.
                                                                                  Rotherham, S., (1981), GROUNDWAVE PROPAGATION
                   approaches by Barrick,       and by Walsh and                      Part 2, IEE Proc., Vol. 128, No. 5 Oct.
                   Srivastava give consistent agreement with the
                                                                                  Srivastava,     S.K.  (1984),    SCATTERING OF
                   measured data.
                                                                                      HIGH-FREOUENCY ELECTROMAGNETIC WAVES FROM

                                                                                      AN OCEAN SURFACE:           AN ALTERNATIVE
                   NORDCO is in the process of developing its                         APPROACH INCORPORATING A DIPOLE SOURCE,
                   own groundwave radar facility. This facility
                                                                                      Ph.D. Thesis, Memorial University of
                   will be used to        further validate        the                 Newfoundland, Canada, available from
                   simulation package in order that optimum                           Canadian Theses on Microform Service,
                   operational performance can be achieved for                        National     Library     of    Canada,        395
                   given target and environmental conditions.                         Wellington, Street, Ottawa, Ontario KIA
                                                                                      ON4, Canada, 305 pp.
                                   ACKNOWLEDGEMENTS                               Srivastava, S.K. and J. Wal    sh, (1985),        AN
                                                                                      ANALYSIS OF THE SECOND ORDER DOPPLER
                   The authors would like to thank..NORDCO Ltd.,                      RETURN FROM THE OCEAN SURFACE, IEEE J.
                   for their permission to publish this paper.                        Oceanic Eng., OE-10,.443-445 pp.
                   The work has been supported by DND Canada and                  Walsh,   J.,    (1980),   ON THE THEORY OF
                   the Atlantic Accord Development Fund.                              ELECTROMAGENTIC PROPAGATION ACROSS A
                                                                                      ROUGH SURFACE AND CALCULATIONS IN THE VHF

                                                                          488

                         REGION, Technical Report prepared for the
                         Defence Reseach Establishment Atlantic
                         (DREA),       Department        of      Supply       and
                         Services,     Government of Canada, available
                         from ocean Engineering information Centre
                         (OEIC),       Report     #    N00232,        Memorial
                         University of Newfoundland, St. John's,
                         Newfoundland, Canada, AlB 3X5, 195 pp.                      9
                  Walsh, J., B.J. Dawe and S.K. Srivastava
                         (1986), ANALYTIC MODE DEVELOPMENT FOR TR                    0
                                                                                                                                            01PIE. WF'      '.W -IW
                         STUDY OF GROUND WAVE RADAR AS REMOTE

                         SENSOR IN AN OCEAN ENVIRONMENT, Prepared
                         for the Department of National Defence,                                  ........
                                                                                                    6        0  11  1.     a 1.  20  22  24   2.  2.  30
                         Ottawa, Ontario, Canada.                                                                RADAR CARRIER FREQUENCY IMHA
                   Wyatt,    L.R.,     Burrows,     G.D.,    and     Moorhead,                    FIGURE 2 Target Doppler as a function of radar carrier freciusncy
                         M.D., (1985), AN ASSESSMENT OF A FMICW
                         GROUND WAVE RADAR FOR OCEAN WAVE STUDIES.
                         Int. J. Remote Sensing, 1985, Vol. 5 No.
                         1, 275-282 pp.

                                                                                                                                 y

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                                                                                                             'second       first
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                                                                                                                                                      second
                                                                                                                                                      scatter
                                                *A"C        A.,

                                                                                                                   (PO-A   P   P @s (PO + AP)

                                                                                               Fig. 3        Three parts of second-order backscatter
                                                                                                             from a circular annulus and off the
                                                                                                             annulus for omidirectional transmission
                                                      CEIIANJ                                                and reception. (Po= distance of
                                        DMIN        AWAY                                                     annulus;.2 &9@= radial width of annulus;
                                                                                                             F's        groundwave attenuation functions
                           Figurel.l. GROUNDMVE  PULSE DOPPLER RADAR                                         with modified surface impedances.
                                                                                                                                              -*' "'ru "",
                                                                                                                                              scatter

                                                                                         ,489

                                                                                                                                                               -0617

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                        RESULTS OF EXACT INVESTIGATIONS ABOUT THE CHARACTERISTICS OF THE EXTREMELY FAST AND
                        ACCURATELY, MEASURING KIEL MULTISONDE AND REPRESENTATIONS ABOUT ITS NEWEST PERFORMANCE

                                                                          by

                                                                      Werner Kroebel

                                           Institute for Applied Physics, University of D-2300 Kiel, FRG

                                A B S T R A C T                               totally new generation-of C-T-D sondes.
                 Prearrangings to further developments in the                 The author already came to the same conclusion a
                 ocean research are actual and challenge the de-              couple of years ago, but other than the considera-
                 velopment of a total new generation of C-T-D                 tions of the "WOCE" committee, that generally for
                 sondes. Therefore, many efforts have been made               example temperature measurements in situ in the
                 during the last 2 years. Anyway, this problem is             Sea need probe devices with definite smaller time
                 still of high actuality. Now, the author has                 constants for all C-T-D sensors than those used
                 found a new and special solution for this problem.           before. Since the commonly used temperature sensors
                 It concerns new devices of the sensors as well as            with their relatively big time constant caused, in
                 of the needed electronic circuits. At present                terms of suddenly appearing changings in the tempe-
                 this new C-T-D sondes have been exactly tested.              rature profiles, faults by great delay of time as
                 Theiresults are: All C, T and D sensors have a               well as suppressions of the fine structures in the
                 very short time constant. For example T .5 msec,             graphic representations. These faults cannot be
                 the accuracy     .3 mK, the resolution    .12 mK,            compensated by calculation. Furthermore in these
                 the electric circuits allow to repeat all                    cases, the measured temperature data range does
                 measurings in periods of 2 msec. The spatial                 not correspond,to the measureddata taken at the
                 resolution for C is .5 cm, the precision .001,               same time of the electric conductivity and the
                 the resolution .0005. At present, the pressure               pressure to the a  'ctual same depths. Besides, the
                 sensor can reach a precision of about �1,5 m                 calculation of deviative units of measurands as
                 between 0-600 bar, a resolution of �30 cm.                   of salt content and density leads to the well
                                                                              known spikes in the graphic depiction of profiles.
                                                                              Moreover, real existing changings in the kind of
                                                                              jumps in thetemperature profiles notify important
                           I N T R 0 D U C T 1 0 N                            marks for bounderies between superimposed different
                                                                              layers of water. Thus they are re.levant and give
                About 4 to 5 years ago it seemed to be about time             characteristic informations for the interpretations
                to undertake an universal determination of hydro-             ofprofile courses under the different parameters.
                graphic data of the Sea. This lead to developing              Since, on the other hand, such fine structures of
                and planning an international program of measuring,           those transition regions from one to the other
                which became popular about 1984 under the name of             layers can have extensions between cm, dm and m.
                "WOCE". Based on intense thoughts about the extent            In order to find out this transitions with its
                of this program, it was deducible that it was                 fine structures all measurable parameters must
                realistic and possible only, if beforehand essen-             have time constants ranging between msec. and less
                tial progress,    on the used measuring instrument            referring to the high speed of lowerings of the
                was achieved. This concerned especially the C-T-D             C-T-D sonde. A further reason for the necessity of
                sondes. Therefore, they had to be developed in                fast measurings is the requirement to quasi synop-
                order to meet the necessary standards.                        tic measurements.

                This requirement referred to the-feasibility of               BRIEF    REPORT ABOUT FEASIBILITIES OF HIGH SPEED
                fast measurements in terms of times of only a few             C-T-D MEASURINGS IN SITU
                milliseconds, on increasing the accuracy in
                measurement up to 16 bit per measuring range for              Based on these considerations the author took [1-1
                the temperature and the electric conductivity                 efforts in the seventies to develop first of all
                parameter plus a new pressure sensor for the depth            a high speed measuring temperature probe. 1978 he
                destination with an accuracy of � I meter for a               succeeded in realizing such a thermic sensor with
                range of 0 up to 600 bar as well as essentially               time constants in the range of .5 msec. Some of
                increased speed of lowering of the C-T-D sondes               those high speed measuring temperature sondes were
                through the hydrosphere. Since all available                  first applied in a very thorough hydrographical
                C-T-D sondes did not meet these standards, all                surveying of the Lake Constanz in July and
                producers of these sondes definitely knew that        the     November of 1979 [2]. They came up with results
                "WOCE" experiment required the development of a               which depicted a relevant meaning for understanding

                                                       CH2585-8/8810000-, 491 $1 @1988 IEEE

                the dynamic of the lake even for temperature values           dissolving depth of .5 cm for measurements of the
                within the range of mK. Later in 1982 with this               electric conductivity in situ. The diameter of the
                type of probe it was possible to depict by means              cell tube was 16 mm, thus the seawater could flow
                of an expedition with the German research vessel              very quickly through the cell. Besides, the cell
                Poseidon that in the northern part of the Atlantic            was performed mechanically very stable.
                Sea changings in temperature occur in a number of
                ranges in depth within depth of more than 1 900 m             In respect of measuring the depth there were indeed
                in which the temperature only run up to about .1 K.           great problems confronting the new generation of
                (see fig. 1) DI                                               the C-T-D sonde by the available multiple types
                  POSEIDON 86 DATE. 9.4.82 STATION. 329 PROFILE, 72  21.S.32  of pressure sensors on the market, because they
                                                             13               did not allow high measurings speeds and simul-
                                           '4S    as         11               taneous sufficient accuracy in measurement.
                                                             74
                                                                              Besides, most of them were also not sufficient free
                                                                              of drift and the best of these were too expensive.
                                                                              Measuring of the drift of pressure sensors has
                                                                              been made by Wearn. R. B.., L@rson.. N. G. The
                                                                              result by these authors .'is to:,see-in Deep Sea Re-
                                                                              search Vol* 29, NOIA 82 [3]. This situation gave
                                                                              the author the suggestion to seek for a new and
                                    T4                   To                   genuine solution for measuring of a good fitted
                                                                              pressure sensor concerning marine measurements
                                                                              in situ. He found a new way about the pressure
                                    t                                         dependence of the electric resistance of a mercury
                                                                              filament. About a first performance of such a probe
                                                                              he gave a presentation on the "Ocean 8711 [5a].
                                                                              Parallel to his efforts, independent of him, also
                                                                              Neil Brown had himself turned towards to seek a
                                                                              new solution about this problem. And also Neil
                                                                              Brown presented his new interesting ideas and re-
                                                                              flections on this problem with his first results
                    7------- 7--                                              on the "Ocean 87" [5b].Since that time the new
                                                                              solution for a pressure gauge by the effect of
                                                                              changings of an electric mercury filament re-
                                                                              sistance has been carefully investigated under
                                                                              the authors guidance by his student B. Steffens       in
                                                                              his thesis as well as forward developed by the
                                                                              author himself. The result is now a pressure
                Figure 1.    Temperature  profiles at a depth of              sensor device, measuring high speed and with an
                1492 m to 1562 m in the   atlantik near the azores.           accuracy better than required by the "WOCE"
                T is a  Rosemount thermometer which takes a long              committee. Thus a new generation of a Kiel C-T-D
                time to reach the final resolution value with a               sonde, respectively multisonde by the author with
                sampling rate of 10/sec. T      T   T are thermo-             new genuine sensors and new performances are
                meters designed by Kroebel'@hiN ak characterized              existing. To this are added advanced as well as
                by time constants of approximately .5-1 msec with             decisive improved electronic circuits. To demon-
                a sampling rate of 50/sec. The differences are real           strate the properties of this C-T-D sonde it was
                and are caused frcm horizontal distances of about             necessary to investigate and to test the complete
                15 cm between the thermometers T4    and T7  and T   91       instrument very carefully.
                in us,ing a combination of many high speed measuring          THE ARRANGEMENT FOR TESTING THE NEW GENERATION OF
                temperature probes by this expedition it was                  THE KIEL C-T-D SONDE WITH AN ACCURACY ACCORDING TO
                possible to prove that in the transition layer of             THE STANDARDS AT PRESENT
                such a jump always water turbulences of minimal
                spatial extension in the range of some cm occur.              For this work especially the author's co-;worker
                                                                              K.-H. Mahrt has prepared..' a special arrangement.
                The sampling rate for these temperature sensors,              To this belonged a big pressure vessel for the
                depending on the number of simultaneously measuring           pressure range of 0 - 1000 bar. It has a volume
                parameters, increased up to 50 and 100 per second.            of about 80 litre and is sufficiently big enough
                Based on this, it was possible to reach a dis-                to enclose the complete C-T-D sonde. This pressure
                solving of depth for the temperature up to about              vessel is combined with a pressure balance. It was
                 10 cm in using the lowering velocity of the Kiel             shortly calibrated by our bureau of standards PTB
                C-T-D respectively multisonde device by the author            (Physik  techn. Bundesanstalt) on an accuracy-of
                of that time (see fig. 1).                                    5@1e-10    Besides, we have for the temperature
                                                                              calibrations and tests water triple point cells and
                In the course of realization of high speed                    a gallium cell for the temperature fix.point of
                measured parameters, the author succeeded in de-              29,77140C. In addition to that we have platin
                veloping in the years 1980-1982, a new and rela-              thermometers with an accuracy of 2 mK even shortly
                tively long conductivity cell of about 10 cm using            chequed by our bureau of standards. For chequing
                measuring speeds of about 1 msec for a spatial                the electric resistances we use an ASL Bridge and
                                           a
                                            T11   I
                                            sf%

                                                                        492

               an inductive resistance box. And for measurings                 feasibilities of a linearisation of the bridge
               of atmosperic pressure and comparisons we own a          big    circuits. He found several ways of which it could
               tank of sea water of 3,6 ml.                                    be done. For the new C-T-D sonde, the author has
                                                                               been chosen an electric circuit arrangement which
               For the calibration of the salinity respectively                was first represented on the "Ocean 85" and de-
               electric conductivity we use the autosal of guild-              scribed in the proceedings.[71
               line. For using the autosal the pressure vessel is
               arranged in such a way that it is possible to                   The linearisation of the above explained bridge
               take out water samplings under pressure, which                  were reached by splitting the measuring into three
               can be measured with the autosal at atmospheric                 steps. With the first step the sine signal voltage
               pressure.                                                       is led to the input on an A-D converter of about
                                                                               12 bit 181. It gives a rough value of the signal
               BRIEF    INFORMATIONS ABOUT THE.DEVELOPED ELECTRIC,             peak voltage in numeric numbers. This happens in
               ELECfRONIC CIRCUITS FOR MEASURING C, T AND D                    a very short time interval near the signal peak
                                                                               voltage in any half wave period of the sine. With
               Since all three measurands C, T and D by electric               the next step the numeric defined voltage is led
               measurements cause changings of the values of                   to the input of a D-A converter at the present
               electric resistances, the author has developed a                time of 18 bit. On this way it gets an exact known
               special A.C.resistance bridge. This bridge has                  value for the sine servo voltage on the output of
               been first deviced by the author 1972 161. This                 the D-A converter. This voltage appears temporary
               bridge works with three branches. (s. fig. 2) 171.              directly after the time point if the numeric num-
               Two of these 1, 2 are well known and general used               ber is produced. This takes still place in the
               in resistance bridges. Through this two branches                first half wave period of the sine. The exactness
               flows a constant sine current. This current pro-                of the sine servo voltage of the D-A converter
               duces a sine signal depending on the measured                   corresponds to 18 bit. Now the exact known value
               value between the two branches..This sine voltage               of the servo voltage in general is very less dif-
               can be understood as an algebraic vector. The                   ferent against the signal voltage from the bridge.
               third branch is connected with a constant cosine                Therefore to know its exact value the d    ' ifference
               current. This current produces at a fixed re-                   of these two sine voltages is produced in an adder
               sistance a constant cosine voltage. The addition                and than after a suitable amplification directly
               of the sine signal voltage and the cosine fixed                 measured respectively reproduced as a numeric
               voltage results a new and with the signal voltage               number about the above explained two phase bridge
               in its phase changeable vector. By this addition                in a range where the bridge should viorir linear til a re-
               a phaseshift is produced. From this changeable                  solution of �  I Isb for a range of 18 bit.
               phaseshift can be deduced a changeable time inter-                             7
               val which is counted out with a very high puls                  In the present time this bridge works with an A.C.
               frequency. By this procedure the described bridge               voltage of 500 cycle. Therefore the value of the
               transfers the measurands directly into a digit                  measured parameter will be received every two
               number. Therefore this bridge is also an A-D                    milliseconds. However the measuring of the dif-
               converter.                                                      ference voltage respectively its corresponding
                  i._ konslant und                                             time interval needs only a measuring time of
                  gegeben durch
                     i. sin d                                                  about 100-150 psec.

                                       C                                       THE RESULTS OF TESTS OF THE LINEARISED TWO PHASE
                  1   2       3                                                A-C BRIDGE
                                       R3     imm . !L,.Co s Wt                Since the described and explained bridge circuits
                             R211    + OP,                                     are an essential part for the quality of the new
                                                                               instrument. Therefore these circuits must be in-
                         R,                       R4                           vestigated and tested as well as the single sensors
                                                                               themselves. This test has been performed with great
                                                r,.R6
                                  Rx                                           under his guidance by working on his thesis. The
                                                                               carefulness by the authors student R. Duch5teau
                                                     Rr Rx + imm
                                             4             + @, -
                R
                  1_@'                                                         tests were started by connecting a very stable
                 .[ R.                                                         electric resistance to the input of the bridge.
               Figure 2.     This alternating current bridge has               By this arrangement at the output the value of the
                    three branches 1, 2 and 3. The branches 1 and              measurand in kind of numeric number appears. There-
               2 have the same source and a constant sine
               current.flowsthrough them. R is the changeable                  fore this numeric number corresponds to the size
               and R,gthe reference resistaAce. U is the out-                  of the input resistors. The values were written
               put s   nal. Through 3 flows a constafit cosine current.        down by using a magnetic tape from which later
               They.are vectorial added in OP      U is than a com-            the values were carried out. On this way the mag-
               plex output signal              3' 1                            netic tape contains all elementary measurings in
                                                                               time distances of 2 msec from which the value can
                                                                               be transferred to a graphic projection.
               However the dependence of the output signal from
               the input is non linear. The consequence is that                To,test the circuits we made many thousands elemen-
               the resolution is not the same for the whole range.             tary measurings with a fixed inductive resistance
               Therefore the author has thought about
                                       op,
                                                  R,

                                                  6
                                                @,R

                                                                         493

                            of high quality of the input of the circuit. With                                                                                                                         T
                            this arrangement the deviations of all 2 msec                                                           Calibration of the linearised two phase AC - Bridge with
                            measured values were noted on a graphic in de-                                                          Rosemount Pt-oceanographic thermometer with Rosemount
                            pendence of the time in sec.in fig. 3 on the                                                            Pt - standard thermometer.
                            ordinate. Hereby the chosen range was.devided in
                            18 bit. As the fig. shows there were no deviations
                            til one's of 2 400 data greater than �1 bit of
                            18 bit. The structure of the distribution of the                                                                Deviations from quadratic regression
                            deviations depending on the timedet expect, that
                            the measurings were,still something disturbed from
                            outside.                                                                                                                     resolution           precision
                                        Stability of the linearised two phase AC-bridge                                                                  0.12 mK                0.3 mK
                                lsb                                                                                                 A/mK    I                                                               presently
                              of 18                                                                                                  0.4-                       X                   X                       claimed
                                                                                                                                     0.2-                                                                   accuracy
                                                                                                                                     0          .10`X-X                                     so               2 mK
                                                                                                                                                                              Y 3@ t I -C
                                                                                                                                     0.2 -               1@    1; \iO X
                                                                                                                                    -0.4-.
                                                                                                                             Figure 5.       traceable to        PTB

                                                                                                                  11A        In fig. 5         is graphically represented the                        result of
                                  Elementary measurements every 2ms of a constant data, simulated with a high
                                  accuracy ratio transformer at room temperature ( 2400dato I                                a calibration of the linearised two phase bridge
                                                                                                                             with a Rosemount Fit oceanographic thermometer
                            Figure 3.            Elementary measurementc,every 2                         ms of               against a Rosemount standard thermometer. The
                            a constant data, stmulated with a high accuracy                                                  measurings cover the whole range between 0' and
                            ratio transformer at room temperature-(2 400 data)                                               300C. This graphic represents only the deviations
                                                                                                                             versus a quadratic regression curve because in such
                            In fig. 4 a, b, c are drawn the deviations from                                                  a way the result is better to demonstrate. These
                            the linearities of the used and linearisized two                                                 measuring has been done in our big seawater con-
                            phase A-C bridge of the author. These measurings                                                 tainer with a content of about 3.6 m". As the
                            are referred to an arrangement by which the                                                      graphic shows the result is �.3 mK for the preci-
                            sensor resistance at the input of the bridge has                                                 sion and .12 mK for the resolution.
                            been substituted by variable resistances of our
                            inductive resistance box. The measurings in                                                                     Differences 6weeks after repetition of calibration
                            fig. 4 a, b, c are done in a temperature con-
                            trolled container for fig. a at 100C, for b at
                            200C and for c at 300C. The result is that all
                            measurings stay in an interval of �2 bit of 18 bit.                                                             T
                            However it can be concluded that the values lie                                                                 AymK_
                            within a band with deviations of �1 bit of 18 bit.                                                                                                                       1mK
                            Besides, as measurings of the D-A converter have
                            shown this'band is the following on non linearities                                                      7.5.88
                            by this converter.
                                                 N-fl- f- time-ty f the I i me a,,&, t-1 ph... AC-b,idg,                                    2,0
                                                 a' diff-It t"Pelpl-1, 10.11.d t, .2 -C
                                                 11@b
                                                 23                                                                                 b
                                        30*c I-                                             r
                                                  I               V
                                                 -2 - - - - - - - - - - - - - - - - - - - - - - - - - - - -
                                                                                                                                            1,0

                                                 2- - - - - - - - - - - - - - - - - -
                                        20*C .1                                            b
                                                 I                                                                                   21.S.88
                                                 -2                                                                                              1   T
                                                 -3-a02       0,4      6      0.8       10                                                  0    -           5       10      f5     2'      Z5     3,l) T
                                                 It.b .18                                                                           Calibration                      A.                                     C
                                                 21                                                                                                   r
                                        lopc@                                             a

                                                 -2- . . . . . . . . . . .     . . . . . . .
                                                 -3-00,2     0,4      0,6     ps        10                                      Fig. 6a, b        measured in a shrred 3,6m3tank
                            Figure 4.            This figure          shows      a   g  raphic represen-                     In fig. 6 a, b two calibration curves are repre
                            tation of a          calibration          of the tested circuits                                 sented with the same arrangement as for fig. 5 be
                            in a at 100C, in b,at 200C and in c,at 300C                                                      Hereby fig. 6 b is referred to, dates which have
                                                                                                                             been measured six weeks laterthanthe calibration
                            room    temperature for the complete linearised                                                  dates in curve of fig. 6 a. The comparison of both
                            AC-bridge.
                                                                                                                             figures show a drift between the temperature

                                                                                                                     494

              values of about 2 mK. However hereby is to attend            However this cell has been further developed under
              that shifts in the temperature notification of Pt            the author guidance in connection with the thesis
              sensors could happen also by a push against it.              of the student E. Falkenhagen. The cell has eight
              Therefore it must not be a real drift.                       annular electrodes 1-8. The constant alternating
                                                                           current for measurings of the conductivity is led
              A measuring in the same tank by a fixed temperature          in the electrode 4 and flows,to the electrode 1. A
              produced the graphic in fig. 7. It shows separate-           flow of this current to the electrode 8 is blocked
              ly the results of elementary measurings over a               by a controled servo current which is flowing in
              time interval of .4 sec with a sampling rate of              the electrode from 7 to 8. On this kind the path
              500/sec. In this graphic the measured values                 over which the conductivity is measured only lies
              fluctuate to about �.5 mK. However this fluctua-             between the electrodes 2 and 3. Its distance is
              tion is caused very probably by the natural and              about 5 mm and in general the diameter of the tube
              real noise in such a big tank.                               9 about 16 mm. This cell is combined to a compact
                    The linearised two-phase AC-bridge with a Rosemount    sensor with thermic'sondes.       This cell has been
                     Pt oceanographic thermometer                          calibrated with the arrangement as explained above.
                                                                           That means the calibration is made with the
                                             26-_1mK                       linearised two phase bridge. For the cell Wormley
                                                                           water is used in a comparison with a autosal in-
              21,1120-                                                     strument. The result is displayed in fig. 9 by a
                                                                           temperature variation from DOG til 250C of the
               1mK
                                                                           Wormley water. The reached precision was �.001 in
                                                                           a A salinity, this means in deviations of a square
              21,1100-T                                                    regression line. For the resolution. could be found
                                                                 @s        .0005 in A S.
                  Elementary measurements every 2ms in a stirred 3,6m3tank    Calibration of the linearised two phase AC-Bridge with Wormley water
                                                                              and outosal salinometer
               Figure 7.                                                             Deviations from quadratic regression
                                                                            b s      resolu hon    precision
              INVESTIGATIONS AND TESTS I PF THE CONDUCTIVITY CELL          0,004-    0,0005       -0,001                     presently
                                                                                                                             claimed
                                                                                                                             accuracy
              As above mentioned for measurings of the conducti-           0,002-                                            tO,003
              vity it was used a special cell which has been de-              -                             42.902 Z
                                                                              0-
              viced by the author and is described in several                     0!6/  0,7    0
              publications 191. Therefore it should not be                 -0,002-               X-9         -.0
              necessary to repeat a description of this sensor
              in details. From this reason for this paper it               -0,W4-
              may be sufficient to show the construction in
              fig. 8 a, b.                                       9         Figure 9.
                                                                           A MERCURY PRESSURE SENSOR FOR MARINE RESEARCH

                                                                           1982 Wearn R. B and Larson
                                                                                                         N. G. 141 have made an
                                                                           investigation of the sensitivities and drift of
                                                                           pressure sensors which at present are commonly used
                                                      W
                                                                           in the marine research. For all scientist's who
                                                                           need pressure sensors, the work of Wearn and Larson
                                                                           is very instructive. By this work it can be con-
                                                                           cluded that these are many pressure sensors in the
                                                                    20     marine field, however it exist's no really suitable
                                            20                             sensor for purposes by which precision measurings
                                                                           are reached as required. Therefore the author has,
                                                                           tried to find out another fundamental idea to
                                          -710                             realize such a sensor. From this basic he thought
                                                                    mm
                                            MM 3 3,                        to use the pressure dependence of a liquid elec@-_
                                                                           tric resistance. Then a liquid electric resistance
                                            0  2,                          sensor cannot show any drift phenomenons. Therefore
                                                                           in respect of the well known electric properties of
                                                                           mercury, such a sensor could be a mercury filament.
                                                                           In a first approach the dependence of a mercury
                                                                           electric resistance on pressure R@jo by a variable
                                                                           P and a constant temperature T i         given by
                                                                                                          0
                                                                           R         R     (1+a     - AP)
                                                                           PoJ 0     PoJo      P,To
              Figure 8 a, b   Conductivity cell with 8 annular             respectively    ARPJ
              electrodes 1-8  in a quartz tube 9. Fig. 8 a demon-                              o     I     A P, OL
              ttrdtes in a cross-section drawing and b-in per-                             R                      P, T   wher3 a
              specti ve depiction                                                          PoJo       Pj0             0

                                                                     495

                               is the pressure coefficient at the temerature T                                                   o'                  But our measurings prove that up to a sufficient
                               A diagram for this dependence is to be seen in                                                                        approach these deviations can be corrected by a
                               fig. 10a curve (1) for an interval of 0 til 600 bar.                                                                  square function. By this reason it is possible to
                                      ARp                                                                                      R                     reach on the basic of the described mercury
                                      R                       2                                           6         OC
                                      P.                                           @4@                    i                    RTO                   resistance pressure sensor a precision at least til
                                                             0:2                   0,4                   0,6 *C                                      �1.5 m in the range of 0-600 bar. Because this work
                                                                                                                                                     could not be finished til this time a detailed
                                                                                                                                                     publication will follow very soon.
                                                                                                                    2
                                      60-                                                                                      -60                                         Tegrature edibrahm of i Ng4nortz dt&k mktance
                                                                                                                                                                                                                                                              At
                                      40-                                                                                                    Abe                                                                                                              mK
                                                                                                                               40              1621.          "1   Dwidiam of fto Unftr mVmionlirw                                                            .80
                                                                                                                                                                                                                             P,-2,063SO10                     -70
                                      20-                                                                                      20                                                                                                                             -60
                                                                                                      __3
                                      0-        -                                                                              0                                                                                                                              so
                                      _20-       160         2@O        3100       4'0 0      56        '600 P/b.,                                                                                                                                  width     '0
                                                                                                                                                                                                                                                              -30

                                                                                                                                                                                                                                                              zo

                                                                                                                                                                                                                                                              .10
                                      -60-                                                                                                                                                                                                 Regmsionstine      _0
                                                                                                                                                 -3-                                                                                                          10
                                      _80-

                                                                                                                                                                                                                                                              -30

                                                                                                                                                                                                                                                              -40
                                      120]                                                                                                        0 . . . . S'                10 . . . . i's              ia@            i5            30                     r'C
                               Figure 10 a, b.                       Diagram for the dependences                                             Fiftre 11.                         REFERENCES
                               AR     P                                                                      AR
                               __R__        10-4      of P in curve (1) and for                              R_     T .'       10-4          (1) a)Kroebel, W. German Pat. Nr. 29.10957 (1979)
                                      P0                                                                            T                                WEEE Journ. OC. Engeneering, Vol. OE-6, No.4,
                                                                                                                    0                                    118..124 (1981)
                               for T        = 6'C in curve (2).and                         for T            0,60C in                                 c)Kroebel, W. and v. Bosse, N. OCEANS V, IEEE
                               cu     Irve  (3).                                                                                                         Publ. No. 82-CH 1827-5, Washington D.C., USA,
                                                                                                                                                         272..276 (1982)
                               However,@ a mercury filament shows also a dependence (2)                                                              Kroebel, W. Hydrologische Untersuchungen mit der
                               of its electric resistance with the temperature.,                                                                     Kieler Multisonde im Bodensee. Publ. by
                               This dependence is represented in ajirst approach                                                                     Landesanstalt fOr Umweltschutz Baden-WOrttemberg,
                               in fig. 10b curve 2 and 3 for a temperature inter-                                                                    Karlsruhe (1980)
                               val from DOC til 61C in curve 2, respectively                                                                 (3)     Kroebel, W. and v. Bosse, N. OCEANS '82, IEEE
                               0-0,6*C in curve 3. In the fig. 10a is recorded in                                                                    Publ. No. 82-CH,1827-5, Figures 3-6, 273..274
                               the abszis the pressure P as well as in fig. iOb                                                              (4).Wearn, R.B., Larson, N.G. Measurements of sensi-
                               the temperature T versus the ordinate                                                ARP          4                   tivities and.drift of Digiquartz pressure sensor,
                                                                                                                    R          10                    Deep Sea Research Vol. 29, No IA, 111-134 (1982)
                                                          ,IRT                                                      P0                       (5)     Kroebel, W. OCEANS '87, IEEE Publ. No. 87-CH2498-4
                               respectively                                -4                                                                        Halifax, N.S., Canada, Vol.1, 331..334 (1987)/
                                                          R            10                                                                            Brown, N.L., OCEANS '87, IEEE Publ. No.
                                                            T 0                                                                                      87-CH 2498-4, Halifax, N.S. Vol.1, 335..340 (1987)
                               The magnitude of                   the ordinates                 is    the           same for both            (6)'a)        Kroebel, W. German Pat. Nr P220059 89 (1972)
                               abszisses. Therefore the diagrams                                      allow to compare                               b)    Kroebel, W. A frequency independent Two-Phases
                               the influence of the temperature on a pressure                                                                              AC-bridge for precision in situ Measurements
                               measuring. This comparison shows that it is impor-                                                                          of Physical Parameters in Sea Water,
                               tant to try to suppress the temperature influence                                                                           Interocean 1973, KongreBberichtswerk,
                               by a suitable pressure sensor device. A first de-                                                                           DOsseldorf,817..822 (1973)
                               vice which fulfills this conditions leads to the                                                              (7)     Kroebel, W. OCEANS '85, IEEE Publ. No. 85-CH-2250-9,
                               result of a deviation of about �1,5 m. For this re-                                                                   San Diego, USA, 610..615 (1985)
                               Isult has been arranged in a rugged block in one                                                              (8)     Kroebel, W.A.,new Generation of CTD-Probe for
                               borhole a pressure protected mercury filament and                                                                     in situ Measurements with high speed, Accuracy and
                               in another borhole of the same block near by a                                                                        sensitivity, Part 2, Marine Technology Vol. 18,
                               pressure unprotected similar mercury filament. The                                                                    149..154 (1987)
                               changeable temperature interval by a measuring                                                                (9)     a)Kroebel, W. German Patent No. 3238956 (1982)
                               between 0-600 bar has been about 2 K.                                                                                 b)see (8)

                               However, the deviations concerning the coefficient
                                      T,P0  from the linearity are shown in fig. 11.

                                                                                                                                         496

                                    FIELD PROVEN HIGH SPEED MICRO OPTICAL DENSITY PROFILER SAMPLING
                                               1000 TIMES PER SECOND WITH 10-6 PRECISION

                                                Karl-Heinz Mahrt and Christoph Waldmann

                                             Institute of Applied Physics, University of Kiel
                                                     Olshausenstrasse 40, 2300 Kiel 1
                                                            Fed.Rep.of Germany

                                    ABSTRACT                             vinced that the addition of high recision refrac-
                                                                         tive,index determinations.to simuTtaneously mea-
              We developed a miniature fibre optical point sea-          sured "first class" CTD- data should give new in-
              refractometer with industrial prototype status. It         sights into the dynamics of structures and distri-
              was designed to be used in high speed profiling            butions of water bodies. We really were led to
              applications, e.g. for quick survey of the density         think about a whole refractive index concept rather
              field of the ocean by directly measuring the index         than building just another new instrument./ I
              of refraction with extremely high precision of 10-6        / 2 /./ 12 /,/ 13 /.
              as it is required for fine description of the den-         At the M.I.T.- workshop on "Profilers of the Futu-
              sity distribution.                                         re" (WOCE- meeting) in Boston,August 1984,/ 3 / we
                                                                         reported under the topic "Is there anything new
              Thanks to the kind invitation by Albert Bradley            under the sun" on our-experience with refractive
              from Woods Hole Oceanographic Institution and,to           index measurements. It was there where we learnt
              his substantial and invaluable help,we were able           about details of A.Bradley's research work,on his
              to mount our sensor on his newly developed most            high performance deep sea instrument carrier "Fly-
              progressive high speed free falling deep sea in-           ing Fish" / 4 /, following an inspiring and very
              strument carrier "Flying Fish" who at the same,            courageous concept of high speed surveying of the
              time was furnished with the most recent Neil Brown         oceans as a large step forward to tackle the prob-
              Mark V CTD electronics.                                    lem of what Walter Munk called the "terrible under-
                                                                         sampling of the oceans" at the occasion of his talk
              Field data evaluation studies showed at the very           in the opening plenary session of last year's
              first glance: Index of refraction profiles are an          "Oceans'87" conference in Halifax,.N.S.,Canada./ 5
              extremely good representation of the actual densi-         We found it to be of mutual interest  .and benefit to
              ty distribution. Evaluation of all measuring data          come together,' -and so we did some "merge in"- re-
              turns out that there are significant correlation           search work with "Refractive Index",and "Flying
              anomalies between CTD- derived density data (using         Fish" that culm,inated in 1987/88. The crucial joint
              the equation of state EOS-80),and densities as.de-
              ternined from index of refraction measurements.
              These differences may well serve as a new parameter                 LSD               PMF
              for a much more detailed description of water
              bodies.                                                             TST

                               1. INTRODUCTION

                                                                                  6PD
              On June 26, 1984,from board of the research catama-                                         rb
              ran M/S"Haithabu" our sea going experimental labor-                       db
              atory, instrument delivered in situ in the Baltic
              Sea the first continuously measured absolute index
              of refraction profile, clearly demonstrating the
              good feasability of "first class" optical density                                        E
              measurements with unparalleled small measuring vol-
              ume, very high measuring speed, and very high pre-                  PR
                           6
              cision of 10 . This most important experience to-
              gether with the results of our intensive recherche
                                                                                        rb
              and study of all the old and recent related litera-                        0   11
              ture we could get, made us conclude that it would                   IRB
                                                                                    - Arb
              be a regrettable, limitting misunderstanding to                                                     lb
              consider refractive index measurements just to be                           lb
              another substitute for e.g. conductivity measure-
              ments to finally arrive at "conventional practical"        Fig.1: Measuring principle of the extrinsic fibre
              salinity and density data. Instead, we became con-                optical point sea- refractometer

                                                    CH258S-8/88/0000- 497 $1 @1988 IEEE

                  field experiment took place on WHOI R/V "Oceanus"                               4. INDEX REFERENCE STANDARD
                  195 cruise, Oct./Nov. 1987 / 6 /, when the refrac-
                  tive index sensor proved to be a high performance                     SCHOTT Optics Division, R&D Physical Optics,Mainz,
                  instrument.                                                           West- Germany supplied us with special K5- type
                                                                                        reference material with best chemical resistance
                                    2. OPTICAL PRINCIPLE                                properties with respect to the aggressive sea
                                                                                        water. From that raw material we had the index
                  To begin with, have a look at figure 1 showing the                    reference body shaped according to figure 2.
                  optical foundations of the instrument.                                                                          a
                  750 nm laser light from the single mode laser diode                                                            3 mm
                  LSD is launched into the polarization maintaining
                  fibre PMF which guides the light through a bulk
                  head into the sea water in such a way that it hits
                  as incident beam ib at nearly grazing angle the
                  index reference glass body IRB at it's glass / sea
                  water interface. The refracted beam rb re-enters
                  the pressure protected inner part of the vacuum
                  optical bench system and is lead on through the
                  magnifying projecting optics PRO and focused on
                  the silicon crystal surface of the posicon, serv-
                  ing as beam position detector BPD. The angular dis-                             0.8mm
                  placement of the deflected beam db is a function
                  of the refractive index n of the sea water.                           Fig.2: Favourable shape of the        sensor sting for
                                                                                                best hydrodynamical behaviour
                  In order to fulfil accuracy requirements the laser
                  diode and the posicon chip are kept on constant                       This standard material shows fairly low temperature
                  temperature by means of the common thermostat TST.                    and pressure coefficients:
                                      3. RESOLUTION                                                    An = - 2        jo-7    K
                  Center part of the point sea- refractometer is the                                   AT
                  index reference body IRB, a        standard material of                              An              10-8
                  best available quality with        refractive index N. As                          --ip   = + 4               dbar
                  we have vacuum at the inner        side of the optical
                  bench system, the following        relations hold:                    These numbers have to be used to simply correct for
                            siny = N sin 0 = N       sin ('cL - E                       temperature and pressure influences.
                          y = arc sin ( n cos F,           N2 - n2     sin c                            5. BEAM POSITION DETEKTOR
                                as sinCE = n / N.                                       The lateral-effect photo detector used for sensing
                                                                                        the position of the refracted and deflected beam
                  The sensitivity of the influence of n on             follows          has a sensitive-area of 1 x 3 mm2 and is a special
                  from differentiation:                                                 silicon chip made according to our requirements.As
                                                                                        relatively often @mall but not negligible crystal
                                                                   in F                 disturbances occur, all incomming chips had to un-
                                                     Cos E +     s                      dergoe a thorough check for crystal defects. For
                                dn      Cos Y                 NF(-N/n)'- 1              that purpose we developed a high precision inter-
                                                                                        ferometric length measuring machine in a well con-
                                                                       of . the         trolled environmental chamber to measure the beam
                  As we choose Y = 0 for the mean value no                              position output signal as a function of the light
                  total range of refractive index variation            in sea           spot position with the ultimate possible accuracy,
                  water, we arrive at:                                                  reaching the limits of noise. Spot size, light in-
                                                              i                         tensity, and some other parameters could be varied.
                           dn              Cos &        __ -                            The light spot position signal is continously mea-
                                 n=n                  @1 - (n/N)2                       sured while the spot moves along the mean axis of
                                 Y=00                                                   the crystal surface. Figure 3 shows the character-
                                                                                        istic of a passed crystal (solid line) in compari-
                  To get a numerical      idea about the sensitivity the                son with a rejected one due to obvious defects
                  following figures are given : For our standard ma-                    (dotted line).
                  terial of the index reference body we have
                   E = 62.060, and with the * imum requested re-                        The lower diagram in figure 3 shows the simultane-
                  so                                 m19
                     lvability of dn = 5 - 10- we get dy = 0.22"                        ously measured intensity signal UL to be almost
                  what corresponds with a slope of about 10 cm to                       independent on the beam position.
                  100 km !                                                                              6. EVALUATING ELECTRONICS
                  This should be strong argument that the stability
                  of the whole optical bench system in the full                         In order to improve the signal to noise ratio an
                  ?ceanographic range of pressures and temperatures                     AC- modulation technique has been used. The laser
                  is of paramount importance.

                                                                                    498

                     60                                                                                              7. SPECIFICATIONS
                  A                                                Center scan
                 d                                                 ZEISS Lurninar f=25mm       After the brief description of the main features
                                                                   Spot: 0.360..               of the instrument's measuring principle, the
                     30                                                                        main specifications are to follow now:

                                                                                               --- extremely small measuring volume: 0.1 pI
                                                                --------                       --- high measuring speed: 1000 samples per second
                                                                                               --- measuring wavelength: 750 nm
                                                                         B
                                                                                               --- measuring    range: 1.323 !!: n t 1.369
                   -30                                                                         --- precision:      10-6
                                                                                               --- accuracy:    +10-5 ( estimated with distilled
                                                                                                   water and -Felieved to be achievable for the
                                                                                                   whole range of measurement as soon as re-
                  -6                                                                               liable sea water data for 750 nm will become
                           -4060'      -2000              0          2000      1  40100            available )
                                                                            dX/8               --- over all length: 48 cm
                                                                      -                        ---max.diameter: 8 cm
                      4-                                          1                            --- weight in air: 5.5 kg
                    u,./v                                       Ointensity of                  --- max.working depth: 6000 m
                      2-                                             light     660n.           ---materials exposed to sea water: titanium,
                                                                                                   glass, neoprene

                                                                                               The industrial prototype instrument is depicted
                           -4000        -2000             0         2000 d  AIS   4000         in figure 5, and a close up photo in figure 6
                Fig.3:     Calibration functions of        posicons                            shows details of the rugged refractive index
                           A  good silicon crystal                                             sensor sting.
                           B  crystal defect
                           I   light intensity belonging to curve A                                      8. PRELIMINARY CALIBRATION
                           The curves illustrate the deviation from                        At present    time, refractive index data for a com-
                           linearity versus light spot position in                         plete calibration of sufficient quality are not
                           units Of d ),/8 . ( d X= 632.8 nm, He-Ne-                       available from the literature. Until we will have
                           laser wavelength of the length measuring             in-        finished our own laboratory interferometer for
                           terferometer                                                    750 nm index of refraction measurements of sea

                light is modulated with             kHz sinusoidal
                                                                                                                                                              r
                signal. The pre- amplified signals of PA1 and                                                    A B.P           S&H           X:
                PA2 in figure 4, which shows the basic con-                                                          Filter                            INTENSITY
                cept of the evaluating analog electronics,.                       PA1               PA                   COMP. 11"S I
                are led through band pass filters and then                     3s             L        I(L-5)                                              U,
                are peak- rectified by use of sample,and                              6S.1
                hold modules. The proper control signals for                                                                     O.S.                    POSITION
                the sample and hold circuitry are,generated                                              BPD
                by comparators as zero crossing detectors and                                                    B   B. p
                monostable multivibrators ( one shots O.S. )                                                         Fitter      S&H
                with suitably adjusted time constants T                 T                db
                Then the well established standard techAl?qug*                                                           COMP    US
                for analog computation of intensity UL and                                                                       '172  EVE: EvALuATiNG
                position     U+_is applied as e.g. described in                                                                                 ELECTRONICS
                  7                                                                                                              a S.          (ANALOG
                The over all electronics noise level is kept
                below a 30 nm position signal equivalent,
                thus being below 5 - 10-7 refractive index                                        PHOTO CURRENT             3, = )S+ J(L-S)
                equivalent.                                                                                                               s
                                                                                                                    and    3 = lo( 1     -7)     hotds
                                                                                                                     or    )(L-Sf 30(     LLS       respect,
                                                                                                 INTENSITY INDEPENDENT POSITION SIGNAL:
                                Fig.4: Basic concept of the AC- measuring photo-                               IS -)(L-S) =I - 2 S
                                         electronics and beam position detection                               )S +](L-S)                L
                                                                                                       3(L
                                                                                        S-1

                                                                                                         B

                                                                                     499

                                                                               Fig.6: Refractive index  sensor sting

                                                                                       --------------
                                                                                      C,T-sensors!

                                                                                                       -------- - -- - -
                                                                                        --- -------

                                                                                                             48*

                                                                                                                    C,T- sensors

                                                                                        1.64.

                                                                                                 0.65.
                                                                                   2.                             TS_
                  EF12,L Industrial prototype of fibre optical
                         point sea- refractometer                                                                        -C
                                                                                                                   TF
                  water, we have to put up with the 400 ... 700 nm data
                  compiled by Austin and Haliks / 8 / and extrapolate
                  them for 750 nm. As these data remain very doubtful                   --- J__
                  we use them only as fixed check points against which
                  to observe drifts, etc.                                             n-sensor
                  ( Note: It is not important to know the accurate
                  values in the context of this paper

                                                                                                                        .em
                         9. FIRST HIGH SPEED PROFILING TEST                                                       Tf
                  In order to best demonstrate the capabilities of                                                            C
                  our refractive index sensor we were looking for the
                  best test facilities available today, and these              Fig.7: "Flying Fish" for surface to bottom high
                  were found at Woods Hole Oceanographic Institution:                 speed density profiling
                  A.Bradley's "Flying Fish" / 4 / well equiped with
                  most recent Neil Brown Mark V CTD- electronics / 9           The-upper right hand picture represents an axial
                  and Mark III CTD- sensors. Figure 7 shows the                rear view and illustrates the relative angular po-
                  "Flying Fish" together with the arrangement of sen-          sition of n- and C,T- sensors.At the middle right
                  sors.                                                        Is a drawing of the Mark III CTD- sensor cluster
                                                                               with    Ts   Slow Rosemount Pt-thermometer,
                  In order to properly accomodate the optical experi-                  TF   Fast thermistor bead thermometer,
                  ment, a special mid section with two "short wing                    :C    Ceramic conductivity cell.
                  tanks" had to be built. The left tank holds the
                  refractive index sensor, while the other tank con-
                  tains units of power supply and solid state memory           At the lower right: Location of   thermistor bead
                                                                                                           @48-'

                                                                                                                           C

                  for refractive index sensor operation and data               relative to the conductivity cell.
                  logging.

                                                                          500

                How the optical sensor fits into it's short wing                                   _@o          An/,Cj. 6P      120
                tank can be seen from the cross section drawing in
                figure 8.                                                                    0

                                                                                            300--
                                                                                                         An
                            EVE

                                                    MOD
                            LS                      TST
                                                                                            500-
                            BPD-_                   PA2

                            PA1__                   SLB

                                                                                            700
                            VO8
                                                    10cm

                              PRO
                                                                                          %dbar
                              PM                  IRS                                       900-

                                                                                                   10                      i/.C 20
                Fig.8: Compact arrangement of the components of                   Fig.9: Optical   density   profile. 190 000 refractive
                        the refractive index sensor                                       index data taken in less than 200 seconds.
                The abbreviations stand for:                                              "Flying  Fish" drop #4, Nov.11,1987
                                                                                            X= 55023.7'W,     (P= 37049.8'N
                        EVE:   Evaluating electronics
                        MOD:   10 kHz modulator                                   Now, if we subtract the very low frequency part of
                        LSD:   Laser diode                                        the An- profile in figure 9 from the an- profile
                        TST:   Thermostat                                         itself and express the refractive index differences
                        BPD:   Beam position detector                             in equivalent density differences APn, we get the
                        PA1:   Pre- amplifier channel     I                       spiking- free profile in the third column of figure
                        PA2:   Pre- amplifier channel     2                       10. Taking the CTD- data, we calculate the PEOS 80
                        SLB:   Stream lined body                                  density profile / 10 / and subtract in the same way
                        VOB:   Vacuum optical bank                                it's very low frequency part to get the I&PEOS 80
                        PRO:   Projecting optics                                  profile in the first column of figure 10, referring
                        PMF:   Polarization maintaining fibre                     to the use of the slow Rosemount Pt- thermometer
                        IRB:   Index reference body                               data. In case we were using the fast thermistor
                                                                                  bead data, we got the curve in column 2. The last
                The  first high speed field test took place on WHOI               column in,figure 10 depicts the result of the same
                R/V  "Oceanus" cruise 195, Oct.27 - Nov.15, 1987                  procedure applied to PSS 78 salinity calculation
                / 6  /. The refractive index sensor was put in for                / 11 / and expression of salinity differences in'
                the  very first time at "Flying Fish" drop #4 on                  terms of equivalent density differences.
                Nov.11,1987 and produced the first refractive index
                profile together with CTD- data as shown in figure                Comparing these results, we learn that the refrac-
                9 . On the extremely smooth ride down with 4.6.m/s                tive index measurements perfectly resolve the
                all data were taken within roughly 200 seconds,                   density structures. This is also.obvious from fi-
                about 1000 refractive index values and 40 CTD data                gure 11 illustrating the directly measured profiles
                sets every second.                                                of a thin layer in the pycnocline. Here every
                                                                                  measuring point of refractive index and CTD data is
                The graph in figure 9 demonstrates at first glance                printed out. From looking at the curves one might
                the refractive index profile to be an extremely                   be tempted to deviate towards the discussion of
                good estimator for density as suggested by the                    sophisticated anti- spiking algorithms and proce-
                Lorenz-Lorentz equation. Today, there is no other                 dures, instead of this one should rather realize
                in situ measuring single sensor with such a close                 and think about the advantages rising from the
                approximation of the searched density profile.                    fact, that the optical density profile is a direct

                                                                             501

                                                                                                                                 APn /Ib to-'                              NEW 80      10-5
                                      A                                     A                                     -4          0           4 -8                          0           4
                                      *,r,                                                          0-
                                      EM-3465 JL
                                                  CM.4W CAM-3-11" EgM-340'

                              100-1

                                                                                                     5-
                              300                     L
                                                                    .7                                                                                                                          -120

                                                                                                      -2                                                                                           P
                                                                                                                                                                                                   /dbar
                                                                                                    to-
                                            T           TF                                                                                                                                      -125
                                              9

                                                                                                        3
                              700-                                                                    1

                                                                                                    Fig.12:       Deviations-from the mean density profile, observed
                                                                                                                  in the pycnocline with refractive index measure-
                            %bar'                                                                                 ments on the one hand and with CTD- measurements
                                                                                                                  on the other hand.
                              900                                                                                 "Flying Fish" drop #4

                                                                                                                  high speed single sensor result as compared to the
                      Fig.10:         Registrated "density             roughness".Third                           indirect multi sensor                  PE?S 8? - profile.
                                      column depicts spiking- free optical density                                Figure 12 is another examp e o the excellent reso-
                                      measurement.                                                                lution of the density field in the pycnocline by
                                                                                                                  means of refractive index measurements. To traverse
                                      TS    calculated profile basing on slow                                     the 14 m layer the "Flying Fish" needed some 3 sec-
                                            Pt- thermometer data                                                  onds. The region between the dotted lines is the
                                      TF    dto.,basing on fast thermistor data                                   same thin layer as regarded in figure 11. However,
                                                                                                                  this time the curves are difference plots of the
                                      "Flying Fish" drop #4                                                       same kind as in figure 10 in order to get a distinct
                                                                                                                  resolution for the comparison of the original data.
                                                                                                                                                                   P/.JL
                                                                         0           1         2         3     0' 4                              1.02585                         1.02690

                                                                                                                                                                                                   120

                                                                           0.2       ............ . .

                                                                                                                                                                                                   -121
                                                                           .OA                      An                  T@F                          C
                       Fig.11: Optical sensing Of                       2-
                                      the fine density
                                      structure in a                                                                                                                                               P/dbar
                                      thin layer of the                                                                                                                                            -122
                                      pycnocline                    AZ/,'
                             "Flying Fish" drop #4                         -0.6
                                                                                                   21.9                           22.0               T/9C         22.1
                                                                        3
                                                                                                                             na                              61.9              %S              sio
                                                                                                                                                                                  CM

                                                                                                              502

                                                                                                               Ap/-VO-5
                        -32     -16      0       16      32                          -32     -16      0       16      32
                  100-                                                          400-

                                NN

                  300-                                                         Soo---

                                                                                                        DO
                  Soo-                                                          Soo-

                  700-                                                         1000-                    f

                                                                               P/dbar
                  Pldbar-

                  900--                                                        1200-

                                                                                   1             1.5             2
                    -1               0        AO/10-3 I                                                              An/10-3
               Fig.13: A   An curve                                        Fig.14: Same as  figure 13, but refering to another
                       B   CTD- derived P[Oj 80 curve,    adjusted                 water body, measured on location:
                       in such a way that o h curves have common                   "Flying Fish" drop #5, Nov.14,1987
                       profile end points.                                               6702.7'W,    @D= 4007.5'N
                       C : Differences A-B, expressed in units of
                       density equivalents.                                                   10. ANOMALIES
                       "Flying Fish" drop #4                               If one compares the density plots derived from op-
                                                                           tical refractive index data with those calculated
                                                                           from electrical CTD- measurements, as it is done in
                                                                           figures 13 and 14, one discovers characteristical
                                                                           differences due to the variability of the composit-
                                                                           ion of sea water. ( Note: An- plots in figures 13,
                                                                           14 refer to the exclusive use of the linear part of
                                                                           the refractive index calibration function. The true
                                                                           density differences are somewhat smaller and will
                                                         500
                                                                           be published elsewhere ). These differences are
                                                                           small and normally concern only the 5th and 6th de-
                                                                           cimal place, but they may well serve for more de-
                                  5
                                    j__                                    tailed studies of water bodies, as has been sug-
                                                         400               gested by by Bein,Hirsekorn,and MbIler / 14
                                   t 0
                            GO           *4                                E.g. they determined difference contours as repro-
                                  Se                                       duced from / 14 / in figure 16, illustrating a sect-
                                                                           ion through the Danmark Strait between Iceland and
                                                k
                                                         30*               Greenland. The West to East variation of the com-
                                                                           position of sea water is as well seen as the pro-
                          70o       60'       so.                          nounced indention of the Irminger and East-Green-
                                                                           land currents.
              Fig.15: Stations locations of drops #4, #5.                                     11. CONCLUSIONS
                       MarKed on surface currents map taken
                       from.Dietrich and Ulrich     15                     The advent of new  optical techniques and components
                                                                                      diode
                                                                           like laser       s, fibres,  silicon chips, etc. make
                                                                           us believe, that the concept of refractive index

                                                                      503

              measurement of sea water is a "hundred years old              5/Munk,W.: "Remote sensing/ contact oceanography"
              good idea whoe's time has come". This is partcular-                  talk in plenary session:"The Ocean frontier
              ly true with respect to high precision and high                      in 1990"
              speed measurements."First class" n,C,T,D- instru-                    OCEANS187 conference,Halifax N.S.,Canada
              ments on high performance vehicles are a powerful                    Sept.28- Oct.i, (1987)
              new oceans research tool.
              0.     69 70 71 68   67               5          3 62       /6 /Bradley,A.M.: "Fast hydrographic profiler"
                                                                                   in cruise report R/V "Oceanus" 195
                                                                                   WHOI, Oct.27- Nov.15, (1987)

                                                                          /7 /Kelly,B.O.,and Nemhauser,R.I.:"Techniques for
                                                                                   using the position sensitivity of silicon
                                                                                   photodetectors toprovide remote machine
              100@
                   Profil                                                          control"
                                                                                   21 st Annual IEEE Machine Tool Conference,
              15Wr                                      Profil Ya      -1500       Hartford, Conn.,USA, (oct.1973)
                                                                            8/Austin,R.W., and Halikas,G.: "The index of re-
                                                                       12M         fraction of sea water",
                                                                                                           -1,SCRIPPS Inst.of
                                                 5                                 Tech.Rep. SIO Ref.No. 76
                                                                                   Oceanography, La Jolla, CA 92093,(Jan.1976)
              2500L____
                                  31-   J21
                                         Abb. 24.                           9 /Brown.N.L.: "New generation CTD sensor system",
                                                                                   OCEANS'87,IEEE Publ.No.87 CH 2498-4,01.1,
              Fig.16: Contours of   differences  between chlorinity                Halifax,N.S.,Canada, 280 ... 286,(1987)
                        determined density P17   5(CI) and refrac-
                        tive index determined d6nsity P17.50),           /10 /Fofonoff,N.P. and Millard,R.C.:"Algorithms for
                        reproduced from / 14/.(numbers are in 10-6)                computation of fundamental properties of
                               12. ACKNOWLEDGEMENTS                                sea water"
                                                                                   UNESCO techn.papers in marine science
              The authors wish to express their deep appreciation                  No.44, (1983)
              for Dr.Albert Bradley's,WHOI, most friendly invi-
              tation to use his "Flying Fish" and facilities,and         /11 /UNESCO: "Background papers and supporting data
              for his substantial help in preparing for the field                  on the Practical Salinity scale 1978"
              work.                                                                UNESCO techn.papers in marine science
              We greatfully acknowledge Dr.N.Neuroth and W&Jochs                   No.37, (1981)
              from SCHOTT-Glass,Mainz, for donating some high
              quality glass samples to this project.                     /12   Mahrt,K.-H.,and Kroebel,W.: "Quantitative per-
              We would like to thank the German Research Society                   formance data of a new automatic optical
              (DFG) for financial support.                                         bench salinometer/ densitometer"
                                                                                   OCEANS185, IEEE Publ.No.85 CH 2250-9,
                                 13. REFERENCES                                    San Diego,CA,USA,622 ... 627,(1985)
                    Mahrt,K.-H.,Waldmann,H.C.and Kroebel,W.:                13  Mahrt,K.-H.: "Neue Methoden zur Pr6zisions-
                        "A newly developed in situ-measuring ocean-                messung des optischen Brechungsindex von
                        ographical probe sensing the optical index                 Seewasser in situ im Ozean und im Labor
                        of refraction of sea water with new aspects                dargestellt an erhaltenen MeBresultaten"
                        of salinity and density determinations"                    Verhandlungen d.Deutschen Physikal.Ges.,
                        OCEANS'82,IEEE Publ.No.82 CH 1827-5,                       51.Physikertagung, Vol.5,ME-4,Berlin(1987)
                        Washington,DC,USA,266, ... 271,(1982)              14/ Bein,W.,Hirsekorn,H.G.,M61let,L.: "Konstan-
                 2 /Mahrt,K.-H.,and Kroebel,W.:"Optical interfero-                 tenbestimmung des Meerwassers und Ergeb-
                        metric bench salinometer of high precision                 nisse Uber Wasserk6rper"
                        with electronical read out"                                Ver6ff.d.Inst.f.Meereskunde,Univers.Berlin
                        OCEANS'84,IEEE Publ.No.84 CH 2066-9,                       Neue Folge A,Heft 28, 240 S.,(Nov..1935)
                        Washington,DC,USA,219 ... Z23,(1984)             /15    Dietrich,G.und Ulrich,J.: "Atlas zur Ozeano-
                 3 /Heinmiller,R.H.: Report:"Profilers of the fu-                  graphie".
                        ture" Meeting (WOCE),Earth Sciences Bldg.,                 Bibliogr.Institut Mannheim,S.45, (1968)
                        Massachusetts Institute of Technology,
                        Cambridge,MA,USA,Aug.8-9,(1984)

                 4 /Bradley,A.M.: "High performance free-fall pro-
                        filing vehicles"
                        Marine Tech.Soc.Journ.21,33 ... 41,(1987)

                                                                      504

                                                              MULTI-SAMPLE PARTICLE FLUX COLLECTOR

                                                                                     STAFF*

                                                                            Oregon State University
                                                                           College of Oceanography
                                                                       Oceanography Admin. Bldg. 104
                                                                          Corvallis, OR 97331-5503

                                            ABSTRACT                                        4)   Sufficient 0.50 square meter collecting area to provide
                                                                                              -  gram-sized samples for multiple analyses
                 A non-metallic, conical fiberglass sediment trap has been                  5)   In situ sample poisoning and preservation
                 designed by personnel at Oregon State University to collect                6)   Fifteen modular sample cups which can be opened and
                 uncontaminated, preconcentrated samples compatible with                         closed in situ
                 trace element analytical requirements. The sediment trap has a             7)   Isolation of each individually sealed sample from contam-
                 0.5-m2 collecting area and a 15-multiple sample cup mechan-                     ination or loss during deployment and recovery, and
                 ism to allow the sediment trap to collect gram-size monthly                8)   Removal of sealed sample from the sediment trap without
                 samples during a typical year-long deployment and to isolate                    exposure to atmospheric contamination.
                 them until recovery.                                                                       MULTI-SAMPLE PARTICLE
                 The sample acquisition timing is controlled by a programmable                            COLLECTING SEDIMENT TRAP
                 CMOS microprocessor for variable sampling intervals from 32
                 seconds to tens of months. In addition, the microprocessor                 The design concept of the sediment trap is based upon facilita-
                 stores a permanent event record of trap performance.                       ting clean sample transferral and trap deployment. Sealed sam-
                                                                                            ple cups can be removed and archived individually without ex-
                 Particular emphasis has been directed at keeping the           trap        ternal shipboard contamination. The modularity of the sedi-
                 modular for ease of sample handling and trap manufacturing.
                 Components of the trap are compatible for moorings to 6000
                 meters depth.
                                                                                                                         0    im
                                        INTRODUCTION                                                                                           nylon braid
                                                                                                                                            mooring lines
                 In recent years (1,2,3), particle collectors have been used in-                                          llei@ 'A.
                 creasingly in the marine environment to investigate the com-
                                                                                                                         A
                 plex cycles of marine sedimentation from surface production                                          `.11
                 and mid-water transformation, to eventual burial, diagenesis,
                                                                                                                      @ F.,                  hexcel baffle
                                                                                                         "@upw@
                 and resuspension at the ocean floor. In order to fully under-
                 stand the complex, rapid changes in oceanic productivity and
                 sedimentation, it will be necessary to collect samples on a
                                                                                                                               K-111
                 monthly or bi-weekly basis over the course of several years.                                                    A,
                                                                                                        PkJll,!WV@,l                             fiberglass
                                                                                                                               E, ", E
                 In addition, increasing interest in trace element chemistry of the
                                                                                                                                ti         collector funnel
                 oceans makes it extremely important that samples remain un-                                     @k4
                 contaminated during typical year-long deployments.

                 The following description is for a particle collecting sediment
                 trap designed to address these rigorous sampling criteria. The
                 trap incorporates the following features:                                                                                   funnel outlet
                                                                                                                                              and coupler
                           -metallic construction materials compatible with trace
                 1)   Non
                      element analytical requirements
                 2)   Conical shape for preconcentration of sample and ease of
                                                                                                                                              multi-sample
                      processing
                                                                                                                                         carousel assembly
                 3)   An accurate and reproducible trapping efficiency under
                      normal oceanic current environments

                      Contributions by:
                      Dr. Roderick Mesecar, Head
                      Technical Planning & Development Group
                      Chris Moser, Research Assistant
                      Marine Geology                                                          Figure 1. Multi-sample sediment trap assembly

                                                               CH2585-8/88/0000- 505 $1 @1988 IEEE

                       ment trap design also allows removal of the sample changing
                       mechanism for servicing in a clean, trace element laboratory.                              anodized 6061 T6
                                                                                                                  aluminum
                       The multiple sediment trap, shown in Figure 1, consists of                                 pressure case
                       three subsystems: (1) a conical fiberglass collector with                                                                            feeder funnel
                       honeycomb baffle; (2) a multiple 15 sample collection mechan-
                       ism controlled by a programmable timer; and (3) a non-metallic
                       nylon rope harness for flotation and mooring attachment.                                                                                              compression fit
                                                FIBERGLASS CONE                                                                                                              o-ring seal

                       The fiberglass sediment trap cone has a 0.50 square meter col-
                       lecting area and was modelled after a design from Soutar et al.
                       (4). The diameter of the trap mouth is 80 cm., that of the low-
                       er opening is 7.5 cm., and the height is 160 cm., giving the
                       cone a 2:1 height/diameter aspect ratio for maximum trapping
                       efficiency. The trap mouth is covered by a polyester resin,
                       honeycomb baffle with 1-cm. diameter cells that are 5 cm.
                       thick which creates an entrapped water boundary at the mouth
                       of the sediment trap to reduce internal eddies. A horizontal lip
                       extends 5 cm. beyond the edge of the baffle to help deflect cur-                           eccentric
                       rent eddies downward and reduce the turbulence in current                                  motor drive
                       flow over the trap mouth. The walls of the cone slope only                                 crankshaft and
                       14* from vertical and are coated with an extremely smooth,                                 sliding actuator
                       clear acrylic resin to allow trapped material to fall rapidly to the                       mechanism
                       multiple sample collector.                                                                 vertically compensating
                             MULTIPLE SAMPLE COLLECT10N MECHANISM                                                 sleeve with Teflon o-ring
                                                                                                                  wedgej@daped.th
                       A mating flange on the fiberglass cone bolts to a lower multi-                             valve dy wt
                                                                                                                  sliding gate
                       sample collector assembly which can be removed and serviced

                                                        fiberglass carousel
                                                        unit support frame                                        Lexan polycarbonate
                                                                                                                  sample tube
                                                                              microprocessor/timer
                         shaft and torque stop                                mountm*g cage
                         for torsional spring

                                                                                                                  removeable end cap

                                                                                                                   Figure 3. Schematic drawing of the Collector assembly
                                  "@Ojl
                                                                                                                                  components.

                                                                                                                  independently in the laboratory (Fig. 2). This assembly con-
                                                                                                                  sists of a feeder funnel and rotating sample carousel plate with
                                                                                                                  fifteen independently sealable sample tubes; a pressure housing
                                                                                                                  that contains a microprocessor based timer unit, high-torque
                                                                                                                  motor and batteries; and an actuator alignment mechanism that
                                                                                                                  opens and closes each sample tube as it sequentially rotates
                                            @V                                                                    into precise alignment beneath the feeder funnel aperture.

                                                                                                                  The essential collector assembly components are shown sche-
                                                                                                                  matically in Figure 3. The collector assembly mates to the
                                                                                                                  fiberglass cone through a feeder funnel with a vertically com-
                                                                              ON                                  pensating, telescoping tube faced with a teflon coated silicone
                                                                                                                  rubber O-ring which seals tightly against each of the fifteen,
                                                                                                                  wedge-shaped sample tubes. Each sample tube is capped by a
                                                                                                                  unique sliding gate valve sealed with a teflon-coated silicone
                                                                                                                  rubber O-ring. This configuration allows every sample tube to
                                                                              carousel sample plate for           be loaded and removed from the sediment trap without being
                         one of three carousel plate                          fifteen sample tubes                opened. The collected sample is only open in situ to prevent
                         roller bearing supports                                                                  any contamination from the ambient seawater or the atmos-
                                                                                                                                                                             ._r
                                                                                                                                                                                 p
                                                                                                                                                                                in
                                                                                                                                                                                   es
                                                                                                                                                                                    a
                                                                                                                                                                                     s
                                                                                                                    @su@u
                                                                                                                        emc a, @e

                                                                                                                  phere until analysis in the laboratory. All feeder funnel, valve,
                                                        carousel torsional                                        and sample tube components are constructed of LEXAN poly-
                                                        spring assembly                                           carbonate plastic to prevent leachable trace metal contamina-
                                                                                                                  tion. Polycarbonate also withstands extremely rough handling
                                       Figure 2. Sample tube carousel assembly                                    at cold temperatures without breakage.

                                                                                                         506

                     Oregon State University personnel laboratory experiments                                 BASIC to open each sample tube for variable intervals from 32
                     have shown that upwards of 30% of the total dissolved sample                             seconds to many months or more, if needed. The micropro-
                     fraction can be lost from even a 20 cm. long sample tube over                            cessor also keeps an independent history of motor jog events
                     a two week period. This soluble fraction can amount to a sig-                            utilizing a backup lithium battery in the event of main battery
                     nificant portion of the total flux of some sample components.                            failure.
                     Therefore, each individually valved sample tube is 3.8 cm.
                     I.D. and 44 cm. long and is filled with 500 ml of a dense anti-                          ne trap is deployed with a sample valve open under the feeder
                     bacterial sodium azide brine. This long, narrow sample tube                              funnel which constitutes position #1 in the sampling sequence
                     design minimizes any loss of soluble sample fractions from the                           as shown in Figure 5. Under command from the microproces-
                     stable brine while the tube is open and collecting.                                      sor, the motor begins turning and the crankshaft pushes the
                                                                                                              valve pin forward to begin closing the valve. This also moves
                     The 15 sample tubes are bolted to a carousel plate that rotates                          the pin against a sloping ramp channel that breaks any sticktion
                     on three non-metallic bearing supports and relies on a linear,                           and allows the sample valve and sample carousel to rotate out
                     torsional spring to directly rotate the sample tubes into posi-                          from under the feeder funnel to position #2. Here the sample
                     tion. This high-tension spring is an integral part of the carou-                         valve pin escapes the actuator mechanism and the carousel ro-
                     sel mechanism (Fig. 4) and is located on the carousel axis in a                          tates freely powered by the torsional spring until the next valve
                     sealed, pressure compensating chamber filled with water-solu-                            pin enters the actuator at position #3. This second valve is
                     ble lubricant to protect it from corrosion. The spring applies a                         closed when it enters, and, as the crankshaft continues to
                     continuous torque which can be adjusted simply by how many                               rotate, the actuator pulls the valve pin back and the valve opens
                     turns the spring is loaded before deployment. The motion of                              through another sloping ramp channel which guides the new
                     the spring-loaded carousel sample plate is regulated by a sam-                           sample tube into registration under the feeder funnel back to
                     ple actuator mechanism and microprocessor timer that deter-                              position #1 where the motor rotation stops. The second sam-
                     mine how long each sample tube is open and collecting mater-                             ple tube is now open and ready to receive sample material for
                     ial.                                                                                     its preset period.

                                                      carousel shaft
                                                                                                                                                                       sample tube under
                                                                          sample tube valve body                                                                            feeder funnel
                                                                          with sliding gate
                     sample carousel plate                                                                                 0                  0                 0
                                                                             Z"I'MIMM131M,

                                                                                                                           0                  0                 0                  0

                                                                                                              corresponding
                                                                                                              motor shaft                                                represents path
                                                                                                              positions                                                     of valve pin

                                                                                                                           Figure 5. Sample valve actuator mechanism
                                                                                                                                       operating sequence

                                                                                                                       NYLON NON-METALLIC ROPE HARNESS
                     carousel torsional                                             sample tube
                     spring housing                                                                           During a typical oceanic deployment, each sediment trap is
                                                    location of spring                                        suspended within a completely, non-metallic, nylon rope
                                                    assembly pressure                                         harness (Fig. 1) for easy coupling into any mooring design.
                                                 compensation diaphram                                        Since each trap is usually deployed in a mooring below glass
                               Figure 4. Carousel sample holder assembly                                      flotation on galvanized chain, the harness is designed to keep
                                                                                                              any source of metal contamination at least 50 meters above the
                                                                                                              trap mouth. To further reduce potential metal contamination,
                               MICROPROCESSOR TIMER AND MOTOR                                                 the traps have also been deployed with PVC plastic radio
                                                                                                              buoys, nylon flotation harnesses, and type 316 stainless steel
                     The motor, microprocessor timer, and batteries are enclosed in                           shackles to eliminate corrosion and galvanized metal compon-
                     an anodized 6061 - T6 aluminum pressure case tested to                                   ents. The harness and trap have been successfully tested to
                     10,000 psi. The high torque, gear-reduction motor engages an                             3600 Kg working load with failure occurring at 6300 Kg
                     eccentric drive and crankshaft to power the sample valve actua-                          tension. The trap weighs 54 Kg in air (22.5 Kg in water) and
                                                                                                             00

                     tor and sample changing mechanism. The low power-drain,                                  can easily be deployed and recovered with typical shipboard
                     CMOS microprocessor can be programmed in user-friendly                                   facilities.

                                                                                                      50.7

                                              SUMMARY

                     In order to monitor the, increasingly complex changes in ocean-
                     ic productivity and sedimentation, we have designed a new
                     multi-sample particle flux trap which can collect and preserve
                     15 individually seated samples during a typical year-long
                     deployment. The non-metallic fiberglass and LEXAN poly-
                     carbonate plastic construction materials and type 316 stainless
                     steel hardware are compatible with trace element analytical
                     requirements. Individual samples can be removed from the
                     trap without exposure to atmospheric contamination. A micro-
                     processor controlled sample changer can be programmed for
                     an unlimited variety of sampling rates while storing a perman-
                     ent historical event record of trap performance. These sedi-
                     ment traps can be deployed to 2700 Kg meters depth and under
                     tension loads up to 3600 Kg.

                     Three of these sediment traps are currently moored at 1500
                     meters depth on three moorings off the Oregon coast and are
                     due to be recovered in late September 1988.

                                            REFERENCES

                     1.Spencer, D.W. The sediment trap intercomparison experi-
                       ment. Some preliminary data. In: R.F. Anderson and M.
                       P. Bacon, eds., Sediment Trap Intercomparison Experi-
                        ment, Woods Role Oceanographic Institution Technical
                        Memorandum WH0I-1-181,1981, p. 57-104.

                     2. Asper, V.L. A review of sediment trap technique. Marine
                        Technology Society Journal 21, 1987, 18-25.

                     3. Honjo, S. and K.W. Doherty. Large aperture time-series
                        sediment traps: design objectives, construction and appli-
                        cation, Deep-Sea Research 35, 1988, 133-149.

                     4. Soutar, A., S.A. Kling, P.A. Crill, E. Duffrin and K.W.
                        Bruland. Monitoring the marine environment through
                        sedimentation. Nature 266, 1977, 136-139.

                                                            508

                                         MULTI-SENSOR REAL-TIME DATA ACQUISITION AND PREPROCESSING AT SEA

                                                                        J. M. Moore, J. S. Charters and C. de Moustier

                                                                              Scripps Institution of Oceanography
                                                                              University of California, San Diego
                                                                                   La Jolla, California, 92093

                                                 ABSTRACT                                           second, or "offline" system, is available for data processing, software
                         This paper describes the real-time underway data acquisition               development, general use (word processing, correspondence, etc.)
                   system developed by the Shipboard Computer Group of the Scripps                  and as a backup for the "online" computer. Both machines run under
                   Institution of Oceanography in support of seagoing research. Since               the Berkeley UNIX (BSD 4.3) operating system, supporting applica-
                   February 1984, this system has been implemented on a DEC VAX-                    tion software written in C, FORTRAN-77 and UNIX shell script pro-
                   11/730 computer which runs the UNIX operating system and com-                    gramming languages.
                   municates with various sensors through an IEEE488 General Pur-                        The following peripheral devices are supported by each sys-
                   pose Interface Bus and slave microprocessors. The sensors inter-                 tem:
                   faced in this fashion acquire navigation data (i.e. ship's heading,              - Two Fujitsu 160 megabyte Winchester disk drives, interfaced
                   speed and position) and geophysical data (gravity, magnetics, Sea                through an Emulex Unibus controller. On the R/V T Washington
                   Beam bathymetry and expendable bathythermograph profiles). After                 each system also includes a Fujitsu 300 megabyte Winchester disk
                   a brief overview of the hardware involved, the paper discusses near              drive.
                   real-time processing of the underway navigation and geophysical                  - One Kennedy 9300 tape drive, 800/1600 bits per inch, 125 inches
                   data made available to the investigator during the course of a survey.           per second, connected to the VAX via an Emulex Unibus
                                            L INTRODUCTION                                          controller/formatter.
                         For 17 years, reaf-@time acquisition and processing of ship navi-          - A National Instruments Unibus IEEE488 GPIB controller to pro-
                   gation and marine geophysical data on the R/V T. Washington                      vide the communication link between the VAX and its slave
                   operated by the Scripps Institution of Oceanography (SIO) were han-              microprocessors.
                   dled by an IBM 1800 computer system permanently installed aboard                 - One Calcomp 965 four color belt bed plotter (R/V T. Washington
                   ship. From the start, the Shipboard Computer Group (SCG) at SIO                  only) with an effective plotting area restricted to approximately 34
                   has been responsible for operation and maintenance of this system                by 36 inches. Note that the plotteron the "online" system is devoted
                   and of nearly identical installations on R/V's Melville and Argo. In             to plotting in near real-time the ship's track in geographic coordi-
                   February 1984, these shipboard computer systems were replaced by                 nates and bottom contours when Sea Beam is used. The "offline"
                   DEC VAX-1 1/730 systems on the two ships still in operation: R/V's               plotter is used both as a post processing output device and as a
                   T. Washington and Melville [ 1 ]. To use these new computer systems              backup to the "online" plotter. These plotters communicate with the
                   for real-time data acquisition, SCG built a communication interface              VAX through a 9600 baud RS-232C serial line. The RIV Melville
                   based on an IEEE 488 General Purpose Interface Bus (GPIB) and an                 has only one Calcomp 502 flatbed plotter connected to a VAX-
                   IEEE 961 Standard bus (STD) to acquire, buffer and transmit data to              111730 through one of the STD/GPIB interfaces described below.
                   the VAX from various navigation and geophysical sensors.                         - Up to eight Graphon-140 (DEC VT-100 compatible) terminals pro-
                         In the following we first give a brief overview of the VAX-                vide user input/output and data display functions. All have graphic
                   11[730 computer hardware and peripherals installed aboard the ships              capabilities emulating the Tektronix 4010; some have attached
                   and of the various sensors interfaced to the computer through the                Okidata-92 printers with graphic enhancements, providing parallel
                   STD/GPIB data acquisition system. In Section III, we discuss the                 hard copy output.
                   real-time data acquisition system including descriptions of the STD                   Hardware interfaces to real-time data input/output devices are
                   and VAX-l lf730 software components, along with how these com-                   built into eight industrial instrumentation systems using the IEEE
                   ponents interact over the GPIB. We describe the near real-time                   961 STD bus protocol. Each STD system contains a single Z80
                   VAX-lln30 software used for data processing, storage, and to drive               microprocessor supporting from four to sixteen kilobytes of memory;
                   the displays for the various devices in section IV. And we conclude              direct memory access (DMA); a GPIB for communicating with the
                   with comments relating to both the strong and weak aspects of the                "host" computer, together with a variety of digital, analog and spe-
                   data acquisition and processing system, together with ideas for future           cialized data acquisition interface cards. Each STD system also has
                   improvements.                                                                    its own software clock which is used to time stamp all data passing
                                                                                                    from one of the acquisition devices through it to the VAX. A
                                        H. SYSTEM OVERVIEW                                          hardware clock which displays day-of-the-year, hours, minutes and
                         On board ship, two Digital Equipment           Corporation VAX-            seconds can be set and interrogated through the STD/GPIB VAX
                   lln30 mini computers provide the "main               frame" computing            link.
                   envirortment. Each machine is equipped with a floating point                          As shown in Figure 1, the navigational sensors interfaced to the
                   accelerator and four megabytes of memory. One is designated as                   VAX through the Z80/STD/GPIB link include: a gyrocompass for
                   "online"; its primary responsibility is to interface with the various            the ship's heading, a dual-axis Doppler current profiler for the ship's
                   shipboard instruments for real time data acquisition and display. The            speed, a Transit satellite receiver and a Loran-C receiver for the

                                                                       CH2585-8/88/0000- 509         $1 @1988 1EEE

                                            NAVIGATION DATA DEVICES                                                  REA IME                                                     INITIALIZE                                              CLOCK INTERR
                                                                                                                        CLOCK                                                    Reset clock                                               K41MR            u@
                                   GYYFO      DOP                                                                                                                    Clear poll and transfer tables
                                                                                                                                                                        Set-up GPIB/DMA protocol                                         rR`.-d-4o-.k_.7.7
                                                                                                                                                                                                                                         Idata  buffer _j

                                                                                                                                                                            MAIN POLLING Loop
                                                             7                                                                                                            Read clock and update                                          address Into transf
                                                                                                                                                                             timeout counters                                            table and rot.,    rn
                                                     Z801STD BUS MICROPROCESSOR SYSTEM
                                            Data Collection, Data Buffering and Software Clock                                                                                   dela                                                    Decode Identity and
                                                                                                                                                                                               yes        read in                        branch to service
                                                                                                                                                                            available                                                      routine
                                                                                                                                                                                 from                       buffer
                                                                                                                                                                                                                                         ROM CODES
                                                                                                                                                                                 A
                                                                                                                                                                                                                                AK - acknowledge
                                                                                                                                                                                                                                         recelved,clear
                                                     UNDERWAY DATA HARDWARE DEVICES
                                                                                                                                                                                                             data                        appropriate slot
                                                                                                                                                                                     no                      valid       yes             in transfer table
                                                                                                                                                                                                                                  01.    download buffer
                                                                                                                                                                                                                                         to specified
                                                                                                                                                                                                                                         RAM address.
                                                   MAGNE-Tncs                             IEEE-488 GPIB LINK                                                                                                                     XQ_     fill in poll
                                                        ISP@
                                                                Y
                                                  fDISPLAY                                      TO VAX 111730 __7                                                                Check transfer table and perform                        address to turn
                                                                                                                                   7
                                                                                                                                                                                     any pending data buffer,                            device on or off.
                                                                                                                                                                                 acknowledge, or retry transfers
                                  Figure 1. Architecture of the real-time data acquisition system.                                                                                        to VAX 11/730                                  RAM CODES
                                                                                                                                                                                                                                         Ind! cate which
                                                                                                                                                                                                                                         device service
                              ship's position. Note that the receiver for the Global Positioning                                                                                                                                         routine is to be
                              System (GPS) transmits its data directly to the VAX by a serial (RS-                                                                                                                                         evok .
                              232C) link.                                                                                                                                                                                                Return from
                                                                                                                                                                device                    Call device                                    service routine
                                        Underway scientific data collected on the RN T. Washington                                                             servi             yes
                                                                                                                                                                     'Ice
                              may vary from leg to leg, depending upon the particular scientific                                                    no       address 1.                        service
                                                                                                                                                                in poll                        utine
                              requirements for that leg. The "standard" devices installed on board                                                               table
                              ship which can be serviced in any desired combination include: a
                              gravimeter, a magnetometer, a Sea Beam mutlibeam echo-sounder,                                                                                                   Increment
                              an expendable bathythennograph and a one- or two-channel seismic                                                                                                 poll table
                              system. A subset of these devices, no gravimeter and no Sea Beam                                                                                                 Iaddress
                              system, is also available aboard the R/V Melville. Special "one                                                       Figure 2. Flow chart of the Z80 ROM software common to all STD
                              time" devices have also been accommodated at the request of many                                                      units.
                              chief scientists, but will not be discussed here.
                                        111. STANDARD BUS TO VAX-11/730 INTERFACE                                                                           The bi-directional communication link provides the
                                                                                                                                                    input/output path between the STD/Z80 and the VAX for data
                                        The UNIX BSD 4.3 operating system has no "real-time"                                                        acquisition, device control and the downloading of RAM device
                              pretensions in the data acquisition and control sense; however it does                                                specific software. These routines accept packets sent from the VAX,
                              provide flexible capabilities that would be difficult to reproduce on a                                               inform the VAX of a full data buffer ready to be sent, transmit pack-
                              computer required to respond in microseconds to external events.                                                      ets to the VAX, construct check characters for each transmission and
                              By incorporating the STD/Z80s to handle the input/output details                                                      initiate retransmissions as needed.
                              and bringing buffers of data into the mainframe computer only as                                                            . Great care was taken in the design of the polling loop to insure
                              fast as is convenient for navigational and human response times, the                                                  each device an equal "time slice" of the Z80's attention. No "loop"
                              VAX is allowed to concentrate on the interactive human-to-data                                                        or "wait" states are allowed; if a device is not ready to accept or to
                              interface where UNIX performs so well.                                                                                send data, the next device in line is interrogated. By maintaining
                                        Our STD/Z80 design philosophy was to allow a single                                                         tight control over both the ROM and RAM software routines, a dev-
                              microprocessor to control a maximum of three external devices.                                                        ice can be serviced less than a millisecond after its "ready" flag is
                              This limitation keeps the Z80s lightly loaded for increased reliability                                               activated. This method eliminates the complexity and overhead of
                              and simplicity of programming. Configuration and control informa-                                                     an interrupt driven scheme without compromising data integrity.
                              tion data are maintained in random access memory (RAM) tables to                                                      Some of the device interfaces requiring high data rates incorporate
                              allow dynamic activation/deactivation of any device without disturb-                                                  first-in-first-out (FIFO) buffers to enable the STD/Z80 to sample and
                              ing the operation of other devices sharing the same STD slot. Data                                                    store many bytes within a single polling cycle.
                              buffer sizes vary from a few dozen bytes up to sixteen kilobytes,                                                             The clock in each STD unit consists of a sixteen bit hardware
                              with larger buffers possible. Most of the buffers are made small so                                                   register, driven by a rubidiurn vapor controlled pulse train with one
                              the VAX will always have sufficiently recent data and so that any                                                     millisecond resolution, together with a sixteen bit high-order counter
                              problems with the instrument or transmission path will be detected                                                    containing the time-of-day in tens of seconds. A "global" interrupt
                              early.                                                                                                                can be generated by the VAX to force all STD clocks to report their
                                        Each Z80 read only memory (ROM) contains approximately                                                      current values. Clock synchronization checks are performed
                                                                               7

                                                                                                                                                                                               Yes

                                                                                                                                                                                                                         Yes
                                                                                                                                                    ,F.tZy"

                              one kilobyte of code to provide the following elements: routines for                                                  automatically every five minutes. The VAX support software allows
                              communicating via the GPIB with the VAX; a polling loop to allow                                                      users to interrogate the clocks at any time. Every data buffer
                              frequent testing for device activity; a clock synchronization interrupt                                               includes at least two time readings, the time of the first and the time
                              routine; clock reading and setting routines; and a power-up and reset                                                 of the last data samples contained in the buffer; each sample is timed
                              initialization routine (see Figure 2).                                                                                in some data streams.

                                                                                                                                           510

                       Device specific software resides in RAM and operates under                                 INITIALIZE
                 the control of its associated ROM polling and transfer routines.                        Set-up   Interrupt servicing            Set flag to
                 Although the detailed functions of the RAM code vary according to                                Clear GPIB interface               read
                 the instrument it services, the overall operations are quite similar.                Read device configuration file            configuration
                 Data input routines are responsible for testing device ready status,                                                                file
                 reading in the data in either serial or parallel format, decimating and
                 or reformatting the data as necessary, attaching a time stamp to the                             MAIN PROGRAM LOOP            Reconfig.
                 data buffer and notifying the ROM when a buffer is ready to be                                   Dormant until one of
                 transferred. Output routines normally act as buffers between the                                 following occurs:          SRO Service
                 VAX and the device receiving its data; additional services such as
                 flow control and data reformating are supplied in some cases.                                    Interrupt signaled            Wakeup
                       All Z80 software is written in assembly language using utilities                           1 second loop active         Timeout
                 developed on the VAX by SCG. These utilities include a cross-                                        I
                 assembler, an object code downloader and a monitor which runs in                                 Send STD clock read        Return from
                 an unused STD slot. The monitor communicates with the VAX                               command If timetic file               Interrupt
                 downloader to check and bum EPROMs and to provide code                                           exists; delete file         routine(s)
                 verification and debugging capabilities.                                                         -  +
                       The software for the real-time data acquisition system in the                      Retry   fan, unacknowledged               Identify STD
                 VAX is controlled by a "core program" called: GPCON (GPib CON-                                   bfe's sent to STD a                issued SRO
                 troll . This program is run as a high priority UNIX server (i.e. a                      max      U, of two times and               urn If queue
                                                                                                                  'm
                                                                                                           p
                                                                                                       F          'Int message if failure            ern t
                 background process which lies dormant until activated by an external
                 event) to maintain communication with the STD/Z80s. A                                   Initiate GPIB transfers to
                 configuration file is read by GPCON at start-up or upon command                                  STD for all data          Read in GPIB buffer,
                 from a "privileged" user. This file contains an STD slot number,                                 buffer files found       send VAX acknowledge
                 download and execute addresses, and an identity tag for each device.                                                        and decode identity
                 This information insures the instrument support software and com-
                 munication table entries are, in place to accept and/or transfer data.                           sad In configuration           If
                 As mentioned above, the "dynamic" configuration allows instru-                       F Rfile If flag is set                    Sm         yes
                 ments to be "turned on or off' without affecting other devices in the                                                      acknowidg.
                                                                                                                  Decrement one second         reeved       delete Its
                 same STD slot.                                                                           _@@cycle count                                       file
                       After initialization, GPCON puts itself into a ten minute sleep             _F
                 cycle until one of the following events occurs (Fig. 3):                                                                      no
                 1. A VAX program requests a data transfer to the STD by creating a                                                      Write the buffer to Its file
                 file whose name is unique to a particular STD slot containing the
                 data together with header information describing the device to be                     Figure 3. Flow chart of the GPIB control program GPCON.
                 serviced. The program then sends a "wakeup" signal, forcing
                 GPCON out of its sleep cycle to begin transferring data from any                  3. A special signal can be sent to GPCON to force it to wake up and
                 STD files it finds. Upon awakening, GPC0JV cycles for 6 one                       read its configuration file. The polling loop is again reactivated after
                 second intervals to insure all new or pending retry transfers are ini-            the new configuration information has been obtained.
                 tiated before resuming its ten minute sleep cycle.                                4. The ten minute "watchdog" timeout should never occur under
                       Clock interrogation programs create a "timetic" file which will             normal operating conditions. Even with no instruments active, the
                 cause GPCON to send an "interface clear" interrupt to all STD sys-                STD clocks automatically report their readings every five minutes;
                 tems. This interrupt signals each STD to read its clock and send the              therefore this wakeup condition indicates a problem in the GPIB sys-
                 results to the VAX.                                                               tem.
                 2. One of the STD systems initiates a service request (SRQ) inter-                     The GPIB VAX support software include both mainline and
                 rupt when it has a data buffer ready for transfer to the VAX. The                 subroutine versions of utilities to: (1) Provide "wakeups" to signal
                 header section of the buffer contains a device identifier, time stamp,            GPCON to initiate a data transfer or reread its configuration file. (2)
                 data byte count and any additional information specific to that partic-           Download and activate Z80 software for an entire STD system
                 ular instrument. Control is then transferred to an interrupt routine              configuration or for selected device(s) on the system. (3) Deactivate
                 which polls the GPIB to determine which STD system requires atten-                selected device(s) on the STD. (4) Set, interrogate and report the
                 tion and initiates a transfer to the VAX. A checksum is performed                 STD clocks.
                 and, if all is well, the device identifier is decoded and its data are
                 written (or appended) to a file associated with that identifier and a                  All the VAX GPIB system and-support software is written in
                 "received acknowledge" transfer is initiated over the GPIB to that                the C programming language. The ease of defining device structures
                 STD.                                                                              and implementing the "signal-interrupt" capability made C the logi-
                       A data buffer may contain an "acknowledge identifier" which                 cal choice over other high level languages available. Some addi-
                 informs GPCON that a previous VAX to STD transfer has been                        tional user interface utilities have been developed using the UNIX
                 received and verified by the STD. Upon receipt of this identifier, any            shell script feature. These are mainly "one-time" programs to pr6-
                 pending retransmissions for that device are cancelled.                            vide some non-standard information or control options; useful scripts
                                                                                                   are recoded in C for increased efficiency.
                       The interrupt routine exits back into a now active polling loop
                 to service any VAX to STD transfer requests that were made while                                 IV. NEAR REAL-TIME PROCESSING
                 the STD data buffers were being received.                                              All of the VAX data acquisition, process control and display
                                                                                                                                            Poll to
                                                                                                                                            slot that
                                                                                                                                             and ret
                                                                                                                                                  Is

                                                                                                                                                           Y
                                                                                                                                                             -s
                                                                                                                                                             .

                                                                                             511

                              programs receive and or transmit their data buffers under virtually
                              identical procedures (Fig. 3). Input routing is controlled through the
                              use of unique device identity files; output to a selected STD is deter-                                                                            IEEE-488 GPIB LINK                         SERIAL DATA LINK
                              mined by the device identifier contained in the header portion of the                                                                              IFFIDIVISMSYMSTEM                                  FROM DEVICE,
                              data buffer.
                                      VAX input is obtained from files created either by GPC01V or                                                                                                          GPCCN                              GPS Navigation
                              by a UNIX "cat" command to a serial port. These files continue to                                                                                                VAX GPIB Interface
                              grow until the servicing program is activated to perform a specific                                                                                                     Controller
                              processing function which always includes the removal of its input                                                                                                                                                                      op
                                                                                                                                                            .*IMIM
                              file so no data overlap can occur between processing cycles.
                                                                                                                                                                                 .4               DISK 1/0 DATA
                                                                                                                                                                                                            AND
                                                                                                                                                                           di                                                                                         AM
                                      A program initiates output to the STD by creating a file and                                                                                             HANDSHAKING FILES
                                                                                                                                                                                                                                                                                 .M
                              sending a "wakeup" signal to GPCON. This file has the name                                                                          logelock
                                                                                                                                                                                                            S I
                                                                                                                                                                                                 Hard/ o t        Clocks
                                                                                                                                                                  readcloks
                              GPoutN where N corresponds to the STD device slot number (0
                                                                                                                                                                                                    -Doppler Log                                dmav,     s
                                                                                                                                        priate
                              through 7). The data buffer is sent over the GPIB to the appro
                                                                                                                                                              ..........
                              STD slot; the ROM allocated to that slot uses the header identifier to
                                                                                                                                                                      0 MV
                                                                                                                                                                                                            Gyro
                              determine which RAM servicing routine to activate.
                                      The three following subsections describe program operation,
                                                                                                                                                                                 fiffiR,
                              together with the data and communication files required to process,
                              display and archive the real-time information presented to the VAX                                                                     a 000                            Transit Sat
                                                                                                                                                                                                                                             . . . . . . ......
                                                                                                                                                                                                                                                      . . . . . . . . . .
                              (Fig. 4). These subsections am: STD CLOCKS, NAVIGATION and
                                                                                                                                                                                                                                                       lorxfr
                              UNDERWAY DATA.                                                                                                                                                                Loran
                                                                                                                                                                                                                                      a
                                                                  IV (a) STD CLOCKS                                                                                                                         Gravity
                                      Data integrity requires that all information received over the                                                                                                                                                 cypmag
                              GPIB be synchronized by time. As mentioned before, our procedure
                              is to include at least the times of the first and last samples in each
                                                                                                                                                                  .......  . .........
                                                                                                                                                                        s@draw                              Sea Beam
                              buffer. Time differences between STD slots are monitored by the
                              logclocks and readcloks command scripts. Both of these'scripts                                                                    . . . . . . . . . .. . . . . . . .
                                                                                                                                                                                                                                       . . . . . . . .                           ..
                                                                                                                                                                                                            elsmic
                                                                                                                                                                                                                                                    seisS[1-21
                                                                                                                                                                                                            S
                              interrogate the clocks, wait until the clocks have reported their time
                                                                                                                                                            .....................
                                                                                                                                                                                     02.
                                                                                                                                                                     . . ...                                                                M.77-- 77     ."O.M.7-5
                              count registers (by noting the existence of the numbered clock iden-
                              tity files), and then execute the program clkmn to convert the counts                                                                        bt                               XBT
                              to time in hours, minutes, seconds and milliseconds. Every five
                              minutes logclocks appends the times to the stdtimes file; readcloks is                                                        Figure 4. Block diagram of programs and data Mes associated with
                              invoked from a terminal to print the current STD times on that termi-                                                         each sensor. Programs appear in the boxes within the shaded area,
                              nal and to append the values to the stdtimes file. The output format                                                          with data files names listed directly above the box.
                              is:
                              Tue Oct 27 18:45:43 GMT 1987                                                                                                  entire water column within beam range) are sampled every 600 mil-
                              STD2time= 18:45:39.589 offset= 482                                                                                            liseconds, packed into 16 kilobyte buffers and sent to the VAX every
                              STD3time= 18:45:39.589 offset= 190                                                                                            twelve seconds.
                              STD4time= 18:45:39.589 offset= 2751                                                                                                    A background* process (drnav) performs the functions involv-
                              STD5time= 18:45:39.589 offset= -87                                                                                            ing measurement of ship's speed and heading, inference of ship's
                              STD6fime= 18:45:39,589 offset= 412                                                                                            true velocity over the ground and plotting of DR and fix positions.
                              HARDtime= 1-8:45:39.589 date= 1987/10/27 (300 of year)                                                                        This process "wakes up" at one minute intervals to read values of
                                      The first line is the VAX time when the clocks were recorded                                                          speed and heading buffered in the VAX. Speed is determined by
                              and is typically three to five seconds after the interrogation time.                                                          applying drift history to the two dimensional Doppler speed vector
                              Offset values represent millisecond adjustments needed to synchron-                                                           course is calculated by combining the gyro reading with the Doppler
                              ize the individual software clocks with the hardware (HARDtime),                                                              speed vector. The output includes 10 second averages for speed and
                              clock. One of the tasks of program clknwn is to compute these clock                                                           course, together with updated one minute ship positions.
                              offsets and to send the corresponding adjustment to the appropriate                                                                    Inputs to drnav are the the raw Doppler D)oinpf and gyro
                              STD units.                                                                                                                    GYinpf files created by GPCON (Fig. 4), together with a file called
                                                                   IV(b) NAVIGATION                                                                         saved containing all the information that may be shared by con-
                                                                                                                                                            current processes (i.e. current position, last Transit satellite fix posi-
                              Dead-Reckon (DR)                                                                                                              tion, course, speed, drift, as well as times associated with these data).
                                      Analog heading information is obtained from the ship's Sperry                                                         A simple software locking scheme was implemented to prevent the
                              Mark-37 gymscope, passed through a 10 bit synchro-to-digital con-                                                             programs that both read from and write to this Me from obtaining
                              verter and sampled at one second intervals by the STD system.                                                                 simultaneous access to the data and possibly corrupting them.
                              When 20 readings have been accumulated, the data buffer is                                                                             File DPinpf is also used by the background speed display pro-
                              transferred to the VAX via the GPIB.                                                                                          gram spddsply. The Arrietek-Straza Doppler Current Proffier has no
                                      A dual-axis Ametek-Straza Doppler Current Proffier provides                                                           direct speed indication capabilities; spddsply filters the raw values to
                              ship's speed and, if desired, ocean current profile data. Selected bins
                              (depth windows) are collected at 1.8 second intervals, buffered in the                                                        *All background processes discussed in this paper, with the exception of GPCON
                              STD and passed along to the VAX every six seconds. If ocean                                                                   which is activated by "signals", use the UNIX "sleep" mechanism to control their
                                                                                                                                                                                                     LINK
                                                                                                                                                                                             D
                                                                                                                                                                                                            1
                                                                                                                                                                                             @
                                                                                                                                                                                                            CON
                                                                                                                                                                                               VAX GPIB           1.
                                                                                                                                                                                                       C..troll

                              current profile data are to be collected, aU bmis (representing the                                                           cycle periods.

                                                                                                                                                     512'

                                                                                                             B
                                                                         0&1200- - +                                                                                                0 A@
                                                                                                                                            SEA BEAM OFF
                                                                                    +                                                                            J%..
                                                                                                                                                          I          _%diRk
                                                                  O&JI28-                                     MAGNETIC                   CENTER
                                                                                                              ANOMALY                       BEAM
                                                               06,             +                                PROFILE,                  DEPTH->,o,%
                                                                    1100@@                                                                                                 ftv,900
                                                                                                                                                                         ftft'14

                                                                04,
                                                                   Irooo                                                           $000                   q%00
                                                                                                                                                          TRACK
                                                                                                                                                    ADJUSTMENT
                                                                                                                                                          FROM
                                                                1      10    km,                                    01                                  0418 FIX
                                0--
                                                                                                                        449
                                                                         LEGEND

                                                             +       15  MINUTE DR
                                                                        POSITION

                                                           x    TRANSIT SATELLITE
                                                                        POSITION
                                                             SOLID LINE RE                                                            "0410.                  10 km
                                                                                 PRESENTS                                                   1100                           _.J
                                                            SHIP'S SMOOTHED TRACK
                               0610,                          BETWEEEN LAST TWO
                                   1100                       SATELLITE POSITIONS.

                                           Figure 5. Examples of real-time plots: a) real-time DR plot of the ship's track with sattelite fixes information,
                                           b) real-time Sea Beam contours and profile of magnetics data along the ship's track.
                  provide a smoothed data stream for driving serial LED speed                            (3) a permanent archive file (csespd) which contains 10 second aver-
                  displays located on the bridge and in the scientific watchstander's                    ages for time, course and speed. This file is used primarily as input
                  area.                                                                                  to the navigation post-processing program, but is also available to
                        In addition to updating position, course and speed values in                     various utility programs that use Us information.
                  saved, drnav outputs include:                                                          (4) plots of the ship's position in Mercator projection (Figure 5.a)
                  (1) archive files DPpfile and GYpfile which contain the raw Doppler                    are also generated by drnav. Spool files containing plot moves are
                  and gyro data in a compacted format. These files are not normally                      created for user defined repetition rates (usually 5, 10, 15 or 30
                  retained for more than a few days; transfer to permanent magnetic                      minute intervals) to output the most recent DR position to the Cal-
                  tape is done only if Doppler current profiler information is desired.                  comp 965 plotter. As discussed in Section W(c), near real-time Sea
                  (2) a circular file (drfib which is large enough to hold approximately                 Beam generated bottom contours can also be included on this plot
                  the last 12 hours of one minute entries for the ship's time, course,                   (Fig 5.b). Transit satellite fix positions are automatically plotted
                  speed and position, This file is used by the Transit satellite fix calcu-              along with the DR; or, if desired, fixes may be plotted without the
                  lation and smooth plot program discussed below, and by utility pro-                    DR.
                  grams which provide position data for survey sites, XBT stations,                          . Unless otherwise indicated, all archive files are periodically
                  etc.                                                                                   transferred to permanent magnetic tape storage. Two tape copies are

                                                                                                    513

                      made; one is returned to SIO at the end of each cruise leg and the                      the magnetics data to be plotted, at user defined scales and offsets,
                      other remains onboard to serve as a backup to the transported tape,                     along the ship's track (see Figure 5.b).
                      Transit Satellite                                                                       Global Positioning System (GPS)
                            Automatic updating of ship's position is accomplished through                           Depending upon the ship's location relative to the present GPS
                      fixes obtained from our Transit satellite (TRANSAT) system. Both                        satellite constellation, absolute positions to within a few tens of
                      GPS and Loran are used to supplement TRANSAT, but their current                         meters can be obtained for periods of four to twelve hours each day.
                      availability cannot be counted upon for 24 hour coverage in all the                     Serial (ASCII character format) position fix data are obtained at user
                      oceanic research areas of interest.                                                     selected intervals, usually 10 seconds, from a Trimble-4000AX
                            In the TRANSAT system, a dual channel (150 and 400                                receiver and transferred directly to the VAX via a 1200 baud RS-
                      megahertz) ITT 5001 receiver performs an analog-to-digital conver-                      232C serial line. Acquisition and logging of GPS position fixes are
                      sion of the incoming 4.6 second Doppler count interval data. At the                     controlled by a UNIX C-shell script (GPT.Tr-set.up) which
                      end of a satellite pass, it sends these data to the VAX, through its                    configures the RS-232C port and starts a UNIX background process
                      STD/GPIB interface, for position fix calculation. Position fixes may                    to read the port and save the position fix information in file GPTinpf.
                      be obtained at intervals varying from tens of minutes to six hours,                     The drift adjustment program is the only near real-time process that
                      depending upon the ship's latitude and the number of healthy satel-                     uses all the GPS fixes made available by the user selected transfer
                      lites in orbit. A series of fix position computation, drift determina-                  interval. Terminal display and plotting processes use one minute fix
                      tion and smoothed track plot programs are executed under control of                     intervals.
                      the satloop script. As its name implies, this script runs in a closed                         When GPS becomes an active world-wide 24 hour system, our
                      loop invoking the processes in the order required.                                      current DR scheme will give way to GPS navigation. Until then, the
                            The first program in the loop, satacq.out, checks the current                     only contribution of GPS to real-time navigation is through drift
                      condition of the satellite data input file SAinpf. Three possible con-                  adjustments and North and East components of drift applied to the
                      ditions and the program's corresponding actions are:                                    ship's DR positions are calculated from Transit satellite fix differ-
                      1. The file does not exist; satacq.out sleeps for twenty seconds,                       ences.
                      wakes up and tries again.                                                                     A script (DOclosedloop) operates on a five minute cycle to
                      2. The file exists and its status (time of last update) has changed.                    update the drift values. This script activates the process
                      Again, satacq.out sleeps for twenty seconds before performing                           triDRF.closedloop which reads the last few thousand bytes from
                      another status check.                                                                   GPTinpf and averages a number of carefully screened fixes. This
                      3. The file exists and its status has not changed since the last time it                average is fitted to speed lines in the North and East directions for
                      was tested. This condition indicates that all the data have been gath-                  standard deviation calculation. If all is well, the new drift adjust-
                      ered from the satellite's pass and the processing phase can now be                      ment is written to saved. If no new inputs are available or if the fixes
                      started.                                                                                appear to be in error, the values in saved are allowed to slowly revert
                            The file is then renamed SAinpflunp to clear the way for the                      back to a smoothed version of recent drifts. A history of drift
                      next acquisition cycle and its raw data compacted and appended to                       changes produced are logged into the file TRIlogCL.
                      the permanent archive file SApfile. Data validity checks are per-                             Various utility programs have been developed to display and
                      formed and if any problems am detected, an appropriate error mes-                       plot GPS fixes from the data in GPTinpf. GPS positions may be
                      sage is written to the satfixes file.                                                   added to an existing DR Mercator plot by gpsplt which can be exe-
                            The next program in line, satOr, collects, reformats and edits                    cuted either under operator control or automatically on a preselected
                      the information from the files SAinpf ttnp and drfil. These data am                     time cycle. Because the status of the GPS navigation system is still
                      written to file file.0r; again, any error condition is reported by writing              undergoing changes, the corresponding processing software is regu-
                      a diagnostic message to sa#ixes. File file.Or is used as input to pro-                  larly updated as new GPS developments are implemented.
                      gram sat1r which does the preliminary short count calculations. The                     Loran-C
                      results are written out to file file.Ir with error reports again directed                     Due to the lack of world-wide coverage and occasional unrelia-
                      to satfixes.                                                                            bility of Loran-C, positions obtained from this source are not
                            The last program in the satellite fix computation loop is                         integrated into our real-time navigation. These fixes are used as a
                      sat2r.out which calculates the ship's position and fix statistics using                 supplement to the information provided by the Transit satellite and
                      the information obtained from file.1r. This information is written to                   GPS systems.
                      file last-fix and appended to satfixes. Users can obtain the most                             Loran-C lines-of-position are collected and converted to char-
                      recent fix from the former or a longer term history of fixes from the                   acter navigation inform ation by a Trimble-200 receiver, and supplied
                      latter. The saved file is then updated by this program.                                 to a 1200 baud serial STD interface at approximately ten second
                            Two other processes are included in the satloop operational                       intervals. The STD extracts time, latitude, longitude, and transmitter
                      cycle. The first program (drift) calculates the North and East com-                     time differences from each fix and, when three fixes have been accu-
                      ponents of a drift vector by comparing the TRANSAT position with                        mulated, it passes these parameters to the VAX which stores them in
                      the DR position at the time the fix was obtained. A smoothing func-                     file LOinpf. Under stable operating conditions, data are appended to
                      tion factors in past drift values to minimize errors due to either a bad                the file at approximately thirty second intervals. However, if less
                      TRANSAT fix or bad DR.                                                                  than three fixes have been accumulated and 45 seconds have elapsed
                            The second process invoked by sattoop after a successful                          since the last fix, the available parameters are passed in order to
                      TRANSAT pass is the real-time smooth plot program sphnn. From                           empty the buffer.
                      the fix position information in saved and the course-speed data in                            A background program torxfr loops waiting for any new entries
                      drfil, spbnn computes a smoothed ship's track between the current                       to appear in Winpf. lorxfr reformats the data and writes a one line
                      and previous fixes. A plot spool file is created and the Calcomp 965                    summary to the file loran for each fix position encountered.
                      then plots this smooth track (Fig. 5.a). User options allow the navi-                         The loran file serves both as a permanent archive and as a
                      gation data to be merged with magnetics (file magfil) and profiles of                   source for utility programs to display and plot Loran-C fix positions.

                                                                                                        514

                  Program lorplt operates either under operator control or automati-                  This file is used by the smooth plot process for profiling magnetics
                  cally on a preselected time cycle to add Loran-C positions to an                    (total field or magnetic field anomaly) along the ship's track (Fig.
                  existing DR Mercator plot. This feature, together with the GPS plot                 5.b).
                  program gpspit, allow all navigational fixes to be plotted and com-                        Several utility programs exist to manipulate and display mag-
                  pared in near real-time.                                                            netic data in near real-time. Both terminal graphics and hard copy
                                        IV(c) UNDERWAY DATA                                           printouts of magnetics profile versus time are available on demand.
                  Gravity                                                                             Other features permit the scientific watchstander to call up on the ter-
                        One second pulse counts (1 pulse count is roughly 5 mGal) are                 minal the latest reading logged, or a series of the logged readings.
                  supplied by a Bell Aerospace Textron BGM-3 gravity meter to its                     Sea Beam
                  STD interface. The STD checks the validity of each 16-bit count,                           A General Instrument Sea Beam bathymetric survey system
                  appends the current time to each accepted value and, when ten values                installed on the R/V T Washington is also interfaced to the VAX
                  have been received, transfers the buffer to the VAX Program grvcpy                  through an STD/GPIB link. This multibeam echo-sounder forms 16
                  is executed on a five minute cycle to process the one second gravity                beams with 2 2/3* angular resolution over an athwartships sector of
                  "pulses" accumulated during the last time interval in file GVinpf.                  about 400 to provide cross-track coverage of roughly 3/4 of the water
                  The input Me is renamed by adding a amp extension to prevent                        depth. It contains a Data General Eclipse S-130 computer which
                  conflicts between the logging and processing functions. After                       controls timing and echo processing within the system and generates
                  compressing and archiving the pulse counts in permanent file                        anear-real-time swath of seafloor contours plotted in the direction of
                  GVpfile, the temporary Me is removed.                                               ship's travel. For every ping cycle (I to 16 sec. intervals depending
                        Scripts used to monitor the gravity data stream include two                   upon ocean depth), it also sends up to 16 pairs of depth and cross-
                  utilities to convert the pulse count data to milligals and print the,               track distance together with Eclipse time and ship's heading at
                  results. Script avGVin prints a series of the latest one second read-               transmit time, for a total of 34 16-bit words, to be logged on the
                  ings taken from GVinpf and script avGVpf prints the average of the                  VAX via the Z80/STD/GPIB link.
                  values stored in the permanent file GYpfile over the latest one minute                     The software in the Z80 microprocessor serves two functions.
                  interval. These scripts are normally setup to write their outputs to                Its primary function is to acquire the data sent by the Eclipse com-
                  data files which the scientific watchstander can routinely query to                 puter and, when 3 pings have been received, to transfer them to the
                  check the integrity of the data collected.                                          VAX. SCO's standard GPIB transfer header information is added to
                        Other data monitoring procedures include two near real-time                   this group of three pings. The second function is to receive the ship's
                  display programs: graphGV and grvchart. Script graphGV produces                     speed from the VAX and to send it to the Eclipse.
                  a time series plot of the last five minutes of one second gravity                      - On the VAX, the Sea Beam data acquisition software requires
                  counts from GVpfile. Maximum, minimum and arithmetic mean                           about 10 megabytes of disk storage for the data files and 2 mega-
                  values are also displayed. gravchart is a more elaborate C program,                 bytes of storage for the programs. Program GPCON appends each
                  contributed by scientists from the Lamont-Doherty Geological                        set of three pings transferred by the GPIB to the Sea Beam data file
                  Observatory, which computes the free-air gravity anomaly. The pro-                  SB!npf. These data are then handled by three background processes:
                  gram reads one minute averages of DR position, course and speed                     SBstdrw, SBmerge and SBplot.
                  from the common data file saved, and one second pulse counts from                      . Program SBstdtrw (Sea Beam standard bus to raw file program)
                  GVpfile. An estimate of the observed gravity is then calculate         'd, the      is executed on a 40 second cycle to process the data accumulated in
                  F,6tvos correction is applied, and an estimate of the normal gravity                SBinpf during the last time interval. The first processing step is to
                  and of the free-air anomaly are computed. The observed gravity, its                 rename the file to SBinpftmp and append its contents to file SBpfile.
                  F,dtvos corrected value and the free-air anomaly obtained in this                   This file is a raw backup in case of problems ftirther on in the real-
                  fashion are displayed symbolically on an Okidata printer. Such a                    time processing. The next operations include adding the current
                  near real-time display is useful during gravity surveys at sea, as the              UNIX time to the data in SBinpfttnp and writing these data into both
                  free-air anomaly displayed can be compared directly with the free-air               the SBpfile file and a circular file called raw.seabeam. The
                  anomaly values shown on existing gravity maps for the oceans.                       raw.seabeam file holds the data until navigation for the same time
                  Magnetics                                                                           period (one second resolution) is available.
                        Binary Coded Decimal (BCD) magnetic field readings are                               At the start of every 40 second cycle of processing new data,
                  obtained at six second intervals from a EG&G GeoMetrics G-801/3                     SBstdtrw also finds the center beam and the closest return. (first
                  magnetometer. The STD software drives a six segment Light Emit-                     arrival) and writes these two values together with UNIX time to a file
                  ting Diode (LED) device to display the most recent reading and,                     called depfil which can accomodate 299 such records. UNIX time is
                  when ten readings have been collected, transfers the buffered data to               stored in a 32 bit integer word and isthe number of seconds elapsed
                  the VAX. The processing and display of magnetic data is a routine                   since Jan 1, 1970. These data are saved to be used by other programs
                  procedure carried out on all cruise legs when the EG&G GeoMetrics                   such as the sound source synchronizer which schedules the firing rate
                  magnetometer is in operation. A real-time display, driven by the                    of the Sea Beam system, the seismic and the 3.5 kHz subbottom
                  STD software, shows the latest six second total field reading received              profilers [2].
                  to allow the computer technician to monitor the data stream to the                         The second background real-time job is then started with pro-
                  VAX.                                                                                gram SBrItnerge which sleeps several minutes between passes of the
                        Data compression and archiving functions are performed by                     data files. It merges the Sea Beam data found in the raw.seabeam
                  program cpymag which is also executed on a five minute time cycle.                  file with the dead reckoning navigation found in file drfil, written by
                  This process follows our standard procedure of renaming the input                   program drnav. The merged Sea Beam data is written into file
                  Me by adding a tmp extension to it; in this case MGinpf becomes                     rtin.seabewn in the SIO standard merge format of 50 16-bit words.
                  MG1npf.t?np. The BCD total field readings are then compressed and                   This file is a 5 Mbyte circular file and its pointers are kept in file
                  archived in the permanent file MGpfile and the temporary Me is                      seabewn.rtcommon.
                  removed. Program cpymag also maintains an additional circular Me,                          To output the ship's speed to the Eclipse, Ortmerge creates a
                  magfil, containing magnetic readings and their associated times.                    file GPouO which contains the ship's,speed converted to a binary

                                                                                                515

                       integer in the range of 0-1023 hex corresponding to speeds of 0 to 15                        Program oneshot (or twoshot for channel 2) can be executed to
                       knots. Note that due to a problem in the Eclipse software the speed                    display the last recorded event in near real-time. The file Sldspl is
                       sent by the VAX is limited to a lower bound of 1 knot. When                            used to produce a time series display of the recorded signal. By
                       GPCON finds this file it transfers it to the Z80 processor which then                  monitoring these plots, improper hardware setup or equipment mal-
                       sends the 10 bits of speed data to the digital-to-analog converter                     functions can be detected and quickly corrected.
                       hardware which provide ship's speed to the Eclipse computer.                           XBT (eXpendable BathyThermograph)
                             The last of the three background real-time jobs is handled by                          Temperature measurements from a Sippican MIK-9 XBT sys-
                       program SBplot. This program reads the Sea Beam data from                              tem are transferred through Sippican's GPIB interface to the
                       rtin.seabeam, contours it, and sends the output to the real-time Cal-                  appropriate STD where the data are buffered and passed along to the
                       comp 965 plotter (Fig. 5.b). SBplot gets the file pointers, contour                    VAX.
                       interval, and labeling information from the file seabeam. rt. common.                        The da  ta once acquired are stored on disk (about 4000 bytes
                       The contents of seabeam. rt. common can be monitored with program                      per T-4 drop) and displayed in near real-time on the operator's termi-
                       Cbeam. This allows the operator to use a CRT terminal to set the                       nal, with an optional hard copy printout available. The time needed
                       contour interval for the flatbed plotter display, monitor the amount of                for an XBT drop depends on the type of probe used, a typical T-4
                       space left in the holding file and turn contour plotting on and off.                   probe requires about 80 seconds to acquire the data. The actual cpu
                             In order to archive the Sea Beam data it must be extracted from                  usage is only several seconds during this 80 second interval.
                       the rim.seabeam file approximately every other day. This rate                                To do an XBT drop, program xbt is started on the VAX. This
                       depends on the ping rate, but them is enough room to last about 24                     program communicates with program xbt.src which is running in the
                       hours at a 2 second ping rate. Program sbcopy copies the data from                     Z80. xbtsrc establishes that the Sippican MK-9 interface is opera-
                       the circular,file rtm.seabeam and writes them into a file to be                        tional and relays this information back to xbt. The user informs the
                       archived in the SIO merge format.                                                      MK-9 of the type of probe being used through the the VAX to
                       Seismics                                                                               STDAZ80 link. Once the probe type has been established no more
                             The seismic system is used for acquiring seismic reflection or                   computer operator intervention is needed. The MK-9 interface waits
                       refraction signals received by hydrophones or sonobuoys. An inter-                     for data to become available and then transfers them to the VAX by
                       face designed at Scripps controls cycle time, delay time and acquisi-                  way of the STD. As data are collected, they are displayed on a
                       tion time for each event to be sampled. This interface applies the                     TEK-4010 compatible terminal in a graphic form. This is just a
                       appropriate filters to the incoming signal, digitizes it and passes it to              rough look at the data (uncorrected for thermistor non-linearity and
                       the VAX via its STD/GPIB link. Parallel systems are available for                      AID drift). At the end of the data acquisition phase, program xbt
                       simultaneous acquisition and processing of two input channels. Sam-                    reformats the raw data, adding the ship's position, ship's name, time
                       ple and delay times are controlled by switch settings on the                           and date. It then writes these data to a disk file in the XBTDATA
                       operator's control panel with 250 microseconds as the shortest sam-                    directory.
                       ple interval available. The STD data buffers accept a maximum of                             A shell script (DOxbr) assists the operator during the XBT data
                       sixteen kilobytes for each shot or event; therefore, to prevent data                   acquisition process. It runs all the commands needed to acquire, pro-
                       overflow, the operator must control the balance between sample rate                    cess, plot and archive the data. It starts by creating a new filename,
                       and event duration. The following paragraphs describe the process-                     unique for this leg. It then runs xbt,.xbt1soth, xbtplot, bathymessage,
                       ing applied to channel 1; except for program and file names ("J."                      and xbt-Smpl[ndx. It also produces a hard copy output on a printer
                       replaced by "2") the processing for channel 2 is identical.                            attached to the terminal running the script.
                             A l6kbyte buffer containing the sixteen bit data words is                              Two other scripts are used to help maintain order in the data
                       passed to the VAX at the conclusion of each event. The buffer                          directory. The script DObegincrulse which initializes the sequential
                       header contains a shot sequence count and a configuration word with                    number and prompts for cruise name, and the script DOendcruise
                       sample rate, delay time and sample time. Other words with urnique                      which nms program xbt-nodc converting all xbt drops to NODC for-
                       bit patterns are used to flag beginning and end of shot conditions.                    mat and which reminds the..operator to copy the data to tape.
                       Data words contain twelve bits of digital information and a four bit
                       scale value representing the gain applied to the value in the other                                              V. CONCLUSIONS
                       twelve bits.
                             A background process (seisSl) is activated every ten seconds to                        The system described in this paper has been in continuous
                       check for the existence of file Slinpf and, if found, rename it                        operation since February 1984. Hardware reliability has been excel-
                                                                                                              lent with only one significant failure on the R/V T. Washington's
                       Slinpf.imp   to ready the system for the next event. The 16kbyte                       "offline" computer. The system was back on-line within 48 hours
                       buffer represents a maximum shot sample size of 8000 words (e.g.                       after a faulty crystal oscillator had been detected and replaced; none
                       an eight second sample window at a one kHz sampling rate). As the                      of the data acquisition capabilities were affected by this interruption.
                       actual number of samples may not fill the full 16kbyte buffer passed,                  Had the failure been in the "ordine" system, the other computer
                       a header word indicates the number of samples present in the buffer                    would have been switched in by changing the STD/GPIB cable (no
                       to process.                                                                            power down/up required) and starting up the appropriate data
                             A "shot record" of appropriate length is constructed by unpack-                  acquisition processes.
                       ing each 16 bit sample (four gain plus 12 data) and converting it to
                       its equivalent 32 bit integer SEG-Y* format. Each shot record has a                          Once the system is booted and the data acquisition processes
                       240 byte binary header containing sequence count, shot                                 are started, only routine system monitoring (primarily archiving of
                       configuration, date and time prepended to it. This buffer is used to                   data to magnetic tape, purging the archived files and checking input
                       overwrite the near real-time plot data input Me Sldspl and is also                     devices) is required. This job, together with program development
                       appended to the permanent archive file SEGY]file.                                      and hardware maintenance, is normally handled at sea by a techni-
                                                                                                              cian from the Shipboard Computer Group. Collection of navigation
                       *SEG-Y is the data exchange magnetic tape format proposed by the Society of Ex-        along with a subset of underway data has been successfully done on
                       ploration Geophysicists Technical Standards Comn-tittee.                               the R/V Melville without a trained computer operator in attendance.

                                                                                                       516

                  Software command scripts handle the necessary details to provide a             4. Integration of gravity and Sea Beam center beam depth profiles
                  designated operator (usually the ship's Resident Technician) with the          into the smooth plot system. These features should be fairly
                  tools for activating and monitoring the data acquisition processes.            straight-forward and easy to implement but, as mentioned above,
                        Although little concern was given, during system development,            will require ship time for final testing and debugging.
                  to the eventual transport of this software to other computing                       Improving the computational and inter-communication capabil-
                  machines; use of the Fortran.77 and C programming languages                    ities of our existing mainframe machines is another area of high
                  should simplify this task if a switch to some other UNIX based sys-            priority. Personal compute  'rs (PCs) have been routinely used at sea
                  tem is desired. The only current requirement of the target machine is          for some time with access to the VAX- 11/730 real-time data bases
                  that it provide hardware and software support for the GPIB data                through primitive RS-232C file transfer procedures.
                  communication protocol. With appropriate acquisition device inter-                  On a cruise of the R/V T. Washington in the spring of 1987, an
                  face modifications, the STD/GPIB link could be replaced by RS-                 Alliant FX/l cornputer* was attached to the VAX-l 1/730's through
                  232C communication on a mainframe computer able to support the                 an Ethernet link. Prior to this installation, resource sharing between
                  overhead of the serial transmission of these data.                             the two VAX-l 11730's had been accomplished by use of magnetic
                        Most of the current VAX- 11/730 - BSD 4.3 real-time data                 tape, the UNIX utility "uucp" and, a serial data network scheme
                  acquisition software was adapted from the IBM 1800 system                      "slipnet." The purchase of Ethernet hardware and a simple
                  developed during the past 20 years. The increased power and flexi-             reconfiguration of the UNIX system provided true high speed net-
                  bility of these new computers have allowed us to continuously                  working between the three mainframe computers.
                  improve and fine tune our operations in cautious and slow incre-                    This successful mating demonstrated the versatility of a
                  ments. Caution is required, as in any software modification project,           networked system where each machine can be dedicated to a portion
                  to insure the new changes do not affect any of the existing features.          of the tasks required to be performed. In our case, the "online"
                  The sometimes painfully slow rate of system refining is due to the             VAX-11/730 handled only the data acquisition and near real-time
                  small portion of time at sea that can be dedicated to hardware and             processing; the "offline" machine served as backup and for software
                  software testing. Ship time is expensive and the scientists whose              development; while the FX/l provided a powerful time shared com-
                  grants pay for that time do not want to donate it to non-scientific pur-       puting environment.
                  poses. The old adage "if it's not broke, don't fix it" prevails on most
                  cruises.                                                                                           ACKNOWLEDGEMENTS
                        Hardware and software development and testing has, until                 Most of the software development work reported here has been
                  recently, been carried out on our shore based VAX-1 1/750, This has            funded by SIO institutional funds. Sea Beam related work was
                  not been a very satisfactory configuration because; 1) the system              funded in part through the Accelerated Research Initiative on multi-
                  must remain "up" for use by Scripps' radio station WAID, the                   beam systems sponsored by the Office of Naval Research, Contract #
                  scientific and administrative communities and; 2) subtle differences           N00014-85-G-0104. J.L. Abbott directed and was actively involved
                  exist between VAX-11/730 and VAX-11/750 architectures which                    in the development work performed by the Shipboard Computer
                  have affected the operation of some software packages. Recently,               Group. Under his guidance, the main contributors to software
                  the availability of used computer equipment at low cost has made it            developments reported here were G. Bouchard, J.S. Charters, R.L.
                  possible to put together a shore based VAX-l 1/730 and STD/GPIB                Moe, and J.M. Moore. P. Wessel and W.H.F. Smith at Lamont-
                  system to better emulate the shipboard environment.                            Doherty Geological Observatory contributed the grvchart program
                       Software modification and enhancement projects currently                  mentioned in Section IV(c) while at sea on the R/V T. Washington.
                  under consideration include:                                                   C. de Moustier brought this paper to publishable form. E. Ford for-
                  1. Automate the STD and VAX-11/730 clock corrections using                     matted the text and J. Griffith did the art work.
                  either the available high precision Transit or GPS satellite times.
                  The ability to detect and correct clock offsets greater than some                                        REFERENCES
                  defined threshold should be added.
                  2. Smoothing out the interaction between GPS and the dead-reckon               (1] Abbott, J. L., S. M. Smith, J. S. Charters, P. G. Downes, T.
                  program will be a high priority item as the GPS system approaches              Hylas, R. L. Moe, J. M. Moore and D. V. Stuber, Scripps Seagoing
                  full 24 hour coverage. More effort needs to be spent to determine              Computer Centers: Real-Time Data Acquisition and Processing,
                  the best combinations of data input editing and processing.                    IEEE Proceedings of the Fourth Working Symposium on Oceano-
                  3. Providing our own time stamp of Loran data so as not to rely on             graphic Data Systems, pp. 123-129, February 1986.
                  the information provided by the receiver. Invalid times, due to tem-
                  porary receiver malfunctions or improper initialization, sometimes             [2] Phillips, J. C., J. L. Abbott and C. de Moustier Multiple sound
                  make it difficult to correlate Loran positions with other navigational         source synchronizer for seafloor surveying Proc. Offshore Technol-
                  and underwav data.                                                             ogy Conference, OTC #5867, Houston, Texas, May 2-5, 1988.

                                                                                                 *On loan from Alliant Computer Systems Corporation. Acton Massachusetts.

                                                                                          517

                                                           A COMMON XBT/PERSONAL COMPUTER INTERFACE

                                                                                       STAFF*

                                                                              Oregon State University
                                                                             College of Oceanography
                                                                        Oceanography Admin. Bldg. 104
                                                                             Corvallis, OR 97331-5503

                                                 ABSTRACT                                       The Apple II computer was one of the first to approach a
                                                                                                solution to the interface problem. It was provided with a
                    Ile use of expendable probes, such as expandable bathy-                     number of 1/0 slots" for peripheral devices such as floppy
                    thermographs (XBTs) as temperature profilers, in the                        disks. One of the early peripherals was an RS-232 interface
                    oceanographic research and operational data gathering                       (intended for modem access). A unique characteristic was a
                    community is well established. Thousands of XBT probes are                  memory chip in the interface which provided the necessary
                    cast annually to contribute to a broad suite of national                    information to the resident software (frequently BASIC) to
                    oceanographic research programs and the National Weather                    provide easy peripheral access.
                    Service.
                                                                                                Now, most small computers, including those of the "IBM PC-
                    This paper will report on the improved system design                        AT-XT and Clone" group provide an RS-232 port as a
                    flexibility for a digital XBT electronic interface created by the           standard feature complete with high-level language access.
                    simplified serial communications and hardware features of RS-               Most of the popular languages, including BASIC, C,
                    232 parts on a variety of personal computers. The application               PASCAL and the Eke have either resident commands or readily
                    of this design philosophy is also applicable to other marine                available subroutines to access the RS-232 port.
                    instrumentation needs.
                                                                                                But why the interest in RS-232? Surely there are other
                              1. VIRTUAL INSTRUMENTS AND RS-232                                 schemes for moving data between an interface and a computer.
                                                                                                The following is a review of some of the data link options:
                    Since the beginnings of small computers, the advantages of
                    applying the power of these computers to instrumentation have               1. Processor bus - probably the highest data rate of all choices
                    been apparent. Gradually, the concept of using a small                      is available when going directly onto the data bus. This
                    computer together with a specialized interface and software to              method usually requires machine language code to support it.
                    construct an instrument has grown and acquired a name:                      It is the method used by "peripheral cards" such as analog-to-
                    "virtual instrument" (1). This name applies particularly to                 digital (A/D) converters. On the negative side, this method is
                    equipment where software has replaced major functions                       processor-specific and a device built for one family of
                    previously accomplished by hardware. This concept has                       computers will usually not operate with a different one; also,
                    particular import for oceanography because the numerical                    many computers (including "lap tops") do not provide access
                    quantities of equipment tends to be small in comparison to                  to the processor bus. Very little physical separation is allowed
                    many other fields of endeavour and the demands on the                       between a computer and a device on its processor bus (perhaps
                    equipment tends to be rather varied. The virtual instrument can             less than half a meter).
                    frequently satisfy these specialized requirements better and/or
                    more inexpensively than conventional hardware-only                          2. IEEE-488/GHIB/HPIB - IEEE-488 and GPIB (General
                    equipmem                                                                    Purpose Interface Bus) are synonyms for an 8-bit parallel
                                                                                                communications bus. HPIB (Hewlett-Packard Interface Bus)
                    One of the frequent frustrations of designing virtual                       was the precursor to IEEE-488 and differs in a few respects
                    instruments with early small computers was the problem of                   from IEEE-488. In many applications, the two are
                    connecting the specialized interface to the computer. A                     interchangeable. Data transfer rates up to one-half megabyte
                    Commodore "PET" computer had entirely different                             per second are possible. The interface has a reputation for
                    requirements from a Radio Shack "IRS-80". Frequently, the                   being difficult to implement for both hardware and software.
                    processor bus was the only connection available and machine                 Hardware design has been simplified to some degree with
                    code was almost always required to access devices on that bus.              specialized integrated circuits. Relatively few computers
                    Different processors made the machine code and hardware                     provide a "native" IEEE-488 interface. The simplest way to
                    different for each computer. Even connectors were different.                implement the computer-side of the interface is to purchase a
                    'Mere was no such thing as a "standard interface".                          commercial product; this Emits implementation to computers
                                                                                                with "expansion slots". Separation between computer and
                                                                                                devices on the IEEE-488 bus is limited to 20 meters without a
                       Contributions by:                                                        repeater.
                       Dr. James Wagner
                       Dr. Roderick Mesecar, Head                                               3. HPIL - (Hewlett-Packard Instrumentation Loop) is a serial
                       Technical Planning and Development Group                                 loop initially intended to provide a simple interface to pocket

                                                                     CH2585-8/88/0000. 518       $1 @1988 IEEE

                  calculators. Outside of a few Hewlett-Packard calculators and
                  computers, this system does not appear to be widely used.
                  4. LAN - (Local Area Network) comes in a variety of styles                                             Sigral
                  including Ethernet, STARLan, and others. Data rates can                                Serisor(s)   Conditiordrg        AID         U                 Host
                  exceed 1 megabittsec over distances up to 500 meters (2). If                                                                                         Cornput!r
                  simple communication between two only points is needed, the
                  hardware overhead can be rather high. Software, especially at
                  the computer side of the connection, is commercially available.
                  Access is generally limited to computers with "expansion                                                  ................... ControUer
                  slots" for the LAN interface cards.

                  5. RS-232 - this is a duplex serial system with control lines.
                  It is best suited from point-to-point communications between a
                  single pair of devices. Usually, each end of an RS-232 line
                  requires receivers and transmitters which convert between 5
                  volt logic levels and RS-232 levels. Each end also requires
                  UART (Universal Asyncronous Receiver-Transmitter). These                                       Figure 1. Virtual Instrument Block Diagram
                  devices are readily available and are frequently included in
                  many small computers. Data rates are commonly limited to
                  19.2 kilobaud (about 2000 8-bit characters per second). 'Me                         Note that there is no requirement that the specialized interface
                  maximum recommended length of an RS-232 link is 15 meters                           be connected a computer at all times. A case in point is the EG
                  with longer distances permitted at lower data rates or reduced                      & G Inc. Vector Averaging Current Meter. These instruments
                  load capacitance. When an RS-232 port is included in a                              are used by sending sampling parameters to the meter via an
                  computer, software to access the port is usually included in the                    RS-232 link, then disconnecting the meter and placing it into
                  operating system.                                                                   use. During measurement, data is stored in a local memory.
                                                                                                      At some later time, the meter is reconnected to the computer
                  6. Current loop - here is a system very much like RS-232. It                        and data is transferred from the meter's memory to the
                  differs only in the electrical characteristics of the link. It is a                 computer. Processing and display then occurs within the
                  simplex serial system using current rather than voltage for                         computer. This is again a virtual instrument but one in which
                  signaling. No control lines are used. Maximum data rates are                        the data collection is carried out disconnected from the
                  lower than RS-232 and are frequently in the 1.2 kilobaud.area.                      computer.
                  Noise immunity is good.
                                                                                                                             11. AN XBTE*4TERFACE
                  7. RS-422 - this system is also very much like RS-232 and
                  differs only in the electrical characteristics of the link. It is a                 An example of a virtual instrument for oceanographic
                  duplex serial system. It utilizes differential signal lines (for                    instrumentation which will be considered in more detail is an
                  noise immunity) which can default to RS-232 when connected                          XBT (eXpendable Bathy-Thermograph) interface designed at
                  in a certain way. Protocol is the same as RS-232. Interface                         Oregon State University by the Technical Planning and
                  cards for some computers are available.                                             Development Group of the College of Oceanography.
                  With all of these possibilities, how is a choice to be made? If                     This interface is made, to operate with the standard XBT probe
                  there is only one to be produced,,then the choice will probably                     and launcher produced by Sippican Corporation. It provides
                  be. what-ever fits equipment on hand while meeting other                            sensor excitation and analog signal conditioning appropriate to
                  requirements such as data rate. But if there are to be many                         the sensor. A digitizer converts analog voltage signals into
                  built for wide distribution, the answer is probably RS-232.                         digital numbers. Sample rate and other characteristics are
                  The reason is fairly simple: implementation cost is low and it is                   programmed into the interface by the host computer. Data is
                  supported in a wide variety small computers. While computer                         stored in the interface and transferred to the host after the
                  programs to support a specialized interface on an RS-232 port                       measurements have been completed. An 8-bit microprocessor-
                  may not be transportable at the compiled-code level, programs                       based controller containing an EPROM interprets commands
                  at the higher-level source codes usually are transportable with                     from the host and schedules operation of the interface. The
                  most of the required changes occurring in instructions which                        interface is fairly simple, fabrication costs are low and the
                  generate displays.                                                                  design was carried out quite quickly.

                  The impact of these factors on oceanographic instrumentation                        For maximum portability to ease placement of XBT equipment
                  is fairly significant. It leads to a virtual instrument which uses                  aboard ships-of-opportunity, the interface is tailored to operate'
                  a computer and an RS-232 link to connect to a specialized                           with some of the newer "lap-top" computers of the "PC-
                  interface. The interface usually contains some analog sensor                        compatible" type (Toshiba, Zenith, and others). It occupies an
                  excitation and signal conditioning, an analog-to-digital                            enclosure 12" square and 3" thick which is close to the size of
                  converter, a serial data port, and some type of controller. The                     most lap-tops. Figure 2 shows the XBT interface with a lap-
                  controller may be implemented as a simple state-machine if the                      top computer. Operation is possible with any computer having
                  required tasks are very simple. More likely, however, one of                        an RS-232 port, however. Communication between the host
                  the simpler 8-bit microprocessors will be used; for simplicity                      and the interface is via an RS-232 link for the reasons
                  and ease of implementation, the choice is often a                                   previously outlined. Virtual instrument software is written in
                  microprocessor which contains its own ultra-violet erasable                         BASIC which is fully adequate in execution speed with the
                  read-only memory (EPROM). Other choices might be made if                            possible exception of "bathy message" processing. The bulk
                  low power is special concern. The almost universal block-                           of the program was written in about five days with some fine
                  diagram of such a virtual instrument is shown in Figure 1.                          tuning requiring additional time later.
                                                                                                                                   qeD:
                                                                                                                                   ..........                  L

                                                                                                519

                     I           `I-IMOM!'n
                                                                                               There are other controlling characters which may be sent
                                                                                               between the host computer and the interface. For example,
                                                                                               the host computer can send an "M" (memory status) to the
                                                                                               interface. If the interface has unread data, it responds with "P
                                                                                               (full); if there is no unread data, the response is "E" (empty).
                                                                                               Similarly, the host computer may send characters to set the
                                                                                               sample rate, change the serial link baud rate, or reset the
                                                                                               interface controller. The interface also provides a software-
                                                          M" N
                                                                                               controlled data switch allowing one host computer serial port
                                                                                               to drive either the XBT interface or serial satellite transmitter
                              J
                   J."N",2,
                              H F.J@                                                           port on the interface.

                                                             ME                                In a virtual instrument, there are two sets of specifications.
                                                                                               One includes the performance of the specialized interface.
                                                                                               These specifications establish boundaries to the system
                                                                                               performance which programming wizardry is not likely to
                                                                                               circumvent. The second set outlines the system performance
                                                                                               utilizing provided software. Table I gives interface
                                                                                               specifications for the XBT interface while Table H gives the
                                                                                       U       specifications of the complete XBT systen-L
                            Figure 2.  XBT Interface with lap-top computer                                   Table 1 - XBT Interface Specification
                   Design of a virtual instrument requires careful consideration of                     * Sample Rate: 1, 2, or 4 per second programmable
                   how tasks are to be partitioned between the host computer and                        * Sample capacity: 1009 samples
                   the specialized interface. The design of the XBT interface was                       * Resolution: 0.05' Centigrade
                   no exception. An example is the test which the interface does                        e Accuracy: 0.10* Centigrade
                   prior to each probe drop. The numbers obtained help gauge
                   the operation of the interface and are used in the conversion of                     o Serial host interface: RS-232
                   the A/D output to temperature. A decision had to be made                             * Serial baud rate: 300 to 9600 baud, programmable
                   concerning which unit, host computer or interface, was to
                   determine acceptability of test results. That responsibility was                     o Serial data control: XONIXOFF
                   assigned to the host computer so that the test criteria could be                     & Satellite port: switchable by host
                   more flexible than if contained in the interface controller's                        9 Satellite baud rate: 300 to 9600 baud, programmable
                   EPROM.
                                                                                                        9 Interface testing: built in
                   Another aspect of virtual instrument design is the protocol                          * Launch detection: built in
                   chosen for exchanges between the host computer and interface.
                   Brevity and lack of ambiguity ease decoding at both ends.
                   Completeness insures that all probably situations can be
                   handled. The interchange protocol between the host computer                                    Table H - XBT System Specifications
                   and the interface is best described by following the sequence of
                   operations during a probe launch. Normally, the empty probe
                   canister is kept in the launcher until just before the next drop.                    e Host: Zenith or Toshiba "lap-top"
                   The interface senses when the canister is removed and sends                          e Operating Sys   tem: MS-DOS 3.0
                   an ASCII "C" to the host computer. The interface
                   automatically begins the self-test procedure; when the test is                       * Language: BASIC
                   finished, the interface sends the A/D output values from each                        * Floppy disk drives: dual 3.5" required
                   test step to the host computer. The AID is a 12-bit converter                        * Data storage: all samples stored as temperature and
                   and each output value is sent as three hexidecimal values in                           depth
                   ASCII. The host computer verifies the test values and if they
                   are acceptable, sends an ASCII "G" (go) to the interface. At                         0 Data display: temperature vs depth graph (operator
                   the same time, an operator message indicates readiness for a                           optional)
                   new probe canister and the next launch. When the probe is                            e Additional processing: significant profile points
                   launched, the interface sends an ASCII "L" (launched) to the                           (operator optional)
                   host computer and begins sampling at the rate specified earlier                      e Bathy message: screen display and disk storage
                   by the host computer. Sampling continues until the interface                           (operator optional)
                   either reached the end of available memory space or receives
                   from the host computer an ASCII "E" (end). When the host                             * Satellite message: Suited to user requirements.
                   computer is ready for the data, it sends an ASCII "D" (data) to
                   the interface. 'Me interface responds by returning the data
                   using three hexidecimal characters (sent in ASCII) per sample.
                   K necessary, the data flow can be interrupted by the host
                   computer by sending "XOFF" (ASCII ctl-S or DC3) and                         Host computer software handles operator displays, movement
                   resumed by sending "XON" (ASCH cd-Q or DC1). The host                       of control information to the interface, movement of data from
                   computer processes the data into the desired form, then waits               the interface, conversion of data from arbitrary A/D units into
                   for the signal from the interface that the one empty canister has           temperature units and from saffi ple time into depth, storage, of
                   been removed for the beginning of the next launch.                          depth and temperature data, graphic display of temperature vs

                                                                                          520

                  depth, compression of a temperature-depth data set into
                  standard World Meteorological Organization (WMO) bathy-
                  message, formatting the bathy-message (if desired) for satellite
                  transmission, and, finally, (if desired) movement of
                  compressed data to a satellite transmitter. Since the host
                  computer software is accessible to any user who knows
                  BASIC, it is easy to change, for example, operator interface
                  displays, processing algorithms or data formatting rules.
                  Additional functions may be readily added. These might
                  include temperature limit alarms, mixed layer depth
                  determination, or identification of profiles leading to certain
                  sound transmission characteristics.

                  Note that these functions are independent of the host computer,
                  operating system, or programming language. While the
                  provided implementation runs under MS-DOS 3.0 on Zenith or
                  Toshiba lap-tops, many of the functions have also been
                  implemented on an HP-85.

                  While few details of the interface have been provided, it should
                  be sufficient to say that the design for sensor excitation and
                  signal processing is taken from one of our existing designs (3)
                  and includes about 8 analog integrated circuits (I.C.s) and
                  some discrete parts. The digitizer is a single I.C. and includes
                  some discrete parts. Two digital I.C.s are used to control the
                  analog circuitry. The interface controller is an 8748
                  microprocessor with an additional 2K of memory and a few
                  logic I.C.s. The RS-232 port includes a UART and a receiver-
                  transmitter.

                  Four of the systems described have been constructed. Several
                  are undergoing initial sea-tests at the time of preparation of this
                  paper. Initial results appear to indicate that the specifications
                  of Table I have been met. Two of the interfaces have been
                  built with battery-backup so that operation is possible while
                  separated from the host computer and line power.

                                             III. SUMMARY

                  The idea of a virtual instrument has been explored. The
                  problem of how to move data between a host computer and the
                  specialized interface was discussa If use with the greatest
                  variety of host computers is a goal, then RS-232 would seem
                  to be the interconnection method of choice. An XBT interface
                  is described as an example of how these ideas can be applied to
                  the unique requirements of oceanographic instrumentation.

                                              REFERENCES

                  1.  Fitzgerald, K. Instrumentation, IEEE Spectrum 25 (1),
                      Jan 1988, 47-49.
                  2.  Stix, G. Telephone Wiring: a conduit for networking
                      standards, IEEE Spectrum 25 (6), June 1988, 38-41.
                  3.  Mesecar, R. and J. Wagner. An XBT Digital Recording
                      and Display System. OCEANS 1979 Conference,
                      September 1979, 598-601.

                                                                                        521

                                                                HYDROBALL - A NEW EXPENDABLE:
                                                                              USES AND ISSUES

                                                                                      H. Tremblay

                                                                             NewTech Instruments Limited
                                                                               P.O. Box 13635, Station A
                                                                                St. John's, NF, Canada
                                                                                        A1B4G1

                                             ABSTRACT                                         i - The Eulerian method - measures simultaneously the
                                                                                              direction and speed at fixed points, and;
                    Early in 1988 the HYDROBALL Ocean Current Profiling System,
                    under development since 1985, was introduced to the                       ii - The Lagrangian method - measures the water move-
                    marketplace by NewTech Instruments Ltd. The HYDROBALL                     ments by tracing a path of a water particle over a longer
                    System is a transportable, easy to operate, low-cost expendable           time interval.
                    current and temperature profiling system which operates from
                    stationary platforms and moving vessels in water depths up to             The commercial products existing at the time used one of
                    500m.                                                                     two technologies to derive current speed and direction
                    The HYDROBALL System uses an expendable Lagrangian                        throughout the water column: cloppler measurements of
                    drifter, spherical in shape, which houses an acoustic transducer,         acoustic waves reflected from particles suspended in the
                    pressure sensor, thermistor and timing electronics. The un-               column (RD Instruments Doppler Current Profiling Sys-
                    tethered, free-falling drifter transmits data hydroacoustically as it     tem), and measurements of the electrical current generated
                    descends through the water column. The changing range and                 bythe motion of seawaterthrough the earth's magneticfield
                    depth of the drifter, aswell as its azimuth with respectto the ship's     (Sippican Ocean Systems Inc. Current Profiling System).
                    heading, are detected by an ultra-short-baseline phased array
                    hydrophone, and converted to digital data by a signal analyzer.           After researching these and other potential technologies, it
                    Adedicated microcomputer calculates flow velocity components,             was decided to use a direct, physical method of current
                    as well as temperatures, at regular depths throughout the drop.           profiling - monitoring the movement of a free falling Lagran-
                                                                                              gian drifter in three dimensions, and using the resultant data
                                                                                              to extrapolate current speed and direction along the path
                                        1. INTRODUCTION                                       of descent.

                    The potential benefit of absolute real time current profiles              It was determined early in the development cycle that
                    used in support of offshore operational activities has only               hydroacoustics would be a reliable and cost-effective
                    recently been identified as a long term growth market for                 method of tracking the path of the probe. The use of
                    manufacturers of oceanographic equipment [1]. The sur-                    hydroacoustics would also allow the transmission of sen-
                    vey identified several sectors which could derive tangible                sor data from the descending probe.
                    benefit from absolute current profiles obtained prior to un-
                    dertaking sub-surface activities. The applications identified             The completed system consists of an expendable probe
                    included uses in manned diving and remotely operated                      (the HYDROBALL), a hydrophone, and shipboard
                    vehicle operations, drilling unit positioning, dredging and               electronics. The data acquisition process is shown in
                    dump site management, and tactical ice management                         Figure 1.
                    programs in support of offshore drilling.
                                                                                                          2. PRINCIPLE OF OPERATION
                    In 1985 National Petroleum and Marine Consultants Ltd.,
                    of St. John's, Newfoundland, Canada, undertook the                        The HYDROBALL System operates on the principle of cal-
                    development of a current profiling product which would                    culating a current velocity profile from the dynamic
                    meet the requirements identified. The objective was to                    response of a freely falling object [3,4,5]. The development
                    develop a cost-effective, easy to use technology that could               of the product began with the construction and verification
                    reliably measure significant currents in near real time.                  of a numerical model to determine the dynamic response
                                                                                              of a spherical probe of known physical characteristics (Fig.
                    In general there are two methods of measuring water move-                 2) [6]. Both theoretical and field research demonstrated a
                    ments (currents) [2]:                                                     predictable dynamic response of the HYDROBALL probe.

                                                                    CH2585-8/88/0000- 522       $1 @1988 IEEE

                                                                                     rate of 1.024 Hz. Because the HYDROBALL probe is
                                            Analog to                                calibrated to fall at a constant vertical velocity of ap-
                                            Digital                                  proximately 0.36 m/sec., the effective resolution of the sys-
                                            Circuit                                  tem is approximately three measurements per metre.

                                                                                     Navigational information, including ship's heading and
                                         +                                           speed (for moving vessels), is input manually by the
                                                                                     operator. Corrections for changes in heading during the
                                                                                     descent of the probe are input through a direct electronic
                  Probe                                                              connection to the vessel's gyrocompass.            In practice,
                                        4                                            moving vessel profiles are undertaken at a speed of ap-
                                                                                     proximately two knots, with vessel heading and speed
                                                                                     maintained throughout the profiling operation. An addition-
               FIGURE 1. The HYDROBALL Current Profiling System hydroacoustic        al verification of the profile data is established by continu-
               data acquisition system.                                              ing to collect data from the probe for several minutes after
                                                                                     it has reached the seabed.
               The results of this theoretical study were used to guide the          During the profiling operation the incoming data is dis-
               development of Inverse Dynamics Analysis (IDA) algo-                  played to the operator in numerical form in real-time. The
               rithms. The IDA algorithms are used to express the                    incoming data is processed by the IDA algorithms to
               hydrodynamic relationship between the response of the
               sphere to flow velocities in a given horizontal field, and the        produce current and temperature profiles in near-real-time.
               actual current speed.                                                 The data is stored to disk for later analysis, printing or plot-
                                                                                     ting.
               Tracking the expendable sphere requires the resolution of
               its position in 3D space at regular time intervals as it des-         The HYDROBALL System is designed to operate in water
               cends through the water column, The technique involves                depths of up to 500m., with a maximum range between the
               the determination of probe range, depth and azimuth, rela-.           probe and the hydrophone of 1500m.
               tive to the hydrophone. The completed system uses three
               techniques to determine positional information.                                               3. TESTING

               The range of the-probe is determined by measurement of                Throughout the development the HYDROBALL System
               the time delay of incoming probe signals due to the speed             was tank tested at the Acoustics Laboratory facilities at
               of sound in water. A precision electronic. clock in the ship-         Memorial University of Newfoundland and at the New-
               board electronics package is synchronized with a similar              foundland and Labrador Institute of Fisheries and Marine
               clock in the probe prior to deployment. Astherangeofthe
               probe from the hydrophone increases, the time delay of in-
               coming signals versus the synchronized clock pulses is
               measured and the range calculated.

               The depth of the probe is measured by a pressure
               transducer housed in the expendable. Data from the
               transducer is converted to digital form, and transmitted
               using pulse position modulation of the hydroacoustic sig-
               nal.

               The  measurement of the azimuth of the probe relative to
               the hydrophone is made possible by ultra-short-baseline
               phased array hydrophone. The measurement of small
               changes in the phase of incoming signals as they pass over
               the three-element array allows an accurate determination                                          A,
               of azimuth.

               In addition to establishing probe position, the system also
               recognizes and decodes data from a thermistor built into
                                                                                                                         -V
               the probe, and uses the incoming data to produce a simul-
               taneous temperature profile.

               The probe emits range, depth and temperature signals at
               three distinct frequencies (27, 26, 25 kHz.) at a repetition          FIGURE 2. The HYDROBALL expendable probe.

                                                                                523

                                               HYDROBALL SIPPICAN DOPPLER
                                                TWO VELOCITY COMPONENT ANALYSIS
                                                 SHIP: COLUMBUS ISELIN FUZ NAME: MIAM13
                                           LAN: 25.46.5.N LONG: 80,03.4.W 12-AUG-88 14:58:23

                         200--                                                                                        LEGEND

                         180--                                                                                                 HYDROBALL N-S

                         160--                                                                                                 SIPPIOM N-S

                                                                                                                      .......  DOPPLER N-S
                         140--

                                                                                                                               HYDRORA-1 W-E

                         120--
                                                                                                                      .......... SIPPICAN W-E

                     rn 100--
                                                                                                                      --- DOPPLER W-E

                          so--

                          60--

                          40--

                          20 . . .........

                                                                            .............. ...........
                           0.

                         -20                                                                  i i     i      i i
                               10                                                                             165
                                                                   DEPTH
                                                                       M

                FIGURE3. HYDROBALL      Sippican /Doppler field data.             was felt that the most practical method of demonstrating
                                                                                  the accuracy and function of the system would be to ar-
                Electronics. These facilities were used to determine the          range comparative, simultaneous trials with two other near-
                hydroacoustic properties of a variety of transducer               real-time profiling systems.
                materials, constructions and assemblies for both the
                hydrophone and the HYDROBALL probe.                               On August 12, 1988, NewTech Instruments Ltd., the
                                                                                  manufacturers of the HYDROBALL System, arranged for
                In the absence of a suitably large testing facility that could    the charter of the research vessel ORV Columbus Iselin
                simulate current shear and representative water column            from the University of Miami, to obtain comparative current
                depths, open-water testing was conducted. A prototype             measurements in the Gulf Stream. The vessel was out-
                hydrophone and a supply of probes was manufactured and            fitted with an acoustic Doppler Current Profiling System
                the system was installed on an inshore fishing vessel for         manufactured by RD Instruments Ltd., San Diego, CA, an
                field trials. The field program also included the use of          MK-10 current profiling system manufactured by Sippican
                moored current meters and a three-point shore-based               Ocean Systems Inc., Marion, MA, and the HYDROBALL
                navigation system as a means of data verification. In sub-        System. Third-party personnel were responsible for the
                sequent trials the system was installed on an offshore            operation of the doppler system (University of Miami per-
                anchor handling supply vessel, and tested on the Grand            sonnel) and the XCP system (Shell Development Com-
                Banks offshore Eastern Canada.           I                        pany).

                Although these tests provided some comparative data, al-          At the time of preparation of this paper the data from the
                lowed the construction of mathematically generated data           three systems was still undergoing detailed numerical
                sets for software testing, and ensured that the measure-          analysis; however, a preliminary examination of the results
                                X

                ment methods and equipment were functioning properly, it          (Fig. 3) suggests that the three instruments were produc-

                                                                               524

                ing data sets with a high degree of correlation. A tempera-           extrapolate current speed and direction from the motions
                ture profile from the same HYDROBALL probe is shown in                of the drifter.
                Figure 4.
                                                                                      The HYDROBALL System has been demonstrated as a
                A full report on the testing results will be available from the       practical alternative to profilers using other technologies.
                author at time of publication.
                                                                                                   5. ACKNOWLEDGEMENTS

                                   Wer TeNperdture ('--- C.)                          The development of the HYDROBALL System was funded
                                                                                      in part by the Government of Canada's Department of
                                                                                      Regional Industrial Expansion Ocean Industries Develop-
                                                                                      ment Program, and through the Industrial Research Assis-
                             20                                                       tance Program of the National Research Council of
                                                                                      Canada. Additional technical support was provided by
                                                                                      Memorial University of Newfoundland and by the New-
                             40                                                       foundland and Labrador Institute of Fisheries and Marine
                                                                                      Technology.

                                                                                      The author also wishes to thank Mr.George Z. Forristall of
                                                                                      the Offshore Engineering Research Department, Shell
                                                                                      Development Company, the University of Miami and the
                             80                                                       Husky Oil East Coast Project for their participation in the
                                                                                      testing program.    6. REFERENCES
                           W
                                                                                      1.Omnifacts Research Ltd. (1985), "Market Survey for Cur-
                                                                                      rent Profiling Systems", National Petroleum and Marine
                           120                                                        Consultants Ltd. Internal Document, St. John's New-
                                                                                      foundland.

                           140                                                        2.Neuman, G. and Pierson, W.J. Jr. (1966), "Principles of
                                                                                      Physical Oceanography," Prentice-Hall Inc.

                           160                                                        3.Rossby, H.T. (1969), "A vertical profile of currents near
                                                                                      Plantaganet Bank", Deep-Sea Research, Volume 16, pp.
                                                                                      337-385.
                           180                                                        4.Pochapsky, T.E. and Malone, F.D. (1972), "A vertical
                                                                                      profile of deep horizontal current nearCape Lookout, North
                                                                                      Carolina,"Journal of Marine Research, Volume30, pp. 163-
                                                                                      167.
                                    6.0     12.0 18.0 24.0                            5.Luyten, J.R. and Swallow, J.C. (1976), "Equatorial Under-
                                                                                      currents", Deep-Sea Research, Volume 23, pp. 999-1001.
                FIGURE 4. HYDROBALL temperature profile from the field test il-
                lustrated in Figure 3.                                                6..Npmc i;ii,. (1985), "Numerical analysis of the dynamic
                                                                                      response of the HYDROBALL due to wave condition and
                                                                                      current velocity profile", National Petroleum and Marine
                                   4. CONCLUSIONS                                     Consultants Ltd. Internal Document, St. John's New-
                                                                                      foundland.
                The HYDROBALL Current Profiling System has
                demonstrated in laboratory and field trials the validity of
                using hydroacoustic tracking of a Lagrangian drifter to
                measure current speed and direction in water depths up to
                500m@

                The IDA algortihms used in the system software have, in
                comparative testing, demonstrated the ability to properly

                                                                                 525

                                                SHIPBOARD TACTICAL COMPUTER

                                The Coast Guard's Combat Information Center Modernization

                            Lcdr Rex A Buddenberg USCG and Lt Andrew Givens USCG
                            Commandant (G-TES-1)                commanding Officer (cs)
                            US Coast Guard                      USCG Electronics Engineering Center
                            Washington, DC                      Wildwood, NJ

                                                                 II. REQUIREMENTS
              ABSTRACT
                                                                       Assembling definitive requirements
                    We chronicle the motivations,                for a modernized CIC has turned out to be
              architecture and development of a                  a nearly insoluble problem. The first
              modernization of information handling in           aspect is that articulation of existing
              Combat Information Centers aboard Coast            requirements for a high intensity law
              Guard Cutters. The mission requirements            enforcement/low intensity conflict
              are specialized for Coast Guard                    application is not an easy task.
              applications, but the solution is being            Secondly, the rapid mission evolution
              fabricated from general purpose industrial         experienced by the Coast Guard in the past
              and defense components.                            decade means that whatever requirements
                                                                 stated now are destined to be obsolete by
                                                                 the time a system can be fielded to meet
                                                                 them. This problem of finding a solution
              I. THE PROBLEM                                     to a problem that isn't well stated has
                                                                 bedeviled us from the beginning.
                    Two classes of Coast Guard cutters                 Nonetheless, we found it quite
              have wholly manual CICs -- the WMEC 210            practical to perform some requirements
              and WHEC 378 classes. Indeed, a high               analysis once we understood requirement
              endurance cutter CIC at general quarters           #1: provide a flexible, growth-oriented
              resembles a college telephone booth                structure that is highly adaptable to the
              stuffing contest.    Despite the existing          varied and ever-changing Coast Guard
              situation, the information management              mission profile.
              tasks placed on these CICs is steadily                   We first examined what we perceived
              growing and now dwarfs the capability.             to be the 'growth' missions, particularly
              Additionally, the WMEC 270 class cutter            in their demands on our CH structure.
              has a considerable degree of automation,           These include air interdiction and surface
              but the close coupling of its architecture         law enforcement in peacetime and
              presents major problems in its evolution           continental shelf ASW and mine warfare in
              over the life of the hull.                         the wartime environment. In all these
                    As technology has placed a personal          cases, it is evident that cutters are
              computer on everyone's desktop, it has             components in a larger milieu and we could
              become obvious that the existing Combat            not confine our architectural thinking to
              Information Centers on our cutters can             within the hull. In particular, data is
              handle data in a much more effective               imported from external sensors and
              manner than they do now. Equally                   databases in all of these missions. This
              obviously, the Coast Guard does not have           data export aspect has a seminal impact on
              the budgetary or organizational means to           the communications subsystem requirements.
              reinvent solutions from the ground up.
              Unfortunately our vendor survey revealed
              that there does not exist a canned CIC             III. THE ORGANIZATIONAL ENVIRONMENT
              that meets both the wartime and peacetime
              Coast Guard needs.                                       This problem, and impetus to do
                    Consequently, we built the Shipboard         something about it, has appeared in a time
              Tactical Computer project around a clear           of budget and personnel shrinkage.      This
              understanding of our architectural                 presented us with the constraint of having
              requirements, and then a low risk                  to articulate the larger architecture,
              adaptation of existing technology to meet          then trim the problem to practical size
              them.

                                               CH2585-8/88/0000- 526 $1 @1988 IEEE

            without sacrificing the growth potential.             Similarly, we are unable to solve the
            This meant that notions of a 'do all'            external communications problems in the
            automation system that fully integrated          ship-shore-air network environment within
            ship control, tactical planning and combat       our present scope, but we are able to
            direction were impractical. The present          provide a well specified interface in the
            scope of the project has brought it within       cutter's communications center once this
            the capabilities of the three dedicated          area is addressed. The key is to
            project personnel.                               understand the internetworking
                  In our pruning of the project scope,       relationship between an intra-ship network
            we set into the future any requirements          and a ship-shore-air network.
            that fall under the aegis of the conning              Finally, by defining the immediate
            officer and weapons liaison officer in           problem as transporting data from sensors
            favor of automating the tactical decision        to a decision support system and providing
            support process. This confines the               the evaluator with an integrated displayr
            technical risk, provides the most payoff         we can capitalize on well understood
            in terms of crew workload and becomes a          technology.
            practical objective.

                                            Intel

            On board                                                                       Display
            Sensors                                    Identify
                            Acquire                    & Assess
                            targets
            Off board
            Sensors

                                                                               ssess
                                                                             Threat  &
                                                      Target  file
                                                                              Recommend
                                                                       Nell",II                  %I  % % %'1,%,%,V,
                                                                              Engagement
                                                                         % % % %

                                                                       .......           ....
                               % % %       % % % %%                                     % %     Control
                                                                                                Combat   &
                           % %
                           %    % %                    %                  % %
                           I I I I I I I I . III . I I I . I I I
                                                 , -@,"X'l             I I II%I%I%I
                                        APTOM01      Z, I "%            , , % %                 Weapons
                                        %
                                        %       I I I I . I . I I 1     11
                                                                                                systems

            Nav
                                   e/
                           Navigat                      llpp le                            I
            Senso
                           Maneuver                            &
                                                             r c e p t

                                                  I . I . I I I                            Analyze
                                                %I %I                                      & Display
                                  I I I I I I I I I I II

                             IN1,111I%
                                                                Track   file

                                             Automation Domain

                                                           527

               IV. C31 STRUCTURE                                    But first, how much survivabilty is
                                                               enough? We have set, as a working
                    The structure for automating certain       hypothesis, the requirement that the
               CIC functions does not change the data          network must be able to isolate any
               flow within CIC. Rather we concentrate on       damaged portions of the network so the
               replacing.manual communications (sound          remainder can continue to operate in the
               powered phones) and manual plotting (dead       event of a single combat hit (or a single
               reckoning tracer) with faster, less error-      ramming by a desperate drug smuggler or
               prone and less costly mechanization. The        single incidence of damage internally by
               Sense --> Decide --> Act cycle remains          fire or externally by ice).   In such
               fully intact and will be easily                 events, the damage control system in the
               recognizable to the operators using the         ship is likely to be effective and the
               system. And the decision making still           communications.network must be able to
               rests with the human operators, not the         support it. The second combat hit in a
               machinery; our modernization provides           Coast Gaurd cutter.renders the network
               computer assistance, not complete               survivability problem moot -- there won't
               automation.                                     be a ship left for the network.to operate
                                                               in.

                     Erin

                                    Automation Domain Boundaries

                                     The Command & Control Cycle

                    A. COMMUNICATIONS SUBSYSTEM                     An additional requirement was that
                                                               the network should be able to accomodate a
                    The intra-ship communications system       very wide variety,of communications
               that relies on sound powered phones and         applications aboard ship, not just the
               liberal application of Norwegian steam is       tactical data ones.   Examples include
               obviously inadequate. But this time-            logistic, administrative, and engineering
               honored practice has the attributes of          control data communications applications.
               being quite survivable and flexible.   How      This desire drives the solution strongly
               do you make the necessary upgrades in           in the direction of a LAN.
               capacity without reducing the existing                A final implicit requirement is that
               features? We knew we wanted a Local   Area      such a network must be affordable -- we
               Network (LAN) because it offered the            would have to meet the organizational
               promise of capacity, flexibility and            budgetary considerations mentioned
               abili0y to internetwork to other                earlier. And this constraint applies not
               communications nets, but existing               just to the initial configuration of the
               standards for networks lack the                 network, but would continue over the life
               survivability needed aboard ships.              cycle.

                                                            528

                                                             increased, Unix has essentially become
                 B. DISTRIBUTED COMPUTING                    real time as its sensitivity to data
                                                             requirements approaches that of a true
                 Once the survivability problem in      the  real time executive. This shortcoming is
            communications network is solved, the            far outweighed by the standardized,
            survivability aspect of the decision             general purpose nature of Unix and its
            support system becomes much easier to    deal    ready availability.
            with. The network can supply track data'
            to two or more computers as easily as it
            can to one. This allows us to use the                 D. APPLICATION SOFTWARE
            Coast Guard's proven-tactic of relaxing
            the individual component hardening                    Decision support software is probably
            requirements (with considerable cost             the most difficult area in which to obtain
            savings) and installing more than one            articulate requirements from users or
            (much more economical than it looks at           resource sponsors. Additionally, it is
            first -- the logistics pipeline doesn't          obvious that we-will not have the
            need to be duplicated). We've done this          resources to specify, assemble or maintain
            successfully throughout the service with         a significant software product within the
            navigation receivers, radars, and radios;        Coast Guard. Therefore, we have mounted a
            we can do it with tactical computers as          concentrated, continuing effort to locate
            well -- within the budgetary constraint.         software products already in development
                 We can today purchase and send to sea       or use in other services. Since the
            tede a tactical computer that exceeds our        taxpayers have already paid for the
            ability to tax it. Indeed it is generally        software, we see no reason why we should
            economical to provide about twice the            duplicate the expense.
            horsepower that the forecasted                        This intelligence effort is very
            requirements indicate because of the low         interesting, and usually unorthodox.; the
            cost of hardware compared to high cost of        military services do not answer requests
            squeezing ten pounds of software into,,a         for information in the Commerce Business
            five pound bag.                                  Daily. No central clearing house exists
                                                                leads,have come from thelold-boyinet,
                                                             symposia, contractors (yes, most of them
                 C. SOFTWARE FLEXIBILITY                     are quite ethical) and general 'big ear'
                                                             habits of listening. And like any
                 We wanted very much to avoid                intelligence work, the raw data that comes
            constraining ourselves to a single               in is random, and a large part of it
            software package. Similarly, our ever            unusable. But we have identified a few
            present budgetary constraint argues.very         usable and suitable packages.
            strongly toward use of an existing package
            already owned and supported.by the
            government rather than creation and.
            support of a custom package -- assuming we       V. COMMITMENT TO OPEN STANDARDS
            can find one. So the software
            requirements drove the computer hardware              Permeating the entire structure of
            choices to open standards. A color               the project, including out-year.
            graphics workstation.running the Unix            expansions, is our committment to open
            operating system and supporting open             system standards and layered, flexible
            graphics (Programmers Heirarchical               architectures. This is our hedge against
            Interactive Graphics - PHIGS or Graphics         obsolescence, our.guarantee of
            Kernel - GKS) and database standards             interoperability, and our means to
            (Structure Query - SQL) is our choice.           integration without the close coupling
            Many software packages either are  ' or soon     that stifles growth.
            will be, available off-the-shelf and we               More specifically in communications,
            can preserve.our ability to choose an            this means employment of the International
            appropriate package or packages and change       Standards Organization layered
            them as the mission requirements change.         architecture model, and use of the
                 Unix provides the best tradeoff             Government'Open Systems.Interconnect
            between availability and standardization,        Profile standards in its execution.
            cost, flexibility, and real-time                      This overriding desire to preserve
            performance. Unix is not 'real time' in          flexibility is embodied in use of the Unix
            the sense of being event driven. But its         operating system for the decision support
            scheduled, time slice task managementy           workstations. -Since we are obtaining
            particularly in a high performance               turnkey decision support software, the
            environment characteristic of todays             language it is written in is not directly
            workstations comes close enough   to a true      relevant. liowever, anything not written
            real time operating system that we are           in C, Ada or another high level, machine
            within the performance envelope that we          independent language was nearly
            need. As task switching speeds have              automatically ruled out.

                                                           529

                   And in data formats, we are planning       VI. ENUMERATING THE SOLUTIONS
              to use those prescribed in JCS Publication
              25, the JINTACCS message formats for                 Once we had charted the requirements
              anything new we must generate. More on          carefully, the search for solutions
              this subject in the system integration and      yielded to the concentrated search effort
              the Presentation Layer Pre-Processor            we Coasties are trained for. our search
              function below.                                 patterns didn't exactly conform to those
                   Cartographic standards also hold a         in the SAR Manual, but they turned out to
              promise of improved chart presentation in       be effective enough.
              the future. Most current workstation-                The Navy's Survivable Adaptable Fiber
              based decision support systems generally        optic Embedded Network (SAFENET)
              use World Database points (from Defense         standardization effort will meet all the
              Mapping Agency) to create on-screen map         intra-ship communications requirements and
              representations. A few simply use a             more. SAFENET's emphasis on multi-vendor
              digitized representation of a paper chart.      interoperability promises a long.term
              These representations are deficient for a       growth path. We have been participants in
              variety of applications due to the lack of      this standardization effort for about a
              detail. Our decision support software           year and a half at this writing and are
              criteria include a desire to replace the        starting to glimpse the promise of
              current cartographic database with the          deliverable hardware.
              Electronic Chart Display and Information             A suitable graphics workstation was
              System being standardized by RTCM for           located in the Navy's Desktop Tactical-
              digital chart displays as that standard         support Computer-II which is in the
              matures and products become available.          contracting process at this writing. Our
                                                              Navy colleagues were happy to include the
                                                              Coast Guard as optional buyers,off their
                                                              open contract.

                                                     Architecture

                                                   Implementation

                           n't (D T

                                 Implementation of the Decision Cycle

                                                           530

                 We have lined up at least one              VII. DEPLOYMENT AND CONCLUSIONS
            software package at this writing that has            The past year has been spent largely
            been in use in the Navy for a few years         in surveying the marketplace,
            and is currently undergoing a major             troubleshooting our architecture,
            rebuild to remove exactly the hardware          eliciting user feedback and observing and
            dependencies that worry us and to meet  the     aiding the maturation of several products,
            general purpose requirements needed for         and lining up contractural and logistic
            growth and maturation.                          vehicles. This writing marks the occasion
                                                            of a turning point in our project.
                                                                 The coming year's plans consist
                 A. INTEGRATION                             primarily of assembling a shore based
                                                            mockup using the above described
                 The final identifiable component is        components and existing sensors in common
            glue. Most of todays critical sensors in        Coast Guard use. With a bit of fortune,
            the Coast Guard's inventory, such as the        the project will see a workable,
            surface search radar, navigation receivers      deployable, and supportable structure in
            and visual sighting reports have some sort      about a year. This Block One will replace
            of native digital output, but it isn't in       the existing hardware in the surface
            a format understood by the decision             warfare/surface law enforcement/search &
            support software.  Similarly, imported          rescue module in our cutters starting in
            track reports come in a variety of formats      about a year.
            most of which need translation.                      Expansion to the Anti-Air Warfare and
                  In some cases, particularly over the      Anti-Submarine Warfare modules in CIC and
            long run, the problem can be solved by  re-     incorporation of modernization of conning
            educating sensors to provide data in a          functions on the bridge and communication
            correct format.  In the nearer term, a          functions in radio central are all future
            track report translater function will have      growth areas fully accounted for in the
            to.be provided. This function, which we         architecture.
            have termed a Presentation Layer Pre-
            Processor, can run.as a separate process
            on the multi-tasking decision support           VIII. THE PAYOFF
            computer, or on a separate machine on the
            LAN, or as a distributed function at each            At the moment, the half dozen crewmen
            of the LAN interface points.    Specific        manning the surface warfare module in CIC
            implementation decisions in this area will      during general quarters become swamped
            remain one of the major work items in the       with more than a dozen active contacts to
            project in the coming year. Fortunately,        account for. This expansion should
            this is the only real development work          provide a track capacity about two orders
            that we must do -- all other parts of our       of magnitude larger. Conversely, the
            system have been imported from other            efficiency payoff is that the job will be
            sources without the burden of reinvention       performed about half as many crewmen.
            or customization.                               Similar manpower efficiencies will be
                                                            realized as we expand into the other CIC
                                                            modules.

                                                        531

                                                  NETWORKING AND SHIP-TO-SHORE SIUP-TO-SHIP COMMUNICATION

                                                                                      Ronald L Moe

                                                                           Shipboard Computer Group, A-023
                                                                          Scripps Institution of Oceanography
                                                                                La Jolla, California 92093

                                                ABSTRACT                                           fleet and the shore based station; and how we have
                      This paper discusses shipboard communication as it applies                   attempted to utilize them in networking schemes.
                      to computer networking between ships and the shore facili-                                         SFHP-TO-SHORE
                      ties at the Scripps Institution of Oceanography. Different                   Since the early days, the primary means of ship-to-shore
                      communication links are discussed including satellites and                   communication has been radio-teletype (RTTY) or high
                      VHF (high frequency radio). Further detail is given relat-                   frequency voice (VHF). Radio-teletype is sometimes the
                      ing to the networking options aboard ships and at SIO                        only communication path available because of distance,
                      while pointing out some of the advantages, disadvantages,                    atmospheric conditions, etc. Since it is slower and less
                      and limitations of the different systems.                                    flexible than voice communication, voice is the preferred
                                            INTRODUCTION                                           method to communicate.
                      Communication between the shore facilities at the Scripps                    Approximately ten years ago, satellite communication
                      Institution of Oceanography (SIO) and the ships in our fleet                 became available to the oceanographic community. NASA
                      has always been a necessity. The need to communicate                         had two transponder relay satellites that were -originally
                    .may be for ship's personnel to have contact with the                          VHF communication experiments. NASA wanted to deter-
                      Marine Facilities or for scientists to be able to pass mes-                  mine the reliability of VHF communication with the satel-
                      sages to SIO or to their own institutions if they are not                    lites. The results from the experiment showed that VHF
                      affiliated with SIO. Members of the scientific party are                     communication was not very reliable. The satellites had
                      usually made up from many diversified groups, such as                        served their intended purpose and were no longer being
                      scientists and technicians from SIO or other institutions                    used. Access to the satellites by the ocean      'ographic com-
                      both in the U. S. and abroad, as well as observers from                      munity was allowed by NASA for communication pur-
                      foreign countries if survey work is done in their territorial                poses. The satellites are referred to as ATS-1 and ATS-Ill.
                      waters. The larger of the ships can be anywhere in the                       Both satellites are in geosynchronous orbits and appear to
                      world with the associated problems of long distance com-                     remain stationary in the sky if the observer remains    ' station-
                      munication. To meet the communication needs, SIO has                         ary on the ground. As a ship station moves on the surface
                      always operated and maintained its own licensed radio sta-                   of the earth, the apparent position of the satellite in the sky
                      tion, call letters WWD.                                                      will change. This change is very slow and changes in the
                      In 1966, it was decided to install permanent computer                        ship's heading will cause tricking problems.
                      centers on our larger ships. The computers were to be used                   The satellites were to be maintained stationary over a
                      for real-time data acquisition and control. The post-                        specific longitude by NASA ground control. ATS-I was
                      processing of data and general purpose computing were                        maintained over 149 degrees west while ATS-III was main-
                      also to be supported. The Shipboard Computer Group was                       tained over 105 degrees west. The satellites oscillated
                      created and charged with the responsibility for this task.                   about the equator and ATS-1 would move about 11 degrees
                      Along with the shipboard installations, an identical facility                above and below the equator. ATS-Ill would move about 9
                      was established on shore to support the ships and to pro-                    degrees above and below the equator. The period of the
                      vide general computing services at SIO. Soon it was                          oscillation is twice per day. One problem that has
                      recognized that there was a real need for computer to com-                   developed is that the fuel for the satellites positioning
                      puter communication. Initially what was envisioned was                       motors has been used up so no control can be exerted over
                      the ability to transfer messages between individuals, small                  them. ATS-IH is parked in a gravity anomaly and should
                      programs or documentation, and maybe even small                              remain there-forever. ATS-I has drifted into and back out
                      amounts of data.                                                             of ATS-111's territory and both have a wobble in their
                      Ship to shore communication has evolved from CW, Morse                       orbits. these satellites have long outlived their projected
                      code sent with a telegraph key keying a transmitter, to                      lives but are still in useful condition.
                      currently using satellites that provide near telephone qual-                 The ATS satellites are translating devices rather that
                      ity service. We will briefly discuss how some of the com-                    repeaters. They re-transmit exactly what they receive and
                      munication facilities function between the ships in the SIO                  the amount of power that they provide during transmission

                                                                     CH2585-8/88/'0000- 532        $1 @1988 IEEE

                                                                    Table 1 ATS Channel Definitions

                                                Channel                                        Principal Usage

                                     SDR (Ship Data Receive)            This is the "low data channel" and the ship stations receive
                                                                        data on this channel. Ile land stations transmit data on
                                                                        this channel.

                                     CH2 (Channel Two)                  ATS-III voice channel.

                                     CH3 (Channel Three)                This is the "center channel" and is reserved for ATS-1
                                                                        operation only.

                                     CH4 (Channel Four)                 ATS-HI voice operations.

                                     SDX (Ship Data Transmit)           This is the "high data channel" and the ship stations
                                                                        transmit data on this channel. The shore stations receive
                                                                        data on this channel.

                                     Note that SDR and SDX combined give full duplex operation. These five channels are defined for the convenience
                                I    of the satellite's users. At the satellite, they appear as a single wide channel.

                 is dependent on     the amount of power received from the                  vice with simplex data transmission rates of 56 Kbytes per
                 earth station. The stronger die received signal, the stronger              second. Inmarsat's three Marisat geostationary satellites
                 will be the re-transmitted signal. ATS-I is a very basic                   were launched in 1976 and are positioned to cover the
                 translator and can support only a single user at any given                 Atlantic, Pacific, and Indian Ocean regions. The complete
                 time. This means that voice must be operated simplex and                   Inmarsat space segment is made up of eight satellites which
                 there are no data channels on this satellite. It is quite easy             provides near global coverage with the exception of the
                 to transmit data on ATS-I but the data must be transmitted                 polar regions and a band in the middle of North America.
                 one way at a time. ATS-111 is a more advanced translator                   Four new dedicated satellites are currently under construc-
                 and can support several users simultaneously. There are                    tion and will be launched beginning in 1989.
                 five defined channels for the ATS satellite communication                  Besides voice and data communication over the satellite
                 system (Table 1) and ATS-Ill can support all of them. The                  systems, it is possible to send graphics data. The ATS does
                 only real limitation on multiple user operations on ATS-HI                 this throught Qwip which we have used to send bathymetry
                 is the total power available from the satellite.                           maps, administrative forms, and program listings. The
                 The current schedule calls for three one hour windows for                  Inmarsat has FAX capability. Besides being monochrome,
                 oceanographic use for voice traffic. The times are 140OZ                   our shipboard FAX machines have gray scale processing
                 to 150OZ, 180OZ to 190OZ, and 230OZ to OOOOZ. The data                     and have been used to send high resolution pictures to
                 channels on ATS-IH can be used at any time although by                     shore facilities.
                 only one user at a time. The data channels are operated on
                 simulated low power. The simulation of low power results                             EARLY COMPUTERIZED ATTEMPTS
                 from the location of the data channels on the satellite's
                 base band. The data channels are near the edge of the                      In the early 1970's, our first attempts at computer to com-
                 satellites response so it takes a lot of power to operate over             puter message passing used a computer to send or receive
                 them and they normally provide relatively weak signals.                    16 bits of binary data to a black box built in-house. The
                 This allows the ship systems to use maximum available                      box provided two frequencies that represented O's and Vs.
                 power and still avoid interference with voice channels.                    These were then sent to key the appropriate equipment
                 While the ship use of the data channels must never inter-                  which were then transmitted over the RTTY. This attempt
                 fere with a voice channel, it is often the case that a voice               did work, but because it involved three people on shore in
                 channel will interfere with the use of a data channel. This                three different locations and two people aboard ship to set
                 is one of the limitations on the use of the data channels.                 up the communication and make it work, and because of
                 One of the more recent communication systems installed                     the lack of constantly reliable transmissions, this project
                 on SIO ships is the Inmarsat, International Maritime Satel-                was never used.
                 lite Organization, satellite link. It uses the Mazisat satellite           A later attempt was made utilizing the ATS data channels
                 system as a marine communication system that provides                      to provide a path for the computers aboard two ships. This
                 Telex, telephone, and data services on a worldwide basis.                  demonstrated to us that it was indeed feasible to communi-
                 Data transmission rates of up to 2400 baud are provided.                   cate this way, although with varying degrees of bit error
                 More recently however, AT&T International using Inmar-                     rates. Operating from two different moving platforms try-
                 sat facitilies has made available a data communication ser-                ing to keep their antennas tuned to the satellite does not

                                                                                    533

                      always produce the best of conditions. Today almost all                  To implement the Telex connection required still another
                      computer traffic is from ships to our shore facility and                 set of rules. Access to Telex was made over telephone
                      vice-versa and ship-to-ship communication via computer is                fines, and SIO subscribed to several companies to provide
                      rarely done.                                                             Telex services. Communication protocols for the different
                                                                                               services were never quite the same. In order to connect to
                                   CURRENT IMPLEMENTATION                                      a phone line, we purchased a NU-DATA Series 106 con-
                      The Shipboard Computer Group of the SIO uses a DEC                       troller which contains an originate/answer modem and an
                      VAX-lln50 in its shore facility and two HMO's aboard                     auto-dialer. This box took care of the basic protocol
                      the R/V Melville and Thomas Washington. The computers                    requirements to communicate over Telex. Output from the
                      run under the Berkeley UNIX* 4.3 operating system. The                   box was RS-232. The Telex services we subscribe to also
                      computers aboard ship are networked together via Ethernet                use ASCII data code so no data conversion was necessary.
                      with provisions to connect other computers brought on                    Four more lines to the computer and the Telex hardware
                      board if they have the appropriate connecting hardware.                  requirements were met.
                      The computers on shore are networked via Ethernet to the                 The radio station required that all traffic transmitted, or
                      University of California at San Diego's campus wide Eth-                 received, be logged on hard copy. Therefore, all equip-
                      ernet network and also to UCSD's local area network                      ment also had a printer in parallel. For equipment operat-
                      (LAN). In addition, smaller computer systems around SIO                  ing in particularly noisy environments, like the ATS, a
                      are linked to these facilities by our computer.                          device built in-house was also provided to filter out non-
                      In early 1985, it was decided at SIO to "computerize" the                ASCII characters to the printers. This prevents the printers
                      radio station, and to a lesser extent, the larger of the ships           from taking unexpected form feeds, going into strange
                      equipped with computers operated by the Shipboard Com-                   modes, etc. One other requirement by the radio station was
                      puter Group. The goals for the radio station were to be                  to cover times when the computer was not available due to
                      able to send and receive electronic mail (e-mail), between               hardware problems, preventive maintenance, or some other
                      the radio station and the people using its services. The                 reason. For this, all equipment also have a terminal that
                      messages transmitted between the ships and the shore radio               can be switche d in place of the computer. Data can be sent
                      installation were then to be sent under computer control to              directly as it is being typed in by the operator or up to four
                      the various facilities. The communication facilities of                  screens of data, 24 lines by 80 or 132 columns per screen,
                      interest were the ATS, RTTY, Telex, and two message                      can be saved in the terminal.'s memory and transferred after
                      repeaters ashore where all messages are printed, one in the.             being entered.
                      administration offices and one in the marine operatiorls                 Up to eight RS-232 lines were needed to support the radio
                      offices.                                                                 stations requirements. However, after following the vari-
                      To implement e-mail for the radio station was an easy task.              ous tunnels, conduits, etc., the length of the wires far
                      It was only necessary to run the appropriate hardwire lines              exceeded the RS-232 standard. Therefore it was decided to
                      between the station and our facility, and to fumish them                 string only two twisted pair lines, four wires, and have a
                      with a terminal and an account on the computer.                          multiplexor on each end that would provide the eight lines
                      The ATS was the next easiest implementation. Because                     needed. Traffic through the multiplexor was not expected
                      data channels in the radio station were already connected to             to be very heavy and well within its limits. Only the termi-
                      a hardcopy terminal via RS-232 lines, it was only necessary              nal ports runs at 9600 baud. Ile ATS port is set at 300
                      to install a switch to select the current terminal or a coin-            baud and the other ports at 110 baud.
                      puter connection, and to string more hardwire lines from                 The original implementation of the repeater loops for mes-
                      the switch box to the computer. In this case, the lines were             sages to the administration and Marine Facilities was one
                      connected directly to one of the computer's RS-232 ports.                loop on a dedicated teletype line. The hardware required
                      Data had been routinely transmitted in ASCII code so no                  was identical to the RTTY. Recently the teletype line has
                      data conversion was necessary.                                           been removed and the two printing functions separated.
                      The RTTY connection was more difficult to implement.                     The administration's printer is located close enough to the
                      The output from the transmitter was usually connected to a               computer that wires were strung directly to the printer from
                      teletype. This meant current loop connections and BAU-                   the computer and a print spooler implemented to output all
                      DOT code. A Black Box system was purchased to convert                    messages. The link to the Marine Facilities spanned
                      the current loop to RS-232 signals and back; and another                 approximately 15 miles and was more involved as it was
                      box was purchased to convert the BAUDOT code to ASCII                    necessary to go over telephone lines. In this case the com-
                      code or vice-versa in real time. The data conversion could               puter port was connected to a modem with autodial capa-
                      have been done easily by the computer but since an in'ex-                bilities and the printer was connected to a dedicated phone
                      pensive box could be purchased to do the code conversion                 line with another modem. A print spooler was imple-
                      and to manage the RS-232 1/0 requirements, it was decided                mented to deal with potential printer error conditions (e.g.
                      to do it in hardware. Once again four more wires would                   off line, out of paper, paper jammed, and phone line noise).
                      need to be strung to connect the transmitter to a computer               The ibove descriptions cover most of the hardware require-
                      port and the hardwire requirements would be satisfied.                   ments needed to route traffic at the radio station by the

                      Trademark of AT&T

                                                                                      534

                   computer. Aboard the ships, only a subset of the hardware                 including personal computers such as IBM PCs and
                   described above was needed, and it was identical to that                  Apples, this capability allows for a convenient and reliable
                   used in the shore installation.                                           means of transferring files.
                   In order to make all of this hardware work, a certain                     Another UNIX utility that could be used, although we have
                   amount of software was required. UNIX provides most of                    not, is the UNDC to UNIX COPY, (UUCP), program. It
                   the utilities needed although in some cases maybe not quite               could be used to advantage for sending electronic mail
                   as well as the user might like. The main problem encoun-                  between ship and shore. The electronic mail utility in
                   tered in the automating of the radio station has been accep-              UNIX uses UUCP and Ethernet to transfer messages. The
                   tance by the radio operators. Most of them had no com-                    UUCP program, like Kermit, will keep retransmitting pack-
                   puter backgrounds and were reluctant to learn the neces-                  ets until a successful transfer takes place. With UUCP,
                   sary computer operations. Fortunately, UNIX provides a                    mail is held until a connection is established. Once the
                   facility for writing scripts containing lines of commands                 connection is established and verified, all the mail that is
                   that are executed by the operating system. To make it                     being held by both computers is sent without operator
                   easier for the operators to use the computer system, this                 intervention.
                   facility was used to construct a menu to walk an operator                 Aboard ship or on shore, people can connect their comput-
                   through whatever function he wanted to perform. Func-                     ers to our VAX systems via RS-232 lines or the Ethernet
                   tions were included to read or compose e-mail, start and                  links. These computers can then go further. Once they
                   stop receiving traffic from any of their communication                    have logged into the remote host computer aboard ship or
                   facilities, starting editors to compose messages, list con-               ashore, they can log into any desired computer that has
                   tents of directories, remove files, or any other function that            been connected to the remote Ethernet network. Ashore,
                   they would need. The disadvantage to this way of operat-                  since UCSD has access to most of the major nets, a user
                   ing is that scripts are slow since they are interpretive and              aboard ship can transmit mail or attach themselves to virtu-
                   are submitting commands to the operating systems. Also                    ally any net or computer anywhere via the UCSD network-
                   there is the necessity of doing extensive error checking on               ing facilities.
                   operator input. The system does work well and has                         As already stated, our system is used on a daily basis in the
                   achieved the desired objective with half the number of                    more passive mode, with the computer listening at the port
                   operators required at the station.                                        or sending data out the port to the transmitter. This mode
                                        THE NEXT STEP                                        requires very little operator interaction. The operator need
                                                                                             only turn it on or off by software. To perform real com-
                   Our usual way to establish a connection between computers                 puter communication requires the radio operators at both
                   is to listen or send on a port with no interaction between                ends to establish the communication path. On shore,
                   computers. However, once the various transmitters have                    because the radio facilities and the computer facilities are a
                   been connected to the computer, the link for computer to                  distance apart, the radio operator must then call the com-
                   computer hookup has been established. The radio link is                   puter user over the telephone to notify him that communi-
                   really nothing more than a copper wire link with probably a               cation has been established. The user can then proceed
                   somewhat higher bit error rate. To go a step further is to                with his computer link. After he is through, he must then
                   use one computer to connect to the other computer. The                    call the radio operator back so he can break the radio con-
                   only, change for the computer is that on one end, the port                nection. Setting up the "normal" computer mode must then
                   corresponding to the    'communication device must be                     be done. Radio operators would prefer not to go through
                   configured so that the computer can be "logged into". Con-                this routine, so it is only done in cases where large file
                   necting computers together can be done through RTTY or                    transfers need to be completed in an error-free environ-
                   voice channels but with the current hardware we only do it                ment. To alleviate this problem, the necessary ATS equip-
                   through the ATS. Hardware does exist for the RTTY and                     ment should be purchased to allow the Shipboard Com-
                   voice channels that provides more reliable communication                  puter Group to perform all the necessary functions required
                   and in a full duplex environment but so far there has been                to set up the ship-to-shore link themselves. This would
                   no interest in purchasing it.                                             expedite matters tremendously but funds have not been
                   Once the computers are talking to one another, it is possi-               available to do this.
                   ble to do remote computing or other computer functions. It                One other means of connecting computers has been
                   is possible to make data transfers under computer control                 achieved by way of Inmarsat. Using a triple speed modem
                   making the transfers much more reliable. One often used                   (300, 1200, and 2400 baud) with error correction capabili-
                   file transfer facility is Kermit. It does not have error                  ties, a user aboard ship can use a voice channel to call any
                   correction abilities like cyclic redundancy check (CRC),                  compatible modem. Our experience has been that using
                   checking to enable data stream correction as the bits go by.              voice channels can result in a noisy environment. The
                   It works by using checksums to determine if a packet has                  error correction option within the modems has never been
                   been sent error free. If the checksums do not match, the                  tried. Our use of this system has been restricted by the cost
                   receiving computer requests the sending computer to                       of Inmarsat voice channel communication. The current
                   retransmit the packet again. We have used Kermit to                       cost is $30 for the first three minutes and,$1 for every fol-
                   transfer files between computers with 100% reliability.                   lowing tenth of a minute. In most of the cases where the
                   Because Kermit has been ported to so many computers                       data collected aboard ships would be usefully sent to shore

                                                                                     535

                   for analysis, the quantity of data is too large to be cost                ing on the ship, different people may operate the ATS. On
                   effective. Some of the typical large data streams collected               the smaller SIO ships that do not have radio operators, the
                   at sea include seismics profiles and Sea Beam bathymetry,                 captain or a member of the scientific party may operate it.
                   both of which accumulate many millions of bytes of data                   On the larger ships, it may be the radio operator
                   on a daily basis.                                                         exclusively or a member of the scientific party. There still
                   Some experimentation has been done with intelligent con-                  is apprehension by captains and radio operators for anyone
                   trollers sending out packets with error correction and/or                 using the ATS or any other radio without their direcr con-
                   packet retransmission over the different transmitters. This               trol. In a computer-to-computer hook-up, this control is
                   makes connecting computers together by RTTY or VHF                        obviously lost.
                   more practical. These controllers have internal micropro-
                   cessors to take care of all decoding, signal processing, and                                    CONCLUSIONS
                   protocol requirements, and their output can be made com-                  For us, ship-to-shore computer-to-computer data communi-
                   patible with VHF, RTTY, and RS-232 requirements. The                      cation, even under the best of circumstances, has the prob-
                   internal modems can transmit packets at rates up to 1200                  lem of various degrees of bit error rates. Satellites provide
                   baud with the option of using an external modem for higher                the best and easiest transmission mediums. The limitations
                   baud rates. One controller tested also supported many                     on ATS are its slow transmission rates, limited availability,
                   parallel, dot matrix graphic printers with a direct connec-               manual antenna tracking, and lack of global coverage. Its
                   tion to print BF monitored FAX signals.                                   main advantage over Inmarsat is that after its initial cost,
                   Another concern to consider is that the captain and the                   its use is free except for maintenance on the equipment.
                   radio officer are responsible for all communication to and                The limitation on Inmarsat is its expense, $30 for the first
                   from the ship. The ATS in particular is technically a tele-               three minutes and $1 for each additional tenth of a minute
                   phone and not under FCC regulation. It therefore does not                 to North America. Its advantages are transmission speeds
                   need a licensed radio operator. Also, on SIO ships it is                  up to 2400 baud over voice channels or 56 Kbytes over
                   considered as a piece of scientific equipment and depend-                 data channels, it is always available and with near global
                                                                                             coverage.

                                                                                      536

                                                      THE DEFENSE MAPPING AGENCY'S
                                                   NAVIGATION INFORMATION NETWORK

                                                                     Steven C. Hall

                                                               Defense Mapping Agency
                                                            Washington, D.C. 20305-3000

                                         Abstract                                 The weekly Notice to Mariners is a joint publica-
                                                                               tion of the Defense Mapping Agency (DMA) , the
                  More than a decade ago, the            Defense Mapping       National ocean service (NOS) and the U.S. Coast
                Agency    made a     ccmmitment     to      improve     the    Guard (USCG) .     Its use is intended primarily for
                means of      processing, managing, and          producing     the offshore mariner; that is, U.S. Navy units
                navigation safety publications          and information        operating worldwide, ccmmercial U.S. vessels oper-
                using automation to the fullest extent possible. As            ating in international trade or coastal trades and
                the present Automated Notice to Mariners System                lastly, the offshore sailor who goes beyond the
                developed and matured, it became apparent that the             limits of the USCG local Notice to Mariners. It is
                future of dissemination of        these    data    lay in      a time-dated publication essential to the preserva-
                teleccrmnun icat ions, thus    the creation        of the      tion of the integrity of the nautical products
                Navigation Information Network (NAVINFONET). This              which are necessary for the safety of all ship-
                paper will review the history, design, and use of              ping, large or small.         It is critical to all
                the ANYS and then discuss the present and future               concerned that the information         contained in the
                utility of the NAVINFONET. As the age of the Elec,             Notice be accurate, current and distributed in a
                tronic Chart Display and information System (ECDIS)            timely manner.
                approaches reality, the potential of the NAVINFONET
                as the only functional existing system to support                  When viewed as a battle against time, three
                corrections to ECDIS at sea may          well prove its        separate aspects of the Notice to Mariners process
                greatest value. In the interim, its worth is proven            were defined; namely, compilation, composition and
                daily by the myriad of users who seek up-to-date               distribution. Within the canpilation phase of a
                marine safety information to correct their charts              weekly Notice, the first target was chart correc-
                and publications far in advance of receipt of the              tions as the Notice is the legally designated
                printed word through the mails.                                vehicle to correct any or all of the 5,000 odd
                                                                               charts produced by NOS and DmA.         The first thing
                                                                               that had to be done was to break away f ran the
                  The Defense Mapping Agency began the design of               former loosely defined format of a chart correc-
                the Automated Notice to Mariners System (ANMS) in              tion and     create specific guidelines to simplify
                1975.   The intent of this project was to maximize             and standardize information presentation. Suffice
                the use of automation to improve the composition,              it to say that DMA consciously f lew in the face of
                management and distribution of several products                international tradition in designing this new
                which prcmote navigational safety, primarily the               computer compatible format which:
                weekly Notice to Mariners. In view of the ambitious
                scope of this project, and keeping in mind the                      1.   corrects each chart individually
                blinding pace at which ADP systems were reaching                    2.   tracks edition number, date, correction
                the market in the last decade, a phased development                      authorty and previous correction
                approach was selected. This allowed DMA to add the                  3.   uses a three (3) colLnn format for text
                latest off-the-shelf hardware and certain pieces of                      that tells action (in f ive (5) verbs --
                commercial sof tware to the ANMS as the            system                ADD, ]DELETE, SUBSTITUTE, FELOCATE, aiANGE)
                matured. The initial design concept of this devel-                       --subject (specific standards, minimum of
                opment was to allow ccmmunications access to the                         words) - position (level of accuracy tail-
                extensive files to be developed          not in the tra-                 ored to specific scale and required action),
                ditional meaning of a data base          but actually as       By changing to columns, reducing to only the mini-
                data files. The success of this phase develop-                 mum text necessary and custom designing coordinate
                ment approach has already been proven even though              presentations, data entry for a computer based
                its full potential has yet to be achieved. Inter-              system became simpler, canpiling (and training
                estingly enough, the communications portion of the             compilers) became faster and easier, and accounting
                system design has been so popular with the user                for various horizontal datuns in a common area
                ccmmunity and so beneficial to the Defense Mapping             ceased to be a problem.
                Agency and the U.S. Coast Guard among others, that
                this portion of the workload has now been given its               Use of the new guidelines established           as the
                own computer and its own name -- The Navigation                system    design proceeded has allowed the Marine
                Information Network or NAVINFONET.                             Information Specialist (MIS) compiling a notice to

                                                         CH2585-8/88/0000- 537  $1 @1988 IEEE

               move through his tasks more easily and more accu-        via remote communications and to improved effi-
               rately than in the past. Data entry to the weekly        ciency of Notice to Mariners data processing.
               work file is facilitated by the use of intelligent
               graphics terminals which will soon be available on         Here it is appropriate to mention that periodi-
               each desk. The quality     and integrity of chart        cally throughout the year special recaps of infor-
               corrections and, in fact, all sections of the            mation appear in the weekly Notice. Automation of
               Notice have been maintained throughout the develop@-     weekly compilation of the Notice allowed automatic
               ment process.                                            updating of numerous summary files for later pro-
                                                                        duction; thus, time to compile these listings was
                 Automation was used to expedite the compilation        eliminated completely. The files referred to here
               of the catalog correction portion of Section I of        include the, monthly mobile oil drill rig update,
               the weekly Notice to Mariners as well. The DMA           the quarterly drill rig status list and the quar-
               indexes its hydrographic products in ten (10) vol-       terly list of charts affected by notices, to name
               umes of catalogs.  These dynamic publications are        but a few.
               corrected weekly.  Naturally,    if    mariners are
               expected to have   the latest available chart on           In each of the aforementioned cases, the informa-
               board, there must  be a rapid means of notifying         tion is processed by an MIS, checked, entered to
               them when a chart is ready for purchase. A side,         the work file by an Editorial Assistant working at
               benefit of this development was a file of chart          a terminal, proofed from an output device, checked
               titles, scales, coordi nates and other attributes        and revised as.necessary and loaded to a weekly
               for future use. Ebr now, suffice it to say that          work file on the ANMS computer. Although this input
               this change has trimmed compilation time for cata-       procedure represents several new steps in the com-
               log corrections in half.                                 pilation proceSSr it remains far more efficient
                                                                        than the past manual methods used at DMA. The
                 Computer assisted compilation of the List of           composition process begins at this point.
               Lights (produced by DMA) and Light Lists (produced
               by U.S. Coast Guard) has resulted in a measurable          At the conclusion of the compilation of the
               decrease in compilation time and a corresponding         weekly work file, several computer routines are
               improvement in product accuracy and dependability.       executed by the ANMS. These procedures simultane-
               In this case, automation was a necessity as well as      ously update a number of history files from which
               a desirable improvement because the former method        various products are composed or queried.           In
               used by DMA and USCG was using totally archaic           addition, a tape is generated which drives an
               equipment and technology. Adding the List of Lights      automated photo typesetter wbich produces page
               and Light  Lists to the ANMS provides far more           negatives of chart corrections, list of light
               up-to-date information than ever before due to           corrections, light list corrections, radio aids to
               simplified data entry and storage procedures.     The    navigation    corrections, catalog       corrections,
               compilation data   files for all seven (7) volumes       broadcast warning message texts and special cumula-
               .of the DMA List of Lights and six (6) of the seven      tive listings -- each ready for the press. The
               (7) USCG Light Lists are now mature and strictly         reader should contrast the speed of this automated
               maintained on a weekly basis. These latter volumes,      operation with the old hot lead type operations of
               although produced by the US Coast Guard, are main-       the Government Printing Office or even our own
               tained through the weekly Notice to Mariners and         vari-Type list of lights process where each line of
               compiled and produced usingthe computerized work         type was manually typed on to one_3@'_x    -- 10 " card
               files of the AkmS. unique to these operations is         that required the operator to change type elements
               the fact that all the USCG light files (weekly,          as many as four times per line/card. Computer
               summary, and annual) are accessed and processed          driven typesetters at DMA can      set up to 4,000
               remotely by Coast Guard personnel, thus eliminating      characters per minute, a speed which      makes even
               their need to be on site at DMA.                         the most proficient manual operator obsolete.

                 Corrective information for certain radio aids to         Because this phase of production is controlled by
               navigation are now compiled on the ANMS either as        software, it has enabled DMA to upgrade or replace
               part of the appropriate List of Lights or as part@       its former typesetting equipment without interfer-
               of Pub. 117, Radio Navigational       Aids. Further      ing with the critical schedules of the Notice to
               automated compilation of this latter volume is           Mariners. ANMS Software modifications are neces-
               planned for the near future.                             sary, of course, but that is far more desirable
                                                                        than complete system redesign. Once again the
                 The next compilation task to be addressed as part      phased development procedure has proven advanta-
               of ANMS was the Broadcast Warnings portion of the        geous.
               weekly Notice. These warnings are the texts of
               messages issued by DMA as part of its duties under         At the same time that the various summary and
               the worldwide     Navigational Warning Service and       history files were created and updated by the
               include   NAvAREA Iv and NAvAREA xII warnings;           weekly work filesr an additional compilation/compo-
               HYDROLANT and HYDROPAC warnings; and Special warn-       sition benefit was realized. As the master data
               ings. The compilation advantage here was not re-         files reached maturity, it became possible to
               lated as directly to the weekly Notice as it was to      produce with vastly improved efficiency the five
               the production of the Daily memorandum and the           (5) voluiies of Summary of Chart Corrections twice
               quarterly summaries of messages in force. NDnethe-       yearly, seven (7) volumes of List of Lights and six
               less, this software package did contribute to the        (6) volumes of Light Lists on demand or on a sched-
               overall usefulness of the    ANMS data to mariners       ule simply by generating a print tape to produce

                                                                     538

               page negatives frcm the same auto photo typesetters            also was selected because all ships equipped with
               previously mentioned. To give an idea of the extent            an INMARSAT ship earth station have TELEX and the
               of this improvement, the total summary of correc-              ship driver is our main target. Up until early
               tions file contains every chart correction to every            1987, NAV-INFONET      was also     accessible by TWX;
               DMA and NOS chart published since mid 1975 or since            however, it proved to be of little use so the line
               the latest edition date of the individual chart. In            was converted to a TELEX rotary circuit.
               other words, it contains everything the user needs
               to bring his charts up-to-@-date to the point where              As of      today, NAVINFONET is      accessible     over
               maintenance can be easily assumed by the weekly                voice grade telephones (including INMARSAT voice
               Notice to Mariners. This represents 40 megabytes of            circuits) on: the U.S. telephone systems by five
               data.    The lights data f iles on the other hand              (5) 300 baud lines, f ive (5) 1200 baud lines, and
               contain the   current status of over 82,000 aids to            two (2) lines at 1200/2400 baud; the European
               navigation    worldwide.     These files hold         107      standard CCITT V.21 by two (2) lines at 300 baud;
               megabytes      of data. To    put this improvement in          and one dual TELEX line compatible with any Inter-
               perspective, composition,     negative production     and      national Record Carrier. This equates to 16 lines
               printing of   a List of Lights formerly took on       the      plus several hard-wired access ports.
               order of.90   days prior to automation. Now it        can
               be accomplished in two weeks, although we normally               At the      time  this    paper was prepared, there
               allow four. On the other hand, the constant changes            were over 1,600 individual user identification
               representing     new   data    for   chart     correction      codes on issue that permit access to the NAVINFONET
               summaries were never an easy update process for                system. of this number, about half have used the
               manual compilation whereas now the summaries are               NAVINFONET and make an average of 1,000 queries to
               produced practically at the touch of a button.                 the system each month. These figures do not reflect
                                                                              special query options used by DMA, the Federal
                 The final time oriented design element that was              Republic of Germany, Lykes Brothers Steamship
               chosen was information distribution. This was a                Ocxnpany, or selected. other customers with whom DMA
               tough problem because broadcast warnings are trans-            collaborates on special projects. Current usage is
               mitted by Morse telegraphy radio, the Notice to                at about 16% of capacity which leaves much room for
               Mariners is sent by first class mail, and the                  expanding the customer base as well as improving
               remainder utilize various rapid automatic distribu-            our available services.
               tion methods to reach the user. So --where did we
               go from here? After all, already we had cut compi-               A pioneer in managing the development of the
               lation and composition time down by a factor of                ANMS and NAVINFONET, Mr. Glenn R. DeYoung, a former
               50%, that is, from 42 days to the user under former            head of the Notice to Mariners, was adamant about
               methods to 21 days for the printed paper copy with             the fact that the system must be user friendly. His
               the computer assisting with compilation and compo-             position was (and ours still is) that the system is
               sition. Enter the Navigation Information Network               for the end user, the navigator and cartographer;
               (NAVINFONET) which for our primary target of chart             therefore, it must operate in plain language, not
               and light corrections, reduced another eight (8)               in code. With this guideline in mind, nine (9)
               days off the user access time.                                 separate modules were developed within NwiNFONET,
                                                                              each with appropriate sub-elements.        As with most
                 NAVINFONET, like the ANMS, is centered around a              things, an advantage can become a disadvantage at
               second Prime 2550 super minicomputer. In point of              times. While working in plain language was advan-
               fact, they are very close to being totally redun-              tageous overall, it had the effect-of slowing the-
               dant   systems..   This    is-- necessary --to ensure          user's response time by requiring numerous prompts
               dependability, data integrity and uninterrupted                and replies. This became just another on-going
               service to the user. Each time the ANMS data files             challenge for us to design an optimum compromise
               are updated, a similar update is performed on the              position and we're still striving for that plateau.
               master disk of the NAVINFONET. Thus, its data files
               are up@to-date making the latest information                     No matter whether the user selects "good ole" 50
               available for remote query. The NAVINFONET computer            baud TELEX or the more efficient 2400 baud
               is a multipurpose computer which simultaneously                voice-grade circuit, a conversational series of
               supports new system development, broadcast warning           -prompts will le    'ad the user step by steR to the
               processing, manages the query system and stands,               needed   data. Preformatting a request can be very
               ready to take over from the ANMS if necessary.                 helpful  to the user unless he is just experimenting
                                                                              with the system. it must be emphasized again that
                 NAVINFONET's primary function is to bring the                although the data are free,       the connect cost is
               user closer to the data needed while at the same               paid by the user.     Tb receive a user ID, one need
               time providing selective query options to minimize             only convey the request to:
               the connect time and associated costs involved with
               interactive data exchange over commercial communi-                      Director
               cations circuits. As the potential user community                       DMA Hydrographic/Topographic Center
               was examined, it was obvious that the versatility                       ATTN: MCN
               of the worldwide voice grade telephone system                           Washington, D.C. 20315-0030
               presented the most efficient and accessible cir-
               cuitry readily available to NAVINFONET.           Not so       and an identification code will be assigned and a
               simple to access, or as versatile, but universally             user manual supplied by return mail.         Nearly any
               accepted, was TELEX.      Even though it is slow and           data terminal with an internal MODEM or acoustic
               somewhat unfriendly in a, conversational mode, it              MODEM   or a micro computer with a communications

                                                                         539

               software package may be used.        NAVINFONET is       is called "Query by Port." By entering your choice
               configured to operate full duplex, parity off, 8         of all notices or notices back to a certain point
               data bits, 1 stop bit. The 300 baud modems are           following the two digit figure wbich corresponds to
               compatible with the Bell 103 standard while the          one of 92 ports or regions, the user avoids typing
               1200 baud equipment correspondsto the Bell 212 or        a long list of chart numbers. A word of caution is
               Racal-Vadic 3400 standards. The 2400 baud circuits       necessary here. The charts selected for each port
               are compatible with Bell 201 modulation standards        may not be suitable for each individual user. It is
               and, of course, there are two 300       baud modems      up to the user to make that decision and supplement
               con-forming to CCITT V.21      standards    for our      the data received as he feels necessary.
               overseas user community.
                                                                          Lastly in this section is program 22 which we
                Module 1 is the ANMS Mailbox/utilities group.           informally call the autanated chart card. By enter-
               There are only two sub-elements to this section at       ing a chart number, the user  obtains a printout of
               the present time. Program 10 is the ANMS Mailbox.        the Notice week numbers in    which that chart was
               This allows the user to send a message to DMA from       corrected beginning with      its announcement as
               his location and to get a copy of exactly what he        available from a distributor. This program is used
               sends to us.    This is a supplementary, one way         extensively by U.S. Navy units and others who track
               canmunications program.    That is, it is not in-        the number of Notices charged against a chart.
               tended to compete with commercial electronic mail
               systems or bulletin boards, but merely provides a          Module 3 is concerned with the text of various
               narrow set of users with an alternative method of        radio broadcast warnings. This particular group is
               canmunicating information to DMA for immediate           valuable to retrieve previously transmitted radio
               consideration for action.    In point of fact, an        messages which were missed for whatever reason.
               incaning MAILBOX message prints out at the World-        This is the only program on the system that gives
               wide Navigational Warning Service watch desk which       information - af ter - it-was pranulgated-by another
               is operated 365 days per year. most of our oil,          means; however, it provides a highly valuable means
               drill rig movement data canes in over our MAILBOX        of restoring radio warning continuity after a break
               !as do many requests for information fran companies      in reception. Selections are based on all warnings
               under contract to DMA. occasionally, DMA will            or warnings since a specific date. Further deci-
               promulgate outgoing information on the MAILBOX;          sions are made using the DMA subregion     system to
               however, in order to receive these messages, the         narrow the    affected   area   or   else    NAVAFdW
               user must call into the system. As can be seen,          HYDRCLANT-HYDROPAC designations can be used. Spe-
               that is not particularly dependable or efficient in      cial Warnings may be queried by date or by number
               the outgoing mode.                                       as can MARAD Advisories. The intent of this module
                                                                        was to provide the user with sufficient parameters
                 The second option under this module is the NA-         to narrow his search for these vital data as much
               VINFONET User's Manual. As the Manual is canposed        as possible. Last, but not least, with this in
               on the ANMS, this option was added to allow changes      mind, option 32 prints a list by number only of all
               to the system to be made available to users without      effective warnings in a chosen warning series so
               continually reprinting the instruction booklet.          the user can check his inventory and request only
               This option is preceded by some very interesting         the missing items.
               numbers concerning the down load times to transfer
               the Manual from its file to the user. Quite simply,        Modules 4 and 8 are practically identical.      The
               it states "This selection prints out the 1987            major difference is that 4 deals with the DMA Lists
               Blition of the NAVINFONET User's Manual. This takes      of Lights for foreign waters and 8 deals with the
               4 minutes at 2400 BAUD, 8 minutes at 1200 BAUD and       USCG Light Lists for U.S. waters.    The user first
               32 minutes at 300 BAUD. TELEX users should not           selects the volune number he wishes       to query.
               exercise this selection." These statements illus-        Thereafter, he may select individual lights by
               trate quite graphically the advantages of voice          number or groups of lights consecutively listed or
               grade use over TELEX. Although voice grade may cost      even all lights    between two selected light num-
               more per minute, ultimately its efficiency and           bers. This last option will allow a user to print
               speed override the lower per minute TELEX rates.         an entire volume if he so chooses. All these option
                                                                        selections print the light data including any cor-
               The second module, subsystems 20, 21 and 22, deals       rections processed against the selected lights
               with chart corrections for NOS and DmA nautical          since the latest printing of that particular vol-
               charts.  Program 20 is the most active query pro-        ume. On the other side of the coin, an option is
               gram on the system. It gives the user access to all      offered that allows the selection of just the
               corrections to selected charts or corrections from       lights that have changed since the last edition
               the current notice back to a user selected notice        date of the publication.    These programs are de-
               number for selected charts.    The most common and       signed to facilitate updating small portions of a
               efficient use of this program is as a last minute        List of Lights or Light List until the hard copy
               update before making port or as a supplement to the      Notice is received through the mails.     This will
               printed Summary of Corrections and weekly Notice         allow the corrected volume to be used safely as a
               when a change of orders is received to divert to a       supplement to the appropriate up@to-date nautical
               port or area where the chart portfolio may not have      charts.
               been maintained previously.
                                                                          The last unique user selection in the lights
                 Option 21 was created to save the user from            program allows the navigator to select only those
               having to enter a long series of chart numbers. It       lights exceeding a certain range of visibility.

                                                                   540

                Ibis option may be useful when coasting in order to           Module 7 was designed to give the user convenient
                see at a glance the specifications of all lights            access to DMA Hydrographic Products catalog correc-
                visible at 12 miles or more.     other uses are as a        tions. Sales'agents, ship chandlers, and navigators
                voyage planning tool for the navigator and for the          reviewing portfolios for chart replacement can make
                cartographer.   it simplifies lighted aid selection         use of this group of subroutines to stay on top of
                for certain smaller scale charts which show only            what's new in the world of charts and publications.
                the more powerful navigation lights.                        Selections are made first by catalog volume number.
                                                                            The numbers one through nine correspond to the 9
                 Module 5 doesn't really "correct" anything, but            DMA catalog regions. Selections may be further
                it contains information that could help save a ship         defined by subregion using two digits. The excep-
                and crew.   It is called the Anti-Shipping Activity         tion to this rule is volume 10, miscellaneous
                Message (ASAM) subsystem. This file was developed           Charts and Publications, which can be searched only
                at the   request of the U.S. Interagency Working            by volume number.     In any case, the user may make
                Group on piracy and Maritime Terrorism. it contains         all corrections to the volume or subregion or all
                random reports of various forms of aggression               corrections since a certain notice.             Further,
                against shipping around the world. Events are               within the subregion query group is the option to
                categorized by date and by geographic area based on         query a specific notice number alone.
                the DMA subregion system.       ASAM reports can be
                f iled with DMA using option 50 which is the f irst           Programs 97, 98, and 99 are operational in nature
                subroutine of the module. Step by step          prompts     in that the first two supply a short or long menu
                help the user enter full particulars of the inci-           for reference purposes and the last selection
                dent to be reported and then automatically transmit         actually terminates your system access.
                the message to DMA over the ANMS mailbox subsystem.
                Upon receipt at DMA, the text is reviewed, evalu-
                ated for further action or disseminated, edited,              By way of recap, you have here, readily available
                and f iled in the ASAM data file for use by all             at your fingertips, a full file of chart correc-
                system users when needed.        This is an immature        tions tied to individual charts by edition date and
                f ile as of this writing.     It is expected to gain        number, broadcast warnings with worldwide applica-
                favor as a voyage planning tool in the future by            tion, List of Lights, and Light List data for the'
                providing cautionary ihformation to owners and              world, anti-shipping     intelligence       information,
                masters concerning security conditions in and near          mobile drill rig/ship location data, and chart
                ports and narrow channels around the world. Exam-           catalog updates. Each program was designed to be a
                ples of data in this file include the ACHILLE LAURD         functional tool for the user--the mariner at sea or
                incident, robberies of ships transiting the Malacca         the planner in port. of course the cartographers
                Straits, attacks on fishing boats and merchant              within DMA and NOS received great consideration
                ships coasting off Western Sahara, and certain              when our system was designed, expanded and modi-
                events occurring in and around the Persian Gulf             fied.    In fact, DMA remains the highest volume
                over the last few years.                                    remote user of the system. Several instances have
                                                                            occurred wherein a user requested a specific pro-
                 As the world need for     petroleum increases, more        gram and we were able to accommodate the request,
                and more offshore oil exploration has become neces-         such as the Automated chart Card and the Query By
                sary. Despite the present slackening of interest, a         Port file. It is in our interest to continue re-
                point had been reached a few years ago when there           sponding to such requests whenever possible, not
                were so many mobile oil drill rigs and drill ships          only to create new options, but also to discontinue
                plying the seas that it became extremely awkward to         unused selections now that sufficient user statis-
                trace their whereabouts. Thus, module 6 "Oil Drill          tics are available to make competent decisions.
                Rig Locations" (ODR) was created. This subsystem is
                used to track nearly 1,000 of these very fluid                What does the future hold for ANMS/NAVINFONET?
                exploration vessels. The ODR file makes an ideal            Technology is moving ahead so rapidly it is almost
                supplement to the weekly radio broadcast warning            futile to look too far into the future, but plan
                messages which update the movement status of the            one must in order to be a part of the future rather
                rigs. The user may use this file in several ways.           than an afterthought of history. The primary goal
                If   he knows the name     of    a particular      unit,    of autanating the Notice to mariners and associated
                entering the correct spelling will        produce the       information was to be able to produce that weekly
                current location, assuming the information has been         periodical, cover-to-cover, by digital means.          ith
                accurately reported to DMA, of course. Secondly the         is about 60% complete. Still to be completed are
                user may query an area by subregion, which corre-           all of the free text sections, chartlets (or wall
                spond s to  the f irst   two digits of a DMA or Nos         paste-on sections of charts) , depth tabulations,
                chart nunber. Thirdly, he may query by broadcast            weekly sailing directions corrections and miscella-
                warning area; that is, HYDRoLANT, HYDRoPAC, NPVAREA         neous graphics. Automation of full sailing direc-
                IV or xiI. The last subroutine in this file allows          tions will be accomplished in the near future using
                the user to enter a rectangular area of operation           the DMA Consolidated Navigation System and the
                by coordinates and the NAVINFONET will search for           Navigation Graphics Workstation. The major benefit
                and print the names and locations of all oil explo-         of these improvements in relation to NAVINFONET
                ration units within the designated area. This file          will be the remote access availability of the
                is updated daily from a variety of sources, many            weekly Sailing Directions and Coast Pilot correc-
                reports of which come to bMA over the mailbox               tions and ultimately, remote receipt of chartlets,
                subsystem.                                                  depth tabulations and graphics.

                                                                        541

                   A project of major concern at this time is, of           cost may not sufficiently offset higher costs
                 .course, the development of the Electronic Chart           associated with duplex operation of voice (up to
                 Display and Information System (ECDIS). It would           2400 baud) or data speeds. This will bear further
                 seem only a halfway job if a functional ECDIS were         investigation, especially since someone will have
                 created to meet international standards without a          to 'absorb the cost for the data.
                 means of providing corrections to the ECDIS data
                 while at sea. Should the United States endorse the           I've given sane background on the development of
                 ECDIS concept and even produce an ECDIS, it will,          the Automated Notice to Mariners System, discussed
                 no doubt, be incuibent upon the Defense Mapping            the content of the various files accessible using
                 Agency to provide the means to keep it corrected.          the Navigation Information Network, and presented a
                 The ANMB/NAv-iNFONET is available for that purpose         few ideas and potential avenues to pursue in the
                 when the time comes.                                       future. our existing systems consist of dual PRIME
                                                                            2550 super mini computers with a full range of
                   once more, it should be emphasized that the data         peripheral devices. Each is equipped with one 600
                 is already in the files of the ANMS, although I'm          megabyte disk drive and two 80 megabyte disk
                 sure the format will need some revision. The oommu-        drives. We have designed room for expansion and can
                 nications system is there in the form of NAVINFONET        support future uses as well as new users of our
                 waiting for a heavier workload.                            systems.

                   The Federal republic of Germany has attempted to           The NAviNFONET was designed for flexible exter-
                 study chart correction sizeing under ECDIS condi-          @nal access to these vital data. Tbe mission of the
                 tions and has generally arrived at a f igure of 60         Navigational Aids Division which controls the
                 kByte to correct a 100 chart portfolio. A use of           ANMS/NAVINFONET is to promote safety of life at sea
                 the NAviNFoNET not previously discussed is to              through up-to-date, accurate and inexpensive nauti-
                 electronically transfer chart corrections contained        cal charts and publications. Today we accomplish
                 in each weekly Notice to Mariners digitally from           most of the in-house processing paper to paper or
                 Washington, D. C. to New Orleans, Louisiana. This          digits to paper. Tomorrow, we'll do it digits to
                 process is done over a 1200 baud voice grade line          digits. Satellite communications using Standard A,
                 using an error checking protocol and takes about 20        Standard B, or Standard C, or land based radio
                 to 30 minutes to complete an error free transfer.          using   vHF or high frequency narrow band direct
                 Coincidentally, the    size of this transfer, wiien        printing, or conventional distribution of unconven-
                 converted to the 10 bit German byte is 57.7 kBytes!        tional products such as mailing floppy disks or
                 One item that remains to be resolved is how to             larger printouts are potential avenues worth inves-
                 transfer these data to the user. INKARSAT Standard         tigating. The list for tomorrow is endless. DMA
                 C may be a viable candidate system, but at a speed         will be part of tomorrow with the Navigation Infor-
                 of 600 bits per second in simplex mode, its low            mation Network.

                                                                       542

                                                 COLD WEATHER EFFECTS UPON MARINE OPERATIONS

                                                    CAPT John D. Crowley, USCG (Retired)

                                                              Marine Consultant*
                                                              606 Montauk Avenue
                                                       New London, Connecticut 06320

                                     ABSTRACT                               Ice continues to accumulate, destroying the stabil-
                                                                            ity of the ship until, under the force of sea and
              Cold weather causes unique and unexpected problems            wind, the vessel capsizes. Annually, perhaps ten
              in marine operations. These problems affect both              or twelve ships are lost in cold, northern seas be-
              ships and offshore structures. The paper reviews              cause of this threat. Well known examples include
              a few of these problems. Several incidents are                the British fishing vessels LORELLA and RODERIGO,
              discussed to provide examples of the severity or              lost northwest of Iceland in 1955 (Reference 1),
              the unexpectedness of the events. Design features             the British ROSS CLEVELAND and KINGSTON PERIDOT,
              and operational procedures are noted and some needs           also lost in Icelandic waters, and the U.S. crabber
              are discussed.                                                GEMINI, lost in Alaskan waters in 19,80.

                                                                            The most serious cases of ship icing involve freez-
                                1. INTRODUCTION                             ing spray. Spray can be the wind-driven spray from
                                                                            wave tops and breaking seas, or the spray generated
              Vessels and structures are brought into cold weath-           by the sea striking the ship's hull. Significant
              er operations in a variety of ways. In some cases,            spray also arises from the interaction of the wind
              icebreakers and offshore structures designed for              and sea with the ship generated wave train. Of
              Beaufort Sea or northern Norwegian Shelf opera-               these sea spray sources, spray generated by the sea
              tions, attention is paid in design to meet the spe-           striking the ship's hull is by far the most
              cial problems involved. Similarly, Great Lakes                important in topside icing.
              ore carriers and most northern fishermen antici-
              pate cold weather operations; special design fea-             Of lesser importance is the   freezing water from
              tures may be installed and cold weather operational           atmospheric sources: freezing rain, freezing fog-
              precautions are developed. Otfiervessels or struc-            Dr snow. However, all contribute to icing and
              tures have been designed to operate in warmer re-             worsen the situation if sea spray icing occurs con-
              gions. When the demands of commerce shift their               currently. From the small data set available, it
              operation to colder areas, careful winterization              appears that snow in the presence of sea spray ic-
              should be accomplished. Finally, there is the case            ing occurs in most cases of extremely rapid icing.
              of the ship caught in a one-time situation: the               Whether this is true because of the interaction of
              freighter for years trading between the Gulf Coast            snow and freezing spray, or because the.particular
              and South America, sent to pick up a cargo of news-           meteorological conditions that produce extreme sea
              print in the St. Lawrence in January, or the ship             spray icing also generate heavy snow flurries has
              caught in Boston or Portland, Maine on that odd               not been established. (See POLAR LOWS below.)
              week when the temperature never rises above 10     0F.
              In such cases, the crew can rely only upon its own            The three key factors are wind velocity air temp-
                                                                                                                             0
              resources, knowledge and experience. This paper               erature and sea temperature. If below about 4 C,
              describes a few cold weather problems, some design            sea temperature has a weaker effect on icing rate
              or operational procedures to relieve the problems,            than the other two. Nomograms have been developed
              and the need for continuing data, development and             to indicate the relation of these factors to the
              communications in this broad area.                            rate of icing. These are usually based upon sta-
                                                                            tistical analyses of actual icing cases, and the
                            2. SUPERSTRUCTURE ICING                         trends have been supported by laboratory studies
                                                                            and by mixed empirical-theoretical studies.
              Perhaps the most spectacular and certainly the most           (References 2-6)
              dangerous of all cold weather effects for small
              vessels is that of superstructure icing. With high                 2.a. Examples of Superstructure Icing
              winds, low air temperature and low sea temperature,
              ice accumulation is very rapid. For small vessels             Large ships with high freeboard experience severe
              caught in an extreme icing situation, severe con-             icing less frequently than smaller vessels. Yet,
              ditions bar on deck ice removal efforts by the crew.          they are not exempt from heavy icing. Figure I is
                                                                            a photograph of the bow of a Finnish Containership
              *Formerly of Bath Iron Works Corp., Bath, Maine

                                                     CH2585-8/88/0000- 543  $1 @1988 IEEE

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                                                                                                          Z

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                   Figure 1. Bow of a containership in Helsinki             Figure 2. The semisubmersible OCEAN   BOUNTY in
                        (Photo courtesy of Lasse Makkonen)                   Cook Inlet (Photo courtesy of L. David Minsk)

                upon its arrival in Helsinki. The mass of ice on         A very severe icing event on the East Coast of
                the rigging is typical of severe ice formation and       North America involved the semisubmersible    0
                the ten to twelve inches of ice on the deck and on       SEDNETH II, drilling on the Scotian Shelf (43 30'N,
                the winches reflect a severe encounter.                  62034'W) on the evening of February 25, 1970.
                                                                         At one time during this incident, the rig's draft
                Another example of heavy icing on a large vessel is      was increasing at.a rate of one foot per hour, and
                described by Sachse (Reference 7): the icing of          the crew was preparing to jettison several hundred
                the German freighter ELSFLETH on a voyage between        tons of mud, barite and drill pipe. In the actual
                Bremerhaven and Baltimore. The icing began south         event, the temperature rose and these extreme
                of Cape Farewell, Greenland, continuing until the        measures were not needed. The icing of this event
                ship passed Nantucket. The growth of ice was             was concentrated below the main deck of the rig.
                steady and enduring. The total ice accumulated was       (Reference 9)
                estimated at 250-300 tons forward and an additional
                100 tons amidship. The addition of such weight             2.b. Problems Created by Superstructure Icing
                above the main deck not only reduces stability, it
                grossly impedes any work on deck, may damage ma-         The problems associated with superstructure icing
                chinery, and creates both the hazard of personnel        are many. The issues of stability and buoyancy
                falling and the hazard of falling ice.                   alluded to above are familiar naval architecture
                                                                         problems associated with adding high weight. In
                Figure 2 shows the ice accumulation on  the semisub-     addition to this, icing increases the wind resist-
                mersible drilling rig OCEAN BOUNTY during one of a       ance of the structure, adding to the heeling load
                series of severe storms in lower Cook Inlet, Alaska      while decreasing stability. Design rules of the
                in the winter of 1979-80. Extremely high winds,          regulatory administrations and the classification
                very low temperatures and the very steep seas            societies incorporate criteria to meet the expected
                associated with short wind fetches resulted in ice       ice loading and wind. In operation, taking on sea
                accretions of 2 to 10 inches per day. The spray          water ballast may be an effective measure, assuming
                icing in this case extended to a height of over 30       buoyancy is not an issue. If reserve buoyancy is
                meters above the sea surface. During the most se-        critical, ice removal or jettisoning high weights
                vere icing event, total ice loads were estimated at      may be,the only solutions. Clearly, the basic re-
                500 tons, and it was deemed necessary to dump            quirements to ensure safety must be incorporated
                drilling mud to ensure adequate stability.               into the design.
                (Reference 8)

                                                                     544

             Even moderate icing creates problems. Bridge win-         Most severe icing incidents take place with the
             dows, even fitted with deicing features, can become       wind coming off a continental shore or ice shelf.
             covered by ice; safety of personnel working on deck       Moving further offshore, to provide a longer fetch
             is drastically impaired; and the operability-of           to allow the sea to warm the overlying air, or
             machinery on deck or in the rig is impaired.              moving into warmer waters (out of the Labrador
             Access to vital equipments: winches, windlasses,          Current toward the Gulf Stream) frequently prove
             ship's boats, lifesaving apparatus, deck firefight-       effective methods to terminate a severe icing in-
             ing equipment and valves may be attained only after       cident. If the windward shore or ice edge is close
             slow, laborious deicing. And the danger of damage         by, moving into the lee of the shore will result
             to equipment during icing exists.                         in a reduced.sea. However, that reduction that
                                                                       reduces spray is only very close to shore, and the
             Light icing or freezing snow on a  radome, unless         air temperature will be coldest closing the coast.
             eliminated by adequate anti-icing, will cause a           Each event is special, and requires the best data
             blind arc decreasing the safety of navigation. For        available on the current weather, oceanographic
             some radio transmitting antennas, salt water ice          conditions and knowledge of local geography.
             on an insulator can result in an arcing path to
             ground, causing both a marked attenuation and broad       From the viewpoint of design, a clean deck and
             band interference with other communications.              superstructure, uncluttered by machinery, rigging
                                                                       and other "ice catchers" is optimum. The purpose
                         2.c. Alleviating Icing                        of the unit often mandates against such total sim-
                                                                       plicity. A number of steps can be taken to provide
             There currently exist no magic cures for icing.           a cleaner structure. On offshore structures, this
             Efforts are presently underway to develop long term       includes placing bottom deck stiffeners inside the
             effective coatings to which ice will not adhere           structure, using fewer legs for a structure when
             tightly. As yet, it appears that economical coat-         possible,and, as much as possible, moving cross
             ings are still over the horizon. Heating for gen-         bracing out of the icing zone.
             eral deicing or anti-icing is tremendously costly
             (first cost, maintenance costs and energy cost) and                         3. POLAR LOWS
             is usually fitted only for small, critical areas
             and vital equipment. High pressure water jets are         While addressing the topic of sea spray icing, men-
             being investigated for this use, but successful           tion must be made of Polar Lows. Polar Lows, or
             application at sea is not yet confirmed.                  "Arctic Hurricanes" are small scale storms of in-
                                                                       tense fury and relatively short duration that are
             I have seen pictures taken a century ago of whalers       usually born near the edge of the ice cap, often in
             de-icing the rigging of a ship, wielding the heavy        an area of high horizontal sea water temperature
             cooper's mallets used to barrel whale oil, as well        gradients. Like the tropical cyclone, they have
             as axes and other tools at hand. In the mid-1980s         an eye. While they are mesoscale or subsynoptic
             the tools available for most ships are wooden             phenomena, it has been found possible to identify
             baseball bats, fire axes, hammers and crowbars.           them using satellite data. Considerable recent
             Not much progress has been made. However, studies         scientific attention has focused on these lows, as
             on anti-icing and deicing procedures continue.            reflected by a mini-symposium in Copenhagen (1984),
             (Reference 10)                                            a Workshop on Arctic Lows at the National Center
                                                                       for Atmospheric Research (May, 1985)(References 11,
             Operationally, using the customary impact tools           12) and a complete issue of TELLUS, the Swedish
             described above, it is important to start ice re-         Geophysical Society publication (Reference 13).  The
             moval efforts early. The ice as initially formed          Fifth International Workshop of Polar/Arctic Lows
             encapsulates considerable brine and is weak. The          was held last March in conjunction with the
             brine encapsulations coalesce into larger brine           American Meteorological Society's Second Conference
             pockets, leaving a low salinity ice which quickly         on Polar Meteorology and Oceanography. (Proceed-
             hardens, especially if the temperature is falling.        ings to be published)
             In many cases, an early started and continuing ice
             removal effort may control build up. If the wind          For the marine operator, the nature of the Polar
             and temperature allow, washdown with a solid stream       Low can be appreciated by the situation encountered
             of sea water from a full stream nozzle, undercut-         by the Coadt Guard Icebreaker POLAR SEA on 13-15
             ting the ice, is an effective method. Some ships          October 1985, near Barrow, Alaska (Reference 12):
             are fitted with boilers to heat this firemain
             water. If the wash water itself begins to freeze,          "The ship had just completed helicopter recovery
             or if the deck drains are frozen, the use of sea-           operations that require good weather conditions.
             water in this fashion only adds to the total ice.           Less than 5 hours later, the ship measured winds
             If adequate steam is available (and reserve feed            at 75 knots, seas estimated fifteen feet, icing
             water), this can be a most effective,ally in ice            of superstructure, low visibility in snow.and
             removal, but does pose some hazard to personnel.            the ship sustained damage from this unpredicted
             For a ship, running before the sea and wind reduces         storm. Excerpts from the POLAR SEA situation
             both the spray coming on board and the relative             report message from 13 October 1985 read as
             wind that convectively cools and freezes the spray          follows:
             into ice. Thus, downwind courses are preferable
             in severe icing situations.

                                                                  545

                     "P 140224 OCT 85                                                                      4. COLD

                       FM USCGC POLAR SEA TO AIG EIGHT NINE FIVE SIX               Cold, of itself, is a severe problem. Freezing of
                       INFO REQIFUA/COGD THIRTEEN SEATTLE WA//O//                  any exposed fresh or saltwater piping should be ex-
                                                                                   pected. Consequently, all topside firemain must be
                       SUBJ: AWS-85 DAILY SITREP: 13 OCT 85                        secured and the hydrants and risers properly drain-
                       1. 14020OZ OCT 85 POSIT: 70-53N 160-42W                     ed. Proper attention must be paid to any topside
                       2. WX: TEMP;      26F             SST:  32F                 foam systems and monitors. It is important that
                                 BARO:   29.24R          SIG:  OVC/SNOW            firemain shore connections be properly drained, as
                                WINDS:   240/67KTS       VIS:  .3NM                the ship may encounter its coldest weather in port.
                                  ICE:   OPEN WATER     SEAS:  240/7FT
                                                  CONFUSED,INCREASING.             Sanitary systems and overboard discharges are
                       3. SUMMARY OF ACTIVITIES:                                   subject to freezing. Steam condensate lines, if
                            A. ARRIVED VICINITY OF PT.BARROW LATE                  not properly drained, will freeze. Recognize that
                       P.M. 12 OCT. MAJORITY OF TRANSIT TO PT.BARROW               insulation does not protect against freezing if
                       WAS THROUGH FY THIN AND YOUNG ICE WHICH DIS-                there is no flow in the line. Thus, below deck
                       ALLOWED FOR ANY FURTHER GLOBAL LOAD DATA COL-               piping in unheated holds or compartments, or ex-
                       LECTING.                                                    posed via an unheated ventilation system to outside
                            B. 13090OU: CONDUCTED FLT QTRS FOR PAX/                air must also be isolated and drained. Compressed
                       CARGO TRANSFER  -----                                       air lines and piping, unless extremely dehydrated,
                            C. 131227U: RECOVERED HELOS       ------               will condense water vapor and freeze. How does
                            D. 13170OU: WINDS SUDDENLY AND UNEXPECT-               this affect design and operation? Questions of
                       EDLY INCREASED TO 60KTS AND CONTINUED TO IN-                this sort require careful, integrated review of
                       CREASE TO 70KTS WITH GUSTS TO 75KTS; WINDS OF               the detail design and the interplay among systems.
                       THIS MAGNITUDE NOT FORECASTED. OMEGA ANTENNA                Further questions: Must this piping system be re-
                       BLOWN DOWN. BOTH ANTENNAS HAVE BEEN RECOVERED.              routed or heat traced to prevent freezing? ...
                       ADVISED BARROW RADIO VIA H.F. OF PRESENT WINDS              What spaces are affected by unheated vent systems?
                       /WX.BARO.                                                   Unheated vent systems can carry cold air deep into
                       4. INTENTIONS:                                              a ship, causing freezing in unanticipated places.
                            A. PROCEED TO KODIAK. SOA        MAY HAVE TO BE        Even if the designer envisages that a vent cover
                       REDUCED IF CONDITIONS CONTINUE DETERIORATE."                would be in place in bitter cold, that does not en-
                                                                                   sure that it will be .... even the vent fan may be
                  In a supplementary situation report, POLAR SEA not-              running!
                  ed that winds in excess of 50 kts. had continued
                  throughout the evening, maximum seas of about 15 ft              In addition to freezing, cold can cause other prob-
                  with freezing spray, snow and fog. Sea and air                   lems. Cold lubricating oil, hydraulic oil or fuel
                  temperature remained the same.                                   from tanks near the shell can increase in viscosity
                                                                                   so as to decrease the net positive suction head at
                  Clearly, for a small vessel without the extreme                  the pump rotor low enough to result in severe
                  stability of an icebreaker, an unexpected storm          of      cavitation and rapid pump wear. If cold fuel oils
                  this ferocity and duration could lead to disaster.               are not heated well above the wax point, and fuel
                  Any vessel could expect some damage to topside                   filters closely follow the heater, rapid fouling of
                  equipment and structure from the icing and the wind              the filters by residual waxes is a possibility.
                  loads. Norwegian studies cited by Twitchell report
                  a maximum frequency of these storms of one or two                                 5. CHEMICAL EFFECTS
                  a week in the months of January and March. Much
                  study has been conducted because of the development              These effects are effects of cold, but are listed
                  of offshore resources on the Norwegian Shelf, but                separately because they all concern the effect of
                  similar storms occur in the Bering Sea and the Gulf              low temperature on chemical processes. First, and
                  of Alaska. Typically, the Polar Lows are small,                  probably most familiar is the effect of cold upon
                  with a size of 300 km or less. Wind speeds in@                   the lead-acid storage battery. The same low volt-
                  crease to over storm force in a brief time, and          the     age, high resistance characteristic that immobil-
                  storm is accompanied by very heavy snow and low                  izes your car on a cold morning will evidence
                  visibility. With the winds developing the seas                   itself in the cold marine environment.
                  over a short fetch, and with rapidly changing wind
                  direction, the seas would be very steep and con-                 Not only the lead storage battery, but dry cells
                  fused, a situation contributing strongly to ship or              are affected. Recalling their use for emergency
                  structure icing. While the fury of the storm may                 lights, transmitters, emergency beacons, etc.
                  be no greater than that of many North Atlantic or                raises the question, "What batteries or dry cells
                  North Pacific winter cyclones, the sudden, unpre-                should be used for these emergency and vital needs
                  dicted onset and the resulting steep sea makes                   in cold weather?
                  them a particular danger.
                                                                                   Finally, the now common chemical light, used for
                                                                                   lifefloat and lifejacket markers, glows but dimly
                                                                                   in bitter cold weather. Special chemical lights
                                                                                   for cold weather use burn brightly, but with a
                                                                                   short life at warm temperatures. Should two lights
                                                                                   be used, one for cold weather, one for warm?

                                                                              546

                                   6 .  TWO EXAMPLES                     On both the design and operation side, there is
                                                                         need for more up-to-date knowledge and better
             We will cite two examples of:cold weather problems.         communication with the environmental science com-
             Each is rather simple, unexpected, almost an oddity.        munity. Designers and operators should know the
             However, each caused an expensive loss.                     data and tools available to them and use them.
                                                                         Considerable progress has been made in the last
                           6.a. Cargo Contamination                      few decades through such conferences as those on
                                                                         ice and icing of the International Association for
             A ship had encountered severely cold weather for            Hydraulic Research, the POLARTECH Conferences,-..abd
             several days prior to reaching its discharge port.          the meetings sponsored by the ASME's Ocean Mechan-
             Much of the last day was in broken ice. Nearing             ics and Arctic Engineering Division.    Effort is
             the port, steam was turned on to the cargo tank             needed by operators and designers to keep abreast
             heating coils.   It was then discovered that the            of this developing technology.
             coils had not been totally drained, and that con-
             densate had frozen in and ruptured several coils.           There is a need for a breakthrough on anti-icing
             This was not discovered until after the cargo had           and deicing technology. The high cost of systems
             been significantly contaminated by water. Costs             for occasional use results in the fitting of
             included both the damage to the cargo and the re-           systems that are capable of handling moderate
             pair costs for the damaged heating coils.                   icing situations. As long as operations are con-
                                                                         ducted in regions where the icing incident can be
             Note that fresh water freezes several degrees above         expected to be short, and to be followed by a re-
             sea water, and that cold air acting on the ship's           prieve to allow deicing, this is satisfactory.
             hull can chill cargo spaces and tankage to a level          When operations are in regions where the ice of
             below that of the warmer seawater.                          two weeks ago is still on the structure, and is
                                                                         rock hard, effective deicing will be a necessity.
                    6.b. Transferring Fuel Between Tanks
                                                                         Finally, as always, there is need for excellent
             A ship bound for Montreal had encountered some sea          communications between the designer and the user
             spray icing, but nothing abnormal for the area and          of a ship or platform. This is particularly true
             the season. The engineer on watch decided to                because many cold weather problems are infrequent
             transfer fuel, bringing one of the double bottom            occurrences, almost oddities. This infrequency of
             tanks close up to capacity, normally a routine op-          occurrence is in itself a serious problem.     It can
             eration.  Some time after the transfer had begun,           result in lack of maintenance of systems designed
             it was found that the tank top of the receiving             to protect from cold, and a lack of understanding
             tank had been set up 1@-2 inches.     Investigation         by operators of both the procedures and the equip-
             revealed that the topside icing, usually of little          ments fitted to cope with cold. Further, it tends
             concern to the watch engineer, had effectively              to a collective loss of memory--from design all the
             sealed shut the tank vents. As oil was being                way to operation--of the problems of cold. Too
             pumped into the tank, the unreleased air was being          often we find that we have created or discovered
             compressed, finally producing a.structural loading          an old problem anew. To paraphrase the late George
             sufficient to buckle the tank top.                          Vedeler of det Norske Veritas,    "Must each of us
                                                                         always learn from bitter experience?"
             Like cold, superstructure icing can have effects
             that are apparent not only immediately at the cold                          8. ACKNOWLEDGEMENTS
             envelope of the structure, but manifest themselves
             deep within the ship or structure.    it is this sort       Numerous far-flung individuals have contributed to
             of complex interplay of systems that makes design           the author's interest and knowledge in this area.
             review of the integrated detail design essential to         Several generations of Coast Guard officers with
             identify potential hazards and to develop proper            extensive experience in cold weather issues have
             operating guidance and instructions.                        been generous in assistance. Particular mention
                                                                         must be made of the U.S. Army's Cold Regions
                            7. CONCLUDING REMARKS                        Research and Engineering Laboratory for continuing
                                                                         cooperation.
             This paper has been a sampler. Its purpose has
             been to provide a reminder of cold weather prob-            Parts of this overview result from data developed
             lems and to provoke thought on these issues. Note           performing related studies for Bath Iron Works
             how climatology, meteorology and oceanography have          Corporation, and for the U.S. Navy by Bath Iron
             a complex interplay with design and operational             Works under Contract N00024-82-C-2011. The views
             engineering for cold weather operations. On the             expressed are those of the author, and do not re-
             environmental side, there are many needs.     Some          flect official positions of the U.S. Coast Guard,
             key phenomena are subsynoptic. As a result, their           the U.S. Navy or Bath Iron Works Corp.
             documentation has been poor and our present under-
             standing and predictive techniques are inadequate.
             In many important areas, weather data are scant,
             and do not support the detail needed for operations
             or prediction.

                                                                    547

                                  9. REFERENCES

                  1. Hay, R.F.M., "Ice Accumulation upon Trawlers in
                           Northern Waters", Meteorological Magazine,
                           Vol. 85, No.1010, 1956, p.225.

                  2. Lundqvist, J.E. and I. Udin, "Ice Accretion on
                           Ships with Special Emphasis on Baltic
                           Conditions", Swedish-Finnish Winter Nav-
                           igation Board Report No. 23, 1977

                  3. Makkonen, L., Atmospheric Icing on Sea Struc-
                           tures, CRREL Monograph 84-2, April 1984

                  4. Minsk, L.D., "Ice Accumulation on Ocean Struc-
                           tures", CRREL Report 77-17, August 1977

                  5. Overland, J.E., C.H.Pease and R.W. Preisen-
                           dorfer, "Prediction of Vessel Icing",
                           Jnl.Climate and Applied Meteorology, Vol.
                           25, No.12, Dec. 1986, pp.1793-1806

                  6. Stallabrass, J.R., "Icing of Fishing Vessels,
                           An Analysis of Reports from Canadian East
                           Coast Waters", National Research Council,
                           Canada, Division of Mech. Engrg.,
                           Lab. Report LTR-LT-98, June 1979

                  7. Sachse, K., "Ein Sonderfall von Schiffsvereis-
                           ung von 8stlich Neufundland his vor
                           Nantucket im Februar 1968", Der Seewart,
                           Band 30, Heft 1, 1969, pp.1-9

                  8. Naumon, J.W., "Superstructure Icing Observa-
                           tions on the Semisubmersible OCEAN
                           BOUNTY in Lower Cook Inlet, Alaska,
                           Proceedings of the Second International
                           Workshop on Atmospheric Icing of Struc-
                           tures, Trondheim, Norway, June 19-21,
                           1984.

                  9. Mycyk, 0. (Rapporteur), "Session 2: Icing Case
                           Studies", Proceedings International
                           Workshop on Offshore Winds and Icing,
                           Halifax, Nova Scotia, Oct. 7-11, 1985
                           pp. 388-9

                  10. LOset, S., "Investigation on Anti-Icing and
                           De-Icing Devices for Marine Application",
                           Proceedings International Workshop on
                           Offshore Winds and Icing, Halifax, N.S.,
                           Oct. 7-11, 1985, pp. 95-101

                  11. Kellogg, W.W. and P.F. Twitchell, "Summary of
                           the Workshop on Arctic Lows, 9-10 May
                           1985, Boulder, Colorado", Bulletin Am.
                           Meteorological Soc., Vol 67, No.2,
                           Feb. 1986, pp. 186-193

                  12. Twitchell, Paul F., "Arctic Lows", Naval
                           Research Reviews, Vol. XXXIX, No. 4,
                           19879 pp. 15-22

                  13. TELLUS, Vol. 39A, No. 4, August 1987
                           (Polar Low Special Issue II)

                                                                     548

                                                   ARTICULATED LIGHTS IN ICE

                                               Shawn M. Smith & Dennis Strahl

                                               U. S. Coast Guard Headquarters
                                                       Commandant (G-ECV)
                                                   2100 Second Street, S. W.
                                                  Washington, D.C. 20593-0001

                                 ABSTRACT                          joint type hinge above the sinker.)         Safety
                                                                   chains are attached to the light assembly
             An   experimental   and theoretical    study    on    and   the sinker in case of failure       at   the
             the   behavior of   articulated lights in mov-        shackle connection.       A typical articulated
             ing   ice covers was    conducted.     A    scaled    light is shown in figure 1.
             model of a United States Coast Guard proto-
             type   design was tested under various icing          The   articulated light has the potential to
             conditions.    Parameters varied during test-         replace       numerous    conventional       buoys
             ing   included ice strength,      thickness    and    throughout    the   country.    The   U.S.   Coast
             velocity.     Data collected included in-line         Guard's      program  of    replacing     standard
             and tranverse inclination, acceleration and           channel buoys with these lights is now over
             axial loading at the hinge.       A clear depen-      five    years old,   with over 20     articulated
             dence   on ice velocity and ice strength was          buoys   having    been   deployed.
             demonstrated in describing the            model's
             behavior.     A  computer program was concur-         The   purpose   of the study     of   articulated
             rently developed to predict in-line         motion    lights   in ice was to model and      predict the
             and axial loading at the hinge.                       structure's response to moving ice. The
                                                                   study preceeded the placing of the articu-
             The   United   States Coast Guard has        since    lated lights in ice-covered waters.
             deployed articulated lights modified for
             ice   conditions.     Coast Guard experiences                        THE ICE DESIGN
             with these structures is reviewed.
                                                                   Since ice loading is expected only near or
                                                                   above the waterline, the only modification
                             INTRODUCTION                          made to the articulated light pictured in
                                                                   figure I was to replace the top assembly.
             Articulated    lights are aids    to   navigation     On the    modelf    this was    accomplished    by
             with   a narrow watch circle,      used to    mark    merely   capping    off the top of    the    steel
             channels    with      greater  precision      than    cylinder.     On the actual light,     the plat-
             conventional    buoys.     They   are   compliant     form    subassembly was removed and      replaced
             structures,    designed    to  withstand     minor    with    a Polycarbonate     Dome Ice   Top   Sub-
             environmental    loading  and to yield to      se-    Assembly.    This ice top includes      ..sacrifi-
             vere loading conditions.        The basic con-        cial" foam dayboards.        A similar dome was
             struction consists of a        narrow vertical        placed on the ice buoy deployed in             the
             pipe  with    a  flotation     collar   providing     Mackinac     Straits   with good      success [ 5
             vertical stability.     It oscillates around a        Figure 2 depicts the ice design.
             universal coupling connected to a sinker.
             The   entire   structure is    designed   to    be    At  certain    ice thickness,    strengths     and
             nearly neutrally buoyant.                             velocities, the ice cover will submerge        the
                                                                   articulated light.       This is particularly
             The Coast Guard design features a series of           likely in the Great Lakes where, at the
             flanged   steel 12" pipe sections,      open    to    height of winter conditions,       ice ranges in
             flooding, a flexible foam collar to provide           thicknesses up to five feet in the channels
             buoyancy,   a    cast  iron   counterweight     to    these   lights may mark.      As configured for
             reduce tension on the sinker, a maintenance           icing conditions, the articulated light
             platform with dayboards, and the light.               will employ the "push-down, pop-up" con-
             They are designed to mark waters 25 to 60             cept.    As thin or weak ice impacts the
             feet deep.                                            structure,     it will incline until           the
                                                                   restoring (buoyancy) force exceeds the ice
             The light assembly is anchored to the sin-            failing strength, at which time it will
             ker with a mooring bail connected to the              rebound toward the vertical position.           In
             bottom cylinder.       A steel shackle is led         stronger, thicker ice, the structure will
             through the mooring bail and pinned to a              incline until submerging.        When the ice
             steel plate cast into the concrete.             (A    cover passes over, or when the ice weakens,
             recent design modification uses a universal           the structure will "pop back up".

                                                               549 United States Government work not protected by copyright

                          ICE PROPERTY REFRESHER                    The higher values are characteristic of
                                                                    hard winter ice, the lower values for
              The   ice property most influential in       ice-     spring ice.
              structure interaction is ice strength.         in
              general,     ice    strength increases       with                 TABLE 1 (Ice Strengths)
              decreasing temperature, decreasing brine
              content, increasing ice age, and increasing                              EatLgmg ipgll ggg-igni2211
              thickness.                                            Compression            50_1BOO         7S-400
                                                                    Flexure                44-414          65-200
              Ice is much stronger in compression than in           Shear                  40-132          60-120
              tension and its strength is            generally
              characterized      by  its  failure`mechanism,        The variability of ice properties      makes the
              principally bending (flexure), crushing,              task of modeling ice strength and failure
              buckling or shearing. The vast majority of            mode complex. One usually has to choose an
              reports    concerning ice-structure     interac-      average,   representative property,      or else
              tion list crushing or bending as the domi-            select a worst case scenario.
              nant ice failure modes. Crushing strengths
              of ice are generally two to four times that                        THEORY OF RESPONSE
              of bending.     Many engineering designs have
              taken     advantage of the lower          bending     Motion of    an articulated light in wind,
              strength    of.ice by building marine      struc-     waves   and current can be      predicted  using
              tures with inclined components at the ice-            techniques similar to those employed by
              structure interaction point [5,13,16].                Bose and Rao [1] and Elledge [3].        In pre-
                                                                    dicting the structure's response to ice
              Crushing occurs when a moving ice mass                loading, these techniques were utilized,
              strikes a vertical or, nearly           vertical      with the added assumptions that the ice
              structure.      Michel     and Toussaint (11]         impacting the structure is an isotropic,
              demonstrated     three zones       of   crushing      constant    thickness,     constant      strength
              behavior:    ductile, transition and brittle.         cover;    and  that waves will not occur cnn-
              Although ice failure occurs in all thre         ,e    currently with ice.       It is realized that
              zones,      crushing      strength     generally      such assumptions reflect only a portion of
              increases with increasing strain             rates    the conditions in nature; however they were
              through the ductile zone, peaks in the                made to simplify the calculations.
              transition zone, decreases and then levels
              off in the brittle zone.       Under conditions       The articulated light is first divided into
              of quick loading,         ice behaves like a          discrete increments; drag forces due to
              brittle material.                                     wind and current calculated; and moment
                                                                    arms calculated about the hinge (shackle).
              Ice failure by bending on inclined struc-             Added mass and the structure's mass moment
              tures is dictated by a decrease in the                of inertia are calculated, together with
              horizontal component of ice pressure and              the    buoyancy    force and       gravitational
              the appearance of a vertical component                forces. Finally, the angular acceleration,
              proportional to the angle of structural               change in angular velocity and the resul-
              inclination 191.       The failure of an ice          tant change in the light's angle of incli-
              sheet in bending is generally preceeded by            nation are determined.      These calculations
              the formation of radial cracks propagating            are repeated at predetermined time inter-
              outward from the loading point.           Circum-     vals, and the incremental change in incli-
              ferential cracks then form as the ice sheet           nation applied to the previous angle to
              is bent, until the flexural strength at one           arrive at the instantaneous inclination.
              of these circumferential cracks is exceeded           This method was proven to be successful in
              by the load an the ice.        The distance of        predicting a model's motion by Elledge [3].
              this failure is apparently related to the
              characteristic length of the ice, a proper-           In predicting the li,ght's response to ice
              ty related to its elastic modulus.                    loading, the computer program written by
                                                                    Elledge was adapted to include an ice
              Tracks    behind isolated structures      in   ice    loading   moment.    The impacting ice     sheet
              fields can often give a clue as to      the mode      heels the    structure    over until     the ice
              of    failure  which   occured [6,8].     A  path     fails,   or the structure is submerged.         it
              roughly    equal to the     structure  diameter,      was assumed that the ice would fail in       one
              with small rubble piles on either side,        is     of two modes, bending or crushing.       The ice
              generally    the    result  of ice   failure   by     failing   forces   and resultant moments     for
              crushing or shearing.       Bending failure    is     these   modes were   calculated.     Then,   the
              characterized     by a series of     circumferen-     other environmental and structural       moments
              tial   shaped   cracks on either side of       the    are  summed.     If these moments exceed the
              track.                                                ice failing moment, then the ice is assumed
                                                                    to   fail.      If not,     then    the    light
              Table     1  lists   extreme   ranges   of     ice    inclination    increases as determined by the
              strengths    measured by various     authors   as     velocity of the ice and the selected       time
              well   as   recommended design values        [10].    increment.    The   forces   and    moments  are

                                                                 550

              recalculated, until ice failure occurs.                The model was tested under a variety of ice
                                                                     conditions at the U.S. Army Corps of Engi-
              The calculation of which angle of structure            neers Cold Regions Research and Engineering
              inclination    the ice failing mode      ..shifts"     Laboratory (CRREL) in       Hanover,    N.H.     The
              from    crushing   to bending posed a      problem     CRREL    test basin measures 30 feet wide,         a
              since   there is no well defined       threshold.      feet deep and 120 feet long.          Ice is grown
              Danyaa and Bercha [2) found that       ice    fails    to specification by variation of room          tem-
              by crushing at an angle of up to       15 degrees      perature     and  time to attain      desired    ice
              from    the   vertical.   From 15-30   degrees     a   thickness     and  strength.      Ice was    seeded
              crushing    made could be    assumed,    yielding      using    a   urea  doped    water     solution   of
              conservative forces.      Between 30-45 degrees        approximately one percent concentration, as
              a bending failure could be assumed.           Saeki    described in Hirayama [7].            Ice sheets are
              et   al   (13)  found     0-10  degrees    to    be    pushed    along   the tank by means of a       D.C.
              crushing;     10-25 degrees transitional;      and     motor driven carriage which spans the width
              above 25 degrees, bending.                             of the tank.
              Obviously, the type of failure which takes.
              place     depends    on   which    kind  of    ice     Just prior to testing,       the ice was sampled
              strength, bending or crushing, is surpassed            to    determine    its     thickness,     flexural
              first.    For the purposes of this study, an           strength and elastic modulus.         The flexural
              angle-dependent     formula was derived which          strength was measured using           a cantilever
              assumed   failure    to be   somewhere     between     beam test;      the elastic modulus was deter-
              crushing and bending.                                  mined     by measuring the            characteristic
                                                                     length as described in Kato and Sodhi 181.
                      FORCES TRANSMITTED TO THE HINGE                The crushing strength of ice was then cal-
                                                                     culated, -again following a relationship
              Since   the articulated light is designed to           reported in Kato and Sodhi,           which uses the
              quasi-neutrally     buoyant,    the   hinge will       downward flexural strength to arrive at the
              normally    see only a small load due to net           compressive strength of ice.
              buoyancy      (total buoyancy      minus      total
              weight).    This force should remain somewhat          In   addition to instrumented measurement of
              constant    as  the structure inclines        since    the   structuve's     motion,     an    inclination
              the hinge   is moment free.      If ice    impacts     panel was mounted behind the structure from
              the  structure     however,     an   axial    force    a   foot bridge which spans the test         basin.
              component     will   arise   due   to    friction      A   video tape record of the tests war.        then
              between       the     ice      and     structure.      made.
              Additionally,      if the structure becomes
              frozen-in, potentially high forces would be                              TEST RESULTS
              generated in breaking the adfreeze bond
              (4,12].   Friction    forces    were   calculated      Tests    were   conducted on five ice       sheets,
              using     the  standard      friction    formula,      with three velocities per sheet, except the
              modified    by  the   instantaneous     angle    of    fifth    (2   velocities),     yielding   fourteen
              inclination     of    the    structure.        The     separate tests.      Table 2 presents the model
              resultant     axial load can then be     resolved      ice characteristics and velocities used:
              into vertical and horizontal components to
              ascertain     forces imposed on the hinge      and          TABLE 2 (Ice Sheet Characteristics)
              sinker system.
                                                                     sheet Thlglinggg         gtrgugth       YgIggitz
                               MODEL TESTS                               1      1.5 in      4.2/S.5 psi      .16,.32,.49
                                                                        11      2.0 in      3.8/7.0 psi      .08,.32,.49
              A model of the prototype articulated          light       111     1.3 in      4.8/10.4 psi     .08,.32,.66
              was constructed based on Froude scaling and               IV      1.2 in      7.8/20.9 psi     .16,.32,.66
              a water depth of 30 feet.               The same           V      2.0 in     11.9/21.0 psi     OBf.32
              materials were utilized for the model as
              a r d-  found  on   those    lights     currently      Note:    Strength    values are upward/downward
              deployed:     steel  pipe,   cast iron counter-        flexural strength.       Velocities are ft/sec.
              weight,   surlyn    foam and the paint system.         Strength is pounds/square inch.         All values
              A  battery compartment and the        light were       rounded off.
              not modeled, allowing room instead for
              instrumentation.      A   1000 lb capacity load        On the first four ice sheets, the model was
              cell    measured axial loading at the        hinge;    cleared from all ice prior to testing.           On
              inclinometers    were     placed   orthogonal    to    the   fifth ice sheet,      the model    was   left
              each other to measure motion in the in-line            frozen-in to simulate a similar          situation
              and transverse planes of motion; and torque            in the     environment.      A summary    of   test
              balance   accelerometers were      installed     to    results    is   given in Table 3.       Angles   of
              measure structural vibration.        A ball joint      inclination given are the maximum angles,
              was  used     to attach the structure to       the     in   degrees,    from the     vertical   achieved.
              tank bottom.                                           The failure mode is the dominant mode
                                                                     observed during the tests.

                                                                  551

                       TABLE 3 (Model Test Results)                length.    Figure 6 shows a test run pre-
               Sheet Velocity            Ang19 f@IjVrg Mgjg        dominated by bending failure of the ice.
                  1    .16 fps       41.5            Bending       Figure 7 demonstrates crushing failure.
                  1    .32 fps       44.0            Bending
                  1    .49 fps       45.0            Crushing                  THEORETICAL FINDINGS
                 11    .08 fps     Submerged
                 11    .32 fps     Submerged                       The computer program written by Elledge [3]
                 11    .49 fps     Submerged                       was adapted to predict response to ice
                 111   .08 fps       28.9            Bending       loading.   Emperical    results from the model
                 111   .32 fps       33.5            Sending       tests    were  added to refine    the  program,
                 111   .66 fps       45.0            Crushing      specifically the maximum ice failing       angle
                 IV    .08 fps       43.9            Bending       and   the  angle of rebound.      The  computer
                 IV    .32 fps       39.3            Bending       model   predicts reasonably well the      struc-
                 IV    .66 fps       45.0            Crushing      ture's     response,    and   in  every    case,
                  V    .08 fps     Submerged                       predicted      the structure's     submergence.
                  V    .32 fps     Submerged                       Figure 4 provides a sample comparison of
                                                                   the computer model results (solid, straight
               The typical test   proceeded in the following       line) with visual records (dashed line) and
               manner:    The  ice was set into motion      and    model test results (solid, jagged line).
               impacted the structure with no visible
               structural rebound. The structure inclined                         FIELD EXPERIENCE
               at a steady rate.         Approximately 5-10
               degrees before failing, the ice surrounding         Several    articulated      lights  have     been
               the     structure   rode  up     the    cylinder    positioned     as aids to navigation    in    ice
               ,slightly,  forming a circumferential crack.        environments,      including    one    in     the
               The  ice   then failed about this crack      and    Chesapeake     Bay and two in the Great Lakes.
               split   to  either   side    as  the  structure     Only    one of    these,  the  Lake   St. Clair
               rebounded.   The rebound did not stop at the        structure,     has  survived    the     winters
               site of the initial circumferential       crack,    relatively     unscathed  and it has   been    in
               instead the ice was crushed/sheared for             place for two years.
               some additional distance before stopping
               and repeating the process.                          To prepare for winter, the top assembly,
                                                                   including the light, dayboards, lantern
               A typical in-line inclination    plot is shown      stand and platform, is replaced by the
               in  Figure 4 (jagged line;     the other lines      Lexan ice dome assembly shown in figure        3.
               will    be explained  later).    The  structure     In the spring, the process is reversed.
               inclines as the ice pushes against it,              The    Chesapeake Bay Bridge        articulated
               until the ice failing force is exceeded.            light, on one occasion, became unshackled
               The     structure  then   rebounds,      perhaps    from the sinker.     On another occasion, the
               failing the ice several times (noted in the         foam collar was found to have absorbed much
               visual    record) before the process          is    more water than usual.      Ice conditions the
               repeated.    Little transverse motion was           past two years in the vicinity of this
               observed, as might be expected in the               light had been on average one to four inch
               uniform ice sheets produced in the lab.             pack ice, generally with about seventy
                                                                   percent coverage (although ice floes coming
               Typical load cell readings are depicted in          off the Chop Tank River were observed to be
               Figure 5.     Generally, the load decreases         up to 12" thick).        Upon one inspection,
               with    increasing angles of   the   structure,     the   structure   was observed leaning      20-30
               after an initial peak at about 12 to 20             degrees in 3" running slush ice, with newly
               degrees. When the structure rebounded, the          installed "sacrificial" dayboards missing.
               load increased. This is most likely due to
               the decreasing axial component of buoyan-           The Munuccong Channel Junction light was
               cy. There is one major ice failure, either          discovered off location and a larger sinker
               bending or crushing, followed by a series           was retrofitted to provide a larger bearing
               of smaller failures.                                surface.    The    light  had apparently     been
                                                                   dragged    along the muddy        bottom.      On
               The average angle of inclination before ice         another    occasion,    the   sinker  bail    was
               failure increased with velocity, as did the         observed to have worn excessively, probably
               frequency   of these   failures.     There   ap-    due to loss float floatation       causing    in-
               peared to be a shift in the type     of failure     creased    stresses at the hinge.     The light
               as well,   with bending predominating at the        has been removed from     station.      Average
               lower     velocities  and    crushing  at    the    ice   thickness   in the channel    during the
               higher.    This agreed& with the findings of        height of winter is five feet.
               Haynes et al [6). Bending failure occurred
               at higher angles,     crushing occured at the       On the first occasion to inspect the         Lake
               nearly   vertical   angles.     As   might    be    St.   Clair    Light after  installation,     the
               expected,   the failure angle   increased with      Lexan   dome was discovered smashed and       ice
               the  elastic modulus and the     characteristic     was   packed   around the top of    the    light.

                                                                 552

            Ice   conditions    at the time of     inspection                         REFERENCES
            were 6-8 inch of refrozen pancake ice, 9/10
            coverage.    On another occasion, the Light's           [1] Bose,  K. and Rao, E., "Development of a
            Ice   Dome assembly broke off at the        flange      Theory for Analysis  of Articulated         Beacons
            above    the  float.       Ice   conditions     were    for  use   as   Offshore    Light    Structures",
            severe    - up to six feet of       moving  packed      Bulletin de L'A.IS.M., P. 13-19, 1979.
            brash ice, full coverage.         The floatation
            collar    was   also found to have     been     torn    (2] Danyas,    J. and Bercha, F., "Investiga-
            slightly and the dayboards were        destroyed.       tions of Ice Forces on a Conical Offshore
            After    three months on station,      the   light      Structure",    Ocean Engineering,      Vol.3,p.
            had been dragged about 100 yards.                       299-310, 1976.
            Of the original 23 deployed lights, only 10             [3] Elledge,L.,"Dynamic Study of Articula-
            still remain an station.        The other, non-         ted Beacon",Thesis  Dissertation, URI, 1983.
            ice lights, suffered from much the same                 [4] Gaythwaite, J., The Marine Environment
            problems as the ice structure, principally
            failure     at     the   hinge/sinker       joint.      and Structural Design, 1981.

                            MODIFICATIONS                           [5] Glahe, P., Recent Developments in a
                                                                    Navigational Buoy for use in Ice Condi-
            Based     on    these    experiences,      several      tions, U.S.C.G. Report, 1980.
            modifications      are planned,        with     some
            already implemented.       First, the dayboards         (6)  Haynes    et    al,  Ice Forces    on   Model
            have     been     changed   to     Surlyn       foam    Bridge Piers, CRREL Report 83-19, 1983
            "breakaway" dayboards.         Second, the foam
            float collar will be made longer and         thin-      [7] Hirayama,K., Properties of Urea-Doped
            ner to facilitate buoy tender deck handling             Ice in the CRREL Test Basin,        CRREL   Report
            operations.     It will also be made of a dif-          83-8, 1983.
            ferent material. Shrinkage of the original
            foam   floats had occurred,      decreasing     the     [8] Kato,H.  and Sodhi, D.,     Ice Action on
            volume    of  the float and thereby       reducing      Pairs of Cylindrical and Conical Struc-
            the net upward buoyancy.       These floats also        tures, CRREL Report 83-25, 1983.
            were subject to water intrusion due to
            inadequate "close cell" properties, further             [9] Michel, B., Ice Pressure on Engineering
            reducing buoyancy.                                      Structures, CRREL Monograph III-Blb, 1970.
            More flexible (neoprene) and reliable           uni-    [10] Michel,     B.,   "Advances    in Ice Mecha-
            versal bearings will be used at the sinker-             nics", P.O.A.C. 1981, p. 189-203.
            light connection.      Problems with the sinker         [11] Michel B. and Touissant N.,"Mechanisms
            bail     are  partially    a   secondary    effect      and  Theory of Indentation of Ice         Plates",
            caused by the loss of float buoyancy.        Re-        Symposium on Applied Glaciology, 1976.
            duced buoyancy results in the loss of pro-
            per   tension on the hinge,      leaving the en-        [12] Sackinger, W. and Sackinger, P."Shear
            tire   weight    of the    structure   "bottoming       Strength of the Adfreeze Bond of Sea Ice to
            out" against the sinker       bail.    Ultimately       Structures",    P.O.A.C. Vol. II, p.607-614,
            the   sinker    bail   was chipped out     of   the     1977.
            concrete and failed at the welded joint.
                                                                    [13] Saeki, H. et al, "Experimental Study on
            A   thicker  lens will be used for the       Lexan      Ice Forces on a Cone Shaped and an Inclined
            Dome     and  longer    top    sections   will    be    Pile Structures", P.O.A.C. Vo1 II, p. 695-
            mounted     to  give the dayboards     a   greater      706, 1979.
            height of eye. Finally, thicker flanges
            will be used to prevent shearing off of the             (14]   Smith, S.,   "Response of Articulated
            top   section     due   to the   severe    bending      Beacons   in   Ice",    Thesis      Dissertation,
            moments     caused   by    collisions   and     ice     URI.,1984.
            loading.
                                                                    [15] Strahl, D., "Articulated Lights", USCG
            It   is hoped that   these modifications        will    ATON Bulletin, Vol 17. No.2, p.10-11, 1988.
            solve the major problems encountered with
            the   articulated lights.    Five of the     new        [16] Tryde,    P.,   "Ice Forces Acting on In-
            designs    are scheduled for     field    testing,      clined   Wedges and Cones", Ocean Engineer-
            although none of them will be placed in icy             ing, Vol 3, 1976.
            locations until the designs are proven in
            the more benign environment.         Ideally, the       [17] Walker, S., "Articulated Beacons Could
            articulated light will eventually be placed             Replace Buoys", Commandant's Bulletin, 14-
            as a year round navigational aid in criti-              82, U.S. Coast Guard, p. 30-31, 1983.
            cal navigation locations.

                                                                 553

                                                 U@
                                                                  FM&PL/M -T

                                                                                                                                                                                   wwo

                                                                                                                :rT

                              Figure 1             C.G. Articulated                                                                     Figure 2             Articulated Light
                                                   Light Design.                                                                                             Ice Top Design.

                                                                                         Figure 3 -,Ice Dome
                                                                                                               Assembly.

                                              COAST GUARD CG-L412                                                                    C AST GUARD       CG- I all
                                                   ;4           1.0 Y.        Be.,.                                                                     ca V.I.   98.00.1.
                                             Stop-Glli WiSOH-s.                                                                   Stop-88 I DOI 0M.G.

                            45.0                                                                                      [Be

                                                                                                                      Ic
                            I S , 05;__:

                            10.8                                                                                      4E

                         C  9.0                                                                                       26,

                                                                                                                0
                                                                                   75
                            -9.0                                                              SECONDS                 -2                                                             SECONDS
                          c-'e.8                                                                                      -4

                            27.0                                                                                      -6
                          136.0                                                                                       -8

                           -45.0

                      Figure 4               In-line Inclination Plot. Jagged                                   Figure 5             Plot of Axial Loading at Hinge.
                                             line is inclinometer record;                                                            Ice Sheet III.
                                             dashed line is visual; solid line
                                             is theoretical. Ice Sheet IV.

                               1@4," y4f,

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                                         Of
                                                                                                                      6T

                                    W                               @0

                         Figure 6             Typical Ice Failure                   by Bending.                  Figure 7             Typical Ice Failure by                      Crushing.

                                                                                                           654

                                                       ARCTIC ICE ISLAND CORING FACILITY

                                                                Michael Gorveatt
                                                                  Mark Chin Yee

                                                       Bedford Institute of Oceanography
                                                                  P.O. Box 1006
                                                             Dartmouth, Nova Scotia
                                                                  Canada   B2Y 4A2

                                      ABSTRACT                                delivered to the PCSP in Resolute Bay, but for
                                                                              logistical reasons, the 1600 metre runway was not
               In 1982 a three-by-seven kilometre iceberg calved              completed and the planned delivery by Canadian
               from the Ward Hunt ice shelf on northern Ellesmere             Forces Hercules aircraft had to be delayed.         The
               Island and began moving west into the Arctic                   same feat was attempted in 1986 with the same
               Ocean.    The Canadian Department of Energy, Mines             result.   PCSP then negotiated with the Canadian
               and Resources used this as an opportunity to take              Forces to put the winch and a bulldozer on the
               sediment samples and piston cores from this area               island via a Low Altitude Parachute Escape System
               of the Arctic Ocean and other areas as dictated by             (LAPES) drop.    This was successfully carried out
               the track of this Ice Island. With the assistance              in the early spring of 1987.
               of the Engineering and Technical Services Division
               of the Department of Fisheries and Oceans, a                                        BUILDINGS
               substantial sediment sampling system was de-
               veloped, built, and installed on the island.                   There are many different buildings on the Ice
                                                                              Island, each with special functions.          Buildings
               This sediment sampling system consists of a winch,             that house essential camp functions include the
               gantry, and ice melting system capable of taking               generator hut , the radio /of f ice hut , the
               piston cores to a water depth of 4000 metres.                  navigation hut, the sleeping huts, and the all
               Sampling is carried out through a 1.5 metre                    important dining hut.       These buildings are the
               diameter hole melted through ice 44 metres thick               responsibility of the PCSP.          Other buildings
               by a 249 kW melting system.      This paper describes          designed specifically       for piston coring and
               the evolution, the logistics, and capabilities of              sampling were constructed by the Atlantic
               the sampling system.                                           Geoscience Centre (AGC).         These AGC buildings
                                                                              have grown into quite a complex.             The main
                                                                              building is the coring hut which houses     the winch,
                                                                              gantry, hydro-hole, office, and core working lab.
                                    INTRODUCTION                              Attached to this is the pump room which contains
                                                                              the hydraulic power pack to run the coring winch.
               The indication that another ice island had calved              on the other side of the coring hut is the hut
               from the large Ward Hunt ice shelf was discovered              which houses the oil-fired hot-water system used
               by the geographer and , ice specialist Martin                  to melt the hydro-hole in the ice and to keep it
               Jefferies during his 1982 summer research on                   open for the summer sampling program.              This
               northern Ellesmere Island. George Hobson,                      building also contains the diesel generator which
               director of Canada's Department of Energy, Mines               provides the power for the coring facility.        Part
               and Resources Polar Continental Shelf Project                  of the complex is a 3 by 4 metre Weatherport tent,
               (PCSP) identified this ice island on August 11,                which is used for storage.     Each of the buildings
               1983. At this time it was offshore of Ayles Fiord              on Ice Island is surrounded by ablation shields,
               and moving to the southwest.      A telemetering buoy          which are sheets of plywood, painted white to
               was placed on the island so that overflying                    reflect the heat from the sun to retard melting
               aircraft could plot its location until the PCSP                and erosion around the footings during the summer.
               were ready to build and man a station. (Fig. 1)

               The Ice Island, [named Hobson's Choice after its                                  HANDLING GEAR
               founder] , measures approximately 3 by 7
               kilometers, is 44 meters thick, and presents an                The semi-permanent nature of an installation on
               excellent semi-permanent floating station from                 an ice island of this type permits the use of
               which to study the relatively unknown Arctic                   handling equipment with somewhat greater sampling
               Ocean.    In 1984, plans were made and funds were              capability than might be found on most arctic ice
               found to set up and man a small camp on the island             camps.   The primary concern is that erection is
               to operate a gravity corer and a 3.5 KHz sub-                  possible using a limited variety of hand tools
               bottom profiler.     Piston coring was. attempted in           with little or no machinery available for
               1985 without success.       In 1985, a new winch was           carrying, lifting, or placing of components.

                                                       CH2585-8/88/0000- 555  $1 @1988 IEEE

                Most operations involve lowering sampling devices                to ease handling of the core barrels and
                through the hydro-hole using the winch located at                heat probe.
                one end of the coring hut.        The cable is led            e. The supports should be detachable at ice
                almost horizontally from the winch, through an                   level in case the coring building had to be
                intermediate (heel) block, up over the main sheave               moved on its skids because of excessive
                block hanging from a gantry, then down the hydro-                melting or deterioration of the hydro-hole.
                hole (see Fig.2).       The use of the heel block
                minimizes the side loading on the gantry, and                              SUPPORTING STRUCTURE
                reduces the overturning moment on the winch.
                                                                            The steel structure is assembled from pipe
                Construction of the coring facility took place              sections with bolted flange joints.     Each section
                during the spring of 1985, amidst all the other             weighs a maximum of 70 kg so that they could be
                preparations for the sampling program on the                handled by twopeople. The winch, heel block, and
                Canadian Ice Island.      A smaller, more portable          gantry are mounted on columns frozen into the ice
                winch which had been used on earlier ice camps,             to a depth of 2.0 metres.    The columns are fitted
                was installed until the new winch could be                  with flanges below ice level in order to increase
                delivered. The temporary winch was attached to the          the pull-out strength by increasing the shear area
                wooden beams supporting the floor of the building,          of the supporting ice. Where the columns protrude
                with most of the load taken by a restraining cable          through the floor of the coring hut another
                shackled to the back of the winch and anchored to           flange connection is provided at ice level to
                a pipe frozen into the ice.      The heel block was         allow removal should the building have to be
                held in place by a heavy wire strap wrapped around          moved.
                a structural steel member spanning two of the
                floor joists. Positioned over the hydro-hole is a           The gantry was raised by three meters, on columns
                standard portable workshop gantry, which straddles          which are cross-braced by wires and turnbuckles
                the coring hut.    The gantry is rated at 4500 kg           for lateral stability, to give approximately 6.8
                and was mounted on a one-metre high wooderi                 meters headroom over the hydro-hole (Fig. 3).        A
                trestle frozen into the ice. The gantry also had            jig was constructed from available timber on site
                guy wires attached to the base of the building at           to locate and support the columns during freezing
                the opposite end from the winch in order to resist          in.   The one utilization of mechanical lifting
                any side loading on the structure.                          assistance was the use of a helicopter in removing
                                                                            and re-positioning the gantry atop the steel
                A limited sampling operation was carried out                structure (fig. 4).       Finally, the top of the
                during the late spring and early summer of 1985             gantry was guyed as added security against side
                which included bottom photography, plankton tows:           loading.
                grabs, dredges, and gravity coring.       Finally in
                August, with the necessary equipment assembled to           The heel block is shackled to a pivot held by two
                do piston coring using an 820 kg core head, a               structural members frozen two metres into the ice.
                trial run was conducted using a 3 meter barrel.             Based on our previous sobering experience, much
                Everything appeared to go smoothly until pullout            debate took place about the way that the heel
                was attempted. The resulting line tensions pulled           block support was to be installed. It was decided
                the heel block up through the floor of the coring           to angle the bottom of the columns away from the
                building, which in turn altered the rigging                 hydro-hole to avoid the weakened ice around the
                arrangement.     The cable angle now produced an            hole, and also the possible melting that may occur
                upward force on the winch, unresisted by the                in that area. An additional flange was installed
                horizontally acting restraining cable.         Despite      on each support to resist the potentially high
                valiant attempts to pull out the core barrel stuck          pull-out forces.
                in the ocean bottom, the wire cable had to be cut
                in order to save the winch, which by now was                The winch is bolted to steel beams running under
                steadily creeping toward the hydro-hole.       It did       both sides of the base and spanning the columns
                not take much imagination to see that piston                located near each corner of the winch. The
                coring was going to require the coring winch that           original intention was to place the supporting
                was stranded in Resolute Bay, and a completely              columns through holes in the existing floor, but
                redesigned support for the winch, heel block, and           site conditions made it simpler to mount the winch
                gantry.                                                     outside, then to extend the building at the winch
                                                                            end. This also added some much needed room to the
                A number of options were considered for the                 working area inside the hut.
                supporting structure with certain constraints
                placed on the design:                                                          CORING WINCH
                   a. The forces must all be transferred to the
                      ice, not to the  building.                            The hydraulic winch is a robustly constructed ma-
                   b. All components and structural members must            chine capable of bare-drum line pulls up to 28.5
                      be light enough to be hand carried and                kN (6400 lbs) at 55m/min (180ft/min), when powered
                      assembled.                                            by the dedicated 43 kW (58hp) diesel /hydraulic
                   c. Steel is the preferred material since some            pump unit (see Fig. 5).       The primary hydraulic
                      basic steel welding is available on the Ice           system utilizes two pumps in parallel, delivering
                      Island should modifications become                    oil to an open loop circuit.           Whenever the
                      necessary.                                            horsepower limit of the prime mover (the diesel
                   d. The height of the gantry should be     increased      engine) is approached, one of the pumps is

                                                                       556

                automatically unloaded, which effectively drops             ships there is mechanical assistance available to
                the winch speed by 50%, but doubles the line pull           help with the moving and rigging of the corer.
                capability by allowing the hydraulic pump to                The second is there are no real constraints on
                attain higher pressures without stalling the                the size of the piston corer assembly used from a
                diesel engine.    The winch has many of the basic           ship since there is usually enough space to rig
                features expected of a hydraulic winch:                     the corer and collect the sample.       The third i s
                   a. infinitely variable speed control, with good          most ships carry a deck crew to assist the scien@-
                      low speed high torque characteristics                 tist in handling the corer and operating the
                      necessary for this type of operation;                 mechanical handling equipment.         None of these
                   b. excellent resistance to wet environment;              things exist on Ice Island.        Chain blocks and
                   c. high power to size ratio;                              come-alongs" are used to compensate for the lack
                   d. self-contained and simple in design.                  of mechanized and manual help.

                The drum can hold up to 4000 meters of 9.5    mm (3/8       The problem with the trip arm arrangement for the
                in.) diameter cable, and is supported on      one end       corer was not as easy to overcome.        Due to the
                by a hollow stub shaft suitable for slip ring               limited size of the hydro-hole, it was a very
                mounting if used to handle electromechanical                tedious and nerve-racking experience      to lower a
                cable. On one side of the winch is an independ-             piston corer with the trip arm only       inches from
                ently driven warping head (capstan) which is                the side of the hole. Contact with the side could
                convenient for handling short lifts around the              pre maturely trip the corer with disastrous re-
                hydro-hole.                                                 sults to equipment and personnel. On average, the
                                                                            sides of the hydro-hole would grow inward at the
                The winch and pump units are welded steel fabri-            rate of about 5 cm per week, so reaming the hole
                cations with frames that completely surround the            had to be done often to ensure the corer would not
                drum and drive components.     This design provides         catch on the ice walls. After many long discuss-
                strength, rigidity, and protection for vulnerable           ions of this problem we decided to streamline the
                parts, which proved critical when the winch was             corer.   This would allow us to cut and maintain a
                air dropped onto the ice in 1987.     The undersides        smaller hydro-hole.    Our second consideration was
                of the frame are enclosed skid or toboggan shaped           safety, which    meant eliminating the trip arm
                .to facilitate dragging the units across the snow.          assembly.   This was done by using an acoustic re-
                                                                            lease mounted    just above the core head in the
                                       MELTER                               same manner as the trip arm assembly.         Using a
                                                                            separate pinger (EDO 462;12KHz) attached a known
                The melter system (Fig., 6) used to cut the 1.5             distance from    the end of the corer, we could
                meter diameter hole through   44 metres of ice is a         watch the corer's descent and with the aid of a
                large and powerful system.     This melter uses re-         graphic recorder, control the distance between
                heated melt water as the melting agent.          Since      the corer and the ocean floor. When the corer was
                this water will become sea water, which would               the prescribed distance off bottom (5 m) we could
                eventually corrode and contaminate the boilers, a           talk acoustically to the release and trigger the
                system of transferring heat from a glycol closed            corer. This system worked very satisfactorily.
                loop to the seawater melting medium was devised.
                This allowed a mixture of glycol and water to be            There were still problems de-rigging the corer.
                heated in the two boilers and circulated through a          Limited room in the core hut made it impossible to
                stainless steel heat exchanger by a 5 HP steel              lay the corer down horizontally to unscrew the
                circulator pump (Fig. 7).     A second circuit ear-         barrels.   These had to be separated in the vert-
                ploying a 1.5 HP submersible vertical turbine pump          ical mode, resulting in the loss of 6 to 10 cms of
                in a stainless steel housing draws the surface              core before we could cap off the upper barrel.
                water from the hydro-hole and sends it to the heat          Since the core system was designed to be used at
                exchanger via a 4 cm diameter low pressure wash-            sea, the barrels were screwed together for greater
                down hose.   The salt water collects its heat from          bending strength.     Due to the relatively stable
                the heat exchanger and returns to the melter                conditions when coring from an ice island, it was
                head, the descent of which is controlled by a               decided that this lateral strength was not
                small winch in the coring hut.    A descent rate of         required.   Several systems of connecting the bar-
                25 cm every 10 minutes will produce a hole no               rels were explored and a system of movable coupl-
                less than 102 cm diameter.     The boilers are each         ings attached by set screws was used.        Whe n t he
                capable of   producing 249 KW (1.2 millon BTU/hr)           barrel coupling arrived at the disassembly point
                of heat.                                                    just above the hydro-hole, the lower barrels were
                                                                            clamped and lowered to a support rail.        The set
                                       CORER                                screws were then loosened and the whole sleeve
                                                                            was allowed to slide past the pipe joint. A core
                A modified Benthos piston     coring system is now          cap was then slid under the end of the upper bar-
                being used on the island      (Fig. 8).    The f irst       rel and secured to the pipe without the loss of
                attempts at  coring employed a Benthos 2171 gravity         any sediment.    The single barrel was then placed
                corer with   a 1.5 meter core barrel.      The first        on its side and the liner removed for cataloguing
                piston core attempted was with a 6 meter Benthos            and packing.
                2450 system  with a Benthos 2171 gravity corer as
                the trip weight.      There are some significant
                differences between piston coring from a ship and
                coring from an ice island.     The first is on most

                                                                      557

                                    CONCLUSION

                Due to the unique problems involved with coring in
                the Arctic, many modifications have been made to

                the standard shipborne coring system to improve
                its safety and performance.     This system can now
                be operated by two persons and up to three cores a
                day are possible.      Besides piston coring, the
                winch system is capable of      handling heat flow
                equipment, sediment grab         samplers, camera
                equipment, and gravity corers.         Future plans
                include side scan sonar and sediment drilling.

                                               1100                 1000                  900
                              820)                                                                        -820
                                    C5

                                                                                 1985

                                                                               1986

                                                          1987
                                                                       10,
                             800-                                                                           800
                                                                        .0                   AXEL
                                                                                          HEIBERG
                                                                                            ISLAND

                                       5/06/88

                                                                                 1010
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                                                                        1)>
                                          PRINCE
                                   '00   GUSTAF
                                          ADOLF
                                            SEA                         -1 . ......

                                                               .1X

                             780.-.
                                                                                                           -780
                                                                            'Z
                                                                            63

                                 1100                                 00 0                                900

                                                        Fig. #1     Ice Island Track
                                                                    From 1985 - 1988

                                                                       558

                                                                                   PLAN VIEW

                                                                                                                                                                                              HEEL BLOC
                                                                                                                                                                                                               K                                         HYDRO-HOLE

                                                                                                                                                                                                                                                            STON CORER

                                                                                   L
                                                                                                 2@ GENERALPURPOSE                                                     LCORINGHUT                                                                 '---GANTRY
                                                                                                         HYDRAULIC         WINCH

                                                                                   ELEVATION
                                                                                                                                                                                                                                                        GANTRY

                                                                                                       .GENERAL PURPOSE                                                                                                                                                       CORING HUT
                                                                                                              HYDRAULIC WINCH

                                                                                                                                                                                              HEEL                                                    'PIMOORER

                                                                                                                                                                                              DYNAMOMETER

                                                                                                                                .......... .

                                                                                                                                                                                                                          ....... .

                                                                                                                                                            ........... ",
                                                                                                                                                                                                                                      TO-H

                                                                                                                                                               Fig. #2                            Coring                Facility

                                                                                                                                                                                                                                                                                                                                            'Yo, 001-50@

                                                                                                                                                                                                                                                                                                                                            t M

                                                                                                                                                                                                                                                                                                                                            1
                                                                                                                                                                                                                                                                                                                                            ,A
                                                                                                                                                                                                                                                                                                                                            1A
                                                                                                                                                                                                                                                                                                                                            A
                                                                                                                                                                                                                                                                                                                                            il"MA I

                                                                                   Fig. #3                            Gantry

                                                                                                                                                                                                                                                          Fig.             #4                 Placing Gantry

                                                                                                                                                                                                       559

                                                                                                                                                                                                            MEN

                                          Ll
                                                        Fig. #5             coring         Winch
                                                                                                                                                                      Fig. #6               Melter System

                                                                                                                                                                                                                      CABLE
                                                                                                                                                                                                                      CLAMP
                                                                                                                                                                         CABLE

                                                          100 gal.
                                                        EXPANSION                                                                                                                                                     ACOUSTIC
                                                            TANK                                                                                                                                                      RELEASE

                                                                                            HEAT
                                                                                         EXCHANGER
                                                                                                      '0

                                                        @INL@          r IN@                     INLU

                                                 1.2 M.B.T.V.    1.2 M.B.T.V.
                                                  BOILER          BOILER

                                                                                    5 H.P.
                                                                                    CIRC.
                                                                                    PUMP                                                                                                                                PINGER

                                                                              r  - - - - - - - - - - - -
                                                                                                                                                               CORE HEAD
                                                                          T'
                                                                     QuTt
                                                                       BLE
                                                                                      -50%GLYOOL/
                                                                                     1----SALTWATER

                                                                                                                                                                                                                         CORE
                                                 Fi   9 ,    '77       Schemati        -c. of    Melter                                                                                                                 BARREL
                                                                                             Now

                                                                       System
                                                                                                                                                               Fig. #8               Piston Coring System
                                                                                            HEAT
                                                                             L EXCHALNGER
                                                                                    _[      __        _0
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                                                          INL-   @r IN.                         _,N_

                                                                                                                                    560

                                                  OPERATIONAL ICEBERG FORECASTING CONCERNS

                                                              Walter E. Hanson

                                                          INTERNATIONAL ICE PATROL
                                                     Avery Point, Groton, CT 06340-6096

                                     ABSTRACT                             As evidenced by the many years of safe passage by
                                                                          trans-Atlantic shipping, the IIP seems to have
              The International lee Patrol uses parametric                some skill in determining the extent of the ice
              deterioration models to forecast iceberg melt               danger.    To quantify this skill has been hard
              rates in the vicinity of the Grand Banks of                 because of the need for accurate data to represent
              Newfoundland.      These    predictions,      sometimes     the initial iceberg, and interim iceberg and
              extending as long as two weeks, are used     to aid in      environmental conditions.     Between 1983 and 1985,
              resighting   or deleting      icebergs.    The    daily     the IIP studied the drift and deterioration of
              forecasts ' are used along with reconnaissance              four icebergs. Although no firm conclusions could
              efforts to establish the limit of the ice danger            be drawn from such a small data set, which
              to trans-Atlantic shipping.       in June 1987, the         represented an average drift of 4.5 days, the
              Patrol conducted a week-long study of iceberg               prediction models did a fair job hindcasting the
              deterioration in the Labrador Current on the                drift and deterioration of the icebergs when
              northeast Newfoundland Shelf (50-45N, 53-30W).         A    actual observations were used as inputs (3).           A
              cluster of six medium-sized icebergs was studied.           similar study was performed, using U. S. Coast
              Iceberg histories were compared to operational              Guard    iceberg    data,    for    the     Atmospheric
              melt predictions.     Environmental data from the           Environment Service of Canada (4).          Again the
              U.S. Navy's Fleet Numerical oceanography Center,            results were mixed.     Thus in June 1987, the IIP
              the    Canadian      Forces     Meteorological      and     conducted another cruise to collect similar data
              oceanographic Center and on scene observations              for a longer period on a cluster of icebergs.
              were compared and used to hindcast iceberg melt.
              The findings are used in a discussion of the                The objectives of this study were to compare
              Patrol's system input errors and efforts the                iceberg deterioration predictions derived from
              Patrol is pursuing to reduce them.                          inputs collected in situ to inputs available from
                                                                          operational data centers.       These latter inputs
                                                                          were divided between global and regional scale
                                                                          products.
                                 1. INTRODUCTION
                                                                                              2. BACKGROUND
              Since 1971, the International Ice Patrol (IIP) has
              used computer-based drift prediction models to              The iceberg deterioration model used by the IIP
              assist in evaluating the extent of the iceberg              provides the watch officer with an estimate of the
              danger in the vicinity of the Grand Banks of                "melt" rate of each iceberg entered in the drift
              Newfoundland   to    North Atlantic     shipping.      A    model.   The computer-based application (2), vihieh
              dynamic model began operational use in 1979 (1).            computes the melt rate, is derived from the Coast
              This model,     along with a parametric iceberg             Guard Research and Development Center Report No.
              deterioration model which began operational use in          CG-D-62-80, "Theoretical Estimate of The Various
              1983 (2), has grown in importance as limited Coast          Mechanisms Involved In Iceberg Deterioration In
              Guard resources restrict iceberg reconnaissance to          The Open Ocean Enviroment" (5).        The model sums
              an every other week schedule. During the peak of            the effects of:
              the iceberg season, April through June, the limits
              of the iceberg danger expand rapidly, requiring             .  solar radiation;
              reconnaissance    missions     to    concentrate     on     .  buoyant heat convection;
              patrolling the limits.        The majority of the           .  heat convection caused by iceberg movement
              iceberg    population   is  reconnoitered    as    time        relative to the water mass (forced beat
              permits.   often icebergs go one to two weeks                  convection); and
              before   being   resighted.     Resighting     icebergs     o  waterline wave erosion, followed by calving of
              depends   heavily    on  these models       effectively        the resultant ice overhang.
              predicting drift and deterioration rates.         These
              predictions are also routinely used to set the              Based on the 1980 report, warm air heat convection
              limit of all known ice twice daily, as reported in          is considered insignificant and not calculated.
              the international lee Patrol bulletins.                     The 1480 report also identified other iceberg

                                                                     561 United States Government work not protected by copyright

                  deterioration processes; however, they were only                the drift and deterioration of six icebergs which
                  partially addressed and difficult to quantify.                  were within a circle of approximately 55km radius
                  Consequently those processes are not modelled.                  made both compilation of environmental factors
                                                                                  affecting each iceberg and verification of iceberg
                  The model calculates melt in terms of length                    identity late in the experiment difficult.            The
                  versus mass.    This measure of melt accommodates               distance TAMAROA was        from each iceberg was
                  IIP's operational constraints, in which nearly all              paramount in determining the applicability of
                  iceberg dimensions are only reported qualitatively              environmental observations.       The average distance
                  by general size categories.       These categories are          wave data was collected from each iceberg was
                  based primarily on the maximum observed length of               48km; wind and weather data,            61km;   and sea
                  the iceberg.                                                    temperature data,      7km.    These distances were
                                                                                  computed form the interpolated positions of each
                             3. 1987 DATA COLLECTION EFFORT                       iceberg for OOOOZ and 1200i as derived from a
                                                                                  cubic spline.
                  This study collected data on six medium         to small
                  icebergs for a period ranging from 2.1 to 6.3                   The spatial separation of the wind and wave
                  days.   The icebergs were studied as they drifted               observations is much smaller than the 250km data
                  south with the Labrador Current on the Northeast                grid-spacing used by the U.             S.  Navy Fleet
                  Newfoundland    Shelf     (centered   around     position       Numerical oceanography Center to provide input
                  50-45*N,   53-30*W).      The   study    was    conducted       data  for    the    IIP's    drift   and    deterioration
                  between 15 and 21 June using the       USCGC TAMAROA, a         models.  Because the study area was at least 1051cm
                  68m (205 f t) U. S. Coast Guard         law enforcement         offshore, the wind and wave field were assumed to
                  cutter.                                                         be spatially uniform over the study area.

                  Iceberg   areal    dimensions     were    taken    during       in mapping the sea surface temperature,               the
                  daylight  using a camera and reticulated laser                  icebergs were in a tongue-like feature of cold
                  rangefinder.      Iceberg    shape    and    size    were       water    which    protruded       southeastward.      The
                  calculated    from     photographic     images     scaled       southeastward protrusion of the tongue measured
                  according    to   rangef inder measurements.         This       about l8km across.     This complicated observations
                  required a 360 degree look at each iceberg;                     since the sea surface temperature field could not
                  measuring/photographing       all    prominent     faces.       be assumed uniform.          As   a   compromise,     only
                  Measurements were accurate to +-8% of the observed              observations within 9km of an iceberg's position
                  dimensions.   No underwater iceberg dimensions were             were accepted.     Because of this restriction and
                  measured.                                                       having only one observation platform, the data
                                                                                  sets for some icebergs were incomplete. The OOOOZ
                  The rangefinder-derived distances were used with                temperature      values       necessary     to       model
                  visual bearing to fix the icebergs' positions                   deterioration    were    linearly    interpolated     from
                  during daylight.     At night, radar bearings/ranges            these data sets.
                  were used to fix their positions.         The ship used
                  LORAN-C    and    SATNAV    to    fix    its    position.                         4. ICEBERGS STUDIED
                  Positional accuracy for iceberg positions was
                  estimated (by summing system errors) to be                      Six non-tabular icebergs were studied.         Five were
                  750m.                                                           classified medium in size; one was small 0620).
                                                                                  The majority of the icebergs did not deteriorate
                  Hourly environmental observations included:            air      enough to change size.       The numbers ref er to the
                  and sea surface temperature, cloud cover, and wind              sequential numbering system that IIP uses to track
                  (at 22.3m).    Sea surface temperature was taken by             individual icebergs during the course of the ice
                  bucket thermometer (error was + O.I*C); wind was                season.    These are the same numbers used in
                  measured by the ship's anemometer.         Wave height,         archiving IIP iceberg data at the World Data
                  period and direction were visually estimated every              Center for Glaciology, Boulder, Colorado.
                  six   hours.      Visual    wave    observations     were
                  estimated to have an error of + 0.5m for wave                   Although the icebergs did not change size during
                  height; and + 2 seconds for period.                Surface      the course of the study, all were in a rapid stage
                  currents were inferred from the drift of two                    of   deterioration.      Because     of  the     recurring
                  sate 11 ite-tracked drifters, which had window-shade            presence of growlers and bergy bits in the
                  (2m X 10M) drogues.       Both drifters were deployed           vicinity of all icebergs, except #620 and #744,
                  near the center of the cluster.           Both drifters         calving was assumed a major factor in the clusters
                  were deployed at the same time; one drogued near                deterioration.    The study could not document all
                  the surface (center of the drogue 8m deep), while               calving for any one iceberg since no iceberg was
                  the other was drogued at 58m, at the core of the                observed around-the-clock.        However, two events
                  Labrador Current.     Temperature vs. depth profiles            were documented:      iceberg #784 on 19 June; and
                  were taken in the vicinity of each berg and                     1#747 on 21 June.        Because of the warm water
                  transects. were made at the beginning and end of                (greater than 3*C), the brash was expected to
                  the study to determine iceberg drift in relation                fully melt between observations. Bergy bits and
                  to the Labrador Current. The measurements were                  growlers    which    did    not   fully melt between
                  made to a depth of about 300m using T-4 eXpendable              observations were tracked (in one case up to 18
                  BathyThermographs (XBT).                                        hours), to keep     the calving statistics for the
                                                                                  cluster from being inflated.
                  Having only one observation platform to monitor

                                                                              562

              Only   icebergs    #785 and #787       appeared stable        below 40m depth were calculated and included in
              throughout the study period.         Stability in this        the    buoyant     and    forced      heat    convection
              context meant that the icebergs length and height             contributions. For all other icebergs,, convection
              constantly    decreased.     Most   of    the   icebergs      contributions below 40m   depth were ignored.
              changed shape during the study,     many probably from
              rolling.    iceberg #784 rolled     while TAMAROA was         The rest of this paper     evaluates modelled iceberg
              close aboard on 19 June.          In this case, the           deterioration      by      examining       environmental
              rolling caused height to double although length               parameters.      The     environmental       assumptions
              increased insignificantly (5%).                               regarding each melt process are reviewed.          using
                                                                            White's research (5), various observed values are
                                5. THE WATER COLUMN                         evaluated as melt parameters.        Using Anderson's
                                                                            operational computer model (2), melt estimates are
              The cluster of icebergs was in a         tongue of the        calculated from operational data center inputs.
              Labrador Current as evidenced from both sea                   The implications of error estimates for various
              surface temperatures in the area and the XBT                  model inputs on IIP operations are then discussed.
              profiles. The tongue of Labrador water had a cold
              (-l*C) core at 60m, below a shallow thermocline at                            7. WARM AIR CONVECTION
              40m.   Surface temperatures ranged between 3.4* and
              7.6*C.   Temperatures of -I*C or colder, that would           Melt from warm air convection is ignored in the
              preclude melt (5), existed primarily from 40m to              model.   For March through mid-May, no melt is
              between 90m in the eastern portion of the study               estimated for air convection.        For July through
              area, to 160m in the western portion. XBT casts               September the average melt          is   estimated     at
              taken in the vicinity (within 28km) and within 6              8cm/day, assuming an average daily air temperature
              hours    of   the    OOOOZ    interpolated     icebergs'      of 10*C and average wind of 37km/hr.
              positions were used to estimate the average heat
              available    in the water column to melt the                  The daily average air temperature warmed during
              iceberg.   The water temperature, relative to -I*C,           the study period from 6*C for 15 June to 8*C for
              was averaged in 10m increments over the estimated             21 June.    The average wind speed for the study
              draft of the iceberg. Iceberg draft was estimated             period was 33km/hr. Warm air heat convection
              as 3.95 times the average sail height observed                was estimated to be approximately 4cm/day.
              during the study (6).
                                                                            Climatological average air temperatures for the
              When there was no XBT cast near a particular                  lip region could be used to make monthly melt
              iceberg within six hours of OOOOZ, the temperature            estimates.     Likewise,    daily   global-scale     air
              information      was     calculated     by      linearly      temperature   values could be requested from an
              interpolating in time.                                        operational   data center; however, the IIP level
                                                                            of    effort   for   this    major    revision     seems
              From analyzing temperature profiles        taken about        impractical for operational forecasting purposes.
              four days apart, this tongue of the Labrador
              Current had advected south 74km. The advection of                               8. SOLAR RADIATION
              the cold core at 60m agrees well with the
              deep-drogued    drifter.    Its   drift    indicated     a    The modelled melt due to solar radiation is fixed
              predominantly southerly flow (186*T at 21cm/s for             at 2cm/day, which represents the minimum melt rate
              4 days (from 15 June/OOOOZ through 19 June/OOOOZ),            for the period March through August (2).             The
              then an easterly flow (112*T at 12cm/sec) for the             model assumes cloudy conditions.
              last 1.5 days of drift. The westward displacement
              of the thermal field above the thermocline agreed             The daylight (080OZ to 240OZ) cloud cover/obscured
              well with the shallow-drogued drifter.          From 15       skies averaged 100% every day of the study except
              June/OOOOZ to 17 June/160OZ the drift was 193*T at            for the afternoon of 17 June and morning of 19
              27cm/s.   From 17 June/160OZ until recovered on 20            June.  For those half day periods the skies were
              June/1243Z,    the    drifter    showed    a    constant      partly (averaged 50%) cloudy.         Assuming a 35%
              deceleration, averaging 206*T at 9cm/s.          All of       albedo for an iceberg, the average melt rate for
              the drifters recorded sea temperature at 1m depth             the June study period was 4cm/day (5).
              between 3* and 5*C, which agreed well with the
              bucket thermometer measurements.                              The model could be adapted to the monthly melt
                                                                            estimates derived by White; however the benefit
                   6. MODEL EVALUATION BASED     ON MELT FACTORS            would    be   minimal.      Likewise,      global-scale
                                                                            radiation estimations could be requested from
              The deterioration processes were evaluated based              operational data centers (7); however the level of
              on computations for the four medium, non-tabular              effort to identify those periods of clear skies
              icebergs which had estimated drafts from 98 to                would only provide an additional melt of 2cm/day.
              146m.   These icebergs were #747, #784, #785, and
              #787.  This cluster was studied for an average of             The IIP level of effort to make this major
              5 days.                                                       revision, and the data center's level of effort to
                                                                            extract    a  parameter,    which    is   an     interim
              Based on in situ temperature, all of the icebergs,            computation    to     predict    other      atmospheric
              except #784 and #785, had insignificant melt from             conditions,   seems   impractical     for   operational
              convective   processes    below    40m    depth.     For      forecasting purposes.
              icebergs #784 and #785, the convective processes

                                                                       563

                                    9. WATER TEMPERATURE                           product to potentially reduce melt rates appears
                  The model uses sea surface temperature to estimate               inadequate for operational forecasting purposes.
                  both buoyant and forced convection contributions                                  10. RELATIVE VELOCITY
                  to iceberg melt.       The melts due to buoyant and
                  forced convection were computed:        as a function of         Forced convection is also a function of relative
                  sea surface temperature (To); and as a function                  velocity between the iceberg and the surrounding
                  of the temperature (fTO) of the water column                     water column. The model equates relative velocity
                  integrated over the estimated draft of the iceberg.              to the difference between iceberg drift and the
                                                                                   IIP historical current in the iceberg's vicinity.
                              a. BUOYANT VERTICAL CONVECTION                       The wind-induced component to the sea current is
                                                                                   ignored.
                  Buoyant convection is considered solely          dependent
                  upon the relative temperature between a near                     Melt rates for forced convection using relative
                  vertical wall of ice and the water column.              The      velocities       derived   from      different     current
                  cluster's average daily melt due to buoyant                      parameters were compared.          The shallow-drogued
                  convection using f To       was estimated at        2cm/day      drifter was assumed to represent the velocity of
                  with    average    values    for   individual      icebergs      the water mass between the surface and the 40m
                  ranging from 1cm/day        0787) to 3cm/day (#785).             thermocline,     that portion of the        total water
                  The melt rate as a function of To                  averaged      column     which    contributed     most    to     iceberg
                  7cm/day greater; with daily differences ranging                  deterioration. The relative velocity        between each
                  from +3cm/day (9787/21      June) to +11em/day     (#747/20      iceberg and the following were calculated as
                  June).     These differences are associated with                 inputs to the -model:      shallow- and deep- drogued
                  surface temperatures which are approximately I.S*C               drifters,    and   the    lip's     ..master"  historical
                  warmer than the averaged temperature for the first               current field velocity, which for the entire study
                  10m of the water column.                                         area is 160*T at 23cm/s. The deep-drogued drifter
                                                                                   represents real-time current data which when
                                 b. FORCED HEAT CONVECTION                         available is used to "modify" the historical
                                                                                   current.     The "modified" current is forced by a
                  Forced convection is primarily dependent upon the                two dimensional spline to            fit the observed
                  relative temperature between ice and the water                   current.     Sea surface temperature was used to
                  flowing past the iceberg.         The cluster's average          compute the relative temperature term.
                  daily melt due to forced convection using fTo
                  was approximately 15cm/day with average values for               The average daily melt due to forced convection,
                  individual icebergs ranging from 12cm/day 0787)                  using     iceberg       drift      relative     to     the
                  to 21cm/day (#785).       The melt rate as a function            shallow-drogued drifter, was estimated at 59cm/day
                  of   To   averaged 47cm/day greater;          with daily         with    average   values     for    individual    icebergs
                  differences ranging from +17cm/day (#784/20 June)                ranging from 55cm/day (#785) to 62cm/day (#747).
                  to +69cm/day (both #747 and#784 on 18 June).                     The melt rate as a function of iceberg drift
                  These differences are associated with surface                    relative to the "modified" historical current
                  temperatures which are about 0.9*C warmer than the               ranged from 25cm/day slower (#747/19 June) to
                  averaged temperature for the first 10m of the                    38cm/day     faster   0784/20      June).      Using   the
                  water column.                                                    "master" historical current, the melt rate ranged
                                                                                   from 53cm/day slower (#747/19 June) to 63cm/day
                             c.   COMBINED EFFECT IN USING SEA                     faster (#784/20 June).       These differences in melt
                                     SURFACE TEMPERATURES                          equated     to   velocity differences       between the
                                                                                   shallow-drogued       drifter    and     the   "modified"
                  By using sea surface values to compute the                       current, and between the shallow-drogued drifter
                  relative temperature tent , the waterline loss                   and   the    "master"   current    of     +/-9cm/see   and
                  could be over estimated by 20 to 80cm/day.             This      +/-16em/sec respectively.
                  error    represents      summer    conditions      (surface
                  warming).     Errors for the period March through                In comparing the melts due to forced convection
                  mid-May should be significantly smaller. Although                between the "master" and "modified" currents, the
                  the error associated with summer sea surface                     real-time    input     serves  to     dampen   the    daily
                  temperatures appears significant, it is an order                 differences for each iceberg by about half.            The
                  of magnitude less than the sum of all modelled                   meteorological conditions during the study also
                  deterioration processes.                                         was a limiting factor.          Rapid changes in the
                                                                                   weather prevented wind direction from remaining
                  Subsurface temperature values can be requested                   constant (within a 60* are of the compass) for
                  from    operational     data   centers;     however,     the     periods longer than 27 hours; wind shifts averaged
                  quality of the analyses are highly dependent upon                every 12 hours.       Consequently, the sum of the
                  the availability of observational data. More                     differences      for  each    iceberg     never   exceeded
                  daily     observations      occur    for    sea     surface      +/-70cm for the study period, or an averaged error
                  temperature than for temperature over depth in the               of +/-21cm/day.
                  IIP region.       Additionally, data center thermal
                  depictions often have an accuracy no better than                 Assuming     that   these    are    the     least   errors
                  the temperature differences enumerated              above.       anticipated for the IIP region, where 5- to 7-day
                  Consequently the justification for an operational                wind events occur, an)effort to control the growth
                  data center to provide an additional temperature                 of these errors may be appropriate. Wind-induced

                                                                               564

                components of the sea current could be extracted                          TABLE 1: AVG DIFFERENCE BETWEEN DATA CENTER PRODUCTS AM OBSERVATIONS
                f rom    the    dynamic      iceberg    drif t     model     and                             OBSERVED - PNOC         OBSERVED - MITOC
                substituted     for    the   existing     input.      This    is          DATE     or     SET        WAVE HT WAVE PD SET     WAVE HT
                perceived to be a moderate level of effort for the                        000OZ   ICEBERGS 00        (m)    (see)    (*C)    (m)
                IIP.                                                                   is am      2     +1. 1        -1.2   -8  (2)  +0.5    -0.9
                                                                                       16 JUN     1     +0.7         -0.9   -5  (5)  +1.0    -0.6
                                                                                       17 JUN     5     +0.3         -0.1   -5  (5)  +0.5    -0.6
                                      11 . WAVE EROSION:                               is JUN     6     +1.0         -0.9   -4       +0.2    -1.2
                            GLOBAL VS REGIONAL SCALE PRODUCTS                          19 JUN     .5    +1.5 MA      -0.9   -2       -0.1    -0.3
                                                                                       20 JUN     4     +1.8 (2)     -1.2   -4  (1)  +0.2    -0.9
                Wave erosion, which is induced by heat convection                      21 JUN     3     1+2.5 (2)    -0.6   -2       +0.7    -1.2
                from the turbulent maximum orbital velocity caused                     *Vote %Numbers In Farentheass indicate number of times a value "a
                                                                                       auto ids the following error bounds:
                by the wave field surrounding the iceberg,                    is       SET +/- 1.6-C    Wave Height +/- 1.8 m.  Wave Period +/- 4 see
                computed     by    the model.        This     convection      is     FNOC and METOC products differed primarily in
                proportional to wave height (H) times relative                       their representations of sea surface temperature.
                temperature (T), and inversely proportional to                       The      FffOC-produced         sea surface     temperatures
                wave period (P). The model assumes the effects of                    averaged 1.3*C colder than the surface-measured
                the wave field are non-directional, implying that                    values       for   the   cluster;      the     METOC-produced
                the    iceberg      is    melted     uniformly      from    all      temperatures       were         0.6*C  colder.        Averaged
                directions (5).       This assumption generates a melt               differences between observations and FNOC products
                factor which may over estimate the wave-generated                    for individual icebergs ranged from 1.9*C 0784)
                convection.      Wave erosion is the most important                  to 0.6*C 0785) colder. The differences listed in
                process in the iceberg melt model.              It is up to          Table I which are greater than the reported system
                ten times greater than melt by forced convection,                    error are due to the presence of sub-scalar
                and routinely 100 times greater than buoyant                         thermal features.       in this case, iceberg #747 and
                convection.     The applicability and accuracy of the                #784 had crossed the surface thermal front between
                environmental      parameters     used     to model       wave       the      colder    Labrador     water      and  the     warmer
                erosion thus greatly affect the daily melt rate                      Newfoundland Shelf water.
                estimated by the model.
                                                                                     Little difference existed between the observed
                The    model      computes       T   from     sea      surface       wave height and those produced by YNOC and METOC.
                temperature.      Significant wave height and a wave                 The FNOC-produced wave heights averaged 0.9m
                period, which     is that period associated with peak                higher than the observed height for the cluster;
                energy    observed      in    the    wave     spectrum,     are      the METOC-produced height was O.8m higher.                Daily
                currently used by the model                 f or H and P             differences between observed and predicted wave
                respectively.     Sea surface temperature is assumed                 heights for individual icebergs ranged: from 0.3m
                to be the best parameter from which the relative                     (all/17 June) to 1.5m (#785/20 June) for FNOC
                temperature term for wave erosion is calculated,                     products; and from 0.2m (all/19 June) to 1.2m
                and it is readily available from data centers.                       (all/18 June).       The wave period differences in
                Data center products to represent H and P are                        Table I which exceeded system error may be based
                significant,      sea,   and swell height and peak                   partly on the limitations of visual observations
                periods for the total energy spectrum, and for the                   and      the quality assurance employed by each
                sea and swell spectrums.             When the model was              observer.
                implemented in 1983, the wave parameters currently
                used were the only ones available.                                   The cluster's average daily melt due to wave
                                                                                     erosion using observed values was estimated at 379
                Table I shows the differences between observations                   cm/day with average values for individual icebergs
                and those values produced by operational data                        ranging from 330 cm/day 0785) to 408                    cm/day
                centers.    The global scale (250km grid-spacing)                    (#747).      The cluster's average daily melt using
                parameters were produced by U. S. Fleet Numerical                    FNOC (global scale) products averaged 152               cm/day
                oceanography Center (FNOC) using its computerized                    faster.      Individual iceberg's average melt          ranged
                Expanded Ocean Thermal Structure (EOTS) analysis                     from 144 cm/day (#784) to 200 cm/day                    (#785)
                and Global Spectral Ocean Wave Model (GSOWK) (7).                    faster.      The cluster's average daily melt using
                The regional scale (estimated from 50 to 100 km                      METOC    (regional scale)        products averaged 195
                grid-spacing) parameters were produced by the                        cm/day faster.       Individual iceberg's average melt
                Canadian Forces Meteorological and Oceanographic                     ranged form 149 cm/day (#785) to 218 cm/day (#787)
                Center    (METOC)     Halifax,     Nova    Scotia.      METOC        faster.
                depends on human interpretation of surface thermal
                observations and uses a parametric ocean-wave                        The higher melt estimated using both FNOC and
                model (8) which is qualitatively blended with ship                   METOC parameters was a function of their 'higher
                observations.     All values are for OOOOZ, except                   wave height predictions.         The melt estimate using
                for the METOC H parameter, which was analyzed at                     FNOC products appeared better than METOC because
                180OZ.     The . METOC      180OZ    sea   state     analysis        the colder FNOC temperatures helped offset the
                normally contains more ship observations than the                    error in predicting wave height.                The model's
                METOC OOOOZ analysis; improving the quality of the                   sensitivity to wave height makes that input
                180OZ analysis.       For all data center inputs, the                parameter highly important to IIP.              Thus it is
                values, which were compared to observations, were                    highly prudent for IIP to investigate new wave
                interpolated to each iceberg's OOOOZ position.                       data inputs for the model, and thoroughly evaluate
                                                                                     these inputs before substituting them for the FNOC
                                                                                     significant wave height and peak period inputs.

                                                                               565

                                                    12. SUMMARY                                          The       iceberg       sizing        methodology           and     study
                                                                                                         time-constraints            made       comparisons           of     model
                       Table 2 summarizes the deterioration processes                                    estimations         to observed            lengths       inconclusive.
                       examined by this paper.                   For this ensemble of                    Either a better methodology must be used in future
                       medium-sized,         non-tabular shaped,               icebergs,        a        studies or studies must be extended over much
                       daily melt rate was estimated by the model to be                                  longer periods (14-21 days). Given the potential
                       4.0 m/day.       Using FNOC products, the melt rate was                           for         errors        associated            with        operational
                       over estimated by 1.7 m/day. METOC products over                                  reconnaissance,             which        depends         heavily         on
                       estimated the melt by 2.2 m/day.                           These melt             qualitative descriptions, and the                       inability to
                       estimates are of the same magnitude as the iceberg                                address       all     deterioration processes,                 the IIP
                       sizing error.          Because of the short duration of                           policy to require icebergs to deteriorate 175% of
                       the study, no firm conclusions could be drawn from                                their original estimated length is prudent.
                       the observed iceberg measurements.                      Icebergs #785
                       and #787, which seem to have remained stable                                                                 13. REFERENCES
                       throughout the study period, appeared to have
                       melted faster than the prediction based on the                                    1. MOUNTAIN, D. G., 1980. On Predicting Iceberg
                       optimum-observed                environmental              parameters;                      Drift. cold Regions Science and Technology,
                       however, both predictions based on data center                                              Vol 1 (3/4), p ?73-282.
                       products were within measurement error bounds.
                                TABLE 2: AVERAGE MELT RATE FOR VARIOUS INPUTS (cm/day)                   2.    Anderson, 1., 1983.            Iceberg Deterioration
                                                                                                                   Model. Report of the International Ice
                                  OPERATIONAL MODEL                                                                Patrol in the North Atlantic Ocean, Season
                       Relative Temperature         T/D       SST         SST     FNOC        IMOC
                       Relative Velocity          Waft)      V(sfc)       V(deep) v(sfe)      V(ofe)               of 1983, (CG-168-38)9 p 67-73.
                       Wave Height                Primary    Primary      Primary FROC        METOC:
                       Wave Period                  Peak      Peak        Peak    Peak        Peak       3. Anderson, 1., 1985.               Oceanographic Conditions
                       Warm Air Convection             4         4          4        2        2                    On The Grand Banks During The 1985 IIP
                       Solar Radiation                 4         4          4        0        0                    Season. Report of the international Ice
                       Buoyant Convection              2         9          9        6        a
                       Forced Convection               15       62        6- 122    33        41                   Patrol    in the North Atlantic Ocean,
                       Wave Erosion                 379       379         379     531         574                  Season    of 1985, (CG-188-40), p 56-67.

                       TOTAL AVERAGE MELT           404       458    402 - 520    572         625
                                                                                                         4. El-Tahan, M., S. Venkatesh, and H. El-Tahan,
                       T/D       - Temperature contribution as function of depth                                   1987.     Validation and Quantitative Assesment
                       V(sfc)    - Differential velocity between iceberg and surface-drogue4
                                   drift r                                                                         Of The Deterioratoin Mechanisms of Arctic
                       V(desp)   - differential velocity between iceberg and deep-drogued                          Icebergs.      Journal of offshore mechanics and
                                   drifter                                                                         Arctic Engineering, February 1987, Vol 109,
                       Sea surface temperature appears to be a suitable                                            p 102-108.
                       parameter from which the relative temperature term
                       is calculated in the model. In this study the use                                 S. White, F. M., M. L. Spaulding, and L. Gominho,
                       of sea surface temperature to solely represent the                                          1980. Theoretical Estimates Of The Various
                       relative temperature term vice using temperature                                            Mechanisms Involved In Iceberg Deterioration
                       versus depth to represent the term for buoyant and                                          In The Open Ocean Environment. Report
                       forced convection, caused the melt rate to be over                                          CG-D-62-80, U. S. Coast Guard Research and
                       estimated by 12%.               Global-scale thermal products                               Development Center, Groton, CT 06340-6096,
                       cannot adequately represent the Labrador Current                                            126 pp.
                       as it flows below 48*N latitude. Regional scale
                       temperature          products        currently       available         can        6. Robe, R. Q., 1975. Height To Drift Ratios Of
                       improve the resolution of the temperature data.                                             Icebergs. Proceedings of the Third
                                                                                                                   international Conference on Port and Ocean
                       over simplification of methods used by IIP to                                               Engineering Under Arctic Conditions, 11-15
                       derive the relative velocity between icebergs and                                           August 1975, Vol 1, p 407-415.
                       the surrounding water contributed to                       an error of
                       up to 16% of total melt. Because the                       wind-induced           7. Numerical Environmental Products Manual, Vol
                       component of the ocean surface layer                       (between the                     II, August 1986. Prepared under authority
                       surface and 50m depth) is computed in the IIP                                               of Commander, Naval Oceanography Command,
                       iceberg drift model, this velocity component could                                          NSTL,MS 39525, 200 pp.
                       be added to the known or historical surface
                       current.       The resultant current value could then                             8. Macdonald, K. A., and S. Clodman, 1987. The
                       be used to compute relative velocity to reduce the                                          AES Parametric Ocean-Wave Forecast System.
                       magnitude of this error.                                                                    Proceedings of the International Workshop on
                                                                                                                   Wave Hindeasting Forecasting. Report 065.
                       Wave height over estimation causes daily melt to                                            Envirorunental Studies Revolving Funds,
                       be over estimated. This significant (about 38% of                                           Ottawa, pp 119-132.
                       total melt) error in determining the wave erosion
                       factor may help offset the model's inability to
                       represent other deterioration processes that the
                       model ignores.             New wave products that have
                       recently become available should improve the
                       representation of wave erosion.

                                                                                                    566

                                              AN AUTONOMOUS ATMOSPHERIC PRESSURE RECORDER
                                                                     FOR
                                                 ESTABLISHING POLAR SEA SURFACE HEIGHT

                                 GEORGE STEEVES                                      STEPHEN GRANT

                                 Head, Systems Engineering                           Regional Tidal Officer
                                 Engineering & Technical Services                    Canadian Hydrographic Service

                                                         Bedford Institute of Oceanography
                                                         Dept. of Fisheries & Oceans
                                                         Scotia-Fundy Region
                                                         P.O. Box 1006, Dartmouth, N.S.
                                                         Canada 82Y 4A2

                                        ABSTRACT

                    An        accurate      long-term        recorded
                    measurement of atmospheric pressure in
                    Arctic       regions      is    essential      for
                    correcting      absolute-pre5sure measuring
                    submerged tide gauges. A device capable
                    of     unattended    operation       will    make
                    possible an accurate measurement of polar
                    sea    surface    height.       This     data    is
                    required        for  hydrographic        surveys,
                    physical     oceanography,      and   satellite
                    image     analysis.          This    paper will
                    describe an     autonomous    low-power device
                    for the precise measurement (+/-0.7 mbar)
                    of atmospheric     pressure versus date/time
                    in Arctic conditions (-55 deg C, 120
                    km/hr wind).        Data     is stored using
                    "burned         in   silicon"        technology.
                    Measurements are made every hour on the
                    hour over a period of 12 months. Static
                    pressure is measured using a special part
                    designed to be insensitive to the affects
                    of wind.     Endurance problems associated
                    with a "one-year" instrument operating in
                    extremely harsh conditions are discussed.

                                 1. INTRODUCTION                                                FIGURE 1. SYSTEM COMPONENTS

              The tides in the      vast areas of the Canadian Arctic           achieved    in  the    past ,    using    bottom     mounted
              continue     to be    one of the principle concerns Of            submersible tide gauges that        measure the pressure
              hydrographer5 and     oceanographers.      In order to meet       changes as    the   height   of   water   over    the gauge
              the     needs      of  marine      shipping,   construction       changes   with   the    tide.     Except    for   ice   berg
              industries.     environmental      impact      studies ,  and     scouring, the gauges       are  relatively    safe beneath
              resource     development     the   Canadian    Hydrographic       the surface of the ice.      The pressure sensed on the
              Service      has   recognized   the   need  for   a planned       ocean bottom is the     sum   of   that   exerted    by the
              approach to     the tide survey of the Canadian Arctic            water mass and that exerted by the atmosphere.            The
              Archipelago.       However,    sea   surface   height   as a      pressure of the atmosphere varies by the equivalent
              function     of    time is   a difficult       parameter    to    of   approximately       12S   cm    of   water,    and    if
              measure, in the Arctic, because of         the destructive        unaccounted    for   would   result    in  a    significant
              forces of       ice and the almost total lack of                  error.        The    atmospheric     component must be
              facilities (power,      communications, transportation,           subtracted from the total pressure to arrive at the
              people).        A limited amount of success has been              sea water pressure and thus the sea surface height.

                                                         CH25 85-8/68/0000. 567  $1 @1988 IEEE

                    In near    shore areas not infested with sea ice, the                  The third circuit board, designated DS-64,              is a C-
                    measurement of sea surface             height is    a relatively       44 bus   compatibledata store composed of 64k bytes
                    5 i pip I e procedure.                 Adifferential   pressure        of  CMOs       EPROM.    The    AIR    digital    barometer is
                    transducer is installed on             the sea floor with one          interfaced     directly    to     the  CPU     board using the
                    Port exposed        to the sea water     and the other port            parallel       port  and   connected    to     the   atmosphere
                    vented to the atmosphere.              There  have   been many         through a      wind dampened    pressure port.       Energy is
                    attempts to         construct this kind of installation in             supplied by a lithium battery pack.
                    the Arctic.         The failure rate    is high     because in         The instrument is contained in a section of              8 inch
                    most cases          ice movement       has destroyed the vent to       diameter aluminum       schedule 40     pipe, with 1/2 inch
                    the atmosphere;        even armored    vent  tubes in5talled           thick aluminum end caps and internal bulkhead.                The
                    in   protected      trenches           have not survived.    The       battery        and     instrument       compartments      . are
                    obvious alternative is                 to measure  the total and       individually sealed.
                    atmospheric pressures independently          versus time     and
                    subtract them later to determine the pressure
                    variations due         solely to       the vertical water
                    movements.          The actual         wa t er level changes are                        3. SENSOR & CLOCK
                    calculated from the pressures using the specific
                    gravity of sea water.                                                  A search was     initiated    for a    pressure sensor with
                    To address this problem,               the Canadian Hydrographic       lowI   power,  consumption      and    a    12 month accuracy
                    Service commissioned        the design     of a device which           equivalent to        +/- I cm. of      water while operating
                    would   record      atmospheric        pressure versus     time.       under Arctic     conditions.       An almost ideal device,
                    The accuracy        of the pressure measurement and        t he t      called         "INTELLISOR",       is       manufactured      by
                    of time             to be at least as  good as      that of the        Atmospheric      Instrumention      Research      Inc.      This
                    submerged tide      gauge.             The pressure sensors in the     pressure transducer combines           a    stable capacitance
                    tide gauges now in use have an accuracy             of +/- 0.3         type    sensor       with  microprocessor      control.       it
                    mbar,   but         the uncertainty    in  the      value of the       Measures pressure 10 times per second             and makes it
                    specific gravity of the sea water above it, make :                     available in     digital format to a computing device.
                                                                                   it      Relevant specifications include:
                    likely that the        calculated sea water height has an
                    accuracy of +/-        I cm.           The system   required an        Pressure accuracy (12 mos.)                       +/-0.7 mbar
                    endurance           of one  year       and survivability   under       Pressure resolution                               0.01 mbar
                    Arctic    weather      conditions.         The      design   and       Pressure range                              800 to 1200 mbar
                    development         was initiated      in 1987,     with a test        Temperature range                           -5S to +85 deg C
                    deployment later       that year.                                      Power consumption                                 99 mW (oper)
                                                                                                                                          150 uW (stdby)

                                                                                           Accurate time keeping for          a 12     month period    is a
                                                                                           problem, when        the temperature range is expected to
                                                                                           be 60 deg 0.         Power restrictions rule out oven
                                                           h                               controlled oscillators.          A temperature compensated
                                                                                           crystal oscillator (TXCO) provides an adequately
                                                                                           accurate time        base. Accounting for temperature and
                                                                            A              ageing stability, the oscillator                  chosen would
                                                                                                          worst case    error in       time of +95 to -65
                                                                                           produce a
                                                                                           seconds per year.

                                        P                  "le
                                                                                                          4. OPERATIONAL SEQUENCE

                                                                           m               The sequence of      states      the   system     moves through
                                                                                           af ter   start   up    reveals     the design     strategy    and
                                                                        Of
                                                                                           describes It's operational details.
                                                           xTn-
                                        FIGURE 2.  VIEW    of ELECTRONICS
                                                                                           1. Empty EPROMs are installed on the data store
                                        2. SYSTEM OVERVIEW                                 board.         The   (year,month,day.hour,minute) initial
                                                                                           date/time is set into the micro thumb wheel array.
                    The System is based        on the      C-44 microcomputer bus          The    system    is  powered     up manually on the minute
                    architecture        for  battery       powered Systems.      The       selected.
                    system is managed by         an        Onset CMOs   single board       2.   The       power sequencing        circuit     delays     the
                    computer            (CPU-8085A).       Asecond custom designed         application of power to the digital barometer until
                    circuit             board,   contains        the     real-time         the   CPU      conditions   the    control     lines.        This
                    calender/clock circuit,                an array of 10 micro thumb      prevents the barometer's microcomputer fr           .om locking
                    wheel switches (to initialize the date/time), and a
                    circuit             to synchronize     the application of power.       up.

                                                                                       568

                                                                                             PRESSURE
                                                                                             PORT

                                                                            AIR              POWE
                          DATE/TIME SET                                  DIGITAL         S   QUENCER
                                                                      BAROMETER
                          (MICRO-774UMBMIEEL ARRAY)      Ho I M, MO]   I k A   SHU      TEMPERATURE
                          1@ 1y01M11M0jDjjD6jH1                         00,19  DOWN     COMPENSATED
                                                                                           CRYSTALL
                                                            2                            OSCILLATOR

                           CMOS EPROM                  CMOS SINGLE BOARD          WAKE REAL TIME
                           DATA STORE                         COMPUTER              UP    CALIENDER
                               DS-64                          CPU-8085A                      CLOCK

                          F                                  C-44 BUS

                                                            FIGURE 3. SYSTEM STRUCTURE

                3. The CPU then reads the micro thumb wheel array,             daily record. The high voltage supply (used in
                                                                               the programming made) on the data store board is
                sets the initial date/time into the real time                  turned an and the data written into the non-
                clock chip and sets the alarm for the next integral            volatile EPROMs.    This event happens each midnight
                hour.                                                          up to and including day 368, when the 64k byte data
                4. The power down command is then issued to the                store is considered full.
                barometer and the CPU places the system in low-                The microcomputer code executed by the CPU has two
                power HYBERNATE mode. This mode not only holds up              special modes to facilitate system testing and
                instruction execution, but also reduces the system             verification.    FAST mode speeds up the real time
                supply voltage.       However, a TXCD (temperature             clock, such that I hour of real time is replaced by
                compensated crystal oscillator) time base continues            10 sec. of computer time. FAST/N0 HYBERNATE mode
                to drive the real time clock chip.                             speeds up the clock and keeps the system awake.

                5. On the hour, the clock alarm sends a WAKE-UP
                signal to the CPU.          This signal initiates the                         S. ENERGY SOURCE
                sequence which brings the supply voltage up to it's
                operating value.     The CPU then begins execution of          The energy    source for an autonomous instrument
                the interrupt service routine.                                 operating in  a remote area under harsh conditions
                                                                               is a system   component of crucial importance. For
                6. The barometer is turned on     and commanded to make        unattended     year     long    Arctic , deployments,
                10 Measurements and average them. The CPU then                 reliability   and low temperature operation are of
                initiates a sequence of hand-shaking signals to                particular concern. Operating temperatures as low
                transfer the measurement data bytes to CMOS memory.            as -SS deg C preclude the use of almost all common
                                                                               battery Lechnologies; this factor alone would point
                7. The system places itself in HYBERNATE mode once             to one of the lithium types. Design considerations
                more and awaits the next hourly alarm.         The day's       that must be accounted for include:
                data is accumulated and stored in CMOS RAM.
                                                                               1. Load Voltage versus Capacity (ampere hours)
                8. When the alarm coincides with midnight, the 24              2. Capacity (ampere hours) versus Discharge Current
                hourly measurements of atmospheric pressure are                3. Capacity (ampere  hours) versus Temperature
                                                                                             POWEI
                                                                                        @SEQ@UEN
                                                                                        T MP;=PjAj

                concatenated with the date to form a 1?8 byte                  4. Mid-point Voltage  versus Temperature

                                                                          569

                                                                                                                                                                                           Al .. 11 . Al 2 .1
                                                                                                                                                                                      J1 8     1211411011812M01POM2124 14 15 J 7 19 J 2 18 J 11113115 17 19 2f 23 2                    .0

                                                                                                                                   I T
                                                                                          I   I     I F                            IIT
                                                                                          .   I     ..   I                         III   T
                                                   1 2 3 4 5 6 7 8                        12  1 @1                                 17 1! @1 @1@2                 31          33       3 V
                                           DN)DE                                                                                                                                                                                                                                                 2-    2-
                                                                                                                                                                                                                                                                                                 7     7
                                                              1.        12 1                                                       2     21                                                                                                     3         3              1                       V     74- w- Ixo-
                                                       &                7                                                                                                                           C    =1
                                                                                      ED                                           aG)                                                                                                                                                           1-1   .1  VW
                                                                                       ml           LID                            2                                         2        5   2        1                                                                                             1.

                                                                             IN4= DO=
                                                                                                                                   C,
                                                         -->DH>                                                                    .1
                                                                    .1      N2

                                                                                                                                   .2 21.1
                                                                                                         '4                        3 3 4              4,
                                                                                              2.    k'r2
                                                                            .2

                                                                                                    MC14MIS
                                                                        1            2                                             3
                                                                                                                                                      74 HC3D
                                                                          .IPj                                                     A--
                                                                                       7 11 1 11           1                       7
                                                                                                                                                                             Nora. m 'MINNIGM
                                                                                                                                                                 2
                                                                                                                                                               3

                                                                                              R IS I T I U I V JW I X 118 120 JH

                                                                                                                                                  FIGURE 4. SCHEMATIC

                                  The             system                   components                         which                are       significant                              cells in the double D size.                                                   To achieve the voltage
                                  consumers of electrical current are:                                                                                                                and capacity required, 4 parallel groups of 5 cells
                                                                                                                                                                                      in series were employed, each group isolated by
                                                                           HYBERNATE                                               EXECUTING                                          blocking                     diodes                   to          prevent charging.                                           This
                                                                                                                                                                                      configuration produces an open circuit voltage of
                                  CPU Board                                     I mA                                               8 I'l A                                            19.Sv, a                  mid-point voltage                                   of 15v,                      and a minimum
                                  Data Store                                 10 uA                                                 55 mA (programmingi                                capacity of 60 ampere-hours at                                                       -40           deg           C.           This
                                  Barometer                                  10 UA                                                 6 mA                                               specification is more than adequate for d location
                                  Oscillator                                    5 MA                                               5 mA                                               such as Eureka NWT, in the                                                high Arctic,                           where the
                                                                                                                                                                                      mean annual                        temperature is -18 deg C and the mean
                                  The system                    spends less than 2 sec. per                                                  hour making                              daily minima                       for the coldest month is -46 deg C.
                                  measurements and less than 0.5 sec. per day burning
                                  the data in EPROM.                                          Therefore the power consumed
                                  in execution made is insignificant compared to that
                                  consumed in the hybernate made.                                                                  The major energy                                                                      6. DATA STORAGE & RETRIEVAL
                                  usage results from maintaining an accurate time
                                  base in the presence of fluctuating temperature,                                                                                                    The digital                        barometer, produces it'5 ASCII coded
                                  and riot writing data into EPROMs, as might be                                                                                                      readings in                         the             form              xxxx.xx                      in            units of
                                  expected. Calculating for a one year deployment, a                                                                                                  millibars.                               The              daily record of 24 hourly
                                  battery pack capacity of S2.5 Ah is required; the                                                                                                   measurements of atmospheric pressure are combined
                                  momentary peak current is 74 mA.                                                                                                                    with the date and delimiting characters to produce
                                                                                                                                                                                      a 178 byte ASCII string.                                                 The "64k" (6S536) byte
                                  The switching regulators on                                                                      the microcomputer                                  capacity data store can thus record for 368 days.
                                  boards and                      more importantly the                                             TCX oscillator can                                 Since the information                                       is        stored                 "on           silicon" in
                                  be operated                           over a            wide range                               of input voltages,                                 ASCII            code,              the          EPROMs               themselves                           form       a data
                                  but they are significantly more energy efficient at                                                                                                 archive.
                                  ,the high end of the voltage range (maximum 18v).
                                                                                                                                                                                      A small read-out device has been constructed into
                                  Lithium                   batteries                         using                                oxyhalide       chemistry                          which the complete data store board may be plugged.
                                  provide the                           highest performance in low to moderate                                                                        When          initiated                    the            device              will            output                 all the
                                  discharge rate applications.                                                                     Abattery pack                   was                records to either a serial (RS232C) device or a
                                                                                                                                                                             M
                                                                                                                                                                                 1331

                                                                                                                                                                             2                                                                          ly,

                                  designed using an array of Electrachem BCX primary                                                                                                  parallel (Centronicsi' device.

                                                                                                                                                                             570

                                                                                  In August 1987, one of the two completed units was
                                                                                  deployed on the coast of Labrador for scheduled
                                                                                  recovery in August 1988.           The second unit was
                                                                                  tested on the roof of the Bedford Institute during
                                                   FUSE                           January 1988.        The resulting measurements were
                                                                                  compared     to    those    obtained using a mercury
                           +     +    +      +                                    barometer at the nearby            Shearwater Naval Air
                                                                                  Station (readings corrected Using the Smithsonian
                                                                                  Meteorological Tables, 6th edition). The agreement
                                                                                  between the readings was well within the +/-0.7
                                                                                  mbar accuracy of the digital barometer.           This test
                           +     +    +      +                                    verified the immunity of the pressure port assembly
                                                                                  to the affects of wind, ice, rain, and snow.
                                                  ELECTROCHEM
                                                  5 x 4 ARRAY
                           +     +     +     +    BCX LITHIUM
                                                  OXYHALIDE                                      8. FUTURE DEVELOPMENTS
                                                  PRIMARY CELLS                   The independent collection of atmospheric and total
                           +      +    +     +                                    sea bottom pressure is a logical first step for
                                                                                  establishing accurate long term records of sea
                                                                                  surface height in remote regions, However, there
                                                                                  are instances where the information is required
                           +      +    +     +                                    more frequently than once per year.                In these
                                                                                  cases, it would be useful to monitor, both the
                                                                                  barometer and       the tide gauge remotely.              The
                                                                                  availability of reliable and inexpensive satellite
                                                                                  up-links make this a straight forward engineering
                                                                                  task were it not for the problem of communication
                                                          0                       with the submerged tide gauge.               Just as the
                                                                                  differential pressure transducer could              not be
                              FIGURE S.      BATTERY PACK                         vented   t a  the  atmosphere, due to the destructive
                                                                                  ice surface, the tide gauge cannot be electrically
                                                                                  connected to the shore. Underwater telemetry in
                                                                                  near shore situations is plagued with problems of
                                                                                  it's own, not the least of which is the ice to
                       RS-232C                                                    water interface.     It is known that hard rock miners
                    COMPATIBLE         COMPATIB E         CMOs EPROM
                       DEVICE                              DATA STORE             use HF radio to      communicate with the surface from
                                           DEVICE                                 thousands of meters underground       using the     rock as
                                                                                  the transmission medium. If such a radio could be
                                                                                  coupled to the rock under the tide gauge, it may be
                       SERIAL               CMOs                                  possible   t 0   transmit    the   data   t o  a   receiver
                  COMMUNICATIONS       SINGLE BOARD                               ashore, thus avoiding the water-ice-air boundary
                       BOARD             COMPUTER                                 altogether.      This   topic    is  the subject,of some
                       WART              CPU-8085A                                interest   for   the    Arctic     sea    surface     height
                                                                                  application and will be pursued in the coming
                                                                T                 months.
                E                       C-44 BUS

                            FIGURE G. DATA STORE READER

                                                                                                9. ACKNOWLEDGEMENTS

                                                                                  The authors wish to thank Steven               Witiker of
                                                                                  Atmospheric     Instrumentation      Research Inc. and
                                                                                  Dr.R.Siegler of Electrochem Industrie,@ for their
                              7. TEST PROGRAMME                                   technical assistance.
                                                                                  Members of the technical staff of the Bedford
               An extensive series of        tests  were   conducted with         Institute of Oceanography      who   contributed     to the
               the system placed in FAST mode and when cooled to                  design include R.Vine, G.Awalt and G.Cooke.
               -55 deg C.       These tests verified the operational
               sequence of the system by simulating an entire year
               of    operation       n    25    hours    of    real time.
                                          rFUSE

               Measurements      were    made of electrical current
               consumption and        time    keeping     accuracy which
               confirmed        the    correctness      of    the     design
               calculations.

                                                                              571

                                 10. REFERENCES

                 Tait,B.J. et al (1986). "Canadian Arctic Tide
                 Measurement Techniques and Results", International
                 Hydrographic Review, Monaco, LXIII(2)

                 Stephenson,F.(1977):    "An   Assessment of the
                 Permanent Water Level Stations in the Canadian
                 Arctic", Lighthouse, Ed.16

                 O'Leary,T. (1986): "Report on the Stability and
                 Accuracy of Two AIR-DB Series Digital Barometers",
                 Schwien Engineering Inc., Pomona CA

                 Krehl,P.W. et al (1987). "Safety-Enhanced. High-
                 Rate, Non-Magnetic       Lithium   D-Size    Cells for
                 Oceanographic      and     Naval   Use",    Oceans     87
                 Proceedings, Volume One pp. 271-279

                                                                          572

                                                  ESTIMATED ICE-GOUGE RATES ON A MANMADE SHOAL
                                                                IN THE BEAUFORT SEA

                                                       Thomas K. Newbury and Allen J. Adams

                                                Minerals Management Service, Alaska OCS Office
                                                          Leasing and Environment Office
                                                           Anchorage, Alaska 99508-4302

                                       ABSTRACT                                gouging, has not yet been analyzed and is the
                                                                               subject of this paper.
               In 1987, slope-protection fabric was removed from
               the top of an artificial gravel island in Harrison              Past   experience with abandonment          of Alaskan
               Bay, southwestern Beaufort       Sea.     As a result,          Beaufort Sea artificial islands is          mainly with
               currents began to erode the island's top.           After       islands such as BF-37 and Duck II, which were
               it is eroded to a subsurface     shoal, ice keels will          constructed on the shoreward side of natural
               slowly gouge and disrupt the     remaining shoal. This          islands where ice-gouge rates arelow.               These
               paper analyzes the ice-gouge     process and estimates          naturally protected islands have been gouged very
               the rate of sediment disruption by gouges.            The       infrequently by ice keels during the years since
               rate is derived from existing information on                    abandonment in the early 1980's.
               gouges in the surrounding seafloor in Harrison        Bay
               and for a time when the shoal is at half of           the       Abandoned    artificial    islands    that   have been
               water depth (-7.5 m).       It is estimated that      ice       studied in the Canadian Beaufort Sea are located
               keels will typically disrupt I vertical meter of                in an extensive landfast ice zone in which there
               the whole surface of the shoal within a period of               are infrequent ice gouges.        For example, a study
               about 2 decades.                                                of seafloor gouges in 15 m of water near artifi-
                                                                               cial islands off Tuktoyaktuk concluded that there
                                  1. INTRODUCTION                              is an average of one new gouge per year per
                                                                               kilometer (gouges/year/km) of survey trackline
               Mukluk Island is an artificial island constructed               (4).     The maximum gouge rate in the Canadian
               in 1983 in 15 m of water in outer Harrison Bay,                 Beaufort Sea is about four new gouges/year/km (5).
               southwestern Beaufort Sea.       The island is made of          In contrast, an average of eight to nine new
               sandy gravel fill material from an onshore borrow               gouges/year/km was observed in Harrison Bay where
               site and contains negligible fine-grain material.               Mukluk Island is located (6).
               The material has been protected from wave erosion
               by a slope-protection system. The system includes               The purpose of this paper is to use existing
               gravel- filled bags that are made of heavy woven                information on ice-gouge rates to analyze the
               polypropylene cloth and an underlying polypropy-                process and estimate the rates of sediment disrup-
               lene mat (1).       In 1987, the owner decided to               tion on Mukluk Island's base.         The actual rates
               abandon the island and, therefore, removed the                  eventually can be determined through bathymetric
               slope-protection fabric from the top of the island              monitoring.
               to a depth of -4.6 m (1).
                                                                                          2. ICE GOUGES IN HARRISON BAY
               This unprotected island in outer Harrison Bay will
               be subject to erosion by waves to form a submerged              Harrison Bay is gouged at "high" to "very high"
               shoal in a relatively brief time period.        The time        rates between water depths of 10 and 30 m (7).
               will depend mainly on the frequency and severity                Side-scan-sonar records and bathymetric profiles
               of open-water storms.       Storms in both 1986 and             from this area show remnant traces 'of 50 to 100
               1987 that were comparable to 100-year events                    gouges per square kilometer (7, 8).         The benthic
               eroded about 20 percent of the island's top. With               survey for Mukluk Island (9) also noted the many
               the removal of the slope-protection materials in                ice gouges in the area.           Another study (10)
               1987, the complete erosion of the unprotected top               describes the seafloor seaward of the 12- to
               to -4.6 m might occur after several more open-wa-               15-meter isobath in Harrison Bay as "saturated"
               ter seasons (2, 3).       The subsequent fate of the            with ice gouges.
               island's base, which is in an area of severe ice

                                                        CH2885-8/88/0000- 573 $1 @1988 IEEE

                 The maximum incision depths of new gouges in                     Three sets of studies provide relevant data that
                 Harrison Bay are usually about 10 percent of the                 show that the variation in ice-gouge-disruptlon
                 water depth (6).      The most extreme gouges may be             rates due to sediment composition is minor.
                 from ice keels driven by forces amassed from an
                 encompassing solid icepack (7).            Some of the           One study observed the effects of         ice keels on
                 widest gouges (gouge "multiplets") are caused by                 Mukluk Island fill material (1).             Just after
                 ice-pressure-ridge keels. There are traces across                Mukluk Island was constructed in          1983, summer
                 the central Beaufort Sea shelf, including the                    drift ice caused extensive damage to      the slope-pr-
                 waters 15 m deep in Harrison Bay, of about two                   otection system.     The slope-protection polypropy-
                 wide multiplets per kilometer of survey trackline                lene fabric was ripped extensively and the gravel
                 (7). One of the gouge multiplets they observed in                fill in the bags was dispersed by wave-induced
                 outer Harrison Bay had a width of 78 m, maximum                  currents (1). This study shows that Mukluk Island
                 gouge depth of 4.0 m (excluding the adjacent                     fill material is gouged and disrupted by the
                 ridges), and a cross-sectional area of incision                  forces of isolated pieces of summer ice.
                 estimated at 234 m2.
                                                                                  A second set of studies concerns ice-push events
                 The gouges near Mukluk Island are made primarily                 near Point Barrow (13). In this area grounded ice
                 during the winter by ice-pressure-ridge keels                    ridges and floes    are frequently incorporated into
                 (11).    The pressure ridges form when the offshore              the ice canopy      during freezeup. During winter
                 pack ice drives the landfast ice toward the                      ice-push events, the grounded ice moves easily
                 southwest.    Stringer observed that massive ridges              shoreward across the beach fronts, gouging into
                 are created in December shoreward of Mukluk                      many sediment types.      The sediment types include
                 Island, around the 10-meter isobath.          The ridges         consolidated sandy gravel (13) and consolidated
                 gradually build seaward to the region around                     clays (14).       This set of studies shows that
                 Mukluk Island.     During the late winter, very deep             consolidated,    coarse-grained beach fronts and
                 ice keels gouge into and ground on the offshore                  consolidated clays are gouged similarly by winter
                 shoals in water 20 m deep and more than 20 km                    ice forces.
                 offshore of Mukluk Island. The late-winter ridges
                 that ground offshore protect the shoreward ice                   A third set of studies concerns gouges in the
                 around Mukluk Island from pack ice forces, so                    widespread occurrence of "concrete like" over-
                 there is little additional ridging and gouging in                consolidated silty clay in Harrison Bay (15).
                 waters 15 m deep (11).         The seasonal change in            This study notes that some of the clays are so
                 formation of the ridges indicates that most of the               hard that vibracorers failed to penetrate them.
                 gouging around Mukluk Island probably occurs                     The overconsolidated clays in Harrison Bay are
                 during the middle winter.                                        located in the area in which many ice gouges have
                                                                                  been observed during a five-year study (6). This
                 Ice gouges in Harrison Bay are mainly oriented in                set of studies indicates that overconsolidated
                 two directions, northwest-southeast and north-                   sediments,    perhaps    similar   to    some    reworked
                 east-southwest. This dual orientation was inter-                 materials in Mukluk Island, are gouged by ice.
                 preted (10) as evidence that there may be a second
                 forcing mechanism on gouging ice in Harrison Bay,                The last set of studies indicate a further point
                 aside from the force of the offshore pack ice as                 about gouges. If the overconsolidated silty clays
                 described above. The second forcing mechanism was                in Harrison Bay influenced gouge-disruption rates
                 identified as wind and currents pushing isolated                 over a geologically long period, a flattening in
                 pieces of ice toward the southeast during summer                 the depth profile or relief at the outcrops would
                 (10).                                                            be expected.       However,   this is not observed;
                                                                                  bathymetric charts show that the bay's topography
                 The intensity of ice gouging that occurs in the                  is flat in spite of the different sediment types.
                 summer is probably low compared to that of winter                The flat bathymetry indicates that "concrete like"
                 gouges.    During summer a few deep depressions may              overconsolidated sediments are disrupted at the
                 be formed by grounded ice through a process called               same rate as other sediments.
                 dynamic ice wallow (12).        This process is caused
                 by the open-water wave-induced motion of grounded                Harrison Bay shows no change in slope along the
                 ice.    This motion creates depressions by pounding              survey testlines (6) where the overconsolidated
                 the seabottom. Ice-wallow depressions formed near                silty clays crop out adjacent to or on the
                 Reindeer Island in up to 10 m of water were 0.5 m                testlines.    Rather, bottom depth increases at a
                 (nearshore) to 3 m deep (12).         Ice wallow easily          uniform rate with distance from shore.                 The
                 reduces the cohesion of sediments and enhances                   bathymetric features in and studies of Harrison
                 currents around the grounded ice such that even                  Bay (6,    15) indicate the following: ice-gouge
                 coarse-grained sediments are transported.                        variability that is related to sediment charac-
                                                                                  teristics is minor.
                    3. EFFECT OF ICE GOUGES ON MUKLUK ISLAND
                                                                                  To summarize, ice keels have been observed to
                 The above studies describe ice gouge character-                  gouge many types of sediments similarly.               The
                 istics in natural shelf sediments, as opposed to                 types   include    consolidated sediments       and un-
                 the sandy gravel material in Mukluk Island.            The       consolidated coarse-grained sediments similar to
                 applicability of gouge data for natural sediments                Mukluk Island fill material.
                 to the Mukluk Island shoal is discussed below.

                                                                             574

                4. SEDIMENT DISRUPTION RATE IN HARRISON BAY            crests due to positive relief of shoals."     Other
                                                                       investigators (17) state that they also were
              Harrison Bay is the site of a study by Rearic    (6)     "impressed by the intensity of (ice) gouging on
              of Beaufort Sea ice-gouge-recurrence rates in            shoal crests in the Beaufort Sea compared to that
              addition to the previously mentioned studies of          on the low-lying surrounding terrain."
              ice-gouge characteristics. Rearic (6) studied    the
              rate of seafloor disruption by ice gouges in             The magnitude of the difference in the disruption
              Harrison Bay along testlines that he resurveyed          rate on the top of shoals can be estimated.     The
              yearly for 5 years.   One of the testlines (number       observed gouge rates on the crests of the three
              1) extends from shore to the 14-meter isobath and        shoals in Harrison Bay shoals (6) will be compared
              passes within 7 km of the Mukluk Island site.            to the rates on the surrounding seafloor.    Rearic
              Rearic's data (6) for Testline 1 show that the           observed generally lower disruption rates both on
              annual volume of sediment disrupted increases with       and off the shoals in eastern Harrison Bay than
              water depth in almost a linear relationship              the rates in the central part of Harrison Bay.
              (redrawn in Fig. 1).    Rearic's calculations (6)        The low level of the rates possibly is because of
              result in an average minimum disruption rate. His        the presence of offshore shoals that protect from
              relationship indicates that for the water, around        intensive gouges the eastern part of the bay.
              Mukluk Island (which is 15 m deep), a minimum of         Also, the three shoals which are only several
              7,000 m3 of sediment is disrupted annually within        kilometers apart may influence the intensity of
              an area of 1 km2.                                        gouging on one another.     Regardless of general
                                                                       level of the rates, the data for the three shoals
                   5. SEDIMENT  DISRUPTION RATES ON SHOALS             indicate the comparative rates on and off of
                                                                       shoals.
              The sediment -dis rup t ion rate on the top and  sides
              of the Mukluk Island shoal may be substantially          The rates on and off the shoals will be related to
              different than the sediment-disruption rate on the       Rearic's (6) data on. the height of the shoals
              surrounding seafloor.    The unusually high dis-         above the seafloor.    The shoreward and leeward
              ruption rate on the top of shoals is illustrated         sides of a shoal may be protected from gouges by
              in Figure 1 which shows the rates on the top of          the shoal.   Therefore, comparisons will be made
              three shoals in eastern  Harrison Bay.  Rearic (6)       with the seafloor rate on only the seaward side of
              describes the "high (ice) impact rate on shoal           shoals, which is the primary direction of ice
                                                                       encroachment at Testline 2 (6).

                       -                                               One shoal extends 3.5 m above the surrounding
                                                                       seafloor (16, Figure 7).   The disruption rate on
                                                                       this shoal crest is 6 times greater than the rate
                    6-                                                 on the seaward side of the shoal (16, Table III) .
                                                                       Two of the shoals extend 2 m above the surrounding
                                                                       seafloor.   The disruption rates on the shoal
                                 TESTLINE 1.                           crests are 1.5 and 4 times greater than the rates
                                                                       on the seaward sides of the shoals.

                                                                       The above data indicate that the disruption rate
                A   4
                0 C4                           Shoal                   on the top of the Mukluk Island shoal, when it
                  -E                           Location                extends just 2 m above the seafloor, will be at
                  _X                           along                   least 1.5 times greater than the seafloor rate.
                E                              TESTLINE 2.             When the Mukluk Island shoal is still 3.5 m above
                  E                                                    the seafloor, the disruption rate may be 6 times
                V) 02-                                                 greater than the rate on the seaf loor.   When the
                  0                                                    shoal crest is 7.5 m above the bottom (and is at
                                                                       -7.5 m water depth), the disruption rate will
                                                                       probably be greater than 6 times the seafloor
                                                                       rate.   The factor of 6 is probably a minimum
                                                                       estimate for the Mukluk Island shoal    at -7.5 m
                                                                       because of the shoal's relatively small size (less
                    0  5             10              15                than 250 m diameter).
                             Water Depth (m)                           For the following estimations of the    disruption
                                                                       rate on Mukluk Island shoal, the rate   is assumed
              Figure 1.  Mean volume of sediment disruption by         to be at least 6 times the seafloor rate at Mukluk
              ice gouges along two testlines in Harrison Bay,          Island when the shoal is at -7.5 m water depth.
              redrawn from Rearic (16, Fig. 14).      Testline I       Rearic (6) calculated that the seafloor disruption
              extends from shore to the 14-meter isobath and           rate near Mukluk Island equals 7,000 m3/km2/year,
              passes within 7 km of the Mukluk Island site in          so we estimate the rate on a small -7.5 m shoal
              central Harrison Bay; Testline 2 passes over three       crest to equal at least 42,000 m3/km2/year.
              shoals in eastern Harrison Bay.    Rearic explains
              that the gouges are measured for a 250-m-wide
              corridor along 1-m-water depth intervals and that
              the disruption estimate is a minimum.

                                                                  575

                            6. SEDIMENT-DISRUPTION RATE ON                           8.      Barnes, P.W.       1981.     Ice Gouging.        In:
                                   MUKLUK ISLAND SHOAL                               Beaufort Sea Synthesis-Sale 71, D.W. Norton              ;-nd
                                                                                     W.M. Sackinger, eds. Juneau, AK:           U.S. Dept. of
                  The effect of the above disruption rate on Mukluk                  Commerce (USDOC), National Oceanic and Atmospheric
                  Island shoal will be estimated for just one depth.                 Administration (NOAA), Outer Continental Shelf
                  The depth of -7.5 m will be used because it is                     Environmental Assessment Program (OCSEAP), pp.
                  half of.the water depth. Further, the -7.5 m depth                 100-108.
                  is several meters below the -4.6 m. water depth to                 9.    Dames and Moore.      1983.   Final Report, Sohio
                  which currents are expected to erode the island                    Mukluk Well No.       1, Harrison Bay Alaska, Biolog-
                  relatively quickly (2). At a depth of -7.5 m, the                  ical Survey, February 16- 22, 1983.            Unpublished
                  Mukluk Island shoal has a radius of about 94 m                     report    for    Sohio    Alaska    Petroleum     Company,
                  (1).   The area on top of the shoal at -7.5 m. will                Anchorage, AK, 14 pp.
                  equal about 28,000 m2.        At the ice-gouge-disrup-
                  tion rate that is estimated above (42,000 m3/km2/-                 10.     Craig,   J.D. and G.P. Thrasher.               1982.
                  year), the sediment disrupted annually might equal                 Environmental    Geology of Harrison Bay,         Northern
                  about 1,200 m3 for Mukluk Island shoal when it is                  Alaska.    Open-File Report 82-35. USDOI,         USGS, 11
                  -7.5 m. deep.     At this disruption rate, it should               PP.
                  take an average of 23 years to disrupt I vertical
                  meter of material on the entire surface of the                     11.   Stringer, W.J.      1981.   Seasonal Ice    Morphol-
                  shoal (about 28,000 m2).                                           ogy Maps. In: Beaufort Sea Synthesis-Sale         71, D.W.
                                                                                     Norton anT W.M. Sackinger, eds.              Juneau, AK:
                  In conclusion, ice gouge rates indicate that it                    USDOC, NOAA, OCSEAP, Appendix C, 13 p.
                  should take an average of about 2 decades to
                  disrupt 1 vertical meter of material on the entire                 12.   Reimnitz, E. and E. Kempema.         1982. Dynamic
                  surface of the shoal.                                              Ice-Wallow Relief Of Northern Alaska's Nearshore.
                                                                                     Journal Of Sedimentary Petrology 52(2):451-461.
                                      7. REFERENCES
                                                                                     13.   Shapiro, L.H., R.C. Metzner, A. Hanson, and
                  1.     Anderson, L.M. and C.B. Leidersdorf.            1988.       J.B. Johnson.     1984.    Fast Ice Deformation During
                  Arctic Island Abandonment: Planning and Implemen-                  Ice-Push and Shore Ice Ride-Up. In: The Alaskan
                  tation for Mukluk Island. Proceedings of the 20th                  Beaufort Sea: Ecosystems and Environments, P.W.
                  Annual Offshore Technology Conference, Houston,                    Barnes, D.M. Schell, and E.         Reimnitz, eds.       New
                  TX, pp. 49-60.                                                     York: Academic Press, Inc., pp. 137-158.

                  2.     Standard Alaska Production Company.             1987.       14. Phillips, L. and T. Reiss.          1983.     Nearshore
                  Mukluk Island     Reclamation and Abandonment Plan.                Marine Geologic Investigations, Pt. Barrow To
                  Anchorage, AK.                                                     Skull Cliff, Northeast Chukchi Sea.            In:   USDOC,
                                                                                     NOAA, OCSEAP, Final Reports Of Principal Inves-
                  3.     Reimnitz, E.     1987.    Personal communication            tigators 34:157-181.
                  to T.     Newbury, Oceanographer, U.S. Dept. of
                  Interior (USDOI), Minerals Management Service,                     15.    Reimnitz, E., E. Kempema, R. Ross, and P.
                  Anchorage, AK, in June 1987 from Erk Reimnitz,                     Minkler.     1980.        Overconsolidated        Surficial
                  Marine Geologist, USDOI, U.S.          Geological Survey           Deposits On The Beaufort Sea Shelf.               Open-File
                  (USGS), Menlo Park, CA.                                            Report 80-2010. USDOI, USGS, 37 pp.

                  4.     Gulf Oil Canada Limited.       1979. Analysis of            16.    Rearic, D.M.       1985.    Temporal and Spatial
                  Side-Scan Sonar Sea Bed @magery from Repeated                      Character of Newly Formed Ice Gouges in Eastern
                  Surveys off Pullen Island -Beaufort Sea.                 Un-       Harrison Bay, Alaska, 1978 -1982.             In:    USDOC,
                  published report prepared in May 1979 for Gulf Oil                 NOAA, OCSEAP, Final Reports Of Prin@_ipal Inves-
                  Canada Limited, Ottawa, Ontario, Canada, 28 pp.                    tigators 52:605-700.

                  5.      Shearer, J., B. Laroche, and G. Fortin.                    17. Reimnitz, E. and E. Kempema. 1985. Pack Ice
                  1986.      Canadian Beaufort Sea 1984 Repetitive                   Interaction with Stamukbi Shoal, Beaufort Sea,
                  Mapping    of   Ice    Scour.    Environmental      Studies        Alaska. In: USDOC, NOAA, OCSEAP, Final Reports Of
                  Revolving Funds Report No.        032. Ottawa, Canada,             Principal Investigators, 34:251-282.
                  43 p.
                                                                                     18.    We thank Peter Johnson and James Craig for
                  6.     Rearic, D.M.       1986.    Temporal and Spatial            their expert technical reviews, Elinore Anker for
                  Character of Newly Formed Ice Gouges in Eastern                    editorial help, and our supervisor, Tom Boyd, for
                  Harrison Bay, Alaska, 1977-1982. Open-File Report                  general encouragement.
                  86-391. USDOI, USGS, 18 pp.

                  7.     Barnes, P.W., D.M. Rearic, and E. Reimnitz.
                  1984.    Ice Gouging Characteristics and Processes.
                  In:    The Alaskan Beaufort Sea:          Ecosystems and
                  Fn-vironments, P.W. Barnes, D.M. Schell, and E.
                  Reimnitz, eds.      New York:     Academic Press, Inc.,
                  pp. 185-212.

                                                                                576

                                      DESTRUCTION OF OFFSHORE PLATFORMS BY ACCELERATED GALVANIC CORROSION

                                                                  Risque L. Benedict

                                                     Corrosion Consulting Service Corporation
                                                                   1530 Tioga Trail
                                                             Fallbrook, California 92028
                                       ABSTRACT                                 were 630 platforms which will need to be
                                                                                removed in the next 12 years from the Gulf
                 There are two principal drawbacks         to existing          of Mexico.    The cost for this platform removal
                 platform removal techniques.        The   most common          is estimated at $7.5 billion           by the U.S.
                 method    is  using explosives        to  sever the            National    Research    Council.3      In   1987    it
                 piles below the mud line, which kills fish                     was reported that there were           139 offshore
                 and sea turtles.        In addition,      many deep            structures in the North Sea            of which 40
                 water structures are too heavy            to remove            are deep water        structures.      The estimate
                 with   the existing derrick         barge   capacity           for platform removal for the           North Sea is
                 after     toppling.        Accelerated      galvanic           approximately $8.9 billion.4           BHP estimates
                 corrosion is proposed as a new concept to                      total    costs for clearing 13 platforms in
                 destroy offshore platforms.          In   one scheme           the Bass Straights offshore Australia would
                 envisioned, the use of accelerated galvanic                    run around $1 billion.5
                 corrosion    would    reduce    the       quantity of
                 explosives required for platform toppling,                     Alternatives to platform removal have been
                 thereby    minimizing     ecological      damage  to           considered.     One possible use is recycling
                 @ea life.    The accelerated galvanic corrosion                the platforms and reutilizing them.             Still
                 is achieved by      applying a special         copper          another     program    has   been      toppling    the
                 clamp-on, device to the platform          structural           platforms     in   place   to    create   artificial
                 member that is      to be destroyed.        Galvanic           reefs    for marine     life   habitats,    such as
                 corrosion rates     of eight inches of steel                   Louisiana's Artificial Reef Program (LARP).
                 per year occur at a slit placed in        the copper           However, the U.S. Navy has raised objections
                 film.     Steel  members    one    inch   thick are            over     artificial    reefs,    claiming     foreign
                 severed by corrosion in about two months.                      submarines could use them for cover.6 Another
                                                                                innovative solution proposed for the North
                                                                                Sea by the British Ministry of Energy is
                                                                                the Fairy Lights concept.         In this concept
                        BRIEF HISTORY OF PLATFORM REMOVAL                       the platforms would be illuminated and left
                                                                                in situ, becoming beacons in the ocean as
                 A 1958, Geneva treaty requires that offshore                   a warning to marine traffic.7
                 platforms be removed within a year after
                 they stop producing. Branches of the Interior                     EXISTING TECHNOLOGY FOR PLATFORM REMOVAL
                 and    Commerce  departments would        like   some
                 platforms left in place or used as building                    Virtually all      of the platforms that have
                 blocks    for artificial     reefs.       The  United          been recovered offshore to date have been
                 States, along with Britain and Norway, is                      removed by explosives.      This usually consists
                 urging treaty changes to allow this.        However,           of placing a       charge within the platform
                 the U.S. Navy has called the platforms a                       legs below the mudline and remotely detonating
                 threat to national security.       Several coastal             the. explosive.    The platform jacket is then
                 states    have    enacted     "Save       the  Ri gs"          refloated and picked up by a derrick barge.
                 legislation.    Louisiana has designated eight                 Finally the jacket is placed on a dumb barge
                 areas where obsolete rigs can be scuttled.                     and brought ashore.
                 It   has   also    established     conditions     for
                 transferring    liability    for    the   old    rigs          The problem with explosives is the destruction
                 from oil companies to the state.1                              of fish and sea turtles, which congregate
                                                                                in  large numbers around offshore structures.
                 Over the     past   40 years,     4,187 platforms              An  additional problem is the lift capacity
                 have been installed on federal Gulf of Mexico                  of existing crane barges.           Until   recently
                 leases.   Of that total, 3,080 fixed platform                  crane barge capacity was limited to 2,000
                 drilling   structures    remain    in     place.  it           tons.    There is now a single crane barge
                 is estimated that between January 1,             1947          with    a  pickup    capacity of       16,000   tons.
                 and August 31, 1987 a total of 659 structures                  Even this capacity is far short of the largest
                 have been removed from the Gulf of Mexico.2                    steel    jacket    placed     so    far,    platform
                 In June 1988 it was reported that there                        Bullwinkle, which weighs over 50,000 tons.

                                                           CIH2565-6/88/00007 577 $1 @1988 IEEE

                          Proposed Platform Removal Techniques                    Equations 1 and 2 below.
                    There are a number of innovative techniques8                         Anodic Reaction
                    that   have     been proposed   for the      removal                 (oxidation)
                    of offshore platforms, among which are cutting
                    and sawing devices, either manned or operated                        Fe -@ Fe++ + 2e-                  (1)
                    by remote operated vehicles (ROV's).           These
                    proposed solutions have obvious drawbacks.                           Cathodic Reaction
                    For example, the cutting and sawing operation                        (reduction at the   copper cathode)
                    by   either     man  or   ROV's    is   potentially
                    dangerous.      At some point during the cutting                     02 + H20 + 4e- -4 40H-            (2)
                    or   sawing     operation   when   the     structure
                    collapses either the man or the multimillion                  Our    experiments   show that       reaction 2 is
                    dollar ROV will be imperiled. In the Fairy                    the    controlling mechanism.        Therefore, the
                    Lights concept the oil companies face the                     more oxygen that reacts at the cathode (the
                    continued liability of injury to trespassers                  copper surface      of the ACA),      the greater
                    on the platforms.     In addition, the structures             the    steel    corrosion   rate     at  the  anode.
                    pose   an   obstacle    to    both    military   and          Because    of   limited    oxygen    solubility    in
                    'commercial marine traffic.                                   sea water, about 6 to 10 mg/kg (milligrams
                                                                                  per kilogram), the reaction is limited by
                    The    author    believes     that    the  use     of         the cathode (copper) area.           The result as
                    accelerated corrosion as a method of platform                 shown in Table 1 is that the larger the
                    removal has merit when compared to existing                   copper    to   steel   ratio,     the    higher  the
                    concepts.       Destruction   of      platforms    by         corrosion rate of steel.
                    accelerated     corrosion   can   be  utilized     to
                    remove existing structures.                                                   DESCRIPTION OF THE
                                                                                           ACCELERATED CORROSION ASSEMBLY
                                    HOW THE CONCEPT WORKS
                                                                                  Figure 1 shows the details of the accelerated
                    Accelerated corrosion and ultimate collapse                   corrosion    assembly    (ACA).      A   variety   of
                    of the platform member is achieved through                    ACA sizes will be required to fit the many
                    galvanic    corrosion.      Accelerated     galvanic          tubular    diameters    encountered    in   offshore
                    corrosion is achieved through the well-known                  pl atform    construction.    A      custom fit    is
                    technique of using a large cathode and a                      not required, however.      For example, a single
                    small anode.     Corrosion rate is proportional               ACA is expected to fit tubulars four feet
                    to the cathode/anode ratio.       This is achieved            to six feet in diameter.       As shown in Figure
                    by utilizing a large copper cathode with                      1,  the essentials of ACA are the critical
                    a thin circumferential slit at the center.                    gap of 0.005 inches in the slit at the center
                    This   slit     is centered over the platform                 of  the assembly.      This slit is located at
                    member at the point where the tubular member                  the exact point where the platform tubular
                    is to be severed by corrosion.        This geometry           is  to be severed.      The ACA is first secured
                    produces cathode to anode ratios exceeding                    at  the location on a vertical or horizontal
                    10,000:1.       Such a cathode to anode ratio                 tubular where destruction by corrosion is
                    will produce galvanic steel 'corrosion rates                  desired.     Securing    is  accomplished     easily
                    in sea water of approximately eight inches                    by cinching straps as shown in Figure 2.
                    per year.       Table 1 shows corrosion rates                 Thermite charges are then battery detonated,
                    measured in our laboratory for varying cathode                which welds the stainless steel blocks of
                    to anode ratios.                                              the ACA to the tubular members as shown
                                                                                  in Figure 3.      The lightweight copper frame
                                    Corrosion Mechanism                           of ACA is securely fastened to each stainless
                                                                                  steel    block   by    stainless     steel   rivets.
                    The    accelerated    galvanic     corrosion     cell         The in situ ACA is shown in Figure 3.            The
                    has   four components.        These   are a     large         resultant geometric configuration will give
                    copper cathode; a small          steel  anode (the            the large cathode to anode ratio necessary
                    .005 inch slit in the accelerated corrosion                   to achieve the high rate of corrosion required
                    assembly); an electrolyte (sea water); and                    for rapid destruction of platform tubulars.
                    a metallic conductor between the anode and
                    cathode.        In the    accelerated      corrosion                        DISMEMBERMENT SEQUENCE
                    assembly (ACA), this conductor is the thermite
                    weld which metallically fuses together the                    Platform       dismemberment      by     accelerated
                    ACA    and      the   platform     tubular.       The         corrosion    requires    the    placement   of   the
                    electrochemical reactions are shown in                        accelerated     corrosion   assembly     (ACA)   over

                                                                            578

                 the   tubular     member  to    be   severed.    The          protrudes nearly 400 feet above the ocean
                 assembly is placed around the tubular member                  floor.    Proper   placement    of   ACA's    could
                 by diver or ROV.         In some cases the ACA                reduce this 400 foot protrusion to between
                 can    be   utilized    for   platform    toppling.           30 feet and 50 feet after about six months
                 In other cases it will be used for platform                   of accelerated corrosion.      This would create
                 dismemberment.       When    used    for  platform            a barrier reef marine habitat in situ and
                 dismemberment,     placement    of   the  ACA    can          avoid costly refloatation and the leasing
                 occur   either     prior  to    or   subsequent  to           of a heavy duty derrick barge.
                 platform toppling depending on       the economics.
                 Water depth will usually determine whether                    There  are   a   number of      platform    removal
                 the   accelerated    corrosion    assembly    (ACA),          variations where the use of ACA would be
                 when   used   for platform dismemberment,        is           advantageous.   ACA would be more economical
                 placed before or after platform toppling.                     than platform removal for in situ destruction
                 As   a  hypothetical     example,    for a jacket             of   the   platform   and   creation   of marine
                 in 1,000 feet of water, let us make the                       habitats.   As a natural process, corrosion
                 assumption that it is acceptable to leave                     not only does      not   ham the environment,
                 the lower 150 foot section of the jacket                      but it also eliminates or reduces the use
                 secured   by piles      in   place.   The balance             of explosives and their attendant detrimental
                 of the jacket is to be cut by ACA     into pieces,            effect on marine life.
                 none of which weigh more than        the capacity
                 of a medium sized crane barge, e.g., 2,000                         COMPARISON OF ACCELERATED CORROSION
                 tons.    The accelerated corrosion assemblies                             CONCEPT TO ALTERNATIVES
                 are placed at the appropriate points.            if
                 all the ACA's have the same cathode to anode                  Table  2 shows the ACA in comparison with
                 ratio,    the   uppermost    platform     segments,           other forms of platform removal.       Two things
                 since they have lighter wall tubulars, would                  stand out.    ACA reduces the risk to both
                 be expected to topple first.         However, the             man and marine life by a substantial margin.
                 time to failure sequence can be controlled                    ACA is estimated to cost about 10% more
                 by varying the cathode to anode ratios on                     than platform removal using explosives and
                 the ACA's.      The   time   frame for platform               medium capacity crane barges plus floatation.
                 dismemberment    ordinarily     would   vary    from
                 two to six months.      The crane barge recovers                                 CONCLUSIONS
                 the more manageable 2,000 ton subsections
                 and   places   them on     dumb   barges.      These          From the above analysis it can be concluded
                 subsections    can  be either brought ashore                  that since economics usually dictates choices,
                 or placed in marine barrier reefs.          Removal           the existing techniques of explosives, medium
                 of the 150 foot platform base will require                    capacity lift barges, and floatation equipment
                 explosives or other means.        The pile guides             will continue to be used over the alternatives
                 prevent attachment of the ACA's directly                      analyzed unless society is willing to pay
                 to the piles.      However, even if explosives                a premium for reduced risk to man and nature.
                 are now used to remove the 150 foot base,                     If   reduced   environmental     damage   warrants
                 the great majority of marine life that was                    a premium, then this needs to be spelled
                 clustered around the upper 850 feet of the                    out in our national policy.      The accelerated
                 jacket will     be spared.     In this concepti,              corrosion   assembly    concept     could   become
                 two important goals are realized.            Damage           a  viable alternative       to existing    removal
                 to marine life is minimized.         Large savings            techniques    within  a     year   once   national
                 are   achieved    by  sectioning     the  platform            priorities are established.
                 into smaller segments that can be removed
                 by a    2,000   ton   crane    barge   instead   of                              REFERENCES
                 floatation   tanks or a       costly 16,000 ton
                 crane barge.                                                  1.   Sterba, James P.,      "Save the Oil Rigs?
                                                                                    Yes, Some Say, They    Are Habitat-Forming",
                 In another scenario, again using the 1         ' 000               The  Wall    Street    Journal,   April    29,
                 foot jacket as an example, the jacket is                           1988, page 1.
                 severed into two sections of approximately
                 the same weight.      Assume that the sections                2.   "3,080   Platforms     Still  in   Place    in
                 @elected will require cutting the platform                         U.S.  Gulf", Ocean     Oil  Weekly Report,
                 into two parts at approximately -650 feet                          Volume 22, Number      4, October 5, 1987,
                 MLLW.   The ACA will be appropriately placed                       page 1.
                 around platform legs or braces at the -650
                 foot level by divers or ROV's several months                  3.   "Platform Removal      Costs Could Run in
                 in advance of platform toppling.          Platform                 Billions;   Reuse    on Rise",    Ocean   Oil
                 toppling is accomplished in the conventional                       Weekly Report, Volume 22, Number 36,
                 way by explosives severing the piles below                         May 16, 1988, page 2.
                 the mud line.       The base of the platform

                                                                        579

                        4.     Editorial      Comment,        "Could     Corrosion                                          TABLE 1
                               Assist with Offshore Platform Removal?",
                               Corrosion Prevention & Control, Volume                                COPPER/STEEL RATIO VERSUS CORROSION RATE
                               34, Number 2, April 1987, page 31.

                        5.     "Ease Platform Removal Guides, Operators
                               Ask Australian Government", Ocean oil
                               Weekly Report, Volume 22, Number 41,                               Cu/Fe Ratio                       Steel Corrosion Rate
                               June 20, 1988, page 2.                                                                               inches per year (1py)

                        6.     "Platform Removal         Costs Could Run in                            1:1                                    0.152
                               Billions;      Reuse on        Rise",    Ocean     Oil
                               Weekly Report, Volume 22, Number 36,                                    1:10                                   0.638
                               May 16, 1988, page 2.
                                                                                                       1:100                                  2.59
                        7.     Editorial       Comment,       "Could     Corrosion
                               Assist with Offshore Platform Removal?",                                1:1,000                                4.86
                               Corrosion Prevention & Control, Volume
                               34, Number 2, April 1987, page 32.                                      1:10,000                               8.11

                        8.     W.L. Alexander Jr., T.G. Jackson, and                                   1:20,000                              10.5
                               D.J.     Hardin,       "Engineering       the     Cost
                               Out of Platform Removals and Salvage",
                               Presented at the 20th Annual Offshore
                               Technology Conference in Houston, Texas,
                               May 2-5, 1988.

                                                                                          TABLE 2

                                                              COMPARISON OF REMOVAL TECHNIQUES FOR A 1,000 FOOT PLATFORM

                                                                                                    Explosives,     Underwater
                                                                         ACA and                    Medium Crane    Cutting
                                                                         Medium      Explosives     Barge, and      Devices
                                                                         Crane       and Heavy      Buoyancy        and Medium
                                                                         Barge       Crane Barge    Tanks           Crane Barge     Comments

                             1. Total Time for Platform                      18           4                8              12        Explosives plus heavy
                                 Removal (months)                                                                                   crane barge are most
                                                                                                                                    rapid for removal.

                             2. Total Time for Divers or ROV                 4            1                3               8        Explosives plus heavy
                                 on Station (months)                                                                                crane barge minimize
                                                                                                                                    diver or ROV time on
                                                                                                                                    station.

                             3. Comparative Time for ROV or                  4            1                2              20        Explosives plus heavy
                                 Divers Underwater                                                                                  crane barge minimize
                                                                                                                                    ROV or diver time
                                                                                                                                    underwater.

                             4. Danger to Man and Marine Life                1           10                20              5        Accelerated corrosion
                                                                                                                                    assembly reduces risk
                                                                                                                                    to man and marine life
                                                                                                                                    by a large margin.

                             5. Relative Cost                                1.1          1.5              1.0             2.5      Existing removal
                                                                                                                                    techniques with
                                                                                                                                    explosives, medium
                                                                                                                                    crane barges, and
                                                                                                                                    buoyancy tanks is
                                                                                                                                    least expensive.

                                                                                          580

                                                                                                                                                 .FIGURE 3

                                                                                                                                        ACA    ATTACHED TO TUBULAR

                                                    FIGURE I

                                     ACCELERATED CORROSION ASSEMBLY

                                                                                                                                                               WELD CONTAINER

                                                                                                                                                                     TUBULAR

                                                                   STAINLESS STEEL
                                                                   ATTACHMENT DEVICE FOR
                                                          15-- ELEC./MECH     . CONNECTION

                                             A
                                                                             10 KL. COPPER (TYP.)
                                               A                                                                          5 NIL. GAP                            WNCHING STRAP
                                                    OVERLAP TO                   30 ML. STEEL (TYP.)
                                                    PERMIT VARYING
                                                    DIAMETER TUBULAR

                                                                                                                                                             STAINLESS STEEL THERMITE
                                                                                                                                                    A-9--    WELD CONTAINER

                                                                                                                                                             WELD METAL FUSED TO SURROUNDING METAL

                                                                                                                                                                           STAINLESS STEEL RIVET -
                                                                                                                                                                           ATTACHING STAINLESS STEEL
                                                                                                                                                                           WELD CONTAINER TO COPPER
                                                                                                                                                                           CLAD STEEL

                          5 ML. GAP (TYP.)

                                                    -   10 ML. COPPER (TYP.)                            COPPER                        TUBULAR
                                                    14-                                                 CLAD -z@
                            SECTION DETAIL AA           ju 14L. STEEL (TYP.)                            STEEL                          SECTION DETAIL BB

                                                                                                                               ELECTRICAL/MECHANICAL ATTACHMENT

                                                                                             FIGURE 2

                                                                                         CINCHING STRAP

                                                      PLASTIC TENSION
                                                      HANDLE

                                                      PLASTIC
                                                      RATCHETING
                                                      HEAD

                                                      PLASTIC
                                                      STRAP
                              CA
                                                                             '0

                                                    OV RLAP To
                                                    PE
                                                    RMIT VARY ING
                                                    D
                                                    I
                                                        TER  TUBULAR

                                                                                                                                                              TAINLESS  S
                                                                                                                                           @&--@WELD              CONTAI
                                                                                                                                                             WELD  METAL
                                                                                                                     ?IBI

                                                                                                      581

                                                                 CORROSIVE-WEAR OF BUOY CHAIN

                                                                           Craig A. Kohler

                                                  U.S. Coast Guard Research and Development Center
                                                                              Avery Point
                                                                Groton, Connecticut 06340-6096

                                            ABSTRACT

                  Laboratory studies were conducted to
                  determine         the     causes        of buoy           chain
                  degradation and how the corrosive-wear                                                                                       buoy
                  resistance of steel could be improved.                                           wave         wave
                  Undisturbed          corrosion         and       accelerated                      h ight      crest             wind
                  corrosive-wear tests were conducted on
                  plain carbon and alloy steels.                       Analysis
                  of the tests included the effects of
                  composition, hardness, and microstructure
                  on wear resistance.                                                                      T
                                                                                                            wave              Chain  Mooring
                  Chain moorings were evaluated for pitting                                 water           trough                (90 ft) ---------
                  corrosion resistance, reduction in link                                   depth
                  diameter, overall weight loss, and ob-                                   (35 ft)
                  served appearance after a two year f ield                                                     current
                  test. Results suggest which steels may                                          sinker        -------
                  provide increased corrosive-wear resis-                                       (20001 .bs)
                  tance and longer chain service life.

                                                                                                                   "i4e, r
                                       1. INTRODUCTION

                  One of the primary missions of the U.S.                                            FIGURE 1.         Buoy   and   Mooring
                  Coast Guard is maintaining the aids to
                  navigation within the waterways of the
                  United States and its territories.                         Per-         Although the mooring                 chain acts as a
                  formance of this mission requires periodic                              damping mechanism, the              chain itself is in
                  inspection and repair of a large number of                              nearly continual motion.                        It is the
                  fixed and floating structures.                      Servicing           motion of the chain which produces wear
                  of aids to navigation accounts for a                                    of the links.            Interlink wear occurs be-
                  significant portion of the Coast Guard's                                tween the contact surfaces of adjacent
                  budget.        In an effort to reduce servicing                         links. The section of the chain which is
                  costs, the Coast Guard has established a                                in contact with the bottom, referred to
                  goal of a six year life cycle for its                                   as the chafe section, is subjected to
                  fixed and floating aids to navigation.                                  abrasion. Therefore, the chafe section is
                                                                                          exposed to additional wear on the outer
                  The typical floating aid to navigation,                                 surfaces on the links, referred to as
                  illustrated in Figure 1, consists of a                                  barrel wear.
                  buoy, steel chain, and concrete sinker.
                  Each component is designed to withstand                                 The corrosion of plain carbon steel in
                  the maximum anticipated wind, current, and                              seawater is well established.                         Uniform
                  wave f orces.          Resistance to these forces                       corrosion rates of 10 to 15 millimeters
                  are provided by the horizontal component                                per year (mpy) in the f irst year, then
                  of the tension in the chain created when                                slowing to less than 5 mpy after 2 to 3
                  the chain is picked of f the bot                     'tom and,          years for undisturbed specimens have been
                  ultimately, the horizontal holding force                                documented [1].                However, the ferrous
                  of the sinker.             Additionally, the weight                     oxide        surface          layer       which        reduces
                                                                                                      e
                                                                                          _7+                                       7__@
                                                                                                                                    ,noring _ r

                  of the chain suspended in the mooring acts                              corrosion is loosely adherent.                      When the
                  as a        shock absorber against dynamic                              oxide layers are removed, the initial
                  loading.                                                                corrosion rates are re-established.

                                                                                     582
                                                                                             United States Government work not Protected by copyright

                  Corrosive-wear is the synergistic effect                                     The first set of laboratory experiments,
                  of the corrosion and wear processes which                                    conducted in 1984 by D. May, will be
                  results in the rapid degradation of steel                                    referred to in the subsequent text as
                  chain in seawater.                 The protective oxide                      Experiment A. The second set of laboratory
                  layers are continually removed by the wear                                   tests, conducted in 1985 by C. Kohler,
                  process exposing unprotected metal.                             The          will be referred to as Experiment B. Both
                  corrosive-wear mechanism is most destruc-                                    studies were funded by the U.S. Coast
                  tive to the chafe section of the chain                                       Guard [2].
                  mooring.          In Figure 2, the chafe section
                  in the right of the picture was worn to
                  the point where failure of the mooring
                  ?ccurred. Chafe section wear such as this
                  is most common in areas of high currents                                                     2. LABORATORY TESTING:
                  and wave action.                                                                                  EXPERIMENT A

                                                                                               The research in Experiment A included
                                                                                               three objectives. The first objective was
                                                                                               to       identify          which        mechanisms            were
                                                                                               responsible for the majority of chain
                                                                                               material loss. The second was to design
                                                                                               and      construct           a      laboratory           testing
                                                                                               'apparatus which would simulate buoy chain
                                                                                               degradation.           Finally, by testing several
                                                                                               other steels and comparing the results to
                                                      "A                                       the baseline 1022 steel it could be
                                                                                               determined which material properties were
                                                                                               most important in reducing corrosive-wear.
                                                    V
                                                                                               The apparatus used to conduct the testing
                                                                  4
                                                                                               is shown in Figure 3.                      A plastic tank
                                                                                               contained the distilled water and seawater
                                                                                               for the tests.             Mounted on the bottom of.
                                                                    h,
                                                                                               the tank was a                 sanding disk used to
                                                                                               provide         an    abrasive          surface       for the
                                                                                               corrosive-wear tests.                   The carriage and
                                                                                               s
                                                                    v,                          pecimen holder maintained contact between
                                                                                               the steel specimen and the abrasive disk.
                                                                                               The loading and motion of the                         apparatus,
                                                                                               were designed to simulate those seen by
                             FIGURE 2. Abraded Buoy                 Chain                      buoy chain links.

                  Presented in this paper are                       the results                The      steels         selected          for      study          in
                  from two laboratory studies and a two year                                   Experiment A, in addition to the baseline
                  field test on the effects of corrosive-                                      ASTM 1022 steel, were ASTM 1045 and 4140
                  wear on plain carbon and alloy steel buoy                                    steels.         Selection of the 1045 steel wag
                  chains.          The compositions of the steels                              to determine the effects of increasing the
                  that were tested are listed in Table 1.                                      carbon content from the baseline 1022. The

                                                                                        TABLE 1
                                                                                 STEEL COMPOSITION

                                                                                                                                            Hardness
                               steeL          9           tin                                                                      !LO         (Rc)

                               1022       0.18-0.23    0.7-1.0      0.04      0.05

                               1022HT     0.18-0.23    0.7-1.0      0.04      0.05                                                             41

                               4140       0.38-0.43    0.75-1.0     0.035     0.04      0.15-0.35                   0.8-1.0     0.15-0.25      28

                               4140HT     0.38-0.43    0.75-1.0     0.035     0.04      0.15-0.35                   0.8-1.0     0.15-0.25      20

                               4340       0.38-0.43    0.65-0.85    0.035     0.04      0.15-0.35      1.65-2.0     0.7-0.9      0.2-0.3       27

                               8740       0.38-0.43    0.75-1.0     0.035     0.04      0.15-0.35      0.4-0.7      0.4-0.6      0.2-0.3       25

                               8620       0.18-0.23    0.70-0.9     0.035     0.04      0.15-0.35      0.4-0.7      0.4-0.6     0.15-0.25      30

                                                                                        583

                                                                                            The weight loss coefficients were plotted
                                                                                            as a function of time.                        of particular
                                                                                            interest was the shape of the curves for
                                                                                            each material.            For the f irst few hours,
                                                                                            there appeared to be an incubation period
                                                                Motor                       which       was      characterized            by     a     rapid
                                                                                            increase in the material loss coefficient.
                                                                                            This phenomena is characteristic of the
                            F- Drive Shaft    @@DM    ion=>                                 wear process due to the abrasive cutting
                                                                                            grooves into the material.                    Following the
                                  Calomel                                                   incubation stage was a steady state
                                  Electrode                                                 region.        During this phase the surface of
                                                                                            the specimen experiences consistent wear
                                                                                            due to the reduction of asperities on the
                     Ll               Specimen                                              abrasive surface.              corrosive-wear of buoy
                   Weight                 Abrasive                                          chains occurs almost entirely in the
                                            Disk                                                    y state region. Therefore, it is the
                                                                                            stead
                                                                                                                                          region which
                                                                                            slope in the steady state
                                                                                      I     provides the best indication                  of corrosive-
                                                                                            wear rates.               A summary           of the data
                                                                                            obtained from all the graphs is given in
                                                                                            Table 2.
                   FIGURE 3. Tank and Motor Set-up Apparatus:
                                  Experiment A
                                                                                                                         TABLE 2
                                                                                                       SUMMARY OF MATERIAL LOSS COEFFICIENT RATES

                                                                                                                               MATERIAL LOSS COE -FJICIENT
                                                                                                STEEL       TYPE OF TEST              RATES (x1O )
                   influence         of      alloying          additions           on                                                              2_
                   corrosive-wear would be investigated in                                      1022       UNDISTURBED SEAWATER           1.84 mg/cm hr
                   the 4140 steel. The effects of hardening
                   by     changing          the      microstructure              was            1045       UNDISTURBED SEAWATER           1.93
                   achieved by heat treating the 1022 steel
                   at 1650*F for thirty minutes followed by a                                   4140       UNDISTURBED SEAWATER           1.79
                   water quench. The heat treatment produced
                   a martensitic surface layer.                                                 1022HT     UNDISTURBED SEAWATER           2.07

                   Undisturbed         corrosion         tests      were       con-             1022       CORROSIVE-WEAR                 161
                   ducted first to provide a baseline for                                                  (DISTILLED)
                   analysis of the corrosion resistance of
                   the      steels       and      its      effect        on      the            1622       CORROSIVE-WEAR                 240
                   corrosive-wear process.                  Identical spec-                                (SEAWATER)
                   imens of each steel were immersed in
                   distilled water and seawater for 120 and                                     1045       CORROSIVE-WEAR                 289
                   180 hours. Weight losses were calculated
                   for all specimens.                                                           4140       CORROSIVE-WEAR                 52

                   Following completion of the undisturbed                                      1022HT     CORROSIVE-WEAR                 73
                   corrosion tests, corrosive-wear tests were
                   performed using the 1022 steel in both
                   distilled water and seawater.                       The data             One of the objectives of Experiment A was
                   would provide insight into the effects of                                to determine the effects of the corrosive
                   the corrosive medium on wear.                      Corrosive-            medium on the corrosive-wear process.                           By
                   wear tests in seawater were performed on                                 comparing the results of the undisturbed
                   all the steels.               As with the corrosion                      tests with the corrosive-wear tests,
                   tests,       weight        loss measurements                 were        differences of one to two orders of
                   determined.                                                              magnitude occurs in the material loss
                                                                                            rates.         Wear was the dominant material
                   The      corrosive-wear             testing          apparatus           loss mechanism.              The results between the
                   presented a problem with the measurement                                 1022       steel         corrosive-wear           tests         in
                   of material weight loss.                          The steel              distilled water and seawater demonstrate
                   specimens had unequal abraded surfaces.                                  that the wear increases by 50% in a
                   Therefore, the applied pressures on the                                  corrosivemedium.
                   contact surfaces were inconsistent.                                A
                   material loss coefficient was calculated                                 wear rates are greatly effected by the
                   by dividing the specimen material loss by                                material properties of the steels.                             The
                   the abraded area to account for the                                      1045 steel had the highest material loss
                   difference in area.                                                      rates as shown in Table 2. This steel is

                                                                                       584

                  identical in composition to the 1022 steel                           The steels tested. in this experiment
                  with the exception of a higher carbon                                included the 1022, 4140, heat treated
                  content. Abrasion resistance improves with                           4140, 4340, and 8740 steels.                     With the
                  increased carbon content and hardness.                               exception of the common buoy chain steel,
                  However, with sufficient stresses, wear                              1022, all the other steels had similar
                  may occur through delamination of the                                carbon contents.            Heat treatment of the
                  carbide plates below the surface (3].                                4140 steel consisted of austenitizing at
                  Large amounts of material are removed by                             1600*F for one hour followed by slow
                  this process.             The martensitic micro-                     cooling over a 24-hour period, which
                  structure produced by heat treatment of                              produced a more ductile metal.                   The 8740
                  the 1022 steel resulted in improved wear                             and 4340 were selected due to their
                  resistance. The greater hardness produced                            increased nickel content.
                  by this microstructure resists abrasion
                  while       preventing           delamination            from        The corrosive-wear testing procedure was
                  occurring.         Alloy additions in the 4140                       similar to that used in Experiment A.
                  steel provided the lowest material                       loss        Weight measurements were taken prior to
                  rate.       The solid solution hardening of                          testing and following completion of the
                  this alloy is most effective in reducing                             testing.       The material loss measurements
                  abrasion.                                                            were graphed as a function of the test
                                                                                       durations.          The graphs showed initial
                                                                                       rapid material loss followed by reduced
                               3. LABORATORY TESTING:                                  steady state wear.                The slope of the
                                    EXPERIMENT B                                       curves in the steady state region, given
                                                                                       in Table 3, were obtained to compare the
                  The results of Experiment             A indicated that               corrosive-wear resistance of the steels.
                  the microstructure of the steel was the
                  most     important        factor in controlling
                  material        loss       in     a       corrosive-wear                                       TABLE 3
                  environment.         Several       different         micro-                MATERIAL LOSS RATES: EXPERIMENT B
                  structures were examined in Experiment B
                  to identify a better wear resistant
                  microstructure.                                                                     STEEL                  WEAR RATE

                  A new corrosive-wear testing apparatus was                                          1022                     0.46     mg/hr
                  designed for Experiment B due to problems
                  in the first experiment with uneven                                                 4140                     0.19
                  abraded surfaces. The apparatus, shown in
                  Figure 4, was designed to provide abrasion                                          4140HT                   1.42
                  across the entire surface of the steel
                  specimen.       Although the magnitude of the                                       4340                     0.10
                  load was less than that used in Experiment
                  A, the frequency of the loading was                                                 8740                     0.21
                  identical.
                                                                                       The material loss rates indicate that the
                                                                                       4340 steel had the best corrosive-wear
                                                                                       resistance, followed by the 4140, then the
                                               an                                      8740 steel. The 1022 steel was relatively
                                              Specimen Holder       Shaft              poor in comparison to the alloy steels,
                                            F- Abrasive Disk        Linear Bearing     except for the heat treated 4140 steel.
                                                                    Shaft Guide -      The controlling factor for the corrosive-
                                                                                       wear rate of steels with ferrite-pearlite
                                                                                       structures appeared to be the ferrite to
                                                                                       pearlite ratio.           Material loss decreased
                                                                                       with a decreasing ferrite to pearlite
                                                                                       ratio.       The control of this ratio by
                                                                                       suitable alloy selection, heat treatment,
                                                                                       and processing techniques would therefore
                                                            j                          seem to hold promise in improving buoy
                                                                                       chain wear resistance.

                                                                                       Due to the differences in the loading of
                                                                                       the specimens in Experiments A and B,
                                                                                       quantitative comparison of the material
                  FIGURE 4. Laboratory Testing Apparatus:                              loss rates are not possible. However, the
                                 Experiment B                                          relative corrosive-wear resistance were
                                                                                       consistent for the same steels tested in
                                                                                       both experiments.            Of greater importance
                                                                                       was whether the results could be verified
                                                                                       by field testing.

                                                                                585

                            4. FIELD TESTING                      bottom characteristics in the vicinity of
                                                                  the sinker are provided from the diver
              A two year buoy chain field test was                reports.   Percentage weight losses of the
              conducted using several of the alloy                complete chains are listed in the second
              steels examined in the laboratory tests             column.   In the third column the maximum
              [4].   The objective of the field testing           reduction in link diameter are listed as a
              was to determine whether the results of             percentage of the original measurement.
              the accelerated laboratory tests were               In all chains this occurred in the curved
              valid     for     long    term      exposures.      section of the links.           The relative
              Particularly    of   concern     was    pitting     pitting corrosion resistance    compared with
              corrosion of the alloy steels.          Pitting     the other chains are shown      in the fourth
              corrosion was determined to be a major              column.
              cause of failure of moorings in tests
              conducted by the Canadian Coast Guard [5].          By observation of the weight loss data it
                                                                  appears that it is largely influenced by
              The buoys were moored at a location                 the ocean f loor rather than the type of
              approximately     one     mile      south    of     chain.    Both steels exposed to a sandy
              Charlestown Breachway on the Rhode Island           floor lost the least weight while a rocky
              coast.    The location of the buoys was             floor resulted in maximum weight loss.
              selected for several reasons.        The most       Although general weight loss          is not
              important of these is that the    buoys could       critical to the strength of the mooring,
              be   monitored    at     frequent   intervals.      lower weight results in greater movement
              Secondly, the environment was semi-exposed          of the chafe section due to reduced
              with an average wave height      of 2.4 feet        damping in the riser section.
              and current of one knot.         Finally, the
              location provided a water depth of 35 feet          The link diameter measurements were the
              with a rough bottom consisting of rocks             most critical part of the data.             Re-
              and sand.                                           duction   in   link    cross    section    will
                                                                  eventually result in failure of the
              The five different steels selected for the          mooring. These measurements also have the
              mooring chains were the conventionally              highest potential for error as evidenced
              used 1022 plain carbon steel, and alloy             by the 8740 steel chain. The reduction in
              steels 4140, 4340, 8740, and 8620.         The      link diameter was much less than all the
              compositions of the steels are given in             other chains; however, the chain weight
              Table   1   along with their respective             loss was one of the highest. A reasonable
              hardness values.         The variations in          explanation    for   this    occurrence     was
              composition    were     primarily     chromium,     discovered    in   the     diver    inspection
              nickel, and molybdenum.       The 4340 steel        reports. The 8740 chain was found to be
              contained the highest total of these                tangled in rocks in both June and October
              alloying additions with the 8740, 8620,             1986.   Estimating the chain to have been
              then the. 4140 steels decreasing in alloy           tangled for at least six months, the
              additions.    Following the manufacture of          reduction in wear would be accounted for
              the alloy steel chains, tempering to a              by the lack of movement in the chafe
              hardness of less than Rc30 was conducted            section. The remainder of the chain would
              to avoid premature failure by stress                still experience wear on the hard rocky
              corrosion     cracking     in    the    marine      bottom which would explain the high
              environment.                                        overall weight loss.     The 8740 chain link
                                                                  diameter data was therefore considered to
              Prior to commencement of the testing in             be invalid.
              August 1985, the chains were weighed and
              link diameter measurements were recorded            A more practical method for evaluating the
              at two locations on each of ten links.              performance of the chains is to compare
              The moorings were inspected quarterly               the smallest link diameter measurements.
              during the testing to insure they were in           Using the weakest link data, the 4340
              good condition and that none were wrapped           steel performed better than all the other
              around their sinkers.        The buoys were         steels even though it was located on a
              subjected    to    several    severe    storms      mostly rocky bottom.       The typical buoy
              including Hurricane Gloria in September             chain steel, 1022, exhibited the worst
              1985.   The testing was concluded in July           performance.
              1987. The chains were reweighed and dia-
              meter measurements were taken on each link          A comparison of the 4140 steel with the
              in the chafe section at the same positions          1022 steel chain showed some unexpected
              on the links as had been previously                 results. Both chains were located in.sand
              recorded.     Visual examinations of       the      and from the laboratory testing the 4140
              chains were conducted.           Evidence of        steel should have greatly out-performed
              pitting or unusual wear was recorded.               the 1022 steel. However, there was little
                                                                  weight   loss    and    diameter     reduction
              The results of the buoy chain tests        are      difference between the two steels.            A
              shown in Table 4. In the first column      the      likely possible explanation for this re-

                                                               586

                                                           TABLE 4
                                         SUMMARY OF BUOY CHAIN FIELD TESTING DATA

                                                      Weight           Reduction in          Resistance
                    Steel         Floor Type          Loss             Diameter              to Pitting

                    1022          Sand                9.5              41.1                  Poor

                    4140          Sand                9.0              39.3                  Poor

                    4340          Sand+Rock           11.2             32.6                  Excellent

                    8740          Rock                12.5             Invalid data          Fair

                    8620          Sand                13.1             39.6                  Good

             sult is that interlink         wear was the        the    majority   of   the , material     loss.
             primary mechanism for material loss. Link          Additionally,    the     4340  steel     showed
             shape reflects this theory as the curved           superior performance in the comparison of
             section having considerably more material          maximum link reductions. Improved service
             loss on all chains than the other sections         life of chain moorings can be achieved
             of the link.       However, the 4340 steel         through the use of 4340 steel.      The steel
             showed only minor differences in wear              will be of maximum benefit in areas where
             along the curved section in comparison to          the conventional chain has been worn in
             the rest of the links.          Consequently,      relatively short periods of time.
             barrel wear was responsible for the
             majority of wear observed for this chain.
             Therefore, the results demonstrate that                           6. REFERENCES
             interlink wear is a much more damaging
             process than barrel wear. This conclusion          (1]  Dexter,      S.C.,      "Handbook       of
             is not only supported by the data but              Oceanographic  Engineering Materials,!' John
             observations as well.                              Wiley & Sons,  Inc., 1979.

                         5. CONCLUSIONS                         [2] Kohler,      C.A.     and   May,      D.A.,
                                                                "Corrosive-Wear of Buoy Chain," Interim
             From the data collected in    this study, the      Report, U.S. Coast Guard Report No. CG-D-
             best material to replace      the 1022 steel       21-86, July 1986.
             for buoy chain moorings       would be 4340
             steel chain tempered to       a hardness of        (3] Suh,     N.P.,     Jahanmir,      S.    and
             Rc28.   The accelerated laboratory testing         Abrahamson,  E.P., I'Delamination Theory of
             indicated a four to five fold decrease in          Wear," Progress Report to DARPA, Materials
             material loss.     The two year buoy f ield        Processing    Laboratory,    Department      of
             test proved the 4340 steel to have the             Mechanical Engineering,      MIT, Cambridge,
             best pitting resistance due to its high            MA, September 1974.
             nickel content.       From a weight loss
             perspective,     other    chains     performed     (4] Brown      R.    and     Kohler,     C.A.,
             better.   However, responsibility for the          "Corrosive-wear of Buoy Chain," Final
             majority of the weight loss was due to the         Report, U.S. Coast Guard,    in publication.
             rocky ocean floor.       The link diameter
             measurements were supporting evidence of           [5] Laing,     A.K.,     Buhr,   R.K.,      and
             the benefits of the steel.          The 4340       Gertsman, S.L., "Navigational Buoy Mooring
             exhibited the lowest average percentage            Chains," Technical Report by the Canadian
             reduction in diameter in the chafe section         Department of Mines and Technical Surveys,
             where interlink wear was responsible for           1965.

                                                           587

                                   COLLISION TOLERANT PILE STRUCTURES: DESIGN ANALYSIS SOFTWARE

                                     Marc Briere, Kenneth C. Baldwin, and M..Robinson Swift

                                Mechanical Engineering Department and Ocean Engineering Program
                                     University of New Hampshire, Durham, NH, 03824, U.S.A.

                                ABSTRACT
               A Collision Tolerant Pile Structure
               (CTPS) is a compliant, hinged structure
               designed to carry Aids to Navigation
               (ATON's) in shallow navigable shipping
               channels subject to heavy barge traffic.             ATON
               The project goal is to develop a software
               package to serve as a tool for full scale
               CTPS   design   based on site      specific
               conditions. The software runs on MS-DOS,
               is interactive and menu driven, and
               utilizes the LOTUS 123 spreadsheet.
                  The software includes recent design           MIDDLE BUOYANT SECTION
               improvements involving an improved spring
               configuration and the use of buoyancy and
               simulates CTPS dynamics during collision,
               storm and normal operating conditions.
               Typical model inputs include wave height,
               current velocity, water depth, and barge
               draft, speed, freeboard, and bow angle.
               Using site specific values in a generic
               model, based on Coast Guard
               specifications,   parametric  studies    are                              LOWER SPRING SECTION
              .readily performed.

                                                                   UPPER BASE

                                                                                            LOWER BASE
                             I.INTRODUCTION

               Background

                  The rigid pile structures currently in
               use for deploying aids to navigation
                                          channels     and
               (ATON ' s)  in   coastal                              WINGED FOUNDAT,
               intercoastal waterways are frequently
               destroyed by towed barges straying out of
               the main channel.    Replacement of these        Figure 1.   Central Stay CTPS system and
               structures is costly and their absence           component configuration.     Foam cladding
               from   the   waterway poses      both    an      can also be attached to the lower spring
               environmental and safety hazard.           A     section.
               possible solution to this problem is the
               replacement of existing rigid pile
               support by a compliant Collision Tolerant
               Pile Structure (CTPS) -    This compliant        section has a buoyant core and outer foam
               structure would maintain verticality             cladding while the lower section contains
               during normal operating conditions and           a spring assembly.      Upon impact the
               yet be able to "give way" to a colliding         structure rotates about the bell / base
               vessel.                                          pivot point allowing the barge to pass
                  The CTPS configuration consists of an         without seriously damaging the structure.
               ATON mounted upon a series of two pile           After the barge passes the spring /
               sections and a bell / base combination           buoyancy recovery mechanism acts to
               which   is   inserted    into   a winged,        restore the pile to an upright position.
               foundation (see Fig 1).    The middle pile         The objective of   this present work is
                                                                                0, Tr@

                                              CH2585-8/88/0000- 588 $1 @1988 IEEE

                to develop software to serve as a tool in                     the central stay system is a clear
                analyzing and designing a full scale CTPS                     advantage over that of the peripheral
                for    site     specific      conditions.          The        stay.
                software allows the designer to perform                          The success of the 1/15 scale, central
                parametric        studies to determine the                    stay physical model prompted efforts to
                effect of the design parameters on the                        design, build and test a 1/4 scale (10
                structure's performance.              The program             ft.). central stay physical model.                The
                requests       environmental           inputs      and        encouraging results of the investigation
                provides the user with information on how                     are described in Swift et al. (1986).
                CTPS dynamics are modified due to design                      Baldwin et al. (1987) summarized all the
                parameter changes.             Utilizing a menu               1/4 scale results and confirmed that the
                driven structure the user is                      also        central stay hinge concept is indeed a
                provided        the      option      of      viewing          viable       design     alternative         to    the
                intermediate calculations              (ie.    hinge,         peripheral stay configuration.             The next
                gravitational, and buoyancy moments vs.                       step, therefore, is to design, build and
                pile inclination).                                            test a full-scale structure utilizing the
                                                                              central stay concept.

                Review of previous work

                    The initial development of the CTPS                              II. PRESENT FULL SCALE DESIGN
                concept was performed by Swift and
                Baldwin (1985). Their efforts were                            Hinge  Concept
                directed toward developing analytical
                tools for evaluating design concepts,                            The present full scale hinge concept
                choosing the best            hinge concept         for        is based on the 1/4 scale, central stay
                further study,           and constructing and                 physical model.         However, the increased
                testing a 1/15 scale (2 1/2 ft.) physical                     inertial       and    gravitational           forces
                model.      Using a mathematical model and                    resulting      from scaling considerations
                design criteria specified by the                              place. higher demands on the spring
                Coast      Guard,        S w i f t  and      Baldwin          mechanism. The existing 1/4 scale spring
                (1985,1986)       identified two potentially                  design is incapable of sustaining the
                successful hinge concepts - a central                         increased      loading      requirement.          The
                universal         joint,      peripheral         stay         investigation of a new spring design is
                arrangement and a central stay system.                        described in Ward et al. (1988).                  The
                The peripheral stay concept received                          results of this investigation indicate
                initial emphasis and its development has                      that a compressive rather than a tensile.
                been reported by Swift and Baldwin                            spring       is    best     suited       for      the
                (1985,1986), Cloutier et al. (1985),                          application.
                Durkee (1986) and Mielke (1986).                                 The new spring design consists
                Subsequently, however, the central stay                       primarily of         three compression coil
                arrangement was developed as a design                         springs connected in series by couplings
                alternative.                                                  and a termination plate on top (see Fig.
                                                                              1). A chain running through the centers
                   The major components of the central                        of    the    springs    is   connected to         the
                stay system,    as described in Swift et al.                  foundation as well as the termination
                (1986), include the base, the bell, the                       plate.     In addition to this change in
                central stay attached to a pre-stressed                       spring design, buoyancy is added via a
                tensile spring, and the hollow pile.               As         foam core and foam cladding to increase
                the pile tips,          it pivots about the                   the restoring moment aiding in the
                bell/base contact point, while the stay                       recovery process. Thus, as the pile tips
                and buoyancy forces provide the restoring                     the spring mechanism is enabled and the
                moment.                                                       buoyant section submerged creating a
                   The   development of the central stay                      restoring moment about the bell/base
                system began during the 1985-1986                             pivot.
                academic year when a senior student                              There are a number of advantages in
                design    team embarked on the design,                        u s i n g   t h i s     n e w     compression
                construction and testing of a 1/15 scale                      spring/buoyancy recovery mechanism. To
                physical model.        Their objective was to                 begin, the pile no longer acts as a
                determine the bell/base geometry which                        compression member thereby significantly
                would minimize the possibility of jamming                     reducing the possibility of buckling.
                while maintaining the stay moment arm                         Secondly, the configuration of this new
                with respect to the contact point. Their                      spring mechanism places its center of
                results showed the central stay concept                       gravity closer to the hinge which reduces
                to be successful and thus a viable                            the gravitational moment produced by the
                alternative to the peripheral                    stay         spring weight.       Since the springs are in
                arrangement.      In fact, the removal of                     compression the possibility of over
                friction during the recovery process of                       extension failure is eliminated.                    In.

                                                                        589

              addition, the buoyancy reduces the
              requirements on the spring by acting to                                                   Rb
              offset the gravitational moment.

                      III. MATHEMATICAL MODELING

                  The modeling approach used is similar
              to that found in Swift and Baldwin
              (1986).   The CTPS system is considered a
              rigid pile - flexible hinge system where                                Ly@ Fs
              the hinge is omnidirectional, possessing
              a restoring moment stiffness via the                     A
              spring mechanism described above.           In        HC
              keeping with the worst case approximation
              the directions of the wind, wave, current
              and barge motion are assumed collinear.                                                    Hb
              In addition, all loadings and resulting
              motions are restricted to the vertical                                     RC
              plane.
                  The governing system dynamic equation
              is the time rate of change of angular
              momentum equation applied at the "fixed"           Figure 2.      Central  stay hinge concept
              bell-base pivot point,                             showing    pertinent      parameters      for
                              IH 6 = I MO         (1)            determination of hinge moment (MH).

              where IH = moment of inertia about the
              pivot point 0, e = angle of pile with
              respect to the vertical, ( .. ) indicates
              two time derivatives with respect to time
              t, and  ?10 refers to moments applied about
              the pivot 0.         Depending upon the
              application the      applied moments may
              include the effects due to the hinge                                ye
              stiffness, buoyancy, gravity, wind,
              relative fluid motion and barge contact.                                  61    G      D
                  The hinge moment, MH, created by the
              central spring has the form
                  MH = -FS(RCcos0L+ HCsin-w.)sgne        (2)                                WT

              where FS = spring force, and RC and HC
              are the cone radius and cone          height,
              respectively, as shown in Fig. 2.       The
              (-) sign and sgnG are in accordance with                                    R91
              the sign convention used to indicate that                                r
              the hinge moment always acts to restore                             @b/      R 82
              the pile to vertical.
                  The upsetting gravitational moment,
              MG, due to the "dry" weight of the CTPS
              is given as
                                                                 Figure 3.      Central stay CTPS dynamic
                  MG   (yGsinesgne - RBcOs@)WTsgnO       (3)     modeling nomenclature.
              where YG and RB are shown in Fig. 3 and
              WT  is the total CTPS weight.                         The moment, MW, acting on the pile as
                  The buoyancy moment, MB, resulting             a result of (steady) wind is given in the
              .from fluid displacement has the form              form

                  MB = -62.4(RBlVSI + RB2VS2)sgne        (4)           MW = FW @D + 0.5 (LT-LS)COSOI       (5)
              where RB 1 and RB2 are shown in Fig. 3 and         where FW = the applied wind force and the
              VC1   and VS2 represent the submerged              term  in brackets represents the moment
              v@fumes of the lower and middle pile               arm (see Fig. 4). The wind force, FW, is
              sections, respectively.       The volume of        approximated using a drag force approach
              the ATON is small and it's buoyancy                and can be written as
              effect was neglected.
                                                                                      LY,
                                                                                                   @H,

                                                             590

                FW = 0.5 TaCaUa 2 f DO(LT-LS)cosG     (6)     collision sequences the barge speed is
                                                              unaltered and assumed constant. Assuming
            where          C     and U    represent the       that the barge-pile contact is maintained
                      3 at   at        a                      throughout the collision process allows
            density of air, drag coefficient of pile          the    pile   motion    to    be   analyzed
            in air and air velocity, respectively,            independently of the forces        involved.
            and the bracketed term f     ... I indicates
            the projected CTPS area exposed to the            Thus, the solution to Eqn. (1) is found
            wind.                                             via the barge-pile kinematics.     Eqn. (1)
                                                              is solved numerically, however,    in those
                                                              cases where the kinematics do not fully
                                                              define the motion.       In these cases a
                        FV                                    Fourth    Order Runge-Kutta       numerical
                                                 (Ly AS  casS integration    technique   I s implemented.
                                                              Both of     these techniques are fully
                                                              developed in Swift and Baldwin (1986).

                                                                          III. DESIGN SOFTWARE

                    GIONMT AMC
                  0+ 1/2(L-r-4)c*s8                           Purpose
                                e                  D              The purpose of the software is to
                                                              provide the user with a structured and
                                                              easy to use design tool for developing a
                                                              site specific CTPS. The goal is to allow
                                                              various CTPS configurations to be easily
                                                              generated and their performance studied
                                                              and compared, giving the user the ability
                                                              to conveniently investigate a number of
                            01                                design alternatives and examine their
                                                              limits.

                                                              Description
            Figure 4.     Diagram showing the location
            of the resultant wind drag force for the              A number of conditions are placed on
            CTPS.                                             the type of software used in developing
               The moment      load induced 'by the           the design program.    It is required that
            relative water movementr MCr is evaluated         the software used have the ability to
            using a form of Morrison's equation               easily    access   tables     of  pertinent
                                                              information,    be menu driven,         have
                         MC @ MD + MI'                (7)     graphics    capabilities,     and perform
                                                              iterative calculations.        To do this
            where MD and MI' represent the drag and           LOTUS 123, a spreadsheet software package
            inertial moment loads, respectively.              with these capabilities, is employed.
            These moments are evaluated using linear              The design program      (worksheet)    is
            wave theory and a relative velocity and           completely menu driven containing several
            relative acceleration normal to the pile.         menu levels (see Fig. 5).      Each of the
            Note that MI I is that part of the total          entries in a menu, called menu items, are
            inertial forcing moment remaining after           used to describe a type of operation. To
            the   "added  inertia effect"     has   been      select an item the user can either type
            removed.     The added mass itself is             the first character of the item desired
            incorporated into the mass moment of              or, using the arrow keys, position the
            inertia about the hinge pivot.       A more       highlight over the item and press RETURN.
            detailed description and full development             The main menu categorizes the program
            of this approach can be found in                  operations into three basic types:
            Medzorian et al. (1988).                          Documentation (description), Analysis
                                                              (dynamic and static), and output (screen
               The   applied barge moment,           MA,      viewing  and printing)     The lower level
            resulting from the barge contact force
            during a collision is given in the form           menus are Invoked by a higher menu
                                                              selection and are more specific than the
                                                              higher levels.     They provide the user
                        MA = FALCsin9C               (8)      with the flexibility to "pick and choose"
            where FA = applied barge contact force,           the precise operation desired.           For
            LC = distance from hinge pivot to point           example, if the user is interested in the
            of contact and OC = angle between pile
            direction and direction of barge force.
               The approach to solving Eqn. (1) also
            varies with the application.    During   the

                                                         591

                   impulse loadings occurring during the                 performed by inputting parameter ranges
                   upper and lower bow impacts he/she need               instead 'of single values.       These studies
                   not evaluate the entire collision.            By      can be done on the system dynamics
                   selecting Dynamics (D)       Collision (C) /          (collision,      recovery,      storm)   or the
                   Impact (I)   (see Fig. 5)    the user obtains         static moments. This item, (S), is still
                   the evaluation of the        impact dynamics          under development.
                   only.                                                    The output is easily         obtained using
                                                                         the menu items View (V)         and Print (P) .
                   f-INTRODWT100 DYNAMICS MOMENTS STUDY view PROT QUITI  View (V) allows the user        to inspect any
                   - I                                                   output resulting from a         design session
                   Ma. Print                                             while Print (P) allows          formatted hard
                   ISterm CoLlWan Recovezy-ExTtl                         copies of the output.      The output formats
                          I                           I     i            include graphs, the             corresponding
                      11mact All --Bxl-ti  Warta Data Graph EX10         numerical      data,  input     tables,    output
                                                                         tables, and the CTPS configuration.           All
                   Iftige gravity nuoyawy Restaging                      of the output, except graphs,           is sent
                             Hil                                         directly to a printer using Print (P). A
                                                                         hardcopy of the graphical data is
                   Istorm C01118ken Rocovety ramnts Impact exit          obtained without leaving the worksheet by
                                                                         first viewing the graph and using the
                             Storm CoIlLsion R*-cmerv Koments lim        "Print    Screen"    keys   on  the    keyboard.
                         [XnPuts StQ= C01irs-lon- ftcovecy into Parts Exiti Note, however, that the graphical output
                                                                         produced during a design session is also
                                                                         saved and is available through the LOTUS
                   Figure 5.       Diagram showing the menu              graphics printing program (PrintGraph).
                   structure. The menu item "Exit" returns               Application
                   the user    to the previous menu.          The
                   "Study" item is still in the development                 Two scenarios are presented to show
                   stage.                                                the    usefulness      of   the   software      in
                      Once inside the worksheet the user is              performing parametric studies. The first
                   allowed to go up and down the menu                    considers the effect of spring stiffness
                   structure by selecting the proper menu                degradation while the second considers
                   items.   To go from a lower level to the              the effects of buoyancy loss.
                   next highest level the user selects Exit                 Spring stiffness degradation over time
                   (E).   Only if the user selects Quit (Q)              is expected due to cyclic loading and
                   when in the main menu will the program                corrosion.      This directly effects the
                   terminate. Upon completion of a selected              hinge moment as well as the overall
                   operation  the program returns to the menu            restoring moment.        The effects of this
                   where the operation resides.         I The user       reduction in the central spring stiffness
                   then has   the choice of performing that              on the hinge moment, overall restoring
                   operation again or going to another                   moment and dynamic response during a
                   operation somewhere else in the menu                  recovery process are easily evaluated by
                   structure.                                            varying     the    parameter      K      (spring
                      A general description of the program               constant)      from   100%    to  7 @%  of    its
                   and its use is contained in the worksheet             original value. Figures 6, 7, and 8 show
                   and can be viewed or printed.          To view        the output obtained and indicate that the
                   this information on the screen the user               hinge and restoring moments are sensitive
                   selects Intro (I)/ View (V) .           A hard        to the parameter change and the pile
                   copy is obtained by selecting Intro (1)               recovery response is not.
                   Print (P).                                               The outer foam cladding is subjected
                      The analysis performed by the program              to harsh conditions and is considered
                   is   divided     into    three categories:            sacrificial.      This effects the buoyancy
                   Dynamics,    Moments,     and     (parametric)        moment and the overall restoring moment,
                   Studies, and are represented as Dynamics              but, again the effect on the recovery
                   (D),   Moments     (M),    and Study       (S),       dynamics is marginal.         The results are
                   respectively, in the main menu.              The      shown in Figures 9, 10, and 11.               The
                   Dynamics (D) item allows the dynamics of              static moments are directly affected by
                   the Collision / Recovery sequences and                the   loss of      foam but the recovery
                   CTPS under Storm conditions to be                     response varied little.
                   investi gated.      The Moments      (M)   item          The previous results indicate that the
                   allows any of the static moments about                recovery dynamics are little effected by
                   the hinge or the spring force to be                   the individual changes in both spring
                   evaluated     as    a   function     of    pile       stiffness and buoyancy.            A recovery
                   inclination.     The@selection Moments (M)            simulation using both a reduced stiffness
                   / All (A) evaluates all of the moments                (70%) and no outer foam indicates that
                   and combines the results             for each         the combined effect results in a recovery
                   individual moment on one graph. The item              time increase of about 4 seconds, or
                   Study.(S) allows parametric studies to be             increase of about 25% (see Fig. 12).

                                                                    592

                                    HINGE MOMENT VS PILE INCLINATION                                                                    BUOYANCY MOMENT VS PILE INCLINATION

                                                                                                                                        am -

                                                                                                                                        ?a-
                                 'M
                                                                                                                                        do-

                                 do-
                                                                                                                                        so

                                                                                                                                        30-

                                                                                                                                        20

                                                                                                                                        to-
                                 30-

                                                                                             0a                                         a            20                                             00
                                 a            20

                      10-100S              +    KS - 9=             0   Ks   WX                  ks - MX                     ?ht - 3 W.                 + Tht    1.5 W.                   0   Tht  0.0 1..

                   Figure 6.                  Curves showing the effects of
                    spring stiffness degradation on the hinge                                                           Figure 9.                 Curves showing the effects of
                   moment (MH).                                                                                         exterior foam loss on the buoyancy moment
                                                                                                                         (MB)-

                                  RESTORING MOMENT VS PILE INCLINATION
                                                                                                                                        RESTORING MOMENT VS PILE INCLINATION

                                                                                                                                        70

                                                                                                                                        60

                                 23-                                                                                                    40

                                 W
                                                                                                                                        30-
                                 j30                          4@                                                                        zo
                      KS - 10019                                   0")                                                                  0
                                                KS - 9=              9   KS - aDX             A   KS   71119                                                                         W               so
                                                                                                                               W - 3 W                   +   Thr  1.3 K                        Tht  0.0 itt.
                      Figure 7.                 Curves showing the effects of
                      spring stiffness degradation, on the                                                                Figure 10.                     Curves showing the effects
                      restoring moment (MR).                                                                              of exterior foam loss on the restoring
                                              PILE INCLINATION VS. TIME                                                   moment (MR).
                                                                                                                                                     PILE INCLINATION VS. TIME
                                                                                                                                                                       O@2
                                 70-                                                                                                    am @

                                 W -                                                                                                    70-

                                 ao -                                                                                                   Go.

                                                                                                                                        W.

                                 30-

                                                                                                                                        20-

                                 a         4          a         12
                                                             TIM (MC)                                                                   _20
                      KS -       100X       t    Ks   gwg            0   Its - a0X            A   KS   It=                                                                        Is         2@
                                                                                                                               Tht - 3 bo.                              (SM)
                                                                                                                                                                    5 W                     0 Tht    0.0 W
                      Figure        8.         Curves showing the effects of
                      spring stiffness degradation on pile                                                                Figure          11.            Curves showing                    the effects
                      recovery behavior..                                                                                 of exterior foam loss on pile recovery
                                                                                                                          behavior.

                                                                                                               593

                            PILE INCLINATION VS. TIME
                     00                                           Swift, M.R. and K.C. BAldwin (1986) "The
                                                                     Development of a Collision Tolerant
                     70-                                             Pile Structure Concept", Ocean         -
                     0.                                              Engineering, Vol. 13, No. 2, pp. 131-
                                                                     156.
                                                                  Swift, M.R., A. Dudka, R. Villeneuve, J.
                                                                     Ward and K.C. Baldwin (1986)
                     30                                              "Development of a Central Stay
                     20                                              Collision Tolerant Pile Structure". a
                     10                                              UNH CTPS group technical memorandum
                     a                                               submitted to the U.S. Coast Guard,
                                                                     2100 2nd St. SW, Washington, D.C.
                                                                     02593.
                                                                  Baldwin, K.C., M.R. Swift and D. Mielke,
                     -30                                             (1987), "Quarter Scale Collision
                                    Tal(WI                           Tolerant Pile Concepts: Peripheral and
                                 KS 70X M W - 0 1.                   Central Stay", OCEANS 87
                                                                  Swift,M.R. and K.C. Baldwin (1988).
                Figure   12.      Curve showing the pile             "Collision Tolerant Pile Structure
                recovery response with a 30% decrease in             Hinge Concepts". ASCE Technical Note,
                spring stiffness and total loss of                   in press.
                exterior foam.                                    Ward, J.S., K.C. Baldwin and M.R. Swift
                                                                     (1988), "The Design and Analysis of a
                                                                     Full Scale Prototype Collision
                Summary    Conclusion                                Tolerant Pile Structure", Submitted to
                                                                     ASME Ocean Engineering Division, 4th
                     The CTPS design software presented              Annual Symposium on Current Practices
                here is a multi- functional package which            and    New    Technology      in   Ocean
                provides the user with a flexible design             Engineering.
                tool.   All of the modeling and analysis          Medzorian,J., M.R. Swift, J.S. Ward and
                is self-contained in a single worksheet              K.C. Baldwin (1988),       "Microcomputer
                eliminating the       need to     exit    the        Modeling of Collision Tolerant Pile
                worksheet to perform multiple design                 Structures Dynamics", Sea Grant report
                tasks.    All pertinent system parameters            number      UNH-MP-T/DR-SG-88-3          , -
                are allowed to vary enabling the user to             University of New Hampshire, Durham,
                alter the configuration during the design            NH, 03824.
                session.     The user is also able to view
                or obtain hard copies of the output
                without terminating the program.

                References

                Swift, M. R. and Baldwin, K. C.     (1985).
                  "The design and model testing    of a
                     collision tolerant pile structure",
                     Final report submitted to the U.S.
                     Coast Guard R&D Center, Avery Point,
                     Groton, CT.
                Cloutier,   R., T. Bier, C. Byrne, T.
                     Sears, and C. Tuttle (1985) "The
                     Design, Development, and Testing of a
                     Quarter Scale Collision Tolerant Pile
                     Structure", Tech 697 Sea Grant Ocean
                     Projects Course, University of New
                     Hampshire Mechanical Engineering
                     Department, Durham, NH.
                Durkee, R. A.    (1986)  "A Mathematical
                     Model for   the Three-Dimensional
                     Dynamics of a Collision Tolerant Pile
                     Structure", M.S. Thesis, Mechanical
                     Engineering, UNH, Durham, NH 03824.

                                                              594

                                     UNITED STATES NAVAL EXPERIENCE WITH ANTIFOULING PAINTS

                                                                    Theodore Dowd

                                                             Naval Sea Systems Command
                                             Materials and Assurance Engineering Office - Code 05M1
                                                             Washington, DC 20362-5101

                                      ABSTRACT                                from June 1981 to September 1987. In both cases
                                                                              the ships did not require any underwater brushin;
              Performance of several antifouling tributyltin                  in the 6 years that the organotin was on the hull.
              (TBT) paints on a variety of Naval ship types is                Other examples of outstanding long service, where
              presented. The current Naval assessment of TBT                  organotin is still performing, are a submarine
              paints is presented in terms of economic, environ-              painted in 1982, and an aircraft carrier painted
              mental, and health and safety issues. The                       in 1984. Organotin paints were applied on assorted
              alternate ablative paints tested have given mixed               combatants and auxiliary ships up to the end of
              results, but acceptable economic and environmental              1985, just before the ban went into effect, and
              results. Future antifouling paint needs and                     these ships are continuing to perform well.
              directions are discussed.
                                                                              A complete list of the ships painted with organo-
                                                                              tin and their length of service is contained in
                                                                              Table 1.
                   UNITED STATES' NAVAL EXPERIENCE WITH ADVANCED
                                ANTIFOULING PAINTS                                                    Table 1.
              Extended drydocking intervals and foul-free ser-                            COPOLYMER ORGANOTIN   TEST SHIPS
              vice of up to 7 years became a reality for the                                              DATE             LENGTH OF
              marine industry with the introduction of ablative               SHIP TYPE                 PAINTED             SERVICE
              organotin antifouling paints. These coatings
              resulted in reduced propulsion fuel costs up to                 Coast Guard Cutter      Feb  1979           7 Years
              16 percent, completely eliminated the expense of                Destroyer               Nov  1980           6 Years
              underwater scrubbing, and halted the ensuing                    Destroyer               Jun  1981           6 Years*
              damage suffered by the paint from the mechanical                Submarine               Jan  1982           Still Active
              process which further increased the savings. This               Aircraft Carrier        Apr  1984           Still Active
              is an outstanding achievement because,.at 201knots,             Frigate                 Jul  1984           Still Active
              a fouled ship may require 19 percent more horse-                Frigate                 Jan  1985           Still Active
              power to maintain its speed.                                    Aircraft Carrier        Feb  1985           Still Active
              The ablative organotin copolymer paints replaced                Supply Ship             Mar  1985           Still Active
              the old conventional cuprous oxide paints, which                Tug                     Sep  1985           Still Active
              are good for only 18 to 24 months, and are no                   Destroyer               Dec  1985           Still Active
              longer able to meet the increasing demands of the               Frigate                 Feb  1987           Still Active
              commercial marine industry and combat naval forces.             Frigate                 Sep  1987           Still Active
                                                                              Frigate                 Sep  1987           Still Active
              Ablative copolymer-type organotin paints were first             *This ship has an ablative organotin,       while all
              introduced in Europe in 1974 on commercial ships.                the others have the copolymer.
              By 1978, the news of its superior performance had
              become well-publicized in the United States, and                However, this superior antifouling coating       has come
              led to the application, in February 1979, on a                  under fire from environmentalists and labor unions
              U. S. Coast Guard cutter. This ship performed                   as being dangerous to man and marine life. In
              foul-free for the next 7 years. At the interim                  1986, the U. S. Congress imposed a ban on the use
              dockings in 1980, 1983, the ship was water washed               of organotin for Navy ships only. This is unfor-
              to remove the slimej mechanically damaged areas                 tunate because there are no alternatives that match
              were touched up, and the ship was returned to the               the performance of organotin paints.        Organotin
              water. The coating continued to perform well until              paints are legally used worldwide on 70 percent to
              1986.                                                           go percent of the major commercial ocean-going
              In November 1980, a U. S. Navy destroyer was                    ships-including the naval forces of many countries.
              painted with organotin and that ship performed
              foul-free until June 1986; another destroyer went

                                                                          595 United States Government work not protected by copyright

                 The Navy Environmental Assessment report claimed                                     TABLE 2.
                 that organotin can be safely used without danger
                 to marine life if the water quality standard did                           ABLATIVE  COPPER TEST SHIPS
                 not exceed 50 parts per trillion of tributyltin.                                   SOURCE #1
                 However, the Environmental Protection Agency (EPA)
                 recently recommended a 10 parts per trillion con-                             DATE       LENGTH OF
                 centration in the water. This is going to be very             SHIP TYPE      PAINTED      SERVICE          RESULTS
                 difficult, if not impossible, to meet, due to the
                 existing background levels in busy harbors or re-             Frigate        Aug  1983   48 Months      15% Fouling
                 pair areas, and because drydock discharges could              Ordnance       Apr  1984   36 Months      70% Fouling
                 be more than one order of magnitude higher.                   Supply         Apr  1984   35 Months       1% Fouling
                                                                               Carrier        May  1984   46 Months       0% Fouling
                 The other impediment to organotin implementation              Frigate        May  1984   40 Months       5% Fouling
                 is the cost of application in naval facilities                supply         Jan  1985   Still Active    0% Fouling
                 'Where increased concerns have escalated recent               Carrier        Mar  1985   12 Months      100% Delami-
                 costs. Costs at navy facilities can run over                                                                  nation
                 $100 per square foot to remove and reapply organo-                           Jul  1986, paint removed/reapplied
                 tin, while a commercial shipyard may charge $15 per           Carrier        Mar  1985   24 Months       0% Fouling
                 square foot for the same job. The main cost dif-                             May  1987, docked  and repainted
                 ference could be the result of different interpre-            Auxiliary      May  1985   Still  Active
                 tations of environmental and health requirements.             Destroyer      Jul  1985   Still  Active
                                                                               Assault        Aug  1985   Still  Active
                 As early as 1982, the U. S. Navy had reservat    ions         Cruiser        Sep  1985   Still  Active
                 on the ultimate use of organotin paints, based on             Destroyer      Oct  1985   Still  Active
                 the lack of environmental regulatory inputs. This             Supply         Oct  1985   Still  Active
                 apprehension led to Navy testing of ablative                  Carrier        May  1986   Still  Active
                 copper paints as an alternative, with the first               Carrier        Jul  1986   (Repair of 3/85 failure,
                 ship being painted in 1983. This was the first                                           Still Active)
                 ship test of this paint in the world.                         Destroyer      Sep  1986   Still Active
                                                                               Oiler          Nov  1986   Still  Active
                 In 1987, the Navy resorted to the fleetwide imple-
                 mentation of the ablative copper antifouling                               ABLATIVE COPPER TEST SHIPS
               ,system because organotin paints were no longer a                                     SOURCE #2
                 viable option. This paint is similar to Formula
                 121, but employs self-cleaning properties to renew            Assault        Mar 1986    Still Active
                 its surface. The system was originally advertised             Oiler          Apr 1986    Still Active
                 by the manufacturer to give a minimum of 5 years              Carrier        Sep 1986    Still Active
                 service and be the alternative to organotin                   Carrier        Nov 1986    Still Active
                 copolymer paints.

                 The history of that experience includes applica-              It is too early to report any long-range results
                 tions on submarines, and combatant and noncombat-             of test ships painted in 1985 to 1986, but in one
                 ant surface ships from 1983 to the present. In                case, the paint became powdery after only 13 months
                 August 1983, ablative copper was first applied to             service. This paint had to be removed and
                 a frigate. That ship was inspected 48 months                  replaced, and had it not been discovered, a mas-
                 later, in September 1987, and found to have about             sive paint failure and heavy fouling was
                 15.percent fouling. An ammunition ship painted in             anticipated.
                 April 1984 was found to have 70 percent heavy
                 fouling after only 36 months service. During                  At best, the present version of ablative copper is
                 1984, ablative copper was also applied to                     an improvement over F121, but no match for the
                 2 frigates, I aircraft carrier, and an auxiliary              superior 7-year performance of organotins. One of
                 supply ship; they are performing well, with little            the Navy suppliers has reformulated his ablative
                 or no fouling, after 4 years. This illustrates                copper product line in an attempt to approach the
                 that the ablative copper system is unreliabile and            performance of organotin. This new material has
                 not the equal alternative that the U. S. Navy is              been applied to a combatant surface ship, and its
                 seeking in place of organotin paints.                         performance will be monitored and compared with
                                                                               that of the existing systems serving as controls
                 The complete list of ships coated with ablative               on the same ship.
                 copper, from 1983 until 1986, is shown in Table      2.
                                                                               In addition, the quest for radically new and
                                                                               superior antifouling paints continues. There is
                                                                               a program to develop and test fouling-resistant
                                                                               paints which do not use any toxicants, but rely on
                                                                               the structure of the polymer to repel the attach-
                                                                               ment of marine organisms. Along this line, a new
                                                                               rubber-based material that has no toxicant, but
                                                                               nevertheless is able to repel the attachment of
                                                                               marine fouling is being.tested on ships following

                                                                           596

              2 years of laboratory testing. The material can be
              used on both steel and aluminum hulls, as well as
              rubber surfaces. It also has the potential for use
              in areas that require resistance to heat and ultra-
              violet rays.

              This is all a part of the continual investigation
              for new and improved antifouling systems that can
              best serve the maritime industry without endanger-
              ing the marine environment or mankind. The U. S.
              Navy places its reliance on the private sector to
              develop a long-lived antifouling paint system.

                                                                 597

                                               TAPERED INTERFACE IN HARSH ENVIROWENT CONNECTORS

                                                                   ALAN BERTAUX

                                                            JUPITER ELECTRONICS INC.

                                                                                      - Reduced visibility;
                      The mission of standard commercial, or                          - Temperature extremes;
                      even military electronic connectors is                          - Radiation.
                      typically to join 2 or more electrical
                      conductors     with   a     minimum     of                   Yet, a connector operating in such
                      interference   to current flow, within                       environments should, in addition to
                      the minimum amount of space and cost,                        meeting above constraints:
                      maximum    reliability    and   ease    of                      - Present as little signal loss as
                      operation for the task at hand.                                   possible;
                                                                                      - Be capable of handling        power,
                      Connectors made to operate in high                                signal and coax circuits;
                      fluid pressures or corrosive environ-,
                      ments    face additional      requirements                      - Allow   for fast and zero-force
                      which    translate into "trade        offs"                  mating and unmating (since the environ-
                      (price vs. reliability, size vs. ease                        ment   is often dangerous to         human
                      of operation,etc.).                                          beings):
                                                                                        Have unmistakable mating, in spite
                      A     conical interface    represents     a                  of poor visibility or uncomfortable
                      significant breakthrough in terms of                         situations;
                      performance,     cost,    and   ease    of                      - Have positive and secure connec-
                      operation.                                                   tion, to resist shocks, vibrations and
                                                                                   rough handling;
                                                                                      - Offer a wide range of shell and
                                                                                   insert combinations,     including high
                                                                                   contact densities;
                      Harsh environments, such as found in                            - Be   field   installable,     without
                      the oil, nuclear, mining, chemical or                        requiring cumbersome neoprene molding
                      naval industries dictate demanding con-                      equipment.
                      nector specifications not found in the                          - Have a knurled and circular shape
                      office   environment.       Traditionally,                   to enable easy handling even          with
                      designers have used military cylindri-                       gloves;
                      cal connectors to meet the demand of                            - Be cost effective.
                      these industries.    Unfortunately, such
                      connectors have inherent design and                          All  above design parameters can be
                      performance limitations, particularly                        satisfied,, in part, by the choice of
                      in the area of mating Interface. The                         connector raw materials.    Housings can
                      Purpose of this paper is to demonstrate                      be made of stainless steel, marine
                      the advantages of conical (or tapered)                       bronze or nickel plated brass; inserts
                      interfaces as applied to harsh environ-                      can be made of neoprene, Nylatron,
                      ment applications.                                           Tefzel, or vespel; and contacts can be
                                                                                   gold plated.
                      A harsh environment typically includes
                      one or more of the following con-                            In addition to offering various raw
                      straints:                                                    material or plating options, military
                         -  High humidity;                                         connectors have long offered keying,
                         -  Corrosive liquids or atmosphere,                       polarization and knurled cylindrical
                            including salt water;                                  bodies to enable easy and fool-proof
                         -  Dirt and dust;                                         mating.   Moreover, some of the newer
                         -  Fluid or gas pressure;                                 military connector developments also
                         -  Severe  shocks    or     vibrations,                   Provide for good resistance to shock
                            including human abuse;                                 and vibrations (example:     MIL-C-38999
                                                                                   Series III).

                                                      CH2585-8/88/0000-598 $1 @1988 IEEE

                     However,   even    with    military-class                    In addition, even the best 0 ring mate-
                     circular connectors, there is a limit                        rials can dry out or harden because of
                     as to how Much humidity or           water                   age, chemicals, or cold temperature.
                     pressure can be tolerated. in fact, by                       They then become brittle and fail.
                     design,   there    are   some    inherent
                     mechanical conflicts related to water-                       Another compromise is the use of a
                     tightness in standard military circular                      molded-on "rubber boot" wherever high
                     connectors.    Tightening the tolerances                     fluid   pressures are present.         The
                     that exist between two mating cylindri-                      cables are prepared and terminated in a
                     cal   connector surfaces results        in                   shop, and a rubber-like material (often
                     better waterproofinq.      However,    the                   neoprene) is molded over the connec-
                     tighter these tolerances are, the more                       tion.
                     difficult it is to mate and unmate the
                     connector halves.      Both the      metal                   Unfortunately,   there are several draw-
                     friction and the air pocket in the                           backs to this approach besides high
                     interface   area    must   be    overcome                    cost. Field repair is generally impos-
                     (Figure 1).                                                  sible.   Also,    if the connector is
                                                                                  damaged, it has to be cut from the
                     rip. I                                                       cable.   If not enough cable remains to
                                                                                  join the connector halves that have
                                                                                  been   substituted    for the      severed
                                                                                  connector, an entire harness has to be
                                                                                  replaced.    Furthermore, a molded-on
                                                                                  boot only guarantees hermeticity if the
                                                      plull                       joined cables remain straight.     Past a
                                                                                  given cable curvature, fluids may be
                                                                                  allowed to seep through the open sDace
                                                                                  created   between the cable and the
                                                                                  molded boot.      In   short,     standard
                     Hence, the tighter the hermeticity, the                      circular   military    connectors     were
                     harder it is for the air to be squeezed                      designed for specific purposes that may
                     out.    Conversely,    the unmating, of                      not    meet   some    harsh     commercial
                     tightly mated cylindrical connectors                         environments. A connector with conical
                     requires overcoming the vacuu-n left in                      mating surfaces may answer such design
                     the interface area.    Hence, the first                      parameters.      The    conical     mating
                     conflict inherent in military cylindri-                      surfaces allow quick air motion during
                     cal connectors is hermeticity vs. ease                       mating and unmating.
                     and speed of operation.                                      ho. 2

                     Another conflict exists  with high fluid
                     pressures. Cylindrical   mating surfaces
                     necessarily require tolerances, even if
                     only 0.0011, or less.   A zero tolerance
                     in the contact area would ensure abso-
                     lute watertightness but would render
                     mating impossible.    Hence, the second
                     conflict is herimeticity vs. basic rules
                     of mechanical design.
                                                                                  When two 'cones engage, air pressure or
                                                                                  vacuum does not exist to     hamper the
                     Closer   tolerances   also mean higher                       connection.   in addition,   two conical
                     manufacturing costs, fragility to mis-                       surfaces can be allowed to "bottom,"
                     handling, and susceptibility to the                          metal-to-metal, thus ensuring complete
                     presence of foreign particles in the                         watertightness while avoiding problems
                     mating area. These conditions create a                       related to close tolerances of cylin-
                     third conflict, hermeticity vs. cost                         drical mating surfaces.     To avoid the
                     and practicality.                                            cost of high precision     conical sur-
                                                                                  faces, two 0 rings can be  used:
                     As a compromise, 11011 rings can be                          F19.3
                     placed in the mating area even though
                     they are not used in standard circular
                     military connectors. 0 rings, however,
                     do not offer the mechanical resistance
                     of metal.   Under high fluid pressures,
                     0  rings can actually get squeezed
                     within   the tolerance gap       existing
                     between the mated cylinders and be
                     flushed out of the mating area.

                                                                      599

                     However, these 0 rings no longer serve                       Furthermore, a connector with conical
                     as the ultimate line of defense against                      mating surfaces does not depend on
                     fluid pressure, chemicals, dust, or                          backshell accessories, like a rubber
                     temperature extremes.      in fact, with                     boot, for hermeticity.      The connector
                     this design, the greater the outside                         can   be    assembled    from    standard,
                     pressure,    the tighter the      conical                    modular components and becomes fully
                     surfaces are jammed against each other,                      field repairable without specialized
                     thus relieving the 0 rings from their                        molding equipment.      Repairs can be
                     hermetic role and making it impossible                       performed without the disposal of the
                     for them to be "flushed" out under                           entire connector or harness.
                     pressure.    Such connectors have been
                     tested under pressure of up to 22,000                        The contact size, density and plating
                     psi when mated, and 1,500 psi unmated.                       can be chosen to min.1mize bulk and
                                                                                  voltage drop, while guaranteeing pro-
                     The unmated hermeticity is enhanced by                       longed usage in the most severe envi-
                     the contact design, which also takes                         ronments.   A connector can also be
                     advantage of conical interfaces:                             provided with a double internal seal
                          rig. 4             Directl                              for extreme fluid pressures and to
                                             ofposalble                           allow   sheath    capture for      perfect
                                                                                  grounding and electromagnetic inter-
                                                                                  ferencelradio    frequency interference
                                                                                  (EM11RF1) shielding:

                     Potting    can   be    applied   in     the
                     transition area existing inside the
                     connector at the level of contact-to-
                     wire junction (See floure 5).
                                                                                                                      Fq,
                                                                                       7@777777777

                                                                                  Military cylindrical connectors serve
                                                                                  military purposes well.       However, a
                              00U.'al                                             civil engineer faced with severe envi-
                                              .1 wh                               romental     constraints should select
                                                                                  comerpial connectors that meet his
                     However, the potting serves more as a                        specific design requirements        rather
                     strain relief in this case, than as a                        than adopting existing military pro-
                     hermeticity    barrier.     The   potting                    ducts.   A connector with conical or
                     allows for mechanical tension to be ap-                      tapered interface is more like     ,ly to
                     plied to the cable without risk of wire                      answer those needs, than a standard,
                     rupture inside the connector.                                cylindrical connector.

                                                                                  Figure 7 below shows the whole concept.

                              Concept (Fig. 7)

                                       high precision  flarnele
                                DU81 0 ring ffmdtilned receptacle
                                PrIotection Insert          male
                                                            plog Grounding              Blip boot
                                                                  clip                  Ino over-molding required)

                                      Conical         Optional
                                     Intertbee       cornpou;           seal feature
                               lCone slope exaggerated for      Conical (tapered) interfacing is a Jupiter patent.
                                 concept visualization)

                                                                        600

                    BIOGRAPHY

                    Alan Bertaux has been president of
                    Jupiter Electronics, Inc., the U.S.
                    subsidiary of C.E. Jupiter S.A. of
                    France,    since its creation in the
                    Chicago area in 1982. Prior to that
                    assignment, he was director of Latin
                    American    operations for Molex Inc.
                    where he worked for 5 years.     He also
                    worked for AMP Inc. where he spent 6
                    years.

                    Mr.   Bertaux    holds    a   degree     in
                    mechanical     engineering    from      the
                    University of Paris, and a B.A. and
                    M.A. from the University of Maryland.
                    Mr. Bertaux also taught at Goucher
                    College and Tufts University, and spent
                    3 years in the U.S. Army. In addition
                    to ECSG, he is a member of Phi Kappa
                    Phi, SME, SMTA, ASQC, IEPS and ISM.

                                                                        601

                        NADIA: WIRELINE RE-ENTRY IN DEEP SEA BOREHOLES

                                               Jacques LEGRAND, Andr6 ECHARDOUR, Luc FLOURY, Henri FLOCH,
                                              Jacques KERDONCUFF, Tanguy LE MOIGN, G6rard LOAEC, Yves RAER

                                            IFREMER, Centre de BREST - Direction de I'Ingenierie et de la Technoloy*e
                                         D6partement Instrumentation, Capteurs et Acoustique - BP 70 - 29263 PLOU ANE
                                                                          FRANCE

                                     ABSTRACT                                    The first trials at sea were completed successfully in
               NADIA is a system clevelopped to complete re-entry ope-           2300 m of water in the Mediterranean Sea. Operations in
               rations in deep sea boreholes, drilled for twenty years by        DSDP Hole 396 B will be conducted in July and August
               the drilling vessels Glomar Challenger and JOIDES Resolu-         1.988.
               tion.
               NADIA is operated by a manned submersible at water
               depth of up to 6000 m, with a capability of lowering                    PHASE 2 - HOVERING ABOVE THE CONE
               instruments in holes of 1000 m of penetration.                                     & I
               This paper describes the system and re-entry operations,                                       RELEASE OF THE SECONDARY
               with some technical details about specific equipments                                J.        FLOTATION ASSEMBLY
               developped within the project NADIA.
               The work to be cqmpleted during the upcoming cruise
               FARE is described. Then, a programme plan of develop-
               ment, following FARE is briefly exposed.

                                 INTRODUCTION
               Deep sea boreholes have been drilled bythe D/VGlomar
               Challenger of the Deep Sea Drilling Project and then by
               the D/V Joides Resolution operated by Texas A & M Uni-
               versity for the Ocean Drilling Programme, since 1968, in
               allmost every parts of the world Oceans.                                  Figure I - NADIA Configuration in the docking phase
               To day, nearly 800 boreholes exist and about 40 of them
               are so called re-entry holes, i.e. fitted with a cone at the               EQUIPMENTS DESCRIPTION
               seafloor and casings in the unconsolidated section of the         NADIA is a non-propelled, free falling device. Descent to
               geologic formation.                                               the sea floor and return to the surface are achieved by
               The only mean to re-occupy these boreholes, either to             gravity and buoyancy. The horizontal displacement bet-
               replace the drill bit during drilling operations or to come       ween the landing point and the cone location is achieved
               back to deepen a hole previously drilled, has been the drill      by the submersible.
               string, hanged below the drilling ship.
               The concept of wireline re-entry, i.e. re-occupation of a         NADIA is composed of four sub-systems:
               drill site in order to lower instrumentation in the borehole      - A main frame, built of welded aluminium alloy tubes,
               using a conventionnal reseach vessel, was born within the         fitted with a winch and its hydraulic control system, the
               DSDP community about 8 years ago, but was never com-              logging tool, the electro-hydraulic connector, a 10 m
               pleted despite several attempts.                                  umbilical link to the submersible, and ancilliary equip-
               This paper describes an original solution, developed in           ments: (mechanical releases, dead weights, cable cutter,
               FRANCE by IFREMER.                                                etc.)
               The approach is the use of a special frame NADIA                  - A main flotation assembly supporting the weight of
               (NAvette cle DIAgraphie - logging schuttle) fitted with a         the main frame. It is fitted with an accoustic navigation
               logging winch and docked into the re-entry cone by a              beacon for tracking NADIA during the vertical trips and
               manned submersible.                                               rendez-vous with the submersible.

                                                          CH2585-8/88/0000- 602 si @1988 IEEE

                - A secondary flotation assembly released to ballast                                       4 Sensors
                the main frame and to dock it down in the re-entry cone.           Lowering and rising of the instruments in the borehole are
                - A descent dead weight, released by the submersible               controled by two parameters: cable length and cable
                before the horizontal displacement at the sea floor.               tension. The cable length is measured at the top pulley,
                                                                                   fitted with 3 Reed switches. A permanent magnet, fixed to
                A more detailed technical description is given of the fol-         the sheave, actuates successively the switches, giving
                lowing sub-systems:                                                pulses directly related to the length of wire payed in or
                I -the winch,                                                      out. The sign of the wire motion is detected bythe chrono-
                2 - the electro-hydraulic connector,                               logy of the 3 pulses.
                3 - the NADIA/submersible umbilical security release,              With 1000 N of tension on the cable, no slipping of the
                4 - the sensors,                                                   wire with respect to the pulley has been measured.
                5 - the control and data acquisition system.                       This simple device gives a precision of � 0.33 m.
                                         I Winch                                   The cable tension is measured with a strain gages tensio-
                                                                                   meter monted between NADIA's frame and the top pul-
                In the present stage of development, NADIA is fitted with          ley. This tensiometer is pressure compensated up to
                1000m of 4.6 mm steel wire. Spooling on the drum is                6000 m of water.
                completed in 12 layers, controlled by a diamond screw
                level wind.                                                        Precision is 0.1 % in the range of 0 to 50 000 N.
                A slow POCLAIN hydraulic motor, modified to work in
                pressure equilibrium, drives the drum under control of a                                                     C"a TENSION
                closed-loop hydraulic circuit. Primary energy is provided                                                    SEM"
                                                                                       MEMO-                                 C"Lf LMGTH
                bythe submersible hydraulic purripworking ata maximum                  WD"UUC                                MEA"Ih* PULLEY
                                                                                       CONNECTOR                             WCKWCAL
                pressure of 14 MPa and a maximum discharge flow of                                                           AXTUATOR
                6.2 Ilmn.                                                              "BILICAL                              CABLE CWTER
                Two different rotating speeds are obtained by changing                 WMC+l                                 LOGMING TOOL
                the cubic capacity of the motor, resulting in linear speeds                                                  Om WrIcAiT
                of the wire from 225 to 450 m/H.
                         2 Electro-hydraulic connector
                Hydraulic and electric links are needed between NADIA
                and the submersible. This function is achieved, at the sea
                floor, by an underwater matable-unmatable connector.
                This device uses an hydraulic locking piston to plug the                         Figure 2 - NADIA General arrangement
                male part of the connector on NADIA to the female part
                moved into the correct position by the arm of the submer-
                sible. The disaccoupling is obtained by springs when the
                piston pressure is released.                                               5, Control and data acquisition
                Three hydraulic links and sixteen electrical conductors can        The different functions (electro-hydraulic connectorwinch
                be connected under 6000 m of water.                                operations and data acquisition) are controled by the
                The hydraulic connection is realised by self-obturating            operator in the submersible.
                front water-tight coupling devices while the electrical            A micro-computer Epson PX8 is used to perform these
                continuity is realised by standard Electra Oceanic connec-         tasks. The commands are:
                tors.                                                              - connect, disconnect,
                                                                                   - speed selection,
                                 3 Security release                                - pay the cable in or out.
                In order to allow the physical separation between NADIA            Data from the cablemeter and the tensiometer are dis-
                and the submersible in case of problems with the electro-          played on the screen for real time control of the operation
                hydraulic connector, the interface between the submersi-           and stored in the RAM for playback with data coming from
                ble and the umbilical link with NADIA isa security release.        the logging instruments and plot.
                This release is actuated by an electrical pulse causing the        A joystick and a separate display are available to ease.the
                ignition of explosive bolts. The,forces needed for the dis-        control operations inside the exiguous sphere of the
                connection are given by compressed springs.                        submersible.

                                                                              603

                                       OPERATIONS
                   A logging operation with NADIA proceeds in the follo-
                   wing steps:
                   1 - Launching of the frame and the flotation assembly            7 - Raising the logging tool back in NADIA'sframe. This
                   (system buoyant 50 to 100 N). Lauching of the descent            operation is similar to phase 6. If the tool get blocked in
                   weight when ship is in a position that gives the closest         the hole, and if it cannot be worked free by operating the
                   impact of the system from the cone (system negatively            winch back and forth, two levels of security are available:
                   buoyant -900 N).                                                 a - a shear pin rated 6000 N provides a weak point at the
                   2 - Landing at the sea bottom. Length between descent            cable head. A fiching neck at the tool upper end will
                   weight and frame is chosen to prevent NADIA from over-           permit the use of the fiching overshot in use on board the
                   shooting or hitting thelsea floor.                               drilling vessel Joides Resolution,
                   3 - The submersible dives. Rendez-vous with NADIA with           b - an hydrostatic cable cutter is f itted in NADIA's frame.
                   the help of the accoustic navigation system and a flash          In case the shear pin cannot be used, the cable can be cut
                   light. The submersible holds NADIA with one arm, adjusts         to set the system free from the cone.
                   her ballast to become neutrally buoyant with NADIA and           8 - At the end of operations, the logging tool is raised
                   releases the descent weight. The submersible moves               back in theframe. The submersible disconnectsthe electro-
                   NADIA towards the cone using its propulsion system.              hydraulic link and replaces it in the basket.
                   4 - Hovering of NADIA above the cone - the secondary             9 - The submersible holds NADIA, lifts it up out of the
                   flotation assembly is released and NADIA isset in the cone       cone and moves a few meters off. The ascent weight is
                   with -600 N negative buoyancy.                                   released. NADIA is set free and pops up to the surface.
                   5 - The submersible connects with the electro-hydraulic          10 - The system is recovered on board the ship.
                   connector to NADIA.

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                                                                                                                            ;2-
                                                                                                                             ii@TT,
                            Figure 3 - NADIA on the fan toil ready for launching

                   6 - Lowering the logging tool. Winch control and data
                   acquisition in the submersible sphere. If the tool is blo-
                   cked, the wire tension decreases and the operator stops                 Figure 4 - NAUTILE: 3 men, 6000 m copobity submersible
                   the winch.

                                                                               604

                          FARE: TESTS IN HOLE DSDP 396 B                                                                                                                       Appendix
                  The first attempt to re-enter a deep sea borehole will take                               NADIA - GENERAL CHARACTERISTICS
                  place in July and August 1988 on board N/O NADIR with
                  the deep submersible NAUTILE.                                                          FRAME
                  The target hole is Hole 396 B, drilled by D/V Glomar                                      overall height      .............................................  3,5 M
                  Challenger in February 1976. It's position is 22059'N and                                 overall diameter         ......................................... 4,0 m
                  43031'W, about 90 nautical miles east of the Mid-Atlantic                                 weight in air     .............................................    1300 kg
                  Ridge.                                                                                    weight in water (descent)            ..........................    9 000 N
                  This hole iscased onthefirst 163 m, on the whole sediment                                 maximum operating depth                ........................    6 000 m
                  section. Open hole extends to 405 m below the sea floor.
                  About two thirds of the open hole were drilled in pillow                               FLOTATION ASSEMBLY:
                  basalts, the bottom third was mainly basaltic gravel and                               2 assemblies of syntactic foa@n packs
                  sand.                                                                                     height    .......................................................  1.6 m
                  Although the cruise FARE (FAiseability RE-entry) is a tech-                               diameter      ...................................................  1.3 m
                  nical test, the opportunity will be taken to collect scientific                           weight in air     ............................................     2 000 kg
                  valuable data. After relocation and inspection of the re-                                 buoyancy      ................................................     7 700 N
                  entry cone, operations to be conducted in the hole are the
                  following:                                                                             WINCH
                  I - Sampling of fluids as deep as possible,                                               maximum cable length             ..............................    1 500 m
                  2 - Temperature continuous logging,                                                       cable diameter        ...........................................  4.6 mm
                  3 - Taking pictures from the walls,                                                       pulling capacity
                                                                                                                      outerlayer     .....................................     8 300 N
                  4 - Test with a 200 mm dummy tool.                                                                  on drum     ......................................       16 600 N
                                                                                                            cable speed
                                       PROJECT - PHASE 2                                                              outer layer    ................................ 0. 15/0.30 m/s
                  The cruise FARE representes the milestone marking the                                                                                              540/1080 m/h
                  end of the first phase of the project NADIA. If these tests                                         on drum     ................................... 0.07/0.15 m/s
                  are successfull, a phase 2 will be initiated with the main                                                                                           270/540 m/h
                  objective of transforming NADIA in a real logging unit.
                  The evolution of the system will involve the following                                 LOGGING TOOLS
                  transformations:                                                                          diameter      ...................................... 100/ 150/200 m m
                  I - Replacement of the cable by a 7 conductors logging                                    length    .......................................................... 2 m
                  cable; this implicates the replacement of the winch drum                                  weight in water       .......................................      1 000 N
                  to support a greater volume and to provide for the electri-
                  cal continuity with the logging tools; the cable length                                TENSION SENSOR
                  measurement device will also be replaced by a sensor                                      range     .....                                        .0 - 50 000 N
                  similar to those used in standard logging operations with
                  a special packaging for high pressure environment.                                        sensitivity   ...................................................  100 N
                  2 - An autonomous data acquisition system, as compatible
                  as possible-to the similar units used in oil well logging will                         CABLE LENGTH SENSOR
                  be added on NADIA'sframe; an electrical power unitwill                                    increment     ..................................................   0,1 m
                  also be added.
                  These transformations will give NADIA the capability of                                ANCILLIARY EQUIPMENTS
                  recording clownhole data for periods of up to a few                                       hydrostatic cable cutter (minimum operating pres-
                  month; the re-entry operations and logging tools lowe-                                    sure 100 bars),
                  ring will still be completed, in this phase, by a manned                                  mechanical actuators for:
                  submersible.                                                                                        cable cutter operation,
                                                                                                                      release descent and ascent dead weights,
                  A final phase 3, in the future, will be to perform the entire                             electro hydraulic NADIA/NAUTILE connector,
                  suite of operations using a remote operated vehicle.                                      hydraulic winch control.

                                                                                                   605

                       IMPEDANCE MEASUREMENTS OF BIOFOULING IN SEAWATER CONDENSERS: AN UPDATE

                                     Patrick K. Sullivan 1,2 and Bruce E. Liebert3

                                    10ceanit Laboratories, Inc., Honolulu, Hawaii
                                  2Department of Ocean Engineering, University of Hawaii
                                3Department of Mechanical Engineering, University of Hawaii

                  Electrode    Impedance Spectroscopy            Hawaiian Electric Company (HECO),
                  (EIS) is a new technology presently            the host utility, is interested in
                  being     investigated     for     its         EIS technology to improve power
                  usefulness in measuring biofouling             plant efficiency. To assist in the
                  in seawater cooled power plants.               first industrial testing of EIS
                  EIS is based on the hypothesis that            technology, HECO has provided space
                  biofouling can be characterized by             within their Honolulu power plant
                  observing its steady state response            facility   as    well as technical
                  to a small amplitude sinusoidal                support.
                  perturbing potential imposed on the
                  biofilm material.    From the change           our research is leading to the
                  in phase and amplitude of          the         development      of   a    diagnostic
                  response      signal   a    real-time          engineering tool that would enhance
                  characterization of the biofilm can            the cost effective operation of
                  be determined.                                 power plants; enhance understanding
                                                                 of biofilm accumulation and factors
                  EIS was developed at the University            that effect its rate; and allow
                  of Hawaii in 1985 for use in Ocean             plant    operators   to assess the
                  Thermal Energy Conversion (OTEC)               effectiveness       of       cleaning
                  materials      testing      research.          techniques. Additionally, it would
                  However, it has      wide    reaching          improve    methods    for   designing
                  applications   in the power industry           condenser   systems;    testing and
                  for measurements of corrosion as               selection   of     materials;     and
                  well as biofouling.    The Electric            evaluating        complex     surface
                  Power Research Institute (EPRI), in            geometries.       Results  from the
                  conjunction     with  the    Hawaiian          ongoing research at the  HECO plant
                  Electric Company (HECO) sponsored              will be presented and discussed.
                  Oceanit Laboratories, Inc. (OLI) to
                  conduct research to determine the
                  usefulness of EIS as an insitu tool
                  for monitoring biofouling in power
                  plant condensers.      Results from
                  this    research     will     largely
                  determine its use as a tool for the
                  power industry.

                                             CH2585-8/88/0000- 606 $1 (c)1988 IEEE

                                 WORLD'S FIRST RIGID FREE-STANDING PRODUCTION RISER

                                                      E. A. FISHER
                                                      H. P. HACKETT

                                          CAMERON OFFSHORE ENGINEERING, INC.
                                          580 WESTLAKE PARK BLVD., SUITE 1650
                                                 HOUSTON, TEXAS 77079

            ABSTRACT                                          FLOATING PRODUCTION SYSTEM

                 The first deep water (15501) floating               In reviewing characteristics of the
            production    system in the Gulf of Mexico        Green Canyon Block 29 discovery, and in
            has been installed in Green Canyon Block 29       reviewing the potential technology avail-
            for the Placid Oil Company. The key compo-        able for the production system, a set of
            nent of this system, and the first of its         criteria evolved for the economic develop-
            kind in the world, is the rigid free-stand-       ment of this field.
            ing production riser which serves as the                 0   System to accommodate simulta-
            conduit for the well fluids up to the                        neous     drilling/workover       and
            floating production facility and for the                     production;
            processed oil and gas back down to the                   0   System to be capable of accommo-
            pipelines on the seafloor.                                   dating 24 wells;
                 This paper reviews the overall float-               0   System    to accommodate surface
            ing production system and focuses on the                     well     flow    control    devices,
            riser   and its components:        the bottom                (chokes)    and    have individual
            connector, a one-piece tapered titanium                      tubing and annulus lines for each
            stress joint, the 601 long steel riser                       well;
            joints wrapped in syntactic foam, the upper              0   System to be capable of           gas
            manifold,    and the flexible       hoses and                lifting any well by means of
            tension system.                                              surface controls;
                                                                     0   System to be able to accommodate
                                                                         production from or injection to
                                                                         any satellite well;
            INTRODUCTION                                             0   System to have the flexibility to
                                                                         work in the water depth range of
                 The Placid Oil Green Canyon 29 Project                  1,5001 to 3,5001;
            is a pioneering effort in many ways:                     0   The subsea control system compo-
                 �     it is the first floating produc-                  nents    must be accessible for
                       tion system in the Gulf of Mexico                 maintenance;
                 �     it is the first floating produc-              0   The floating platform will be
                       tion system designed and certi-                   equipped with "bare bones" pro-
                       fied for a 20 year life with the                  duction    facilities --- a shallow
                       ability to withstand a 100 year                   water production platform site
                       storm                                             will be used for final processing
                 �     it has the deepest oil          well              of oil and gas;
                       completion in the world at 22431              0   Pipelines will be installed to
                       of water depth, exceeding the                     transport the field's oil and gas
                       previous record of 16131                          production to a sales point.
                 �     it has the deepest opertional                 A variety of sytems and designs were
                       pipelines in the Gulf of Mexico        reviewed, analyzed, and costed out; and the
                 �     it has the world's first rigid         optimal design was selected (Figure 1).
                       free-standing production riser
                 �     it will be profitable even at
                       today's reduced oil prices.

                                            CH2585-8/88/0000- 607 si @1988 IEEE

                                FIGURE 1. PLACID OIL GREEN CANYON BLOCK 29 FLOATING PRODUCTION SYSTEM

                    The     floating      production      system
              consists of:
                    0     a     floating      semi-submersible                  spin   resistant     spiral strand
                         .converted to allow simultaneous                       jacketed 4-1/211 wire, a submerged
                          drilling    and production.        The                buoy with 130 kips net buoyancy,
                          particular vessel selected was                        approximately     1500,    of     spin
                          the Penrod 72. Rig modifications                      resistant spiral strand jacketed
                          included the addition of sponsons                     4-1/2" wire, another submerged
                          to "house" the new mooring equip-                     buoy with 50 kips net buoyancy,
                          ment and to increase the payload,                     approximately     12001    of    spin
                          the relocation of the helideck to                     resistant multi-strand 5 wire,
                          provide a clear area for the                          and the bending shoe and linear
                          processing       equipment,        the                winch system in conjunction with
                          "opening up" of various areas to                      large capacity spooling winches.
                          facilitate inspection, the addi-                o     A 24 well slot template located
                          tion    of    vent booms,       subsea                on   the ocean floor         directly
                          controls, and ROV support, the                        beneath the rig. The template is
                          modification     from    a standard                   constructed from standard struc-
                          drive to a top drive drilling                         tural steel shapes to accommodate
                          system, and the addition of the                       the design depth requirement, and
                          process equipment itself.          The                has four rows of six slots. The
                          major    purpose of the process                       two outer rows of slots can be
                          equipment is to split the well                        used for connections of remote
                          fluids into the liquid phase and                      satellite    wells or for wells
                          gas phase, where the liquids will                     drilled    directly    through the
                          flow through one pipeline and the                     template.    The template measures
                          gas through another to a shallow                      out at 1651 long, 821 wide, and
                          water platform for further pro-                       201 tall. It weighs approximate-
                          cessing.     The process-equipment                    ly 1250 tons and is supported by
                          is    designed to handle 40,000                       eight 40" piles.
                          barrels per day of oil and 120                  0     Up to 12 remote satellite wells.
                          million cubic feet per day of                         The wells would be drilled by a
                          gas.                                                  different    semi-submersible and
                    0     An eight-point mooring system for                     would typically be 1coated 5 to
                          the Penrod 72. Each mooring line                      10 miles from the template. The
                          consists of a 77-kip Bruce Flat                       flow from these wells would be
                          Fluke Twin Shank anchor and a 7-                      routed to the template through
                          kip    chain depressor, approxi-                      pipeline on the ocean floor.
                          mately 25001 of 4-1/8" ORQ (oil                0      A shallow water processing plat-
                          rig quality) plus 20% (20% higher                     form.   Although the well      fluids
                          break strength than ORQ)        chain,                are separated into the liquid and
                          10001   of 4-1/4" ORQ plus 20%                        gas phases on the rig, additional
                          chain,    approximately 1250'       of                processing is required.      This is

                                                                 608

                        performed     on a shallow water
                        platform approximately 60 miles
                        from    the     rig/template,      with
                        separate pipelines on     'the ocean
                        floor routing the liquid and gas
                        from the template to the plat-
                        form.    The processed oil and gas
                        are then piped to shore.                                      TENSIONE9
                  0     The rigid free-standing produc-
                        tion riser. The basic function
                        of the riser is to route the well               CA:LE SUPPLY
                        fluids up from the        template to            POOL
                        the floating production system
                        and the separate liquid and gas                       .-A
                        back   down   from   the rig   to the                              TURNDOWN
                        template    and  ocean floor    based                              SHEAVES
                        pipelines.
                                                                     WATER LINE
             RIGID RISER

                  Cameron     offshore Engineering, Inc.
             (Houston, Texas), after working in conjunc-                                            F@'
             tion with Placid in developing the overall               CONNECTION
             f loating     production     system      concept,        PORCH          PONTOON
             designed and supplied the rigid            riser
             system.   The rigid free-standing production                                CENTRALIZER
             riser described by Placid as the most
             innovative   component of the overall system                           FLEXIBLE TENSIONER
             and  a   key  to   its   economics,     is fully                       PIPE     CABLE
             installed and free-standing beneath the
             Penrod 72 (Figure 2).                                                     TENSIOW SHEAVE
                  The riser is the critical link between                                 PACKAGE
             the floating rig on the surface and the
             template   on the ocean floor, and holds the                             CUPPER RISER
                                                                                       ONNECTOR PACKAGE
             production and annulus lines from each
             well, the oil and gas sales lines, and the
             control line bundles. From the bottom up,
             the riser has:       a structural riser base
             welded   into the template, to     transfer the                       UPPER RISER FLOTATION
             riser  loads through the template       into the                          AIR TANKS
             piles and soil; a collet connector, to
             provide a strong reliable attachment to the
             riser base and to provide a connect point
             for running the riser and a disconnect
             point for retrieving the riser; a one piece
             titanium stress joint, to provide              the
             necessary flexibility; the riser joints
             with internal air chambers and external
             foam modules, to provide the necessary lift
             to be self-buoyant and to act as support
             for the production, annulus, and sales
             lines; the upper_,,,air tanks, to provide
             additional lift; the upper riser connector
             package, to provide a single point where
             the  entire array of flow      line connections                          STRESS JOINT ASSEMBLY
             could  be separated to quickly      release the                          LOWER CONNECTOR
             riser, or where each flowline could be
             connected/disconnected        separately       for                          RISER BASE
             maintenance;   the flexible hoses,      to allow                          1EMPUIE
             the flow up to the rig and back down to the                          OCEAN FLOOR
             riser    while simultaneously serving           to
             decouple the relative motions of the rig
             and riser; and the specially             designed
             tensioner system, where the tensioner,is
             not used to hold the riser up,      but    rather                   FIGURE 2. RIGID RISER
           ,is used to maintain the proper relative
             position between the rig and riser.
                                                                                          '.IN' AS -MBLY

                                                                                         CONCOR

                                                                                         IS  G
                                                                                        . LREWR.TA ES

                                                               609

              - Lower Riser Package
                   The lower riser package serves several
                                                            S
              into the template, to connect the riser and
              flowlines to the template, and to provide
              the necessary flexure between the fixed
              functions - to transfer the riser load

              template and the relatively mobile riser.
                   The riser base is welded into the
              template,  and serves to transfer the riser                                          L@er riser connector
              loads into the template, and to act as a
              fixed connection point for the riser and
              flowlines.
                   The  lower c6llet connector (Figure 3)                                          Hydraulic cylinder (8)
              is flanged to the bottom of the stress
              joint and lands on the connector hub which
              is   welded into the riser base.           This
              connector hydraulically locks the riser to
              the template, thereby, transmitting the
              riser   loads into the riser base.      Special                                      Collet segrnents
              high strength steel with excellent fracture
              toughness    and   fatigue   properties     was      Locked                   Unlocked
              selected for these components to ensure the
              20-year system design life was achieved.
                   The stress joint assembly,      which is                                -Riser base hub
              located   Immediately beneath the lowest
              riser   joint, provides the        flexibility
              needed for the relatively abrupt bend in
              the riser near its foundation. The stress
              joint   (Figure  4)  provides a   smooth dis-                                        Connector body stab
              placement curve for the production riser,
              producing manageable static loads and a
              lengthened fatigue life for both the stress
              joint and its included production, annulus,
              and export lines. Titanium was selected
              over steel for the stress joint due to its
              substantially superior properties, namely
              twice the flexibility, half the weight,
              higher strength and toughness,     and excep-                                       %.,- ENGINEERWO, INC
              tional corrosion resistance and fatigue
              life    in a seawater      environment.     The           FIGURE 3. LOWER COLLET CONNECTOR
              titanium stress joint allows the riser to
              stay connected to the rig even in a 100-
              year storm.

                   The flowlines are run after the riser
              has been connected.
                                        The production and
              annulus tubing anchors are stabbed into the
              mating receptacle located in the riser
              base, and are
                                locked In through weight
              setting of an    anchoring latch containing
              elastomeric seals like those used to set
              tubing in downhole packers. The tubing can
              be retrieved using either right-hand rota-
              tion or overpull.       The export tubes are
              locked Into their riser base receptacles
              using tieback connectors containing elasto-
                                                                                                            Z"
              meric lip-type seals. The tieback connec-
              tors are similar to mechanical connectors
              used to tieback casing strings in subsea
              wellheads, and are locked and unlocked
              using a setting tool which is run on drill
              pipe through the export tube.

              - Intermediate Riser Package
                   The riser consist of 26   50-foot joints
              .of flanged and cathodically   protected high
              strength steel pipe.       Each joint has an
              open bottom internal air tank with a cas-
              cade tube welded inside to air the joint                                                 L
              above   it.   These   joints are encased in               FIGURE 4. TITANIUM STRESS JOINT

                                                             610

             syntactic foam modules that provide both        riser and the tension lines.      The tension
             passive buoyancy and path ways          molded  in the lines remains essentially constant.
             within them to guide and support the pro-            The pontoon porches added to the rig
             duction and annulus lines along with the        are made of structural steel members suit-
             oil sales line. An external air valve Is        able for transferring the vertical moment
             also provided on each joint for an ROV to       loads from the dynamic motion of the flex-
             increase or decrease the amount of air In       ible hoses into the pontoon structural
             each joint as desired.                          frames. The flexible pipe itself runs from
                  Vortex shedding strakes are attached       the porches to the top of the riser located
             to the outside of the foam modules.        The  1501 below the water surface, and serves as
             riser is instrumented to monitor its per-       a conduit for the flow and to decouple the
             formance and stress level. An environmen-       relative motion of the rig and   riser.
             tal instrumentation package has also been
             provided to correlate the riser stress
             levels with environmental conditions.

             - Upper Riser Package
                  The upper riser package serves several
             functions - to connect the flowlines to the
             rig while simultaneously decoupling the
             relative motion of the rig and riser,       to
             maintain the riser In the proper relative
             position with respect to the rig, and to
                                                                                   1W
             allow the rig to quickly disconnect from
             the riser If desired or to individually
             disconnect each flowline for maintenance.

                  The air tanks at   the top of the riser
             (Figure 5) provide additional lift and
             "righting" force to offset the forces from
             the current. These tanks are modularized
             and the top tanks are tapered to avoid
             interference with the hose bundles.
                  The   upper riser connector package
             (URCP) provides the link between the rigid
             tubing which protrudes from the top of the
             riser and the flexible pipe which Is sus-
             pended from the rig.      In doing so,      it
                                                                                                F
             provides the capability to quickly discon-
                             from the rig if desired or
             nect the riser
             to individually disconnect any given flow-                                 @y
                                                                     .@A
             line for maintenance. Individual hydraulic
             mini-connectors are used in conjunction
             with rigid pipe goosenecks to connect the
             tubing strings to the flexible pipe. A
             large hydraulic connector is located at the
             center of the URCP. This connector trans-
             mits forces from the riser tensioners to
             the  riser, as well as providing a connec-          FIGURE 5. UPPER AIR TANKS, AS RISER IS RUN
             tion for the 1211 gas sales line.    It also
             provides the one point quick disconnect
             feature.
                  The production riser tensioner     system
             acts more as a riser centralizer than as a
             typical riser tensioner. The production
             riser is free standing and the tensioner is
             not required for structural support. By
             applying a restraining force to the top of
             the rigid production riser and limiting Its
             motion relative to the vessel, the flexible
             flowlines between the vessel and the rigid
             riser can be kept to a more easily managed
             length and can thus remain connected during
             more severe environmental conditions. The
             tensloners supply such a restraining force
             and the farther the production riser moves
             from Its centrallzed position the greater
             the restraining force. This is due to the
             changing angle between the top of the rigid

                                                          611

                                       A SINGLE BOARD COMPUTER BASED SAIL CONTROLLER

                                                      Timothy F. Pfeiffer

                                                   University of Delaware

                                                                     85 we were able to develop a fairly clear
                                                                     set   of    specifications     for    the new
                                  ABSTRACT                           controller. Foremost, the data were to be
                                                                     recorded on standard MS DOS disks in a
                     Several companies      are now offering         flat ASCII format that could be read into
              IBM PC compatible single board computers.              spreadsheets, statistical,        or plotting
              In their simplest form they do not have                programs with      no   further processing.
              keyboards or      display adapters, but do             Secondly the data collection portion of
              include                                                the program should be capable of starting
              controllers for standard         MS    DOS disk        itself, and      restarting after a power
              drives. Thus, while they cannot run much               failure, with no operator intervention.
              off the shelf software, programs can be                Our final     specification was that the
              written on a standard PC and then executed             controller have enough power and memory to
              on the singleboard computer.         In addition       perform some real time processing of the
              to MS DOS software         compatiblity, some          data such as computing salinity.
              models also include a PC bus expansion slot
              which provides hardware compatiblity for                  As we evaluated hardware to fill these
              standardvideo and interface boards.             We     requirements we realized that a standard
              have implemented a SAIL controller using a             MS   DOS    computer    actually     had more
              single board computer from Ampro Computers,            capability than    the job required.      Ampro
              Inc.     The software does include a few               Computers Inc.      offers a single board
              provisions to allow it to operate without              computer, known    as the Little Board 186,
              an operator, but essentially it is ordinary            which runs under   MS DOS. The Little Board
              PC software.        These boards provide an            186 is driven by   an Intel 80186 processor,
              inexpensive and easily accessible method of            has 512 kilobytes of memory, two serial
              adding      substantial      intelligence       to     ports, one parallel printer port, and,a
              instrumentation systems.                               disk drive controller.       All of this is
                                                                     contained on a single circuit board which
                                                                     is the same size as a 5.25 inch disk drive
                                                                     (5.75 inches x 7.75 inches). The Little
                                                                     Board 186 does not include any display
                     The Serial Ascii Instrumentation Loop           driver or keyboard interface.         With the
              is     a   hardware    and software protocol           addition of a power supply and standard
              developed under       the leadership of Dr.            360 kilobyte 5.25 inch floppy disk drive
              Roderick Mesecar, Oregon State University,             this    one    circuit    board    becomes     a
              which is used for collecting data from a               functional MS DOS computer.           The only
              variety      of     sources     aboard      ship.      cables required are one power cable to the
              Essentially a SAIL system is composed of               floppy drive, a second identical power
              data modules which read information from               cable for the Little Board 186 and a
              various instruments and devices aboard the             single ribbon cable between the disk drive
              ship and a controller.           The controller        and the Little Board 186. In this minimal
              periodically       interrogates      the     data      configuration the computer will start from
              modules,     processes     and   records their         a standard MS DOS system disk and execute
              responses. The original controller for our             any commands in the autoexec.bat file just
              system    was     an   HP 85 computer which            as any other MS DOS computer would. Of
              provided a      display, printer, and tape             course with      no   display     or keyboard
              cartridge data storage in one integrated               included in the system the program cannot
              package.      Recently, as both we and the             interact with an operator.         However all
              scientific     users    of    our system have          forms of file manipulation and internal
              standardized on MS DOS based computers for             processing will be carried out properly
              many data acquisition and analysis tasks               and the serial and parallel ports are
              it became apparent that we needed an MS                available. Just these three components
              DOS based SAIL controller.                             could, for example, if connected to a
                                                                     printer, act as an off-line print spooler.
                                                                     All that would be required would be to
                     Based on our experience with the HP             include an autoexec.bat file with the

                                                 CH2585-8/88/0000- 612 $1 @1988 IEEE

            appropriate print commands on the disk                module. The data from unknown modules is
            containing the files to be printed. The               simply    stored   as    received    with no
            disk     files     are   completely    MS    DOS      formatting, scaling, or other calculation
            compatible.     One of the Little Board 186's         applied to it. For example we have a flow
            two serial ports is configured to act as              through Turner Designs fluorometer which
            the system console.       If a standard RS 232        has two analog outputs, one for range and
            ASCII     terminal is attached to this port           the other for the dial.     We have assigned
            the Little      Board 186 responds to the             the fluorometer to addresses 30 for range
            terminal's keyboard and displays program              and 31 for dial.     Thus during the loop
            output on the terminal's screen. Programs             poll the software will expect to find
            which are strictly character based operate            analog modules at those two addresses and
            exactly    as    one   would expect.        This      will assume that analog modules at those
            configuration is very different from the              addresses are indeed connected to the
            hardware found in a standard PC, so the               fluorometer.     If one of those analog
            program must be restricted to simple MS               modules is to be used with an instrument
            DOS and ROM BIOS character based input and            other than the fluorometer, the module
            output. The software cannot write directly            must be opened and set to a different
            to the     display hardware and there is              address. While this approach does reduce
            essentially no graphics capability. This              the flexibility of the system, I believe
            means that a great deal of commercial MS              that it increases the integrity of the
            DOS      application     software,    such    as      data by reducing      the    possibility of
            spreadsheets     and   full    featured     word      confusion over which module was recording
            processors, will not run on these boards.             which signal. If the data from a module
            However this is hardly a drawback for a               is not required, that module is simply
            machine    which    will    be   dedicated to         disconnected from the loop.
            controlling a SAIL loop through its serial
            interface.                                               Once the software has established the
                                                                  population of modules which are present on
                  The hardware for our SAIL system is             the loop it begins collecting data by
            composed of      OSU data modules, an OSU             addressing each module in turn.            The
            coupler module, and the Little Board 186              function associated with each known module
            with its power supply and disk drive. The             formats the data into engineering units,
            coupler module provides both power for the            applies   calibration     coefficients,      or
            loop and an RS 232 interface to the loop.             otherwise processes the data.        The data
            The Little Board 186's serial interface is            from unknown modules is simply stored as
            connected to the coupler module. There                received. After data has been gathered
            normally is a terminal attached to the                from all the modules,     the functions are
            Little Board 186's second serial port to              called which utilize the data from two or
            provide a display.                                    more modules to compute a value. For
                                                                  example, when the salinity function is
                                                                  called   it    first    verifies that both
                  The software   which  drives the Little         temperature and conductivity modules are
            Board 186 has been   designed to run with no          present, then it retrieves the stored data
            intervention on the part of an operator.              for conductivity and temperature, computes
            In fact, the system is normally deployed              salinity, and stores the result.
            with no keyboard attached to it so there
            is no possibility of a human interfering                At the conclusion of each frame, the
            with the execution of the program.           The      data is written to disk. The disk access
            first task performed by the program is to             is buffered by first writing the data to a
            poll the loop, by issuing the information             300 kilobyte ram disk which is created
            address for each of the possible loop                 with standard MS DOS software when the
            addresses. According to the SAIL standard             system is first powered up, Every five
            when a module receives its information                minutes the contents of the ram disk is
            address it is to return a description of              copied to the physical floppy disk. The
            itself.    We    have    established standard         software traps the DOS critical error
            addresses for those       modules    which we         handler so that if there is a problem with
            normally use, based on the UNOLS Standard             the disk, such as no disk in the drive or
            Ship Parameters, extended where necessary.            the disk being full, the program is able
            The software then compares the responses              to continue instead of stopping at the DOS
            received from polling the loop with the               "Abort, retry, ignore?" prompt. If the
            expected messages which are stored in the             floppy disk is not accessible for any
            program.     If any other type of module              reason the program continues to add data
            answers, it will be flagged as an unknown             to the file in the ram disk and check the
            module. Any module which responds from an             floppy disk every five minutes. When the
            address which has not been assigned within            floppy does become available the entire
            the program is       considered    an unknown         ram disk file is copied to it. If the

                                                            613

              floppy is not available and the ram disk             return at the end of the line.         At the
              fills, the program will continue to run,             present time we have no modules which
              but the data is not being stored.                    return text messages but if one were added
                                                                   to the system its formatting function
                     After the data is written to disk it          would enclose the text in quotes to ensure
              is   displayed.        The display function          that it would be read properly.      The data
              includes       formatting     and     labelling      files contain data only, with no titles or
              information for all the known modules and            other non-data items to interfere with
              labels data from any unknown modules with            reading the data.     Each time the program
              the address of the module. The display               opens a new data file it also writes a
              screen for the Little Board 186 is simply            header file. The header file is simply
              a terminal driven by a serial interface.             two lines of text which identify the data
              There is no handshaking required between             and their units in the associated data
              the Little Board 186 and the terminal so             file. This approach does present a slight
              if the terminal fails, or if no display is           possibility that the wrong header might be
              desired, the terminal can be turned off              applied to a data file, but I feel that
              without effecting the execution of the               the risk is small compared to the benefit
              software.                                            of the ease of access to the data. if
                                                                   desired the two files can be concatenated
                     The     software continuously monitors        so that both headers and numeric data are
              the loop for continuity. If the loop is              in a single file.
              interrupted at any time, as by unplugging
              a module, data acquisition halts and the                MS DOS based single board computers
              program attempts      to copy all data in            similar to the Little Board 186 which I
              memory to the floppy disk and then the               used for this project are available from
              data    file     is   closed.       Since     an     several manufacturers and are a simple and
              interruption of the loop may well indicate           relatively inexpensive route to creating
              a change. in the loop configuration, the             data       loggers       and       intelligent
              software simply restarts, itself from the            instrumentation. Since the software.can
              beginning when      continuity is restored.          be developed using any MS DOS tools there
              Thus after every break in the loop the               is.no need to purchase cross compilers,
              modules are polled, and new header and               prom programmers, or development systems.
              data files are opened.         Since it is not       The cost of creating     a complete system,
              possible to add a module to the loop                 assuming that a desktop         computer and
              without creating a break condition which             language are already available, is simply
              the software is able to recognize, the               the cost of the Little Board 186, some
              data from      all modules will always be            hardware to mount it in an appropriate
              recorded.                                            enclosure, and whatever time it takes to
                                                                   write the software.
                     The    printer   interface    has been
              handled with the same philosophy. Once                  The project described in this article
              every 10 data samples the software checks            was supported in part by the National
              the status of the printer port. If the               Science Foundation.
              printer is not       available    the program
              simply continues.         If the printer is
              present and on line, the current data
              frame is printed.      Headers are printed at
              the top of each page.      If the length of a
              data frame is greater than 132 characters
              additional lines are used and a blank line
              is inserted before the next frame. I have
              made no provision for further formatting
              of the data or selectively printing the
              data from certain modules as I believe
              this     is  best    done off line with a
              spreadsheet     or   statistical    data base
              program.

                     In order to allow the data files to
              be read directly into spreadsheets or other
              programs with no further processing the
              format has , been      kept    as    simple as
              possible.      The files are standard DOS
              ASCII text with the data from each sample
              interval written       on    a   single line,
              separated by spaces, and with a carriage

                                                              614

                         ON THE-KNOWLEDGE-BASED EXPERT SYSTEM FOR MARINE INSTRUMENTATION

                                                         M.R.Nayak

                                          National Institute of Oceanography,
                                            Dona Paula, Goa-403 004. INDIA.

                               ABSTARCT                           Artificial Intelligence (AI) originally
                                                                a branch of computer science has entered
                                                                in   commercial     technology     enabling
                The combination of intelligence and             computers to perform intelligent actions
              marine instrumentation has pushed the             normally attributed to human beings. One
              frontiers of      oceanography   to great         of the most promising areas of applied
              heights. One of the frontiers is the              AI is the 'expert system' .(ES) used to
              development of knowledge-based expert             solve problems requiring the knowledge
              systems (KbES). Marine instrumentation            and skill  'of human experise Z-1-7. The
              demands    a     comprehensive   set   .  of      last few years have 'seen an increasing
              requirements,    integrating diversified          interest in the development of knowledge
              technologies into the intelligent system          based expert systems (KbES) Z2_7.
              (that can be programmed, controlled and
              made easy to operate). Extensive search
              of   knowledge-base     is,  in    general,                     2. METHODOLOGY
              involved particularly while choosing the            Knowledge repre .sentation is basically
              appropriate digital IC logic family        '      the. link that binds much of AI together.
              Knowledge development process for an
                                                                In contrast to conventional database
              :expert system is discussed in the paper.
                                                                systems, AI-systems require knowledge-
                                                                base with diverse kinds of knowledge.
                                                                These include knowledge about - objects,
                                                                time, goals, motivation, actions, etc;
                                                                in   brief, classified; as       objective
                                                                (quantitative)        and        subjective
                                                                (qualitative).    A . general    Ynowledge
                                                                representation is provided by Brachman
                                                                and Smith Z-- 3 _7, while summaries are
                           1. INTRODUCTION                      given by Barr and Fiegenbaum f 4-7. Most
                                                                of   the knowledge-systems incorporate
                 In-situ data collection in the ocean           knowledge    through   rules    and    data
              is expensive and unpredictable even when.         structures.
              the programme     is well     planned and:                 I
              executed. Inspite     of    the    inherent         @Marine instrument designer has to make
              difficulties, little guidance is found            a   large    search   for choosing       the
              in the literature to assist in the                appropriate    components,    particularly
              planning ' and    organizational stages;          digital Integrated Circuits (ICs) logic
              Marine instrument design,programme can            family   from    a knowledge-base..     The
              .be conceptualised into the following             knowledge development process -for an
              steps:                                            expert system     leading to     a proper
                - identification of the objectives,             decision on the selection of ICs is
                - identification of the data to be              being discussed.
                  obtained,
                - detailed electronic design                      A long standing need is felt to have a
                  (including selection of sensors with          large   knowledge-base     expert   system
                  proper resolution, accuracy and               particularly to provide advice on the
                  ,logistics)                                   circuit design for marine/oceanographic
                - implementation of the design (inco-           instruments. The rules are a combination
                  rporating any modifications whenever          of a set of procedures which are user
                  found necessary).                             modifiable. The knowledge-base consists

                                             CH2585-8/88/0000- 615 $1 @1988 IEEE

                      of       a    large         number         of        criteria,                         Once        the       design engineer , has
                      conditions,            specifications               on         the            identified the required specifications:
                      various types of digital logic                       families.                evironmental and functional parameters
                      The criteria for decision making is:                                          can. be        .expressed in terms of 0knits'
                                  Whether sufficient information is                                 out of) Ch to                  C."% . The number of
                                  available,                                                        functions              thus       identified            for        a
                                  whether conditions for selection                                  particular@application, now represents
                                  of proper components for a parti-                                 the availability of complex circuits.
                                  cular design,are satisfied.                                       Comparison can now be made based on the
                                                                                                    AND-OR rules within the category of.ICs
                         Generally,a         marine instrument engineer                             Z-8 _7.
                      requires' an                exhaustive            search            of
                      component particularly. constrained by                                            The       basic concept underlying this
                      two factors Ir 5.7:                                                           design,. is the use                      of minimum but
                               - lack of electrical power from the                                  sufficient amount of knowledge-base(Kb)
                                  shore (low power devices);                                        to design an optimum solution in the
                               - harsh marine environment (high                                     form of an expert system (ES). The
                                  relative humidity).                                               standard minimization techniques such as
                      Hence, out of the electronic (digital)                                        Karnaugh-map or Quine-McCluskey methods
                      logic family of RTL, DTL, TTL, LSTTL,                                         could be used to arrive at the minimised
                      ,nMOS, pMOS, CMOS, PLEs the choice falls                                      design in a marine instrument design
                      on*.                                                                          programme with particular emphasis on
                           *   LSTTL : Low Power Schottky TTL,                                      oceanographic applications.( Fig.1)
                           *   nMOS : n-channel MOS,
                           *   PMOS : P-channel MOS,
                           *   CMOS : Complementary Symmetry MOS,
                               CMOS PLEB: CMOS Programmable Logic
                                                 Elements.

                         The basic            characteristics of                  these                                                      Logic Family
                      devices ake described in RL Morris and
                      JR Miller C 6 -7, and PLE Handbook C 7 -7.                                                                                FLF
                      The selection of devices. can be made
                      based on the following characteristics:
                           -   fanout (n),
                           -   noise immunity (dc and ac),                                                                   F1      1C, 1C,          C, C,     Ic
                                                                                                                                                                In
                           -   power dissipation per gate                     (m.W),                                       LSTTL nMOS pMOS C110S PLE
                           -   ambient temperature (* C),
                           -   operating RH ( %k,                                                              fan-out
                           -   clock rate (MHz)f.
                           -   propagation delay             per gate         (nS),                          :noise imm
                           -   switching speed,
                               input characteristics,                                                        6 power diss:   *       0
                               output characteristics,                  'and
                               power supply voltage.                                                         a amb. temp:    0       9
                        The    knowledge bank consists                  of '  all the                        0 opg. RH
                      ,above           mentioned             categories                   of
                      information (values). In addition,                             the                     * dk rate
                      .above        categories            can       further               be
                      sub-divided into a large number of sub-                                                9 prop. delay:
                      categoiies. As an example, 'fan-out.' < 5
                      'or 5<f<10; etc. These bits of knowledge
                      @can bs coded. and stored as knowledge
                      .information bits ("knits*, in short) in
                      @the knowledge-bank, after sub-dividing
                      the main categories into a large number
                      of          thinkable            categories.                 These
                      !categories and sub-units can thus be!
                      arranged in a matrix organisation                          as:

                                  C% C111 C11 C41 CS1 C&                C%1
                                  C %a. Cau C32. C43L C52 C&I           Ch,.                                 e switchg spd:

                                  C          C C       C C              C
                                                                                                               Fig. 1 Logic   Families. classification

                                                                                             616

                   All the    knowledge representation                       5. REFERENCES
              characteristics can be correlated during
              the      selection       of       knowledge       1. Kaisler S. EXPERT SYSTEMS:AN OVERVIEW
              representation     formats     to     reduce         IEEE Trans.Ocean Engg,VolOE-11,No.4,
              repetition. The variety of     knowledge is          pp442-448, October 1986.
              stored using a data based      on a widely
              divergent internal storage structure.             2. Helen C. Shen & GFP Signarowski, A
              The decisions      for the selection of              KNOWLEDGE REPRESENTATON FOR ROVING
              appropriate components by accessing the              ROBOTS. Proc.II Conf.on AI applicatn
              @knowledge representation formats, and               (CAIA).IEEE Comp.Soc.1985 pp621-628.
              the system control structure         is an
              important stage of the design. Although           3. Brachman RJ & BC Smith, SIGART
              the sequence and extent of operations                NEWSLETTER, No.90 (Feb.1980).
              execution may change, the manner of
              monitoring, tracking and extracting the           4. Barr a & Feigenbaum E, THE HANDBOOK
              relevant inference decisions does not.               OF ARTIFICIAL INTELLIGENCE, Voll,
                                                                     Harris Tech.Press,Stanford,USA)1981

                            3. CONCLUSIONS                      5. Desa E, MR Nayak, RGP Desai.MICRO-
                                                                   PROCESSOR DESIGN ASPECTS FOR COASTAL
                In general, marine instrumentation can             OCEANOGRAPHIC INSTRUMENTS. Jour.of
              be conceptualised into several steps,                Coastal Res.(USA). 4(3) 1988.
              vi z;.:
                   - identification of objectives,              6. Morris RL & JR Miller. DESIGNING WITH
                   - identification of the data from               TTL ICs. 1982.; McGraw-Hill Kogakusha
                     the knowledge-bank,                           Ltd; Japan.
                   - detailed design of the programme
                     including selection of the compo-          7. PLE HANDBOOK. Monolithic Memories Inc
                     nents and monitoring network,                 1987 USA.
                     data processing, and.
                     data analysis.                             8. Mazlak LJ. USING SUFFICIENCY THRESHOD
                                                                   RULES IN A KNOWLEDGE BASED SYSTEM.
               As an example of the application of                 Proc.I Int'l Workshop on Expert ,
              knowledge    engineering in the       early          Database System.October 1984,p730-734
              stages of     the design, the role of
              knowledge-base in the understanding of
              the specifications is considered here.                           ---------
              When the product is to be designed, the
              desires of the user must be represented
              in   the form of the        specificitions
              according to which the design process is
              carried out. The designer then addresses
              the knowledge-base for decision-making
              to select the appropriate logic family
              for the specific marine application.
              Emphasis is given particularly to the
              role of knowledge-base in expert systems
              of the future. This being a new field,
              it is expected to have a wide range of
              applications particularly in the design
              of marine instruments for long-term,
              remote,    unattended    operations.    The
              continuation of effort is anticipated in
              the future development in this area.

                           4.ACKNOWLEDGEMENTS

               The author wishes to thank Dr.B.N.Desai
              Director, Dr.E.Desa, Head, MICD         and
              .S/Shri J.S.Sarupria and G.V.Reddy for
              @@useful discussions in, the preparation
              .and presentation of this paper.

                                                           617

                                        OPDIN    ONE WAY THE OCEAN COMMUNITY INFORMS

                                                       Ronald J. Smith

                                       Ocean Pollution Data and Information Network
                                             National Oceanographic Data Center
                                      National Oceanic and Atmospheric Administration
                                                   Washington, DC 20235

                                 ABSTRACT                          identified as potential field data col-
                                                                   lectors.    Summaries by year, project
               In 1978 the National Ocean Pollution                region, and pollutant type were gener-
               Planning Act established NOAA's respon-             ated prior to a more detailed project
               sibility for the timely dissemination of            review.
               ocean pollution information produced by
               Federally funded or sponsored programs              Further review of the flagged projects
               to persons having an interest in ocean              involved tracking them across success-
               pollution research, development and mon-            ive annual Catalogs to remove redundancy
               itoring. To this end, NOAA's National               and to identify any changes in primary
               Oceanographic Data Center (NODC) created            investigators.      A   report was       then
               the ocean Pollution Data and Information            generated that lists the projects for
               Network (OPDIN). Since 1981 the Network             each fiscal year by Agency, Department,
               has been providing the marine pollution             and Program.       For each project the
               community with an extensive list of pro-            report provides    project title, region,
               ducts and services. One of the Network's            data type, point of contact, institu-
               recent efforts is to identify Federally             tion, and Catalog project number.
               funded projects listed in the FY 1978 -
               FY 1983 editions of the Federal Marine              This second stage of project review
               Pollution Project Catalog that have col-            resulted in a list of 393 projects as
               lected marine pollution field data.         A       potential sources of marine pollution
               final report is targeted for the end of             data.   The types of data which these
               1988. It will list data-producing pro-              projects may have produced have been
               jects by agency, program, institution,              corre
               and primary investigator.                                lated with the pollutant categories
                                                                   (Table 1) used in the National Marine
                                                                   Pollution Plan (NMPPO 1985b).            Each
                             INTRODUCTION                          project is also identified by its region
                                                                   of interest (Table 2). The number of
               Section 8 of the National ocean Pollu-              projects potentially producing data in
               tion Planning Act of 1978 (Public Law               each of the 'data type' categories is
               95-273,   supplemented by PL 99-272 to              summarized by marine pollution program
               include specifically the Great Lakes and            in Table 3. The number of projects pro-
               estuaries of National importance) man-              ducing data for each region is summar-
               dates that the results of Federally                 ized by program in Table 4.
               sponsored marine pollution programs be
               disseminated to all interested persons.
               In   an    effort    to    fulfill     NOAA's                PROJECT WORKSHEET AND
               responsibility under Section 8 of the                         ASSOCIATED DATABASE
               Act,    the   Central coordination        and       A worksheet was created to facilitate
               Referral Office (CCRO) of the Ocean                 individual project characterization and
               Pollution Data and Information Network              future database key-entry. The work-
               (OPDIN) has identified those Federally-             sheet    contained project       information
               funded marine pollution related projects            gathered from the Catalogs. It also in-
               described in the annual Catalogs of Fed-            cluded the following attribute fields to
               eral Projects published for Fiscal Years            be completed by the most recent project
               1978 through 1983 (COPRDM 1978,         1979,       contact or primary investigator:
               1981, 1982, 1983, 1984) that may have
               collected pollution related measurements              * Did this project collect field data?
               in the marine environment.                            * Region of study
                                                                     * Zone of interest
               Approximately 20% of the over 5,300                   * Data types ( pollutant or parameter)
               separate Catalog projects were initially              * Survey periods

                                                                618 United States Government work not protected by copyright

              �  Number of surveys                              projects did collect marine pollution
              �  Approximate quantity of data                   field data. Most project data is avail-
              �  Present storage media of results               able to interested parties in the form
              �  Location of stored data                        of journal papers or agency publica-
              �  Data availability to secondary user            tions. Other projects have generated
              �  Cost of making data available                  digital data which is available in vary-
              �  Further comments                               ing degrees to secondary users.

            copies of individual project worksheets
            were forwarded to the most recent re-                            FUTURE EFFORTS
            spective primary investigator as listed
            in the Catalogs.                                    The project worksheet responses have
                                                                been key-entered into the database and
            DATAEASE, a commercial DBMS package, was            a report will be generated in the latter
            used to design a database to hold the               part of 1988 identifying data and infor-
            information gathered from the worksheet             mation resources potentially available
            responses.                                          to secondary users. For easy access, the
                                                                report will be indexed by data type and
                                                                region.
                    PROJECT WORKSHEET RESPONSE
                                                                Depending on the success of the current
            A total of 393 project worksheets were              effort, a follow-up evaluation of the FY
            forwarded    to the respective project              1984 and FY 1985 Catalogs (NMPPO 1985a,
            primary investigators or contacts. To               NMPPO, 1985c) may also be produced.       The
            date,      approximately     150    completed       marine pollution data and information
            worksheets have been returned to the                user   will,     as in the past,         help
            Network.      'Initial   review of      these       determine the utility and future Network
            returns    indicate that 90% of these               resources expended on this task.

                                                    TABLE I

                            Occurrences     Pollutant Category
                                  165       Metali-and inorganic chemicals (F)
                                  140       synthetic organic chemicals (B)
                                   92       Petroleum and petroleum products (A)
                                   91       Nutrients and other biostimulants (E)
                                   63       Habitat modification and sediment deposition (H)
                                   44     - Miscellaneous (I)
                                   40     - Pathogens and microorganisms (D)
                                   30     - Radionuclides (G)
                                    3     - Halogens and halogenation products (C)
                                ----      - ------------------------------------------
                                  668       Total Number of Occurrences

                                                      TABLE 2

                      Region  Count    Region
                              92   -   NE    -  New England and Mid-Atlantic States
                              80   -   GL    -  Great Lakes States including portions of New
                                                York and Pennsylvania
                              67   -   us    -  All regions or possible multiple undefined areas
                              43   -   SE    -  North and South Carolina, Georgia, the east
                                                coast of Florida, Puerto Rico and the Virgin
                                                Islands
                              39   -   NW    -  Washington and Oregon
                              38   -   GM    -  West coast of Florida and all states bordering
                                                on the Gulf of Mexico
                              35   -   SW    -  California, Hawaii, Guam, American Samoa and
                                                the Trust Territories
                              19   -   AK    -  Alaska

                                                            619

                                                                      TABLE 3

                                                 Data Type Distributio of Potential Data Activities

                                     Department/Agency-Program                   Total        Data Type Count
                                                                                 Proj. A B C D E F G H
                                     ------------------------------------------------------------------------

                                     USDA-Effects of Agricultural Practices            5  -   2  -  -   3  1  -   3  -

                                     NOAA-Coastal and Estuarine Assess. Program 15        7 10   -  1   110   -   1  2
                                          Ocean Use Impact Program                     4  - - -     2   2  2  -   -  -
                                          Deep seabed mining Environmental Res.        3  - - - - -        1  -   1  2
                                          National Marine Sanctuaries Program          1  - - - -       I  -  -   1  -
                                          ERL Ocean Pollution Studies Program          3  -   2  -  1   2  2  -   I  -
                                          ERL Great Lakes Pollution Studies            4  2   3  -  -   3  -  I   -  -
                                          Sea Grant Ocean Pollution Program          43   6 14   1  8   611   1   1  2
                                          National Fishery Ecology Program           23   8 12   -  7   517   1   5  2
                                          Microconstituents Program                    5  3   4  - - -     2  - - -
                                          Financial Assistance Program                 6  1   3  -  -   1  1  -   1
                                          Long Range Effects Research Program          5  -   3  - - -     2  -   -
                                          Ocean Pollution Monitoring Program           2  2   2  -  1   -  I  -   1  1
                                          Ocean Dumping Program                      11   -   6  - - -     7  -   -
                                          Marine Ecosystems Analysis Program           9  2   7  -  4   4  3  -   -
                                          Hudson-Raritan Estuary Project               2  -   1  - - -     2  - - -
                                          Puget Sound Project                          2  1   - - - -      2  -   -  -

                                     DOD/ACOE-Environmental Quality Program            3  -   1  -  -   1  1  -   3  -
                                               Development and Monitoring Program      9  - - - - - - -           9  -

                                     DOD/Navy-Environment Protection Technology        I  - - - - -        1

                                     DOE- Ocean Thermal Energy Conversion Prog.        4  -   -  1  - - -
                                          Regional Marine Program                    23   2   2  -  1   5  7  5   -  7
                                          Radioecology Program                         9  - - - - - -         9   -  -
                                          Physiological Ecology Program                3  2   - - -     1  3  - - -
                                          Strategic Petroleum Reserve Program          2  - - - -       2  1  -   1  2
                                          Subseabed Disposal Program                   1  - - - - - -         I   -  I
                                          Estuarine Program                            6  1   - - -     1  4  2   2
                                          Stable and Radioactive Elements Prog.        3  - - - - - -         3   -
                                          oil and Gas Program                          2  2   - - - - - - - -
                                          Cooling Systems Program                      1  - - - - - - - -            1

                                     HHS/NIEHS-Extramural Grant Program                3  1   2  - - -     3  - - -

                                     HHS/FDA-Shellfish Sanitation Program              2  1   1  -  2   1  1  -   1  -

                                     DOI/MMS-Washington, D.C. Office Studies           4  4   - - - -      2  - - -
                                              Atlantic OCS Regional Studies            6  5   - - -     I  -  -   1  1
                                              Gulf of Mexico OCS Regional Studies      2  2   - - - - - - -          2
                                              Pacific OCS Regional Studies             3  2   -  -  1   1  - - -     I
                                              Alaska OCS Regional Studies            12  12   1  -  2   - - - - -

                                     DOI/FWS- Fishery Resources Program                5  -   4  -  -   3  3      1
                                               Habitat Resources Program               2  - - - -       I  1      1
                                               Env. Contaminants Eval. Program         6  1   6  - - -     5  - - -

                                     DOI/USGS- Water Resources Division Program      15   -   5  -  1   8  8  -   5  4
                                                Geologic Division Program              6  3   - - - -      4  -   2  1

                                     DOT/USCG-Port and Env. Safety Program             1  1   - - - - - - - -
                                               Marine Env. Response Program            5  5   2  - - -     I  -

                                     EPA- Marine Waste Disposal Program              11   1   2  -  3   -  3  -   &  4
                                          Energy Related Research Program              4  3   - - - -      1  -   -  1
                                          Water Quality Research Program               3  -   2  -  -   I  I  -   1  1
                                          Great Lakes Research Program               41   - 24   -  6  19 25  1   3  -
                                          Chesapeake Bay Program                     15   -   7  -  -   7  9  -   4  -
                                          Exploratory Research Program                 6  3   3  -  -   1  3  3   1  -
                                          Marine Ecology Studies Program               7  2   6  -  -   2  4  -   2  -
                                          Energy-Environment Interagency      Prog.    5  5   - - - -      I  -   -  -
                                          Evaluation of Radioactive Waste Prog.        1  - - - - - -         1   -  -
                                          Ocean Dump Site Evaluation Program           1  -   1  -  -   1  1  - - -

                                     NSF- Division of Ocean Science                    7  1   1  -  -   1  4  -   -  1
                                          Chemical oceanography Program                3  1   1  -  -   2  2  1   2  -
                                          Biological oceanography Program              3  - - - -       3  -  -   3  -

                                     NRC- Environmental Impact Assessment     Res.     3  -   -  1  -   -  2  -   -  1

                                     NPS- National Park Service Program                1  - - - -       I  -  -   1  -

                                                                            620

                                                                TABLE 4

                                           Regional Distribution of Potential Data Activities

                                Department/Agency-Program                    Total    Regional Count
                                                                             Proj. NE SE GM SW NW AK GL US
                                ------------------------------------------------------------------------

                                USDA-Effects of Agricultural Practices Program 5     1  3  - - - - -

                                NOAA-Coastal and Estuarine Assessment Program 15     5  -  2  2    4 1  1
                                     Ocean Use Impact Program                     4  2  1  1  - - -     1
                                     Deep Seabed Mining Environmental Research 3     - - -    3    - - - -
                                     National Marine Sanctuaries Program          1  -  I  - - - - - -
                                     ERL Ocean Pollution Studies Program          3  -  -  1  -    1,-  -  1
                                     ERL Great Lakes Pollution Studies Program    4  - - - - - -        4  -
                                     Sea Grant Ocean Pollution Program          43   8  4  7  4    1 1 17  2
                                     National Fishery Ecology Program           23   9  3  7  1    4 3  -  -
                                     Microconstituents Program                    5  1  2  1  -    1 -  -  1
                                     Financial Assistance Program                 6  1  1  1  1    - -  2  -
                                     Long Range Effect Research Program           5  2  -  1  2    - - - -
                                     Ocean Pollution Monitoring Program           2  2  - - - - - - -
                                     Ocean Dumping Program                      11   6  5  -  -    I - - -
                                     Marine Ecosystem Analysis Program            9  9  - - - - - - -
                                     Hudson-Raritan Estuary Project               2  2  - - - - - - -
                                     Puget Sound Project                          2  - - - -       2 -  -  -

                                DOD/ACOE-Environmental Quality Program            3  - - - - - - -         3
                                         Development and Monitoring Program       9  1  1  1  2    1.-  2  1

                                DOD/Navy-Environmental Protection Technology      1  - - - - - - -         1

                                DOE- Ocean Thermal Energy Conversion Program      4  -  2  1  1    - - -   1
                                     Regional Marine Program                    23   5  5  -  2    6 -  2  3
                                     Radioecology Program                         9  2  1  1  2    2 -  -  1
                                     Physiological Ecology Program                3  - - - -       2 -  -  1
                                     Strategic Petroleum Reserve Program          2  -  -  2  - - - - -
                                     Subseabed Disposal Program                   1  - - - - - - -         1
                                     Estuarine Program                            6  2  2  - - -     1  -  1
                                     Stable and Radioactive Elements Program      3  - - -    1    -       2
                                     Oil and Gas Program                          2  1  -  -  1    - - - -
                                     Cooling Systems Program                      1  1  - - - - - - -

                                HHS/NIEHS-Extramural Grant Program                3  - - - -       1       2

                                HHS/FDA-Shellfish Sanitation Program              2  -  -  1

                                DOI/MMS-Washington, D.C. Office Studies           4  1  1  1  - - - -      3
                                        Atlantic OCS Regional Studies Program     6  4  3  - - - - - -
                                        Gulf of Mexico OCS Regional Studies       2  -  -  2  -    - -  -  -
                                        Pacific OCS Regional Studies Program      3  -  -  -  3    - - - -
                                        Alaska OCS Regional Studies Program     12   - - - - -     12   -  -

                                DOI/FWS- Fishery Resources Program                5  - - - - - -        5  -
                                         Habitat Resources Program                2  - - - - - -        2  -
                                         Env. Contaminants Eval. Program          6  2  1  - - - -      2  2

                                DOI/USGS- Water Resources Division Program      15   4  3  1  3    - -  1  3
                                          Geologic Division Program               6  1  1  2  1    1 1  -  2

                                DOT/USCG-Port and Environmental Safety Program    I  - - - - - - -         1
                                         Marine Environmental Response Program    5  - - - - - - -         5

                                EPA- Marine Waste Disposal Program              11   4  2  -  2    2       1
                                     Energy Related Research Program              4  - - -    1    1       2
                                     Water Quality Research Program               3  -  -  I  -    1       1
                                     Great Lakes Research Program               41   - - - - - -       41  -
                                     Chesapeake Bay Program                     15  15  - - - - - - -
                                     Exploratory Research Program                 6  - - - -       1 -  -  5
                                     Marine Ecology Studies Program               7  -  -  1  -    5 -  -  I
                                     Energy-Environment Interagency  Program      5  -  -  1  1    1 -  -  2
                                     Evaluation of Radioactive Waste Program      I  I  -  1  1    - - - -
                                     Ocean Dump Site Evaluation Program           1  - - - - - - -         I

                                NSF- Division of Ocean science                    7  - - -    1    1       6
                                     chemical oceanography Program                3  - - - - - - -         3
                                     Biological Oceanography Program              3  - - - - - -        1  2

                                NRC- Environmental Impact Assessment  Research    3  - - - - - - -         3

                                NPS- National Park Service Program                1  - 1   - - - - - -

                                                                    621

                               REFERENCES                           COPRDM.      1983. Catalog       of    Federal
                                                                    Projects, IY 1982 Updat           pendix 2 to
                                                                    the Federal Plan for Ocean Pollution
               COPRDM. 1978. Catalog of Federal Re-                 Research, Development, and Monitoring
               search,    Development     and     Monitoring        Interagency Committee on Ocean Pollution
               Programs     for Fiscal Years         1978-80.       Research, Development, and Monitoring,
               Interagency Committee on Ocean Pollution             Federal      Coordinating     Council       for
               Research, Development, and Monitoring,               science, Engineering and Technology).
               Federal      Coordinating      Council      for
               Science, Engineering and Technology).                COPRDM.      1984. Catalog       of    Federal
                                                                    Projects, EY 1983 Update, A-p-pendix 2 to
               COPRDM. 1979. Catalog of Ocean Pollution             the Federal Plan for Ocean Pollution
               Research,     Development and Monitoring             Resea-rch, Development, and Monitoring.
               Programs     for Fiscal Years         1978-80.       Interagency Committee on Ocean Pollution
               Fqorking Paper I  for tHe fe-deral @;_Ian for        Research, Development, and Monitoring,
               Ocean Pollution Research, Development,               Federal      Coordinating     council       for
               and Monitoring.   Interagency Committee on           Science, Engineering and Technology).
               Ocean Pollution Research, Development,
               and Monitoring,       Federal Coordinating           NMPPO.     1985a. Catalog        of    Federal
               Council for Science, Engineering and                 Projects, FY 1984 Update, Appendix 2 to
               Technology).                                         the Federal Plan for Ocean Pollution
                                                                    Research, Development, and Monitoring.
               COPRDM.    1981.     Catalog    of    Federal        National     Marine       Pollution    Program
               Projects, LY-1980 Update, Appendix 2 to              Office, NOAA.
               the Federal Plan for Ocean Pollution
               Research, Development, and Monitorin .               NMPPO. 1985b. National Marine Pollution
               Interagency Committee on Ocean Pollution             Program:      Federal      Plan   for     Ocean
               Research, Development, and Monitoring,               Pollution     Resea-rch,    Development,       &
               Federal      Coordinating      Council      for      Monitoring    -- Fiscal Years 1985-1989.
               Science, Engineering and Technology).                Prepared      E-y   the    National      Marine
                                                                    Pollution     Program      Office   for     the
               COPRDM.      1982. Catalog      of    Federal        Interagency        Committee     for      Ocean
               Projects,    fY 1981 Update, Appendix 2 to           Pollution Research,        Development, and
               the Federal Plan for Ocean Pollution                 monitoring.
               Research, Development, and Monitorin
               Interagency Committee on Ocean Pollution             NMPPO.     1985c. Summary   I    of    Federal
               Research, Development, and Monitoring,               Programs and Projects, F          985  Update,
               Federal      Coordinating      Council      for      National      Marine      PoliTt-i-on  Program
               Science, Engineering and Technology).                Office, NOAA.

                                                                  622

                                            THE USE OF WORM OPTICAL DISKS
                                                  IN OCEAN SYSTEMS

                                      Dennis Stamulis and Michael P. Shevenell

                                        Marine Systems Engineering Laboratory
                                             University of New Hampshire
                                              Durham, New Hampshire 03824

                               ABSTRACT                        many sensors must be packaged in small
                                                               cylindrical pressure housings, size must
             The need for large amounts of non-volatile        be kept to a minimum.       The need f or a
             storage has led the Marine Systems                robust removal media is critical because
             Engineering Laboratory to consider the use        it is often impossible or impractical to;
             of WORM (Write once Read Many) optical            transport the entire instrument. Instead,'
             disks for data and program storage.               only the medium is removed and transported
             Although optical disks have the capability        to the lab for data analysis.
             to store huge amounts of data (e.g. 800
             Mbytes), being a write once medium                The capabilities of present WORM optical
             presents some interesting file management         disks meet all the criterion expressed for
             problems.                                         high   density,     non-volatile      removal
                                                               oceanographic storage.    There are myriads
             This paper presents t    Ihe system design        of  uses    for   current    optical     disk
             which includes a file, system, hardware           technology; these include: bathemetric
             interface, and performance measures. A'           surveys, current profiling, water column
             unique feature of the file management             measurements, side scan sonar and digital
             system allows multiple asynchronous files         image storage.   Although a single digital
             to be written.    In addition single files        image may contain a large amount of data
             are handled efficiently by utilizing the          (256k bytes for a 512 x 512.pixel image)
             large buffer and high transfer rate of the        over 1500 images can be stored on one side
             disk controller.    The disk is interfaced        of an optical disk.
             to the development system running Unix as
             well as the run time system running PSOS,         The application which has driven the
             a commercial real-time operating system.          Marine Systems Engineering Laboratory
             This scheme which is used on EAVE, an             (MSEL) at the University of New Hampshire
             underwater autonomous vehicle and can be          is the EAVE AUV research and development
             applied to data collection by the ocean           program.    The development of intelligent
             community.                                      .,autonomous vehicles has seen a great
                                                               increase in the complexity and size of
                                                               code to perform useful tasks. As the code
                                                               size increased, field downloading became
                           I. INTRODUCTION                     impractical with previous methods. As an
                                                               example,     a    LISP-based      processing
             As more advanced systems and sensors are          environment requires over 2 Mbytes of data
             used in oceanographic data collection, the        storage.    In addition, as more complex
             demand for high density data storage              missions are performed the need for large
             increases.     An example of this data            data storage increases.
             explosion is shown in the digital storing
             of side scan sonar data. Assuming a side                           2. HARDWARE
             scan sonar with two channels each having a
             bandwidth of lOkHz produces 40k bytes per         As mentioned, the integration of a WORM
             second when the samples are   digitized to 8      optical disk comes in the context of the
             bits, a single hour of        digital data        EAVE    autonomous     vehicle      program.
             collection would require     144M bytes of        specifically, the disk has become part of
             storage.                                          the     MSEL   Knowledge-Based        Control
                                                               Architecture based on the VME bus (see
                                                               Figure 1). The disk interfaces to the VME
             in addition to the high data capacity             bus System Controller board which contains
             required in present oceanographic data            an industry standard Small Computer
             systems, small size is desirable.       since     Systems Interface      (SCSI)   port.       In

                                              CH2585-8/88/0000- 623 $1 @1988 IEEE

               addition to the SCSI port, the System              traditional method of updating lists could
               Controller board has special hardware and          not be implemented.
               a DMA controller to perform fast data
               transfers without requiring a CPU to               This file system is essentially a one
               handle the data. As shown in Table 1, the          level hierarchical system that contains.
               maximum data transfer rate of the disk             four types of blocks: a super inode (SIN),
               drive is 1.0 Mbytes per second; this data          a file inode (FIN) , a directory inode
               rate is easily handled by the DMA                  (DIN),, and a data block (DB) (see Figure
               hardware.                                          2).   Special information such as a time
                                                                  stamp,    and   date/time     of     creation
               There are presently several manufacturers          identifies the particular optical disk
               of high capacity WORM optical disk drives.         being used and is stored in the SIN.
               At the start of this project Maxtor was            There is only one SIN assigned to each
               selected as the vendor because it offered          side of an optical disk and is always
               the highest capacity in the 5 .1/4 inch            block number 191951, the highest numbered
               form factor and had an embedded SCSI               block on the    optical disk.     Information
               controller.     The model    chosen is the         about a file, its name, time of creation,
               Maxtor RXT-800S which has     400 Mbytes of        a pointer to its f irst block of data,
               formatted storage per side   of the media.         etc., is stored in the FIN.      The size of
                                                                  the file in bytes may or may not be stored
                                  TABLE 1                         depending on which write mode was used
                 Selected Maxtor RXT-800S   Specifications        (this will be explained later) .     The DIN
                                                                  is unique in that it stores all the
               Capacity                 800 Mbytes                information held in     the previous twenty
               Average Seek Time        108 milliseconds          FIDs.   Finally, the DB contains a byte
               Peak Power               5v 1.3A                   count, a pointer to the next DB used, and
                                        12v 3.5A                  the actual file data being stored.
                                                                  Included in this scheme is a special file
               SCSI transfer rate       1.0 Mbytes/sec            (OSTAT) stored on the host winchester disk
               Disk transfer rate       2.5 Mbits/sec             that contains information pertaining to
               Operating Shock          2G @11 milliseconds       the state of the optical disk currently
                                                                  being used.   Each optical disk used must
               Data Reliability         <1 error in 10-12         first be initialized. This initialization
               Data Life                >5 years                  process writes a time stamp and other
               Dimensions               Width 5.75 in             optical disk identifying information to
                                        Depth 8.00 in             the SIN and to the f ile OSTAT.        Besides
                                        Height 3.25 in            containing    the    same    optical      disk
                                                                  identifying information found in the SIN,
                            3. THE FILE SYSTEM                    five pieces of state information are
                                                                  needed to be stored in      OSTAT for each
               During the design of the file system               optical disk in use. They are:
               structure three requirements had to be
               addressed: compatibility, speed, and                9 The block number of the   last written
               simplicity. A file system would not only              DIN.
               need to run under UNIX, but be easily
               ported to run on the EAVE vehicle under.            9 The block number of the   next free FIN.
               its own operating system PSOS.     Since the
               optical disk would be used to download              9 The block number of the   next free DB.
               large amounts of code to the vehicle in
               the field, optimizing the read/write                e The number of DINs written.
               commands to the disk was essential.
               Lastly, keeping the structure simple                e The number of FINs written since the
               enhances the speed, allows for easy                   last written DIN. This implies that
               maintenance, and assures the size of the              each optical disk initialized is a new
               executable will be reasonable. The size of            entry in the host file OSTAT.
               the    executable      is . an      important
               consideration since the vehicle has a                        5. READING AND WRITING
               finitememory.
                                                                  As mentioned above, the optical disk is
                     4. THE FILE SYSTEM ORGANIZATION              composed of contiguous blocks numbered 0
                                                                  to 191951 with the largest numbered block
               Each side of the optical disk- is a                designated the SIN.    In this scheme, FINs
               contiguous set of indivisible blocks, 2048         and DINs are allocated from block number
               bytes in length, and numbered from 0 to            191950 decrementing towards lower numbered
               191951. Blocks may be written only once            blocks ' and DBs are allocated starting
               but read as many times as needed. It would         from block number 0 incrementing towards
               be an error to attempt to read an                  higher numbered blocks as needed. Anytime
               unwritten block or attempt to write to a           an operation is to be performed on an
               used   one.       Because   of   this,     the     optical disk, its SIN is read and the

                                                             624

           OSTAT file is searched in order to find a        FINs that have not yet been wri    tten to a
           matching entry. This procedure verifies          DIN - nineteen at most. If the named file
           that the disk has indeed been initialized        has not been found, only the remaining
           and its state information has been entered       DINs need to be searched since only they
           in OSTAT.                                        contain information about twenty files
                                                            previously written.     Searches are always
           There are two specific write modes that.         performed in such a manner to insure only
           can be applied when writing to the an            the most current version of duplicate
           optical disk, the linked list (LL) mode          named files will be located first. Using a.
           and the sequential (SQ) mode.     When a new     file's FIN only requires one optical disk
           file is to be written, all pertinent file        access to find where the file resides on
           information is entered into the next free        that disk. This option was needed to
           SIN, including a pointer to the next free        provide for reading any version of a
           DB.     If the file to be written is             duplicate named files. It should be noted
           redirected from standard input, the write        that when reading, a file would be
           routine cannot determine in advance the          accessed in the same mode it was written.
           actual size of the file, and therefore           If it was written using the LL mode it
           cannot include the f ile size as part of         must be read one block at a time.
           the FIN.   In this case, a zero file size        Otherwise, it may also take advantage of
           is entered in FIN to record that the LL          the size of optical disk controller
           write mode was used. This LL mode causes         transfer buffer and read up to its maximum
           one disk block to be written at a time           size for each disk access.
           with each new DB written to the optical
           disk pointing to the next free DB. If the
           new f ile to be    written is given on the                     6. UNIX VS. PSOS
           command line as an argument to the write
           program, the size of the file can be             This file     system and its associated
           predetermined before the FIN is written to       routines are compatible so they run under
           the optical disk and is included as part         both UNIX and PSOS, the EAVE vehicle's
           of the file information stored there.      In    operating system.    It is an ideal, method
           this SQ mode the number of DBs needed can        to download large amounts of code from our
           be determined in advance enabling each           development system to the EAVE vehicle.
           write to the disk to be up to the maximum        First, code is written to an optical'disk.
           size of the optical disk controller              Then, after completion of data transfer
           transfer buffer (i.e. 62 blocks of data).        the disk is removed and then installed in
           After a file has been completely written         the optical disk drive of the EAVE
           to the optical disk, if       the number of      vehicle.    The vehicle is booted and the
           FINs written is equivalent to twenty, a          code on the optical disk is loaded into
           DIN containing all information recorded in       the vehicle's RAM and executed. Both the
           the previous twenty FINs is written to the       above writing and reading are done in SQ
           next free FIN location. At this time, if         mode to insure that writing and reading
           a previous FIN has a 0 byte count, it must       will be done as fast as possible.
           have been written in LL mode and its links       However, when the vehicle is actually
           would be traced, byte count calculated,          performing a mission and storing data, all
           and then recorded in its corresponding           writing is  done via the LL mode. All data
           entry in the DIN.       A special code is        recorded   is a continuous stream and
           entered in the DIN for each file that has        emanating  f rom, many sources on the EAVE
           been written in SQ mode so that any              vehicle.
           reading of files can also take advantage
           of the size of the optical disk controller                   7. THE BOOT SEQUENCE
           transfer buffer.
                                                            Activating  the prommed boot code on the
           Each access to the    optical disk must be       EAVE vehicle is a simple matter of
           preceded by the four basic SCSI phases:          entering 11BU11 on the active terminal after
           select, command, data transfer (if any),         a reset has been initiated.     The program
           and status.    It can be seen that the LL        will then prompt for a SIN number and,
           mode is inefficient since the four SCSI          once given, will read the proper code into
           phases must be executed for each block           RAM and execute it. At this time a Master
           written. However, it does provide a means        Console (MASCON) program will be up and
           of    writing    multiple     open     files.    running.   This program is similar to the
           Conversely the SQ mode needs to execute          UNIX shell in that it allows the user to
           the four basic SCSI phases only once per         execute certain useful commands.. one of
           each 62 blocks transferred.                      these commands brings up other -modules
                                                            necessary for vehicle operation. This
           A read operation can also be performed in        command loads each modules' image from the
           one of two ways, searching   for the file by     optical disk and then executes it.
           its name, or accessing it by using its FIN
           number.    When searching for a file by
           name, it  is only necessary to scan those

                                                         625

                        8. SYSTEM PERFORMANCE

              Preliminary performance measurements have
              been made using a VME bus based 68020 CPU
              board handling the data transfer in a
              programmed 1/0 mode. The DMA mode of data
              transfer has not yet been implemented.
              The results of these tests show the
              transfer rate for a large sequential block
              file to be about 75 kbytes per second.
              Although the DMA controlled will handle
              data at speeds approaching 1 Mbyte/second,
              the programmed 1/0 transfer rate may be
              sufficient for many applications.

                             9. CONCLUSION

              The experience at the Marine Systems
              Engineering Laboratory has shown the WORM
              optical disk to be a vital piece of
              technology to be include in oceanographic
              data systems as well as advanced
              autonomous vehicles.    The unit provides
              high density, non-volatile removal storage
              at low cost (a typical unit costs about
              $2000 with media costing $100 for 800
              Mbytes).

              This file system has proven to be
              portable, simple, and flexible, running
              under UNIX host as well as PSOS; the EAVE
              vehicle operating system. It can be used
              to download code from one system to
              another in a fast and efficient manner.
              For use in the f ield, it is     a greatly
              improved method for data collection since
              the data collection medium can be
              transferred to another system where that
              data can be easily analyzed.

                            10. REFERENCES

              1. Gait, Jason, "The optical File Cabinet:
                 A Random-Access File System for Write-
                 once Optical Disks", IEEE Computer,
                 June 1988, pp. 11-22.

              2. Shevenell, Michael P. "Hardware and
                 Software Architectures for Realizing a
                 Knowledge Based System on EAVE11, Fifth
                 International Symposium on Unmanned
                 Untethered Submersible Technology,
                 Marine Systems Engineering Laboratory,
                 UNH, Durham, NH, pp. 220-237.
              3. "A cooperative Research Project on
                 Intelligent Control for Multiple
                 Autonomous Undersea Vehicles", MSEL
                 Report    #88-03,     Marine     Systems
                 Engineering Laboratory, UNH, Durham,
                 NH.

              4. "Maxtor RXT-800S Product Specification
                 and OEM Manual", Maxtor Corp. San Jose,
                 CA. "NCR 5380-53CSO SCSI Interface Chip
                 Design Manual", NCR Microelectronics
                 Division,    Colorado    springs,    CO.
                 "Ironics   IV-3273    VME  bus    System
                 Controller Users Manual", Ironics Inc.,
                 Ithaca, NY.

                                                          626

                                                VME BUS

                                       -1 F
                 SIMTW        68020                  68010      68020      4M RAM      68020
                              m                    256K RAM
                 CNTRL          P                   8 SERIAL   4M RAM                  4M RAM

                              DATA      GUIDANCE               SITUATION              SUPERVISOR
                           ASSESSNM                           ASSESSMENT               PLANNER

                                             IWSEL BUS 68000 COMPUTERS

                                     TOP LEVEL ARCHITECTURE

                                                  FIGURE 1.
                                                   @
                                                     6
                                                   25 6

                              DAT
                             SESS
                          @AS

                                                     627

                              191951                                    SIN

                              191950                                    FIN

                              191949                                    FIN

                                                                          0

                                                                          0

                              191931                                    FIN

                              191930                                    DIN

                              191929                                    FIN

                                  4                   Byte              DB                LINK
                                                     Count
                                                      Byte                                LINK
                                  3                  Count              DB

                                                      Byte
                                  2                   Count             DB                LINK

                                                      Byte
                                  1                   Count             DB                LINK
                                  0                    Byte             D                 LINK
                                                      Count               B

                               OPTICAL DISK FILE SYSTEM FORMAT

                                                           FIGURE 2.

                                                              628

                                                                   A METHOD FOR OPTIMIZING
                                                   ENVIRONMENTAL OBSERVING NETWORKS

                                                                                          W. Brett Wilson

                                                                             National Data Buoy Center (NDBQ
                                                                            Stennis Space Center, MS 39529-6000

                                                  ABSTRA CT                                              understood, can lead to improper conclusions. Among these are: 1) the
                                                                                                         need to properly develop the input data and interpret the results for ap-
                   Linear programming techniques, based on calculus of variations, have                  plicability and reasonableness, and 2) the need to understand the restric-
                   Proven useful in a variety of disciplines for optimizing multi-attribute              tions inherent in the techique, such as the linearity assumptions in linear
                   objective functions subject to constraints. Thispaper documents the ap-               programming.
                   plication of linear programming to the problem of designing an en-
                   vironmental observing network consisting of multiple sensor and plat-                 In 1988, an independent project to create such a numerical model was
                   form systems in light of budget and other limitations.                                initiated.

                   An environmental observing network optimization numerical model,
                   developed by the author at NDBC, is described, and its strengths and                         2. OBSERVING NETWORK OPTIMIZATION
                   limitations discussed. An example numerical model case study is described                                    NUMERICAL MODEL
                   and evaluated. The value to the planner of the model and its output is
                   also assessed.                                                                        The numerical model OPTNET I was developed by the author, in the spring
                                                                                                         of 1988 using the BASIC language on an IBM PC-AT. The model is bas-
                                                                                                         ed on the linear programming technique derived from calculus of varia-
                                                                                                         tions. The technique, which is described in [2] as well as other sources,
                                            1. INTRODUCTION                                              optimizes an objective function subject to constraints. In OPTNETI, the
                                                                                                         objective function is the maximization of network "utility" or value for
                   One of the difficulties facing meteorologists, oceanographers, and other              a network composed of multiple system types. The constraints may in-
                   geophysical scientists is the acquisition of field observations within the            clude limits on the quantities of individual systems, initial and recurring
                   limits of available technology, the constraints imposed by the infrastruc-            budget limits for individual systems, and intitial, recurring, and total (both
                   ture of logistics, maintenance, communications, and data quality                      present value and nondiscounted) expenditure limits for the network over
                   assurance, and the restrictions of budget. The issue of the optimal alloca-           its life. Figure I depicts the components of the utility function that must
                   tion of resources is important for operational environmental observing                be input separately for each system, as well as the input for system cost
                   programs as well as experiments, for both short- and long-term observa-               data and system and network constraints.
                   tional projects, and for programs of local concern in addition to those
                   of global extent. The types of observing systems to, he operated, their               The utility of an observing system may be evaluated from the perspec-
                   particular sensor capabilities, and the quantities of 'systems, etc., are             tive of a numerical modeler (involved in operational numerical weather
                   several of the "questions" that must be resolved. Where observing systems             or oceanographic predictions, typically on the synoptic and mesoscales);
                   of varying capability are already in place, such considerations may in-               a forecaster (involved in issuing forecasts on the local or regional scales);
                   clude the deactivation of existing systems, the modification and enhance-             and a climate researcher (involved in investigating climatic anomalies
                   ment of selected existing systems, and the installation of entirely new               through modeling or statistical studies, primarily on the global scale).
                   equipment.                                                                            The program allows the input of a weighting factor for each of the above
                                                                                                         three user categories to reflect the objective of the observing network (e.g.,
                   Typically, the composition of an observing network is determined by                   in the example case that follows, primarily for forecasters and secondarily
                   negotiation between the various principals involved-the scientists, plan-             for climate researchers). OPTNETI also requests for each user-system
                   ners, engineers, technicians, equipment suppliers, accountants, and, in               combination the following:
                   some cases, politicians and lawyers. This process is complex and not in-              I . Ideal coverage factors and corresponding weighting factors for meso,
                   frequently time-consuming, but does generally result in networks that                     synoptic, and global scales
                   achieve an acceptable level of the principals' objectives. In many situa-             2.  The utilities and weighting factors for the following characteristics
                   tions, the negotiation of requirements, solutions, and budgets, despite                   eParameters sensed
                   its lack of analyticity, is essential to the success of the program. However,             *Reporting frequency
                   under certain conditions, it is conceivable that analytical techniques could              *Timeliness of reporting (the time interval from data acquisition to
                   be effectively employed to define the composition of optimum observing                     receipt by the user)
                   networks as an aid to the network planning process. These techniques,                     *Data quality (the adequacy of the data quality assurance methods)
                   which are derived from the field of operations research, can be very useful               *Data continuity (the continuity of the observation from a given
                   to the planner, scientist, or engineer, who must either formulate and ex-                  location over the network life)
                   ecute the observing network program plan or recommend it to some ap-                      9System performance (end-to-end reliability and data through-put).
                   proving authority. In general, optimization techniques are intended to                The weighting factors enable each user to place different priorities on
                   supplement the planning and negotiation process, and not replace it                   the characteristics of each system.
                   altogether. Since optimization methods, such as linear programming, are
                   intended for computer application, they offer the network planner a                   For the linear programming method to work, the premise of linearity in
                   number of advantages, among which are: 1) the quantification of benefits              an operations research sense must hold true. This means that economies
                   (as well as costs); 2) the ability to investigate a large number of candidate         of scale either do not exist or are negligible with respect to both the costs
                   network configurations and assess the corresponding effects of changes                and the utility of the systems in the network. In other words, the change
                   in requirements or budget (sensitivity analysis); 3) the capability to                in network utility and costs must be invariant of the quantity of systems
                   analytically determine the optimum solutions in terms of benefits versus              or show decreasing returns to scale. Similarly, the utility assessments must
                   costs; and 4) the ability to do 1, 2, and 3 above quickly and efficiently.            remain functionally independent in order for the multi-attribute utility
                   Numerical optimization models also have limitations that, if not                      function to be developed. For example, the utility of the TIMELINESS

                                                                                                  629    United States Government work not protected by copyright

                              SYSTEM NO                                                                       budgetary and other constraints. The output includes the quantities of
                                                                                                              the systems in the optimum network, a listing of the slack on the con-
                                                                                                              straints (non-zero values where a constraint is not binding, i.e., where
                                                                                                              that particular limit has not been reached), and the shadow prices on the
                                                                                                              constraints (the amount the objective function would be improved if the
                                                                                                              binding constraint or constraints were to be relaxed one unit).

                                                                                                                          3. EXAMPLE NETWORK ANALYSIS

                                                                                                              An example analysis using OPTNETI was performed for an imaginary
                                                                                                              data-void marine region in which surface observations were required. Four
                     ??USER WEIGHT                                                                            types of observing systems were assumed to be available: moored buoys,
                          FACTOR??             ??UWF??                     F??        EUWF= 100               Coastal-Marine Automated Network (C-MAN) stations, drifting buoys,
                                                                                                              and simplified, meteorological-parameters-only Shipboard Environmental
                                                                                                              Data Acquisition Systems (SEAS). Costs, utility considerations, and con-
                                                                                                              straints were assumed as shown in Table 1 (note the constraints on the
                          COVERAGE                                                                            number of systems, which can be considered as either hardware availability
                                                                                                              limits or other restrictions on the availability of suitable installation sites).
                                                                                                              The input values for costs and utilities were estimated by the author and
                          ??MESOSCALE         ??SYNOPTIC             @'@'GT"O'RA?.',
                          FACTOR??             FACTOR??                               1-100 EACH              Table 1. Input Cons     Iiderationsfor Example Marine Observing Network
                                                                                                                         Optimization Study
                          ??WEIGHT??                                                  EWEIGHTS=100
                                                                                                                USERS AND WEIGHTING FACTORS
                                                                                                                  1. FORECASTER - 75
                                                                                                                  2. CLIMATE RESEARCHER - 25
                          SYSTEM CHARACTERISTICS                                                                  3. MODELER - 0
                                                                                                                USER                                       FORECASTER          CLIMATE
                                                                                                                                                                               RESEARCHER
                          ??UTILITIES (1-100 EACH) FOR:         ??CORRESPONDING                                 COVERAGE WEIGHTING FACTOR
                          � SENSED PARAMETERS                  WEIGHTS E        100??
                          � REPORTING FREQUENCY                                                                   MESO                                     HIGH                LOW
                          � TIMELINESS OF REPORTING                                                               SYNOPTIC                                 MODERATE            MODERATE
                          � DATA QUALITY                                                                          GLOBAL                                   VERY LOW            HIGH
                          � DATA CONTINUITY                                                                     SYSTEM CHARACTERISTICS
                          � SYSTEM PERFORMANCE??                                                                WEIGHTING FACTORS
                                                                                                                  PARAMETERS                               HIGH                HIGHEST
                                                                                                                  REPORTING FREQUENCY                      HIGH                LOW
                                                                                                                  TIMELINESS                               HIGH                LOWEST
                                                                                                                  DATA QUALITY                             MODERATE            MODERATE
                     TI-TS9                                                                                       DATA CONTINUITY                          LOWEST              MODERATE
                          ??e FIRST-YEAR COSTS PER UNIT                                                       I   PERFORMANCE                              LOW               I LOW             I
                            RECURRING COSTS PER UNIT?

                          SYSTEM CONST AINTS                                                                    SYSTEM TYPE                   MOORED    DRIFTING       SEAS*        C-MAN
                                                                                                                                              BUOY      BUOY
                          ??* MAXIMUM QUANTITY OF SYSTEMS                                                       COVERAGE
                          9 TOTAL INITIAL COST FOR SYSTEMS OF TYPE                                                MESO                        HIGH      MODERATE       LOW          MODERATE
                          e TOTAL RECURRING COSTS FOR SYSTEMS OF TYPE??                                           SYNOPTIC                    HIGH      MODERATE       MODERATE     MODERATE
                                                                                                                  GLOBAL                      GOOD      MODERATE       MODERATE I MODERATE
                          - - - - - - - - - - - -                                                               UTILITIES
                          ETWORK CONSTRAINTS                                                                      PARAMETERS                  HIGH      MODERATE       VERY LOW     HIGH
                                                                                                                  REPORTING FREQUENCY         HIGH      LOW            MODERATE     HIGH
                                                                                                                  TIMELINESS                  HIGH      MODERATE       GOOD         HIGH
                          ??* NETWORK LIFE                                                                        DATA QUALITY                HIGH      MODERATE       VERY LOW     HIGH
                          � COST OF MONEY                                                                         DATA CONTINUITY             HIGH      LOW            VERY  LOW    HIGH
                          � NETWORK INITIAL COST CONSTRAINT                                                       PERFORMANCE                 GOOD      MODERATE, GOOD              HIGH
                          � NETWORK RECURRING COST CONSTRAINT                                                   SYSTEM UTILITY
                          � NETWORK TOTAL LIFETIME EXPENDITURE CONSTRAINT                                                                     79.5      37.7           20.1         46.8
                          � NETWORK TOTAL PRESENT VALUE CONSTRAINT??                                            (NONDIMENSIONAL)
                                                                                                                COSTS,$K
                     NOTE: INPUT INDICATED BY                                                                     INITIAL                     50        15             20           35
                                                                                                                  RECURRING                   25        15             5            12.5
                     Figure.l. OPTNET Input                                                                     CONSTRAINT ON                 to        40             25         1-7
                                                                                                              @,GUMTITY-OF-SYSTEMS
                     of an observation is assumed to be unaffected by the utility of any other
                     system characteristic, such as REPORTING FREQUENCY or DATA
                     QUALITY.                                                                                   NETWORK LIFE - 5 YEARS
                                                                                                                NETWORK TOTAL EXPENDITURE CONSTRAINT - $5,000,000
                     Based on the utility, cost, and constraint input, OPTNET 1 solves the                    *HYPOTHETICAL SEAS EQUIPMENT, NOT NECESSARILY SIMILAR IN
                     linear programming problem of maximizing network utility subject to                        CAPABILITY OR COST TO NATIONAL OCEAN SERVICE SEAS SYSTEMS.

                                                                                                         630

                   do not necessarily represent expert judgment-rathe'r, they are believed                                           4. CONCLUSION
                   to be generally representative values intended for an example case study.              An analysis of an example marine surface observing n6twork using a linear
                   The results are shown in Figure 2, where the quantities of systems in the              programming optimization numerical model has been conducted. The
                   optimum network are plotted against the initial year budget constraint                 analysis demonstrates the capability and effectiveness of the linear pro-
                   (for a fixed 5-year total expenditure of $5,000,000 and equal recurring                gramming technique for assessing alternate network configurations and
                   costs). All systems are assumed to be installed in the first year of net-              determining optimum network composition. The actual run time for the
                   work operation. Drifting buoys are incorporated into the network at the                numerical model was on the order of one to two days, including prepara-
                   lowest levels of network initial cost constraint. In effect, they have the             tion of all input data. The complexity of the problem, even with only
                   highest ratio of utility to initial cost, and the numerical model selects their        four system types and several constraints, is such that solution without
                   implementation where network initial costs are severely constrained.                   a numerical model would be very inefficient.
                   Moored buoys are installed next as the network initial cost constraint is
                   raised, followed by C-MAN stations and SEAS. (Note that at an initial                  The use of a numerical model such as OPTNETI cannot take the place
                   cost = $1,000,000, the network initial and recurring costs are equal; it               of thorough planning and negotiation of requirements. Nevertheless, the
                   is unlikely that a network would be implemented at an initial cost level               value of this technique, if appropriately and judiciously employed, can
                   less than this value.) Below an initial cost constraint level of just over             -be of significant benefit. While requiring care in the formulation of the
                   $1,300,000, the total expenditure constraint of $5,000,000 (first year plus            problem and judgment in the interpretation of results, the linear program-
                   four recurring years), is not reached. Between an initial cost of $1,300,000           ming numerical model approach enables a network planner to quickly
                   and $1,626,000, both the inital cost and total expenditure constraints are             and efficiently investigate a broad spectrum of network possibilities and
                   binding. SEAS units, with their low recurring costs, are introduced at                 to quantify their relative merits.
                   the expense of drifting buoys for this range of initial cost constraint. The
                   network overall utility, having reached a maximum at an initial cost con-
                   straint of $1,300,000, remains constant as the initial cost constraint is                                         5.REFERENCES
                   raised. Above a network initial cost constraint of $1,626,000, all quan-
                   tities of systems are frozen, since the network total expenditure constraint           I ."Evaluation and Upgrading Strategies for the Marine Monitoring
                   has been reached, but all the initial budget cannot be spent.                             System," Ocean Data Systems, Inc./Global Weather Dynamics, Inc.,
                                                                                                             January 1986.
                   As a last item of note, the optimum of optimum network configurations,
                   given that all the budget can be spent, occurs at an initial cost constraint           2. deNeufville, Richard and Joseph H. Stafford, Systems Analysis for
                   equal to or greater than slightly above $1,300,000. This point is where                   Engineers and Managers, McGraw-Hill Book Company, New York,
                   the maximum network overall utility,is first obtained.                                    1971.

                                                                                 DRIFTING BUOYS
                                         40--                                                                                                                       4.0

                                         30--                                                                                                                    --3.0

                   QUANTITY                                                                                                                                                   SLACK ON
                   OF SYSTEMS                                                                                                                                                     BUDGET
                                                                                                                                                                          CONSTRAINTS,
                                                                                                                                                                                      $M
                                         20                                                                                                                      --2.0

                   NETWORK
                   UTILITY x 10-2

                                         10-
                                                                                                                                                                    1.0

                                                                                                                              C-MAN

                                                                              W,                                                              \\N\
                                                                                                                                           r"i
                                          0                                                                                                                         0
                                              0                    0.5                     1.0                    1.5                    2.0

                                                                                  NETWORK INITIAL COST CONSTRAINT, $M
                   Figure 2. Optimum Marine Observing Networks for 5- Year Life and Total Expense                      $5M

                                                                                                   631

                                            AN USER-FRIENDLY MULTI-FUNCTIONAL CTD SOFTWARE PACKAGE

                                                              Woody C. Sutherland

                                                       Duke/UNC Oceanographic Consortium
                                                           Duke University Marine Lab
                                                            Beaufort, NC 28516-9721

                                      ABSTRACT                                   The SMART CTD has been upgraded by Neil Brown
                                                                            Instrument Systems to allow interfacing of
                      An in-house software package was developed on         additional sensors.   A Sea Tech fluorometer and a
                 a Hewlett Packard 9816 microcomputer for CTD               Sea Tech transmissometer are currently used in CTD
                 operations aboard the R/V CAPE HATTERAS.           The     operations aboard the R/V CAPE HATTERAS.           The
                 package includes routines for data collection,             analog signals from these instruments are
                 data storage, and tabular and graphical display.           digitized inside the SMART and the data
                 Pre-cast setup of the software permits the                 multiplexed with the conductivity, temperature and
                 scientist to select from a number of parameters to         pressure values.    The data string transmitted up
                 customize the operation to meet his/her individual         the sea cable then contains five measurements.
                 requirements. Post-cast routines read stored data
                 from discs, perform tabular print-outs and hard                 The Hewlett Packard 9816 is based on a 8 MHz
                 copy graphical display, and transfer of data to            Motorola MC 68000 16-bit microprocessor with 32-
                 IBM-compatible mass storage media.                         bit internal architecture.     The system on which
                                                                            the CTD software was developed and runs has a 400
                      Presently used with a Neil Brown SMART CTD            x 300 resolution monochrome monitor, 3/4 megabyte
                 having a sampling rate of approximately 4 Hz, the          RAM, a 15 megabyte hard disk which is used for
                 software/computer combination is able to collect           permanent storage of the CTD software and
                 all available data.   Use of faster sampling CTD's,        temporary storage of CTD data, and a 720 K byte 3
                 e.g. NBIS Mark III and SeaBird, would probably             1/2" double sided floppy disk for the final
                 require a subsampling of available data.       Written     storage  of CTD data.     Output devices are an HP
                 in Hewlett Packard Pascal and utilizing a modular          ThinkJet printer and an HP 7475A six-pen graphics
                 design, the software can be easily ported to               plotter.
                 other, possibly faster, computers. This will soon
                 be done for the IBM AT class of microcomputers.                 The software was written in HP Pascal version
                                                                            3.0, a superset of American National Standards
                                                                            Institute (ANSI) Pascal.     Due to the structured
                                                                            nature of the Pascal programming language and
                                    INTRODUCTION                            extensive use of procedures, functions and modules
                                                                            (HP terminology) the CTD software package can be
                      An integrated software package was developed          ported easily to other computer systems having a
                 on a Hewlett Packard 9816 microcomputer to                 Pascal compiler.    This is being done for the IBM
                 collect, display and store oceanographic data from         AT class of microcomputers at the request of a
                 a Neil Brown Instrument Systems SMART CTD.         The     number of regular ship users.
                 SMART CTD, operating in raw data continuous mode,
                 outputs conductivity, temperature and pressure                               INITIALIZATION
                 measurements at a rate of approximately 4 samples
                 per second.   This data string is transmitted via               Upon running the main program the user is
                 frequency shift keying (FSK) communications                greeted with a CRT screen listing the version of
                 through a two-conductor sea cable to a shipboard           the software, presently 3.0, and requesting a
                 mod ul ator/demodulator unit.       The modulator/         choice of CTD instruments.     Duke / University of
                 demodulator unit translates the FSK      signal to a       North Carolina Oceanographic Consortium (DUNCOC),
                 RS-232 signal which is input into the                      which operates the Research Vessel CAPE HATTERAS,
                 microcomputer.    Data communications   are at 1200        owns two Neil Brown Instrument Systems SMART
                 baud.   The raw data signal from the FSK unit is           CTD's, designated "A" and "B".     The SMART CTD is
                 recorded on audio cassette as a backup in the              designed to have the calibration coefficients for
                 event of microcomputer failure.                            the conductivity, temperature and pressure
                                                                            channels stored on EPROM inside the instrument.

                                                      CH2585-8188/0000- 632 $1 @1988 IEEE

               As DUNCOC performs its own calibrations it is more           most frequently used.     The data are averaged over
               convenient to have the coefficients stored in a              one-half meter depth intervals and are catalogued
               disk file to be read by the main program.          Thus,     as the deeper depth. Thus, data collected between
               when the user selects one of the CTD's, a                    1.01 m and 1.50 m depth are averaged and stored on
               specified file on the hard disk is opened and the            disk as 1.5 m depth data.
               following variables are read into the main
               program:                                                           The next screen prompts for station
                     a) Letter designation of CTD                           statistics.      These are: a) Cruise number, b)
                     b) Serial Number of CTD                                Station name, c) Position, i.e. latitude,
                     c) Last date of calibration                            longitude, and time differences if Loran C used as
                     d) Quadratic calibration coefficients for              positioning device, d) Log of cassette tape, i.e.
                         conductivity, temperature and pressure             Tape number and side, and Meter wheel reading for
                     e) Calibration coefficients for                        beginning of data recording.          Values from the
                         fluorescence and light transmission                previous station are listed and only those
                     f) Disk volume where to temporarily                    different need be changed.             The position
                         store CTD data                                     statistics can be entered via the keyboard or an
                     g) Disk volume where to     permanently                interface with the SAIL (Serial ASCII
                         store CTD data                                     Instrumentation Loop) can supply the digital data
               The user is then presented with              a screen        directly from the ship's Loran or Global
               displaying this information so that he/she can               Positioning System unit. The user is prompted to
               Verify the selection of the correct CTD in use and           verify the correctness of the entries before being
               examine the date of last calibration.                        allowed to continue.

                     The next screen prompts for verification of                  The file name for the CTD data is constructed
               use of additional sensors on the CTD underwater              from  the station name and cruise number.       Cruises
               package. The SMART is mounted on a frame, usually            on board the R/V CAPE HATTERAS are numbered from
               with a General Oceanics rosette assembly for water           the beginning of the calender year.       For example,
               bottles.   Frequently a pinger is also attached to           CH0588 signifies the fifth cruise of 1988, the
               accurately measure altitude above the sea floor.             beginning two letters standing for the name of the
               When desired, the Sea Tech fluorometer and                   ship.   The file name is the station name followed
               transmissometer are mounted to the underwater                by an underline, the last digit of the year and
               package.   The use of these two additional sensors           the two digits of the number of cruise for that
               is queried because it affects the length of the              year.   Thus, CTD data for a station named "PRIMO"
               data string and the need for calibration of their            on cruise number "CH0288" would be stored in a
               measurements.      Also, the fluorometer has an              file named "PRIMO   802". When the user answers YES
               internal switch which changes the range of its               to the correctness of the station statistics, the
               readings, and thus the calibration coefficients.             disk volume where the final copy of the CTD data
               The setting of this switch must be entered into              will be stored is checked to see that there is not
               the CTD software so that the proper coefficients             an existing file with the same name.         If one is
               are used.                                                    present then the station statistics screen is
                                                                            again displayed with a message that a file with
                     Seven columns of data can be displayed on the          that name already exists. The user is prompted to
               CRT during the lowering of the CTD.          The first       enter a different station name and then must again
               column is reserved for depth in meters.       The user       verify  the values.    This loop continues until an
               selects the next five column designations from               unique file name is formed.           This precaution
               conductivity, temperature, salinity, sigma-t,                guards  against the  overwriting of a file and loss
               fluorescence and light transmission.        The values       of CTD  data.
               for salinity and sigma-t are calculated from
               conductivity,       temperature and pressure                       A sea-surface   measurement is taken to zero
               measurements according to Fofonoff and Miller                the   CTD pressure   data, thereby eliminating the
               (1983).   Either time of day (hour: minute: second)          need to physically zero the pressure transducer
               or lowering rate of the underwater package                   which can be affected by fluctuations in
               (meters/minute) is displayed in the final column,            atmospheric pressure.     This value is entered into
               by selection of the user.                                    the CTD software as a pressure offset and is
                                                                            subsequently subtracted from all further pressure
                     A real-time graphical display of the data can          readings for the lowering to yield a more accurate
               be performed in addition to the tabular Output.              depth calculation.    This offset can be entered by
               If the graphical display is selected, the user               the user via keyboard or directly from the CTD.
               must choose a property to display, e.g. salinity,            The preferred method is to lower the CTD over the
               temperature, etc., and enter parameters with which           side of the ship and hang it at the water's
               to scale the graph, i.e. maximum depth of CTD                surface.     Pressure readings from the CTD are
               lowering and minimum and maximum expected values             displayed on the computer terminal.          The user
               of the property.                                             presses a key to accept a value for the offset.
                                                                            Hanging the dTD underwater package at the surface
                     All of the  valid data can be stored on disk           is not practical in rough seas as it may be
               (raw mode) or     the user can select to store               damaged by striking the ship.      Thus the option of
               averaged data.    Since raw data are available from          entering a pressure offset via the keyboard is
               the cassette recording and disk storage space                given.
               usually needs to be conserved, the average mode is

                                                                        633

                                    CTD LOWERING                            data was selected then values for these properties
                                                                            which passed the three levels of filtering are
                      With input of the pressure offset the CTD             written to the disk      file.    In average mode,
                 underwater package is ready for lowering. A brief          filtered values for these six properties are
                 reminder to start the cassette for recording of            averaged over one-half meter depth intervals and
                 the raw data signal is flashed on the screen, a            the mean values written to disk.
                 number of program variables are initialized, files
                 are opened on the appropriate disk volumes,                     The collection, calibration, filtering,
                 routines are called to prepare the real-time               display and storage of CTD data continues until a
                 graphical display and the bottom line of the CRT           designated key is struck by the user.        At that
                 is labeled with the names of the properties                time the data file is closed and saved, the
                 selected to be displayed.     The winch operator is        graphic routines are terminated and a reminder to
                 requested to begin lowering the CTD.                       stop the cassette recorder is flashed on the
                                                                            screen.   A menu is displayed giving the user the
                      Each string of multiplexed data sent to the           option to: 1) begin raising the CTD package, 2)
                 HP 9816 from the modulator/demodulator'utiit passes        plot CTD data on the CRT, 3) plot CTD data on the
                 through three levels of filtering routines before          HP pen plotter, 4) print CTD data, 5) transfer
                 being accepted as valid data.     First, the string        data to disk volume for permanent storage or 6)
                 is checked for the proper number of characters and         terminate the program.
                 the proper sequence of numeric characters and                   Output of data to devices other than the CRT
                 commas.    Values for the individual properties            are time consuming and these options are given
                 conductivity, temperature, 'pressure, and if               again once the CTD is back aboard ship.           Thus
                 appropriate fluorescence and transmission, are             their operations will be discussed later.         They
                 extracted from the string.         These values are        are practical only if a hard copy of the data is
                 entered into their respective calibration                  needed before raising the CTD or if the CTD needs
                 equations. The pressure offset is subtracted from          to hang at depth, e.g. to allow reversing
                 the calibrated pressure value.     The second level        thermometers to come to equilibrium.      Graphs can
                 of filtering checks these calibrated values                be quickly repeated on the CRT, although with only
                 against the published minimum and maximum for each         one property at a time, to aid the user in making
                 instrument.     Each property is finally compared          decisions on where to trip water bottles on the
                 with its last valid value to confirm that                  return to the surface. The first graph on the CRT
                 empirically predetermined differences are not              for each property selected extends from the
                 exceeded.                                                  surface to the maximum depth and is scaled from
                                                                            the minimum to the maximum value collected.
                      Derived properties, e.g. depth, salinity,             Following this first graph the user is queried if
                 sigma-t, are calculated from the accepted values           he/she desires to change the depth limits in order
                 of conductivity, temperature and pressure.                 to zoom in on a portion of the graph.     If the user
                 Minimum and maximum values for each property,              so chooses, he/she is prompted to enter the
                 which are used in post-lowering routines to scale          minimum and maximum depths for the new graph. The
                 graphical presentations, are updated with the              graph is redrawn with the new depth scale and a
                 current values.      Values of depth and the six           new property scale with the minimum and maximum
                 selected properties are formatted and displayed on         values collected within this depth interval.
                 the CRT.    The lowering rate is calculated every
                 five seconds ; it was discovered that ship motion               Striking the key to begin raising of the CTD
                 from surface sea state had too much effect on the          brings up the tabular display screen.      The bottom
                 calculated    lowering rate using shorter time             line is labeled with the names of the selected
                 intervals.                                                 properties and input from the CTD is accepted.
                                                                            Data collected during the raising of the CTD is
                      If the   real-time graph was chosen then the          not stored; values displayed pass through only the
                 CRT screen can be switched from tabular to                 first filtering process.     A key is activated so
                 graphical    display by striking a key.            The     that when pressed a routine for closing a water
                 corresponding depth of the selected property must          bottle is begun.
                 be greater than that of the previous value before
                 it is graphed, thus yielding a smoother curve.                  The CTD is raised through the water column
                 Graphing of multiple properties was attempted in           until a depth where the user wishes to collect
                 previous versions of the software, but the only            water is reached.       CTD ascent is halted, the
                 method of distinguishing between properties was by         designated key is pressed on the computer
                 different line types and this proved visually              keyboard, and a button is pressed on the General
                 confusing on the HP 9816 monochrome monitor.        if     Oceanics rosette shipboard unit.              Program
                 the depth of the CTD exceeds that originally               execution is halted while the rosette unit
                 entered then an additional 100 m is added and the          provides a high voltage signal to the underwater
                 graph rescaled, thereby facilitating a search for          unit activating the closure of one of the water
                 an interface which may be deeper than expected.            bottles.    The delay in the program is preset to
                 The addition of 100 m increments will continue as          match the time necessary to trigger the rosette
                 needed until stopped by the user.                          underwater unit. Following the delay the computer
                                                                            inputs CTD data for one minute, averages this
                      Data is stored in a disk file as a series of          data, displays this information on the CRT
                 real numbers: depth, conductivity, temperature,            indicating that a water bottle has been closed,
                 pressure, fluorescence and transmission.       If raw      and writes the data to a file which will include

                                                                         634

                data on all bottles closed during the raising.              fluorescence, and light transmission may be
                The program continues to collect CTD data and               selected for vertical profiles on each graph.
                display it on the CRT until the water bottle key            Temperature vs salinity graphs are also an option.
                is struck again or a key assigned to the end of             Graphs are labeled with the cruise number and
                the raising is pressed.                                     station name, and scaled with the minimum and
                                                                            maximum collected for each property.
                     When the CTD reaches the sea surface, or the
                user is no longer interested in watching the data                The user is returned to the final menu
                collected, a key is pressed to terminate the                following the completion of each output.
                raising CTD routines.       The file containing the         Therefore, he/she can produce as many print-outs
                water bottle data is closed and saved, and a copy           or graphs as desired, in any order, and then
                is sent to the printer.       The user is given the         choose to begin another station with the same
                opportunity to enter a comment for the station and          parameters.
                is prompted to enter the cassette meter wheel
                reading for the end of the raw data recording.                         SOFTWARE FOR STORED CTD DATA
                The file for permanent storage of the CTD data is
                opened as an ASCII text file.            The station             An independent portion of the CTD software
                information, i.e. cruise number, station name,              package is designed to operate on the permanently
                date and time, position, cassette log and comment,          stored files.    A separate HP 9816 microcomputer
                is written to the file.          CTD data from the          system is available on the R/V CAPE HATTERAS to
                lowering are translated into strings of depth,              permit scientists to reexamine data from previous
                conductivity, temperature, pressure, fluorescence           CTD 'stations, or the primary system can be used
                and light transmission and written to the storage           while not actively collecting data.      The opening
                file.   The permanent disk volume is most often a           menu gives options for: 1) tabular or graphical
                floppy disk.    Should the disk fill up during the          output from    single -CTD stations,    2) graphical
                writing of the data the file is closed and the              output of one property from multiple     stations, 3)
                user is prompted to insert another formatted disk           assimilation of statistics from         a number of
                to continue.   A file is opened on the new floppy,          stations, and  4) output ASCII data file via RS-232
                the station information is written to the                   interface.
                beginning of the file, and transfer of the CTD
                data begins from where it was discontinued in the                Selection of the first option prompts for
                previous file.      Data for the water bottles is           keyboard input  of a CTD data file name.     The data
                written to a . permanent file on the same disk              file is opened, the station statistics read and
                volume following transfer of the CTD lowering               displayed on the CRT. The user confirms that this
                data.                                                       is the desired station by virtue of the display
                                                                            and, if so, the remainder of the data file is read
                     The final screen gives the options of                  into memory.    Choices of printed tabular output
                graphical display on the CRT or pen plotter,                and graphical output to CRT or pen plotter are
                printed tabular output, initiation of another CTD           presented.   These routines perform as discussed
                station with the same parameters, or termination            previously.    Following each output the user may
                of the   program.    If the user chooses to begin           choose to return to the main menu.
                another station, the program loops back to the
                station statistics screen, continues to the                      The second option first asks for the number
                pressure  offset, and is ready for lowering of the          of stations.   Physical size of the   graph paper and
                CTD package.      Values for the real-time graph,           number of pens, i.e. colors, limits this number to
                selection of properties for display and the mode            five.    The sequence of prompting for file name,
                of data storage remain as for the previous                  displaying station statistics         and requiring
                station.   Termination of the program returns the           verification is executed for each of the stations.
                computer to the HP Pascal operating system.                 The user must then choose one of the seven
                                                                            properties to plot ( conductivity, temperature,
                     Printing of the CTD data requires the user to          salinity, sigma-t, sound velocity, fluorescence,
                choose an interval over which to average the                light transmission ), the size of paper to use,
                output. The data may be printed as stored, either           and the scaling parameters for the graph ( maximum
                raw or averaged over 0.5 m, or averaged over a              depth, minimum and maximum property values ). The
                larger interval as is frequently done for deeper            graph is drawn on the plotter using a different
                lowerings.   Station statistics are printed at the          pen for each station.
                top of odd numbered pages.       Columns are labeled
                from left to right as depth, conductivity,                       A summary file composed of the station
                temperature, salinity, sigma-t, sound velocity,             statistics for all CTD stations is made following
                light transmission, and fluorescence.         Data is       each cruise.      These are the files that are
                averaged as necessary, the        derived properties        searched when a scientist requests CTD data from a
                calculated, and printed in the respective columns.          specific location or time.         The third option
                Multiple copies are possible in case more than one          permits the     user to make such a file for
                scientist requires the data.                                him/herself as a summary for CTD data collected
                                                                            during a day,   week, entire cruise, etc.       He/she
                     Graphs of the data can    be produced on 8 1/2"        can choose to   send the output of this summary to
                X 11" or 11" X 14" paper.         A maximum of four         the CRT, where only a screen-full at a time is
                properties from the list of conductivity,                   displayed, to the printer or to a text file on
                temperature, salinity, sigma-t, sound velocity,             disk.

                                                                         635

                     More ship users have access to IBM-compatible
                than to Hewlett Packard microcomputers.    The last
                option provides CTD data on IBM compatible mass
                storage media.    A complementary program must be
                executed on one  of the IBM compatibles on board
                ship.   Data is transmitted from the HP 9816
                through the serial port to the IBM microcomputer.
                The user can select to send the data file by file
                or an entire disk of files at a time.       Transfer
                occurs at 9600 baud using an Xmodem checksum
                protocol.

                                   CONCLUSIONS

                     As an extension of the concept of the R/V
                CAPE HATTERAS being an user-friendly ship, CTD
                software was developed to permit the scientist to
                fashion CTD operations to meet his/her
                specifications.     It has proven invaluable to
                scientists as an aid in determining sample schemes
                while at sea.     This is an ongoing process and
                updates to the CTD software package will continue
                to be made as use and need dictate.

                                 ACKNOWLEDGEMENTS

                     Support for development of the CTD software
                was provided by the National Science Foundation
                Shipboard Technicians Program, grant number
                OCE8615924.    Thanks are given to the electronics
                technician, Tim Boynton, the head of the DUNCOC
                CTD committee, Dr. John Morrison, and the many
                ship users over the past three years for their
                constructive criticism and helpful suggestions
                concerning the CTD operations.

                                    REFERENCES

                Fo f ono f f , N. P. and R. C. Millard Jr. (1983)
                     Algorithms for computation of fundamental
                     properties of seawater.      Unesco technical
                     papers in marine science No. 44.

                                                                     636

                                                                                                       ONLINE ACCESS TO NODC INFORMATION SERVICES

                                                                                                                        Douglas Hamilton and Janet Ward

                                                                                                                   National Oceanographic Data Center
                                                                     National Environmental Satellite, Data, and Information Service
                                                                                              National Oceanic and Atmospheric Administration
                                                                                                                                     Washington, D. C. 20235

                                                                                ABSTRACT                                                                                        minimize the time and personnel needed to handle
                                                                                                                                                                                WOCE data and to maintain up-to-date knowledge
                             Oceanographic data holdings of the National                                                                                                        of the status of WOCE data.,,5 In view of those
                             Oceanographic Data Center (NODC) are large and                                                                                                     needs, NODC developed a prototype on-line
                             varied. A goal at NODC is to provide timely                                                                                                        information system called NOSIE - the NODC Ocean
                             information about those data to users via online                                                                                                   Science Information Exchange.
                             caqmter aooess. Recently, NODC has developed a
                             prototype system, called NOSIE (NODC Ocean
                             Science Information Ewliange), that includes                                                                                                                                                    THERMAL DATA
                             descriptions of NODC data files, helps for
                             sending or ordering data, interactive inventory                                                                                                                                          GLOBAL DISTRIBUTION
                             sLmmaries, and bulletin boards. NOSIE is a
                             mem-driven, modular system to which information                                                                                                                               120
                             resources of various types can easily be added.                                                                                                                                                                                                                     N@
                             It was designed using system software for screen                                                                                                                              100 ----- ------  ------------------------  ----- - -------- ---------------
                             management to provide a consistent look-and-feel                                                                                                                                                                                                                      WT
                             during each session.                                       Future plans am to expand                                                                                          BD ---------------*---------------                     ----- I----------           &19=
                             inventory smnaries, add detailed inventories,                                                                                                                                 60 -------- ----------------                                 ... .........              XBT
                             and make subsets of ocean files or special data                                                                                                                                                                                                                       STD
                             sets directly accessible online.                                                                                                                                              40 --------       --------
                                                                                                                                                                                                                                                                                                   SBT
                                                                                                                                                                                                           20 --------------

                                                                        1. INTMDUCTION                                                                                                                     0
                                                                                                                                                                                                           194)                          1%0                            1W
                                                                                                                                                                                                                             19T                        1970
                             Oceanographic data on water column properties,                                                                                                                                                            COLIEC110N YEAR
                             chenistry, biology, surface waves, and other
                             parameters are available frarithe National                                                                                                           Figure 1. Time distribution of thermal data
                             Oceanographic Data Center (NODC). Data held by                                                                                                                                    collected by various instnments
                             NODC span the globe and cover the time period
                             from 1900 to the present, although most data
                             were obtained after 1940. For exanple, Figure I                                                                                                      Table 1. Major NODC data holdings, January 1988
                             shows the volume of one type of NODC data -
                             terperature observations - as a function of
                             time, collected with various instruments aver                                                                                                                        DISCIPLINE                                                                   VOUME
                                                                                                                                                                                                                                                                               (GBytes)
                             the years since 1940. A summary of the types                                                                                                                                                                                                               -
                             and volumes of data available from NODC is shown                                                                                                                     Physical
                                                                                                                                                                                                           Buoy (Wind/wave)                   . . . . . . ...                     3.95
                             in Table 1. The person who wants to order data                                                                                                                                Current           . . . . . . . . . . . .                              2.45
                             from NODC needs to know if the type of data                                                                                                                                   Ocean Station                 . . . . . . . . .                        1.25
                             wanted are available in the region and time                                                                                                                                   subsurface Temperature                           . . . . .             0.67
                                                                                                                                                                                                           salinity/Temperature/Depth                                   . . .     0.83
                             period of interest. Therefore, data requestors                                                                                                                                Other . . . .                                                          0-06
                             need access to inventories and information about                                                                                                                     Biological                           T@TiL'Pff*YS*IC*AL'                        9.20
                             NODC data holdings.                                                                                                                                                           Fish/Shellfish                ... . . . . . . .                        0.12
                                                                                                                                                                                                           Benthic/Intertidal Organisms.                                       .  0.09
                             One of NODC's principal goals is to improve ease                                                                                                                              ma ine Birds                . . . . . . . . . .                        0.05
                                                                                                                                                                                                           Plankt n          . . . . . . . . . . . .                              0.03
                             of access to data and to data inventories.                                                                                                                                    other 0                                . . . . . . .                   0.03
                             Those who plan ocean research projects such as                                                                                                                                                            T;T@L BIOLOGICAL                           0.32
                             the World ocean Circulation Experiment (WOM) 2                                                                                                                       Chemical
                                                                                                                                                                                                           Marine chemistry.                                                      0.07
                             and the Global Ocean Flux Study (GOFS)l have                                                                                                                                  P.llutants/Toxic substances                                            0.02
                                                                                                                                                                                                                                       TOTAL CHEKICAL                             0.09
                             stated the need for timely access to ocean data.
                             "Maxiimm use of online summaries, electronic                                                                                                                                         TOTAL DATA BASE                      . . . . . .                9.61
                             queries, and electronic data transfer will

                                                                                                                                                                     637

                   It became technically possible to develop NOSIE                         NOSli Menu Structure
                   in mid-1987, when NODC became a node on the                                  (Top three /a vels)
                   Space Physics Analysis Network (SPAN), managed
                   by the National Aeronautics and Space
                   Aftinistxaticn (VASA). Major oceanographic                                   V@TOSIE
                   centers connected to SPAN (Figure 2) ommmicate
                   messages, data, and information about data                                       MENU
                   directly Unvugh the network. Although NOSIE
                   resides on an NODC caqmter, anyone with access
                   to SPAN can tap into the NOSIE information                                 Data       Catalogs/      U or
                   resource.  In addition, those with no SPAN                   General     SubmIssion   Inventories    SeZes,
                   connection can dial directly into the system.
                   It is considered by NODC to be the "electronic"
                   window to information about our ocearKx1raphic
                   data holdings.

                                                                                                           d- les
                                 SPAN Ocean Nodes
                                                                                  Buletin
                                                                                  boards

                     AOSU
                                                                  Hot                                                  Or&* user
                                                                                                            and          request
                                                                                                          publkations    B--V*

                                                              UD"-r.
                                  ANSI
                                                          ODC
                      JCSB

                     JP
                        SI
                                                                                                                 yet aveftable; module
                                      UT-i ATAM N       FSU                                                   under development.
                                                                             Figure 3. Menu structure of the NODC Science
                                                                                         Infonration Rwhange Syst@

                                                                             oceans and seas over a time period of several
                                                                             decades. Inventory summary searches provide the
                                                                             number of stations available for geographic and
                   Figure 2. Ocean centers on the Space Physics              tire criteria set by the user. The resolution
                              Analysis Network                               for searches is month for time, and one-degree
                                                                             square for geographic area.

                                                                             b. File Descriptions
                           2. NOSIE STRUCnM AND OONTMS
                                                                             For those who need an introduction to the types
                   NOSIE consists of a series of menus which lead            of data stored at NODC, brief text descriptions
                   to: other merms, to text information, to                  of NODC oceanographic data files are available
                   bulletin boards, or to interactive inventory              from the Catalogs/Inventories menu. As shown in
                   summaries. By navigating among appropriate menu           Figure 4, users may find the time period and
                   choices, users can quickly obtain the                     geographic area coverage of data in a file. The
                   information desired. The first three menu                 file size, file structure, and principal
                   levels are shown in Figure 3.                                      paranve-ters available are also presented
                                                                             in these file descriptions.
                   a. Online Inventories
                                                                             c. Assistance in ordering Data
                   Someone who wants to order data fran a
                   particular region of the world, and perhaps from          After reading a file description, and checking
                   a specific time period, will want to know how             the inventory summary for amounts of data
                   many data are available. Because NODC data                available, a user may decide to ask for more
                   holdings are so large and varied, it was not              information or order data. nie User Services
                   practical to provide complete, detailed                   menu leads to text screens which give ordering
                   inventories with this prototype. However,                 procedures. In that section, guidelines for
                   inventory smmaries are provided for four major            ordering data from NODC are presented, and a
                   data files - CID/STD (conductivity/salinity               contact person and phone number are shown.
                   tenverature depth) data, oceanographic station            other segments give information on user charges
                   data, and expendable and mechanical                       and how payments can be made. If more
                   bathythermograph data. Data in each of these              information is wanted, a single key-stroke adds
                   files are available from roost of the earth's             the name of the file being reviewed to a

                                                                      638

                       Fite: Expendable Bathythermograph (XBT) Data                                                                    FILE                      NO. OF       NO. OF    NO. OF
                                                                                                                    DATA TYPE          ALIAS      SOURCE         STATIONS     RECORDS TAPES
                       Geographic Coverage: Worldwide Oceans                                                        Ocean Stations     CIOO       MIAS UK;             549      8,321        -
                       Time Period: 1966 to Present                                                                                               NOAA AOML;
                                                                                                                                                   NMFS woods
                       Fite Organization: cruise and Geographic Order                                                                             Hole;
                                                                                                                                                  Lamont (1)
                       Fite Size- 718,181 stations; 220 megabytes (July 1, 1988)                                    Analog XBTs        C116       usGs woods           84             84
                                            Cruise file - 3      magnetic tapes (6250 bpi)                                                        Hole (2);
                                            Geofile       - 5    magnetic tapes (6250 bpi)                                                        US Navy
                       Description:                                                                                 Digital XBTs       C116       NOS Seattle;       1,497      1,497        1
                                                                                                                                                  NMFS@
                       This file contains temperature-depth profile data obtained using                                                           Narragansett
                       the expendable bathythermograph (XRT) instrument. Standard XSTs                                                            (3); PRC (4);
                       can obtain profiles to depths of either 450 or 760 meters,                                                                 UK Navy
                       depending on the model. With special instruments, measurements                               C/STD              F022       NOAA PMEL (4); 2,052          76,696
                       can be obtained to 1830 meters. Cruise information, position,                                                              OR State Univ.
                       date, and time are reported for each observation. The data record                                                          (8); Lamont
                       comprises pairs of temperature-depth values. Unlike the MST data                                                           (1);  NMFS Woods
                       file, in which temperature values are recorded at uniform 5 meter                                                          Hole; Univ. AK;
                       intervals, the XBT Data FiLe contains temperature values at non-                                                           NMFS  La Jolts
                       uniform depths. These depths are at a minimum number of points                                                             (9)
                       ("inflection points") required to record the temperature curve to                            Wind/Wave          F191       NOAA  NDBC           87     449,786
                       an acceptable degree of accuracy. On output, however, the user              may                 Spectra
                       request temperature values either at inflection points or                                    [GOSS STD          Lev.  A    NOAA  OPC               -           -
                       interpolated to uniform depth increments.                                                    Sea Level          Lev.  A    Univ. Hi    (5)      24       3,043
                                                                                                                    Chemistry/         Lev.  A    WHOI                 311      7,153
                                                                                                                      Plankton
                       Note: Although new XBT instruments can provide digital output on                             GEOSAT             Lev.  A    US Navy             1.7M        1.7M
                       magnetic tape, NODC stilt receives paper strip charts with analog                               (Wind/Wave)
                       traces that must be digitized. only part of the XBT data that it
                       archives are digitized by NODC itself. A substantiaL amount of
                       data are digitized by the U.S. Navy Fleet Numerical Oceanography                             PROJECTS:    (1)   Marathon - 7
                       Center (FNOC), Monterey, Calif.; some data are also digitized by                                          (2)   MMS - New England Shetf/Slope
                       commerical contractors.                                                                                   (3)   SOOP
                                                                                                                                 (4)   US-PRC Cooperative Study
                       Fite Structure:                                                                                           (5)   Tropical Ocean Global Atmosphere (TOGA)
                                                                                                                                 (6)   STACS and Antilles Current
                       One variabte-tength record (maximum 2,540 characters).                                                    (7)   EPOCS and Puget Sound LREP
                                                                                                                                 (8)   Peru Currents Project
                       Note: Although they are maintained in separate files,            mechanfcaL                               (9)   CaICOFI
                       bathythermograph (MST) data and expendable bathythermograph (XBT)
                       data are stored in a common format.                                                        Figure 5. Sample 'Taomt Data Acquisition" list

                                                 PRINCIPAL PARAMETERS
                               Depth                                                                                                        3. ACCESS TO NOSIE
                               Temperature
                       Figure 4. Sairple file description from NOSIE                                                NOSIE is available in two ways. For those with
                                                                                                                    access to SPAN, sinply type "SET HOST NODC!", and
                                                                                                                    type "INFO" at the prompt. For those who have a
                       "shopping list". At the end of a session, the                                                modem but cannot CoiMeCt to SPAN, dial (202)
                       shopping list can be reviewed and changed. At                                                673-5657 (300 baud), or (202) 673-5665 (1200
                       NODC an information specialist reviews the                                                   baud). When the modem is connected, type a
                       shopping list arid sends the information                                                     carriage return. When                                     11 appears,
                       requested.                                                                                   type 11C NODC", then "INFO". The opening NOSIE
                                                                                                                    screen provides instructions for the session.
                       d. Assistance in Sending Data
                                                                                                                                      4. SYSTEM DESIGN FEATURES
                       Helps for sending data to NODC are available
                       from the Data Submission menu. Text screens                                                  NOSIE was designed and developed to operate on a
                       provide guidelines on the types of data to send,                                             Digital Equipment Corporation (DEC) VAX VNS
                       computer media and suggested data formats, and                                               capiter. In order to meet both present arid
                       type of documentation to send with the data. A                                               future needs, NODC developed NOSIE based on two
                       contact arid Phone number for more direct                                                    primary design considerations.
                       assistance are also provided.                                                                First, the system would be required to allow the
                       e. Bulletin Boards                                                                           addition of new information and interfaces to
                                                                                                                    other systems without major modifications to the
                       Bulletin boards of up-to-data information are                                                source code. In order to accoanplish this, a
                       accessible through the General menu. Lists of                                                modular design featuring a main FoRrRAN program
                       data sets recently acqaired are updated weekly                                               and subroutines was adopted. As new
                       (Figure 5)_ Also, special NODC data products,                                                requirerents warrant, subroutine modules can be
                       such as data sets from the SEQUAT4/FOCAL Project,                                            added, modified, or deleted from NOSIE without a
                       are advertised in the Recent Data Products                                                   significant in-pact on the system's overall
                       bulletin board.                                                                              operation.

                                                                                                         639

                  Second, NOSIE was designed to be easy to operate           Of oceanographIc data by coordinating with other
                  (user-friendly) and easy to maintain. To meet              on-line systems. For example, standards in
                  these requirements, NOSIE employs the DEC's                session presentation and control could reduce
                  Terminal Data Management System (TEM) and the              confusion to users of several systems. At the
                  Ommun Data Dictionary (CDD).                               very least, NOSIE will include pointers to other
                  The TEM package is used in two ways: (1) to                ocean information systems.
                  display the special interactive menu screens               NOSIE is a prototype. It is an experiment by
                  during a NOSIE session and automatically check             NODC to learn if having timely access to data
                  user-entered responses, and (2) at the VMS level           and to information about NODC and its archives
                  to create and modify the interactive screens.              is beneficial to users. You are encouraged to
                  The CM package is used to store and manage data            try NOSIE, to tell us what works and what
                  record descriptions.                                       doesn't, and to think about other ocean data
                                                                             services you would like to see available at your
                                   5. FLTILM PIANS                           computer terminal in an online mode.
                  At the end of each NOSIE session, users have the                            6. REFERENCES
                  opportunity to enter comments or questions.
                  Those messages are checked daily at NODC in                1.  Collins, E. and K. Hughes. Report of Global
                  order to respond to requests for data or                       Ocean Flux Study (GOFS) data management
                  information. In addition, comments about the                   meeting, Massachussetts Institute of
                  system are solicited to guide its future                       Technology, February 1987.
                  develcprent. As a result of these comments,
                  NODC is working on expanding and improving NOSIE           2.  Emery, W. Global Circulation Studies: The
                  in several ways.                                               need for data submission and exchange in
                  Inventory summaries of other NODC files are                    wom, Worm NEWSLETTER. 4, WOCE International
                                                                                 PlwudM Office, Godalming, Surrey, UK. May
                  planned. Also, the possibility is being                        1987. p12-13.
                  considered of providing graphic charts to assist
                  users in setting inventory search criteria and             3.  Hewitt, R., S. Jacobson and C. Meyer.
                  to show results of the search.                                 CalCOFI On-line Data System Programmer's
                                                                              I  Manual, Administrative Report IJ-88-03,
                  Some data search questions require more detailed               National Marine Fisheries Service, la Jolla,
                  answers than are given by the inventory                        CA, 1988.
                  sunmaries. Although it is not possible to
                  provide detailed inventories of all NODC data              4.  Soreide, N. and S. P. Hayes. EPIC: An
                  files through NOSIE, such inventories are ,                    Oceanographic Data Archival and Retrieval
                  planned for selected subsets of the archive or                 System, Proceedings of the Fourth Working
                  for data sets of special interest. These will                  Symposium on Oceanographic Data Systems,
                  give users the ability to search, for exwple,                       Computer Society, Washington, D.C.,
                  for specific measured parameter s, for project                 1986.
                  data, for data from specific ships, and other
                  criteria.                                                  5.  U.S. Science Steerirxj Committee for WOM.
                                                                                 U.S. WOCE nVIEWMATION PLAN, First Draft,
                  Within existing computer system limitations, it                U.S. Planning Office for WOCE, Texas A&M
                  is planned to place selected subsets or special                University, College Station, TX, 1988.
                  data sets online for users to peruse or upload
                  to their own caqwter system. As planned                    6.  Withes, W. and D. Hamilton. Opportunities
                  projects such as WOCE, GOFS, and others get                    in Oceanographic Science Offered by New
                  underway, this is expected to be a quick way for               Advances in Data Management, Proceedings of
                  researchers to have access to small data sets of               the Law of the Sea Conference, University of
                  interest. Larger data sets will be distributed                 Rhode Island, June 1988.
                  on conventional magnetic media, and an optical
                  CD-RCM.6 NODC is now preparing its first ocean
                  data CD-RCK product to test the feasibility of
                  distributing very large data.

                  NOSIE is one of several on-line ocean
                  information system. Within NCAA, for example,
                  the Pacific Marine Environmental L-Amratory
                  developed EPIC, which provides inventories of
                  and access to data stored at that facility.4
                  The California Cooperative Fisheries
                  Inventigations project has provided on-lim
                  access to its data for several years.3 More
                  recently, the University of Delaware developed
                  OCEANIC, which is available either via SPAN or
                  OMNET, a commercial network system. We are
                  investigating ways to improve service to users

                                                                      640

                                               ROBUST SEQUENTIAL W-INTERVAL APPROXIMATION
                                                  DETECTORS WITH O-DEPENDENT SAMPLING

                                              Evriclea Voudouri         Ludwik Kurz

                                              Manhattan College         Polytechnic University
                                            Riverdale# N.Y.10471        Brooklyng N.Y.1120

                                   ABSTRACT                             contaminated and varying noise environments. The
                                                                        theory of the MIPA detectors was extended to
             In this paper, the theory of a robust sequential           include sequential operation      for     independent
             detection scheme is extended to include operation          sampling in [5] and for dependent sampling of
             with   Q-dependent     samples    of      unspecified      unspecified bivariate and first order          Markov
             dependence. The detectors are designed to exhibit          dependence in [6]. The above assumptions on the
             a near optimum performance for nominal noise               type of dependence-can be relaxed if a modified
             distributions and maintain high efficiency to              version   of the Woinsky-Kurz scheme, [7], is
             changing noise environments by adapting their              introduced to treat the       problem   of     signal
             optimum    nonlinearity     Using    an    m-interval      detection with dependent samples of unspecified
             polynomial approximation (MIPA)      of    it.    The      Q-dependence, Q>2. In this case, the sampling rate
             performance is evaluated for weak signals in               can increase 'even further, resulting        in    an
             contaminated and/or varying noise         backgrounds      improved    performance     over   detectors     with
             often encountered in underwater acoustics. It is           independent or bivariate dependent samples.
             shown that the MIPA detectors improve           their
             efficiency, in certain cases up to Q times, at the         Woinsky's idea was first to create a sequence of
             expense of a slight increase in their structural           independent vector samples of dimension N, N>Q, by
             complexity to include operation with dependent             properly grouping the dependent samples. !ffis is
             sampling. Moreover, the sequential MIPA detectors          accomplished by placing N consecutive samples in a
             are asymptotically optimum and increase their              vector, form an intermediate statistic and then
             transmission rate up to four times as compared to          skipping Q-1 samples to ensure that the next
             their fixed sample size counterparts.                      vector of N components is independent of the
                                                                        previous one. A similar approach to the sequential
                                                                        MIPA detection is analytically tractable only for
                                1. INTRODUCTION                         the asymptotic case, (m-->*o). However, without
                                                                        much loss in efficiency, analytic solutions can be
             In recent years, the evolution       of high speed         obtained   for finite m and for small signal
             sampling techniques and the fact that data from            applications if each sample vector is transformed,
             multi-sensor arrays are temporally and spatially           via a suboptimum projection, into         a    single
             dependent, due to unwanted noise and interference,         variable with a univariate distribution upon which
             created a demand for detection procedures with             the sequential MIPA test is applied. Hence, the
             dependent samples [1]. In addition, it has been            theory of sequential MIPA detectors is extended to
             shown that noise fields in sonar, radar, and some          include processing of Q-dependent samples.
             communication channels are non-gaussian and highly
             contaminated with impulsive noise [2]. In this             In particular, the performance of sequential MIPA
             case, parametric detectors based on a gaussian             detector with Q-dependent sampling is analyzed in
             nominal noise distribution are not appropriate             detail for two important classes of detection
             since   their performance can be significantly.            problems:   The shift-of-mean alternative which
             degraded for other than gaussian and varying noise         finds applications in many data communications and
             environments. Therefore, robust and adaptive to            image processing problems and the change-of-scale
             changing noise conditions detection procedures             alternative which finds applications in processing
             have been introduced [3-5]. Moreover, sequential,          signal data or spectral estimation data from,
             i.e., with variable sample size, operation of the          multi-sensor arrays.
             detectors has been used to reduce the average time
             to decision considerably (up to four times) as                        2. STRUCTURE OF THE DETECTOR
             compared to detectors operating in a fixed-sample
             size mode [11].                                            N test samples, z  i=[x x2F ...,xN] from a
                                                                        stationary Q-dependeni random process with p.d.f.
             A fixed sample size robust detection scheme was            f(xltx      x ), N>Q, form an intermediate test
             introduced by Tsai and Kurz in [4]. The Tsai-Kurz                       Q
             scheme uses a piecewise approximation to the               statistic in the following manner:
             optimum   nonlinearity    function,    known as an         The samples are projected upon the op-direction of
             m-interval polynomial approximation (MIPA), to             an N-dimensional space via a linear
             gain   insensitivity    of performance to highly

                                                  CH2585-8/88/0000- 641 $1 @1988 IEEE

                      transformation, namely z        J'z. where J' is the                the scores of order j, j=0,1,...,p, for,the inter-
                                                iv     N :L          N                      ,   +
                      transpose vector of the transformation.                             val A k(p
                      Let f W be the density of the noise                samples          Independence      between      the      intermediate      testi
                      projeSted upon the 0-direction                                      statistics of (la) is accomplished by using N
                                                                                          consecutive samples to form T.Jz } and                    then
                      fo(P (z IVg  o(V (z tv )IA (z + hOT (z )I A 1(z                     skipping Q-1 samples before obtain"A T           ifz
                                            0                      0
                                                                                          Since Tifz     VI and Ti+,(z    V I are independent, the
                      where gog(.) represents the nominal noise (usually                  sequential MIPA statistic with dependent sampling
                      gaussian) and ho(p(.) represents the heavy-tailed                   is an approximation to the sequential probability
                      contaminating noise of unknown form. The notation                   ratio test [81 and all. the expressions for its
                      IA(zV) represents      the indicator function of                    performance measures, i.e., the average samples
                      interval A, which is 1 if xr=A and 0 otherwise.                     number (ASN) and the power function P(6), derived
                      The set A. represents the interval                                  by Wald are valid. In this case, 9 represents the
                      (a-, a+) in which the nominal noise distribution                    parameter of the unknown alternative, and under
                      0  0
                      is dominant and A     is the complement interval of                 the hypothesis "o-
                      A0                                     +                            Thus (la) represents the classical cumulative sum
                      Assume that the parameters Y and a        have been es-             form for the sequential Q-dependent polynomial
                      timated from a projected noise sam     0 e [5]. The ex-             approximation detector (SQDMIPA) with stopping
                                                             Pi                           boundaries       given      by       a=log[(l-A)/Al         and
                      tension of the robust sequential MIPA to the Q-de-                  b--log[3/(l-a)1      where *I is       the type I error,
                      pendent samples case yields then                                    and -p is the type II error. Sampling continues if
                         n                                                                b <   >Tn< a and one accepts H     0 or Hif if T   n  < b or
                      1@ = ET i f ZP)                                        (la)         Tn -  a, respectively.
                         i=l                                                              The basic structure of the detector is shown in
                      where T.fz I is an intermediate statistic based on                  figure 1.
                      z       Ind defined as
                                     ln !IV- (zi!p)                                             Projected Estivation:
                      T {z                           I (z ) +                                   Leorning
                                        9 (z           A0    iT                                 Y Somple        C@ - Y     SCORES, PARTITIONS
                                          09 i(P                                                               OPTIMUM
                                                                                                               PARTITIONS
                                           p       +                                                           bLuKtb
                                +           ze   C_ z        I    (z         (lb)               Projected                                  ao-
                                     k=1 j=o    1 jkiv i(V    +    ilp                           Received             oly         M     --i-D
                                                                                                z Somple.      a-           NO      I
                                                                                                                    i(P            TEST
                      where gof (.) and gl,(.) are the p.d.f.'s of the                                          YES                     0
                      projected sample in the 9-direction and in the                                                     PARAMETRIC
                      middle portion of the distribution under the                                                       DETECTOR                   T1
                      hypothesis Ho ( noise only conditions) and under
                      the alternative H, (signal corrupted by noise                                              b <T.<Cl              T,
                      conditions), respectively. Moreovert 81 is                 a                        YE                 T,     I
                      preselected,   for design purposes, alternative                                                 NO
                      parameter and may represent the signal level.                                       Tn<b:Ho       Tn> o:H1
                      I+ (ze), k = 0,1, ... Im, are the indicator func-

                      t
                      i4                               +        +       +                 Fig. 1 Structure of the sequential MIPA detector
                      0  a of the intervals           AkV = (a  k-l'  a kI and            with dependent sampling.
                      Akq) = (a k' ak-l 1, which partition the       � trans-             Introduce-                 tT
                      formation of the sample space z,.l and c            are                                          -J @--as- the momeTM-genera-
                                                                      jkT                 ting function of T., and assume fi(t) exists and
                                                                                          is finite for any f@oint t, including the origin.
                                                                                          The solution to the fundamental identity of se-
                                                                                                                       0
                                                                                                         @b
                                                                                                                                   TEST

                                                                                                                             T'
                                                                                                          YES                t
                                                                                                                      NO

                                                                                          quential analysis, [8], reduces then to

                                                                                    642

                                                                                                                                            2
                                          t0 -2 E{Ti I/ Var{Ti                     (2)
                             9->O                                                                                     9   919(z
                 The proof follows        from     the cumulant expansion for                  B 04)                  .29        T 9=0          gw(z  9) dz
                 OW (Cramer [91), where the assumption was made                                                            9 6; (z
                 that T  i   satisfies the strong mixing condition
                                                                                                             OT
                 From the above discussion it follows that the
                 average sample number for the sequential MIPA                                 It is interesting to note that t (0) is free of
                 detector with Q-dependent sampling is                                         any dependence and from (6) and 0(3), [51, is
                                                                                               implied that the same thresholds can be used for
                 E{nJ9J = L(S)/EfT        i 11                 EfT i  )   0        (3a)        near optimum detection under independent                           and
                                                                                               dependent         sampling.          However,       the      optimum
                 E{nle} = - ab / VarfT        il               EfT i  }   0        (3b)        partitions and therefore the scores must                            be
                                                                                               adjusted        to     compensate        for     the amount of
                 where                                                                         dependence        introduced          in      any        particular
                 L(S) = [a(l - e          It ) + b(e at -1)1/ (e      at _e It)                environment.
                                                                                   DO          For the locally most powerful scores, the optimum
                                                                                               performance in a sequential mode of operation is
                 Following the same procedure as in the independent                            achieved if the partitions along the 9-direction,
                 sampling case, [5], it can -be shown that the                                 a     minimize the time to decision, i.e. minimize
                 locally most powerful scores which maximize the                               Ae ASN. Following a similar procedure as in [51
                 efficacy       can       be expressed in terms of the                         and under the assumption of small SIN ratio so
                 partition moments of the projected sample,                                    that powers of 9       1 and e higher than two can be
                  :t(j)           +                +     +                                     neglected, we conclude:
                 E         as c                    D   eEC                                     For the locally most powerful scores, the ASN
                  ok4     +       jk(p             jkq,' kq)                                   achieves its minimum when the expression
                 where          is a (2px2p) determinant with a             typical
                 term     6kwj  E�(j+q)   I  j,q = 01112,...Ip, D         +  is ob-                       P? + B 09                                               (9)
                                oko       +                               kv                   is maximized. The expression above,                         however,
                 tained from              D.  by replacing its j-th          column            defines the efficacy of the fixed sample-size
                                          jk? +(j)                                             test, [51, in which case, the optimum set of
                 by the column of            ekT'        while                                 -partitions is obtained by maximizing (9).
                                                                                               Hence, the following theorem is established.
                  �(j)
                 E                 P      h (z ) dz            and                             THBOREM. the set of partitions which minimizes the
                  OkT                     V 00 1P        (V                                    ASN       for    the     sequential MIPA detector with
                                                                                               dependent sampling is identical to the partitions
                                                                                               which maximize the efficacy of the fixed sample
                                                                                               size tests. The optimum scores in both detectors
                  :L(j)                                                                        are identical.
                 e              +fzj"' ho4zo)l                 dz,,.
                  k(p                     ;-9        8=0                                       It can also be -demonstrated, using the same
                                                                                               approach as in [11], that as the type I and Type
                                                                                               III errors approach zero, the asymptotic efficiency
                 For    small 8 1  the expectation, the variance, and                          of the sequential test compared to its fixed
                 the    parameter t       0(0) reduce to                                       sample size counterpart, is four times higher at
                                                2                                              9=8 I    and 8=8 . The efficiency improves even more
                 EfT 1  10) = (90         1 - e 1  /2)JE PIP   + B 01V             (4)         for values        o? 9 exceeding el.
                            , e2          C
                 Var{T                      + Bor}                                 (5)         The superiority in performance of the sequential
                                          pq)                                                  MIPA detection sch6me over other robust tests has
                 t0  (8)    1     26/e    1                                        (6)         been established already in ref. (5]. In this
                                                                                               paper,       the     performance         of the detector is
                 where                                                                         evaluated by comparing it to the independent
                                m         p  +      +      +(j),                               sampling case while taking into account the time
                     E          2: Z      (D-1k /D- ) -                                        to decision. The efficiency of the robust MIPA
                     PO         k=l--j=o     3 T k(, ek,,                          (7)         detector with dependent sampling T (z                       relative
                                                                                                                                               nD
                 and                                                                           to the independent sampling test T W, for
                                                                                                                                                      nI
                                                                                               sequential operation is

                                                                                          643

                   RE = (ASN   I/ASND) - (tI/tD)                           (10)       optimum scores are estimated recursively using the
                                                                                      stochastic approximation algorithms proposed in
                   where t   I /t D is defined   as the ratio of time                 [5].
                   required for independent      observations to the total
                   time needed for a decision interval, including                     If we let in (11) m-->ao, the efficiency of the
                   enough      delay   to    assure independent samples               SQDMIPA detector with respect to the most powerful
                   [T i 1zV),T i+l 1z 4) M.                                           detector with independent sampling approaches
                   Hence, using,(3) and (10), the relative efficiency                            I D(f;G)       NQ
                   can be expressed in terms of the expectations of                   RE                                                      (12)
                   the two tests                                                         CO      I(f.,G)     N + Q
                             ED{TiIG}           Q                                     where I(f;O) is the Fisher's Information on the
                    RE=                                                               marginal noise density, and I (f;O)               is     the
                             E             N +  Q                                                                            D
                             I {Tile}                                                 Fisher's   Information for f    OT (z (P ) given by
                   where ED{Ti} is given          in (4) and EI(Ti} is the                   +to                    )]2 fo,(.
                   expectation of the Sequential MIPA test with                           f      [f@O(zo) / fo(p (z (P           ).dz 1P
                   independent sampling [5].

                                          3. EXAMPLES
                   In this section, the performance of the sequential                 In the case of gaussian noise, z      T  is also gaussian
                   MIPA detector with dependent sampling (SQDMIPA) is                 and the relative efficiency can be expressed in
                   investigated under the shift-of-mean and change of                 terms of the        covariance      matrix Z      of     the
                   scale alternativesand the optimum parameters for                   N-dimensional noise distribution and the variance
                   zero order ('p=O) and first order (p=l) MIPA are                  62              2/
                   estimated.                                                            as RE= {or      Jl.'J){NQ/(N-tQ-1)} which for N=2
                   betectors based on the shift-of-mean alternative                   and Q=2 is given in terms of the correlation
                   find applications in processing of known signals                   coefficient by RE = (4/3)/(l+r).
                   in additive noise. If the level of the signal is                   For values,of Q>2, and as N approaches infinity
                   8, then the alternative is represented in terms of
                                                                                      the asymptotic relative efficiency reduces to
                   the hypothesis c.d.f. as            F(Z) = Fo(Z--e)      and                                     Q-1
                   F(Z).@FO(Z) for any vector of random variables Z                   RE             Q     1 + 2 2: r     k
                   and 0 > 0.                                                         N-->oo                        k=1
                                                                                      where r    k is the correlation coefficient between
                                                                                      the noise samples x. and x.,       such that li-jI = k.
                                                                                                            .1 1
                   It can be shown that the probability density of                    It should be pointed          oat  that for uncorrelated
                                                                                      samples,     r=O    and    the     relative      efficiency
                   the         projected         sample       reduces        to       approaches Q. Furthermore,         if we also let p,->ao,
                   f(P (z  (P  fo4p (z (P -RN 0) where f T(zT) is the p.d.f.          we obtain the same result as Dwyer and Kurz
                                                                                      derived for the sequential         partition detector in
                   .of    the   projected     sample under the unknown                [121. Namely,
                   alternative, fo(p(.) is the p.d.f. of the projected                                          Ts
                   sample under the hypothesis,. and                                  RE                Ts2        r(r) d-C
                          N                                                           NIQ ->*0               0
                   RN     2@ji                                                        where T is the sampling interval for uncorrelated
                          i=1                                                         samples  8 and r(T ) is the correlation coefficient
                   The hypothesis-alternative separation parameter                    in terms of the translation of time between two
                   now becomes A= RNO and the direction 4v is chosen                  dependent samples.
                   such that this separation, and therefore the SM                    For finite values of N and for Q=2, the relative
                   ratio for the transformed vector z,,/ is maximized.                efficiency is shown in figure 2.
                   Hence, Ji = 4 -N M.
                   Moreoverr the optimum partitions which minimize                    It is more tedious to obtain the above results in
                   the ASN and therefore maximize E            are estimated,         the case of contaminated noise. For example, a
                   via a gradient search routine on (7) by letting                    N-dimensional density with marginal densities of
                   p=O and p=l. Thus, the partitions for the zero                     the Huber mixture type is typically represented as
                   order and the first order MIPA can be obtained. On
                   the other hand, the partition moments and the

                                                                                 644

                                          N                                                                                   R@@
                                               (N                                                                             1.50                       . . . .
                        fZ (z)           E       i) (1_ 6)i 6N-i f             l(i)2(N-i)       (z)                           1.45-
                                         1=0
                                                                                                      (14)
                                                                                                                              1.35-        A,               A-A
                        where Z is a N-dimensional vector of random var-                                                      1.30-             CB
                        iables, Z = [ x1f x             21 ... 1 X  N  ], with marginal den-                                  1.25-                  C                   C
                        sities f     X (x) = (I- t) f         I (x) +         ef 2(x)                                         1.20-        P    =0           P=1, N=3
                        .and . f1@i)2N(N-i)         Z. is the joint density of N                                              1.15-
                        variables out of which i have marginal density                                                        1.10-        A A                                       A--
                        f1 (x) and the remaining (N-i) have                                    marginal                       I.05-                      C                     C
                        density f      2 W.                                                                                   1.00-                  P=               1, N=2
                                                                                                                              .95-                                                           10
                                                                                                                              .90                                                    ,    I C,
                                                                                                                                      0                  .8  1.0 1.2 1.'4 1.6 1.8        2.0-

                              REA                                                                                             p: order of       MIPA, N=Q, m--3
                                1.8-                                                                                          Degree of contamination E: A: 0 & 1, B: 0.01
                                                                            r=0.05       N--l-o                                                                            C: 0.9
                                1.5-                                                                                  Fig. 3. Relative efficiency, Shift alternative
                                                                                               oo                     The one-sided change of scale alternative emerges
                                                                                                                      in detection problems dealing with spectral data
                                1.0-                                                                                  and transmission through dispersive media. The
                                                                                                                      distributions                 care         one-sided,             and          the
                                    -                                                                                 change-of-scale effects a stochastic ordering,
                                                                                                                      i.e.,
                                .5-
                                    -                                                                                 F(Z).LFO(Z)          for       any       vector Z. Specifically,
                                                16            20            3             40 N                        F(Z)=FO{Z/(l-te)}, e>O, and the density of the
                                                                                                                      projected sample reduces to
                                                                                                                      f'P(Z'@) = fo'@fzq'/(l+q)) / (1+9).
                        Fig. 2 Relative efficiency of SQDMIPA with                                                    As in the shift alternative case, it can be shown
                        respect to the MIPA detector, Q=2                                                             that the transformation which maximizes the SIN
                        In the case of gaussian noise contaminated by                                                 ratio is
                        high power noise samples, f                  1 (x) = N(0,6?) and                              Ji =VN / N, i= 1,2,...,N.
                        f2(x) can be represented by                                                                   The      relative efficiency with respect to the
                                    2                                                                                 independent sampling detector is obtained by (11)
                        N(O, ff     2) where             C 2 >> C    I'                                               and (4), and the asymptotic relative efficiency
                                                                                                                      (m->oo) reduces to
                        In this case, the relative efficiency with respect
                        to the independent sampling detector can only be                                              REO'= (f-D /CI )[Q/(N+Q-1)]
                        evaluated using numerical methods on (12). For
                        finite m, in particular, the relative efficiency                                              where E         Dis the efficacy of the SQDMIPA detector
                        is depicted in figure 3 in terms of the                                                       as m->aof
                        parameter a        0  , where         a =a   +    and -a =a           It is                                   + Q4                                       2
                        shown that for both ?irsot and second                                       order:            E               f    [1+Z {f' (Z )/f (z M foP                     (z      dz
                        polynomial                approximations,                bivariate             and              D       -00               (P ov (P          O(P T
                        trivariate dependence, and for                     several values of
                        contamination parameter c the                      relative efficiency                        and      E I      is obtained by (15) if foV(z;,) is
                        is almost independent of the selection of a                                    and
                                                                                                 0 .                  substituted by the marginal density of the noise
                        maintains near optimum performance even for high
                        degrees of contamination.                                                                     samples, fo(x).
                                                                                                                                                B    C
                                                                                                                                                                   C_
                                                                                                                                                                         C_

                                                                                                                                           P @__Co                P

                                                                                                              645

                Application: The change of scale alternative-can                       2.0
                model several practical problems including power
                spectral analysis and processing of sonar, radar,.                     1.9-
                and seismic data. Spectral analysis of time series.
                data is performed by transformation of              time.              1.8-
                segments into sequential estimates of the spectrum
                of the received signal. The problem is one of                          1.7- r=0.05, 0.01
                detecting narrow band signals in background noise.
                Assuming constant signals        in    frequency     and               1.6-
                gaussian noise at the input, the optimum detector
                incoherently integrates the spectrum for a period                      1.5-                   r=0.223
                of time before detection. The integration is
                equivalent to averaging the measurements of the                        1.4-
                spectrum over time. The sequential MIPA test may
                give a     useful     alternative    to    integration,                1.3-
                providing    robustness      which   averaging cannot
                provide.                                                               1.2'-  -   -
                In this case, the spectrum analyzer may               be               0  .2  .4 .6      1.0 1.2 1.4 1.6 1.8 2.0
                considered to be a bank of narrowband filters of
                width 2&Hz, each followed by a squaring device                IFig.    4. Relative efficiency vs a
                and the SQDMIPA detector. With gaussian noise at              scale alternative, m=21 P=O          0
                ,the input of the filters, the second             order
                probability density of the output of the squaring             On the other hand, if the noise at the input of
                device can be expressed in terms of a series                  the filters is contaminated gaussian of the type
                expansion [13].                                               represented     by    (14), then the second order
                                                                              probability density at the output of the squaring
                Then, the probability density         of the projected
                noise samples, for,z >0, is                                   device is obtained using a similar procedure like
                                       0                                      the one used by Rice in [14]. In this case, the
                f (z           r212 6  2) expf-z F2/262                       efficacy     of   the    SQDMIPA detector has been
                 Of T                            T                            evaluated and its relative efficiency versus the
                        00     n                                              most powerful detector with independent sampling
                           (r2) fL (z &121)          L   (z r2126 2           (M->oo) is shown in fig. 5 as a function of the
                                   2n (P             2n+l                     contamination     parameter     e and     for     several.
                        n=o                                                   correlation coefficients r.
                where L n(x) is the Laguerre Polynomial.
                If a narrow band gaussian signal is added to
                the noise, the change-of-scale alternative may be                      1.4
                used to model the probability density and 9 may
                represent the unknown SM ratio.
                The performance of the most powerful detector is                       1.3      r:O '& 0.05
                obtained by letting m-> w. AS m->oo the efficacy                                     r= 0.1
                of   the    detector    becomes     2/(l+r2)    and is                 1.2             %0.223
                independent of the variance of the noise. Hence,
                the   relative efficiency with respect to the                          1.1
                optimum detector with independent sampling reduces
                to (4/3)/(I+r2                                                         1.0
                                                                                              .05     OJ     0.15   0.2     0.25
                For finite m, the optimum design parameters of the,
                detector have been estimated following the same
                procedure as in the shift-of-mean alternative case
                and for several correlation coefficients. The                 Fig. 5. Relative efficiency vs the contamination
                relative     efficiency    with    respect    to      the     parameter       Scale alternative.
                independent sampling detection scheme is displayed
                in figure 4 as a function of a where                          From figures 2-5 it is concluded that the MIPA@
                 +                               0                            detectors with dependent sampling improve their.
                a-   E{z    + a                                               performance considerably as compared to the MIPA
                                                                                                    &L-0=02
                                                                                       2@                 23

                               0                                              detectors     operating with independent samples.
                                                                              Especially in the case of the change-of-scale
                                                                              ,alternative, the efficiency increases up to 80%.

                                                                         646

                                                                       7.   M. Woinsky and    L. Kurz, "Nonparametric De-
                               4. CONCLUSIONS                               tection Using Dependent Samples,n       IEEE
                                                                            Trans. on Info. -Theory, Vol. IT-16,
             In this paper, the effects of dependent sampling               PP. 355-358, May 1970.
             on sequential m-interval polynomial approximation
             (SMIPA) detectors is considered. First, the theory        8.   A.   Wald, Sequential     Analysis, John Wiley
             of  SMIPA    detectors    is extended to include               and Sons, New York, 1947.
             N-dimensional   processes    by    introducing      a
             suboptimum    linear     transformation    from     an    9.   H. Cramer, Mathematical Methods of Statistics,
             N-dimensional space to one dimensional space. It               Princeton Univ. Press, Princeton, N.J. 1964.
             is shown that the same partitions and scores lead
           ,to optimum performance for both the fixed sample           10.  M. Rosenblatt, "Independence and Dependence,"
             size and the sequential MIPA detectors even though             Proceedings of the Fourth Berkeley Symposium
             the sequential operation reduces the average time              on Mathematical Statistics and Probability,
             to decision by a factor of four. Moreover, the                 Vol. 11, 1961.
             decision thresholds remain     the same as in the
             independent sampling case,      and   the    optimum      11.  R. Dwyer, "Sequential Partition Detectors with
             partitions and scores are      easily adjusted to              Applications," PH.D. Dissertation Polytechnic
             compensate for the dependence  of the test samples.            University, 1976
             Efficiency calculations have   been made for the
             shift-of-mean      and       the     change-of-scale      12.  R. Dwyer and L. Kurz, "Sequential Partition
             alternatives. For contaminated noise densities and             Detectors with Dependent Sampling, " Journal
             for zero and first order MIPA, numerical results               of Cybernetics, Vol. 10, pp. 211-232, 1980.
             show   that   both   alternatives    give improved                                               -
             efficiencies under the SQDMIPA designs as compared        13.. J. Barrett and D. Lampard, "An Expansion for
             to the sequential MIPA detection schemes.                      Some Second-order Probability Distributions
                                                                            and its Application to Noise Problems, IRE
             It should be pointed out that the SQDMIPA    detector          Trans. Info Theory, Vol. IT-1, pp. 10-15,
             can be easily implemented. All the parameters can              1955
             be estimated from a noise sample and updated
             periodically, via parallel processors, without            14.  S.O. Rice, "Mathematical Analysis of Random
             interrupting the detection process. Thus, the                  Noise," Bell Systems Technical Journal,
             detector can adapt its performance to slowly                   Vol. 23, p. 78, 1945.
             changing noise environments.
                                                                                          ACKNOWLEDGMENT
                                  REFERENCES
                                                                       This work was supported in part by the Manhatttan
             1.  R. Dwyer and L. Kurz,"Characterizing Partition        College Faculty Grant and RCA
                 detectors with stationary and Quasi-stationary
                 Markov Dependent Data," IEEE Trans. on       Info
                 Theory, Vol. IT-32, pp 471-482, July 1986

             2.  R. Dwyer, "A Technique for Improving Detection
                 and Estimation of Signals Contaminated by
                 Under Ice Noise," J. Acoust. Soc. of Am.,
                 Vol.   74, pp. 124-130, 1983.

             3.  P. Huber, "A Robust Version of the Probability
                 Ratio Test," Annals of Math. Stat., Vol. 36,
                 pp. 1753-1758, 1965.

             4.  C. Tsai and L. Kurz, "An Adaptive        Robust-
                 izing   Approach to Kalman Filtering,"
                 Automatica, Vol. 19, No 3, pp. 279-288, 1983.

             5.  E. Voudouri and L. Kurz, "A Robust Approach
                 to Sequential Detection," IEEE Trans.        on
                 Acoustics, Speech and Signal Processing,
                 Vol. ASSP-36, pp 1200-1210, August 1988

             6.  E. Voudouri and L. Kurz, "Robust m-Interval
                 Polynomial Approximation      Detectors    with.
                 Dependent Sampling" Proceedings of the nine-
                 teenth Conf. of Information Science and
                 Systems,   pp. 132-137, March 1985.

                                                                   647

                                           A SHIPBOARD DATA, ACQUISITION, LOGGING AND DISPLAY SYSTEM

                                                                Geoffrey Samuels

                                               Rosenstiel School of marine & Atmospheric Science
                                                               University of Miami
                                                              Miami, Florida 33149

                                      ABSTRACT                              the VMS operating system that runs on the microVAX.
                                                                            This system was modelled after a set of CTD data
                 A shipboard system for acquisition and logging of          acquisition and logging routines developed at the
                 oceanographic data is under development at the             University of Rhode Island.
                 University of Miami utilizing seagoing microvAx
                 computers running the V14S operating system.      The                2. DESCRIPTION OF THE SYSTEM
                 separate functions of data acquisition, logging and
                 display are performed by independent programs.             one feature of VMS that is used is the ability of
                 Data are transferred between programs by using a           independent programs to share the same data among
                 common database resident in the computer memory.           themselves.  This can be accomplished in a number
                 An example of the system is a working system of            of ways: one way is using what is called a
                 routines to acquire, log and display oceanographic         shareable image. A shareable image is a piece of
                 data collected by a shipboard SAIL (Serial ASCII           software code that can be accessed by two or more
                 Instrumentation Loop) system.                              separate computer programs.       By installing a
                                                                            FORTRAN named COMMON block or a C external data
                                                                            structure as a shareable image, a common data
                                   1. INTRODUCTION                          buffer can be established and accessed by several
                                                                            programs simultaneously.     This has enabled the
                 one of the requirements of an oceanographic                separate functions of data acquisition, data
                 research cruise is the need to gather data and to          logging and data display to be split into separate
                 make it easily available to investigators.          A      independent programs; they communicate between
                 typical cruise may need to collect CTD data,               themselves by sharing the same common data buffer.
                 navigational information, Acoustic Doppler Current         The data acquisition program does the data
                 Profiles and meteorological data.                          collection, either passively from instruments that
                                                                            output data automatically or actively by issuing
                 In the past at the University of Miami many                data requests to instruments that must be polled.
                 different types of data were individually collected        The program then stores the data in the common data
                 by dedicated microcomputers. For example CTD data          buffer along with a timestamp showing the time of
                 acquisition would be done by one microcomputer             acquisition.   An independent data logging program
                 while shipboard navigation would be collected by a         accesses the data buffer and stores the updated
                 separate microcomputer.      The data acquisition,         data on disk.    Another program can take the raw
                 logging and display would be done by a single              data in the data buffer, apply calibrations to it
                 monolithic computer program.    There were problems        and store the calibrated data in a separate
                 with this approach: since the programs had to do           calibrated common data buffer which can be accessed
                 several functions they tended to be large and              by display and plotting programs. The speed of the
                 complex.  It was difficult to modify and maintain          microVAX permits rapid updates of the common data
                 these large programs and often memory limitations          buffer so that the data can be displayed or plotted
                 of the computers made it impossible to extend the          on a near realtime basis.    Figure 1  shows a block
                 program's capabilities.                                    diagram of the process.

                 Recently, technological advances have introduced           Each data source can have its own set of
                 computers that are comparable to large mainframes          acquisition,   logging,   calibration   and display
                 in speed and memory, yet are physically small              routines communicating via common data buffers.
                 enough to be practical, seagoing computers. At the         The rest of this paper will provide an example by
                 University of Miami Rosenstiel School of marine and        describing a system to acquire and     log shipboard
                 Atmospheric Science (RSMAS), microVAX computers are        SAIL (Serial ASCII Instrumentation Loop) data.
                 being introduced for seaboard data acquisition and
                 logging. These computers are fast enough and have          3. MULTIPROGRAM SAIL DATA ACQUISITION AND LOGGING
                 enough memory to run data acquisition programs that
                 previously   required *three    or   four    separate      The SAIL system allows access to a variety of
                 microcomputers.     At RSMAS, a system of data             instrument modules monitoring various shipboard
                 acquisition, logging, and display routines is being        parameters-    It i   described more fully in the
                 developed to take advantage of certain features of         ANSI/IEEE standardl@.   Typical parameters measured

                                                       CH2585-8/88/0000-648 $1 @1988 IEEE

              on board University of Miami vessels include ship            calibration program which reads the raw data in the
              speed and heading, anemometer wind speed and                 common data buffer, applies a set of calibrations
              direction,    thermosalinograph     temperature    and       to the data and stores the calibrated data in a
              conductivity, wet and dry bulb temperatures and              separate    calibrated     common     data     buffer.
              barometric pressure. Each module is independently            Calibration constants can be kept and read from
              polled by the SAIL controller; upon receipt of an            separate calibration files. A SAIL display program.
              .attention character and a unique two-digit address,         accesses the calibrated common data buffer in much
              a module will transmit an ASCII data message                 the same way the logging program accesses the raw
              followed by a message termination character.                 data buffer and displays the current calibrated
                                                                           SAIL data on a terminal.        In a multi-terminal
              On the microVAX system the SAIL system controller            situation several copies of the display program may
              is the basic data acquisition program. The program           be run, making for convenient display of shipboard
              (called the SAIL "grabber") maintains a list of              navigational and environmental parameters.
              active SAIL adresses in the common data buffer. It
              polls each module address and stores the received            Future implementations of the system will include
              ASCII data message along with a timestamp of when            realtime data plotting of the calibrated data
              the poll was issued.     After all addresses in the          utilizing terminal graphics or pen plotters.
              list have been polled, the grabber program places a
              "lock" upon the common data buffer and transfers                                 4. CONCLUSION
              the data it has acquired.       It then releases the
              lock on the common data buffer and begins another            By utilizing interprocess communication through
              set of polls. If a module fails to respond after a           shareable image common data buffers, the different
              specified time, or if invalid data is received, an           functions of data acquisition, data logging and
              error message is sent to the console of the                  data display can be accomplished by independent
              microVAX and to an error logging program.          The       programs.   This allows flexibility in meeting the
              grabber program is maintained as an independently            requirements of a particular principal investigator
              running process updating the common data buffer at           (or investigators) for a research cruise and makes
              the end of each set of polls, typically ten to               it easier for future expansion of the system.
              fifteen seconds, depending upon the number of
              selected modules and the length of the data                                   5. ACKNOWLEDGEMENTS
              messages.   Communication with the grabber program
              is accomplished via the common data buffer.        The       I wish to thank  the National Science Foundation for
              list of  active SAIL modules can be modified at any          its financial support of the project. I also wish
              time by an independent program.       Also, if it is         to thank O.B. Brown, J.W. Brown, R.H. Evans, A. Li
              desired  to halt the grabber program, a flag value           and G. Basham for their many helpful comments and
              can be   set in the common data buffer by another            guidelines.      I also especially thank L. Covington
              program.                                                     for demonstrating the feasibility of the project.

              Actual   logging of the raw data. messages is                                    6. REFERENCE
              accomplished by a separately running logging                 1
              program which can be set to log any or all of the            IEEE Standards Board, "IEEE Standard Serial ASCII
              SAIL modules. The logging program only checks the            Instrumentation     Loop    SAIL    Shipboard     Data
              common data buffer at set intervals; a typical               Communication" ANSI/IEEE Std 997-1985, 1985, 12pp.
              sampling interval would be five minutes. At that
              time the logging program places a lock upon the
              common data buf fer and makes a copy of the data.
              It then releases the lock so that the grabber
              program can continue updating the buf fer.         The                        Data            Data
              logging program checks this data for each SAIL                                Source       kcquisition
              address to be logged. If the module data has been                                             Program
              updated since the last logging check, the raw SAIL
              data message, along with its timestamp, is written
              to a disk (or tape) file.                                                     Raw              Common
                                                                                            Data           Raw Data
              Since the data acquisition and data logging pro-                              File             Buffer
              grams are independent of each other, communicating
              through the common data buffer, more than one
              logging program can be run at the same time. One                              Raw
              investigator may only want one subset of all                                  Data            Data
              available SAIL parameters logged every 30 minutes,                            Logger       Calibration
              while another     investigator might desire        all
              parameters logged every five minutes.              This
              flexibility was one reason for splitting the                               Realtime
              functions of data acquisition and data logging.                               Display
                                                                                            Program          Common
              The ASCII data stored in the common data buffer    has                                   -.Calibrated
              to be calibrated before it can be displayed or                                Realtime         Data
                                                                                                             Buffer
                                                                                            @Raw
                                                                                            r
                                                                                            F@
                                                                                            at a
                                                                                              le

              plotted.     This is accomplished by a separate                               Plot
                                                                                            Program

                                                                                                   Figure I

                                                                     649

                                  OFFSHORE OCEANOGRAPFUC APPLICATIONS FOR BATTERY-POWERED, HIGH-END
                                                                       MICROPROCESSORS

                                                             Carroll V. Bakerl and Wm. T. Whelan    2

                              'Skidaway Institute of Oceanography                                    20cean Communications Systems, Inc.
                                     Post Office Box 13687                                                    2430 Industrial Drive
                                   Savannah, Georgia 31416                                                Panama City, Florida 32405

                                           ABSTRACT                                    operational amplifiers contributed useful performance and
                                                                                       energy economy improvements as well in the new design.
                    The availability of the all static CMOS 8OC88 micropro-
                    cessor and a commercial, single board computer featuring           In this paper, we briefly describe three offshore applica-
                    it has presented the designer of battery-powered, unmanned         tions which make use of the 80C88 monoboard computer.
                    oceanographic systems with a new, powerful building                Two of these were developed, solely, by the senior author
                    block. Three different, oceanic applications are described,        and the staff of the Skidaw.ay Institute of Oceanography
                    which have substantially benefited from this powerful new          (SKJO), a unit of the University System of Georgia,
                    tool.                                                              located on Skidaway Island near Savannah. The third,
                                                                                       which is discussed first because of its complexity, has been
                                                                                       a joint development by SKIO and a supporting contractor,
                                                                                       Ocean Communication Systems Inc., of Panama City,
                                                                                       Florida.
                                      1.0 INTRODUCTION

                                                                                                 2.0 THE LORAN REPEATER BUOY.
                        The ubiquitous microprocessor revolution of the past
                    decade has been rather slow to make inroads into applica-          The first application of the 80C88 computer discussed is
                    tions aboard "stay-behind" instruments used in coastal and         that in a free-drifting buoy system, designed to measure
                    oceanographic sensing. The reasons for this were several,          surface or near surface, oceanic or estuarine water circula-
                    among which include, the electrical energy demands of              tion. The buoy in which the computer is installed provides
                    most devices, and the relatively modest computer power of          a minimal wind cross section so its motions will be dom-
                    the available hardware. Until 1984, most of the "CMOS              inated by small water movements. The water drag is
                    CPU" hardware was approximately 50 percent NMOS tech-              enhanced by the use of an underwater 'sail' or current trap
                    nology. Operations in the "powered-down" mode reduced              approximately 4 feet on a side. The trap depth setting is
                    the battery demand by a relatively small amount when               selected for the water depth of concern. This can range
                    compared to what a 100 percent CMOS microprocessor                 from surface to about 125 meters. The buoy is 10 feet
                    could do. The few, true, static CMOS CPUs had modest               long. It has a cylindrical electronic housing 20-inches long
                    computing capacities and required unfamiliar programming           and 8-inches in diameter, which is located below the water-
                    skills. Despite this, there were enough applications made          line. Its launch weight, fully ballasted, is 130 lbs.
                    to indicate the future course of events. The need for an
                    interrupt driven engine with sufficient computing power to         In 1977, the original Loran repeater buoy system was
                    make a difference and which could provide static sleep             developed by the contractor with support from the Geogra-
                    between interrupts was obvious. Harris Semiconductors              phy and Earth Sciences Branches of the U.S. Office of
                    met the need with its 80C88. For the first time, a powerful        Naval Research (ONR). This support was part of ONR's
                    microprocessor was available which was capable of bring-           ongoing commitment to transfer unclassified aspects of a
                    ing the desk computer to sea and running it (for a long            military development program for HF, Over-the Horizon
                    time) from a handful of flashlight batteries! Onset Com-           Radar (OTHR) to the civilian, scientific community (Ref.
                    puters developed a single board computer system which              1). The present SKIO contractor worked many years in the
                    was designed to exploit the opportunities offered by a             ONR radar program where he was also associated with
                    powerful processor, stingy of battery capacity, in isolated,       development of several large ocean data buoys.
                    Istand alone' situations.   This provided a convenient,
                    interrupt-driven computer suited to the type of applications       2.1 Communication Considerations
                    discussed here.
                                                                                       The Model A-8 Loran buoy employs an advanced HF com-
                    The growing capabilities of new, micropowered, precision           munication system over which it periodically broadcasts its

                                                              CH2585-8/88/oooo- 650    $1 @1988 IEEE

                   Loran position. The position information is obtained from              2.2 Data Protection
                   a minimally-modified, automated Loran Receiver-Navigator
                   carried aboard the buoy. After many trials we have settled             It would be most unusual when the position data from the
                   on any of several Sitex CMOS models. The particular                    Loran Buoy could not be delayed for a period of at least a
                   model used is mission-dependent. The buoy can be                       few hours until transmission could be made at a better time
                   received by an unlimited number of properly equipped sites             thus avoiding interference limitations. This option has
                   located within the coverage area of the broadcast. For the             been built into the buoy data system in two ways: the first,
                   electromagnetic surface wave mode of HF which is used at               a software solution and the second, a more , complex,
                   sea, this coverage is a circle approximately 200 miles in              hardware approach. Both require the inclusion of static
                   diameter (Ref. 2). Several dozen buoys can share a single              RAM CMOS memory in the buoy. Sixty five thousand
                   transmission channel. It is noteworthy that the electromag-            five hundred and thirty five bytes of SRAM provides
                   netic surface wave BF propagation employed by the sys-                 sufficient nonvolatile storage for all of the data collected
                   tem, termed Mode 1, permits buoy broadcast reception for               from an entire cruise of a drifting buoy. With the data
                   only a few miles inland from the coast (Ref. 3).                       stored on board, it is a simple matter to protect nighttime
                                                                                          collections by one of the following three approaches. First,
                   System transmitters and receivers are specifically designed            program the buoy to routinely transmit the 'at-risk' night
                   to process the coherent phase modulation/demodulation and              data during daylight of the following day; second, include
                   the encoding/decoding employed for error control.                      a command link to a receiver on board the buoy and
                   Extended operational battery life is obtained through exten-           request a repeat of  ' specific portions of the data record
                   sive use of CMOS technology throughout the system and                  which may have been lost to noise or interference; and
                   high efficiency, MOSFET, switchmode transmitters. The                  third, recover any missed data from, the buoy by direct
                   application of advanced signal processing techniques per-              hardwire 'conversation' via the user's programming umbili-
                   mit the use of only modest levels of radiated power for                cal cable attachment when the buoy is recovered aboard
                   effective cornmunications over the range supported by the              ship. Actually, all three options are available in the Loran
                   HF surface wave mode noted above. Most Loran opera-                    buoy discussed here. For the command receiver option,
                   tions use surface wave mode since the modest transmission              the receiver cannot be operated continually, since the
                   ranges not only suit the scale of local problems, but                  energy penalty would be prohibitive. Therefore, at known,
                   because the distance between buoys and the intended                    fixed times, the buoy management computer periodically
                   recovery ship(s) prudently should not exceed 50 to 100                 activates the energy-conservative, onboard command
                   miles (Ref. 4).                                                        receiver. The latter is then available for receipt of instruc-
                                                                                          tions regarding retransmission of specific portions of the
                   For mode 1,     surface wave propagation, the maximum                  data or changes to the user-installed data collection and
                   power output    provided by the buoy transmitter at the                reporting schedule. All stored data is formatted in the
                   antenna base   is approximately 0.8 watt. With the usual               packet mode. The packet or "ping-pong" mode of data
                   efficiency of small antennas at 4 Mhz, the effective radi-             transfer, with its immediate error correction capability, is
                   ated power level is in the range of 30 to 50,milliwatts.               also available as an operating option.
                   This has been judged to be a reasonable compromise
                   between the buoy's battery operating life and measured                 2.3 Other Data-Gathering Capabilities of the Loran-
                   reliability of 300 baud message receipts at the 100 mile               Repeating Buoy
                   radius of the diffraction zone. Commonly, reception under
                   these conditions can     be anticipated to be* satisfactory            The buoy can be provided with a suite of extremely low-
                   throughout the day and approximately one-half of the dark,             powered sensors to report on the environment which they
                   sunset-to-sunrise hours. During the first half of the average          traverse. Optional CMOS ADCs convert (12-bit plus sign)
                   night, inteference from other world users can limit message            the analog data for digital transmission by the system.
                   copy to ranges of 50     miles or less. The presence of a              This option can substantially extend the scope of a circula-
                   severe thunderstorm, at  night, which is located within line-          tion study for efforts, such as oil spill studies (Ref. 6).
                   of-sight of a particular receiving station, can eliminate any
                   useful reception at that station until the storm dissipates or         2.4 Buoy Data Receiving Terminals
                   moves on.
                                                                                          Multiple buoys time-share a single radio channel. This
                   The performance cited in the preceding paragraphs is con-              greatly simplifies the cost and complexity of an extended
                   siderably improved over that of traditional HF (civilian or            drift study in, say, the Gulf Stream where relatively large
                   military) circuits. This improvement reflects application of           areas must be covered. The receivers are specialized
                   a number of modern signal and data processing techniques               because of the complex signal processing they must per-
                   (Ref. 5) combined with an innovative, small antenna on the.            form (Ref. 5). Attempts to use commercial receivers are
                   buoy.                                                                  generally disappointing, and since the system-specific
                                                                                          receivers are about twice the going commercial price of a
                                                                                          good 'ham' receiver, efforts to minimize the number of
                                                                                          receiving positions are worthwhile. Because of elec-

                                                                                   651

                   tromagnetic noise produced by ship's machinery, special
                                                                                                                                                  @A- it
                   active, noise-reducing antenna systems are available and
                   advisable for reception aboard most research vessels.

                       3.0 A 80C88-BASED COMPUTER APPLICATION
                                  TO COLLECTION OF OFFSHORE
                                      ENVIRONMENTAL DATA
                                                                                                                                                J,
                   Our second application of a computer-based system
                   management (Fig. 1A) was for the update of an offshore
                   sea-air environmental monitoring station. The original sta-
                   tion, previously described (Ref. 7), is located on an
                   offshore platform, 17 miles from the data collection center
                   at'SKIO on Skidaway Island. It recently became necessary
                   to convert this diesel generator facility to unattended,                                                                            A
                   solar-powered operation.
                   In cooperation with the U.S. Coast Guard (USCG), Skida-                         Fig. 1.    A.) 8CO88 based computer.
                   way maintained an air-sea sensor system and VHF radio                                      B.) VHF ra
                   (Fig. 113, 2) data link to the Institute. Commercial grade                                              dio transmitter.
                   prime power was platform-generated and it supported the
                   SKIO system. In 1987, the USCG converted to a solar-
                   powered unmanned operation, and SKIO redesigned its
                                                                                                                 @,Z
                   environmental station similarly. Wherever possible, our
                                                                                                                                            @AA,
                   sensor system was reconfigured to minimize its electrical
                   load. An added premium was placed on system reliability,
                   since an 8-hour round trip cruise is required to correct any
                                                                                                                        4ro kA
                                                                                                                                                   I YX
                   onsite difficulty.

                   The new system management computer selected was the
                   same single board, 8OC88 computer employed by the
                   Loran buoy. The sensors managed and reported by the
                   new system are included: 1. Anemometer, reporting wind
                   speed and direction; 2. Ten thermistors; two for air tem-
                   perature and eight for water temperature at increasing
                   depths; 3. Subsurface pressure gauge for wave and sea
                   level measurement; 4. Barometer; 5. Battery terminal vol-
                   tage and charging current. All sensor outputs are con-
                   verted to rational engineering units by the onsite computer                                 Alk
                   prior to transmission to the mainframe at the Institute.                       Fig. 2.     VHF radio antenna.

                   3.1 Solar Power Supply and Load Details; Communications

                   A pair of solar panels (Fig. 3), supplied by Solarex Corp.,
                   provides up to 5 amperes at 15.8 volts under bright, sum-
                   mer conditions. Each panel area is 2 square feet. They
                   are directly connected to a pair of large, paralleled, 12 volt,
                   industrial lead-acid batteries. The combined battery capa-
                   city is 200 ampere-hours and is sufficient to eliminate the
                   need for charging regulators. This sytem has proven ade-                               tit                  51,
                   quate for long winter nights and protracted periods of con-
                   current, overcast, daytime weather. The power system has
                                 -free since its installation 14 months ago and
                   been trouble
                   has shown no signs of deterioration. Repair of minor wind
                   and wave damage to several of the sensors or their wiring
                   has been the only required maintenance to date.

                   The significant load is the 50 watt demand of the VHF
                   transmitter (Fig. 1B) which operates 6 minutes of each                         Fig. 3.     Solar panels.

                                                                                       652

               hour, 24 times each day. The sensor and computer loads                      mately I square meter in cross section at the open door
               are negligible in comparison with the transmitter load. It is               and can be sequentially opened and closed on command
               interesting that the commercial anemometer package, which                   from the user's keyboard. The on-deck weight of the sys-
               we chose not to modify, draws 100 milliamperes compared                     tem is approximately 1000 pounds and* it is readily handled
               to the "fully-up" computer demand of 20 milliamperes.                       by the ship's hydraulic hoist gear as a side trawl.

                        4.0 MICROPROCESSOR APPLICATION                                     4.1 Sensor-Derived Information Continuously Available on
                            FOR A SMART PLANKTON NET                                       Data Screen

               An instrumented, towed, underwater, plankton-collection                     When making a towed collection, the investigator normally
               net has been developed by SKIO. The system which per-                       seeks to tow the net at a selected depth from a given start-
               mits 'user friendly' control by the scientific investigator on              ing position to some approximate terminus along a
               the towing vessel has been a long-standing need (Ref. 8).                   preselected heading. To assist in this his data display
               However, the conflicting requirement for maintaining ship's                 screen is updated with course and ship's speed information
               time productivity while still permitting the flexibility of                 from the ship's navigation and pilotage equipment. An
               collection operations, has made this a difficult task.                      important tow parameter is the water' throughput rate as
               Experience suggested that a major improvement would                         well as the accumulated water flux as the tow is underway.
               result if a system could be devised to provide all concerned                The net carries a series of sensors which provide the com-
               with a clear picture of precisely what is occurring beneath                 puter with a constant update of raw data from which it can
               the surface as the net is towed. The ability to know the                    calculate and display volumetric data in real time. The
               position as well as the course of the net, in three                         sensors provide the following information: 1. The timing
               dimensions, at all times in c    Ion-s.i.der.e.d eIs.sential-. ItIis  criti- of all door openings and closings and the continuous status
               cally important to minimize the number of times the net                     of all doors; 2. The readout of a precision inclinometer
               must be raised for any reason other than legitimate                         which measures the vertical angle, and its variations, of the
               recovery of the collection. This is especially the case                     net and its doors; 3. The instantaneous flow rate of water
               where deep towing is involved. Rugged, dependable door                      into the door(s); 4. The precise depth of the doors; 5.
               latches on the nets and trustworthy, on-deck status displays                Water temperature; 6. Shallow (0-100 meters) and deep
               of the door conditions are essential to user confidence.                    (0-1000 meters) hydrostat readouts for precise depth track-
                                                                                           ing; and 7.       Continuous monitoring of the watertight
               The new net system employs the same 80C88 microcom-                         integrity for all dry chambers. A micropowered conduc-
               puter to manage the array of seven (7) stacked nets in the                  tivity cell may be added by the time of this publication to
               single, towed package (Fig. 4). The nets are each approxi-                  provide complete CTD profiling capabilities while raising,
                                                                                           lowering or towing the nets. Computation of all the criti@
                                                                                           cal ship's handlers are performed and routed the appropri-:
                                                                                           ate display terminals on the bridge and deck.
                                         A'.@ "PI,                                         4.2 Communications B
                                         "A                                                                            etween Ship Deck and Net
                                                                                           The coaxial two-wire,       steel tow cable is 2500 meters in
                                                                                           length and is carried on a deck winch. All data communi-
                                                                                           cations signals as well     as the continuous, constant recharge
                                                                                           current of 0.4 ampere       for a peak-handling, 12-volt battery
                                                                                           in the submerged package, are passed over the total cable
                                                                                           length. The compliance of this 'smart', constant current
                                                                                           charger must be approximately 125 volts to overcome the
                                                                                           resistive drop in the long cable. Full duplex communica-
                                                                                           tion is maintained between the deck user's terminal and the
                                                                                           microprocessor in the net electronics capsule (Fig. 5). Bell
                                                                                           212 protocol is used at 1200 baud data rate. Customized
                                                                                           couplers and drivers are used at each end of the cable.

                                                                                                                    5.0 SUMMARY

                                                                                           The capabilities of the 100 percent CMOS 80C88
                                                                                           microprocessor (and related brethren, including the 80C86
                                                                                           and 80C286, etc.) make it possible to provide computing
                                                                                           and data manipulation capabilities for battery-powered, ,
                                                                                                 -alone ocean systems which are comparable to those
                                                                                           stand
                                                                                           available at our desks. The efficient, logical structures of
                   Fig. 4.     Towed package.                                              these Intel engines are nearly irresistible invitations to

                                                                                     653

                               Y777@-_"",
                                                                                               tems. Wiley and Son, Inc., 1982, pp. 208-300.
                                               od,
                                    !Aw
                                                                                         6.    Fredericks, R. G., Wiseman, W. J., and Whelan, Wm.
                                                                                               T. "An Expendable Telemetry Buoy for Coastal
                                                                                               Oceanography." Proceedings, OCEANS '77; Annual
                                                                                               Conf. of Marine Tech. Soc. and IEEE, 1978, pp.
                                                                                               2Cl-2C5.

                             7
                                                                                          7.   Schwing, F. B., Blanton, J. 0. Lamhut, L. and Baker,
                                                                                               C. "Ocean Circulation and Meterology of the Georgia
                                                                                               Coast." Technical Report Series Number 84-1, 1984,
                                                                                               22 pp.

                                                                                          8.   Wibe, P. H., Burt, K. H., Boyd, S. H. and Morton, A.
                                                                                               W. "A Multiple Opening/Closing Net and Environ-
                                                                                               mental Sensing System for Sampling Zooplankton."
                                                                                               Journal of Marine Research, Vol. 34(3), 1976: 313-
                   Fig. 5.    Net power supply and modem.                                      326.

                      assembly language programming, for the few who have
                      submitted to the disciplines and developed the necessary
                      skills. All SKIO application programs described here are
                      written in the assembly language. Interestingly, in each of
                      the systems described, the throughput chokepoint was in
                      the serial communications link and not the CPU.

                                   6.0 ACKNOWLEDGEMENTS

                      Thanks are expressed to Dr. Jack 0. Blanton, Dr. Gustav
                      X. Paffenhofer, Mr. Lee H. Knight, Ms. Dee Peterson, and
                      .4s. Anna Boyette for their suggestions and cooperation in
                      the preparation of this paper. Without their help the
                      preparation of this paper would have been most difficult.

                                         7.0 REFERENCES

                      1.  Abstracts.   Coastal Geography Programs.            1978
                          Annual Contractor's Conference. Office of Naval
                          Research. Arlington, Va. 78 pp.

                      2.  Barrick, D. E. "Theory of Ground Wave Propagation
                          Across a Rough Sea at Dekametric Wavelengths."
                          Battelle Memorial Institute, Columbus Labs. 1970. 93
                          PP.

                      3.  Barrick, D. E. "Increased Propagation Attenuation
                          Over Land." Memo to DARPA (U); U.S. Department
                          of Commerce. NOAA Environmental Research Labs,
                          Boulder, CO, June 1973. 8 pp.

                      4.  Kirwan, Jr., A. D. and Chang, M. S. "Effects of
                          Sampling Rate and Random Position Error on
                          Analysis of Drifter Data."        Journal of Physical
                          Oceanography, 1979, Vol. 9: 382-387.

                      5.  Holmes, J. "Coherent Detection of Coherent Modu-
                          lated Signals." In: Coherent Spread Spectrum Sys-

                                                                                     654

                                                                CIDS - A SHIPBOARD CENTRALIZED DITEGRATED DATA SYSTEM

                                                                                              Richard Findley

                                                                   Rosenstiel School of Marine & Atmospheric Science
                                                                                           University of Miami
                                                                                          Miami, Florida 33149

                                                       ABSTRACT                                               - The system should have flexibility to meet future
                                                                                                                needs.
                     In December of 1986, a microvAX computing system
                     was installed aboard the University of Miami                                             Based on the above objectives, a modular networked
                     Rosenstiel School of Marine and Atmospheric science                                      [ETHERNET) system was selected, using Digital
                     (RSMAS) Research vessel COLUMBUS ISELIN. This paper                                      Equipment Corporation's (DEC) microVAX family of
                     presents several aspects of the installation,                                            computers.
                     including design approach, reliability, personal
                     computer         networking,           file       serving,          personal                                         GETTING STARTED
                     computers as interfaces, instrument interfacing and
                     low cost disk sharing.                                                                   The original system was ordered in early December
                                                                                                              of 1986, and was delivered during the Christmas
                                                                                                              holidays.         Because the operating system software
                                                    BACKGROUND                                                had not yet been delivered, a system was copied
                                                                                                              from an existing VAX on campus; a programmer from
                     Prior to the installation of the present computer                                        URI installed a CTD data acquisition package; and
                     system,       the      computing capability aboard R/V                                   the ship departed for a 90-day CTD cruise on
                     COLUMBUS ISELIN was limited to several HP-85                                             January 2.           During that cruise, one problem was
                     computers      and an IBM AT compatible. Data was being                                  encountered with the hardware, due to a crimped
                     collected         and stored in a variety of formats.                                    wire inside the chassis.                   Since that time, there
                     This resulted in a fragmented data base which                                            have been no other hardware failures at sea.
                     prevented realtime inspection and analysis of data.                                      Subsequent to the original installation, several
                     After using these small computers for several years                                      enhancements have been made, but the general
                     to perform various individual tasks, it became                                           concept remains the same.
                     apparent that a Centralized Integrated Data System
                     (CIDS) was required for logging, processing, and                                                                     SYSTEM WERVIEK
                     analyzing a wide variety of data sources, with
                     realtime display for underway decision making and                                        The system consists of two networked microVAX
                     for post-cruise analysis of surface atmospheric and                                      computers with remote access and shared resources.
                     oceanographic parametersi                                                                A modular approach was the key used to allow for
                                                                                                              reliability, flexibility, and reduced acquisition
                                                DESIGN CRITERIA                                               and maintenance costs. Figure I is a block diagram
                     As a result of the limitations experienced with the                                                                           CPU
                     smaller computers, the following criteria were                                                                             Ram merriory
                     established:
                                                                                                                                                Ram memory
                     - system accessibility provided to the scientists                                                                          Video Driver
                       on board as well as being able to connect their                                                                          Video Rani
                       own computers to the system.                                                                                     Ethernet

                     - Present shipboard electronics technicians could                                                              Buss Extender
                       maintain the system.
                                                                                                                                    Extended Buss
                     - A high degree of hardware reliability which would                                                             SCSI Adapter
                       include the ability to recover from hardware
                       failures with a minimum of expertise.                                                                      Real Time Clock
                                                                                                                                           8 Line Serial Interface
                     - Hardware          and       software         compatability              with                                          9 Track Interface
                       computers at RSMAS so that the existing, in-house                                                                    IEEE-488 Interface
                       knowledge and experience base could be used.                                                                  A/D - D/A
                     - Aquisition costs, as well as continuing hardware
                       and      software        maintenance           costs,        should        be                                            Figure I
                       reasonable.

                                                                             CH2585-a/8e/oooo. 655 $1 @1988 IEEE

                 showing the basic individual computer configuration        - SCSI mass storage devices are considerably less
                 while Figure 2 shows the the overall system.                 expensive than traditional DEC mass storage
                                                                              devices.
                 The computers are powered from an Uninterruptible
                 Power Supply (UPS), which is monitored by the              - A great deal of redundancy and flexibility is
                 computer.  If the ship's power fails the computer            achieved as either computer may access the
                 informs the user of run time remaining on the UPS            devices on the SCSI buss.
                 once per minute, until only ten minutes remain
                 then the computer shuts itself down gracefully.            At this time a Digi-Data 1600-bpi 9-track tape
                 Upon restoration of power, the computer reboots and        drive is connected to one of the microVAX
                 selected software is restarted. The computers and          computers.    Future plans call for the this tape.
                 peripheral mass storage devices are shock-mounted          drive to be connected to the SCSI buss so that'
                 in two fiberglass cabinets having water-resistant          either computer may access the drive directly.
                 covers, which are installed when being loaded or
                 unloaded from the ship.                                    Terminal Servers
                 Computers                                                  Terminal servers are installed on the Bridge, in
                                                                            the main lab, and on the lower deck of the R/V
                 Two computers were installed for redundancy. Each          COLUMBUS ISELIN where the scientist staterooms are
                 is configured in two modular sections, the first as        located.    These servers provide serial RS-232
                 a DEC microVAX 3200 diskless workstation, and the          communication with the computers; each server has
                 second as an expansion chassis also manufactured by        eight serial lines. Terminal servers have several
                 DEC.   This configuration takes advantage of the           advantages over traditional computer-based serial
                 educational discounts being offered by DEC while           interfaces:
                 obtaining the same circuit boards as those used for
                 the standard microVAX.     The workstation section         - Resources, such as printers, plotters and RS-232
                 contains the  CPU, RAM memory, ETHERNET interface,           sensors may be used by either of the computers on
                 video driver, and video RAM. The expansion chassis           the network.
                 which has an  identical power supply and backplane
                 as the first section, contains an 8-line serial            - Terminal servers also allow connection to either
                 interface, a host adapter which connects the                 computer in the event of computer failure.
                 microVAX to   a Small Computer System interface
                 (SCSI) buss, a hardware clock, and other boards as         - A somewhat reduced CPU load as compared to direct
                 required.   The two sections are connected by a              connection to the computer serial ports.
                 ribbon cable and are readily disconnected.
                                                                            - Wiring is simplified; instead of running eight
                 Either computer can be used interchangeably; one is          serial lines to the computer, a single cable is
                 normally used for realtime data collection and               run to each server which is located near the
                 display, the second for data processing and as a             terminals of interest.
                 hot spare for the first.
                                                                            Printers
                 Disk and Tape Drives
                                                                            Two line printers are connected to the main lab
                 Each computer has a SCSI host adapter, which               terminal server,,one ison a print queue the other
                 physically connects the microVAX computer buss             may be allocated for realtime CTD printing.          A
                 CQ-buss) to a SCSI buss, and provides emulation of         laser printer on a print queue is also connected to
                 traditional DEC disk and tape drives.             Both     the main lab terminal server.
                 computers are connected to a common SCSI buss.
                 cable, allowing all the devices. attached to the                             SYSTEM NETWORKING
                 buss to be accessed by either computer.            TWO
                 Control Data Corporation WREN IV 300 MB disk drives        The two system computers, terminal servers and IBM
                 and an Exabyte 8 mm tape drive are attached to the         compatible computers normally installed aboard the
                 SCSI buss.    The disk drives and tape drive are           ship are connected together by ETHERNET. Additional
                 housed in a separate chassis with independent power        computers may be connected using ETHERNET or RS-232
                 supplies for each drive.      The advantages. of the       serial connections. A DEC ETHERNET Local Network
                 SCSI bussed storage peripherals are;                       Interface (DELNI) allows eight connections with
                 - Higher performance                                       another connector allowing additional DELNIs to be
                                                                            daisy-chained. Connection to shore-based computers
                                                                            is'accomplished through INMARSAT at 2400 baud or
                     The tape drive stores 2.2 GB of data with a            through Malabar, Florida, via ATS-III satellite at
                   streaming mode throughput of 189 KB per second           300 baud.
                   as compared to DEC's TK50 tape drive, which
                   stores 95 MB with a throughput of KB per second.         IBM Compatible Networking

                   * The WREN IV disk drive has a capacity of 300 MB        Currently installed on the network is a software
                   with an access time of 16.0 ms as compared to            package from DEC, VAX/VMS Services for DOS.       This
                   DEC's RD54, which has a capacity of 151 MB with          software provides IBM compatible computers Virtual
                   in access time of 38.3 ms.                               Disk Service, File Service, Printer Service, and
                                                                            DECnet-DOS Service from the system computers.
                                                                            Virtual Disk Service provides access to space on a

                                                                       656

                                                               @Dopple,                                                             n
                                                               "or
                                                                                                                                                      EB                                                                 SAE,

                                                                                                                                                                                                                      Dry Bulb Terna
                                                                                                                                          "SINBAD"                                                                    Wet Bulb TgM.
                                                                                                                                                                                                                      Solar Radialion Inst.
                                                                                                                                            CPU                                                                       Solar Radiation Integ.
                                                                User Supplied                                                             Ram memory                                                                  Fluarometer #1
                                                                          PC                                                              Ram memory                                                                  Fluommeter #2
                                                                                                                                          Video Driver                                                                FluoTometer #3
                                                                                                                                          Video Ran                                                                         Depth
                                                               Bridge Terminal                                               Ethernet                                                                                    Depth Sweep
                                                               Server                                                                          I                                                                      Sea Surf. Temp.
                                                               Dry Lab Tenn. #1                                          Buss Exten@;-T                                                                                  Sea Surf. Sal.
                                                               UPS #1                                                                                                                                                    Ship Speed
                                                               UPS #2                                                                                                                                                    Ship Heading
                                                               Dry Lab Term #2                                           Extended Bug                                                                                 Barometric Pressure
                                                               Available                                                  SCSI Adapt                                                                                  Port Wind Speed
                                                               Laser Printer                                           Real Tune Clo                                                                                  Port Wind Direction
                                                                                                                                 8 Line Serial interface                                                              Stbd. Wind Speed
                                                                                                                                                                                                                      Stbd. Wind Direction
                                                                                                                                                                                                                      Electronics Lab Temp.
                                                                                                                                                                                                                      Electronics Lab Hurnid.
                                                               Lab Terminal                                                                                                                                           Hydro Van Temp.
                                                               Server                                                                                                                                                 Hydm Van Humid.
                                                               Loran #1                                                                                                                                                  Winch I.D.
                                                               Loran #2                                                      300 mbyte           300 mbyte                                                            Winch Tension
                                                               GPS Satnav                 Loc k1 Ethernet                    Disk Drive          Disk Drive                                                           XBT Launch ID
                                                               Transit Sathav                I iterface                                          12 &byte
                                                               Omega
                                                    Winch Oper. Terun.                                                                           Tape Drive
                                                               Available                                                                  SCSI Chassis
                                                               Available

                                                    Stateroom Terminal
                                                               Server                                                               n
                                                               Tech Cabm                                                                                                                                                     s.1.
                                                               SE. Cabin                                                                                                                                                   Modem
                                                               Sci. Cabin
                                                                                                                                                                                                                         INMARSAT
                                                                                                                                                                                                                           MO&M
                                                    -96. -Cabin                                                                           "POPEYE"
                                                               Sci. Cabin
                                                               Sci. Cabin                                                                 CPU
                                                    I          Sci. Cabin   _j                                                            Ram memory
                                                                                                                                          Ram memory
                                                                                                                                          Video Driver
                                                                                                                                          Video Rm
                                                                                                                            Ethernet

                                                    D/A                                                                 Buss Extender
                                                    Chi        wiwh C.Ow
                                                    Ch2 -
                                                    AM                                                                  Extended Buss
                                                    Chl - Wimb 7@ndoa                                                                                                                            9 TrWk T04X
                                                    02-                                                                  SCSI Adapter
                                                    03-                                                               Real Time Clock                                                                    Drive
                                                    Cb4-
                                                    W@                                                                          8 Line Serial Interface
                                                    Mr.
                                                                                                                                   9 Track Interface
                                                                                                                                 IEEE-488 interface
                                                                                                                          AID - D/A

                                                                                                FIGURE 2, CIDS BLOCK DIAGRAM
                                                                                                                                          Serial *1.rfw.

                                                                                                                                                 rf.
                                                                                                                                            'I 7nec e
                                                                                                                                               Interface

                                                                                                                                               657

                 micrdVAX disk for use as a DOS-formatted remote                 IBM-compatible can be stored directly on the
                 disk.   Application software can be maintained on               microvAxs. This allows the data to be collected
                 this disk and the IBM compatible computer can boot              continuously by the IBM-compatible computers and to
                 from this disk. Performance from this virtual disk              be backed up on a regular basis using the standard
                 exceeds that of a hard disk connected directly to               back-up facilities on the microvAX. The files may,
                 the IBM-compatible computer. File Service provides              be accessed read only by the microVAX for realtime
                 access to files stored on the microVAX.         This is         data manipulation.
                 similar to the Virtual Disk Service above but is
                 slower. The advantage of File Service is that the                                INSTALLED SOFTWARE
                 fIles are readable by either the microVAX or the
                 IBM-compatible.      Printer Service provides IBM               With microVax    workstations sold to educational
                 printer emulation    on networked DEC pirinters for             institutions DEC includes an Educational Software
                 IBM-compatible computers.          Finally DECnet-DOS           Library (ESL). Although this library contains more
                 provides access to mail, phone, file transfers, and             than 20 software licenses which must be renewed
                 other network utilities.                                        yearly, it still offers significant savings. , The
                                                                                 following ESL software is presently installed on
                 Other Computer Networking                                       the system:

                 Accommodation of other computers not capable of                 -Operating System: VMS
                 using DOS or DECnet, such as Apple, Sun, and
                 Hewlett Packard, etc., may access the system using              -Languages: FORTRAN, BASIC, PASCAL, C
                 public domain software such as Kermit or Xmodem.
                 (DEC has announced , plans to produce Apple-                    -Tools: VAX Language Sensitive Editor, VAX
                 compatible services similar to the VAX/VMS services              Performance and Coverage Analyzer, VAX DEC/CMS
                 for DOS.)                                                        (Code Management System), VAX DEC/MS (Module
                                                                                  Management System), VAX DEC/Shell (Unix overlay),
                              INSTRUMENTATION INTERFACING                         VAX DEC/Test Manager Source Code Analyzer,

                 Once the new system was installed, the       interfacing         Communications: DECnet-VAX, VAX/VMS Services for
                 ?f various shipboard scientific and navigational                 DOS
                 instrumentation was undertaken.       Previously, much
                 of the scientific and navigational data was                      Graphics; VAX GKS (Graphic Kernel System)
                 collected using an HP-85 computer and Serial ASCII
                 Instrumentation LOOP (SAIL) modules designed by                  VAX Information Architecture: VAX DATATRIVE, VAX
                 Oregon State University (OSU). Previous experience               FMS (Forms Management System), VAX Rdb/VMS, VAX
                 with this system had been good but because of baud               Common Data Dictionary
                 rate limitations of the OSU SAIL modules, it was
                 impossible to sample individual sensors at high                  of f ice Tools:    WPS-PLUS/VMS      (Word Processing
                 repetition rates.       Elimination of SAIL serial               System), VAX Notes
                 sensors with long data strings permitted a ten-fold
                 improvement (from 60 seconds to 6 seconds) in the               Additionally, software licenses have been.purchased
                 time required to serially poll every sensor                     for VAX LAB which provide 1/0 routines and dat3a
                 remaining on the loop.        The SAIL system is now            processing and graphics routines.         Sof tware has
                 connected directly to one of the microVAXs, which               been developed in house to control and display data
                 performs all loop control and logging functions.                f rom, the SAIL loop.   CTD data collection software
                 Most serial devices are now interfaced through                  I'las been acquired from the University of Rhode
                 terminal servers.     This allows either computer to            Island and CTD data processing software has been
                 access the sensor, with sampling speed only limited             acquired from NoRDA.
                 by the sensor's ability to output the data. A few
                 serial instruments which are physically located                                     USER INTERFACE
                 nearby are connected directly to the microVAX
                 instead of through terminal servers.         (This is a         The CIDS system is useless unless the scientist on
                 matter of convenience and not due to any special                board has physical access and can learn how to use
                 requirement.)    Analog sensors requiring very high             it.    Scientists are provided with their own
                 sampling rates are interfaced directly to the                   computer accounts.     A computer-based instruction
                 microVAX through an 8-channel A/D board which has a             course is on the system so that they may learn the
                 50-kHz sampling speed.                                          necessary commands to perform the tasks needed to
                                                                                 meet their requirements. A shell is placed on top
                 Interfacing of Instrumentation Controlled by IBM                of the operating system so that users familiar with
                 Compatible Computers                                            UNIX may use familiar commands.       Terminals can be
                                                                                 located in either the labs or cabins,                 and
                 Instruments on board, including the RD Instruments              user-supplied IBM compatible computers can be
                 Doppler Current Profiler, and the LI-COR Spectral               installed temporarily.         This user       interface
                 Radiometer,    have    IBM-compatible    computers     as       provides the scientist with the capability of
                 controllers.     Because it was not desirable or                leaving the ship with a 9-track tape written in
                 practical to rewrite the software to interface                  VAX/VMS format or other industry standard formats.
                 these instruments directly to the microVAX system,              Data can be transferred to DOS 5-1/4" floppies of
                 the IBM-compatible is used as an interface. Using               varying densities or scientists may connect their
                 vAx/vMS services for DOS virtual Disk Service and               own computers to the system and transfer data using
                 File    Service,    data   being    collected    by    an       VAX/VMS Services for DOS or public domain software.

                                                                           658

                        ACQUISITION AND MAINTENANCE COSTS                                           ACKNOWLEDGMENTS
              Figure 3 shows the cost to duplicate the system and              I would like to thank the National Science
              the annual hardware and software maintainance                    Foundation and, in particular, Larry Clark of the
              costs.                                                           office of oceanographic Facilities Support for
                                                                               providing the funding for this system.            I would
                                                       Acquis.    Yearly       like to thank Otis Brown, Robert Evans, Jim Brown,
                                                                               and Angel Li of the RSMAS Remote Sensing Group, and
                                                        Cost      Maint.       Hank Poor and Grant Basham of the RSMAS Computing
              MicroVAX 3200 Workstation                                        Center for their patience and assistance in this
                                                                               undertaking.     Finally, I thank Bill Hahn and his
                (Diskless) (2)                         $27,000    $4,800       technician group at URI for their expertise, which
              Expansion Chassis (2)                      5,000        260      aided greatly in the design of this system.
              9-Track Tape Drive/Interface               6,000      1,164
              8-Line Serial Interface (2)                2,500        260                              REFERENCE
              SCSI Host Adapter (2)                      3,200        360
              WREN IV Disk Drives (2)                    4,800        720       IEEE Standards Board, "IEEE Standard Serial ASCII
              Exabyte Tape Drive                         3,200        540       Instrumentation      Loop     SAIL    Shipboard       DATA
              SCSI Peripheral Chassis                    1,200        120       Communication" ANSI/IEEE Std 997-1985, 1985, l2pp.
              Line Printers (2)                          .2,600       600
              Laser Printer                              3,600        600
              Terminal Servers (3)                       9,600        828
              DELNI                                      1,100          96
              miscellaneous cables                       1,500  .       -
              Educational Software    Library               -       1,000
              Additional Software                        1,500        450
              Documentation Service                        -          900

                TOTAL                                  $72,800    $12,698

                    one-year warranty on hardware, maintenance
                    not required first year.

                                       Figure 3

                                       SUMMARY

              After almost two years of operation, with virtually
              no incidences of failure, reliability has exceeded
              expectations.     The modular approach to the system
              has allowed an upgrade from a MicroVAX If to a
              MicroVAX III with no additional capital outlay.
              Intra-institute      sharing     of     inhouse-developed
              software for this system, and a similar system on
              board R/V ENDEAVOR has made it possibleto make the
              best    use    of    limited    funds     available     for
              programming.      In short, scientists and system
              operators are pleased with the system.

                                                                         659

                                           Validation of Computer Model Predictions of the Large-Scale
                                              Transient Dynamic Towing Response of Flexible Cables

                                                                   John D. Babb

                                             Naval Underwater Systems Center, Newport, RI U2841-5U47

                                        ABSTRACT

                    The large-scale transient dynamic response of            tow point and intermediate locations, was measured
                 cables is being investigated by the U. S. Navy              using commercial and custom-designed submersible
                 using several large computer models.     Dynamic            strain-gaged transducers.   Experimental measure-
                 position and tension data gathered during recent            ment uncertainties were determined to be + 1.4
                 full-scale instrumented towing tests are compared           meters for transient dynamic position dat7a and +
                 to analytical predictions for the purpose of                U.5 meters during less dynamic steady-state tovii-ng
                 validation. Comparisons of predicted and experi-            conditions. Tension measurement uncertainties are
                 mental data indicate acceptable validation, with            + 45 N pounds for tow point tension and + 1b N for
                 the exception of slack end effects at the free-             fransducers located within the cable.
                 end. Results are presented for two computer
                 models and two large-scale transient conditions.                   DESCRIPTION OF PHYSICAL CONFIGURATION
                 Analytical shortfalls and future areas of
                 investigation are discussed.                                    The physical validation experiment was estab-
                                                                             lished using a weighted cable framework attached
                                     INTRODUCTION                            to the Systems Measurement Platform (SMP) barge at
                                                                             Seneca Lake (figures I and 3 ). The instrumented
                    The dynamics of flexible cables have been of             cable was hung in a catenary shape from two elec-
                 interest to aeronautical and ocean engineers pri-           tric releases near the middle of the H-shaped
                 marily from the standpoint of steady-state or               channel. Power and signal transmission was
                 small-disturbance towing problems. However, the             accomplished by connecting the instrumented cable
                 large-scale transient dynamic response of cables            to the tow vessel by a 94.5 meter Kevlar-
                 is of interest to several U. S. Navy problems               -reinforced electromechanical cable.
                 concerned with array mooring deployment, under-
                 water buoy release, and underway deployment of                  The instrumented cable was constrained by de-
                 tethered vehicles. Several analytical models                sign to approximate the position of an operational
                 exist which are capable of predicting the tran-             system which had been deployed (payed out) from a
                 sient dynamic cable response; however, experi-              submarine and was ready for separation (breakaway)
                 mental data for validation and verification                 and subsequent towing. The upper end of the in-
                 purposes has typically been limited to laboratory           strumented cable and the electromechanical cable
                 measurements of shortened cable systems.                    were located at a depth of 15 meters. The lower
                                                                             end of the instrumented cable (breakaway or
                    Transient dynamic position and tension data              free-end) was positioned at 30 meters depth and
                 was acquired during full-scale instrumented                 approximately 49 meters forward. In reality, the
                 towing tests at the NUSC Seneca Lake Acoustic               cable configuration came to equilibrium at slight-
                 Test Facility, Dresden, NY (references I and 2).            ly lower depths and horizontal separation distance
                 The objective of the 1986 experiment was to                 between each end (figure 4). In addition, some
                 measure the dynamic position and tension response           repositioning in the Y-direction (out of the
                 of an instrumented flexible cable during trans-             vertical X-Z plane) occurred as a result of
                 ient towing. The initial cable configuration                unequal cable lengths and weights.
                 (figure 1) was designed to approximate the
                 position and behavior of an operational U.S. Navy               The scenario for the tow tests was for the tow
                 system which is deployed and towed from a                   vessel to commence its run from the center of the
                 submarine (figure 2).                                       south notch of the SMP (figure 3). The tow vessel
                                                                             would accelerate, within 5 seconds, to the desired
                    Transient dynamic position data was acquired             speed, towing in a southerly direction. Prior to
                 with acoustic tracking techniques using custom-             the electro-mechanical cable pulling taut, the
                 designed hardware. Cable tension history, at the            instrumented configuration would be

                                                                       660 United States Government work not protected by copyright

            released from the rigging and the cable system                steady-state validation but must be processed
            would be pulled, upper end over the lower end,                first. Attempts to process a 5 meter/second
            through the transient course.    Following com-               transien/steady-state tow run were limited as a
            pletion of the transient phase of the tow run,                result of monetary and technical difficulties.     It
            the tow vessel would make a large radius turn and             is anticipated that the need for validation data
            proceed through the steady-state tow course.      In          at tow speeds greater than 3.40 meters/second will
            this manner, it was believed possible to acquire              be sufficient to generate additional funding.
            good quality dynamic position data during both
            transient and steady-state tow conditions.                        Each acoustic configuration was instrumented
                                                                          with a tow point tension cell at the tow vessel
                Three instrumented cable configurations   were            and at the head end of the instrumented cable.
            employed during the validation experiment (two                The primary configuration additionally had a
            for acoustic measured position and one for                    pressure transducer attached at the head end for
            tension measurements).    Tables 1, 2, and 3 list             depth indication.   Problems related to signal
            the physical parameters of the tow configura-                 cross-talk between the acoustic and tension in-
            tions.   The parameters are based on physical mea-            strumentation resulted in an inability to acquire
            surements of the tow configurations and are suit-             simultaneous dynamic position and tension data.
            able for use during computer model predictions.               However, a third tow configuration was instru-
                                                                          mented with tension load cells at the tow point
                          EXPERIMENTAL TEST DATA                          and first, fourth and sixth pinger positions for
                                                                          measurement of tow-induced tension at those loca-
                Fifteen instrumented tow tests were conducted             tions. This configuration was similar in hydro-
            during the 1986 experiment.    The primary acoustic           dynamic shape and construction as the primary
            configuration was employed for only one combined              acoustic configuration.   Figures 14 and 15 present
            transient/steady-state tow run before it experi-              the processed tension data for two 2.6
            enced electrical failure as a result of over-                 meter/second transient tow tests. The timing of
            straining the electrical connections. The                     cable relsease and tow speed variations are
            acoustic position data was subsequently processed             similar to those in Table 4. No data was measured
            (figures 5 through 8) with indication that only               for the free-end (sixth pinger) position as a
            the upper three pingers were operational during               result of failure of the transducer wiring.
            the tow run. Transient results presented in the
            figures show that the tow vessel remained on a                           COMPUTER MODEL PREDICTIONS
            straight course, per test plan. Table 4 presents
            a summary of the tow run (TA-1). Steady-state                     The transient dynamic behavior of the U.S.
            tow data consisting of approximately 10 seconds               Navy operational system is being modeled using two
            (20 contiguous data points) were processed. The               large, 3-dimensional, straight segment cable
            experimental data indicated a steady-state tow                models which were originally developed to solve
            speed of 3.48 meters/second and a critical tow                other marine and U. S. Navy problems. The Naval
            angle of 15.09 degrees in the vertical (X-Z)                  Civil Engineering Laboratory (NCEL) SEADYN code
            plane.                                                        (reference 3) is a 20,000 line finite element code
                                                                          which was originally written for ship mooring
                The back-up acoustic configuration was used               applications. The University of Cincinnati
            for six combined transient/steady-state tow runs              UCINCABLE code (reference 4) is a 75UU line rigid
            and four steady-state tow runs. Tow speeds                    body dynamics model which is formulated from
            ranged from 2.6 to 7.7 meters/second. The 3.04                Lagrangian dynamics. This code was developed for
            meter/second (TB-3) tow run data was processed to             mine sweeping applications.
            provide initial data for computer validation
            (figures 9 through 13). Review of figure 13 in-               SEADYN Predictions
            dicated that the tow vessel did not complete      a
            straight tow and therefore created a more                         The SEADYN cable dynamics model is the most
            difficult validation test case than a strictly                capable of the two simulations used for this
            2-dimensional tow. The timing and general                     validation effort. Due to the nature of finite
            description of the motion of the tow vessel is                elements, the model can handle the fixed con-
            presented in Table 5 for use during computer                  straints which are required boundary conditions
            model validation. Acoustic problems related to                when modeling the validation configuration (figure
            inadequate Signal-to-Noise Ratio (SNR) resulted               1) and the moving constraints of the Navy opera-
            in the opportunity to track only the first,                   tional problem (figure 2). The physical
            fourth and sixth acoustic sources in the backup               parameters of Tables 1 and 2 and the run geometr-
            configuration. Attempts to process the steady-                ies of Tables 4 and 5 were used for simulation of
            state tow portion of test TB-3 were reduced to                runs TA-1 and TB-3, respectively. Figures 16
            single data points as a result of the SNR and                 through 22 depict SEADYN predictions of dynamic
            Seneca Lake sound propagation characteristics.                position and tension for test TA-1 (Run #21B).
            This data is not adequate to provide validation               This run required approximately 20.5 days of CPU
            for steady-state tow response.                                on a VAX 11/785 and 17 hours of CPU on a CRAY
                                                                          XMP-28.
                Additional back-up acoustic   configuration tow
            data is available for further transient and

                                                                    664

                 Figures 23 through 29 depict SEAUYN predictions              configuration closer than the UCINCABLE run.
                 for test TB-3 at the expense of 25.16 days of CPU            However, the UCINCABLE tension predictions compare
                 on a VAX 11/785.                                             with the tension module instrumented runs TT-1.and
                                                                              TT-2 better than SEADYN results do@ Both SEADYN
                    Comparison of  the SEADYN predictions and the             and UCINCABLE have trouble with the prediction of
                 experimental data for runs TA-1 and TB-3 indicate            free-ended, slack cable response.    It should be
                 that the majority of the dynamic    efforts are ac-          noted that the intermediate tension module data of
                 counted for with the exception of the cable re-              figures 14 and 1b should be treated with caution.
                 sponse at the free-end.   The slack end response             This comment is provided since the head-end and
                 of SEADYN has been addressed in both references    3         intermediate transducers were separated by 3U.5
                 and 5.  The problems with the numerical model are            meters on the 53.8 meter cable.    Tension values
                 due to inadequate discretization of the cable and            should be proportional.
                 the presence of perfectly flexible joints in the
                 numerical model. The physical validation experi-                 Steady-state predictions of SEADYN provide
                 ment configuration contained more opportunity for            better position comparison with the experimental
                 slack cable effects as a result of the reposi-               data than UCINCABLE does.    This continuing agree-
                 tioning depicted in figure 4.                                ment between SEADYN*and the physical experiments
                                                                              in respect to cable orientation, indicates that
                    SEADYN predictions for the   steady-state por-            the SEADYN model is better suited for modeling the
                 tion of test TA-1 (Run #21BSS) consisted of a                U.S. Navy operational system if accuracy is a
                 vertical plane tow angle of 12.51 degrees and a              concern.- The UCINCABLE model is not as accurate
                 tow point tension of 890 N for the 3.48 meter/               but is capable of prediction behavior much quick-
                 second tow run.   These values compare well with             er.  This relationship was previously developed in
                 the experimental data (figure 3U).                           reference 6 for several different problems.
                 UCINCABLE Predictions                                            The tension comparisons of UCINGABLE with the
                                                                              physical experiment and the poor showing of the
                    The UGINCABLE cable dynamics model is capable             SEADYN model provide an interesting comment.
                 of predicting the towing response of cable sys-              Since both models utilize the same hydrodynamic
                 tems in an "open chain" configuration.    This term          drag coefficients the differences in tension
                 implies that no two points on the modeled con-               predictions must be caused by the interaction
                 figuration are constrained and no closed loops of            between material elastic moduli and numerical
                 cable exist. As a result of this problem, SEADYN             stability in the SEADYN model.
                 output at the time of release (9.75 seconds) was
                 employed to generate the initial UCINCABLE input.                The need for additional validation data for
                 A 2-dimensional preprocessor was used for con-               comparison with the two computer models remains a
                 verting SEADYN data for run #21B (TA-1) to                   high priority for future research. The SEADYN
                 UCINCABLE run #32. However, the 3-dimensional                model has been installed on the NUSC CRAY XMP-28
                 tow response of SEADYN run #200 (TB-3) proved to             and selected for optimization as a sample test
                 be a difficult conversion due to the use of                  case. The UCINCABLE code will be installed in
                 dextral angle relationships for the UCINCABLE                order to take advantage of the available turn
                 input file. A suitable input file has yet to      be         around times between runs and to allow additional
                 generated.                                                   comparisons with SEADYN. NUSC efforts continue to
                                                                              develop and validate computer models which can
                    The UCINGABLE predictions for run TA-1 (run               provide quick, accurate predictions although the
                 #32) are presented in figures,31 through.37. This            primary focus at this time is modeling of the
                 run was completed in approximately 38.1 hours on             towed cable response from a maneuvering submarine
                 a VAX 11/785. At this date the UCINCABLE model               at the conclusion of the transient fetch-up.
                 has not been converted for solution on the NUSC
                 CRAY XMP-28. The free-end response of the                    REFERENCES
                 modeled configuration has identical problems as
                 noted in the SEADYN data discussion. The tension             1. J. D. Babb, "Experimental Measurement and
                 response of the UCINCABLE model at 9.75 seconds              Computer Validation of Flex-Hose Large-Scale
                 should be ignored since it is caused by the need             Transient Dynamic Behavior (Interim Report)",
                 to generate an initial configuration and is not              Naval Underwater Systems Center, Newport, RI , TM
                 representative of physical events.                           No. 87-2UU6, 19 February 1987.
                    UCINCABLE predictions of the steady-state                 2. J. D. Babb, "Experimental Measurement of the
                 response of run TA-1 (run #31) indicated that the            Large-Scale Transient Dynamic Towing Response of
                 UCINCABLE model continues to have difficulties               Flexible Cables", ASME 3rd Annual Symposium of
                 with the cable position (figure 3U). UCINCABLE               Current Practice and New Technology in Ucean
                 values of vertical tow angle and tow point ten-              Engineering,       ULU Vol. 13, January 19TT.
                 sion are 15.66 degrees and 560 N respectively.
                                                                              3. R. L. Webster andP. A. Palo, "SEADYN User's
                              DISCUSSION AND CONCLUSIONS                      Manual", Naval Civil Engineering Laboratory, Port
                    Comparison of the experimental, SEADYN and                Hueneme, CA TN No. N-1630, April 1982.
                 UCINCABLE results show that the SEADYN model
                 predicts the position of the instrumented tow
                                                                        662

                   4. J. W. Kamman and R. L. Huston, Users Manual                                 6. J. W. Kamman and R. L. Huston, "Modeling of
                   for a Three-dimensional, Finite Segment Computer                               Submerged Cable Dynamics", University of
                   Code for Submerged and Partially Submerged Cable                               Cincinnati, Department of Mechanical and
                   Systems", University of Cincinnati, Department of                              Industrial Engineering, UNk-UC-MIE-U7U183-16, July
                   Mechanical and Industrial Engineering,                                         1983.
                   ONR-UC-MIE-050183-15, May 1983.

                   5. P. A. Palo, "Comparisons between Small-scale
                   Cable Dynamics Experimental Results and
                   Simulation Using SEADYN and SNAPLG Computer
                   Models", Naval Civil Engineering Laboratory, Port
                   Hueneme, CA. TM No. M-44-79-5, January 1979.

                                                      Table 1. Primary Acoustic Instrumen              ted Tow Configuration
                       ELECTRO-MECHANICAL CABLE:
                                                           LENGTH               94.5 m
                                                          DIAMETER              1.43 cm
                                                UNIT WET WEIGHT                 0.85 NIM
                                        YOUNG'S MODULUS X AREA                  1.437 x 107 N
                                      NORMAL DRAG COEF    1, ICIENT             1.200
                                  TANGENTIAL DRAG COEFFICIENT                   0.0046

                       INSTRUMENTED FLEX-HOSE:
                                                       TOW END TENSION        @PINGER I        PINGER 2       FINGER 3       PINGER 4       PINGER 5        PINGER 6
                                                            MODULE
                       LENGTH FROM TOW END TO
                          INSTRUMENTATION                   1.07 M              1.47   m       10.74 m        23.11 m        32.36 m        44.75 m         54.07 m

                                                 OVERALL LENGTH                 54.07  m
                                            FLEX-HOSE DIAMETER                  1.59   cm
                          INSTRUMENTATION ATTACHMENT LENGTH                     0.46   m
                                     INSTRUMENTATION DIAMETER                   -1.75  cm (average over attachment)
                                                UNIT WET WEIGHT                 3:.26  N/m
                                        YOUNG'S MODULUS x AREA                  1.370 x 10  7  N
                                      NORMAL DRAG COEFFICIENT                   1.389
                                  TANGENTIAL DRAG COEFFICIENT                   0.0259

                                                      Table 2.      Backup Acoustic Instrumented Tow Configuration

                       ELECTRO-MECHANICAL CABLE:
                                                           LENGTH               94.5 m
                                                          DIAMETER              1.43 cm
                                                 UNIT WET WEIGHT                0.85 Nlm
                                        YOUNG'S MODULUS x AREA                  1.437 x 10     N
                                      NORMAL DRAG COEFFICIENT                   1.200
                                  TANGENTIAL DRAG    COEFFICIENT                0.0046

                       INSTRUMENTED FLEX-HOSE:
                                                       TOW END TENSION          FINGER         PINGER 2       PINGEli 3      PINGER 4       PINGER 5        PINGER 6
                                                            MODULE
                       LENGTH FROM TOW END TO
                          INSTRUMENTATION                   1.32 m              2.01   m       10.54 m        22.60 m        31.82 m        44.01 m         53.08 m

                                                 OVERALL LENGTH                 53.54  m
                                            FLEX-HOSE DIAMETER                  1.59   cm
                          INSTRUMENTATION ATTACHMENT LENGTH                     0.61   m
                                     INSTRUMENTATION DIAMETER                   1.90   cm @average over attachment)
                                                UNIT WET WEIGHT                 3.41   N/m
                                        YOUNG'S MODULUS x AREA                  1.370 x 10  7  N
                                      NORMAL DRAG COEFFICIENT                   1.389
                                  TANGENTIAL DRAG COEFFICIENT                   0.0259

                                                          Table 3. Tension       Module Instrumented Tow Configuration
                                          ELECTRO-MECHANICAL CABLE:
                                                                               LENGTH             94.5 m
                                                                            DIAMETER               1.43 cm
                                                                   UNIT WET WEIGHT                 0.85 NIM
                                                           YOUNG'S MODULUS x AREA                  1.437 x 10  7 N
                                                          NORMAL DRAG COEFFICIENT                  1.200
                                                     TANGENTIAL DRAG COEFFICIENT                   0.0046

                                          INSTRUMENTED FLEX-HOSE:
                                                                          TOW END TENSION         INTERMEDIATE TENSION         TAIL END TENSION
                                                                                MODULE                    MODULE                      MODULE
                                          LENGTH FROM TOW END TO
                                              INSTRUMENTATION                   1.37 m                    31.88 m,                    53.38 m

                                                                    OVERALL LENGTH                53.79.m
                                                               FLEX-HOSE DIAMETER                  1.59 cm
                                             INSTRUMENTATION ATTACHMENT LENGTH                     0.61   m
                                                          INSTRUMENTATION DIAMETER                 1.90   cm (average over attachment)
                                                                   UNIT WET WEIGHT                 3.47   N/m
                                                           YOUNG'S MODULUS x AREA                  1.370 x 107 N
                                                          NORMAL DRAG COEFFICIENT                  1.389
                                                     TANGENTIAL DRAG COEFFICIENT                   0.0259

                                                                                         6@63

                                                                  Table 4. Summary of Primary Acoustic Transient Run TA-1
                                                     INITIAL FLEX-HOSE CONFIGURATION:
                                                                                                                     X              Y              z
                                                                            TOW VESSEL TOWPOINT                      51.81 m      0.00 M           0.00 M
                                                                FLEX-HOSE E/M CABLE JUNCTION
                                                                                         (TOW END)                   4.33 m       2.82 m           19.29 m
                                                                        LOWER END OF FLEX-HOSE
                                                                                        (TAIL END)                   42.24 m      1.,29 m          33.94 111

                                                     TOW MEDIUM:                      FRESH    WATER         T       18.33 C

                                                     TOW POINT MOTIONS:

                                                            INITIAL VELOCITY (t       = 0.0    sec.@                 0.00 M/S     0.00 M/S         0.00 M/S
                                                     TOW VESSEL ACCELERATION It       . 0.0    sec.)
                                                           VELOCITY AFTER TOW VESSEL
                                                                 ACCELERATION (t = 5.0         sec.)                 3.41 m/s     0.00 st/s        0.00 M/S
                                                                     VELOCITY AT END OF
                                                             TRANSIENT RUN (t = 80.00          sec.)                 3.41 m/s     0.00 M/S         0.00 M/s
                                                     RELEASE TIMES:
                                                                             RELEASE OF BOTH ENDS                    t= 9.75 sec.

                                                                 Table 5. Summary of Backup Acoustic Transient Run TB-3
                                                     INITIAL FLEX-HbSE CONFIGURATION:
                                                                                                                     X            Y                z
                                                                           TOW VESSEL TOWPOINT                       51.81M       0.00 M           0.00 M
                                                               FLEX-HOSE E/M CABLE JUNCTION
                                                                                        (TOW END)                    4.32m        2.83 m      19.29 m
                                                                       LOWER END OF FLEX-HOSE
                                                                                       (TAIL END)                    42.16m       1.30 m      33.93 m

                                                     TOW MEDIUM:                      FRESH WATER           T        18.33C

                                                     TOW POINT MOTIONS:
                                                                                                                     X            Y
                                                           INITIAL VELOCITY (t - 0.0 sec-)                           0.00 M/S     0.00 M/S         0.00 M/S
                                                 TOW VESSEL ACCELERATION (t = 0.0 sec-)
                                                           VELOCITY AFTER TOW VESSEL
                                                                ACCELERATION (t = 5.0 sec.)                          2.64 m/s     1.52 m/s         0.00 M/S
                                                       GRADUAL CHANGE IN TOW        VESSEL.
                                                                   DIRECTION (t     = 5.0 sec.)
                                                           VELOCITY AFTER TOW       VESSEL
                                                          DIRECTION CHANGE It       = 9.75     sec.)                 3.05 m/s     0.00 M/s         0.00 M/s
                                                       GRADUAL CHANGE IN TOW        VESSEL
                                                                   DIRECTION (t     = 9.75     sec.)
                                                           VELOCITY AFTER TOW       VESSEL
                                                        DIRECTION CHANGE (t = 12.25            sec.)                 3.05 m/s     -0.12 m/s        0.00 M/S
                                                                    VELOCITY AT END OF
                                                            TRANSIENT RUN (t = 80.00           sec.)                 3.05 m/s     -0.12 m/s        0.00 M/S

                                                     RELEASE TIMES:
                                                                            RELEASE OF TOW END               t       9.75 sec.
                                                                           RELEASE OF TAIL END              t        12.25 sec.

                         4      IN                                                                                                @IUNCH

                                UPPER RELEASE
                                    POINT                                                                                                    BREAKAWA
                                             ---- ------------
                               15 m _-1

                                                                  30 m
                                                                                                                     TRANSIENT

                                                 INSTRUMENTED
                                                     FLEX-HOSE  LOWER RELEASE                  T                           STEADY STATE TOW
                                      TOWLINE                        POINT
                     Figure 1. Transient and Steady-State Towing Range
                                                        ENTED
                                                        .S
                                       @IN
                                                     T' M
                                                     FL. H @E                                                                           OW'
                                                                                                                                            @E     H. @E
                                                                                                                        GUIDANCE WIRE
                                                     Profile
                                                                                                     Figure 2. U.S. NavyApplication Addressed.by the
                                                                                                                              Validation Experiment

                                                                                                 664

                                                                                                                                                       R
                                                                                                                                                       E
                                                                                                                                                       L        0
                                                                                                                                                       A                        ------ ------
                                                                                                                                                       T     15
                                                                                                                                                       1     30
                                                                                                                                                       V
                                                                                                                                                       E     45
                                                                                                                                                       D     60
                                                                                                                                                       1     75
                                                                                                                                                       S
                                                                                                                                                       P     90
                                                                                                                                                       L    105
                                                                                                                                                       A
                                                                                                                                                       C    120
                                                                                                                                                       E
                                                                                                                                                       M    135
                                                                                                                                                       E    150
                                              *,,ft                                                                                                    N    165                 INTERMEDIATE (#3) PINGER                X COORO
                                                                                                                                                                       -----    INTERMEDIATE (#3) PINGER. Y COORD
                                                                                                                                                            180                 INTERMEDIATE           (#3) PINGER      Z COORD
                                                                                                                                                       M                        I    I                 Ir TI    T     I       I  I     I    I     f
                                                                                                                                                                    0      4    8    12 16 20          24 28 32 36        40 44 48 52 56 60

                                                                                                                                                                                                       RELATIVE TIME    SEC.
                              Figure          3. Transient and Steady-State Towing Range                                                         Figure 7.                 Run       #TA-1             Intermediate (43).Pinger 1-D
                                              0                                 Overhead                                                               V        0                                      Track
                                                                                                                                                       E    7.5
                                              7.5                                                                                                      R
                                                                                                                                                       T     is
                                                                                                           E/M CABLE                                   1  22.5
                                              15                                                                                                       C
                                   D                                                                                                                   A     30
                                   E22.5                                                                                                               L  37.3
                                   P                                                       D                                                                 45
                                                                      INSTRUMENTE
                                                                                                                                                       0
                                   T                                            CABLE                                                                  1  52.5
                                   H          30                                                                                                       S     60
                                   37.5                        (DEFORMED)                                                                              T  67.5
                                   M                                                                                                                   A
                                                                                                                                                       N     75
                                              45                                                                                                       C  82.5
                                                                                           E/M CABLE (DEFORMED)                                        E
                                   .52.5                  SEAD83 RUN #21                   INITIAL CONFIGURATION W/OjRI2GING                                 90                 PINGER X1              4.75 TO 43.75 SEC.
                                                          SEAD83      RUN #21              LIVE CONFIGURATION W/ RIG             I N                      97, 5                 PINGER X2              4.75 TO 41.75 SEC.
                                              60                                                                                                       M    i05                 PINGER X3-             4.75 TO 34.25 SEC.
                                                               I      I                    I  I        I        I      I       I                                                     I                 Ir    r       I        I        I              Y
                                              0     7:5        15     22.5      30         37.5 45     52.5   60    67.5      75                                    0      15        30                45 60 75     90        105   120     135      150

                                                                      HORIZONTAL DISTANCE M.                                                                                                           HORIZONTAL DISTANCE M
                                   Figure        4. Representation of Initial Configuration                                                            Figure       8. 2-D (X-Z Plane) Track of Run #TA-1
                                                                                                                                                       R
                                   R                                            of Pigging                                                             E
                                   E
                                   L          0                                                                                                        L        0                                                                        ----------
                                   A                .. .........      ........  .......                                                                A               -----------------------------------------------        *---------
                                   T          15                                                                                                       T     15                                                           ----------------
                                   1          30                                                                                                       1     30
                                   V                                                                                                                   V
                                   E          45                                                                                                       E     45
                                   0'         60                                                                                                       0     60
                                                                                                                                                       1     75
                                              75                                                                                                       S
                                   S                                                                                                                   P     90
                                   P          90
                                   L                                                                                                                   L    105
                                   A          105                                                                                                      A
                                   C          120                                                                                                      C    120
                                   E                                                                                                                   E    135
                                   M          135                                                                                                      M
                                                                                                                                                       E    150
                                   E          150                                                                                                      N
                                   N                                                                                                                                                 0 END (#I) PINGER X COORD
                                   T          165         HEAD END    (#I)      PINGER     x coaRO                                                     T    165                 HEA
                                                          HEAD ENO    (#I)      PINGER     Y COORD                                                                              HEAD ENO (#I)          PINGER     Y COORD
                                                                                                                                                            180                 HEAD ENO (#I)          PINGrER JZ COORD
                                              180         HEAD END              1) PINGER  Z ICOORD                                                                                                    rI
                                   M                      r    I      I(#r      I          II          I   I    I     .    T-__@                       M                        I    I                 I
                                              0     4     8    12 16            20 24 28 32 36 40          44 48 52 56 60                                           0      4    8    12 16 20          24 28 32 36 40 44 48 52 56 60
                                                                                RELATIVE TIME SEC.                                                                                                     RELATIVE TIME SEC
                                              Figure 5.               Run #TA-1 Head-End                   (#l) Pinger J-D                             R  Figure           9.. Run #TB-3 Head-End (#l) Pinger
                                   R                                            Track                                                                  E                                               1-D Track
                                   E                                                                                                                   L        0                                           .......   ........   .......... .......
                                   1.         0                                                                                                        A
                                   A                .....                                                                                              T     15     . ............
                                   T          15                                                                                                       1     30
                                   1          30                                                                                                       V
                                   V                                                                                                                   E     45
                                   E          45
                                   D          60                                                                                                       0     60
                                                                                                                                                       1     75
                                   1          75                                                                                                       S
                                   S                                                                                                                   P     90
                                   P          90                                                                                                       L    105
                                   L          105                                                                                                      A
                                   A                                                                                                                   C    120
                                   C          120                                                                                                      E
                                   E                                                                                                                   M    135
                                   M          135                                                                                                      E    150
                                   E          150                                                                                                      N               - INTERMEDIATE (#4) PINGER X COORD
                                   N                      INTERMEDIATE (#2                 PI                                                          T    165     -  ___.
                                   T          165                                          )MNGERR     X COORD                                                                  INTERMEDIATE (#4) PINGER                Y COORD
                                                          -@INSTRENTFD
                                                                                UM
                                                                                CABLE

                                                          INTERMEDIATE (#2) PI GE                      Y COORD                                              180                 IrNTERM'DIATE          #4),PINGER, Z COORD
                                                                                                       COORO                                                                         T -               T. (I    T
                                              180         INTEMEYATFE (.#2),PINGER,                    @ r.                                            M
                                   M                      r    T                T          T               T                                                        0      4    8    12 16 20 24 28 32 36 40 44 48 52 56 60
                                              0     4     0 12 16 20 24 28 32 36                       40  44   48 52 56 60
                                                                                RELATIVE TIME SEC.                                                                                                     RELATIVE TIME SEC
                                   Figure     6. Run 4TA-1 Intermediate (#2),Pinger                                            I-D                  Figure          10. Run          *TB-3 Intermediate (#4) Pinger 1-D
                                                                                Track                                                                                                                  Track

                                                                                                                                        665

                               R
                               E
                               L     0        .......................     .............................................
                               A                                                                                                                                          1300
                               T     15                                                                                                                                   1200
                               1     30                                                                      .........                                                    1100                  8900 N CAPACITY LOAD CELL
                               V                                                                                                                                                       -----    TENSION MODULE (HEAD END)
                               E     45                                                                                                                                   1000                  TENSION MODULE (INTERMEDIATE)
                                     60
                               0                                                                                                                  N                       900
                               1     75                                                                                                           S                       goo
                               S                                                                                                                  1                       700
                               P     90                                                                                                           0
                               L     105                                                                                                          N                       600
                               A                                                                                                                                          500
                               C     120
                               E                                                                                                                  N                       400
                               M     135                                                                                                                                  300
                               E     150
                               N                      TAIL END      (#6) PINCER          X COORD                                                                          200
                               T     163      . ..... TAIL END      (#6) PINCER          Y COORD                                                                          100
                                     180              TrAILIEN'     (f.6) PINGER         Z ICOORD                                                                         0
                               H                                    I            _      ,           I   1     1     1    1 -
                                              0       48   12 16          20 24 28 32 36 40            44 48 52 56 60                                                     048 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80

                                                                          RELATIVE TIME SEC                                                                                                       TIME SEC.
                                     Figure           11. Run #TB-3 Tail-End (#6) Pinger 1-D                                                      R                       Figure 15. Tension History Run #TT"2
                                                                            Track                                                                 E
                               V        0                                                                                                         L                       0
                               E     7.5                                                                                                          A
                               R                                                                                                                  T                       15
                               T     15                                                                                                           1                       30                          ----------------
                               1     22.5                                                 ......                                                  V                                    -- -----
                               C
                               A     30                             .... . ... .                                                                  E                       45
                               L     37.5                                                                                                         0                       60
                               0     45                                                                                                           1                       75
                                     52.5
                               I                                                                                                                  P                       90
                               S     60                                                                                                           L                       105
                               T     67.5
                               A                                                                                                                  C                       120
                               N     75                                                                                                           E
                               C     82.5                                                                                                         M                       135
                               E                                                                                                                  E                       150
                                     90                                                                                                           N
                                     97.5             PINCER X1           1.75 TO 58.75 SEC                                                       T                       165 HEAD END (NODE 10) PINCER             X COORD
                                                      PINCER X4           1.75 TO 58.75 SEC                                                                               ..... HEAD END (NODE 10) PINCER Y COORD
                               M     105              PINCER X6           1.75 TO 58.75 SEC                 -                                                             180 HFADIE'D (Nr"Ej1O)jP'TGER             Z COORD
                                                         I                    I      r       T      T     I                                       M                               -1                            -7-1             1      1    1
                                              0       15 30     45        60 75     90 105 120 135 150 165 180                                                            048 12 16 20 24 28 32 36 40 44 48 52 56 60

                                                                    HORIZONTAL DISTANCE M                                                                                               RELATIVE TIME SEC.
                                     Figure           12.   2-D (X-Z,Plane) Track of Run #TB-3                                                    A                       Figure 16. SEADYN Prediction of Head-End (#l)
                               T                                                                                                                  E                       Pinger Response during Run #TA-1
                               R        0                                                                                                         L                       0
                               A                                                                                                                                          15
                               N     0.75                                                                                                         T                                                                              ----------
                               S                                                                                                                  1                       30                             --------------
                               V     1.5                                                                                                          V
                               E     2.25                                                                                                         E                       45
                                                                                                                                                                          60
                               R
                               S        3
                               E     3.75                                                                                                                                 75
                                                                                                                                                  S
                               0     4.5                                                                                                          P                       90
                               I                                                                                                                  L                       105
                               S     3.25                                                                                                         A
                               T                                                                                                                  C                       120
                               A                                                                                                                  E                       135
                               N     6.75                                                                                                         M
                               C     7.5                                                                                                          E                       150
                               E                                                                                                                  N                                               OE 13) PINCER             X COORD
                                                      PINCER X1           1.75 TO 58.75r SEC                                                      T                       165 INTERMEDIATE      (NO
                                     8.25                                                                                                                                 ..... INTERMEDIATE    (NODE 13) PINCER            Y,COORD
                                                      PINCER X4           1.75 TO 58.75 SEC                                                                               180 INTEqMEDIATE      (NODE,13@ PINCER            Z COORD
                               M        9             PINCER X6           1.75 TO 58.75 SEC                                                                               r               r     7
                                                         I                           I       I      I     i      I      I                         M                                                                     I   I    1      1    7-1
                                              0       15 30     45        60 75     90 105 120 135 150 165 180                                                            04812 16 20           24 28 32 36 40              44 46 52         56 60
                                                                    HORIZONTAL DISTANCE M                                                                                               RELATIVE TIME SEC.
                                     Figure 13. 2-D (X-Y Plane) Track of Run #TB-3                                                                R                       Figure 17. SEADYN Prediction of                   Intermediate
                                                                                                                                                  E                       (#2) Pinger Response during Run #TA-1
                                                                                                                                                  L                       0
                                     1300                                                                                                         (A
                                                                                                                                                  T                       15
                                     1200                                                                                                         1                       30                             -----------------------
                                     1100                                 8900 N CAPACITY LOAD CELL                                               V
                               T     1000                           ----- TENSION MODULE (HEAD END)                                               E                       45
                               E                                          TENSION MODULE (INTERMEDIATE)                                           D                       60
                               N     900                                                                                                          1                       75
                               S     Boo                                                                                                          S
                               I                                                                                                                  P                       90
                               0     700                                                                                                          L                       105
                               N     600                                                                                                          A
                                     500                                                                                                          C                       120
                                                                                                                                                  E
                               N     400                                                                                                          M                       135
                                     300                                                                                                          E                       150
                                     200
                                                                                                                                                  T                       165 INTERMEDIATE (NODE 17) PINCER                 X COORD
                                     100                                                                                                                                  ----- INTERMEDIATE (NODE 17) PINCER               Y COORD
                                                                                                                                                                          180 IN
                                                                                                                                                                          rTEI@E'I'ATF "OD'1'7@ PINCER                      Z COORD
                                        0                                                                                                         M                                             I                       I   I    1      1    7__@
                                              0       48 12 16 2a 24 28 32 36 40         44 48   52 56 60 64 68 72 76 80                                                  048 12 16 20 24 28 32 36 40                       44 48 52 56 60
                                                                               TIME SEC.                                                                                                RELATIVE TIME SEC.
                                              Figure 14. Tension History Run #TT-1                                                                Figure                  18. SEADYN Prediction of Intermediate
                                                                                                                                                                          03) Pinger Response during Run #TA-1
                                              ,J4

                                                                                                                                       666,

                                     R                                                                                                            R
                                     E                                                                                                            E
                                     L
                                     A                                                                                                            L            0
                                     T15                                                                                                          A                                               ...........................
                                                                                                                                                  T            15
                                     V30                                                                                                          1            30 ------------                    -------
                                                                                                             ------------                         V
                                     E45                                                                                                          E            45
                                     060                                                                                                          0            60
                                     175                                                                                                          1            75
                                     S                                                                                                            S
                                     P90                                                                                                          P            90
                                     L105                                                                                                         L            105
                                     A                                                                                                            A
                                     C120                                                                                                         C            120
                                     E                                                                                                            E
                                     M135                                                                                                         M            135
                                     E150                                                                                                         E            150
                                     N                                                                                                            N
                                     T165           TAIL END (NODE 27) PINGER                       X COORO                                       T            165        HEAD ENO (MODE 10) PINGER                   X COORD
                                                    TAIL ENO (NODE 27) PINGER                       Y COORD                                                               HEAD END (NODE 10) PINGER                   Y COORD
                                     180            TrAILIE'D, (NP'E,27), PINGER                    Z,COORD                                                    180        Mr
                                     M                                                     T_1               T                                                            EAO,EN_0, (NPDE,10),PINGER                  Z COORD
                                                                                                             I    I     I                         H                                                      r            I   I. I         I
                                           0     4  8     12 16 20 24 28 32 36                      40 44    48 52 56 60                                       0          48 12 16 20 24 28 32 36                     40 44 48 5 2 56 60
                                                                    RELATIVE TIME SEC.                                                                                                   RELATIVE TIME SEC.
                                     Figure 19. SEADYN Prediction of Tail-End                                         (#6)                        RFigure                 23. SEADYN Prediction of Head-End 01)
                                                 Pinger Response during Run #TA-1                                                                 E                       Pinger Response during Run #T13-3
                                     V0                                                                                                           L            0
                                                                                                                                                  A                                      ......................................
                                     E7.5                                                                                                                      15
                                     R                                                                                                            T
                                     T15                                                                                                          1            30
                                     122.5                                                                                                        V
                                     C30                                  ... ..                                                                  E            45
                                     A                                                     ------------------
                                     L37.5       - ------- -                                                                                      0            60
                                     45                                                                                                                        75
                                     0                                                                                                            S
                                     152.5                                                                                                        P            90
                                     S60                                                                                                          L            105
                                     T                                                                                                            A
                                     A67.5                                                                                                        C            120
                                     N75                                                                                                          E
                                                                                                                                                  M            135
                                     C82.3       PINGER X1          9.75    TO 72.15 SEC.                                                         E
                                     E90         PlNGER X2          9.75    TO 72.15 SEC.                                                         N            150
                                     97.5        P'INGER X3         9.75    TO 72.15 SEC.                                                         T            165        INTERMEDIATE (NODE 21) PINGER                  X COORD
                                     M     --- PINGER X6            9.75    TO 72.15 SEC.                                                                      So .....   INTERMEDIATE (NODE 21) PINGER                  Y COORD
                                     105   -                                                                                                                   I          INTERMEDIATF (MODE, 2'@ PIINGErR.              Z COORDI
                                                 I        I       I       I       I        I        I        I                                    M                       II 1           1   T                           T -1             1    1
                                           0     15     30        45      60   7.5         90       105 120 135         150                                    0          48 12 16 20 24 28 32 36 40                     44 48 52 56 60

                                                                  HORIZ. DISTANCE M.                                                                                                     RELATIVE TIME SEC.
                                     Figure120. SEADYN 2-D                  (X@Z Plane) Representation                                                         Figure 24. SEADYN Prediction,of Interme                                 diate
                                           of Pinger Motions                during Run #TA-1                                                      R                       (#4) Pinger
                                                                                                                                                  E                                      Response during Run #TB-3
                                     0                                                                                                            L
                                                                                                                                                                                         ............................
                                                                                                                                                  A
                                                                                                                                                  T            15
                                                                                                                                                               30
                                                                                                                                                  V                       - -----
                                                                                                                                                  E            45
                                     30
                                     0                                                                                                            0            60
                                     E
                                     P                                                                                                                         75
                                     T45                                                                                                          S
                                     H                                                                                                            P            90
                                     60                                                                                                           L
                                                                    RELEASE POSITION                T        9.75 SEC                             A            105
                                                                    T     .15.00    SEC.                                                          C            L20
                                     75                                                                                                           E
                                                                    T     -20.00    SEC .                                                         M            135
                                                                    T     -25.00    SEC.                                                          E            15D
                                     90                             T     30. DO    SEC.                                                          N
                                                                    T     35.00     SEC.                                                          T            165        TAIL ENO       (NODE 29) PINGER             X COORD
                                                                                                                                                                          --- TAIL END   (NODE 29) PINGER             Y COORD
                                     105                                                                                                                       180        TA
                                                                                                                                                                          rLIENO         (NGOE,29)j PITN.GER          Z COURO
                                                                                                                                                  M                                      Ir                      _T   I    I     I     I
                                           0     15    30         45      60   75          90       105      120 135    150                                    .0         48 12 16       20 24 28 32 36               40 44 48 52 56 60

                                                                  HORIZONTAL DISTANCE M.                                                                                                 RELATIVE TIME SEC.
                                     Figure 21., SEADYN Snapshot,Representation of                                                                Figure       25.        SEADYN         Prediction              of Tail-End (#6)
                                     Instrumented Cable Tow               Response during Run 4TA-1                                               V            Ia         Pinger Response during Run #TB-3
                                     1300                                                                                                         E            7.5
                                     1200
                                                                                                                                                  T            15
                                     1100                                                                                                         1            22.5                                         ------------------------
                                                                                                                                                  C                                                  ---         -------
                                     T1000                                                                                                        A            30
                                     E
                                     900                                                                                                          L            37.5
                                     N
                                     Stsuu                                                                                                        D            45
                                     700                                                                                                                       52.5
                                     0
                                                                                                                                                  S
                                     N600                                                                                                                      60
                                                                                                                                                  T
                                                                                                                                                               67.5
                                     500                                  -- --------------------   ......   ......                               A
                                                                                                                                                  N            75
                                     N400                                                                                                         C            82.5       PINGER X1 9.75          TO 70.05 SEC.
                                     300     iii:T-1                                                                                              E            90         PINGER X4 9.75          TO 70.05 SEC.
                                     200                                    _-'r01fPM N'T           TERS TUW                                                   97.5       PINGER X6 9.75          TO 70.05 SEC.
                                     100                                       .....       HEAD ENO TENSI
                                                                                                                                                  M
                                                                                                                                                               105
                                           T1, il,,:,                                      INTERMEDIATE H                 ION
                                     D                                                                       2NSE TENS
                                                 IT
                                           0 4 8    12 16 20 24 28 32 36       40 44 48 52 56 60             64 68 72 76 80                                    0          15 30          45 60       75       90      105    120       135    150

                                                                          TIME SEC.                                                                                                      HORIZ. DISTANCE M.
                                     Figure 22.     SEADYN Prediction of Cable Tension                                                            Figure 26. SEADYN 2-D (X-Z Plane) Representation
                                                 History during Run #TA-1                                                                                      of Pinger Motions during Run #TB-3

                                                                                                                                    667

                              T
                              R          0                                                                                                     0
                              A
                              N  0.75                                                                                                  R
                              S    1.5                                                                                                 E
                              V                                                                                                        L       7.5
                              E  2.25                                                                                                  A
                              R                                                                                                        T
                              S          3                                                                                             1       15
                                                                                                                                       V                                                          e
                                                                             ---------------
                              E  3. 75                                                                                                 E                                                      e,
                              D    4.5
                              I                                           PINGER X1        9.75 TO 70.05 SEC                           D  22.5
                              S  5.25                                     PINGER X4        9.75 TO 70.05 SEC                           E
                              T                                           PINGER X6        9.75 TO 70.05 SEC
                                         6                                                                                             P
                              A                                                                                                        T       30
                              N  6.75                                                                                                  H
                              C    7.5
                              E  8.25                                                                                                  M  37.5               ACOUSTIC TEST TA-1
                                                                                                                                                             UCINCABLE RUN #31
                              M                                                                                                                45            SEAD83 RUN #21BSS
                                                                                                                                                     T       r- I               I         I          I
                                         0      15     30         45  60      75      90   105    120 135        150                                 60      50      40         30       20          10      0       -10

                                                                  HORIZ. DISTANCE M.
                                                                                                                                                                   RELATIVE HORIZ. DISTANCE M.
                              Figure       27. SEADYN 2-D (X-Y Plane) Representation                                                    Figure 30. COMparison.of Stea                           'dy-State Tow Angle
                                         Of Pinger Motions during Run #TB-3                                                                                             Predictions

                                                                                                                                       R
                                         0                                                                                             E
                                                                                                                                       L       0
                                                                                                                                       A
                                   15                                                                                                  T       15
                                                                                                                                       I
                                                                                                                                               30
                                                                                                                                       V                                                    -------------------------------
                              0    30                                                                                                  E
                              E                                                                                                                43
                                                                                                                                       D
                              P    45
                              T                                                                                                        1       60
                                                                                                                                       S                            ---------
                              H                                                                                                        P       75
                                   60                                                                                                  L
                                                                  RELEASE POSITION T              9.75 SEC                             A       90
                                                                  T   - 15.00   SEC.                                                   C
                                   75                             T   - 20.00   SEC.                                                   E       105
                                                                  T     25.00   SEC.                                                   M
                                   90                             T     30.00   SEC.                                                   E       120
                                                                  T     35.00   SEC.                                                   N
                                                                                                                                       T       135           HEAD END (NODE 9) PINGER            X COORO
                                 105                                                                                                           150   .....   HEAD END (NODE 9) PINGER            Z COORD
                                         0     15     30          45  610                                                              M                i    I   I    I    I    I    I    I    I     I     I  I    I.   I,1
                                                                             75     90     105   120     135     150                                 0  4    8  12 16 20 24 28 32 36 40 44                   48 52 56 60

                                                                  HORIZONTAL DISTANCE M.                                                                                  RELATIVE TIME SEC.
                              Figure       28. SEADYN Snapshot Representation                                 of                       Figure        31.. UCINCABLE Prediction of Head-End
                              Instrumented Cable Tow Response during Run                                      M-3                                    (#l) Pinger Response during Run 4TA-1

                                                                                                                                       R
                                                                                                                                       E
                                                                                                                                       L       0
                               1300                                                                                                    A
                               1200                                                                                                    1
                               1100                                                                                                    V       30
                                                                                                                                       T       15

                              T1000                                                                                                            45
                              E  900                                                                                                   D
                              N                                                                                                        1       60
                              5  800                                                                                                   S
                              1  700                                                                                                   P       75
                              0                                                                                                        L
                              N  600                                                                                                   A       90
                                 500                                                                                                   C
                              N  400                                    --------------                                                 E       105
                                                                  C41                                                                  M       120
                                 300                                                                                                   E
                                 200                                                                                                           135           INTERMEDIATE (NODE 12) PINGER                 x C.OR.
                                 100                                  'j___:-_--_-__T_d_WPOINT TENSION                                 T             ... INTERMEDIATE (NODE 12) PINGER Z                   COO.,
                                                                            ..... HEAD END TENSION                                             150
                                         0                                 -i-,I'TTERrM "A@TE HOSE TENSAON
                                                            _j                             ET       I . @      I I                     M
                                         0 4 8     12 16  20 24   28 32 36 40 44 48 52 56 60 64 68 72 76 80                                          0  4    8  12 16 20 24 28 32 36 40 44                  48 52 56 60
                                                                        TIME SEC.                                                                                         RELATIVE TIME SEC.
                              Figure 29. SEADYN Prediction of Cable Tension                                                            Figure        32. UCINCABLE Prediction of                           Intermea-
                                                History during Run #TB-3                                                                       iate (#2) Pinger Response during                            Run #TA-1

                                                                                                                           668

                                 R
                                 E
                                 L             0                                                                                                             0
                                 A
                                 T             15
                                 I                                                                   ............                                         15
                                 V
                                               30
                                 E
                                               45                                                                                                         30
                                 D                                                                                                                  E
                                 1             60
                                                                                                                                                    P     45
                                 S                                                                                                                  T
                                 P             75
                                 L                                                                                                                        60
                                 A             90                                                                                                                                            RELEASE POSITION            T      9.75 SEC
                                 C                                                                                                                  M                                                     0
                                 E             105                                                                                                                                           1  - 15. 0     SEC.
                                 M                                                                                                                        75                                 T  - 20.00     SEC.
                                 E             120                                                                                                                                           1    25.00     SEC.
                                                                                                                                                          90                                 T    30.00     SEC.
                                 N             135      INTERMEDIATE (NODE 16) PINGER                     X CO                                                                               1    35.00     SEC.
                                 I                                                                             ORD
                                               150      INTERMEDIATE (NODE 16) PINGER                     Z COORD                                       105
                                 M                      I    I      I - I     I    I --F-- I         I    I   I                                                                                           I       I      I       I       I       I
                                               0  4     8  12 16 20 24 28 32 36 40 44 48 52                             56 60                                  0       15      30       45      60        75    90     105     120     135     150

                                                                      RELATIVE TIME SEC.                                                                                               HORIZONTAL DISTANCE M.
                                 Figure        33.      UCINCABLE Prediction of intermed-                                                              Figure 36. UCINCABLE Snapshot Representation
                                   iate        (#3)     Pinger Response during Run                              #TA-1                            of    Instrumented Tow Cable Response during Run #TA-1

                                 R
                                 E
                                 L             0                                                                                                       1300
                                 A
                                 T             15                                                                                                      1200
                                 1                                                                                                                     1100
                                 V             30
                                 E                                                                                                                  T  1000
                                               45                                                                                                   E   900
                                 0                                                                                                                  N
                                 1             60                                                                                                   S   Boo
                                 S                                                                                                                  1   700
                                 P             75                                                                                                   0
                                 L                                                                                                                  N   600
                                 A             90                                                                                                       500
                                 C             105                                                                                                  N   400
                                 E                                                                                                                                                                                        ......
                                 M                                                                                                                      300
                                 E             120
                                 N                                                                                                                      200                                     ........  7.--,.J.QWPQJNT TENSION
                                 T             135      TAIL END (NODE 26) PINGER X COORD                                                               100                                               ----- HEAd CWb-f0W@Y66F        --------
                                               .....    TAIL END (NODE 26) PINGER Z COORD
                                               1
                                               0                                                                                                             0                                                INTERMEDIATE HOSE TENS:ON
                                               51
                                               0  4     8  12 IIS 20 24 28 32 36 40 44                       48 52 56 60                                        0   4 8 12 16 20 24          28 32 36 40 44 48 52 56 60 64 68 72 76 80

                                                                      RELATIVE TIME SEC.                                                                                                          TIME SEC.

                                 Figure        34.      UCINCABLE Prediction of intermed-                                                           Figure        37. UCINCABLE Prediction of Cable Tension
                                   iate (#6)            Pinger Response during Run #TA-1                                                                          History during                  Pun #TA-1

                                 E 7.5
                                 R
                                 T             15
                                 22.5
                                 A             30
                                 L37.5                           41-
                                 D             45
                                 152.5
                                 S             60
                                 T
                                 A67.5
                                 N             75
                                 C82.5                  PINGER XI     9.75    TO 79.70 SEC.
                                 E
                                               90 ----- PINGER X2     9.75    TO 79.70 SEC.
                                 97.5                   PINGER X3     9.75    TO 79.70 SEC.
                                 M 105                  P NGER X6     9.75    TO 79.70 SEC.
                                                          r         I         I    I       I
                                               0  15     30         45     60     75      90      105     120    135      150

                                                                    HORIZ. DISTANCE M.
                       Figure 35. UCINCABLE 2-D (X-Z Plane) Representation
                                               of Pinger Motions during Run.#TA-1

                                                                                                                                      669

                                               SURFACE TET        TR ENGINEERING MOORING (STEK)*

                                                      Henri 0. Berteaux, Daniel E. Frye,
                                                      Peter R. Clay, Edward C. Mellinger

                                                    Woods Hole Oceanographic Institution
                                        ABSTRACT                                 which would maintain the buoy on station
                                                                                 and would also provide a reliable signal
                 A Surface T61emetery Engineering Mooring                        path between the deep sensors and the
                 (STEM) has been developed to collect and                        surface. The mechanical,and electrical
                                                                                 problems of properly connecting these
                 transmit oceanographic and meteorological                       cables at the buoy attachment point and at
                 data via satellite links. Data                                  the points of instrument insertion in the
                 telemetered included currents (from 50 and                      mooring line also had to be surmounted.
                 250 meters), water and air temperature,
                 wind, relative humidity, barometric                             The successful completion of the STEM
                 pressure, and various engineering                               project also depended on advanced buoy
                 parameters                                                      engineering for classical mooring design
                                                                                 and on specialized mooring logistics for
                 The unique     aspect of the STEM design was                    deployment, servicing and recovery.
                 the use of     electromechanical cable for
                 both the strength member of the mooring                                         2.0 RETROSPECTIVE
                 and the electrical connection between the
                 subsurface instruments and the surface                          The R/V ENDEAVOR, operated by the
                 buoy.                                                           University of Rhode Island, deployed the
                 The surface mooring was deployed 150 miles                      STE 'M mooring on November 21, 1987 at
                 south of Cape Cod in 2700 meters of                             39 011N Latitude and 70       0OOW Longitude.
                 water setout in November 1987 and                               This location is near the well-known
                 retrieved in May 1988, it operated                              Site D, 150 miles due south of Cape Cod
                 successfully through the harsh                                  (Figure 1). The water depth at the site
                 N. Atlantic winter.                                             is 2672 -meters. The mooring configuration
                                                                                 is depicted in Figure 2.

                                  1.0 OBJECTIVES
                                                                                  780 W                   700                      620
                 The purpose of the Surface Telemetry                         460-                         1                   NOVA
                 Engineering Mooring (STEM) was to                              N                                              SCOTIA
                 demonstrate the feasibility of collecting
                 and transmitting data via satellite                                                                 A.
                 telemetry. STEM is designed to handle an
                 extensive suite of meteorological,                                               PORTLAND
                 oceanographic and engineering data
                 obtained from sensors distributed on the                                         BOSTON          >
                 surface buoy and on the mooring line.                The                                                         1000_@
                 surface mooring was to be deployed well                                                                          '@00
                 off-shore in deep waters and had to                                 NEW YORK
                 survive the harsh environment of the
                                                                                                       Bu     Farm
                 wintry Northwest Atlantic.

                 This ambitious goal required both
                 electrical and mechanical engineering                                                   sit
                 support. The electrical engineering
                 effort placed emphasis on the                               380-
                 modification and integration of existing
                 instruments and sensors with a system
                 controller. This controller ensures the
                 timely and sequential interrogation of the                                                                       /I
                                                                                                                                  7
                 sensors and the subsequent data processing                      CAPE HATTE
                 and transfer to buoy mounted, satellite
                 transmitters. The innovative mechanical
                 engineering contribution consisted mainly                                 Figure I Site D Location
                 of the development and evaluation of
                 electromechanical cables

                                                         CH2sa5_s/88/ooo0_ 670 $1 @1988 IEEE

                                             4/ ARGOS a GOES TRANSMITTERS
                                                    MET SENSOR PACKAGE
                                                    3m DIA. DISCUS BUOY a CENTRAL CONTROLLER

                                                    2m 5/8 chain
                             5 4 m                  50m U19, 1/2"dia. E/M cable
                                                    VMCM (w/ TEMPERATURE) #11
                                                    200m 309, 1/2 dia. E/M cable
                             254m---->
                                            _VMCM (w/ TEMPERATURE) #2
                                                                                                                                                              _W71
                                            -375m U19, 5/ld'dia. wire rope                                                                                       f.
                                                                                                                    wag-

                                            -375m 309, 5/16             dia. wire rope

                                                    400nn 3xI9, 5/16" dia. wire rope
                                                                                                                    lip
                                          11-CONTINUITY METER
                                            _50rn 309, 3/8"dia. E/M cable
                           1457 rn --->
                                          11-ENGINEERING INSTRUMENT                   #1
                                                    100m ftl6l'dia. wire rope
                           1557 m         3.
                                                    500 rn 15/16" dia. nylon rope

                           2000 m ---->
                                                    500M 13/16" dia. nylon rope

                                                    2 GLASS BALLS                                                                          Figure 3 STEM Buoy
                                                    120 rn 3/4" dia. nylon rope  (adjustable)
                                            E
                                                    BACK-UP FLIDTATION (34) 17" GLASS BALLS                         At 00 00 hours on January 1, 1988, a
                                                    zrn 1/2" chain                                                  software error prompted the controller to
                                                    ENGINEERING INSTRUMENT #2                                       collect data at an accelerated rate which
                                                    2m 1/2" chair,                                                  soon jammed the data buffer.                                  On January 7
                                            i--ACOUSTIC RELEASE                                                     the problem resulted in the cessation of
                        BOTTOM                      5m 1/211 chain
                                                    20m P dia. nylon rope                                           all telemetered data.
                        DEPTH                       5m 1/2; chain
                           2672 m                   ANCH@ (6000 Ibs)                                                On February 9,' 1988 a short (2-day) repair
                                                                                                                    cruise was made with the R/V IDA-Z, a
                                      SITE "D" TEST: 39'10.8'N, 70*00. 55'E                                         converted, fishing vessel from New
                                                                                                                    Bedford, MA. The buoy was boarded, the
                                 SURFACE TELEMETRY MOORING (STEM)                                                   software problem was corrected "in situ",
                                                                                                                    the cabling polarity problem was fixed,
                                      NOVEMBER 21, 1987 - MAY 2, 1988                                               and a new wind sensor was installed to
                                                                                                                    replace the original instrument which had
                                          Figure        2 STEM Mooring                                              damaged bearings. The vessel then
                                                                                                                    promptly and safely returned to Woods
                    This six month engineering test mooring                                                         Hole. On February 12 a major storm hit
                    Was equipped with telemetering current                                                          Site D.
                    meters set at 50 and 250 meter nominal
                    depths and a telemetering meteorological                                                        From the time of the repairs to the time
                    station mounted on a standard WHOI                                                              of recovery, done with the help of the R/V
                    3- meter discus buoy (Berteaux, 1976)                                                           OCEANUS on May 2, 1988, data from both
                    (Figure 3). Telemetry to shore was                                                              current meters and most meteorological
                    performed through ARGOS and GOES satellite                                                      sensors were continually received. The
                    links. The telemetry data stream included                                                       quality of these data is further discussed
                    hourly averages of current, water                                                               in a later section of this paper.
                    temperature, wind, air temperature and
                    relative humidity, barometric pressure and                                                                  3.0 MOORING AND CABLE DESIGN
                    buoy heading, as well as a number of
                    engineering housekeeping parameters                                                                     3.1 Electromechanical (E/M) Cables
                    (mooring line tension, cable integrity,
                    battery voltage, water leaks, etc... ).                                                         Numerous specifications for oceanographic
                    Recording engineering instruments were                                                          E/M cables have been published in the
                    also inserted at depths of 1400 and 2540                                                        literature (A. Driscoll, 1982 and P.
                    meters respectively to monitor tension and                                                      Gibson, 1984), yet very few E/M cables
                    tilt in the mooring line. (Clay, 1987)                                                          have been designed and fabricated
                    From the time of deployment to                                                                  specifically for deep sea mooring
                    December 31, 1987 all data channels were                                                        applications. Mechanically these cables
                    transmitted and received via ARGOS as                                                           must provide enough strength to safely
                    programmed, with the notable exception of                                                       maintain the mooring on station. To
                    the upper current meter. The cause of                                                           prevent conductor damage, the cable
                    this transmission failure was later                                                             modulus of elasticity must be high enough
                    identified as a polarity inversion in the                                                       so that the cable exhibits a minimum
                    cabling to the instrument.                                                                      elongation when under tension. The
                             54

                            254

                                                                                                            671

                          armor must resist corrosion and fatigue,                                                        Cables #3 and #4 are of contrahelical
                          and must be torque balanced to reduce the                                                       double armor construction. The armor of
                          danger of kinking. When deployed in the                                                         #3 is made of Galvanized Improved Plow
                          fishbite zone, typically the upper 2000m                                                        Steel (GIPS) whereas the armor of #4 is
                          of the water column, (Berteaux and                                                              made of KEVLAR. These cables are designed
                          Prindle, 1987) it must provide a fair                                                           to be used only on subsurface moorings
                          degree of protection to the conductors                                                          (A. Bocconcelli, 1987).
                          against fishbite attacks.
                                                                                                                          The strength member of cables # 1 and # 2
                          Modern, hard wire telemetry uses low                                                            is the well-known 3 X 19 oceanographic
                          voltage, low power digital signal                                                               rope. Over the years this type of rope
                          transmission. These needs are easily                                                            has been successfully used to anchor
                          accommodated with relatively small gauge                                                        hundreds of deep sea surface and
                          conductors, typically AWG #20 (.812mm) or                                                       subsurface moorings. It seems logical to
                          # 22 (.644mm). Conductor insulation,                                                            retain this rope design to produce an E/M
                          material and thickness must be specified                                                        cable suited for surface mooring
                          to not only satisfy the electrical                                                              applications.
                          requirements but also to ensure perfect
                          and easy bonding at the termination ends                                                        Using the 3 X 19 construction, three
                          as well as maximum conductor protection                                                         conductors can be placed in the center of
                          from mechanical abuse.                                                                          the strands, as shown in cable # 2, or in
                                                                                                                          the valleys between the strands as shown
                          With these requirements in mind, four                                                           in cable # 1. The first approach provides
                          experimental E/M cables have been                                                               excellent mechanical and fishbite
                          developed and fully to partly evaluated.                                                        protection for the conductors. However,
                          These cables, together with some of their                                                       keeping the armor wires from damaging the
                          characteristics, are shown in Figure 4.                                                         conductor insulation during stranding
                                                                                                                          requires heavy insulation walls and great
                                                                                                                          c
                                                                                                                            are.
                                                                                               _X
                                                       V

                                                                                       X
                                                                                       AM
                                                                                           3                  0,

                                                                                                                                                                          (3) STRANDED COPPER
                                                                                           012,                                                                                       IRS (AWG #20)
                                                                                                                                                                          CONDUCTO
                                                                                           0,
                                                                        Xr
                                                                                                  A
                                                                                                                                                                          INSULATION:
                                                                                                                                                                          0.015* WALL PVC
                                                                                                                                                                          0.010* WALL NYLON

                                          'A'     A
                                                                                                                                                                          3/fl" 3x19 TORQUE BALANCED
                                                                                                                                                                          WIRE ROPE (Mc WHITE)

                                                                                                                                                                          INNER JACKET.
                                                                                                                                                                          POLYURETHANE
                                                                                                                                                                          0.054" WALL
                                                                                                                                                                          O.D.     0.500"

                                                                                               -4 505                                                                     STEEL
                                                                                           4
                                                                                                                                                                          O.D.     0.51
                                                                                                                                                                                  TAPE @2 LAYERS)
                                                                                                                                                                                        6

                                                                                                                                                                          OUTER JACKET.
                                                                                                                                                                          HYTREL
                                                                                                                                                                          0.047" WALL
                                                                                                                                                                          O.D. = 0.610"
                                            TION STRENGTH       1b3/1OOO'  OU'131DE CONDUCTORS                um
                                 Fco;;;U@             (Ibe)             - DIL
                             1    3 X 19 GAPS         14,800       360       0.610     (3) #20 AWG CONSOUDA10
                             2    3 X 18 GIPS         14.800       248    1  0.460     3   #22 AWO        VAcWHYX                             Figure 5 STEK Cable Detail
                             3   STEEL ARMOR          10,300       257       0.478     (3) #20 AWC            B11K
                             4 KEVLAR DOUBLE          8,300        94.1      0.475     (3) #20 AWC            ILLW.
                                       LAYER

                          Figure 4 Experimental                         Electromechanical
                                                                 Cables

                                                                                                                     672

           Cable manufacturing is somewhat easier in         ends, the cable assemblies were tensile
           the second approach. However, a fishbite          proof tested and thereafter, subjected to
           resistant barrier must be added to protect        3000 psi of hydrostatic pressure for four
           the conductors now at the periphery of the        hours. The conductors were then checked
           rope structure. The STEM cable, shown in          for continuity and insulation integrity.
           detail in Figure 5 had a standard 3/8 inch        The assemblies were pronounced fit for sea
           3 X 19 strength member (UBS, 14,800 lbs).         duty after successful completion of these
           Three # 20 stranded copper PVC insulated          tests.
           conductors were laid between the strands .
           and held in place with the help of a Mylar        When deployed, the continuity of the two
           tape. Polyurethane was then extruded over'        upper E/M cable assemblies was monitored
           the cable to provide an additional water          by telemetry. The condition of the
           barrier. Finally two layers of stainless          lower assembly was monitored by a
           steel tape were wrapped over the                  recording instrument which periodically
           polyurethane jacketed core and a jacket of        checked the continuity of its 3
           hard Hytrel extruded over the entire              conductors.
           assembly, with a resulting outside
           diameter of 0.610 inch.                           After retrieval the cable assemblies were
                                                             carefully inspected and tested for shorts,
              3.2 Electromechanical Terminations             opens and residual strength. No sign of
                                                             conductor damage or rope deterioration was
           Two 50 meter and one 200 meter E/M cable          found.
           assemblies were deployed in the STEM
           mooring (Figure 2). Each length was               The four types of E/M cable shown in
           terminated at both ends with terminations         Figure 4 are scheduled to undergo an 18-
           designed and built at WHOI. As shown in           month deep sea evaluation, starting
           Figure 6, the terminations are of the             February 1989. This test will be part of
           Clevis type for ease of connection with           the Engineering Surface Oceanographic
           existing instrumentation. The steel body          Mooring (ESOM) program.
           is made of two halves. The tapered half
           contains the wires of the armor, which are
           embedded in an epoxy pour. The Clevis                  4. 0 DATA COLLECTION AND TELEMETRY
           half screws into the tapered half and is
           filled with polyurethane. The three               The STEM system was equipped with
           conductors are then placed in a protective        environmental sensors to monitor ocean
           polyurethane sheath and laid to a junction        currents and temperatures, surface winds,
           splice which connects them to a commercial        air temperature, relative humidity and
           pigtail. This design provides full cable          barometric pressure. Currents were
           strength and a double water barrier.              measured with EG & G Vector Measuring
                                                             Current Meters (VMCMs) at depths of 55 and
                                             ANTIROTATING PIN 257 m.  These instruments recorded data
                              POTTING SOCKET  POLYUR THANE   internally and were equipped with FSK
                                                CLE          (Frequency Shift Keying) modems which
             E/M CABLE                                       allowed two-way communication with the
                                                             controller using two conductors of the
                                                             electromechanical mooring
                                                             cable. Average current and water
                BENDING STRAIN RELIEF_BOOT EPO               temperature values were recorded at 15
                              2                  POLYURETHANE minute intervals and loaded into an output
                              rONDUCTOR CO E FROM CABLE  JACKET buffer. Every 15 minutes, 7.5 minutes
                    BRANTNER PIGTAIL                         after a record cycle, the system
                              3 CONDUCTORS                   @ontroller interrogated each current meter
                  /_                                         individually using the SAIL protocol
                                                             (IEEE, 1985) and collected the most recent
                                      MOLDED SPLICE (POLYURETHANE current component and water temperature
                                                             values. These 15-minute values were then
                                                             scalar averaged to form hourly averages
            Figure 6'Experimental Electromechanical          and loaded into the ARGOS and GOES
                         Cable Termination                   telemetry buffers.

                                                             Meteorological data collection was
                                                             performed by a Coastal Climate Weatherpak
                                                             instrument. This small, self-contained
                           3.3 Testing                       unit was modified for interrogation via
           The 3 X 19 wire rope was made by McWhyte          SAIL protocol in a manner analogous to the
           Inc. The conductors and the E/M cable             current mieters. The Weatherpak uses an RM
           were fabricated by consolidated Products          Young Wind Monitor to measure wind speed
           Inc. Acceptance testing of the E/M cable,         and direction, an Anderaa clamped compass
           performed at WHOI, included strength and          to monitor buoy heading, a Rotronics
           rotation tests, and conductor resistance          relative humidity and air temperature
           measurements. After terminating both              sensor and an AIR barometer.

                                                         673

                Using the Coastal Climate menu-driven             -  Average, minimum and maximum voltage in
                software, the Weatherpak was programmed to           the primary battery (IOV).
                collect 10-minute averages of each of the
                meteorological parameters once each hour.         -  Average, minimum and maximum voltage   in
                It accomplished this by measuring wind               the secondary battery (12V).
                speed and direction every second for 10-
                seconds and then computing a true vector          -  Average, minimum and maximum voltage   in
                wind velocity using a compass reading                the 12 V charging circuit.
                (buoy heading) every 10-seconds to relate
                measured winds to true geographic winds.          -  Average, minimum and maximum current
                Sixty of these 10-second averages were               consumption..
                then used to compute a 10-minute average
                which was forwarded to the system                 -  Controller internal temperature.
                controller on request, once each hour.
                                                                  -  Communication error counts between the
                In addition to the environmental                     system controller and each of the
                measurements, various engineering                    external devices, i.e. the current
                measurements were made on an hourly basis            meters, the Weatherpak, the ARGOS PTT
                and telemetered once or more per day.                and the GOES transmitter.
                Included in these engineering measurements
                were:                                             Each of these parameters was telemetered
                                                                  one or more times each day. Table 1
                -  Average, minimum and maximum mooring           illustrates the data format sent through
                   line tension directly beneath the              the ARGOS data collection system. A
                   surface buoy.                                  similar message containing 6-one hour
                                                                  averages was telemetered via the GOES
                -  Continuity of   the electrical conductors      system.
                   in the mooring cable.

                -  Water presence or absence in the
                   instrument well.

                           Telemetry Message (hourly): 64hex characters (256 bits)

                           HHQNNNNEEEETTTTQNNNNEEEETTTT SSSDDDGGGAAATTTTHHHPPPP MMMMDDDD3CCCC

                                 VMCM1         VMCM2                 WPAK           ENG DATA

                           Telemetered Data                          ExRlanation

                                 HH            GMT hour during which data was acquired.
                                   Q           Number of values included in the hourly average from
                                               vMCM1.
                               NNNN            Averaged value of north component of current from VMCM1.
                               EEEE            Averaged value of each component of current from VMCMI.
                               TTTT            Averaged temperature from VMCM1.
                                   Q           Number of values included in the hourly average from
                                               VMCM2.
                               NNNN            Averaged value of north component of current from VMCM2.
                               EEEE            Averaged value of east component of current from VMCM2.
                               TTTT            Averaged temperature from VMCM2.
                                SSS            Average wind velocity.
                                DDD            Average wind direction.
                                GGG            Maximum 4-second wind gust.
                                AAA            Buoy heading.
                               TTTT            Air temperature.
                                HHH            Relative humidity.
                               PPPP            Barometric pressure.
                               MMMM            Engineering value 1.
                               DDDD            Engineering value 2.
                                   3           Constant
                               CCCC            Checksum.                                                   L

                           Table 1. Format of the telemetered data sent via Argos.

                                                               674

             Telemetry of the data from the surface             power usage and Service ARGOS charges.
            .buoy to shore was accomplished using both          Thus, a total of sixteen     256-bit
             ARGOS and GOES transmitters. These                 messages were transmitted every 8 minutes,
             systems were chosen because they are               each message consisting of hourly averages
             reliable, well,understood, easy to                 of the scientific parameters previously
             implement and inexpensive. They do not             mentioned. The engineering data were
             require the user to maintain a special             reported less frequently (Table 2). A
             receiver station,and they provide coverage         check-sum was used at the end of each
             worldwide (ARGOS). Other telemetry                 message to edit bad transmissions.
             schemes have been evaluated at WHOI under
             this project and may be required in                The GOES telemetry was handled in a
             situations where data throughput                   similar way, but without modification to
             requirements are higher (Briscoe, 1987).           the standard system. A Synergetics 40
             In this prototype experiment both ARGOS            watt GOES transmitter and Master Control
             and GOES systems had more than enough              Module were interfaced to the system
             capacity to handle the required data.              controller. once every third hour the
                                                                GOES buffer was loaded with the most
             In order to send hourly averages from    both      recent 6 hours of averaged data. Its
             current meters, the meteorological package         telemetry schedule called for a 1 minute
             and various engineering data, it was               transmission every 3 hours, so that loot
             necessary to modify the standard                   data redundancy was anticipated.
             Synergetics/FORE ARGOS
             transmitter. This modification,                    In addition to the telemetry discussed
             performed at WHOI, allowed us to     send 16       above, the surface buoy was also equipped
             times more data than is possible    with a-        with a secondary ARGOS transmitter with
             stock transmitter. The modification,               separate antenna and power supply in case
             which is primarily a software revision to          of damage to the primary unit. A Vector
             the manufacturer's control software,               Averaging Wind Recorder (VAWR) was mounted
             provides a data buffer which stores eight          on the surface buoy to collect weather
             . 256-bit messages. Each message in this           information for comparison with the
             buffer is transmitted sequentially at 1            Weatherpak.
             minute intervals and received by the,
             satellite during a typical 10 to 15 minute
             pass. In addition, the transmitter ID is
             changed twice per minute, effectively
             making it the equivalent of two
             transmitters in terms.of data throughput,

                      Transmission Time (GMT)                     Parameters
                                                  Channel                         Channel 2

                             00            Primary Battery(Min.)             VMCM1  Timeouts
                             01            Primary Battery(Max.)             VMCM1  Comm Errors
                             02            Primary Battery(Aver.)            VMCM1  Address Failures
                             03            1@ V Supply(Min.)                 VMCM2  Timeouts
                             04            16 V Supply(Max.)                 VMCM2  Comm Errors
                             05            16 V Supply(Aver.)                VMCM2  Address Failures
                             06            Tension(Min.)                     0006
                             07            Tension(Max.)                     0007
                             08            Tension(Aver.)                    0008
                             09            Cable Continuity(Min.)            0009
                             10            Cable Continuity(Max.)            OOOA
                             11            Cable Continuity(Aver.)           OOOB
                             12            Secondary Battery(Min.)           WPAIK Timeouts
                             13            Secondary Battery(Max.)           WPAK Comm Errors
                             14            Secondary Battery(Aver.)          WPAK Address Failures
                             15            Tension(Min.)                     PTT Timeouts
                             16            Tension(Max.)                     PTT Comm Errors
                             17            Float Switch                      PTT Address Failures
                             18            Snunt Current(Min.)               GOES Timeouts
                             19            Snunt Current(Max.)               GOES Comm Errors
                             20            Snunt Current(Aver.)              GOES Address Failures
                             21            Tension(Min.)                     Controller Resets
                             22            Tension(Max.)                     0016
                             23            Controller Temp.(Aver.)           Tension(Aver.)

                                             Table 2. STEK Engineering Data

                                                           675

                   5.0 CONTROLLER AND POWER SYSTEM               It also controlled the charging of the
                                                                 secondary rechargeable power supply and
             The system controller was designed and              monitored the communication link between
             built at WHOI to accommodate a wide range           the controller and the peripheral devices.
             of control applications requiring
             collection of data from a variety of                In operation the STEM controller performed
             sensors, data processing and recording,             its data collection, processing and 1/0
             and telemetry (Mellinger, et.al, 1986).             operations on an hourly cycle. The
             It is an 8OC86 based machine designed to            current meters were interrogated every 15
             fit in a 6-inch ID pressure case for use            minutes. These data were converted to
             with in situ oceanographic instruments.             engineering units, and averaged hourly and
             It makes use of a back plane derived from           piped to the storage buffer. The
             the IEEE - 796 (Multibus) standard (IEEE,           Weatherpak was interrogated once each
             1983).                                              hour, the data were re formated to
                                                                 eliminate unnecessary information and
                                                                 piped to the storage buffer. The various
                                                                 engineering data (Table 2) were collected
                                                      ANTENNA    hourly, averaged and stored along with the
                                                                 external values in the storage buffer.
                                                                 Every hour the data, were down-loaded to
                      ANTENNA                                    the ARGOS transmitter for telemetry to
                                                          :3     satellite. Every third hour the GOES
                                                                 transmitter buffer was updated.

                                                                 The format of the telemetered data sent
                                         - - - - - - - -         via ARGOS is shown in Table 1.
                                             CABLE TENSION
                    [IVSAILIOC               SHUNT CURRENT       Power for the STEM system was supplied by
                                         - FLOAT SWTCH           a 30V alkaline battery installed in the
                                CONTROLIER - 12V BATTERY         instrument well.   A DC/DC converter in the
                                         -    16V SUPPLY         controller provided 5V to the controller
                                       0
                                       1
                                       < -30V BArTERY            and the various engineering sensors and
                                            CABLE RESISTANCE     12V to charge a secondary lead-acid
                                           INTERNAL TEMPERATURE  battery which consisted of 6 - Gates cells
                                                                 in series. The lead-acid battery was
                                                                 designed to provide the high current
                          Z                                      required by the 40 - watt GOES transmitter
                                           ILSIR@IAEN@.T W@@     during its 1-minute transmissions
                                                                 scheduled every third hour. This 12
                                                                 volt supply also powered the ARGOS
                              VMCM1                              transmitter and the Weatherpak.
                                                                 The current meters, the navigation light,
                                                                 and the secondary ARGOS transmitter were
                              VWCM2                              all powered by their own alkaline
                                                                 supplies. Power usage by the STEM system
                                                                 was about 1.1 watts on average exclusive
                                                                 of the navigation light, current meters,
                Figure 7 Block,Diagrain Data Acquisition         and secondary ARGOS tranmitter. major
                               Telemetry System                  subsytem usage was approximately as
                                                                 follows:

               The controller was equipped with hardware         - ARGOS PTT (2-IDs)             = 0.33 watts
               and software to handle all of the STEM 1/0
               requirements (Figure 7). These included:          - GOES transmitter   (40-watts) =  0.60 watts
               -   SAIL communication with two current           - Controller                    =  0.04 watts
                   meters sharing a single pair of
                   conductors.                                   - Weatherpak                    =  0.13 watts
               -   SAIL communication with a modified              Total                            1.1  watts
                   ARGOS transmitter.
               -   SAIL communication with a modified                            6.0 RESULTS
                   Coastal Climate Weatherpak.                   Two problems became apparent following
               -   RS232 interface to a synergetics GOES         deployment. First, data from the upper
                                                                 VMCM at 55m was not being telemetered.
                                                    7AW

                   transmitter                                   This turned out to be a cable polarity
                                                                 problem which was repaired on the repair
               -   A/D conversion for 8 channels of              cruise.
                   analog input

                                                              676

              one week after deployment the GOES                               maximum of about 11 repeats of the same
              transmission was lost. A deficiency in                           hour. Typically each data point was
              the GOES transmitter battery recharging                          collected 4 to 7 times. Use of a check-
              circuit proved to be the cause of the                            sum to eliminate data corrupted by the
              transmission loss. Prior to the                                  telemetry link resulted in automatic
              occurrence of this problem, when the                             elimination of about one transmission in
              transmitter batteries were still               fresh,            six.
              good quality data were transmitted and
              acquired by GOES link.                                           Meteorological data collected by the
                                                                               Weatherpak was of much poorer quality due
              Data quality from the          current meters was                to sensor,problems. The bearings on the
              excellent throughout the deployment. On                          RM Young Wind Monitor corroded away within
              the retrieval the VMCMs showed little wear                       10 weeks of deployment. The replacement
              and tear and their bearings were in good                         unit, which used modified bearings faired
              shape. An example of the current meter                           better. but was still somewhat affected by
              data is shown in Figures 8 and 9. In                             increased bearing friction. The
              general the level of redundancy used in                          Weatherpak compass worked reliably as did
              the data sent via ARGOS was more than                            the barometric pressure sensor, but the
              enough to ensure that no hourly data were                        humidity and air temperature sensors
              missed, other than one or two instances                          failed within a few weeks. The air
              where Service ARGOS had a system problem.                        temperature sensor lasted about one week,
              The level of redundancy in the messages                          and then apparently suffered a short
              received at WHOI varied from a minimum of                        circuit. The humidity sensor showed a
              two messages (for a single hour) to a                            gradual increase in humidity with time

                                 STEM - teLemetered data from VMCM-1, depth 55 m.

                                                                          (TqMPERRTUREI
                     12
                  Uj
                  Ll
                  cc 41
                  M                                              12 1-5 14 15  16  17 IS  19 M       22 . %23 24 25 26 27  28  29   30  31
                  L3   1   2   3   4  5   a   7   5  9  to   11

                       10 cm/sec                                          urrent Vectors)

                                                                       IVECTOR DIRECTIONJ
                     360
                     7
                  U)
                  W  I:     a                        '
                  W
                  W

                     0                                                                    19 20   21 22  23 24  25  26' V  28  29   30  31-1
                       12.345610910111213141516171

                                                                         tVECTOR SPEED)
                     so-

                     40.

                  (n 30.
                                                                                                  A
                                                                                                  IL
                     20.                                                                                              a

                     10                                                v
                                                                                    V%'

                       1   2   3   4  5   6   7   a  9  10   11  32 13 14  25  16  17 IS  19  20  21 22  23  24 25  26  27 28  29   30  31
                                                                           March 1988

                                                Figure 8     Telemetered Current Meter            Data
                                                                     VMCM-l (55m)

                                                                           677

                                         STEM    LeLemetered data from VMCM-2, depth 257 m.

                        C@                                                                (TEMPERRTURE)
                         12

                        W
                        w
                                                                                                               %o%o%o
                        LJ     1   2   3    1  5     6   7   8    9  10" 11 '02   13     14 15   is  17   10 19  20  el    22 23   241  25  26   27  28  29  30   31 -7
                        M

                            N
                               10 cm/sec                                                 (Current Vectors)

                                                                                         (VECTOR DIRECTION)
                         360
                        tj
                        u
                        a: 180'
                        uj
                        co

                               1   2   3    4  5     6   7   8    9  10   11  12  13     14 15   16  17   18 19  20  21    22 23   24   25  25   27  28  29  30   31

                                                                                         (VECTOR SPEED)
                         so.

                         10-

                        Lo 30-                                                                                                     .1

                         20-
                                                                                                                                         %

                               P

                               1   2   3    4  5     6   7   8    9  10   11  12  13     14 15   16  17   36 19  20  21    22 23   24   25  26   27  28  29  30   31
                                                                                           March 1988

                                                           Figure 9       Telemetered Current Meter Data
                                                                                  VMCR-2 (257m)

                    until it read 102% humidity all the time.                                    the STEM design can provide reliable
                    Figure 10 shows typical telemetered data                                     mooring and telemetry performance for
                    from the Weatherpak.                                                         periods of six months or longer in most
                                                                                                 ocean environments. The performance of
                    Various engineering data were telemetered                                    the meteorological package was
                    at regular intervals. Figure 11 shows a                                      disappointing,and more sensor testing and
                    time series of some of the engineering                                       evaluation is required before long-term
                    data. Of particular interest are the                                         reliability can be assured.
                    tension measurements which were made                                         The incremental costs for using
                    directly beneath the surface buoy.                                           telemetering surface moorings rather than
                    Tension values averaged between 1000                        and              standard surface moorings with internally
                    2000 pounds and varied from instantaneous
                    lows of near zero to values exceeding 3000                                   recording instruments are not known in
                    pounds which occurred during periods of                                      detail, but are primarily influenced by
                    high currents.                                                               the additional costs of the cable and
                                                                                                 terminations, the controller and its
                                         7.0 CONCLUSIONS                                         special software, and the testing
                                                                                                 procedures required to ensure that all
                    The STEM experiment was the first                                            subsystems operate correctly. More
                    successful use of a general purpose                                          detailed information on costs and long
                    electromechanical cable to moor a surface                                    term reliability will not be available
                    buoy in deep water under very severe                                         until more experience is gained with these
                    weather conditions. None of the critical                                     systems.
                    components, namely cables, connectors,
                    instruments or buoy showed excessive signs
                    of wear and tear. Thus, it appears that

                                                                                          678

                                    1030                                                                                 (BarometrLc Pressure)
                                    9901

                                                    gkpe-A@. A.                                      jlolel-                                                                                  'Aar
                                    NRVRS@ -                                                         R7, //r/ RR @- 'N'T1 gill                                        Py
                                    10 m/sec                                                                             (WLnd Vector.

                                    360.                                                             (DIRECTION FROM WHICH WIND IS BLOWINGI
                                    (n                                                               %ft%&                                            %.:. - -
                                    w
                                    0@ lea-'                                                         dw
                                    CD
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                                    1     2         3       4                                        7" 'ena910 1 @112 '1314 'IS16          a   1 @920       @2122            @232,   @2525         @2728                29 3a 31

                                                                                                                         (VECTOR SPEED)
                                    40-

                                    30-

                                    V7
                                    20'

                                    to-

                                    0
                                                            5                                                                                   %
                                    1     2 -3                    6                                  7
                                                                                                     a910 11 12 13       ill 15           18 17 18 19 ZU     21       22      23 24   2S  26        27 2@                29 30 31
                                                                                                                         March- I
                                                                                                     Figure 10 Telemetered Atmospheric                       Data

                                                            STEM - teLemetered data
                                    3000.                                                                                (TENSION)
                                    2000-x          xxxxxxx xxxxxxxxxxx                              xx X xx x xx x x    x x xx x Xx x xx x xx x xx          x        xxxx x  xxx x   x   xx  X x   X X xx X xx x xx x
                                    xxx xxxxxx                                                                                                                                x       a
                                                            13                                                                                                                                                           X
                                    1000' 0013 00 a C313 ao13 a a a 013 p 00 a C30                   013 (313a                            a13130coo                           a           00130
                                                                                                     00 +00000013013     13 a 13 M 0      13        001310            00 CIO+ 00013+                a                    13 , 013
                                                                                                     + ++4                                0                                   + +4 4                1313 1313            p 130
                                    + ++ + ++ + ++ + ++     + ++                                     + + ++                               + �+ �4+ ++ + *+ + ++4 +    4+      +           ++ + +                         .. . . . .
                                    0               34      5   a                                    7                                                                                                ++ +
                                                                                                     12    13            15               16 17 10 11 20     21       Z2 Z3   Z11     25  25  27    28                   29 30 31

                                                                                                                         (CONTINUITY)
                                    2050 x x x x x x x x x x                                         x x x x x x x x x x                                              x x
                                    4
                                    850:                                                                                                                                                                                 xx
                                    51:             13a                                                                                                               0       a           13
                                                                                                                                                                                      a
                                    1 ISO -                                                          13a   13
                                    1050:                       a                                    a                   a                aa                 a
                                    850
                                    650                                                                                                         +                                                                        0
                                                                                                     910 11 12 33        14 15            16 17 18 19 20     21       22 23   24      25  25  27    28                   i9 30 it

                                                                                                                         (16 VOLT SUPPLY)
                                    20"
                     'n             5-6   1�        t       7& 76 is                                 att�bn              @s IS            nba       h        t        t       8       a       7A    4                    ISa6
                     -3 :+ + + + + + + + +                                                           + + +               + + + + + +                                  + + +                   + +                        + +

                                    1  2            31      5   8                                    70910 11 12 13      14 15            16 17 Ja 19 20     2t       22 23   24      25  26  27    28                   29 30 31

                                                                                                                         (SECONDARY       BATTERY)
                                    20-

                     -JIS-x x x x x x x x x x x x                                                                                         x x x     x x x x x                                       x x x x
                     CD
                     >              P  -P           P43     -P  43                                   43 -P 43 -P 13 -P 43 -P+             -P 43 -P -P -P     P        -P -P   P       -P  13  43    -P                   43P43
                                    301   1         1       ''    '                                  '''''I              II.              '''       '        ''       '       '       ..      I     I                    '''
                                    1  2            34      5   6                                    78910 it' 12 13     14 IS            16 37 ia 10 20     21       22 23   24      25  26  27    28                   29 30 31

                                                                                                                         (PRIMARY BATTERY)
                                    30-

                     -j             25-

                                    20
                                    1  2            34      5   6                                    70910 It 12 13      14 15            16 17 18 19 20     21       22 23   24      25  28  27    28                   29 30 31
                                                                                                                         MARCH 1988
                                                                                                     Figure 3.1 Telemetered Engineering Data

                                                                                                                         679

                           ACKNOWLEDGEMENTS                   (7) Briscoe, M.G. and D.E. Frye, June
              The authors want to express their               1987. Motivations and Methods for Ocean
              gratitude to the engineers and                  Data Telemetry. Marine Technology Society
              technicians, at WHOI and in the Industry,       Journal. Vol. 21, No. 2, pp. 42-57.
              who provided expertise and support to the
              STEM program. In particular we want to          (8) Melligner, E.C., K.E. Prada, R.L.
              thank S. Kery for detailed mooring              Koehler, and K.W. Dohertyi August
              analysis, P. 01 Malley and M. Gould for         1986.Instrument Bus An Electronic System
              the development of the E/M cable                Architecture for Oceanographic
              terminations, S. Longworth for the design       Instrumentation, Woods Hole Oceanogr.
              and preparation of the engineering              Inst. Tech. Rept. WHOI # 86-30,
              instruments, E. Denton and J. Hardiman
              for extensive electronic technical              (9) institute of Electrical and
              support and D. Payne and S. Tarbell for         Electronics Engineers (IEEE). 1983. IEEE
              data dissemination.                             Standard 796-1983, Standard Microcomputer
                                                              System Bus, IEEE, 245 East 47th Street,
              We are grateful to the skippers and the         New York, NY.
              crew of the R/Vs ENDEAVOR, IDA-Z, and
              OCEANUS for safely deploying, servicing,
              and recovering the STEM mooring.
                                                              wHOI Contribution No. 6862
              We want to thank B. Pratt who provided the
              art work and T. Shipley for preparing the
              paper.

              Finally the continued interest and support
              of Dr. S. Ramberg, Dr. A. Weinstein and
              Dr. D. Evans of the Office of Naval
              Research in the field of telemetry from
              moored arrays should be recognized and is
              gratefully acknowledged.

              The work reported in this paper was
              performed under ONR Contract Number
              N00014-86-K-0751 and N00014-84-C-0134, NR
              083-400

                              REFERENCES

              (1) Berteaux, H.O. Buoy Engineering.
              1976. Wiley and Sons, Inc., New York,
              N.Y.

              (2) Clay, P.R. and H.O. Berteaux. 1987.
              The High Performance Oceanographic Mooring
              (HIPOM). MTS/IEEE Oceans 187, Halifax
              Conference Proceeding.

              (3) Driscoll, A., Editor. 1982. Handbook
              of Oceanographic Winch, Wire, and Cable
              Technology. Graduate School of
              Oceanography. University of Rhode Island.
              Narragassett, RI.

              (4) Gibson, P. 1984. Operational
              Characteristics of Electromechanical
              Cables. ASNE. Energy Sources Technology
              Conference, New Orleans, LA.

              (5) Bocconcelli A., Editor. 1987. Real
              Time Environmental Arctic Monitoring
              (RTEAM) Woods Hole Oceanogr. Inst. Tech.
              Rept. WHOI-87-50.

              (6) Institute of Electrical and
              Electronics Engineers (IEEE). April 1985.
              IEEE Standard Serial ASCII instrumentation
              Loop (SAIL) Shipboard Data Communication,
              IEEE Standard 997-1985. 12p.

                                                         680

                                                  NEW TECHNOLOGIES AND DEVELOPMENTS
                                                       IN NDBC BUOY AND MOORING DESIGN

                                                                                    LT Daniel R. May, USCG

                                                                             National Data Buoy Center (NDBC)
                                                                                Stennis Space      Center, MS 39529

                                                  ABSTRACT                                               mooring systems are less labor intensive and require less ship deployment
                                                                                                         time due to the ease in handling.
                   Since the early 1970's, the National Data Buoy Center (NDBQ has
                   deployed deep-ocean weather buoys and mooring systems. Starting in                    Initial engineering concerns were concentrated on the nylon/polypropylene
                   1980, new deep-ocean, bottom-insensitive, inverse-catenary mooring                    connection and the long-term performance of polypropylene as a moor-
                   systems were deployed based on developments of the late 1970's. Since                 ing component. An integral splice between the nylon and polypropylene
                   1980, refinements to the basic mooring design have been made incor-                   segments was the desired approach, although due to the differences in
                   porating recent technical developments, such as use ofnoncorrosive plastic            line diameter size, a special splice was considered. The difference in line
                   materials. In addition, new developments have been made in mooring                    diameters occurred when designing an overall line strength requirement
                   design for reduced mooring costs, in recoverable mooring systems, and                 for the mooring system. Since nylon line is approximately 80 percent
                   in prevention ofdamage to mooring linesfromfishbite. During this same                 stronger than polypropylene, size for size, a much larger diameter
                   period, buoy hulls have undergone new developments, with the trend be-                polypropylene line was required to equal the strength of the nylon
                   ing toward smaller, lightweight, more durable hulls. Use and develop-                 segment.
                   ment of new foam buoys have recently been undertaken for adaptation
                   in nearshore coastal applications.                                                    During the period 1982-1984, research was conducted on the use of
                                                                                                         polypropylene as a long-term, deep-water mooring component. Also,
                                                                                                         numerous tests were conducted on various types of combination
                                                                                                         nylon/polypropylene splices. All results indicated that the polypropylene
                                            1. INTRODUCTION                                              mooring line would perform adequately if an acceptable
                                                                                                         nylon/polypropylene splice could be developed. Using 8-strand plaited
                   The National Data Buoy Center (NDBQ conducts research, development,                   construction ropes, numerous nylon/polypropylene size combinations
                   testing, and deployment of buoys and moorings in the deep-ocean en-                   were spliced together using standard butt splices. During this testing period
                   vironment. The organization was established by the U.S. Coast Guard                   over 30 combination rope splices were evaluated with excellent results.
                   in 1967 and transferred to the National Oceanic and Atmospheric Ad-                   As expected, a tapered style splice, where the larger polypropylene line
                   ministration (NOAA) in 1970. Presently, NDBC continues to operate a                   is slowly tapered as it is spliced into the smaller nylon line, proved to
                   fleet of moored buoys that provides real-time meteorological data to the              be the best overall splice. See Figure 1. For the nylon-to-polypropylene
                   National Weather Service and other agencies.                                          side of the splice, a standard butt splice was used. A standard butt splice
                                                                                                         for both sides of the splice was tested and worked as well as most all splices
                   The NDBC mooring program has been a unique developmental process                      tried, but these were cumbersome to make and had an uneven lay to the
                   that has evolved into a highly regarded asset of NDBC. The early research,            polypropylene-to-nylon splice area.
                   development, and testing, combined with the operational experience of
                   moored buoys, has led to a well-established, successful system of stan-
                   dard mooring designs. Refinement and enhancement of these standard
                   mooring systems in recent years has produced more versatile and less costly                   4
                   mooring systems.                                                                          A

                   A system of standard mooring designs was first established in 1978 based
                   on state-of-the-art technology. A minimum mooring design life goal of
                                                                                                                   A",
                   6 years was chosen for deep-ocean mooring systems. Preliminary testing
                   and development followed, with'operational deployments occurring in
                   1980-1981 through the present. Time has proved these designs to be suc-
                   cessful. NDBC currently has one mooring system over 71/2. years old and
                   several other mooring systems over 61/2 years old. In recent years, the
                   trend has been to refine these designs based on new technologies. Several
                   of these new enhancements are discussed in the sections below.

                       2. COMBINATION NYLON/POLYPROPYLENE
                                          MOORING SYSTEMS

                   This mooring system, which uses long lengths of nylon and polypropylene
                   line, was first suggested as an alternative version of the inverse-catenary
                   design developed in the early 1980's[l]. The polypropylene line provides
                   the required buoyancy, normally provided by glass spheres, for support
                   of the chain and hardware suspended off the ocean bottom. Several ad
                   vantages are achieved by use of this type mooring system. The difference
                   in material cost is quite substantial over the all nylon/glass sphere flota
                   tion type mooring since the polypropylene line is relatively inexpensive.
                   A cost savings of approximately $4-5 K can be realized for a mooring
                   system deployed at a depth of 3,050 meters. Also, deployment of these                 Figure 1. NylonlPolypropylene Splice

                                                                                                   681   United States Government work not protected by copyright

                     Deployed in September 1984 off the Hawaiian Islands at a depth of 4,850
                     meters, the first deep-water combination nylon/polypropylene mooring
                     system is still in use after over four years service. Additional                                                              W,
                     nylon/polypropylene mooring systems have been deployed at deep-water                                                     . ......
                     locations as shown in Table 1. No failures or problems associated with
                     the polypropylene line or the combination nylon/polypropylene splices
                     have been seen to date. Presently, use of these systems has been expand-
                     ed to shallow water locations and to all other deep water locations
                     wherever feasible. Shallow water locations (900 to 1500 meters) require
                     the    use   of larger       diameter     polypropylene       line    (5.72-
                     centimeter diameter).
                                                                                                                                                   5"  S
                                                                                                                 Ile,

                                                                                                                                                        10
                     Table 1. Combination AylonlPolypropylene Mooring Systems

                       STATION      BUOY TYPE      DEPTH (M)       DEPLOYED        RECOVERED
                         51002        NOMAD          4,850         09/05/84       STILL IN USE
                         44004        NOMAD          3,230         12/16/84       STILL IN USE
                         32302       3-METER         4,200         01/19/86       STILL IN USE
                         41002        NOMAD          3,655         03/26/86         06/03/86
                         46006      12-METER         3,930         06/28/86       STILL IN USE
                         46037       3-METER         3,500         08/08/87         09/22/87
                         46002        NOMAD          3;425         04/29/87       STILL IN USE

                                                                                                                                 M

                         3. USE OF PLASTICS IN MOORING SYSTEMS                                           Figure 2. Standard NOMAD Mooring Insulator

                     One area that NDBC has examined in recent years in regard to im-
                     provements in mooring systems involves the use of nonmetallic com-                  internal bolt system and placed through the yoke connection. An over-
                     ponents. New innovations in the use of high-strength, low-wear plastics             sized steel split-key shackle connects by a hole bored through the bolt.
                     have prompted evaluation of these materials for use as components in                See Figure 3. Tests over the past 3 years have indicated this design works
                     seawater mooring applications.                                                      well, although some wear and brittleness is seen in the acetal bushing after
                                                                                                         1 V2 to 2 years. Two buoys are currently fitted with this design, but with
                     One component currently being evaluated for use in long-term, deep-water            a new shortened bushing, for further field testing.
                     mooring systems is the plastic rope thimble. Currently, NDBC uses cast
                     aluminum-bronze rope thimbles that have a special urethane coating. The             Another application utilizes a press-fit type bushing coupled with a stan-
                     coating helps protect the synthetic mooring line as well as isolate the thim-       dard Coast Guard split-key shackle (Figure 4). Several plastic materials
                     ble from its connection to a carbon steel connecting shackle. The thimbles          were examined, including acetal, acetron (a specially engineered acetal)
                     are heavy, cumbersome, and somewhat expensive after application of the              and thordon (a shipboard rudder and shaft bearing material). Thus far,
                     special urethane coating. The plastic thimbles, manufactured by Sam-                the thordon material appears to show the best performance based on ex-
                     son, use a hard plastic internal spool and a protective urethane cover              perimental data. Two NOMAD buoys are currently outfitted with this
                     shield. They are lightweight, easy to use, and are comparably priced. The           type design, one with an acetal bushing and one with a thordon bushing,
                     spool, which must support the mooring loads by providing a bearing sur-             and will be recovered in the late fall of 1988. Based on the results of the
                     face for the mooring line and connecting steel shackle, is composed of
                     a specially engineered nylon of high strength with dispersed lubricants
                     for excellent wear properties. NDBC has used many of these plastic
                     thimbles in developmental mooring systems over the past 3 to 4 years
                     with excellent results. Upon recovery and inspection, it was found that                                51@
                     all thimbles had performed exceptionally well without any degradation
                     to the plastic shield or spool components. In November 1985, two of these
                     thimbles were deployed in an operational mooring system with a 3-meter
                     discus buoy in the Hawaiian Islands. The mooring system, located in the
                     Alenuihaha channel between the islands of Hawaii and Maui at a depth
                     of 1,010 meters, was recovered in July 1988 after 3 years of service in
                     a high-current, rough-channel environment. This mooring system is ser-
                     ving as a long-term evaluation of the plastic thimble for exclusive use
                     in all NDBC deep-water mooring systems.

                     In another application, several new plastics are under evaluation as isola-
                     tion and bushing materials used in the connection of NDBC's NOMAD
                     buoy to its mooring system. The NOMAD buoy has a 316 stainless steel
                     mooring yoke that provides good strength and corrosion performance
                     for long-term seawater applications. Presently, a special stainless steel
                     shackle combined with a 2-meter spliced loop of 11/4 -inch-diameter nylon
                     line is used to connect the buoy to its carbon steel mooring chain. Use
                     of the looped nylon line, called an insulator (Figure 2), isolates the
                     dissimilar metals from contact in seawater. This design has been in use
                     for over 10 years with excellent results, but could be improved and made
                     less costly by using a different isolation/connection technique at the buoy                                                                  A*
                     yoke.

                     Several new isolation/connection techniques are being evaluated using
                     plastic isolation bushings coupled with a standard carbon steel connec-
                     ting shackle. In one application, an acetal bushing is threaded onto an             Figure 3. Special Purpose Split-Key Shackle Connection

                                                                                                  682

                                                                                                                                                                   Table 2. NDBC Fishbite Mooring Failures

                                                                                                                                                                                                          SITE        DAYS ON                 TYPE                FAILURE DEPTH
                                                                                                                                                                                     LOCATION        DEPTH (FT)        STATION          MOORING LINE                      (FT)
                                                                                                                                                                                          25-54.3 N       11,1340            71         1.75'DIA NYLON                      545
                                                                                                   WIP"                                                                                   89-42.4 IN
                                                                                                                                                                       1980
                                                                                                                                                                                          25-00.0 N       10,600           1.118        1.25' DIA NYLON                   3.350
                                                                                                                                                                                          88-00.0 W
                                                                                                                                                                   3 FAILURES                                        -
                                                                                     .4-                                                                                                  26-00.0 N       91996              724        1.625* DIA NYLON                  1,350
                                                                                                                                                                                          93
                                                                                                                                                                                          -30.0 W
                                                                                      VM-l,                                                                            1981               NONE
                                                                                                                                                                                          34-64.2 N
                                                                                                                            MIR    M                               1 FA191LSURE           72-53.5 W       13,880             377        1.75* DIA NYLON                     820
                                                                                          T',                                                                          1983               29-18 0 N                          293        1.125* CIA NYLON                    350
                                                                                                                                                                                          77-18.1 W
                                                                                                                                                                                          23-24.0 N
                                                                                                  lp                                                               2 FAILURES                             10,680             886        1.75' CIA NYLON                   2,075
                                                                                                                                                                                          62-18.0 W
                                                                                                                                                                       1984               NONE
                                                                                                                                                                                          29-18 8 N
                                                                                                                           '1.1111,1:@,;141'11 @q
                                                                                                                                                                                          77-19.8 W       u,z,u_             am         1.125'DIA NYLON                     220
                                                                                                                                                                                          32-18.0 N
                                                                                                                lq
                                                                                                                @@, , I 1                                                                                 12,396                        1.75' DIA NYLON                   1,500
                                   il$ 114,01,lili                                                                                                                     1985               75-17.4 W
                                                                                                                                                                                          26-54.9 N       10,200             9D9        1.75' DLA NYLON                     950
                                                                                                                                                                                          89 42.7 W
                                                                                                                                                                                          32-16.0 N
                                                                                                                                                                       1986               75.1 4.0 W      12,000             46         1.125" DIA NYLON                  1,400
                                                                                                                                                                   2 FAILURES             29-19.0 N       3,420              377        1,125' DIA NYLON                  i,800
                                                                                                                                                                                          77-21.OW
                                                                                                                                                                       1987               25.58.3 N       10,380           2,368        1.75' CIA NYLON                     850
                                                                                                                                                                   1 FAILURE              85-55.9 W

                           Figure 4. Third Class Split-KeylBushing Combination                                                                                                            AVERAGE DEPTH OF FAILURE - 1,350 FEET BELOW SURFACE
                                                                                                                                                                                                     AVERAGE TIME ON STATION - 769 DAYS

                           ongoing field tests, a final plastic configuration NOMAD yoke connec-
                           tion is anticipated for early next year.                                                                                                evaluations, including tensile break-strength tests, will be performed to
                                                                                                                                                                   provide an indication of how much strength was lost due to fishbite.
                                              4. FISHBITE-RESISTANT MOORING                                                                                        The goal of this new study by ND13C is to develop a fishbite-resistant,
                                                           CABLE DEVELOPMENTS                                                                                      long-term, mooring cable as well as further the scientific knowledge of
                                                                                                                                                                   moorings and the fishbite phenomenon. Based on the results of the study,
                           Fishbite of mooring cables is the phenomenon by which mooring lines                                                                     should a particular cable be identified as successful, it would be strongly
                           are damaged or severed by the bite of various ocean species, most notably                                                               considered for use in NDBC's current mooring design. A final report on
                           sharks [2]. NDBC first encountered the fishbite problem during the early                                                                the results of the study is expected to be completed in January 1989.
                           1970's during the deployment of its weather data buoys in the Gulf of
                           Mexico. After early studies indicated no precise explanation for the
                           phenomenon or any solution for a deep-water, long-term, synthetic moor-                                                                 5. RETRIEVABLE SYNTHETIC MOORING SYSTEMS
                           ing system, NDBC continued with its development for the best overall
                           mooring system, omitting any specific fishbite protection. This approach                                                                Deep-water synthetic mooring systems deployed by NDBC are typically
                           worked quite well until the early 1980's, when the buoy network was great-                                                              not recovered; however, where similar type moorings are used in in-
                           ly expanded, especially with the use of smaller buoy hulls and smaller                                                                  termediate water depths (150 to 610 meters) or the Great Lakes, a means
                           diameter mooring lines. During this period and in the following years,                                                                  of retrieval can be provided on the synthetic line. Since NDBC buoy opera-
                           mooring failures due to fishbite began to occur more frequently (Table 2).                                                              tions are supported by U.S. Coast Guard buoy tenders (Figure 5) the
                                                                                                                                                                   means of synthetic line retrieval is designed for use by the lifting boom
                           Due to this increase, and since new technical advancements had been made                                                                located on each ship. Normal operation of the boom is in the lifting and
                           concerning mooring cables, NDBC began a renewed study of the fishbite                                                                   pulling of buoy chain. Thus, a series of retrieval loops were designed for
                           problem. The first portion of the study involved laboratory screening of                                                                use on the mooring line so that it could be recovered in the same man-
                           numerous developmental cables in an attempt to test their "fishbite                                                                     ner. Due to the location of the boom and available deck space, the max-
                           resistance." Most of these cables were new parallel fiber construction                                                                  imum distance retrieval loops can be spaced apart is 6 to 8 meters. Thus,
                           cables with specially designed jackets or construction techniques to pre-                                                               for long lengths of line to be retrieved, numerous loops are required.
                           vent damage resulting from cutting. The screening tests were conducted                                                                  Early loop designs were developed when long Tz (temperature vs. depth)
                           by the Ocean Engineering Department at Woods Hole Oceanographic                                                                         lines were used as integral members of a buoy mooring system in the ear-
                           Institution and included investigation of the cutting force required to sever                                                           ly 1980's. Cables up to several hundred feet long were installed in the
                           the cable (both in the slack condition and with the cable under tension),
                           stabbing force, and cut resistance.                                                                                                     near-surface portion of the mooring and required retrieval loops for
                                                                                                                                                                   routine servicing and removal. The loops consisted of segments of 8-strand
                           From the results of the initial study, four different type cables showed                                                                nylon line braided back onto the Tz cable in an increasing helic: angle
                           an ability to resist cutting[31, This led to the second phase of the study,                                                             or "Chinese finger" fashion. When placed under load, the strands of
                           which involves a field test of the four cables in an attempt to gain actual                                                             the line became taut against each other holding the loop in place. These
                           fishbite experience. The field test portion of the study is being conducted                                                             same type loops were used in a Gulf of Mexico mooring on a single
                           by Old Dominion University in conjunction with an ongoing study of                                                                      305-meter segment of 8-strand nylon line. The loops held just as well on
                           FAD (Fish Aggregation Device) buoys off the coast of Puerto Rico. The                                                                   the nylon line as they had on the jacketed Tz cables. The only drawbacks
                           cables are being deployed during the summer of 1988 on lightweight buoys                                                                to these particular type loop designs are the manhours involved in
                           off the coast of the Island of Culebra. Fish attractors will be placed on                                                               installation of the loops and the possibility of some slight slippage dur-
                           each mooring system to establish an FAD. Previous use of these type FAD                                                                 ing use. Complete fabrication and installation requires approximately one
                           systems in these waters showed a significant amount of mooring line
                           fishbite. The test cables will be physically inspected and their underwater                                                             manhour per loop which, when long segments are involved, can be costly
                           condition videotaped periodically for evidence of fishbite. Cables that                                                                 and time-consuming.
                           exhibit a high incidence of fishbite or any unique type of fishbite damage                                                              In 1986 efforts began on formulating a standard retrieval loop design
                           will be removed from the existing mooring for further analysis and testing.                                                             based on modification of the previous design. Emphasis was primarily
                           Additional lengths of cables will be used to replace removed segments                                                                   on the installation method since this was seen as a deficiency of the early
                           to continue the evaluation period. At the end of the summer or early fall,                                                              design. Three separate retrieval loop designs, all using 8-strand nylon line,
                           all buoys and mooring systems will be recovered and a final inspection                                                                  were developed, fabricated, and tested for evaluation. The three designs
                           and analysis will be made of the four cables' condition. Additional                                                                     are shown in Figure 6. A variation of the Type A design was also tested
                                                                                                                                                                   where the loop was spliced back up onto the mooring line. All designs

                                                                                                                                                       683

                                                                                                      method used the "Chinese finger" type method of attachment using the
                                                                                                      four legs of the loop in a braid down the mooring line. The second method
                                                                                                      used a loop with much shorter length legs and involved splicing the loop
                                                                                                      into the mooring line by following the four pairs of strands with each
                                                                                                      leg of the loop. The latter method was the least difficult method and re-
                                                                                                      quired less than 10 minutes to install.

                                                                                                      Excellent results were achieved on all loops during repeated break tests
                                                                                       a
                                                                                                      of both loops. Slight slippage was seen on the "Chinese finger" loops,
                                                                                             p
                                                                            UIMA;1111@' F'  @,Mcj
                                                                                 02"                  although they held to ultimate break strengths of approximately 9,980
                                                                                                      kilograms. (Individual leg strength was rated at 6,530 kilograms.) The
                                                                                                      spliced-in loops worked extremely well and, with a single leg strength of
                                                                                                      3,900 kilograms, provided a consistent break strength of approximately
                                                                                                      7,250 kilograms.

                                                                                                      Continued development of synthetic mooring line retrieval loops is
                                                                                                      planned with more testing of the spliced-in type Kevlar loops. An increase
                                                                                                      in single line size to achieve a final break strength of approximately 9,000
                                                                                                      kilograms is the goal. From all development and testing thus far, this
                                                                                                      appears to be the best overall design, as well as the quickest and easiest
                                                                                                      to install.

                                                                                                                   6. BUOY HULL DEVELOPMENTS

                                                                                                      Development of new, low-cost, smaller, moored buoy hulls has been a
                                                                                                      major goal of NDBC during the 1980's. Maintenance and refurbishment
                                                                                                      costs of the large 10- and 12-meter discus hulls have reached prohibitive
                                                                                                      levels, especially in austere budget years. The excellent seakeeping
                                                                                                      NOMAD buoys are ideal for offshore (100-250 nm) and severe-
                  Figure 5. USCG Buoy      Tender                                                     environment locations, such as the Gulf of Alaska, but, at $80 to $100 K
                                                                                                      per buoy hull, are too costly for nearshore or coastal applications.
                  worked extremely well, providing over 9,000 kilograms wet break strength            In the early 1980's NDBC began investigating an aluminum 3-meter discus
                  and only requiring about one-half the installation time. No slippage or             hull with a design similar to that developed by Woods Hole Oceanographic
                  excessive elongation was seen during the numerous tests performed. Of               Institution. NDBC procured four of these buoy hulls of varying configura-
                  the two type A designs, the first design appeared to be the better. In the          tions and in 1983-1984 began deployments in coastal areas and in the Great
                  alternate version, when the loop is under load, the top portion of the              Lakes. After a successful deployment of one year (1984-85) off the en-
                  loop fibers cut against each other since the splice is made back up onto            trance of the Columbia River, the 3-meter buoy hull was declared opera-
                  the mooring line.                                                                   tional, and an additional 15 hulls were procured for replacement of 10-
                                                                                                      and 12-meter hulls and for expansion of the buoy network in the coastal
                  During 1987 another retrieval loop design was developed and tested us-              area. The standard configuration 3-meter buoy hull is shown in Figure
                  ing a special Kevlar fiber as the material for the retrieval loop. The pur-         8. The hull of the buoy is constructed of 5086 marine grade aluminum
                  pose in developing this new loop design was first to seek additional im-            with the tripod mast constructed of 6061 grade aluminum. A rigid, three-
                  provements over current designs, and second to gain additional knowledge            leg, steel bridle is attached to the hull for stability and for the mooring
                  with the interworking of different synthetic fibers such as nylon and               connection. Additional data on the 3-meter buoy are shown in Figure 9.
                  Kevlar. To construct the loop, two segments of equal length each were
                  folded over into a loop. A short piece of shrink-tube was used over the             Continued success of the 3-meter hull as a moored meteorological plat-
                  line for chafe protection and to give the loop its rigid shape. A completed         form has been achieved with deployments in the South Pacific, Pacific
                  loop is shown in Figure 7. The loops were attached to 8-strand nylon                Northwest, in the straits of the Islands of Hawaii, and increasingly in
                  mooring line in two different fashions for testing. The first

                                                              LOOP DESIGN A                LOOP DESIGN 8                 LOOP DESIGN C

                                                           TAPE                                          TAPE                          TAPE
                                                           END            1-118" NYLON                   END                           END

                                                                                                          1-118" NYLON                 1-3/4" DIAMETER 8-STRAND NYLON

                                                                        MAKE LOOP 8-101A DIAMETER
                                             SPLICE BACK (EACH SIDE)    OFF MAIN LINE                                                  1-1/8" DIAMETER 8-STRAND NYLON
                                             2 DOUBLE TUCKS
                                             3 SINGLE TUCKS

                                                                                                                                        MAKE LOOP 8-10" DIAMETER
                                                                                                                                        OFF MAIN LINE

                                                                           1-1/8' NYLON

                                                           6-7'                                                       6.7

                                                                            EYE SPLICE TECHNIQUE
                                                                             6-15" DIAMETER EYE           6-8" DIAMETER EY@E                 Figure 6. Retrieval Loop Designs
                                                                                                 684

                                               8-10'

                                                         PLASTIC
                                                         SH INK TUBE
                                                         OVER FLATBRAID

                                                     WHIP EACH SIDE OF LOOP
                                                     AND ENTIRE BUNDLE

                                                     LIGHTLY COAT WITH FLEXANE
                                                     AFTER WHIPPING

                                                                                                                                3-METER DISCUS

                                                                                                                   1.  (3D01)
                             6                                                                                         a.  HULL WEIGHT                 1,887 LB
                               6-)                                                                                     b.  POWER SYSTEM                   610 LB
                                                                                                                       c.  PAYLOAD                        100 LB
                                                                                                                       d.  BALLAST                        500   LB
                                                                                                                       e.  DEPLOYED                    3,300 LB
                                                                                                                       f.  VCG                            2.5 FT

                                                     2 SEGMENTS (12 LONG EACH) JETSTRAN                            2.  (3D02 - 3D19)
                                                     207 KEVLAR FLAT BRAID
                                                     (FOLD OVER TO FORM LOOP)                                          a.  HULL WEIGHT                 2,600   LB
                                                                                                                       b.  POWER SYSTEM                   660 LB
                                                                                                                       c.  PAYLOAD                        210 LB
                                                                                                                       d.  BALLAST                          0  LB
                                                                                                                       e.  DEPLOYED                    3,470 LB
                                                                                                                       f.  VCG                            2.4 FT

                                                     .t___1APE OR WHIP EACH END

                  Figure 7 Kevlar Retrieval Loop                                                   Figure 9. 3-Meter Buoy Hull Data

                                                                                                   New offshore deployments of 3-meter buoy hulls are planned in 1989 and
                                                                                                   1990 in the Gulf of Mexico and the North Atlantic Ocean, as well as new
                                                                                                   coastal locations. One such coastal application will be approximately 32
                                                                                                   kilometers off Cape Canaveral, Florida, for timely weather observations
                                                                                                   in support of NASA's Space Shuttle program. An additional quantity
                                                                                                   of 3-meter buoy hulls is being procured during 1989 in support of these
                                                                                                   and other programs. The cost of the new hulls is approximately $20 K
                                                                                                   per buoy.

                                                                                                   Also, NDBC has recently developed the use of foam in the construction
                                                                                                   of small buoy hull designs. One such buoy was constructed this past winter
                                                                                                   for use as a marker buoy off the coast of California. The buoy will sup-
                                                                                                   port existing NDBC mooring systems while operational buoy hulls are
                                                                                                   refurbished, rebatteried, or outfitted with new calibrated sensors. The
                                                                                                   foam material used in the construction of the buoy hull is a special surlyn
                                                                                                   material. It is lightweight (48 kgs/m3 density), extremely durable, per-
                                                                                                   manantly colored throughout, nonwater absorbant, and requires no
                                                                                                   additional protective outer skin. Figure 10 shows the marker buoy con-
                                                                                                   figuration prior to shipment to the west coast. It is designed such that
                                                                                                   the mast, hull, and counterweight tube can be disassembled for easy
                                                                                                              hen required for operational use, the buoy can be assembled
                                                                                                   storage. W
                                                                                                   in less than 30 minutes and is capable of supporting a 2,268-kilogram
                                                                                                   mooring load. A dry-cell-powered Obstruction and Identification Light
                                                                                                   provides approximately 6 months on-station time if required.
                Figure 8. 3-Meter Discus Buoy                                                      Small foam buoy hulls are also being considered for nearshore coastal
                                                                                                   applications. This potential application includes wave measurements as
                                                                                                   meteorological measurements. This lightweight (less than 340 kilograms),
                coastal applications that include offshore Cape Hatteras during the winter         low-cost buoy hull could be adapted for use in almost any nearshore loca-
                of 1987-1988. The 3-meter deployment in the Pacific Northwest                      tion as well as in bays and inlet areas. Similar to the 3-meter hull, such
                (48* 17'11 " N and 133'45'43 " W) was for a I -year duration and resulted          buoys could be carried onboard a vessel or towed to its station.
                in the highest significant wave height (over 14 meters) recorded by a
                3-meter buoy. A new directional wave system, adapted specifically for
                the 3-meter hull, has gained high acceptance from other government agen-                                   7. CONCLUSIONS
                cies and weather forecasters in areas subject to problems associated with
                high waves and storm surge. Additionally, a new upper mooring system               The National Data Buoy Center is committed to the further development
                has been designed, along with a towing pendant, for easier deployment              of buoy, mooring, and meteorological systems for timely, accurate, and
                and retrieval. In most coastal areas (less than 65 kilometers offshore) the        low-cost weather observations. The recent developments in synthetics,
                3-meter buoy can be towed to station and deployed by a small vessel.               plastics, foams, and new buoy and mooring designs during the 1980's
                Retrieval and exchange of buoys can also be performed on station without           will provide the basis for further improvements and developments in the
                hoisting the buoy from the water through the use of a synthetic mooring            1990's.
                retrieval pendant. An experimental exercise in the Gulf of Mexico this
                past winter showed the buoy can be towed in seas of less than I meter
                by small Coast Guard vessels, such as the 17-meter Aids to Navigation
                Boat.

                                                                                             685

                                                                                J
                                                                                ', @ 77

                                                            7

                                      A'N

                    Figure 10. Foam Marker Buoy

                                          &REFERENCES

                    I .NOAA Data Buoy Office, NDBO Buoy Mooring Workshop Report,
                       Department of Commerce, NOAA, Bay St. Louis, MS, September
                       1978.
                    2. Prindle, Bryce and Robert G. Walden, Deep Sea Lines Fishbite Manual,
                       Department of Commerce, NOAA, Bay St. Louis, MS 1975.

                    3. Prindle, Bryce, Preliminary Assessment of Fishbite Resistance of Lines
                       Designed for Use in Deep Sea Mooring, Woods Hole Report No.
                       400-QANW-6-00458:S-1, Sponsored by National Data Buoy Center,
                       Department of Commerce, NOAA, Bay St. Louis, MS, May 1987.

                                                                                     686

                                                  INTERNATIONAL ICE PATROL APPLIED OCEANOGRAPHY

                                                       Stephen R. Osmer and Donald L. Murphy

                                             Commander, international Ice Patrol, U. S. Coast Guard
                                                        Avery Point, Groton, CT 06340-6096

                                        ABSTRACT                              The prevalence of        fog,    the accumulation Of
                                                                              icebergs, the severe storm conditions so common in
               The     United    States     Coast     Guard     utilizes      this region, the concentration of trans-Atlantic
               oceanographic     research    in    accomplishing      its     shipping, and the presence of oil platforms and
               assigned International Ice Patrol mission.             The     fishing vessels scattered over the Grand Banks
               international Ice Patrol is using side-looking                 make this one Of the potentially most dangerous
               airborne radar for improved iceberg detection and              areas in the world for marine transportation.
               to observe ocean surface features (i.e. fronts,
               eddies); is applying current velocity and sea                  The international Ice Patrol          (iiP)    operations
               surface temperature data from satellite-tracked                center, located in Groton, Connecticut, maintains
               oceanographic     drifters;    has   instituted      using     a plot showing the location of all icebergs
               aircraft-launched      expendable       bathythermograpb       detected in its operations area (40*N-52*N and
               (AXBT) probes; and is using a        satellite infrared        39*W-57*W).    The primary data source is IIP's own
               imagery interpretation system.        The International        aerial reconnaissance detachment which patrols the
               Ice Patrol is striving to improve the quality and              north Atlantic for seven consecutive days on
               quantity of environmental data collected on the                alternate weeks during the six-month ice season
               Grand Banks of Newfoundland.       The data is used by         (March-August).    Each flight covers only a small
               U. S. Navy and Canadian environmental forecast                 portion of the     region.     These iceberg position
               centers to provide input data for the Ice Patrol's             data are augmented by the Canadian Atmospheric
               iceberg drift and deterioration prediction models.             Environment Service (AES) patrols, sightings by
                                                                              the offshore industry, and reports from vessels
                                                                              transiting    the    area.   An average of        300-400
                                                                              icebergs are tracked by the IIP each year; during
                                                                              severe ice years 1000-2000 iceberg might be
                                   1. INTRODUCTION                            tracked.

               The sinking of the luxury passenger liner RKS                  The iceberg sighting information is entered into a
               TITANIC in 1912 prompted maritime communities with             computer at the IIP Operations Center along with
               ships transiting the Grand Banks of Newfoundland,              ocean current,       wind,  wave,    and   sea surf ace
               Canada, to establish an iceberg patcol in the                  temperature data.     iIP utilizes two models - an
               area.   Since 1914, the United States Coast Guard              iceberg drift and prediction model and an iceberg
               has been tasked with the management and operation              deterioration model.
               of this patrol, known as the International Ice
               Patrol.    The patrol observes and studies ice                 Every   twelve      hours,   the   predicted      iceberg
               conditions near the Grand Banks and warns mariners             locations are used to estimate the limit of all
               of any iceberg threats.        The International Ice           known ice.    This limit, along with a few of the
               Patrol is funded by the twenty signatory nations               more critical predicted iceberg locations,              is
               to the Safety Of Life At Sea (SOLAS) Convention,               broadcast as an "Ice Bulletin" from radio stations
               who reimburse the United States government for                 in the United States, Canada, and Europe for the
               this service.    it has proven to be an outstanding            benefit   of   all vessels transiting the North
               example of effective international collaboration               Atlantic.   in addition to this bulletin, a radio
               for the preservation of life and property at sea.              facsimile chart of the area, visually depicting
                                                                              the locations of ice, is broadcast once each day.
               icebergs, mainly from glaciers in west Greenland,
               are carried southward by the cold Labrador Current                           2. ICEBERG RECONNAISSANCE
               to the vicinity of the Grand Banks and into the
               shipping lanes between Europe and the major ports              Since 1983,   IIP has utilized Coast Guard HC-130
               of the northeast United States and Canada.           This      aircraft equipped with a real aperture, X-band
               is also the area where the Labrador Current meets              side-looking airborne radar (SLAR) <an AN/APS-135)
               the relatively warm Gulf Stream; temperature                   as its primary reconnaissance tool (1,2,3).           The
               differences between the two water masses of up to              SLAR has an all weather capability which helps to
               20*C produce dense fog some 40-50% of the year.                negate the prevalent fog and adverse, weather
                                                                              conditions in the Ice Patrol operations area.

                                                                         687 United States Government work not protected by copyright

                 In June of this year, IIP conducted a ten day SLAR             The drifters are air-deployed from Coast Guard
                 experiment    of f Newfoundland      to    evaluate    the     HC-130 aircraft on routine ice reconnaissance
                 AN/APS-131 SLAR.     This SLAIR' is installed as part          flights.   They are equipped with a window-shade
                 of the AIREYE system aboard         Coast Guard HU-25          drogue tethered 50 meters below         the surface, a
                 aircraft (Falcon jet).                                         drogue-tension     sensor,    and     a   sea     surface
                                                                                temperature (SST) sensor.      Service  ARGOS processes
                 The fundamental goal of this research was to                   all sensor and position data and        relays them to
                 provide Commander, International Ice Patrol (CIIP)             IIP via computer link. These data       are also shared
                 with     guidance      on   the    ability      of     the     with all major environmental data collection
                 AIREYE-equipped HU-25 to perform the iceberg                   centers      worldwide      through       the      Global
                 detection mission of the IIP.       Specifically, there        Telecommunications System (GTS).
                 were two objectives:
                                                                                The wind input for the air-drag and wind-current
                      1. Provide CIIP with a basis for determining              computations is calculated from wind data provided
                 the best altitude for          iceberg searches .-    and      every   twelve    hours   by    the   Fleet    Numerical
                 predicting the probability of iceberg detection as             Oceanography Center (FLENUMOCEANCEV).
                 a function of sea state, range, and iceberg size.
                                                                                Deterioration Predictions
                      2.   Compare the iceberg detection capability
                 of the AN/APS-131 SLAR in the AIREYE package with              A parametric model is used to estimate the
                 the AN/APS-135 SLAR currently used on the IIP                  deterioration of an iceberg after its initial
                 HC-130 reconnaissance aircraft.                                sighting.    This model is used to predict the
                                                                                removal of a "melted" iceberg from plot.
                 The Atmospheric Environment Service            (AES)    of
                 Canada also had two of its SLAR-equipped ice                   Deterioration is calculated as a function of
                 reconnaissance aircraft@ participate.      Their SLAR's        monthly   averaged   solar     insolation,   and    daily
                 were an AN/APS-96 and a CAL-100.         Their interest        estimates of water temperature, wave       height, and
                 was to evaluate performance.          This cooperative         wave   period    (approximately      85%   of    iceberg
                 effort is the latest in a long series between IIP              deterioration     is    due    to     wave     effects).
                 and AES (4).                                                   Deterioration from calving and aerial melting are.
                                                                                ignored (12, 13).
                 The U. S. Coast Guard icebreaker NORTHWIND acted
                 as the surface truth platform, recording iceberg               Water temperature and wave data are provided by
                 target     information     and     the     environmental       FLENUMOCEANCEN.
                 conditions.
                                                                                Forecast Limitations
                             3. OPERATIONAL FORECAST MODELS
                                                                                The major shortcomings in operational forecasting
                 Drift Predictions                                              of the iceberg danger are:       (1) the accuracy of
                                                                                the iceberg sighting (position, size, and shape);
                 once an iceberg has been reported to the IIP                   (2) computational constraints which require IIP to
                 operations center, its location, size, and shape               place the icebergs into broad categories of size
                 are entered into a computer drift model that is                and shape; (3) the resolution of the current,
                 used to estimate the subsequent motion of @the                 temperature, and wave fields; and (4) the quality
                 iceberg.   The use of the model is necessary for               of the environmental data.
                 two reasons:     first, so that future sightings of
                 an iceberg are recognized as resights rather than              Using the drifters improves on the mean currents,
                 as new sightings,       and,   second,    so that the          and provides additional sea surface temperature
                 position of an iceberg can be estimated if no                  data, but ten to twenty drifters per year cannot
                 resighting is made.                                            adequately cover the entire operations area for
                                                                                the six-month ice season.
                 This dynamic model combines the effects of water
                 drag, air drag, the Coriolis acceleration, and sea             The latter two shortcomings are classic concerns
                 surface     slope    to . determine      the     iceberg       of regional forecasts.       In the IIP operations
                 acceleration. Wave forces are ignored (5,6).                   area,  data observations are sparse,           seriously
                                                                                degrading forecasts and requiring the use of
                 Model    input   data   are    derived   from    several       grid-spacings which smooth    much of the data useful
                 sources.    The mean geostrophic current field is              to IIP.
                 based on hydrographic surveys conducted by the
                 Coast Guard from 1936 to 1974.       Because this,mean                          4. RESEARCH EFFORTS
                 current   field     fails  to   incorporate     temporal
                 variability    of     the  flow    field,   IIP    began       In an ef fort to improve the input data, IIP has
                 air-deploying          satellite-tracked           TIROS       been discussing with FLENUMOCEANCE9, Naval Eastern
                 Oceanographic Drifters (TOD's) in 1983 and         using       Oceanography Center (HAVEASTOCEANCEN), *and the
                 their drifts     to modify the historical          field       Canadian   Maritime     Command/Meteorological
                 (7,8,9,10,11).    Between ten and twenty buoys are             Oceanography Center (MARCOM/METOC) ways to improve
                 deployed each season.                                          the quality of analysis and quantity of data
                                                                                collected in the area.

                                                                          688

             During the 1988 ice season, IIP provided drift                  In 1988, lip also provided real-time SLAR analysis
             trajectory data       to WAVEASTOCEANCEff for ocean             of ocean surface features (i.e. eddies, fronts) to
             feature analysis during 1988.                                   WAVEASTOCEANCEN and MARCOM/METOC.

             lip is equipping future drifters with barometric                Also in 1987, lip conducted a second research
             pressure sensors.      This data, along with the SST            cruise in an effort to expand its limited data on
             data, will be available to FLENUMOCEANCE9 and                   iceberg deterioration from USCGC TAMAROA.             six
             MARCOM/METOC.                                                   icebergs were studied, and their motion compared
                                                                             to deployed TOD's.
             These drifters could also be equipped with other
             sensors such as thermistor chains if sponsors                   lip    has  put    together    atlases    of   the    TOD
             could be found.     The drifters have a life span of            trajectories since 1983 and SLAR feature analysis
             6 months and become entrained in the North                      since 1985.
             Atlantic Current around 45*W. In the past lip has
             ensured    the   processing     and   dissemination      of                           5. SUMMARY
             drifter    data   as   drifters    crossed    the    North
             Atlantic   although their importance of IIP ended at            The    international     Ice   Patrol     is     applying
             390W.                                                           technology and oceanography to conduct its mission,
                                                                             in the most efficient manner. Cooperative efforts
             The past two years, lip has been involved in a                  with U. S.    and Canadian agencies have given
             cooperative project with the Naval Oceanographic                excellent results in the previous years and hold
             Research and Development Activity            (NORDA)     to     great promise for the future.
             evaluate the potential of mini-drifters (sonabuoy
             size) (14, 15).       in February 1988, Coast Guard             -                    6. REFERENCES
             aircraft deployed eight of these mini-drifters in
             the Gulf of Mexico.          Based upon the initial             (1)    Thayer, N.  B., 1985. EFFECTS OF SIDE
             promising results, two more were deployed by lip                       LOOKING AIRBORNE RADAR (SLAR) ON ICEBERG
             aircraft in mid-March - one in the Labrador                            DETECTION DURING THE 1983 AND 1984
             Current and one in the North Atlantic Current.                         INTERNATIONAL ICE PATROL SEASONS. Appendix
             Two more were deployed in the IIP area in early                        C to Report Of The International Ice Patrol
             April.                                                                 in the North Atlantic 1984 Season, Bulletin
                                                                                    No. 70.
             The past year, IIP has been involved in an
             evaluation of installing an aircraft launched                   (2)    Thayer, V. B. and N. C. Edwards, 1987.
             expendable bathythermograph (AXBT) system on its                       ICEBERG/SHIP TARGET DISCRIMINATION WITH
             aircraft (16).      The evaluations were successful.                   SIDE-LOOKING AIRBORNE RADAR. Appendix B to
             A system was purchased and used during the 1988                        Report Of The International Ice Patrol In
             ice season.     The data, collected on lip flights,                    The Worth Atlantic 1985 Season, Bulletin
             was provided to      all three oceanography centers.                   No. 71.
             During the AXBT system evaluations, data were
             provided to and used by the Harvard Gulfcast                    (3)    Edwards, N. C. and W. B. Thayer, 1986.
             model.     AXBT*s    should    aid    in   future     SLAR             SIDE-LOOKIVG AIRBORNE RADAR DETECTION AND
             interpretation of   ocean surface features.                            IDENTIFICATION OF ICEBERGS. Proceedings
                                                                                    Of The Canadian East Coast Workshop On Sea
             Recent Ice Patrol research has focused on the use                      Ice January 7-9, 1986.
             of remotely sensed data to improve model inputs
             (i.e.   inferred    currents    and   SST).     Satellite       (4)    Osmer, S. R.. and H. McRuer, 1987. 1987
             infrared imagery, used with great success in many                      PRESEASON ICEBERG SURVEY AND SEASON
             parts of the world's oceans to map oceanic fronts                      PREDICTION. Proceedings OCEANS '87, Vol 1.
             and infer circulation, is limited to a few images
             per months by the persistent fog and clouds in the              (5)    Mountain, D. G., 1980. ON PREDICTING
             IIP region.     However, imaging radars (i.e. SLAR)                    ICEBERG DRIFT. Cold Regions Science And
             can map ocean frontal features through clouds and                      Technology, Vol 1 (3/4) pp 273-282.
             fog.    The Ice Patrol has been evaluating the
             detection of ocean surface features by SLAR since               (6)    Murphy, D. L.  and I. Anderson, 1987. AN
             1985 (17).                                                             EVALUATION OF  THE INTERNATIONAL ICE PATROL
                                                                                    DRIFT MODEL.   Appendix D to Report Of The
             In 1986,    Ice Patrol used its SLAR to map the                        International  Ice Patrol In The North
             boundaries of a warm core eddy located between the                     Atlantic 1985  Season, Bulletin No. 71.
             Labrador and the Worth Atlantic Currents (18).
             Concurrent hydrographic survey conducted by USCGC               (7)    Summy, A. D.,  1984. OCEANOGRAPHIC
             EVERGREEN and satellite imagery showed          that the               CONDITIONS ON  THE GRAND BANKS DURING THE
             SLAR would      reliably map the eddy           location,              1982 INTERNATIONAL ICE PATROL SEASON.
             although interpreting radar imagery of the sea                         Appendix B to Report Of The International
             surface still requires much research.            in 1987               Ice Patrol In The North Atlantic 1982
             another warm core eddy was studied             by SLAR,                Season, Bulletin No. 68.
             satellite     imagery,     and    surface     hydrography
             collected from USCGC BITTERSWEET.

                                                                       689

                  (8)     Anderson, 1., 1984. OCEANOGRAPHIC                       (13)    Anderson, 1., 1984. ICEBERG DETERIORATION
                          CONDITIONS On THE GRAND BA14KS DURING THE                       MODEL. Appendix C to Report Of The
                          1983 INTERNATIONAL ICE PATROL SEASON.                           International lee Patrol In The North
                          Appendix B to Report Of The international                       Atlantic 1983 Season, Bulletin No. 69.
                          lee Patrol in The Worth Atlantic 1983
                          Season, Bulletin No. 69.                                (14)    Anderson, 1., 1987. MINI-DRIFTER BUOY
                                                                                          FUNCTIONAL TEST. International lee Patrol
                  (9)     Anderson, 1., 1985. OCEANOGRAPHIC                               Technical Report 87-2.
                          CONDITIONS ON THE GRAND BANKS DURING
                          THE 1984 INTERNATIONAL ICE PATROL SEASON.               (15)    Thayer, N. B., D. L. Murphy, and W. A.
                          Appendix B to Report of The International                       Henry, 1988. TEST AND EVALUATION OF THE
                          lee Patrol In The North Atlantic 1984                           COMPACT METEOROLOGICAL AND OCEANOGRAHIC
                          Season, Bulletin No. 70.                                        DRIFTER (CMOD). international lee Patrol
                                                                                          Technical Report 88-02.
                  (10)    Anderson, 1., 1987. OCEANOGRAPHIC
                          CONDITIONS ON THE GRAND BANKS DURING                    (16)    Alfultis, M. A., 1988. INTERNATIONAL ICE
                          THE 1985 INTERNATIONAL ICE PATROL SEASON.                       PATROL AXBT EVALUATION. International Ice
                          Appendix C to Report Of The International                       Patrol Technical Report 88-05.
                          Ice Patrol In The North Atlantic 1985
                          Season, Bulletin No. 71.                                (17)    Thayer, N. B. and D. L. Murphy, 1987.
                                                                                          DETECTION OF OCEAN FRONTS IN THE GULF
                  (11)    Anderson, 1., 1988. TOD OCEANOGRAPHIC                           STREAM/LABRADOR CURRENT SYSTEM BY SIDE-
                          DRIFTER TRACKS ON THE GRAND BANKS DURING                        LOOKING AIRBORNE RADAR. Appendix F to
                          THE 1986 INTERNATIONAL ICE PATROL SEASON.                       Report Of The International lee Patrol In
                          Appendix B to Report Of The International                       The North Atlantic 1985 Season, Bulletin
                          Ice Patrol In The North Atlantic 1986                           No. 71.
                          Season, Bulletin No. 72.
                                                                                  (18)    Murphy, D. L., and I. Anderson, and N. B.
                  (12)    White, F. M., M. L. Spaulding, and                              Thayer, 1988. OBSERVATIONS OF AN OCEANIC
                          L. Gominho, 1980. THEORETICAL ESTIMATES                         FRONT SOUTH OF FLEMISH PASS. Appendix C to
                          OF THE VARIOUS MECHANISMS INVOLVED IN                           Report Of The International lee Patrol In
                          ICEBERG DETERIORATION IN THE OPEN OCEAN                         The North Atlantic 1986 Season, Bulletin
                          ENVIRONMENT. U. S. Coast Guard Research                         no. 72.
                          And Development Center Report CG-D-62-80.

                                                                              690

                                                       OCEANOGRAPHY ON EAGLE AUSTRALIA '88 CRUISE

                                                       Ross L. Tuxborn, Lieutenant Commander, USCG

                                                                   International Ice Patrol
                                                                              Avery Point
                                                                   Groton, Connecticut 06340
                                                                                                                  ,z
                                                                                                      ff-Z
                                                                                                       14,  r
                                         ABSIRACT                                                        rt @C-     Al FV
                                                                                                      0
                                                                                                          HIM          1 3@ @@,               , -
                                                                                                         f         "A  @ 1 -1 -          A
                                                                                                                       k9o, i@li'o' F
                    On 26 January l9ffl Australia celebrated its blCentelnlal                                                         W*4
                                                                                                                   r
               with a parade of tall ships in Sydney Harbor. Representing
               the United States was the Coast Gjard's EAGLEa three masted
               barque used for training the service's future officers.
                                                                   ht
                    EAG[ F's voyage to Australia and back took eig
                                                                      months.
                                                                                                                 Av
               During that period, Umning was conducted for the 290 cadets
               who were embarked for the two phases of the cruise.    A.course
               in meteorology and physical oc                                                            501@,*
                                             4anography was part of the
               onboard curriculum.
                    Additionally                                                                              F191 I
                                  FAIR served as a platform of opportunity
               for a number of projects. NOAA installed SEAS cnboard to                                     J,
               facilitate weather and xBr observations.      -r                                                                     Ylir C,
                                                         odle    projects
                                                                                                             j
               included marine mamnal observations, plankton taws, and sea
               surface pH measurements.
                    The environmental data was supplied to, forecasters and
               researchers worldwide who are trying to comprehend the
               interactions between the ocean and abmso-@ere. The hends-on
               experience the cadets received in all aspects of observatim                                              Alw      k',
                                                                                                                            3@    I
                                                                                                                  Q
               and data collection was an attarxement to the daily classroom
               work and was invaluable in guiding the cadets taards an
               understanding of the marine environaent.

                                    1. INTRODUCTION

                    The Tall Ship EAGLE has long        been associated
             with   the nautical education of Coast Guard
             officers. This paper describes a recent expansion
             of that role; to not only be a testing ground for
             nautical skills, but, also to serve as a floating
             classroom for academic courses and provide a                            Figure 1. USCGC EAGLE (WIX 327).
             platform for oceanographic research.
                    EAGLE is homeported at the Coast Guard                           a war reparation from Germany. Originally she was
             Academy, located on the Thames River in New              London,        the German naval training ship HORST WESSEL; built
             Connecticut. The Academy is a four year college
             with an enrollment of approximately 800 cadets.                         in 1936 by the Blobm and Voss Shipyard, Hamburg,
             Young men and women who successfully complete the                       Germany (Regan and Johnson, 1986).
             program graduate as commissioned officers with                                EAGLE's hull, masts, and deck structures are
                                                                                     constructed of steel. The term "barque" refers to
             Bachelor of Science Degrees. About half of the                          the sail   .rigging. Figure 2 shows the sail
             Coast Guard's officers come from the Academy.                           configuration.
                    Training on EAGLE is an integral part of a                             In addition to the mission of cadet training,
             cadet's professional education. A cruise on the                         the EAGLE has often participated in celebrations
             sailing ship gives cadets the chance to apply the                       marking important events. EAGLE was the lead ship
             professional skills they learn. Normally these                          for the tall ships parades into New York harbor for
             cruises take place during the summer and are less                       the US Bicentennial in.1976 and for the Statue of
             than ten weeks in duration.
                    New London has been the home for the EAGLE                       Liberty Centennial in 1986. When the invitation
             since 1945, when the vessel was commissioned into                       for EAGLE to take part in Australia's bicentennial
             the Coast Guard following World War II. EAGLE was                       celebration held in 1988 was accepted by the Reagan

                                                                                691   United States Government work not protected by copyright

                                                                    main       0                     Er e       7royal
                                                                               Yal\
                                                                                                  Le           FK%
                                                                                                        opg;
                                                                  main                                        Ilant
                                                                  topgalla
                                       gaff               8         main upp   .er          5          fore          pper
                                                                    tops i                              top          ail
                                       topsail

                                                                                              6        fore
                                   X                                 ain       lower      %                          lower.,
                                                                                                                     topsai
                                                                               topsail

                               spanker                 10i
                                                                               mair@sail                             foresail         4
                                                                                                    7

                      1. flying jib          4. fore topmast staysail               7. main topmast staysail                  io. mizzen staysail
                      2. outer jib           5. main royal staysail                 8. mizzen topgallant staysail
                      3. inner jib           6. main topgallant staysail            9. mizzen topmast staysail
                      Figure 2. Sail plan of USCGC EAGLE (from                 EAGLE Seamanship).

                    Administration, it set in motion events which                             numbered approximately 200. Cadets, Academy
                    caused significant departures from the norm in                            instructors, and personnel assigned full time to
                    Academy education planning and led to the                                 the ship comprised the crew. A complete change of
                    unprecedented voyage of EAGLE to Australia.                               instructors and cadets took place in Australia on
                                                                                              30 December. In all, about 280 cadets were
                                          2. ACADEMIC PLAN                                    involved.
                                                                                                     Members of the EAGLE's permanent crew made the
                          Australia's bicentennial celebration was 26                         entire eight month voyage. The forty five officers
                    January 1988. EAGLE left New London on 10                                 and enlisted personnel were the backbone of each
                    September 1987 to travel the 14,000 nautical miles                        phase's crew for this a        'rduous undertaking.
                    distance to arrive at Sydney, Australia on time.                                 During the semester at sea two courses were
                    It was 6 May 1988 before EAGLE returned home to New                       given to the sophomores, known as "Third Class"
                    London.                                                                   cadets (Class of 90) while the seniors, known as
                          Since cadets made up the majority of EAGLE's                        "First Class" cadets (1988 year class) received
                    crew and the voyage occurred during the Academy's                         one. Third Class cadet courses were:
                    1987 Fall and 88 Spring semesters, special                                Organizational Behavior and Meteorology and
                    arrangements were devised to provide academic                             Physical Oceanography. The one the First Class
                    courses. A constraint was that those cadets who                           cadets received was a 4.7 credit hour nautical
                    participated still had to'complete their education                        science course entitled Deck Watch Officer. Its
                    in four years.                                                            topics included: Shiphandling, Sail Handling,
                          For the first time in the Academy's modern                          Navigation, Watchkeeping, Communications, and Rules
                    history academic courses were held in the summer.                         of the Road.
                    The entire Class of 1990 and about fifty members of                              Topics covered by the Meteorology and Physical
                    the 1988 class attended the summer session to                             Oceanography Course included: weather elements,
                    complete two thirds of a normal semester course                           atmospheric circulation, weather notation, weather
                    load. The other third of the load was received                            chart analysis, physical properties of seawater,
                    onboard EAGLE during the voyage.                                          oceanic circulation, waves, and tides.
                          The cruise was       divided into two phases which                         This course was very well suited for
                    coincided with the Fall and Spring semesters back                         presentation at sea. Everyday, observations of
                    at the Academy. EAGLE's crew for each phase                               clouds, sea state, and other environmental

                                                                                        692

                                                                                   AUSTRALIA              1 88
                                                                                     9/10/87-- 5/6/88
              60                                                                                   -Will
                                                                                                    4 O%b
                                                                                                               NEW
                                                                                                             I)LONDON
              30

                                                                                                        %%
                                                                   H                               '7
                                                                     AWAII

                 0

                                                SAM GA                  TAHITI

                                                           TONGA
              -30
                                                    Y

                                                                                       Phase 1
             -60                                                                       Phase 2 ---
                         -120           -150            190           150           120            9 0
              figure 3. Australia '88 Cruise Track.

              conditions were used for in-class discussions.           cutters, i.e. High Endurance Cutters and Polar
              Nature cooperated often by providing phenomena to        Icebreakers. The following goals could then be
              reinforce lessons.  For example, Hurricane Emily's       met. EAGLE would serve as a platform of
              crossing of EAGLE's track in late September 1987         opportunity for collection of environmental data
              fit nicely with the lesson on tropical cyclones.         along its track. Practical experience in
                   By having both marine science and nautical          observation and data analysis would be passed to
              science co'urses, the point was stressed that            the cadets. The observations would be used daily
              rudimentary knowledge of oceanography, as well as        to reinforce the weather and oceans lessons. And,
              navigation skills are important to the safe              environmental data would be available for input to
              operation of an ocean-going vessel.                      the ongoing operational planning for the ship
                                                                       (especially essential for a sailing ship).
                            3. DATA COLLECTION PLAN                         Projects were planned with the Naval
                                                                       Underwater Systems Center (NUSC) in New London and
                   Prior to this voyage EAGLE had no                   with NOAA. These included synoptic weather
              environmental sampling capability other than that        observation, expendable bathythermograph (XBT)
              which is typical of smaller Coast Guard vessels.         casts, collection of surface water samples for pH,
              Observation of weather and the transmission of the       and marine mammal observations.   Also set up was a
              encoded data was done, but, only once or twice per       cadet project to collect plankton in the South
              day because the ship was billeted with only one          Pacific.
              radio operator.
                   It was decided in the early stages of cruise                           4. EQUIPMENT
              planning to install oceanographic and meteorologic
              sampling equipment onboard EAGLE to upgrade its               Equipment needed for EAGLE's science program
              -capabilities to match those of larger Coast Guard       came from a variety of sources. Primary

                                                                   693

                           B              XBT SECTION('00 TAHITI LEG                                             101S.7     A
                        T160:S                                                                                  910 .       S
                       1 1V @iz Y@                                                                                      2:W
                                          @4     0      (62.     0        6.
                                                                                                T,

                 50-
                          2
                 100-
                         2 3
                          2
                 150-

                 2100-

                 250-

                 300-

                 350-

                 400-

                 45
                 rneTers

                 Figure 4. Temperature cross-section A-B in South Pacific Ocean.
                           Station 50 is in the Galapagos Island Group.

                 contributors were: NOAA's National Marine Fishery        polar orbitting satellites when they were over the
                 Service (NMFS) and National Ocean Service (NOS),         ship. Two display monitors were connected to the
                 NUSC, and the Academy's Department of Science.           WSR. One located in the Navigator's space, near
                     NOAA extended tremendous assistance by               the bridge, was used by personnel conning the ship.
                 providing the advanced SEAS (Shipboard                   The other was in the classroom and was used daily
                 Environmental Data Acquisition System) for               for demonstrations. Between the two pieces of
                 collecting and transmitting (via satellite) weather      equipment, EAGLE was able to keep track of changing
                 and XBT data - and enough XBT probes for the             weather patterns.
                 entire cruise. SEAS basically consists of IBM                Modern methods of navigation, such as SATNAV,
                 PC-compatible microcomputer, GOES satellite              OMEGA, and LORAN C, were taught to the cadets and
                 transmitter with omni-directional antenna, and XBT       @used inconjunction with traditional celestial
                 controller and launcher. Complete description  of        navigation. Often, while in the open ocean, the
                 this system was provided by Szabados, Roman, and         electronic equipment would be turned off so*use of
                 Taylor, 1987.                                            the sextant could be emphasized. The blending of
                    Essential for obtaining weather information           technology with traditional nautical skills proved
                 for EAGLE's operational planning and for use in the      to be an interesting and effective approach to both
                 science course were a weather facsimile recorder         the marine science and nautical science subjects.
                 (WX FAX) and a weather satellite receiver (WSR).
                 Weather charts were received over WX FAX from                              5. OBSERVATIONS
                 broadcasting stations which covered the areas of
                 ocean the ship transited. The WSR received                   The kinds of environmental observations and
                 infra-red and visual images from NOAA-9 and NOAA-10      the numbers of each made are shown in Table 1.

                                                                      694

             Table 1: Oceanographic and meteorologic                  will gra duate to the fleet and again be involved in
             observation made during Australia '88 Cruise.            XBT casts, weather reporting, and other
                                                                      oceanographic studies. The program on EAGLE
                                                                      provided the cadet's valuable hands-on experience
                  Synoptic Weather      630 observations              that they will carry with them throughout their
                                                                      careers.

                  XBT                   230 casts (T6 and T7)                         7. ACKNOWLEDGMENTS

                  PH                    81 observations                    The author wishes to express his appreciation
                                                                      to NOS for providing SEAS. I am especially
                  Plankton tows         18 samples                    grateful to Gerald Bloom and Dave Pritchard for all
                                                                      their help with assembly and installation of the
                  Marine Mammal         41 sighting reports           system onboard EAGLE. The help provided by Charley
                                                                      Brown of NUSC in putting together equipment is also
                                                                      acknowledged.
                                                                           Captain Ernst Cummings and the entire crew of
                  Synoptic Weather. When not in port, weather         EAGLE are gratefully acknowledged for their
             observations were made four times daily on the           invaluable cooperation with the onboard science
             synoptic hour. The data was encoded on NOAA Form         programs. In particular, ET1 Ray Weidauer is
             72-1A and relayed via SEAS to NOAA and US Navy           thanked for his technical support.
             forecast centers.
                  XBT. Drops were usually done twice daily, in                          8. REFERENCES
             the morning and evening, when EAGLE was in depths
             greater than four hundred meters. This data too          (1) Mellen, R.H., P.M. Scheifele, and D.G.
             was sent back to NOAA and Navy users by SEAS.            Browning. 1987. Global Model of Sound Absorption in
                  PH. Sampling the surface waters for PH was          Sea Water. Scientific and Engineering Studies,
             done once per day while underway from 12 to 29           Naval Underwater Systems Center, US Navy.
             September 1987 and 11 November 1987 to 8 February
             1988. This data was provided to NUSC researchers         (2) Regan, P.M. and P.H. Johnson. 1986. EAGLE
             for their ongoing study of the effects of PH on          Seamanship; 2nd Ed. Naval Institute Press,
             sound attenuation in seawater (Mellen, Scheifele,        Anapolis, MD.
             and Browning, 1987).
                  Plankton Tows. Collection of plankton was           (3) Szabados, M., R. Charles, and B. Taylor. 1987.
             done whenever the opportunity was presented. Which       Transmission of Real Time Oceanographic and
             was when winds were very light or when the one main      Meteorologic Data from Ships. Proceedings of the
             diesel engine was down for repairs. A Third Class        Oceans `87 Conference.
             cadet collected the samples for an upper-level
             research project to qualitatively describe plankton
             along EAGLE's South Pacific track. Interesting.
             instances of diurnal vertical migration and
             upwelling productivity were evidenced in
             preliminary analysis of the samples.
                  Marine Mammal Observations. On all occasions
             when marine.mammals were seen, sighting reports
             were completed. This data was provided to NMFS and
             NUSC researchers.

                                6. CONCLUSION

                  Real-time XBT and synoptic weather data
             collected on this cruise was distributed to
             interested users, including forecasters and
             researchers studying global ocean-atmospheric
             interactions. Data collected in areas of Pacific
             Ocean outside the usual sealanes should be of
             particular interest.
                  The skills gained by the cadets in observing
             and interpreting weather patterns went beyond what
             could be provided in a conventional classroom
             setting. On a daily basis EAGLE served as an
             ongoing lab for sharpening these skills and
             reinforcing the classroom presentations. Due   to
             the success of this course, plans to conduct a
             similar weather course during normal summer cruises
             are being developed.
                  The Coast Guard has a long history of
             participation in NOAA/Navy environmental programs.
             Many of the cadets who took part in this cruise

                                                                   695

                       UNITED SMTES NAVY OPERATIONAL oaEMEGRAPHY: FIGUIW- SNAW WITH OCEWO@ INTELLIGENCE

                                         Lieutenant Ocumander James A. McNitt, United States Navy

                                                  Office of the Oceanographer of the Navy
                                                     34th and Massachusetts Avenue, BW
                                                         Washirigton, DC 20392-1800

                                     ABSTRACT                                 Acquisition of hardware and software must be
                                                                          inrx:yvative, cost-effective, and affordable and
                 A key factor in enhancing the U.S. Navy's warfight-      lead to nOn-duPlicative but survivable systems.
                 ing capability in the 1990s is the ability of the        This Process is dependent upon a strong
                 on-scene ccmTander to utilize and exploit environ-       oceanography technology base, a closely coordin-
                 rental information in real-time. In order to ac-         ated and focused research and development pro-
                 cmplish this, Navy scientists and engineers are          gram, and full use of available technology and
                 developing integrated, tactical support systems          equipment.
                 which the fleet can use at sea. These support
                 system may be tailored for the specific mission of                PRESENT OCFANoGRAPHY ARcHrmc=
                 the platform or battle group as required. The tac-
                 tical support system meld a combination of real-             The present Ncmss architecture overtaxes the
                 tire data (remotely sensed or in-situ measurements)      ccuputer resources at the Fleet Numerical
                 with historical databases. These data are then           Oceanography Center (ENOC). Located in Monterey,
                 used as input to sophisticated predictive models,        California, FNoc generates Navy unique gicbal and
                 the output of which are used as aids to the Naval        regional scale atmospheric and oceanic rcdel
                 Oceano@@pher supporting the tactical derision            output data and products. Products are transmit-
                 maker. Ea#iasis is placed on usable and under-           ted as vector graphics data on the Naval
                 standable displays and ease of dissemination of          Enviramental Data Network (NEEN). Additionally,
                 products. This capability is further used when           FNOC trarLmnits fleet application products directly
                 @iwirtrmental factors are considered in all Navy         to ships by naval message. Fleet applications
                 weapm, sensor, and cmmmnication systems from             products are tailored to specific weapon, ccnmm-
                 early design tl@rough test and evaluation to full        ication, and sensor systems. These products rely
                 operational capability.                                  on historical and observed data to assess system
                                                                          effectiveness (e.g., sonar performance).

                                                                              The Naval oceanographic Office (NAVOCEANO)
                                     INTRODUCTION                         Operational Oceanography Center, located at the
                                                                          Stennis Space Center, Mississippi, uses in-house
                     The U.S. Navy operates, trains, and fights in        expertise and global oceanographic data collec-
                 the global air-ocean envirorment. over the past          ticn and assimilation to provide regional and
                 few years, the operating forces have increased           local scale analyses of remtely sensed data to
                 their awareness of the effects of the air-ocean          oceanography centers and fleet users by naval
                 environment on weapon, cmwinication, and sensor          message-
                 system. The primary goal of the Naval
                 Oceanographic and Meteorological Support System              The three regional oceanography centers and
                 (NCHSS) is to enable all fleet tactical decision         the two oceanography cmmand oextiers use the data
                 makers to make fall use of and exploit real-time         received on the NEEN to provide products to fleet
                 oceanographic information, including: oceano--           units by three methods: fleet broadcast (radio
                 graphic; meteorological; and mapping, charting,          teletYpe), alphanumeric products by naval message,
                 and geodesy information.                                 and satellite imagery and graphics by facsimile
                                                                          broadcast. In addition to the NEDN, the ooeano-
                     The foundation for a revolutiorkuy NCHSS is          graphy centers are connected to FNOC by the Naval
                 being built. Key to the oceanographic                    Environmental Satellite Network (NESN). The NESN
                 architecture of the 1990s are:                           provides Defense Meteorological Satellite Program
                                                                          (U,ZP) imagery to the Naval Satellite Display
                     1. Regionalization.                                  Stations (NSDS). The NSDS is an image processor:
                     2. Stand-alone battle group capability.              8-bit oriented with a 256 gray-scale and animates
                     3. Improved use of cmmmications.                     up to 50 images per loop.1 The oceanography

                                                                      696 United States Government work not protected by copyright

              centers are a igned the following areas of                   2. Bathythermal profile of ocean (temperature
              responsibility (ACR):                                    versus depth).

                  1. Naval Eastern Oceanography Center (NECIC)             3. Rawinsande derived atmospheric sounding of
              Atlantic Ocean                                           taTeratum, pressure, humidity, wind speed, and
                                                                       wind direction.
                  2.  Naval Oceanography Ccumand Center Rota
              (NOM)   Mediterranean Sea                                    4. Electronic Refractcmeter Set installed
                                                                       aboard carrier-based early airborne warning
                  3.  Naval Western Oceanograp@y Center (NWOC)         aircraft (E-2C) to measure the refractive index.
              Eastern Pacific Ocean
                                                                           Fbr the most part these point measuranents do
                  4.  Naval Oceanography Ccumand Center Guam           not accurately account for horizontal changes in
              (MCC)   Western Pacific and Indian ocean                 atmospheric and oceanic parameters. The TESS(2)
                                                                       units are now being upgraded to receive and
                  5.  Naval Oceanography Polar Center (NPOC)           process low resolution satellite data from the
              Polar Oceans                                             AN/SM2-6. Although TESS(2) enables the naval
                                                                       oceanog rapher@ to determine sea-surface temperature
                  Enlisted and officer oceanography specialists        gradients in cloud-free area , he still cannot
              are assigned to aircraft carriers, amphibious            apply it to the applications products.
              ships, and battleships. During the last two              Additionally, he is still dependent upon the
              decades the availability of satellite imagery has        oceanography centers for analysis and forecast
              dramatically improved the oceanographer's                products-
              capabilities at sea. The AN/SM-6 Satellite
              Receiving Set is the standard satellite receiving            Limitations of the present architecture
              set for afloat units. It receives and reproduces         include:
              selected AFT pictures transmitted from NOAA polar
              orbiting satellites and other foreign satellites.            1. oceanography centers and the fleet depend
              Some AN/SK@-6 units have been modified to receive        upon FNOC for all Navy oceanographic and meteoro-
              GOES and Eurqpean Space Agency Meteorological            logical products and fleet application products.
              Satellite (MBOSAT). The AN/M2-10 DMSP                    oceanography centers have a limited capability to
              Reoeiver-Recorder Set for Meteorological Data  is        generate products or provide input to FNOC
              the Navy standard EMP satellite reoei-hng set.           products.
              It is only available on a limited number of
              carriers. Both the AN/SQ-6 and AN/S4(@-10 have               2. Although TESS(2) has streamlined aspects
              reached the end of their lift
                                            ,Tles. The first           of afloat oceanography office routine, the battle
              AN/SM@-6 was purchased in 1969.   Maintenance and        group is still dependent upon significant
              repair are no longer cost-effective.                     quantities of data from the oceanography centers.

                  All aircraft carriers and aT#iibicus ships
              have the Tactical Enviram-ental Support System                OCEANOGRAPHY ARCHITECTURE OF TM 19901S
              (TESS(2)]; a data processing and display system
              hosted on the HP-9020 desktop cmpxter. TESS(2)               Two parallel efforts will determine the future
              databases include extensive historical oceano-           of naval oceanography: regionalization of the
              graphic data; weapon, cammunication, and sensor          shore-based support network and develcprent of a
              system parameters; and envimnmental applications         starxi-alone capability for the battle group using
              programs-                                                advanced ccnputer technology and assimila- tion of
                                                                       satellite data in tactical scale nowcast models and
                  These program provide products such as:              applications products.
              aircraft icing analysis, tidal prediction, sound
              speed profile, acoustic propagation loss, acoustic           Regionalization. The Oceanographer of the
              raytrace, electrawagnetic propagation summary,           Navy is sponsoring the development of a "store and
              electromagnetic path loss versus range,                  forward" capability to increase data ocmmuni-
              electromagnetic coverage diagram, and ballistic          caticnus from FNOC to the oo&viography centers
                    and densities corrections.                         through the distribution of gridded data,
                                                                       primarily analysis and forecast products. In
                  Real-time, locally cbserved inputs which can         addition to grid field data, the oceanography
              be used to provide environmental products using          centers will receive raster scan, alphanumerics,
              existing processors and resources are 1=ted to:          and binary data. The oceanography centers will
                 1. Surface observations of air and sea-surface        generate the products for their ADRs, provide
              (sea injection) taq3P_mture, wind speed and              input to FNOC's models based on local knowledge,
              direction, relative humidity, and atnoqlieric            and produce all fleet applications products on a
              pressure.

                                                                   697

                co-lor-ated TESS(3).3 Additionally, regionaliza_               Related Efforts. other resource sponsors
                tien will reduce the potential for a single point          within Navy'are funding system acquisitions which.
                of failure in data production.                             directly involve Naval Oceanography. The AV-8B
                   TESS(3) and AN/SK@-ll. A minim= of 71                   aircraft relies heavily upon digital map data-
                                                                           bases. The Navy Research, Development, and
                -TESS(3) units will be procured starting in 1990           Acquisition policy directs all program to con-
                for installation at shore sites and ships with             sider appropriate environmental factors in Navy
                .oceanography officer and enlisted personnel. The          weaporVsensor systems from program initiation
                TESS(3) full scale engineering development (ESED)          t1uvagh test and evaluation to full operational
                contract was awarded to lockheed Missiles and              capability.5 Naval oceanographers working within
                Space Ocapany, Inc., on 11 July 11988. The FSED            the Navy acquisition organization advise program
                phase will last only two years. operational                managers in this critical area. Many of these
                testing on an east coast aircraft carrier is               programs will be supported by TESS(3).
                scheduled for 1990 with initial operational
                capability scheduled for 1991.                                              CCNCIIJDING PjaAkPIZ

                   The aircraft carrier configuration of TESS(3)               Tactical Naval oceanography is more than an
                consists of three high-resolution image work               architecture. It is an aggressive, innovative,
                stations and three coapxter processing units               and exciting cmbination of experienced
                (CPU), each containing 16 megabytes of memory,             professionals and advanced technology. Industry
                operating at 20 million instructions per second            is playing a key role in that TESS(3) pushes
                (KIPS). Satellite imagery can be displayed as              available technology to its limits. The Navy
                1024 by 1024 by 8 bit images with a 4 bit graphic          laboratories are responding to an extraordinary
                overlay and a 256 gray-scale.   Fiber optic                challenge during a period of fiscal austerity.
                connections between caq)onents and interfaces will         Finally, the oceanographer of the Navy has placed
                prevent electromagnetic interference and enhance           tactical scale support at the top of his priority
                electrcmagnetic hardening. TESS(3) makes full use          list in order to achieve a near-term inprovement
                Of distributed processing. It is capable of                in services which is sure to have a widespread and
                receiving and processing satellite data thrvugh the        dramatic effect in the fleet.
                AN/SM-11 while generatinj up to three applications
                products, including both image and graphic                                      REFERENCES
                processing- The data management functions will
                automatically run the forecasting, application             1. CNOC. Satellite Data Utilization Plan, 1988.
                program control, and observer functions.                   Camronder, Naval Oceanography command, Stennis
                   TESS(3) automatically monitors and nkinages,            Space Center, NS 39529-5000.
                satellite data received from the AN/SMQ-11, which          2. CNOC. Naval Oceanography Equipment plan,
                replaces the AN/SK@-6 and AN/SM-10 receivers.              Vol. 1, 1987. Meteorological Equipnent.
                The AN/SMQ-11 receives direct transmissions from           Ocamander, Naval Oceanography Camend, Stennis
                polar orbiting satellites providing coverage of            Space Center, NS 39529-5000.
                approximately 1,600 nautical miles around the
                receiver. These data include: TIMS operational             3. CNOC. Concept of operations for the NEDN
                Vertical Samder (TOVS) and Advanced Vexy High              Oceanographic Data Distribution and Expansion
                Resolution Radiometer (AMM) data from the TIROS-           System, 1988. Comakinder, Naval Oceanography
                N/NOAA satellites and operational Linescan System          COUMM-1d, Stennis Space Center, NS 39529-5000.
                (OLS), Special Sensor Microwave Imager (SSM/I),
                and Special Sensor Microwave Temperature Soundex           4. COMSPAMUMSOCM. contract Specification for
                (SSMIT) data from the EMP satellites. It also              Tactical Environmental Support System [TESS(3)],
                receives WUAX data from GOES. The receiver and             Vol. 1. System level Performance and Design
                processing hardware are housed in twin 19 inch             Requirements, 1987. Coamander, Space and Naval
                racks. The trainable antenna system consists of            Warfare Systems Command (PM-141), Washington, DC
                two planar arrays.4                                        20363-5100.

                    The Naval Environmental Prediction Research            5. OPNAVINST 5000.42C. Research, Development,
                Facility (NEPRF) and Naval ocean Research and              and Acquisition Procedures, 1986. Chief of Naval
                Development Activity (NOMA) are developing                 Operations, Washington, DC 20350-2000.
                predictive models for TESS(3). Tactical scale
                ocean circulation and thermal structure models and
                atmospheric forecast models will require
                initialization data from the oceanography centers.
                innovative and technologically advanced
                assimilation techniques are being developed to
                enable TESS (3) to create howcasts from data
                received frcm the AN/S1,1Q-11. This capability will
                enable the battle group oceanographer to provide
                briefings and tactical reconwendaticris when data
                are root available from the oceanography centers.

                                                                        698

                                                  WINDROSE, PC SOFT`WARE FOR WIND DATA ANALYSIS

                                                                Kyle Monkelien, Thomas L Murrell

                                                      U. S. Minerals Management Service, Alaska OCS Region

                   ABSTRACT                                                             CRITERIA USED IN DESIGNING THE PROGRAM

                   The Minerals Management Service (MMS) requires that                  Several criteria were established for the development of
                   lessees collect and submit meteorological and                        this program:
                   oceanographic data for offshore oil and gas o       t'
                                                                 oyera ions in
                   frontier areas. The collection and anal ses      these data          1. The pro ram would have to be able to use
                   are necessary to establish a baseline =@Ich can be used              informat      from several databases and spreadsheet
                   to evaluate Critical Operations and Curtailment Plans                files.
                   and other regulatory requirements. To help in the
                   analyses of @yind data the MMS Alaska Outer                          2. The program would need to handle variable amounts
                   Continental Shelf (OC�) Region has developed a                       of data.
                   computer program which will produce both a tabular                   3. The rograrn would have to run on IBM PC-
                         a
                          m7 and agaphic summary in the form of a rose
                   sdui am8 Ta The 12         depicts the relationshi                         atidle hardware for ease of use and flexibility.
                                      ayam                            _p of the         comp
                   percentage of         in five magnitude intervals to the
                   direction of occurrence. The program is designed to                  4 *The program would have to be user friendly and menu
                   work with an IBM personal computer, or compatible,                   driven.
                   with an Enhanced Graphics Adapter (EGA). Hardcopy                    5. The program would need to provide hi h-quality
                   of the rose diagram can be obtained through the use of a
                   Hewlett Packard (HP) plotter and a tabular summary                   graphs ffir use in publications and also provUe tibular
                   Can be output through the use of the print screen                    summaries of the analysis.
                   function.
                                                                                                                                     Figure 1.
                                                                                        A review of current data-base and           Wind data.
                                                                                        spreadsheet software established
                                                                                        that an ASCII format could be
                                                                                        utilized to extract previously stored          20   12
                                                                                        data for use with the rogram. A                40   14
                   WHY THE PROGRAM WAS DEVELOPED                                        suitable format for thke Cata was            170    15
                                                                                        selected: the data were arranged
                                                                                        into two columns with the wind               230    22
                   The Minerals Management Service requires that lessees                direction in the First column and            240    15
                   collect and submit meteorological and oceanographic                  the wind speed in the second                 220    9
                                                                                        column (figure 1). Empt
                   data for OCS oil and gas operations in frontier areas.                                              y lines       200    17
                   The data collected by the operators includes data on                 (rows) or page breaks in the data            200    17
                   wind speed and dire        n, air and water temperature,             field were unacceptable. ASCII
                                          _@Oibjlity, current, and, where               files could be produced by several
                   relative humidity, cris                                                                                           200    18
                   applicable, data on ice coverage and ice movement.                   commercial software           rograms,       200    21
                   This is used to establish a baselifie for conditions which           including     EXCEI,        eymphony         210    21
                   can be encountered in frontier areas such as the                     DBASEIII Plus, as well as standard           200    18
                   Beaufort Sea, the Bering Sea, and the Chukchi Sea. The               editors     and      word-processin          200    20
                   baseline is used to evaluate Critical Operations and                 programs. A simple program m          9
                   Curtailment Plans and other information which is                     could be used to enter wind data             210    22
                   submitted in support of exploratory activities. The                  without the use of commercial                210    18
                   WINDROSE program was designed to analyze the wind                    database and spreadsheet roWrams;            11o    22
                   component ol the data supplied by lessees. Previous                  was also written. The WRID OSE               100    23
                   analysis of the wind data was accomplished through                   f] roNram was designed for use on,an         110    25
                   manual calculations and the hand drafting, of rose                        -compatible computer running
                   diagrams. This method of analysis was becoming                       DOS with an EGA monitor. Aii
                   inefficient due to the large, amounts of data being                  HP @o= any standard printer
                   submitted by the companies.             When we were                 can   e          producing a hard copy. Microsoft Quick
                   unsuccessful in our attempt to find a commercial                     Basic was used as the programming lanwe, and the
                   program which would meet the needs of our office, it                 drafting commands were written in                   Graphics
                   was decided to write a program inhouse.                              Language.

                                                                                  699 United States Government work not protected by copyright

                        HOW THE PROGRAM ANALYZES DATA                                                                                  Figure 3. Screen 2 - main menu.

                        The program provides an analysis of the percentage
                        occurrence of @vind speeds from eight direction ranges.                                            OPTIONS LIST FOR FILE - A. SAMIPLEI.PRN
                        The wind speeds are divided into six ranges: (1 cal
                        R2) greater than 0 knots but less than or eqD to 1%                                                1. PRINT OBSERVATION SUMMARY
                           ots, (3) eater than 10 knots but less than or equal to
                        21 knots, 41) reater than 21 knots but less than or equal                                          2. VIEW WINDROSE
                        to 33 knots M greater than 33 knots but less than or
                        equal to 47 knots, and (6) reater than 47 knots. The                                               3. SELECT NEW FILE
                        wind directions aregiven in 5egrees and are divided into
                        eight equal intervals. The program first examines the
                        data to determine the number &f occurrences per wind                                               4. QUIT
                        direction. It then calculates the percentages from each                                            MAKE SELECTION: 7
                        direction and uses that figure to draw a rose diagram.
                        The program also will produce a summary of the. rose
                        diagram in tabular form which can be printed using a
                        print screen function.

                        USER INTERFACE AND PROGRAM OUTPUTS

                        Screen 1
                        The first screen (figure 2) rompts, the user to input the                                     Figure 4. Printout of observation summary-- hardcopy
                        name of the file to be analyzed. At this point, the user                                                            output under Option 1.
                        can also ask to view a diiectory listing or to end the
                        program.                                                                                                  OBSERVATIONS SUMKARY FOR LEASE SAMPLE1 PRN WELL NO. 01
                                                                                                                                  BEGINNING -     00/OD/88 ENDING      00/00/;9
                                                   Figure 2. Screen 1.                                                            KAGNITUDES, CALM - S - 0      1 - O<S<-10     2 - 10<S<-21
                                                                                                                                  (S-KNOTS)       3 - 21@S-33   4 - 33@S<47     5 - S>t.7

                                                                                                                                  KhGNITUDE       DIRECTION         OBSERVATIONS

                                                                                                                                       I          N (338-22)              4
                                                                                                                                       I          HE          (23-67)     1:
                           ENTER    DRCVE:PATH\FILENAME], [D] FOR DIRECTORY, OR [E] TO END:?                                           I          B           (68-112     7
                                                                                                                                       1          BE (113-157)            8
                                                                                                                                       I          S (158-202  )           I
                                                                                                                                       I          SW          (203-247)   2
                                                                                                                                       1          W (24       a2
                                                                                                                                                              9;2 9 1     12
                                                                                                                                       1          NN (2 -337)             6

                                                                                                                                       2          M (33       "-22)       6
                                                                                                                                       2          ME (23-67   )
                                                                                                                                       2          E (68_112)              29
                                                                                                                                       2          BE          (113-157)   13
                                                                                                                                       2          S           (158-202)   41
                                                                                                                                       2          Sw (203-247)            37
                                                                                                                                       2          W (24       a-292)      19
                                                                                                                                       2          RW (2       93-3 37)    10

                                                                                                                                       3          N           (338-22)    0
                                                                                                                                       3          ME          (23-67)     0
                                                                                                                                       3          E (68-112   )           35
                                                                                                                                       3          SE (113-157)            6
                                                                                                                                       3          S           (158-202)   10
                                                                                                                                       3          SW          (203-247)   27
                                                                                                                                       3          W (248-292)             19
                                                                                                                                       3          KW (2       93_33 7)    2

                                                                                                                                       4          N (33       1-22)       0
                                                                                                                                       4          ME (2       3_67        0
                                                                                                                                       4          z f68-112               0
                                                                                                                                       4          SE (        113-157)    0
                        Screen 2: Main Menu                                                                                            4          S (158-202)             0
                                                                                                                                       4          SW (203-247)            4
                                                                                                                                       4          W (24:-292))
                        The second screen (figure 3) lists four main options. We                                                       4          NW (2 3-337             0.
                        will describe the options briefly here then in the next
                        section, we will discuss Option 2 -- the most powerful                                                         5          N (338-22)              0
                        and versatile part of the program -- in detail.                                                                5          ME (23-67)              0
                                                                                                                                       5          R (         68-1121     0
                                                                                                                                       5          BE          (113-157)   0
                                                                                                                                       r,         S           f158-202)
                                                                                                                                       5          Sw (203-247)            0
                                                                                                                                       5          W 1248-292)             0
                        Option 1, PRINT OBSERVATION SUMMARY, sends                                                                     5          MW (293-337)            0
                        a summary to the printer. This summary lists the number                                                        CALK                               3
                        of observations for each wind-magnitude interval as well
                        as the total number of observations (figure 4) .                                                          TOTAL OBSERVATIONS - 375

                                                                                                            700

                      Option 2, VIEW WINDROSE, allows the user to view                                                              Figure 6. Windrose                   screen display under Option 2.
                      the windrose; to view a summary of the percentages; and
                      to plot the windrose, either alone or with the percentage
                      summary.                                                                                                   'Unm to CmTlmq

                                                                                                                                                                                        .30

                      Option 3, SELECT NEW FILE, enables the user to
                      select a new data file for analysis.

                      Option 4, QUIT, terminates the program and returns the
                      user to DOS.

                      Option 2: View WINDROSE
                      As mentioned above Option 2 allows the user to view
                      the windrose, to view the percentage summary, and to
                      plot the windrose either alone or @vith the percentage
                      summary.

                      When option 2 is selected, the user is first asked to enter
                      lease and well numbers and observation dates figure 5).
                      This information is not required; it is slEqply i2flyng
                                                                                              th          , i                       Figure 7. Percentage summary -- screen display under
                      information that, if enter@T, will appear in t e title me                                                                                                      -
                      of the percentage summary.                                                                                                                         Option 2.

                                    Figure 5. Screen display under Option 2.
                                                                                                                                          COMIATIVE WIND SPEED SUNKhRY FOR LEASE SAXPIZI-M WELL NO-         01
                                                                                                                                          BEGINNING - 00/00/88 ENDING- 00100/89
                                                                                                                                          NACNITUDS     1       2        3        4       5      TOTAL
                            PLEASE ENTER LEASE AND WELL INFORMATION.                                                                                                                                        MAGNITUDES
                                                                                                                                          NORTH         1.07    1.60     0.00     0.00    0.00   2.67
                                                                                                                                                                                                            1: D<S<-IO
                                                                                                                                          NORTHEAST     4.00    5.07     0.00     0.00    0.00   9.07
                                                                                                                                                                                                            2t 10<S<-21
                                                                                                                                          EAST          1.87    7.73     9.33     0.00    0.00   18.93
                        LEASE NUMBER: ?                                                                                                                                                                     3: 21<S<-33
                                                                                                                                          SOUTHEAST     2.13    3.47     1.60     0.00    Q.DO   7.20
                                                                                                                                                                                                            4: 33<S<-47
                        WELL NUMBER: ?                                                                                                    SOUTH         5.07    10.93    2.67     0.00    0.00   18.67
                                                                                                                                                                                                            5: S>47
                                                                                                                                          SOUTHWEST     6.40    9.87     7.20     1.07    O.CD   24.53
                        BEGINNING DATE OF OBSERVATIONS USED IN PLOTTING WIND ROSE - ?
                                                                                                                                          WEST          3.20    5.07     5.07     0.00    0.00   13.33

                        ENDING DATE OF OBSERVATIONS USED IN PLOTTING WIND ROSE - ?                                                        NORTHWEST     1.60    2.67     0.53     0.00    0.00   4.80

                                                                                                                                          TOTAL         25.33   46.40    26.40    1.07    0100   99.20

                                                                                                                                          PERCENT WINDS 99.20 PERCENT CALK           0.80 TOTAL  100.000
                                                                                                                                          DO YOU WISH TO VIEW THE WIND ROSE ArAIN (Y OR   NR I

                                                                                                                                                                                                                             of

                                                                                                                                 At this point, the program offers several options:
                                                                                                                                          The user can view the windrose once more, either
                      Next, the windrose is disDlayed on the screen (figure 6) .                                                          at the same size or enlarged.                               (An enlarged
                      In the windrose, the wind magnitude is represented by                                                               windrose is useful in some instances when the wind
                      the width of the boxes, and the percent occurrence by                                                               is uniformly distributed.)
                      the box length. With a color moffitor the boxes are also
                      differentiated by color. A circle scale is provided to
                      assist in evaluating the percentages shown on the
                      @iagram. The percent of 6din. observations is displayed                                                             The user can plot the windrose either with or
                      in numeric form in the center of the diagram. The cWm                                                               without a percentage summary. (figure 8 shows a
                      percentage is rounded to the nearest whole number.                                                                  windrose plotted With a. percentage summary.)
                                                                                                                                          The user can also add a title and/or narrative
                                                                                                                                          description.

                      Next the user presses the return key and the percentage
                      summary is displayed on the screen (figure 7).                                                                      The user can return to the main menu.

                                                                                                                        701

                                                                  WINDROSE WITH SUMMARY
                                         THIS PLOT WAS DEVELOPED USING DATA CONTAINED IN FILE
                                         SAMPLEI.PRN

                                                 tN                                 CUMULATIVE WIND SPEED SUMMARY             (PERCENT)

                                                                                    MAGNITUDE      1      2      3        4      5    TOTAL

                                                                                    NORTH        1.1     1.6     0.0      0.0   0.0     2.7
                                                                                    NORTHEAST    4.0     5.1     0.0      0.0   0.0     9.1
                                                 ix                                 EAST         1.9     7.7     9.3      0.0   0.0   18.9
                                                                                    SOUTHEAST    2.1     3.5     1.6      0.0   0.0     7.2
                                                                                    SOUTH        5.1     10.9    2.7      0.0   0.0   18.7
                                                                                    SOUTHWEST    6.4     9.9     7.2      1.1   0.0   24.5
                                                                                    WEST         3.2     5.1     5.1      0.0   0.0   0.3
                                                                                    NORTHWEST    1.6     2.7       .5     0.0   0.0     4.8
                                                                                    TOTAL        25.3    46.4    26.4     1.1   0.0

                                                                         n          WINDS        99.2
                                                                                    CALM           .8
                                                                                    TOTAL       100.0
                        0    10 20 30 40         50 60 70 80        90   100
                                      WIND SPEED SUMMARY

                                                                MAGNITUDE:CALM - S - 0 : I             O<S<-10 : 2        iO<S<-21
                                                                 (S-KNOTS)       3 - 21<S<-33        4 - 33<S<-47         5 - S>47
                             CALM 1 2 3 4 5

                                                                               Figure 8.
                                            Plot of windrose with percentage summary -- hardcopy output under Option 2.

                     CONCLUSION                                                         Copies of the program and source code are available
                                                                                        through the:
                     The WINDROSE pro am was developed to provide an                          Mineral's Management Service
                     easy method for anglyzing wind data submitted by
                     0 erators conducting @exp oration activities on the OCS.                 ATTN: Librarian
                       e r         summarizes the observations and provides
                     * sta istical. an is of the data in either a rose diagram                949 E. 36th Ave., Suite 110
                     * as a table su    ary. It will enhance the establishment
                     of the baseline for conditions which can be expected for                 Anchorage, AK 99508
                     operations conducted on the OCS. The program could
                     easily be modified, by an
                                                 ,y programmer faihiliar with
                     BASIC, to process other data requiring similar graphic
                     depiction.
                      r

                                                                                  702

                       MEASUREMENT OF LUMINANCE DISTRIBUTION ON THE SEA SURFACE
                                          FOR COMFORTABLE LIVING SPACE

                            Maki Enomoto, Toshimasa Kawanishi and Wataru Kato

                              Department of Oceanic Architecture & Engineering
                                 College of Science & Technology, Nihon University
                               7-24-1 Narashinodai Funabashi-City Chiba, Japan        274

                              ABSTRUCT
              The purpose of this report is to obtain a                             Sky Light

             basic data of the lighting and daylight
                                                                   Di t  nligh
             plan  to design the comfortable indoor

             lighting environment.

              The light incident    in a room through a
                                                                     Reflected Light
             window in a structure    has three kinds of                  of Sea Surface

             lights, direct sunlight, sky light, and
                                                                     Fig. 1 The Incident Light to The Structure
             reflected light of ground.                                     in Coast and Offshore

              A reflected light of sea surface to the                      1. INTRODUCTION

             structure in a coast or offshore zone is           T h e amount     of   i n d o o rd a y 1 i g h t

             bigger than the light of ground.                  illumination from  a sea surface is mainly

              The special consideration needs to be            influenced by a     sun.elevation,     a sea

             paid  for lighting and daylight plan to           surface condition, and other elements.

             design the comfortable living space in the         If the weather    is fine,    the incident

             ocean optical environment.                        light from a sea surface is great.
              We have seldom come up to these studie   SI.)2)   Fig.1 indicates the incident light of the

              In this report, we will discuss ab   out the     structure in coast and offshore.         Fig.2

             measurement of horizontal and vertical            indicates the view of reflected light of

             distribution of sea surface        luminance      sea surface.

             against a sun elevation.                           The way to treat reflected light of the

              To carry out our study, we developed a           sea surface would be difficult because of
             digital image processing system using a           the changes in the sea surface conditions.
             Charge Coupled Device(CCD) camera as a             Fig.3(a) indicates a reflected light of
                                                                   Di@. 0',Sunii.

             measurement system.                               the smooth sea surface. And       it  is     a

                                                               specular     reflection     which    reflects

                                                           703 United States Government work not protected by copyright-

                                                                                                                                                      Video Signal
                                                                                                                                                                                   Video Tape Recorder
                                                                                                                                             CCD Camara
                                                                                                                                                                          Video Signal

                                                                                                                                                    Video Signal                   Luminance Signal

                                                                                                                                                          Image    Processing Board
                                                            47-

                                  Fig. 2        The Reflected Ligbt of Sea surface                                                            Monitor Television                Personal Computer

                                                                                                                                         Fig. 4       Block Diagram of          Measurement System
                                                                           Direct Sunlight                                           Table. 1           Machine Parts a         .nd Specifications

                                                                                                                               CCD Camara             Camara Tube Sposification    Solid State Image Specificat-
                                                                                                                                                                                   ion (Type. of Interline)
                                                                                                                                                      Camera Tube Area             8.BXS.6[=j (size of 2/31n.)
                                                                                                                                                      Effective Picture Elements   766(10 x493(V)
                                                                                                                                                      SIN Ratio                    More Than 501dBI
                                   (a) Smooth Sea Surface                        Hough Sea Surface                                                    Gum Corrector                7

                                                                                                                               l6mm Standard Lens     Horizontal Angle of View     30.40*
                                    Fig. 3          The Condition of Sea Surface                                                                      Vertical Angle of View       23.18*
                          exceedingly                enormous              amount           of    light in                     image Processing Bo-   Resolution                   256 X 256
                                                                                                                               ard                    A/D Converter                6 Bits     64 Tone
                          regular reflectionofthe sunlight.                                                                                           Sampling ?ims                Image    Tim      1/60 [Sac]

                           Fig.3(b) indicates reflect condition on                                                            analog digital                           converter                  o f     i m a g e

                          the       rough          surface.                The         light             which                processing board "FDM-4"(PHOTORON-MADE).

                          reflects             diffusely               by the          trend of wave                           This converted image is analyzed by a

                          become much less than the amount of light                                                           personal computer "PC-98O1VM-21"(NEC-
                          by the specular reflectiorl@)                                                                       MADE).

                                            2. MEASUREMENT SYSTEM                                                                      3. CHARACTER AND CORRECTION OF

                           Fig.4 indicates the block diagram of                                                                                              EACH SYSTEM

                          measurement system and table.1 indicates                                                             The spectral responsivity of CCD camera

                          details of each equipment.                                                                          largelydiffers from the standardrelative

                           The luminance distribution appears as an                                                           luminous efficiency V(X)                                            w h i c h         is

                          illuminance distribution on image space on                                                          indicated in Fig.5.                           Therefore, we                      used

                          CCD camera "XC-77"(SONY-MADE) through the                                                           a        color correction                            filter               "No. 102"

                          16(mm) standard lens.                                                                               (KODAK-MADE) and                         an          infrared-rays-cut

                           A      v i d e o       s i g n a I         w h i c h        is directly                            -filter "IR."

                          p r o p o r t i o n a 1               to         an         illuminance                              As       a      r e s u 1 t ,          t h e r e        is      o n 1 y         5-9%

                          distribution is transmitted from a CCD                                                              difference between the results of this

                          camera.            And the video signal is converted                                                correction and the standard relative
                          F

                          into the luminance signal of 64 tone by                                                             luminous efficiency.

                                                                                                                     704

                                                              100                                                                                       o CCD
                                                                                                                                                        0 IR                                                                The condition of the weather and sea
                                                                                                                                                        A 102
                                               r              >                                                                                         A Corrected                                                     during the measurement was sunny, 1                                                                                                             cloud
                                                                                                                                                                     Value
                                                              or
                                               U                                                                                                            V(A)
                                               9:                                                                                                                                                                       amount, 2 Beaufort wind scale, 2 wind wave
                                               0              60
                                                              A
                                                                                                                                                                                                                        scale, and 0 swell scale.
                                               Id
                                                                                                                                                                                                                            It becomes cloudy and windy after 16:00
                                                              20
                                               U                                                                                                                                                                        and the swell scale increased to 1.

                                                                                                                                                                                                                            Table.2                                             indicates                       meteological                                                 a n d
                                                                     0           400                 Soo                  600                     700                800
                                                                                                    Wavelength(nm)
                                                                                                                                                                                                                        oceanographic conditions.
                                                              Fig.   5 Relative Luminous Efficienty curve
                                                              10                                                                                                                                                            The amount of a                                                   erosol in the air was

                                                                                                                                                                                                                        enormous; we could not even observe the

                                                              0
                                                                                                                                                                                                                        sun at sunset.

                                                              U

                                                              0.1                                                                                                                                                                                  5. METHODS OF MEASUREMENT
                                                              10,                        10,                       10,
                                                                                                      Luminance              lcd/m')                                                                                        We fixed the optic axis of lens at the
                                           Fig. 6                    Ralation of Luminance and Reference                                                                 Voltage
                                                                                                                                                                                                                        'height of human eyes and                                                                                  took photos of

                                        Fig.6                        shows                        t h e               relativity                                           of             the                           the reflected light of sea surface which

                                    incident luminance and the reference                                                                                                                                                varied from time to time.                                                                                  Also, we tried

                                    voltage on the imag                                                                  e processing board                                                                                                                                                                                        T*k'*
                                    according to the F-number of a camera.                                                                                                                              Table. 2 Meteorological and
                                        The                   1 i g h t                  source                         f o r              fig.6                      w a s                the                                                Oceanographic Conditions                                                             Tky. Bay
                                                                                                                                                                                                              F-1--ci,7.d7T..d 5-11                         1..T7 T,.d S;.
                                    lambertian                                     surface                          made                   out              of          a         white                       Ti.o A-1. F-. S..J. T...                                          T. 1.  xl"Btio*
                                                                                                                                                                                                                                    S-1.                     S.fl.              (11/S
                                                                                                                                                                                                              147-                            _T_
                                                                                                                                                                                                                        .00 2           1                                       10     54. 5,
                                    acrytic board lighted by an incandescen
                                                                                                                                                                                                              __7       I10 2       -1---          0_11
                                                                                                                                                                                                                        1   2           1          a                            I      so. 11,
                                    lamp                      from              the            rear.                       As            a      r e s u 1 t                       t 1,        i r             _.        3,0 2           1                                       .... ...
                                                                                                                                                                                                                        40  3           1                                       0 1    48. 6,
                                                                                                                                                                                                                        50  3           1                                       3.0    44. 6,
                                    relation                           was               proportional.                                                                                                        _I5._Q_0  _3                    -0                                1- 4. 1- -4 2. 6'                  0       to      20       30 K-      P-1fk 0C...
                                                                                                                                                                                                                        10  3                                                          TO 5 _-                   -
                                                                                                                                                                                                                        20  3                                                                                                               (a)
                                                                                                                                                                                                                                                          _L_ _LL                      38.-!'--
                                                                                                                                                                                                                            4           2     __0                               I_� 7_ _36. 5-
                                                              4. OUTLINE OF MEASUREMENT                                                                                                                                 41  3           2          1                            24. 1  34. 5,                                      Funabashi-Shi
                                                                                                                                                                                                                        11  1           1          1                            23.8   3:. S,                Tokyo L8:30.                          .  hrashi-Shi
                                                                                                                                                                                                              11A*          3           1          0                            23. 5  30. 3"                           19:00.
                                        We measured at a breakwater 5 meters                                                                                                                                            10  3           2     _0                                24. 0  29. 4*                          17:00
                                                                                                                                                                                                                                                                                                                       16:00                                  Hakuhari
                                                                                                                                                                                                                                                                                24. 0  26. 4,                          15:00
                                    above the sea level in the seashore of                                                                                                                                              30  a           2          1                            24. 1  24. 2,                                                                      Chiba-Shi
                                                                                                                                                                                                                        48  3       1   3          1                            34. S  22. 4'
                                                                                                                                                                                                                        so  3       1   3          j                            3"     20. r-                                                           1_@,
                                    Makuhari Beach,                                                          Narasino-City,                                                       Chiba                       I I "1        1           3          1                            3                                    Tokyo-Bay
                                                                                                                                                                                                                        10  3       __2_           1                            3S. a  16. V
                                                                                                                                                                                                                        20  3           3          1                            3
                                    Pref., Japan on May 18th, 1988.                                                                                                                                                     so  3           3          1                            3S. 2  12. 3*
                                                                                                                                                                                                                        40  3           3          1                            34. 6  10. 4  .
                                        We recorded the luminance for one minute                                                                                                                                        so  3           2          1                            35. 0  a. 5*
                                                                                                                                                                                                              18: 00        a           3          1                            34. a  5. 5,                                                Sodegaura
                                                                                                                                                                                                                        to  3           3     1    1                            34. 7         1.
                                    every ten minutes from-14:00 to 18:30.                                                                                                                                                                                 -                    . 4.-
                                                                                                                                                                                                              1         201 3       1                                           36     2.8
                                                                                                                                                                                                              1         30 13       1                    1 3 1 $.a                     0. 9*                                                (b)
                                        Fig.7(a) and (b) show the points where we
                                                                                                                                                                                                                                                                                                        Fig. 7                     Measurement Point
                                                                                                                                                                                                                                                                                                                                        IX"
                                                                                                                                                        A
                                                                                                                                                            c

                                                                                                                                                            v
                                                                                                                                                               0

                                                                                                                                                               0

                                    measured.

                                                                                                                                                                                                        .705

                     to catch the variation of the reflected                                                                o Sea Surface Luminance
                     light of sea surface at the very center of                                                             A Sky Light Luminance

                     the photo.           The image of the ref lected
                                                                                                            Z-
                                                                                                            a                     ..
                     light was recorded in video tapes.                                 We                                          A-AA,     0
                                                                                                            U
                     brought them back to our labolatory and                                                cu  l
                                                                                                            u

                     analyzed          t h e   i m a g e    w i t h    a    personal

                     computer.                                                                                    4
                                                                                                                10

                      While some of us o'perating the video
                     camera,         other scanned and obtained the                                             10
                                                                                                                    60*       40'      20*       0.
                     data of the maximum luminance                        of the sea
                                                                                                                            Sun Elevation
                     surface 5 degrees below horizon and the                                                 Fig. 8 Variation of Sea Surface       Luminance
                     sky 5 degrees above horizon.                                                                      and Sky Light Luminance

                                                                                                        u                                        o e
                                                                                                        a                                      6%
                                                                                                        M      o Makuhari                 o
                                                                                                                                         o
                              6. RESULT AND CONSIDERATION
                                                                                                               a Jagashima              o
                      We observed 2 trends from the measured                                                                          o             o
                                                                                                                                    o

                     data.      One is reflectance of                        the sea

                     surface by luminance meter.                        The others                      w                       o
                                                                                                        r
                                                                                                                                                     o
                                                                                                                              No
                     i s   luminance         distribution            of horizontal                                          oo
                                                                                                                         coo
                                                                                                        z            oo
                     and vertical on the sea surface.                                                               o                                   o
                     is variation area of sun glitter on the                                                   60*            40*          20*            0.
                                                                                                                            Sun Elevation (*)
                     sea surface.                                                                           Fig.9      Variation of Sea Surface
                                                                                                                        Reflectance

                             (1) VARIATION OF REFLECTANCE                                           Fig.9 we assign the value 1 for the

                      Fig.8 indicates variation of sea surface                                    maximum none dimentional reflectance in

                     and skylight luminance according to sun                                      Makuhari when the sun elevation is 18.3

                     elevation and fig.9 indicates variation of                                   degrees.         The      calculation          for fig.9          was

                     sea surface reflectance with variable sun                                    done under the assumption of                           observing
                     elevation in Makuhari Beach                     and J6gashima                smoothsea surface.
                     in Kanagawa Pref( Oct.25th, 1987.                          It was              From 54.5 degrees to 40.5 degrees sun
                     clear, 0 cloud amount, and 2 Beaufort Wind                                   e I e v a t i o n ,       t h e    n o n e     dimensional
                     Scale)."                                                                     reflectance increased gently because of

                      The value of sea surface reflectance is                                     the increase of the wave angle that makes

                     obtained from a division of maximum                                          regular ref lection                 to the measurement

                     luminance of sea surface by theoretical                                      point.
                     value of horizontal luminance of sunlight.                                     The reflectance rapidly increased after

                                                                                            706

                    36.5 degrees sun elevation -and reached the                                                                                            11.61 11.6'
                                                                                                                                                           Vertical Line@    9;
                    maximum at                   18.3 degrees and started

                                                                                                                                                           Horizontal        3;
                    to decrease suddenly after 14.3 degreees.                                                                                              I Line
                                                                                                                                                                  _10' 3'    0           16.
                                                                                                                                                           3'              -3-
                      As a result,                    we discovered that the                                                                                                                  3'
                                                                                                                                                                           -6
                    decrease reflectance at 36.5 degrees was                                                                                                               -9.
                                                                                                                                                                           -12*
                    caused by the increasing amount of cloud
                                                                                                                                                           (a)                 b
                    at the time of observation.                                                                                                            Fig. 10 Horizontal Line and Vertical Line

                      As a reference, the increased                                     scale of

                    cloud amount at 36.5                            degrees on table.2
                                                                                                                                                           6.5*
                    and the decreased skylightluminance at                                                                                                 Sun Elevation,[11 18.3 12.3*
                    same degrees on fig.8 can be used.                                                                                                     24.3*
                                                                                                                                                           30.3'
                      The maximum reflectance at sun                                    elevation                                                          36.5'

                                                                                                                                                           42.6*
                    o f      18.3        degrees             was       caused              by       the                                                    8- 48.6*
                                                                                                                                                           6-
                    occurance                of       the       strongest                r e g u 1 a r                                                     4-
                                                                                                                                                           2.
                                                                                                                                                           0
                    reflection toward the measurement point of                                                                                             5' 0. 5. 7.
                                                                                                                     r
                    5 meters above the sea                          level.                                                                                 Scanning Angle

                      The sudden decrease of the reflectance of
                                                                                                                  Fig. 11 Luminance Distribution on Horizontal Line
                    fig.9 is a resemblance                          of the sea surface

                    reflectance of C.Cox                            and W.H.Munk in 4
                                                                                                                                                             6.5'
                    Beaufort Wind Scale.                                                                                                                   12. 3*        1
                                                                                                                                                           18. 3*
                      Cox       and        Munk     5)  discovered                 t h a t      t h i s                                                    Sun ElevaItion P1 24.3'
                                                                                                                                                           30.3'
                    decrease was caused by the wave angle;                                                           a
                                                                                                                                                           36. 5'
                                                                                                                                                           42.6*
                    therefore, we assumed the same reason                                           for                                                    lo-
                                                                                                                                                           8- 48.6'
                    this decrease.                                                                                                                         6-
                                                                                                                                                           4-
                                                                                                                     U                                     2- Sky Horizon Sea
                      The maximum sea surface reflectance in                                                                                               o
                                                                                                                                                           6' 3' 0' -3o -6o -9o
                    J6gashima is 14.3 degrees sun elevation.                                                                                               Scanning Angle

                    But we could get the similar result from
                                                                                                                  @Fig. 12                                 Luminance Distribution on Vertical Line
                    these two different measurement.
                                                                                                                  degrees                                  below horizon and the vertical

                               (2) VARIATION OF LUMINANCE                                                         line                                     appears at the center of the image,

                                                 DISTRIBUTION                                                     and fig.10(b) indicates the co-ordinates

                      In order to obtain the graphical data for                                                   on the horizontal and vertical line.

                    luminance distribution, we established two                                                       We processed the image into the graphic

                    lines          on     the        i m a g e      as      indicated                in           data recorded of every hour from 14:00.

                    fig.10(a) the horizontal line appears at 3                                                       Fig.11 indecates the horizontal                                         line,
                                                                                                                                                           Elaat.-n[-]
                                                                                                                                                           18
                                                                                                                                                           24.3 .1
                                                                                                                                                           2

                                                                                                                                                           3
                                                                                                                                                           n' @@l 2.
                                                                                                                                                           24.

                                                                                                                                                           3
                                                                                                                                                           36.A5
                                                                                                                                                           6

                                                                                                                                                           303
                                                                                                                                                           _3 .5
                                                                                                                                                           2 6

                                                                                                                                                           486

                                                                                                                                                           55

                                                                                                                                                           SyKorionSea

                                                                                                          707

                       fig.12 indicates the vertical line..                                             and started to decrease suddenly after

                        In both figures,                   the horizontal axis                          14.3 degrees.

                       indicates scanning angle of camera, the                                          2) At 30.3 degrees sun elevation, the high

                       vertical one indicates luminance, and the                                        luminance surface grew and expanded to 10

                       other one is sun elevation.                                                      degrees of scanning angle on the luminance

                        At     54.5 degrees               sun elevation,                  t h e         distribution of the horizontal line.

                       luminance          is constant and sea surface                                   3) At 18.3 degrees, high luminance surface

                       luminance            is     s m a 11 e r     than        s k y 1 i g h t         m o v e s      onshore            on      t h e      luminance

                       luminance.                                                                       distribution of the vertical line.

                        At 42.6 degrees sun elevation, high

                       luminance points increased a                                 1 i t t 1 e

                       because of the increased amount.of wave

                       angle which can reflect the sunlight to                                                                     REFERENCES
                       the measurement point for the maximum.                                           I)ARCHITECTURAL                   INSTITUTE           OF     J A P A N
                        At     36.5 degrees               sun      e 1 e v a t i o n ,    s e a         Architectural                 D e s i g n      D a t a     B o o k      1
                       surface luminance is bigger than skylight                                        (Environmental Section). Maruzen, 1985.
                       luminance in the figure of vertical line.                                        2 ) M a s a o   I n u i     a n d    Y o s h i k i     Nakamura:
                        And      at 30.3        degrees         the high luminance                      Luminance          Distribution              in Natural and
                       surface, in the figure of horizontal line,                                       A r t i f i c i a 1     Landscapes.               Journal             of
                       which is more than 4.0 X 10' [cd/m' I grew                                       Architecture, Planning Environmental

                       and expanded to 10                     degrees ofscanning                        Engineering. No.384, p36 - 43, Feb,                          1987.
                       angle.                                                                           3)Motoaki Kishino: Some Ploblems of Light

                        At 18.3 degrees, high luminance surf ace                                        near Sea Surface. Marine Science/Monthly.

                       moves onshore in the fig.12 and luminance                                        Vol.4, No.9, p 11 - 16, Sep, 1972.

                       is maximum value for both fig.11 and 12.                                         4)Maki Enomoto:                   A Basic Studies on

                        The width of high luminance surface is                                          Measurement of Optical Environment in

                       reduced to a half of the high luminance                                          Coas@al and Offshore Structure. Graduation

                       surface.           At 6.5 degrees, luminance is                                  Thesis of Dept of Oceanic Architecture &

                       suddenly decreased and the width of high                                         Engineering                C o 11 e g e      of      S c i e n c e      &

                       luminance surface.is also reduced.                                               Technology, Nihon University, Feb, 1986.

                                            7. CONCLUTION                                               5)Cbx and Munk:                 Statistics of the sea
                       1)    The       v a r i a t i o n    of     reflectance               is         surface derived from sun glittre. Journal
                       increased after 36.5 degrees sun elevation                                       of Marine Reseach, 13-2, p198                          227, 1958.

                       and reached the maximum at 18.3 degrees

                                                                                                  708

                                           USE OF A MACRO-HYBRID CAMERA AT NATIONAL GEOGRAPHIC

                                           EMORY KRISTOF, JOSEPH STANCAMPLANO & ALVIN CHANDLER

                                                     NATIONAL GEOGRAPHIC SOCIETY

                                    ABSTRACT                                   The most important decision was which SLR to
                                                                          chop up. For reasons of size, retained structural
                  Still cameras and television cameras are used           integrity after alterations, and its mechanical
            separately and in concert to produce underwater               shutter, we chose a Nikon FM2.         We retained the
            images.    It is generally accepted that pictures             shutter, the mirror box, the penta-prism, and the
            done on film still cameras are sharper and have               lens mount.    What was left established the inter-
            higher resolution that those produced with video              nal diameter of the housing which is five inches.
            cameras.    The video cameras are capable of much             The macro-lens is a Nikon auto-focus 55mm.            The
            greater sensitivity to light and most importantly             auto-focus feature is not used, but the internal
            feed back information at a real-time rate.                    focusing of the lens keeps the changes to the
                                                                          length of the lens to a minimum.        Since the lens
                  There   are   several    commercially    available      is looking through flat glass the one third magni-
            cameras that have the film and the electronic                 fication rule in water comes into play and the
            imager sharing the same optics.        This is usually        lens is equal to a 73mm lens in air.
            accomplished by use of a mirror that moves back
            and forth between the film and imager.           Cameras           The remains of the Nikon camera body and the
            have been built that have a video camera looking              lens were mated to a Benthos 378 camera chassis
            through the optics of a 35mm SLR.       The Geographic        and film drive.    The film is handled normally in a
            designed and built its own hybrid camera along                Benthos 50 foot     400 exposure cassette.       A Sony
            these lines to accomplish high quality remotely               XC-77 CCD camera with a 16mm relay lens focuses
            done macro-photography from submersibles and ROVs.            on the groundglass through the Nikon eyepiece.
            The camera has been successfully used in the field            The Sony sees about two-thirds of the total 35mm
            from both types of platforms.       The paper wi 11 be        frame.   The focusing is accomplished remotely with
            both on the design and construction of our camera             a motor.    The first edition of the camera didn't
            and the techniques employed during its use.                   have remote     aperture setting.       Color Negative
                                                                          film was relied upon to handle differences in
                                                                          exposure.

                  Some of the most striking and informative                    For its initial use on the Cayman Wall , the
            underwater still pictures produced by scuba diving            camera was first mounted on the RSL Perry PC 1802.
            photographers, such as David Doubilet, have been              A pair of 300 watt second strobes provided illumi-
            made with macro-lenses and SLR cameras in under-              nation.    The aperture was preset at f1l and the
            water housings.     Most of the deep water (beyond            film used was Kodak Vericolor         160 ASA.       When
            scuba   depth)    still   photographs    produced     for     placed on a DOE Phantom a single 100 watt second
            National   Geographic    are   from    cameras   mounted      strobe and a setting of f5.6 were     used.
            externally on submersibles and ROVS.         These are
            special 35mm cameras, such as the Benthos, with                    Shooting pictures from the submersible was
            wide angle optics placed in tube-shaped deep sea              easier than from the ROV, as could be expected.
            housings.   Focus and aperture settings have to be            The biggest problems with shooting from the ROV
            preset.   In most cases an independent video camera           are coordinating the wide angle television view
            with   the  same    angle  of   view   is  used   as    a     with the magnified macro picture, and the magnifi-
            11viewfinder."   This is a simple approach to pho-            cation of the ROV's motion by the macro camera.
            tography that is adequate for many subjects.                  The picture goes in and out focus very quickly
                                                                          if the ROV is being flown in mid-water and is not
                  Macro -ph otogr aphy is best done with a SLR.           sitting on something or otherwise braced.       I found
            The design objectives for our camera were to take             it was best to pre-focus the camera and when the
            the best features of     a good SLR and macro-lens,           ROV swam into the proper focus to shoot it--fast.
            combine them with the extended film capacity and
            drive of an existing     deep sea camera, install a                The mod II camera has a remotely adjustable
            small TV camera with a relay lens to look thru the            aperture control and a second slaved strobe light
            shooti'ng lens, and package the results in as small           that can be placed in the manipulator claw.          This
            a pressure-proof housing as possible.        Since the        makes   possible a more controlled and moveable
            camera was to be used part of the time on our ROV             light.    These improvements are to be tried out
            the small size was especially critical.                       this summer in the Monterey Canyon.      The camera

                                                   CH2585-8188/0000- 709   $1 @1988 IEEE

                 has already proved   to  be  a  success  for   the
                 National Geographic and the first picture will be
                 published in the November 1988 Magazine.     Other
                 scientists and industrial users might find this
                 type of special camera to be a good tool.
                                                                                    40,

                  Stalked crinoid at 750 feet (photo from sub).

                                                                    710

                                                                 UNDERWATER HYBRID 35mm/TV CAMERA
                 U                                                                               NIKON FE-@ HIRROR BOX
                                                                                    CCD CAMERA

                                                                                                                              35irn, 2.8 AF NIKKOR

                                                                           SHUTM
                                    BENTHOS 400 ET CASSET                  SPEED CONT.

                                                                                                                              APE

                      SONY XC37 VIDEO CX-fM POWER SUPPLY

                  Diagram of macro-hybrid camera.

                                                          NOW *0                                    4MM

                                           7
                                                                                     wFFM 'k

                  Macro-hybrid camera mounted         on RSL Perry 1802,      overtop    a pair of video cameras providing stereo.
                            Emory             is pictured
                  Author,           Kristof                  through bubble.

                                                                                    711

                                                                                            t

                (Above): Brain coral in 200 feet of water and (below) close-up of brain coral  (both photos from ROV).

                                                                    712

                                                           3-D AS AN UNDERWATER TObL

                                               EMORY KRISTOF & AL;VIN CHANDLER, DR. WILLIAM HAMNER

                                                       NATIONAL GEOGRAPHIC SOCIETY, UCLA

                       The National Geographic Society has used its            video system, the number of fields per second is
                 first set of 3-D video cameras to produce tapes of            doubled.       We achieve this by doubling the ver-
                 deep sea creatures from down further that a mile.             tical scanning rate, thereby producing 120 fields
                 We are presently building a second miniaturized               instead of 60 fields per second.       Thus the number
                 set of cameras to be mounted on ROVs.         The tapes       of lines per field is halved, but each eye sees a
                 are being introduced to the scientific community              proper twofold interlaced image.         When displayed
                 and    used   by   the    Geographic   in    educational      on a suitably prepared 120 HZ monitor, the two
                 displays. The StereoGraphic system that we employ             images are displayed in sequence."
                 will display both video or computer CAD material.
                 We are using this second ability to produce 3-D                     One of the real advantages of this system is
                 video stereo of a wire model of a shipwreck sur-              that  the signal can be recorded on an unmodified
                 veyed in situ with a SHAPPS system.              We are       NTSC  VCR.   A major improvement was the introduc-
                 looking   at   taking   this   data  and     producing   a    tion   of   LCD   technology   to   replace   the    PLZT
                 hologram. The StereoGraphic system is the first to            goggles.     This made possible lower cost, lower
                 allow the user to electronically set the point of             voltage viewing glasses with much high.er light
                 convergence between the two cameras.         This means       transmission rates.     Large LCD polarized switching
                 the system can be used like a rangefinder to                  plates are now available to place in front of
                 instantly establish the distance to an object and             monitors    and    video   projectors.     This    allows
                 then its dimensions.     The Geographic is working to         multiple viewers     to experience the 3-D effect
                 computerize this ability.      William Hamner has had         wearing only inexpensive polarized glasses.
                 a 3-D motion analysis program created for a Sun
                 work station.     He is now able to pull off speed                  The Universal Camera Controller or UCC will
                 and vector information from 3-D video tape.           3-D     process the video from any pair of genlockable
                 has many applications in the underwater world and             cameras.   A feature of the UCC I found really use-
                 it is a technology whose time has finally arrived.            ful was   the ability to electronically align and
                 The Geographic is in the forefront of its uses.               converge  the cameras at any time.       Where the con-
                                                                               vergence point is placed in a 3-0 image can be
                                                                               very important to the quality and the perception
                      The   National    Geographic   Society has      been     of that image.        This  feature also allows the
                 experimenting with 3-D video for five        years.   The     system to function     like an optical rangefinder,
                 initial reason was to better control         manipulator      making possible instant depth and size measure-
                 functions on its ROV.           For this     purpose we       ments with a coupled PC.
                 obtained a mirror-stereopticon dual          TV viewing
                 hood from ARD Corp.     This granted the     operator of            The Geographic was    impressed enough with the
                 the ROV real-time 3-0 viewing from a         pair of JVC      StereoGraphic system to     purchase it.    The initial
                 nine inch monitors.       We were experimenting with          use was to produce first-time 3-D video of deep
                 the hood and different pairs        of cameras in the         sea animals from depths down to greater than a
                 lab, when the decision was made to pursue a system            mile.    We have been baiting these animals into
                 that would allow us to record       and present stereo        manned   submersibles    during   a multi-year      study
                 video material to the public.                                 known as the BEEBE PROJECT.      In the summer of 1988
                                                                               the    StereoGraphic     UCC,    the     NTSC    Display
                      Over the last decade we followed the develop-            Controller, a 13" 120 HZ monitor, two LCD shut-
                 ment   of    time-multiplexed     stereoscopic      video     tered glasses and a Sony BVW-25 Betacam VCR were
                 systems utilizing PLZT ceramic goggles.         Typified      installed     in     the    International     Underwater
                 by the Honeywell system, video fields alternated              Contractor submersible PISCES VI.        Mounted exter-
                 between "left eye" and "right eye" information.               nally on a pan and tilt were a pair of Sony single
                 The resulting picture flickered because there were            chip CCD cameras with 4.8mm lenses. The 4,500 psi
                 only 30 fields per second per eye.           The picture      rated camera housings were built by Deep Sea Power
                 could only be viewed by looking at the monitor                and Light.
                 through an expensive pair of PLZT goggles that
                 alternately shuttered each eye.                                    The location for the dives was eight miles
                                                                               N.W. of Bermuda.       Many animals, including dif-
                      The further development of     the technology was        ferent species of deep water sharks, were seen for
                 undertaken by Lenny Lipton and      Lhary Meyer of the        the first time in their natural habitat at the
                 StereoGraphics Corp. "In the StereoDimensional                feeding stations. The Project scientists all

                                                         CH2585-8/88/0000. 713  $1 @1988 IEEE

                 like the 3-D video tapes and felt they were reaso-           of the StereoGraphic image.      You feel that you are
                 nable simulations of the actual diving experience.           looking with your own eyes through a face mask.
                 They are now looking at ways to pull additional              This is the beginning of true visual telepresence.
                 data from the tapes. Animal counts will be easier
                 to perform from 3-D video tapes and determination                  To retain the quality of the original, we
                 of sizes will be possible.                                   have been recording the video on two time code
                                                                              linked    Sony   BVW-35   Betacam   recorders.        The
                       The Geographic decided to build a 3-D theater          finished show will be presented by two computer
                 for our museum to show the results of the Project.           controlled laser-disc players.        Chris has built
                 It was patterned to look like an underwater habi-            electronic convergence control into his viewing
                 tat,    with   five   viewing    "portholes."       Each     system.    He has demonstrated the ability to use
                 "porthole" contained a 13" 1000 x 1000 graphic               this function as a rangefinder.         Coupled with a
                 monitor    set   in  2011  from   the   glass   of    the    video measuring system he has sized objects remo-
                 "porthole." The glass is a special 5 x 7 inch LCO            tely.   A protype system demonstrating a completely
                 shutter supplied by StereoGraphics.         The viewer       integrated 3-D video system including cameras,
                 looks through the port and sees the three minute             viewers, recorders, and measuring instrumentation
                 show    in  3-D   without   having   to  wear    special     will be shown at OCEANS 88.
                 glasses.    The video tape is converted to RGB and
                 line-doubled to make up for the reduced vertical                   After establishing the distance and size of a
                 resolution.     We have been very pleased with the           desired object, all that is left to measure is the
                 performance    of   the  equipment    which   has    been    speed and vector of the object if it is relevant.
                 trouble free since we turned it on in January.               Dr. William Hamner had software created for a Sun
                 The public has liked the show.                               work station by Motion Analysis of Santa Rosa,
                                                                              California that allows him to take that infor-
                       Presently we are using a    pair of finger sized       mation from his dual camera 3-D system.        This was
                 Panasonic TV cameras mounted     behind the dome of a        created as part of Bill"s NSF funded study of the
                 W II MiniRover by Chris Nicholson of Deep Sea                schooling of fish.
                 Systems.     This work in Monterey Canyon is our
                 first blue water trial of 3-D video on a ROV.                      The Geographic has plans to do a high resolu-
                 Chris has built a dual nine inch monitor viewing             tion acoustic survey of a shipwreck that we can
                 system     that   uses    a   half-silvered      mirror,     present as 3-D computer graphic information in our
                 polarizing filters on both monitors and polarized            museum theater.     3-D video has many applications
                 glasses.    This is an old idea, but as optimized by         in the underwater world, and it is a technology
                 Chris, and taking advantage of the new small CCD             whose time has finally arrived.      The Geographic is
                 cameras the results have been impressive.             The    in the forefront of its uses.
                 resolution of the image is more     than double that

                                                                                                              Stereo pair of deep
                                                                                                              sea video cameras
                                                                         Fit,, wow"
                                                                                                              mounted on the
                                                                                                              front of PISCES VI, a
                                                                                                              35mm still camera
                                                                                                              is mounted
                                                                                                              underneath.

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                                                                                          Ce"

               (Top): Emory Kristof operating 3-D video system a mile deep in the Atlantic inside PISCES VI. Viewing
               is through LCD shuttered glasses. (Bottom'left): Rack mounted StereoGraphic system is seen over Dr.
               Eugenie Clark inside of PISCES VI. (Bottom right): Scenes from the 3-D show include two types of deep
               sea sharks and several large crabs at the bait cage at a depth of 3,000 feet.

                                                                 715

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                                    Drawing of exterior               of Geographic           3-D theater (top), and drawing of interior of Geographic                                           3-D
                                    theater (bottom).

                                                                                                                   716

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                        National Geographic 3-D System
                                  on IUC PISCES VI

                                                                                                                                  "41

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                                                          Universal Camara Controller

                                                             SONY BVW-25
                                                             Betacarn VCR
                                                             (unmodified)

                             4.8inm lenibs
                                                                                      Cut-away of Geographic 3-D theater (top). Many
                                                                                      eels eating the bait at a depth of 5,100 feet
                                                         NISC Display Controller
                                                                                      (right).

                          SONY CCD
                          Genlockable cameras
                           (unmodified)

                           Sync Generator                  13" 120 HZ Monitor

                                                   Viewingglasw

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                  Emory Kristof
                 graphic 3      inside Ceo-
                           -D theater viewing
                 ,show thr.    LCD shuttered
                  .P.rthoj_e,@gh
                 in front    (top) and Emory
                           Of Of Geographic
                 37D theater (right).

                                                               718

                                              DATE DUE

                                        3 6668 14106 1152

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