[House Hearing, 110 Congress]
[From the U.S. Government Publishing Office]
NEAR-EARTH OBJECTS (NEOS)--STATUS
OF THE SURVEY PROGRAM AND REVIEW
OF NASA'S 2007 REPORT TO CONGRESS
=======================================================================
HEARING
BEFORE THE
SUBCOMMITTEE ON SPACE AND AERONAUTICS
COMMITTEE ON SCIENCE AND TECHNOLOGY
HOUSE OF REPRESENTATIVES
ONE HUNDRED TENTH CONGRESS
FIRST SESSION
__________
NOVEMBER 8, 2007
__________
Serial No. 110-72
__________
Printed for the use of the Committee on Science and Technology
Available via the World Wide Web: http://www.house.gov/science
______
U.S. GOVERNMENT PRINTING OFFICE
38-057 WASHINGTON : 2008
_____________________________________________________________________________
For Sale by the Superintendent of Documents, U.S. Government Printing Office
Internet: bookstore.gpo.gov Phone: toll free (866) 512-1800; (202) 512�091800
Fax: (202) 512�092104 Mail: Stop IDCC, Washington, DC 20402�090001
COMMITTEE ON SCIENCE AND TECHNOLOGY
HON. BART GORDON, Tennessee, Chairman
JERRY F. COSTELLO, Illinois RALPH M. HALL, Texas
EDDIE BERNICE JOHNSON, Texas F. JAMES SENSENBRENNER JR.,
LYNN C. WOOLSEY, California Wisconsin
MARK UDALL, Colorado LAMAR S. SMITH, Texas
DAVID WU, Oregon DANA ROHRABACHER, California
BRIAN BAIRD, Washington ROSCOE G. BARTLETT, Maryland
BRAD MILLER, North Carolina VERNON J. EHLERS, Michigan
DANIEL LIPINSKI, Illinois FRANK D. LUCAS, Oklahoma
NICK LAMPSON, Texas JUDY BIGGERT, Illinois
GABRIELLE GIFFORDS, Arizona W. TODD AKIN, Missouri
JERRY MCNERNEY, California JO BONNER, Alabama
LAURA RICHARDSON, California TOM FEENEY, Florida
PAUL KANJORSKI, Pennsylvania RANDY NEUGEBAUER, Texas
DARLENE HOOLEY, Oregon BOB INGLIS, South Carolina
STEVEN R. ROTHMAN, New Jersey DAVID G. REICHERT, Washington
JIM MATHESON, Utah MICHAEL T. MCCAUL, Texas
MIKE ROSS, Arkansas MARIO DIAZ-BALART, Florida
BEN CHANDLER, Kentucky PHIL GINGREY, Georgia
RUSS CARNAHAN, Missouri BRIAN P. BILBRAY, California
CHARLIE MELANCON, Louisiana ADRIAN SMITH, Nebraska
BARON P. HILL, Indiana PAUL C. BROUN, Georgia
HARRY E. MITCHELL, Arizona
CHARLES A. WILSON, Ohio
------
Subcommittee on Space and Aeronautics
HON. MARK UDALL, Colorado, Chairman
DAVID WU, Oregon TOM FEENEY, Florida
NICK LAMPSON, Texas DANA ROHRABACHER, California
STEVEN R. ROTHMAN, New Jersey FRANK D. LUCAS, Oklahoma
MIKE ROSS, Arizona JO BONNER, Alabama
BEN CHANDLER, Kentucky MICHAEL T. MCCAUL, Texas
CHARLIE MELANCON, Louisiana
BART GORDON, Tennessee RALPH M. HALL, Texas
RICHARD OBERMANN Subcommittee Staff Director
PAM WHITNEY Democratic Professional Staff Member
KEN MONROE Republican Professional Staff Member
ED FEDDEMAN Republican Professional Staff Member
DEVIN BRYANT Research Assistant
C O N T E N T S
November 8, 2007
Page
Witness List..................................................... 2
Hearing Charter.................................................. 3
Opening Statements
Statement by Representative Mark Udall, Chairman, Subcommittee on
Space and Aeronautics, Committee on Science and Technology,
U.S. House of Representatives.................................. 11
Written Statement............................................ 12
Statement by Representative Tom Feeney, Ranking Minority Member,
Subcommittee on Space and Aeronautics, Committee on Science and
Technology, U.S. House of Representatives...................... 13
Written Statement............................................ 15
Panel 1:
Representative Luis Fortuno, Resident Commissioner, Puerto Rico
Oral Statement............................................... 16
Written Statement............................................ 17
Discussion
Impact of Shutting Down Arecibo................................ 18
George Brown................................................... 19
Importance of Arecibo With Regard to Cost...................... 20
Visiting Arecibo............................................... 21
Panel 2:
Dr. James L. Green, Director, Planetary Science Division, Science
Mission Directorate, National Aeronautics and Space
Administration (NASA)
Oral Statement............................................... 22
Written Statement............................................ 24
Biography.................................................... 27
Dr. Scott Pace, Associate Administrator, Program Analysis and
Evaluation, National Aeronautics and Space Administration
(NASA)
Oral Statement............................................... 28
Written Statement............................................ 30
Biography.................................................... 34
Dr. Donald K. Yeomans, Manager, Near-Earth Object Program Office,
Jet Propulsion Laboratory
Oral Statement............................................... 34
Written Statement............................................ 37
Biography.................................................... 40
Dr. Donald B. Campbell, Professor of Astronomy, Cornell
University; Former Director, Arecibo Observatory
Oral Statement............................................... 40
Written Statement............................................ 42
Dr. J. Anthony Tyson, Professor of Physics, University of
California, Davis; Director, Large Synoptic Survey Telescope
Project
Oral Statement............................................... 47
Written Statement............................................ 48
Biography.................................................... 54
Mr. Russell ``Rusty'' L. Schweickart, Chairman and Founder, B612
Foundation
Oral Statement............................................... 54
Written Statement............................................ 57
Biography.................................................... 94
Discussion
Importance of Surveying Objects Larger Than 140m............... 95
Risk of Changing the Project Timeline.......................... 95
Non-U.S. NEO Characterization.................................. 96
Increasing International NEO Collaboration..................... 96
Public Safety.................................................. 97
NEO Deflection Technology...................................... 98
Deflection of NEOs into Keyholes............................... 99
More on International Collaboration............................ 100
Probability of a 10km NEO Hitting Earth in the Near Future..... 100
Apophis NEO.................................................... 101
Understanding the Threat Posed By NEOs......................... 101
Future Responsibility.......................................... 102
Potential NASA Partnerships.................................... 103
NASA Funding NEO Partnerships.................................. 103
Using LSST for NEO Detection................................... 105
Radar Versus Optical NEO Detection............................. 106
Importance of Arecibo Radar.................................... 106
Radius of NEO Surveys.......................................... 106
Ramifications of an Asteroid Hitting Earth..................... 107
NEO Survey Objectives.......................................... 109
Planetary Defense Responsibilities............................. 109
Goldstone Antenna Upgrades..................................... 111
Future Steps in NEO Detection and Deflection................... 112
Orbital Determination.......................................... 112
More on Detection and Deflection............................... 113
Importance of NEO Characterization............................. 114
Appendix 1: Answers to Post-Hearing Questions
Dr. James L. Green, Director, Planetary Science Division, Science
Mission Directorate, National Aeronautics and Space
Administration (NASA).......................................... 118
Dr. Scott Pace, Associate Administrator, Program Analysis and
Evaluation, National Aeronautics and Space Administration
(NASA)......................................................... 127
Dr. Donald K. Yeomans, Manager, Near-Earth Object Program Office,
Jet Propulsion Laboratory...................................... 134
Dr. Donald B. Campbell, Professor of Astronomy, Cornell
University; Former Director, Arecibo Observatory............... 142
Dr. J. Anthony Tyson, Professor of Physics, University of
California, Davis; Director, Large Synoptic Survey Telescope
Project........................................................ 146
Mr. Russell ``Rusty'' L. Schweickart, Chairman and Founder, B612
Foundation..................................................... 151
Appendix 2: Additional Material for the Record
NASA Rebuttal to remarks made by Mr. Schweickart during the
November 8, 2007 hearing regarding Near-Earth Objects.......... 162
Statement of The Planetary Society in Support of Planetary Radar
at the Arecibo Observatory..................................... 163
Letter to The Honorable Dana Rohrabacher from John W. Meredith,
President, IEEE-USA, dated 08 November 2007.................... 164
NEAR-EARTH OBJECTS (NEOS)--STATUS OF THE SURVEY PROGRAM AND REVIEW OF
NASA'S 2007 REPORT TO CONGRESS
----------
THURSDAY, NOVEMBER 8, 2007
House of Representatives,
Subcommittee on Space and Aeronautics,
Committee on Science and Technology,
Washington, DC.
The Subcommittee met, pursuant to call, at 10:07 a.m., in
Room 2318 of the Rayburn House Office Building, Hon. Mark Udall
[Chairman of the Subcommittee] presiding.
hearing charter
SUBCOMMITTEE ON SPACE AND AERONAUTICS
COMMITTEE ON SCIENCE AND TECHNOLOGY
U.S. HOUSE OF REPRESENTATIVES
Near-Earth Objects (NEOs)--Status
of the Survey Program and Review
of NASA's 2007 Report to Congress
thursday, november 8, 2007
10:00 a.m.-12:00 p.m.
2318 rayburn house office building
Purpose
On Thursday, November 8, 2007 at 10:00 a.m., the House Committee on
Science and Technology's Subcommittee on Space and Aeronautics will
hold a hearing to examine the status of NASA's Near-Earth Object survey
program, review the findings and recommendations of NASA's report to
Congress, Near-Earth Object Survey and Deflection Analysis of
Alternatives, and to assess NASA's plans for complying with the
requirements of Section 321 of the NASA Authorization Act of 2005.
Witnesses
Panel 1
The Honorable Luis G. Fortuno, Resident Commissioner,
Puerto Rico
Panel 2
Dr. James Green, Science Mission Directorate, NASA
Dr. Scott Pace, Program Analysis and Evaluation, NASA
Dr. Donald K. Yeomans, Jet Propulsion Laboratory
Dr. Donald B. Campbell, Cornell University
Dr. J. Anthony Tyson, University of California, Davis
Mr. Russell ``Rusty'' Schweickart, B612 Foundation
Potential Issues
What is the current status of NASA's Near-Earth
Object (NEO) search program, and how urgent is the need to move
ahead with the expanded search that was directed in the 2005
NASA Authorization Act? Is the timeline for achieving the goal
appropriate or would changes in the ``deadline'' provide
benefits in terms of technical approaches or costs?
What are the most important priorities to address
relative to detecting, characterizing, and developing the means
to deflect NEOs?
NASA submitted a 2007 report to Congress on NEO
search and deflection options, but the report doesn't provide a
recommended option, as required in the 2005 NASA Authorization
Act. What approach does NASA recommend for complying with the
legislated mandate and what steps has NASA taken to begin
implementing any of the options identified in the report?
NASA's report to Congress mentions search options
that would rely on planned ground-based telescopes that have
been proposed for development under the auspices of other
agencies. What role, if any, should NASA play in supporting the
NEO-related operations of those telescopes? What alternatives
exist if those assets are not funded and developed?
Planetary radar facilities have been cited as
critical for providing more precise orbital determinations of
potentially hazardous NEOs. However, the two radar facilities
currently being used to obtain data on NEOs [Arecibo and
Goldstone] may not be available in the future. What are the
implications should existing planetary radar facilities become
unavailable?
A NEO object, Apophis, has been identified and could
pass as close as 23,100 kilometers from the Earth's surface in
2029 and return again for a close approach in 2036. What threat
does this object pose in terms of a potential impact with
Earth, and what is needed to improve our understanding of the
threat?
How much time would be required to prepare a
mitigation approach if a hazardous object were discovered to be
on a collision course with Earth? How much time would likely be
available?
How well understood are the potential approaches to
deflecting asteroids? What is the confidence level in the
technologies that would be required? What information is needed
to assess the various approaches, and how will decisions be
made on which mitigation strategy to take?
What is the degree of international involvement in
searching for, characterizing, and studying deflection options
for NEOs? What steps, if any, has NASA taken on potential
collaboration or coordination of NEO-related initiatives?
How will policy and legal issues involved in
addressing NEOs--e.g., when and how to warn the public and
whether to use nuclear explosives to deflect an asteroid--be
handled on national and international levels? What steps have
NASA and other federal agencies taken to date to address such
issues?
Background
Astronomers estimate that millions of asteroids, comets,
meteoroids, and other cosmic debris orbit within the vicinity of Earth
and the Sun. The Earth is continually bombarded by these remnants from
the formation of the solar system. Small objects ranging from the size
of a dust particle up to a size of about 50 meters in diameter do not
pose impact threats to Earth, because they burn up and disintegrate
upon entry to the Earth's atmosphere. However, larger objects pose
potentially catastrophic threats because they would not disintegrate
before impacting the Earth. Near-Earth Objects (NEOs) are defined as
asteroids and comets whose trajectories bring them within 45 million
kilometers (km) of the Earth. NEOs larger than about 140 meters, whose
orbits about the Sun bring them within 7.5 million km of the Earth's
orbit, are classified as potentially hazardous objects (PHOs). Most of
these objects are asteroids. According to NASA, there are currently 900
known Potentially Hazardous Asteroids (PHAs). NASA scientists estimate
that the population of PHOs is about 20,000 objects.
The literature on NEOs is not entirely consistent on the threats
posed by various sizes of objects. Information from NASA's Near-Earth
Object Program webpage [http://neo.jpl.nasa.gov] and other sources
indicates the following:
Objects larger than 50 meters can survive entry
through the Earth's atmosphere, and could cause local disasters
or events such as tsunamis upon impact. Estimates of the
frequency of impacts of objects of this size range from once
every 100 years to once every 500 years.
Objects larger than one km in diameter that impact
Earth would cause disasters on a global scale, and ``the impact
debris would spread throughout the Earth's atmosphere so that
plant life would suffer from acid rain, partial blocking of
sunlight, and from the firestorms resulting from heated impact
debris raining back down upon the Earth's surface.'' Estimates
of the frequency of these range from once every few hundred
thousand years to once every million years.
``Extinction-class'' objects (10 km or greater in
size) are estimated to occur on average once every 50 million
to 100 million years.
Past NEO Impacts and Events
Evidence from past major NEO impacts or aerial explosions
illustrates the catastrophic consequences that these objects can have:
The impact of a NEO on the north side of Mexico's
Yucatan Peninsula some 65,000,000 years ago that is thought to
have helped bring about the extinction of the dinosaurs and to
have destroyed 75 percent of life on Earth. Scientists estimate
the frequency of an impact event of this magnitude to be about
once every 50-100 million years.
The Barringer Meteor Crater in Arizona is about one
kilometer wide and is estimated to be 50,000 years old. The
impact was caused by a nickel-iron meteorite, weighing about
300,000 tons and whose size was roughly 45 meters in diameter.
The impact explosion was comparable to 20 million tons of TNT
and created a hole 174 meters deep. Scientists estimate these
types of impacts to occur once every 250-1,000 years.
The Tunguska Event took place in Siberia in 1908 when
a NEO estimated to be 50-100 meters in size disintegrated about
five-ten kilometers above the Earth's surface. That event
unleashed energy comparable to an estimated 10-15 million tons
of TNT. The explosion flattened trees and other vegetation over
an area of roughly 2,000 square kilometers [about 500,000
acres]. Scientists estimate that this scale of impact would
occur about once every 250-1,000 years.
Within the last two decades, instances of objects that passed near
Earth brought increasing interest in identifying NEOs and exploring
options to protect Earth from a potential NEO impact. For example:
On March 23, 1989, the 1989 FC asteroid with an
estimated diameter of 0.3 miles came within 430,000 miles of
Earth. 1989 FC carried the energy estimated to be more than
1,000 one-megaton hydrogen bombs. The asteroid was only
discovered after it had made its closest approach to Earth.
Asteroid 99942 Apophis, discovered in 2004, is
estimated to be roughly 300 meters in diameter, and could pass
as close as 29,470 km [about 18,300 miles] from the Earth's
surface [i.e., about the altitude that geosynchronous
communications satellites orbit the Earth] in 2029. Radar
observations conducted at the Arecibo Observatory in January
2005 significantly improved the understanding of the asteroid's
orbit. The probability of impact in 2036, when the asteroid
makes another close approach, is currently estimated to be 1/
45,000. Scientists hope to use Arecibo again in 2012 to further
refine the orbital coordinates when the asteroid is expected to
be in a favorable viewing position.
Determining the population of NEOs, including those in the PHO
category, can only be achieved by conducting a search campaign using
ground-based or space-based telescopes, or a combination of the two.
Previous Congressional Actions Related to NEOs
Congress has taken a number of steps since 1990 to promote
increased understanding of NEOs and the potential threat they pose, as
well as potential options for protecting Earth from hazardous NEOs. The
National Aeronautics and Space Administration Multi-year Authorization
Act of 1990 directed NASA to conduct two workshop studies on NEO
detection and interception. In 1993 the House Science and Technology
Committee held a hearing to review the results of the two reports, and
in 1994 [by means of House Report 103-654, which accompanied the
National Aeronautics and Space Administration Authorization and Space
Policy Act for Fiscal Year 1995] gave further direction to NASA to
coordinate with the Department of Defense and international space
partners on identifying and cataloging NEOs greater than one kilometer
in diameter that are in an orbit around the Sun that crosses Earth's
orbit within the next decade. In 1998, NASA established a Near-Earth
Object Program Office at the Jet Propulsion Laboratory and established
its Spaceguard Survey. The Survey had the goal of detecting and
cataloging 90 percent of NEOs one km or larger by the end of 2008.
NASA's Current NEO Survey Program and Budget
The Spaceguard Survey was housed in NASA's Exploration Systems
Mission Directorate in recent years, but earlier this year it was moved
to the Science Mission Directorate. NASA's report to Congress states
that the current budget for the program is $4.1 million per year for
Fiscal Years 2006-2012. NASA officials report that the annual budget is
allocated as follows: $3 million are used to support the search teams
and ground-based telescope facilities, $500,000 is allocated to JPL for
studies on near-Earth objects, $400,000 is provided to the Minor
Planets Center at the Smithsonian Center for Astrophysics to refine the
orbital coordinates of NEOs that have been detected, and the remainder
is allocated to additional NASA-funded studies.
NASA's report to Congress states that as of December 2006 the
Spaceguard Survey had identified 701 of the estimated 1100 NEOs larger
than one km that are believed to exist.
Recent Congressional Action on NEOs
Section 321 of the 2005 NASA Authorization Act directed NASA ``to
plan, develop, and implement a Near-Earth Object Survey program to
detect, track, catalogue, and characterize the physical characteristics
of near-Earth objects equal to or greater than 140 meters in diameter
in order to assess the threat of such near-Earth objects to the Earth.
It shall be the goal of the Survey program to achieve 90 percent
completion. . .within 15 years after the date of enactment of this
Act.'' Section 321 also directed NASA to report to Congress on an
analysis of ground-based and space-based alternatives to conduct the
Survey; a recommendation on which Survey option to pursue and a
proposed budget; and an analysis of options to divert an object that
threatens impact with Earth.
NASA's Near-Earth Object Survey and Deflection Analysis of Alternatives
Report to Congress
NASA's report, Near-Earth Object Survey and Deflection Analysis of
Alternatives, Report to Congress, prepared in response to Sec. 321 of
the NASA Authorization Act of 2005, was submitted to Congress in March
2007. The study was led and managed by NASA's Office of Program
Analysis and Evaluation. The report is a condensed version of a longer,
un-circulated version that included the analysis on which findings of
the report to Congress were based. The 2007 report to Congress provides
options for meeting the Survey goals by 2020, as required in the Act,
and options for meeting the goals on a longer timeframe. However, the
report does not provide Congress with NASA's recommended option for
conducting the Survey or provide a cost estimate for that Survey.
The report's basic conclusion is that ``NASA recommends that the
program continue as currently planned, and we will also take advantage
of opportunities using potential dual-use telescopes and spacecraft--
and partner with other agencies as feasible--to attempt to achieve the
legislated goal within 15 years. However, due to current budget
constraints, NASA cannot initiate a new program at this time.''
In addition, the report contained a number of additional findings,
including:
``The goal of the Survey Program should be modified
to detect, track, catalogue, and characterize, by the end of
2020, 90 percent of all Potentially Hazardous Objects (PHOs)
greater than 140m whose orbits pass within 0.05 AU of the
Earth's orbit (as opposed to surveying for all NEOs).
The Agency could achieve the specified goal of
surveying for 90 percent of the potentially hazardous NEOs by
the end of 2020 by partnering with other government agencies on
potential future optical ground-based observatories and
building a dedicated NEO survey asset assuming the partners'
potential ground assets come online by 2010 and 2014, and a
dedicated asset by 2015.
Together, the two observatories potentially to be
developed by other government agencies could complete 83
percent of the survey by 2020 if observing time at these
observatories is shared with NASA's NEO Survey Program.
New space-based infrared systems, combined with
ground-based assets, could reduce the overall time to reach the
90 percent goal by at least three years. Space systems have
additional benefits as well as costs and risks compared to
ground-based alternatives.
Radar systems cannot contribute to the search for
potentially hazardous objects, but may be used to rapidly
refine tracking and to determine object sizes for a few NEOs of
potentially high interest. Existing radar systems are currently
oversubscribed by other missions.
Determining a NEO's mass and orbit is required to
determine whether it represents a potential threat and to
provide required information for most alternatives to mitigate
such a threat. Beyond these parameters, characterization
requirements and capabilities are tied directly to the
mitigation strategy selected.''
The NASA report also describes the general advantages and
disadvantages of using ground versus space-based search systems and
analyzes an approach that includes a combination of ground-based and
space-based NEO search capabilities:
Ground-based Optical Systems. Ground-based telescopes
are relatively easy to maintain and offer the flexibility for
upgrades. They are limited by their nighttime or early morning
viewing periods as well as the atmosphere's effects on
observations.
Space-Based Optical Systems. These systems can take
advantage of proven space technologies, are not restricted in
viewing hours and atmospheric interference, and can observe
objects in inner Earth orbits or orbits similar to Earth's more
easily than can ground-based systems. Space-based survey
approaches however require access to space, data downlinks, and
replacement spacecraft.
Space-Based Infrared Systems. The technology for
space-based infrared systems is less mature than space-based
optical technology, however the infrared systems would require
smaller aperture telescopes and could provide greater accuracy
on the sizes of NEOs they detect.
The NASA report suggests that the goals of the Congressionally-
mandated survey could be met by acquiring shared access to a proposed
ground-based NSF/DOE, telescope system, the Large Synoptic Survey
Telescope (LSST) and a potential Air Force telescope system, the
Panoramic Survey Telescope and Rapid Response System (Pan-STARRS). In
addition, this exemplar search program would require an additional
LSST-type telescope dedicated to the NEO survey effort.
LSST is proposed as a large-aperture, wide-field telescope.
According to literature from the LSST project, the telescope will
``Conduct a survey over an enormous volume of sky; do it with a
frequency that enables repeat exposures of every part of the sky every
few nights in multiple colors; and continue this mode for ten years to
achieve astronomical catalogs thousands of times larger than have ever
previously been compiled.'' LSST was recommended as a high priority
initiative in the 2001 National Academies Astronomy and Astrophysics
Decadal Survey. In addition, the 2003 National Academies Solar System
Exploration Survey included the following recommendation: ``The SSE
[Solar System Exploration] Survey recommends that NASA partner equally
with the National Science Foundation to design, build, and operate a
survey facility, such as the Large Synoptic Survey Telescope (LSST). .
.to ensure that LSST's prime solar system objectives are accomplished''
LSST has not yet been approved as new project start by the National
Science Foundation.
The Director of the LSST project is expected to testify that LSST
could complete the mandated survey within 12 years from the start of
the telescope operations. This goal would involve modifications to the
observing strategy and to the data processing procedures. The LSST
project estimates that the cost of an LSST NEO survey over 12 years
would be about $125M.
Pan-STARRS is being developed by the University of Hawaii with
funding from the U.S. Air Force. A main goal of Pan-STARRS is to detect
potentially hazardous objects. Pan-STARRS is planned to be a system of
four individual telescopes that will survey large areas of the sky at a
high degree of sensitivity. The prototype one-mirror Pan-STARRS
telescope is complete; a full four-telescope system has not yet been
approved.
The NASA report to Congress also indicates that by using a space-
based infrared telescope [along with the LSST and Pan-STARRS systems],
NASA could exceed the mandated requirement and detect an estimated 90
percent of the PHO population by 2017.
An additional capability that could be brought to bear on the NEO
survey task is NASA's Wide-field Infrared Survey Explorer (WISE), which
is scheduled for launch in 2009. The WISE spacecraft will survey the
sky in the infrared band at high sensitivity. Asteroids, which absorb
solar radiation, can be observed through the infrared band. NASA
officials told Committee staff that NASA plans to use WISE to detect
NEOs, in addition to performing its science goals. NASA expects that
WISE could detect 400 NEOs [or roughly two percent of the estimated NEO
population of interest] within the spacecraft's six month--one year
mission.
It should be noted that the National Academies' 2001 report New
Frontiers in the Solar System [the solar system exploration decadal
survey] commented on the potential value of ground-based observatories
for detecting near-Earth objects: ``The SSE Survey's Primitive Bodies
Panel endorses the concept of a large telescope capable of an all-sky
search strategy that would reveal large numbers of near-Earth
objectsalso endorses a telescope that would enable the physical study
of such objects by spectroscopic and photometric techniques. The panel
heard recommendations for the Large Synoptic Survey Telescope (LSST)
and the Next Generation Lowell Telescope (NGLT). . .Other options,
including the Panoramic Optical Imager concept, should be explored and
a choice made that NASA can support in the next decade.
According to the NASA report to Congress, once a NEO is identified,
further characterization of its mass and orbit are required to ``assess
the threat'' as required in the Act. Characterization involves
observations that provide details on an object's structure, whether it
is a single or binary NEO, its porosity, rotation rate, composition,
and surface features. NASA's report to Congress discusses the need to
characterize an object to inform decisions on mitigation.
According to NASA officials, characterization is usually focused on
those objects that are identified as posing a potential threat. Both
optical and radar ground-based systems can be used, however radar
provides precise orbital determinations more quickly than optical
systems. A dedicated in-situ mission to observe the object would
provide the greatest detail on the character of the object and,
according to the NASA report to Congress, help to ``confirm the
probability of impact and characterize the potential threat if
deflection is necessary.''
The report presents two broad strategies for diverting asteroids
from a collision path with Earth. ``Impulsive'' options would involve
the use of conventional or nuclear explosives and have immediate
results. ``Slow push'' options would achieve deflection results over a
period of time.
``Impulsive'' options include:
Surface conventional explosive (detonating on
impact)
Subsurface conventional explosive
Standoff nuclear explosive (detonate on flyby
with proximity fuse)
Surface nuclear explosive (detonate via
impact with surface fuse)
Delayed nuclear explosive (surface lander,
detonate at chosen time)
Subsurface nuclear explosive
Kinetic impact (high speed impact)
``Slow push'' approaches include:
Focused solar (focused beam to burn-off
surface material)
Pulsed laser (rendezvous mission that burns-
off material using laser)
Mass driver (rendezvous mission mines and
ejects material)
Gravity tractor (large rendezvous mission
flies in proximity to ``pull'' object off course)
Asteroid tug (rendezvous mission attaches to
and pushes object)
Heating of surface material
The report includes the following findings on deflection
alternatives:
``Nuclear standoff explosions are assessed to be 10-
100 times more effective than the non-nuclear alternatives. .
.. Other techniques involving the surface or subsurface of
nuclear explosions may be more efficient, but they run the risk
of fracturing the target NEO. They also carry higher
development and operations risks.
Non-nuclear kinetic impactors are the most mature
approach and could be used in some deflection/mitigation
scenarios, especially for NEOs that consist of a single, small
solid body.
``Slow push'' mitigation techniques are the most
expensive, have the lowest level of technical readiness, and
their ability to both travel to and divert a threatening NEO
would be limited unless mission durations of many years to
decades are possible.
30-80 percent of potentially hazardous NEOs are in
orbits that are beyond the capability of current or planned
launch systems. Therefore, planetary gravity assist swing-by
trajectories or on-orbit assembly of modular propulsion systems
may be needed to augment launch vehicle performance, if these
objects need to be deflected.''
Critics of NASA's analysis of deflection options argue that NASA's
report focuses on atypical asteroid threats rather than the objects of
size ranges that have a much higher probability of actually impacting
the Earth. They argue that NASA's focus on the less likely scenarios
results in a set of deflection requirements that are skewed towards
nuclear explosives. If the focus would be placed on addressing the
deflection requirements of the smaller, more common PHOs, the critics
of NASA's analysis would assert that ``over 99 percent of them can be
deflected using non-nuclear means.'' One of the witnesses at the
hearing, Mr. Russell ``Rusty'' Schweickart, will discuss issues related
to NASA's analysis of deflection options, as well as identify what he
believes are serious technical flaws in NASA's report to Congress.
Planetary Radar Facilities
Arecibo Observatory
The Arecibo Observatory in Puerto Rico, which has been described as
``the largest and most sensitive'' ground-based radar telescope on
Earth, has been used to reduce the uncertainty of NEO collision
estimates and refine the time period of when a NEO may pass near Earth.
In addition, radar observations are more precise than data from optical
telescopes in identifying details on the mass, shapes, trajectories,
sizes, and on whether the NEO is a single object or part of a binary
system. In 2005, Arecibo observations improved the estimates of the
trajectory for the object, Apophis, which is on a path that will take
it close to Earth in 2029. Research using the Arecibo Observatory also
helps improve our understanding of how solar radiation influences near-
Earth objects.
Arecibo is operated by Cornell University under a cooperative
agreement with the National Science Foundation. A 2006 independent
review of all NSF ground-based astronomy facilities recommended that
``The National Astronomy and Ionosphere Center [Arecibo Observatory] .
. .should seek partners who will contribute personnel or financial
support to the operation of Arecibo. . . by 2011 or else these
facilities should be closed.'' At present, the planetary radar facility
at Arecibo is funded through FY 2008. Funding beyond that date is
uncertain.
NASA's Goldstone Deep Space Tracking Station
The only planetary radar facility other than Arecibo is NASA's
Goldstone Deep Space Tracking Station in Goldstone, California.
Goldstone is less sensitive than Arecibo, however its steerable antenna
allows it to see a larger portion of the sky. NASA is planning to
replace the current Deep Space Network antennas and is looking at a
number of options, including phased array antennas. The current
replacement options do not appear to provide a planetary radar
capability comparable to that of the existing Goldstone facility.
The 2003 National Academies Solar System Exploration Survey report
contained the following recommendation: ``In addition, NASA should
continue to support ground-based observatories for planetary science,
including the planetary radar capabilities at the Arecibo Observatory
in Puerto Rico and the Deep Space Network's Goldstone facility in
California. . .as long as they continue to be critical to missions and/
or scientifically productive. . .''
NEO Contributions to Science, Human Exploration, and Resource
Utilization
The NASA report notes that an increased search for and
characterization of NEOs will benefit scientific discovery and study of
Kuiper Belt Objects, as well as in determining whether certain comets
originated in the Kuiper Belt. Further data on NEOs could also provide
information that could be used to consider extracting and using
asteroid resources and for considering a potential human mission to an
asteroid. A 1998 National Academies Report on The Exploration of Near-
Earth Objects notes that:
``Although it would be difficult to justify human exploration
of NEOs on the basis of cost-benefit analysis of scientific
results alone, a strong case can be made for starting with NEOs
if the decision to carry out human exploration beyond low Earth
orbit is made for other reasons. Some NEOs are especially
attractive targets for astronaut missions because of their
orbital accessibility and short flight duration. Because they
represent deep space exploration at an intermediate level of
technical challenge, these missions would also serve as
stepping stones for human missions to Mars. Human exploration
of NEOs would provide significant advances in observational and
sampling capabilities.''
NEO-Related Activities at the United Nations
The United Nation's Committee on the Peaceful Uses of Outer Space
(COPUOS), Scientific and Technical Subcommittee has discussed and
considered the issue of NEOs. In 2006, the subcommittee established a
Working Group on Near-Earth Objects to focus on the issue over the
2006-2007 timeframe and also formed an Action Team. Over the next one
to two years, the subcommittee plans to continue to obtain reports on
NEO activities and to address the need for more international
coordination on observations and follow-up studies. The subcommittee
also plans to work on international procedures for handling NEO
threats.
Space Science Missions to Comets and Asteroids
In addition to its ground-based Spaceguard Survey program, NASA and
non-U.S. space agencies have launched, or are planning to undertake a
number of space science missions to study asteroids and comets. NASA's
report to Congress notes that information gained from these missions
benefits the agency's current NEO program. A number of past, current,
and future missions of note include:
NASA's Near-Earth Asteroid Rendezvous (NEAR) mission,
launched in 1996, flew by two asteroids and studied one, Eros;
The Stardust mission collected dust samples from
comet Wild 2;
Deep Impact, launched in 2004, penetrated comet
Tempel 1;
The Dawn mission, launched in late September 2007 is
en route to study, Ceres and Vesta, two of the largest known
asteroids located in the main asteroid belt between Mars and
Jupiter;
Japan's Hayabusa mission had the objective of
collecting a sample from the near-Earth asteroid Itokawa, and
the sample carrier is en route back to Earth; and
The European Space Agency's Rosetta mission to comet
Churymov-Gerasimenko in late 2014 will rendezvous with and land
on the comet.
In addition, the European Space Agency has conducted
studies on a potential space mission that could test and
validate technologies for deflecting an asteroid.
Chairman Udall. Good morning. This hearing will come to
order. I would like to extend a particular welcome to our
witnesses, and in particular, recognize Congressman Luis
Fortuno's presence here with us today.
As many of you may recall, today's hearing on Near-Earth
Objects was originally scheduled for October 11, but we
postponed it in the wake of our good friend Rep. Jo Ann Davis'
untimely death.
Thus, before we proceed any further, I would like to
express my appreciation to each of the witnesses for your
willingness to accommodate that postponement, and appear before
us today. Your testimony will be invaluable to us as we
consider how best to proceed in getting a better understanding
of the potential threats of Near-Earth Objects, NEOs, as well
as options for dealing with them.
Today's hearing is the latest in a series that stretches
back to the early 1990s. We have come a long way since the late
George Brown, former Chairman of the Science and Technology
Committee, led the first efforts to focus Congressional
attention on the potential threat posed by Near-Earth asteroids
and comets.
It has been a bipartisan effort over the intervening years,
and a lot has been accomplished. In that regard, I want in
particular to salute the dedication of Mr. Rohrabacher in
pushing for continued federal initiatives to detect, track, and
catalog NEOs, as well as to examine ways to deflect them if
necessary. He has been an effective catalyst for action, and I
look forward to continuing to work with him on this issue.
As we will hear from our witnesses, much progress has been
made in detecting and cataloging the largest NEOs over the last
decade. However, as we will also hear, much more remains to be
done. In particular, we need to survey potentially hazardous
asteroids that are smaller than the ones cataloged to date, but
which could do significant damage if they impact or explode
above the Earth's surface near populated areas.
That is why Congress directed NASA to ``plan, develop, and
implement'' a NEO survey program for objects as small as 140
meters in size, in the NASA Authorization Act of 2005. As a
result, I am disappointed and concerned that NASA's report to
Congress failed to provide a recommended option and budget plan
for such a survey, as directed by the Act. In fact, the report
says NASA has no plans to do anything beyond the current
Spaceguard program at this time.
Equally troubling, one of the NASA witnesses will testify
that ``NASA would be pleased to implement a more aggressive NEO
program, if so directed by the President and Congress,'' with
the implication that Congress has not yet done so. I believe
section 321 of the NASA Authorization Act, which I quoted
earlier, is unambiguous. Congress, in fact, has directed NASA
to ``plan, develop, and implement'' such a program, and we
would hope that the President would send over a NASA budget
request that reflects that Congressional direction.
Today, I want to focus on where we go from here. Given the
lack of a clear plan in NASA's report to Congress, I hope that
our witnesses today will be able to provide some guidance to
the Committee on the best and most cost-effective path forward
for meeting the goal of surveying NEOs down to 140 meters in
size. In that regard, there are a number of related questions
that need to be addressed.
First, I would like to hear from each of the witnesses
about the planetary radar capabilities at Arecibo and
Goldstone. How important are they to addressing the NEO task?
Second, how can we make the most effective use of capabilities
being planned or developed by other federal agencies, such as
LSST and Pan-STARRS, and what role should NASA play in
supporting them?
NASA's testimony indicates that it has been providing funds
to the Air Force's Pan-STARRS project, so that it will be
capable of providing data on NEO detections. That is an
interesting development, and it raises the question of whether
NASA should also be providing funds to other facilities, such
as Arecibo, and the proposed LSST project, if doing so will
materially contribute to meeting the NEO survey objectives in a
responsible, cost-effective manner.
Third, I would like to know if there are adjustments to
either the timetable or scope of the NEO survey called out in
the NASA Authorization Act that would make sense, either by
allowing more cost-effective approaches on a slightly longer
timetable, or by focusing on just potentially hazardous
objects, rather than on all NEOs.
Fourth, surveying NEOs is just part of the task. If we find
one that is headed towards Earth, we will need to have good
options for deflecting it. What priorities should be given to
developing deflection technologies versus NEO survey systems in
the coming years?
And finally, the potential threat posed by Near-Earth
Objects is not isolated to the United States. What
contributions are other national and international bodies
making to the effort? Should more be done?
Well, as you can see, we have a lot to consider today.
Fortunately, we have a very distinguished set of witnesses to
assist us in our oversight task, and I again want to welcome
all of you, and I look forward to your testimony.
At this point, the Chair now recognizes my friend, the
Ranking Member, Mr. Feeney from Florida, for his opening
remarks.
[The prepared statement of Chairman Udall follows:]
Prepared Statement of Chairman Mark Udall
Good morning. I'd like to extend a welcome to our witnesses and in
particular recognize Congressman Luis Fortuno's presence here with us
today.
As many of you may recall, today's hearing on Near-Earth Objects
was originally scheduled for October 11th, but we postponed it in the
wake of Rep. Jo Ann Davis's untimely death. Thus, before we proceed any
further, I'd like to express my appreciation to each of the witnesses
for your willingness to accommodate that postponement and appear before
us today.
Your testimony will be invaluable to us as we consider how best to
proceed in getting a better understanding of the potential threats
posed by Near-Earth Objects--NEOs, as well as options for dealing with
them.
Today's hearing is the latest in a series that stretches back to
the early 1990s. We have come along way since the late George Brown--
former Chairman of the Science and Technology Committee--led the first
efforts to focus congressional attention on the potential threat posed
by Near Earth asteroids and comets. It has been a bipartisan effort
over the intervening years, and a lot has been accomplished.
In that regard, I in particular want to salute the dedication of
Mr. Rohrabacher in pushing for continued federal initiatives to detect,
track, and catalog NEOs, as well as to examine ways to deflect them if
necessary. He has been an effective catalyst for action, and I look
forward to continuing to work with him on this issue.
As we will hear from our witnesses, much progress has been made in
detecting and cataloging the largest NEOs over the last decade.
However--as we will also hear--much more remains to be done.
In particular, we need to survey potentially hazardous asteroids
that are smaller than the ones cataloged to date, but which could do
significant damage if they impact or explode above the Earth's surface
near populated areas. That is why Congress directed NASA to ``plan,
develop, and implement'' a NEO survey program for objects as small as
140 meters in size in the NASA Authorization Act of 2005.
As a result, I'm disappointed and concerned that NASA's report to
Congress failed to provide a recommended option and budget plan for
such a survey, as directed by the Act. In fact, the report says NASA
has no plans to do anything beyond the current Spaceguard program at
this time.
Equally troubling, one of the NASA witnesses will testify that
``NASA would be pleased to implement a more aggressive NEO program if
so directed by the President and Congress,''--with the implication that
Congress has not yet done so. I think Sec. 321 of the NASA
Authorization Act, which I quoted earlier, is unambiguous--Congress has
in fact directed NASA to ``plan, develop, and implement'' such a
program. And we would hope that the President would send over a NASA
budget request that reflects that congressional direction.
Today, I want to focus on where we go from here. Given the lack of
a clear plan in NASA's report to Congress, I hope that our witnesses
today will be able provide some guidance to this committee on the best
and most cost-effective path forward for meeting the goal of surveying
NEOs down to 140 meters in size.
In that regard, there are a number of related questions that need
to be addressed. First, I'd like to hear from each of the witnesses
about the planetary radar capabilities at Arecibo and Goldstone. How
important are they to addressing the NEO task?
Second, how can we make the most effective use of capabilities
being planned or developed by other federal agencies, such as LSST and
Pan-STARRS, and what role should NASA play in supporting them? NASA's
testimony indicates that it has begun providing funds to the Air
Force's Pan-STARRS project ``so that it will be capable of providing
data on NEO detections. . .''
That's an interesting development, and it raises the question of
whether NASA should also be providing funds to other facilities such as
Arecibo and the proposed LSST project if doing so will materially
contribute to meeting the NEO survey objectives in a responsible, cost-
effective manner.
Third, I'd like to know if there are adjustments to either the
timetable or scope of the NEO survey called out in the NASA
Authorization Act of 2005 that would make sense--either by allowing
more cost-effective approaches on a slightly longer timetable or by
focusing on just potentially hazardous objects rather than on all NEOs.
Fourth, surveying NEOs is just part of the task. If we find one
that it is headed towards Earth, we will need to have good options for
deflecting it. What priority should be given to developing deflection
technologies versus NEO survey systems in the coming years?
Finally, the potential threat posed by Near-earth objects is not
isolated to the United States. What contributions are other national
and international bodies making to the effort? Should more be done?
Well, as you can see, we have a lot to consider today. Fortunately,
we have a very distinguished set of witnesses to assist us in our
oversight task.
I again want to welcome all of you, and I look forward to your
testimony.
Mr. Feeney. Well, thank you, Mr. Chairman, and I appreciate
you calling this morning's hearing, although I did tell you as
I greeted you this morning that this is just one more thing for
us to worry about, that hadn't been on my list until a couple
weeks ago, when I saw the original notice of hearing.
And I want to echo your remarks. We are very grateful to
the witnesses, because we had to reschedule the hearing on
short notice, and we thank you, and we are very appreciative
that you are here today, so that we can accommodate that
emergency change.
NASA's Near-Earth Object program, though very modest in
scale compared to many of the agency's multi-billion dollar
endeavors, is vitally important, and NASA has been doing an
exemplary job standing up an office and managing the Nation's
and world's only survey for potentially hazardous Earth-
crossing asteroids and comets. I find it distressing that other
nations haven't, to date, taken a more active role, and I note
that we have some visitors from Germany here today. We are very
grateful for their interest.
NASA began the NEO survey, called the Spaceguard program,
in 1998, and I note that my colleague, Dana Rohrabacher, who is
here, was instrumental in advocating that, with the goal of
detecting and cataloging 90 percent of all potentially
hazardous asteroids and comets larger than one kilometer in
diameter within a decade, and it appears to be relatively on
track to meet that target. Subsequently, a 2003 NASA-chartered
team of scientists recommended that the survey seek all NEOs of
140 meters in diameter or larger, reasoning that the smallest
of these could still inflict large regional impacts if they
struck the Earth.
Their recommendations were made part of the 2005 NASA
authorization legislation, directing NASA to ``plan, develop,
and implement a Near-Earth Object survey program to detect,
track, catalog, and categorize Near-Earth Objects equal to or
greater than 140 meters in diameter.''
The goal was to get 90 percent completion within 15 years.
This change in mission is no small matter. As the universe of
potentially hazardous objects, PHOs, to be detected and
cataloged increased by a factor of 20, from 1,000 to
approximately 20,000. The bill also required NASA to complete
an analysis of alternatives to meet this ambitious goal, and to
report back with a recommended option. NASA provided such a
report earlier this year, but did not indicate a preferred
choice, instead urging the current Spaceguard program be
allowed to continue its survey for one kilometer and larger
Near-Earth Objects, that will allow the agency to take
advantage of opportunities using potential dual use telescopes
and spacecraft to achieve the goals outlined in the 2005
authorization.
Although the 15-year timeline may not be met in all cases,
NASA's rationale is purely budget-driven, arguing that current
resources are too constrained. While disappointed, I certainly
can't disagree or argue with their reasoning.
At this morning's hearing, it is my hope that we get a
clearer understanding of NASA's plans to proceed with utilizing
dual use telescopes and spacecraft, their potential costs and
schedules, and other facilities that may be utilized, including
the Arecibo Observatory.
I hope to hear concrete steps taken by NASA to develop
cooperative relationships necessary to ensure the requirements
laid out in the 2005 NASA authorization are met. We will also
hear about the future of the Arecibo Radio Observatory in
Puerto Rico, the largest and most powerful such facility in the
world. Arecibo is operated by the Cornell University under a
contract with the National Science Foundation (NSF). It appears
very likely that NSF will significantly reduce its financial
support, such that Arecibo will have to shut down its radar
facility. This, I think, would be a mistake. Arecibo has the
capability of making very precise orbital calculations in a
short amount of time, a critical feature that optical
telescopes simply cannot match. And the sum of money at stake
is on the order of several million dollars a year, an
investment I think is well worth the return. While NSF may be
outside the purview of this subcommittee, the ramifications of
Arecibo's loss to the NEO program begs the discussion.
I want to first welcome my good friend, Luis Fortuno, to
today's hearing. I want to also thank all of our guests once
again, express my appreciation for changing their schedule to
accommodate our schedule, and I want to thank my Chairman, Mr.
Udall, and with that, look forward to the discussion.
[The prepared statement of Mr. Feeney follows:]
Prepared Statement of Representative Tom Feeney
Thank you, Mr. Chairman, for calling this morning's hearing. And I
want to echo Mr. Udall's comments, acknowledging that our originally
scheduled hearing was postponed on very short notice. I greatly
appreciate that all of our scheduled witnesses were able to accommodate
the date change, and I hope notice got out quickly enough to save you
from unnecessary travel.
NASA's Near-Earth Object (NEO) program, though very modest in scale
compared to many of the agency's multi-billion dollar endeavors, is
vitally important, and NASA has been doing an exemplary job standing-up
an office and managing the Nation's--and world's--only survey for
potentially hazardous Earth-crossing asteroids and comets. I find it
distressing that other nations haven't, to date, taken a more active
role.
NASA began the NEO survey, called the ``Spaceguard'' program, in
1998 with the goal of detecting and cataloguing 90 percent of all
potentially hazardous asteroids and comets larger than one kilometer in
diameter within a decade, and it appears to be on track to meet that
target.
Subsequently, in 2003 a NASA-chartered team of scientists
recommended that the survey seek all NEOs of 140 meters in diameter or
larger, reasoning that the smallest of these could still inflict large
regional impacts if they struck Earth. Their recommendations were made
part of the 2005 NASA authorization legislation, directing NASA to
``plan, develop and implement a Near-Earth Object Survey program to
detect, track, catalogue, and characterize. . .near-Earth objects equal
to or greater than 140 meters in diameter. . .,'' with the goal of 90
percent completion within 15 years. This change in mission is no small
matter, as the universe of potentially hazardous objects (PHOs) to be
detected and catalogued increased by a factor of twenty (from 1000 to
20,000). The bill also required NASA to complete an analysis of
alternatives to meet this ambitious goal and to report back with a
recommended option.
NASA provided such a report earlier this year but did not indicate
a preferred choice, instead urging the current ``Spaceguard'' program
be allowed to continue its survey for 1 kilometer and larger near-Earth
objects, and to allow the agency to take advantage of opportunities
using potential dual-use telescopes and spacecraft to achieve the goals
outlined in the 2005 authorization, although the 15 year timeline may
not be met in all cases. NASA's rationale is purely budget driven,
arguing that current resources are too constrained. While disappointed,
I certainly can't disagree with their reasoning.
At this morning's hearing, it is my hope that we get a clearer
understanding of NASA's plans to proceed with utilizing dual-use
telescopes and spacecraft, their potential costs and schedules, and
other facilities that may be utilized, including the Arecibo
Observatory. I hope to hear of concrete steps being taken by NASA to
develop cooperative relationships necessary to ensure the requirements
laid out in the 2005 NASA authorization are met.
We'll also hear about the future of the Arecibo Radio Observatory
in Puerto Rico, the largest and most powerful such facility in the
world. Arecibo is operated by Cornell University under a contract with
the National Science Foundation (NSF). It appears very likely NSF will
significantly reduce its financial support such that Arecibo will have
to shut down its radar facility. This, I think, would be a mistake.
Arecibo has the capability of making very precise orbital calculations
in a short amount of time, a critical feature that optical telescopes
cannot match. And the sum of money at stake is on the order of about $2
million a year, an investment that I think is well worth the return.
While NSF may be outside the purview of this subcommittee, the
ramifications of Arecibo's loss to the NEO program begs the discussion.
I want to welcome my friend, Rep. Fortuno, to today's hearing. I
also want again to say thanks to our excellent panel of expert
witnesses for taking time from their busy schedules to be here.
Thank you, Mr. Chairman.
Chairman Udall. Thank you, Congressman Feeney. If there are
Members who wish to submit additional opening statements, your
statements will be added to the record. Without objection, so
ordered.
And in addition, I would also like to include a statement
for the record from the Planetary Society into today's hearing.
Without objection, so ordered. [See Appendix 2: Additional
Material for the Record.]
At this time, I would like to go ahead and recognize our
first panel. And we are delighted to have Representative Luis
Fortuno, the Resident Commissioner of Puerto Rico, with us here
today, who will be testifying, I think, before the Committee
for the first time.
Congressman Fortuno, the floor is yours.
Panel 1
STATEMENT OF REPRESENTATIVE LUIS FORTUNO, RESIDENT
COMMISSIONER, PUERTO RICO
Mr. Fortuno. Thank you. Thank you, Mr. Chairman. Chairman
Udall, Ranking Member Feeney, distinguished Members of this
subcommittee.
Every day, an enormous quantity of cosmic material falls to
the Earth. Most burn up on reentry in a harmless way. However,
NASA predicts that more than 20,000 large, potentially
dangerous objects pass by the Earth in close proximity, and
given the proper circumstance, could threaten or severely
impact our existence. Although the chances of a major impact
are slim, the consequences are too great to disregard.
I believe we should continue to advance our knowledge of
Near-Earth Objects and their potential consequences for life on
Earth. I commend Congressman Rohrabacher on his effort to
continue funding for Near-Earth Objects surveillance programs.
Since 1992, the Spaceguard program's goal was to discover 90
percent of the NEOs with one kilometer diameter potential by
2008. Although the success of this program will be substantial,
there will still be thousands of objects, ranging from 200 to
500 meters in diameter, that will be overlooked. We must
enhance our understanding of this phenomenon by studying and
assessing the threats posed to our environment and to our
national security.
According to Director Michael Griffin, NASA does not have
the funds to carry out a more extensive program. There have
been suggestions that NASA and the National Science Foundation
should cooperate to fund the construction of a new ground-based
telescope to perform tracking functions of Near-Earth Objects
and other astronomy surveys. I do not think we need to take on
such a burden, when there is still a great deal of information
to be gained by utilizing the unique capabilities of the
Arecibo Observatory in Puerto Rico.
As the world's largest and most powerful radio telescope,
the Arecibo Observatory is essential to monitoring and
surveying NEOs. However, the National Science Foundation has
threatened to close the observatory in 2011, and NASA has, so
far, been unwilling to assume funding of the radar required for
tracking NEOs. Closing the observatory will severely limit our
ability to quickly and accurately refine the orbits of newly
emerging threats, and reduce our monitoring capabilities.
This is why I have introduced H.R. 3737, which directs the
National Science Foundation and NASA to work together to ensure
continued full funding of the Arecibo Observatory, and in
particular, the radar. It is my recommendation and the
recommendation of 19 of my colleagues, that these agencies
start working in collaboration and reconsider how they allocate
their funding.
Mr. Chairman and Ranking Member Feeney, the Arecibo
Observatory's radar is the world's most powerful instrument for
post-discovery characterization and orbital refinement of Near-
Earth asteroids. Observations performed with the radar are
critical for identifying asteroids that might be on a collision
course with Earth.
I respectfully urge the Committee to consider continuing
the important work performed by the Arecibo observatory, and
consider, as well, H.R. 3737, as one potential solution to this
challenge. The unique capabilities of radar are critically
important as we work towards fulfilling the 2005 Congressional
mandate of detecting and characterizing 90 percent of NEOs down
to 140 meters in diameter.
A potentially dangerous collision of an asteroid or comet
is a very real threat. We must take action now to enhance our
awareness to prevent a catastrophe. A better understanding of
our skies will not only help us to comprehend the wonders of
the Earth's environment, but is essential to assessing the
dangers that may threaten our society.
The world's most sensitive radio telescope at Arecibo
Observatory must not be closed. By the way, we don't have final
numbers, but NSF is determining the cost of dismantling this
facility and bringing the area back to a greenfield, but it is
around $200 million. We are dealing with a $4 million gap a
year, so the numbers are certainly there as well.
Mr. Chairman and Ranking Member Feeney, thank you for the
opportunity to provide my views on this issue. I will now ask
permission to show, in the Committee's flatscreen, some images
of the Arecibo Observatory, that would help understand the size
and magnitude of this extraordinary science resource.
Chairman Udall. Please proceed.
Mr. Fortuno. Thank you.
That is an aerial picture of the radio telescope. As you
see, it is embedded in a number of mountains. That is another
angle. It is a massive facility. It really is.
It is visited every year by 300,000 people, 25,000 of them
are K-12 students. That is it.
Thank you again, Mr. Chairman.
[The prepared statement of Mr. Fortuno follows:]
Prepared Statement of Congressman Luis G. Fortuno
Chairman Udall and Ranking Member Feeney,
Every day an enormous quantity of cosmic material falls to the
Earth. Most burns up on re-entry in a harmless way, however NASA
predicts that more than 20,000 large, potentially dangerous objects
pass by the Earth in close proximity and, given the proper circumstance
could threaten or severely impact our existence. Although the chances
of a major impact are slim, the consequences are too great to
disregard. I believe we should continue to advance our knowledge of
Near-Earth Objects and the potential consequences for our life on
Earth.
I commend Congressman Rohrabacher on his efforts to continue
funding for Near-Earth Objects surveillance programs. Since 1992, the
Spaceguard program's goal was to discover 90 percent of the NEOs with
one kilometer diameter potential by 2008. Although the success of this
program will be substantial, there will still be thousands of objects--
ranging from 200 to 500 meters in diameter--that will be overlooked. We
must enhance our understanding of this phenomenon by studying and
assessing the threats posed to our environment and to our national
security.
According to Director Michael Griffin, NASA does not have the funds
to carry out a more extensive program. There have been suggestions that
NASA and the National Science Foundation should cooperate to fund the
construction of a new ground-based telescope to perform tracking
functions of Near-Earth Objects and other astronomy surveys. I do not
think we need to take on such a burden, as there is still a great deal
of information to be gained by utilizing the unique capabilities of the
Arecibo Observatory in Puerto Rico. As the world's largest and most
powerful radio telescope, the Arecibo Observatory is essential to
monitoring and surveying Near-Earth Objects. However, the National
Science Foundation has threatened to close the Observatory in 2011 and
NASA has so far been unwilling to assume funding of the radar required
for tracking NEOs. Closing the Observatory will severely limit our
ability to quickly and accurately refine the orbits of newly emerging
threats, and reduce our monitoring capabilities.
This is why I have introduced H.R. 3737, which directs the National
Science Foundation and NASA to work together to ensure continued full
funding of the Arecibo Observatory and in particular, the radar. It is
my recommendation that these agencies start working collaboratively and
reconsider how they allocate their funding.
Mr. Chairman and Ranking Member Feeney, the Arecibo Observatory's
radar is the world's most powerful instrument for post-discovery
characterization and orbital refinement of near-Earth asteroids. The
observations performed with the radar are critical for identifying
asteroids that might be on a collision course with Earth. I
respectfully urge the Committee to consider continuing the important
work performed by the Arecibo Observatory and consider, as well, H.R.
3737 as one potential solution to this challenge. The unique
capabilities of radar are critically important as we work towards
fulfilling the 2005 congressional mandate of detecting and
characterizing 90 percent of near-Earth Objects down to 140 meters in
diameter.
A potentially dangerous collision of an asteroid or comet is a very
real threat. We must take action now to enhance our awareness to
prevent a catastrophe. A better understanding of our skies will not
only help us to comprehend the wonders of the Earth's environment, but
is essential to assessing the dangers that may threaten our society.
The world's most sensitive radio/radar telescope at Arecibo Observatory
must not be closed.
Mr. Chairman and Ranking Member Feeney, thanks for the opportunity
to provide my views on this issue.
Discussion
Chairman Udall. Thank you, Resident Commissioner Fortuno.
This testimony has been very helpful, and I want to pay
particular note to the costs that might be involved in
decommissioning this site, and we look forward to getting
firmer numbers, because the obvious argument would be you would
take the money that would be used in decommissioning the site,
and actually operate it for a certain number of years or even
decades into the future.
At this time, I would be happy to recognize Mr. Feeney, if
he has any questions for his colleague, Mr. Fortuno.
Impact of Shutting Down Arecibo
Mr. Feeney. Well, thank you, Mr. Chairman, and thank you
for your testimony, Congressman. You know, as I read through
the materials and the different NSF and NASA projections, and
discussion of this important issue, all of them suggest that
Arecibo is very important to our capabilities.
Any decision to close it down seems to be purely budget-
driven, and so that I hope, as we get the numbers and the
estimates for what it would cost, and what the impact would be
of shutting it down, that you will immediately provide this
committee, and also, the Committee with jurisdiction over NSF,
with those numbers. Because if this is entirely cost-driven,
then we need to, as we are understanding the advantages that
everybody acknowledges, we also need to know that the, of
keeping it open, that the disadvantages of closing it also will
have a significant cost many, many times what it costs on an
annual basis to keep it alive.
Our next panel includes some very distinguished witnesses.
One of them, for example, Mr. Yeomans' testimony will tell us
that Arecibo and Goldstone complement one another and provide
two very different functions. That is very important, because
while the one telescope is capable of identifying Near-Earth
Objects that may be a threat, it is Arecibo that helps us
determine the exact threat to the Earth. And the fascinating
thing is that we have the capability with Arecibo, at least
with the large objects that we have now proceeded to catalog,
and we are very near our goal, or at least we are on track. Mr.
Yeomans will testify that once we find the vast majority of
them, they can be tracked, cataloged, and then ruled out or in
as threats during the next 100 years or so.
I think the people of the world would be very grateful to
know, especially with 100 years notice, that there may be a
catastrophe, driven by a Near-Earth Object. But most
importantly, we have the technological capabilities to actually
deflect or to eliminate the damage with that type of notice,
and again, Mr. Yeomans and our other witnesses will testify to
that.
So, Mr. Fortuno, I know that Congressman Rohrabacher had a
question. I wanted to yield a few minutes to him, but if you
could tell us the impact, because probably uniquely you are
able to tell us this question, the impact on Puerto Rico if we
shut Arecibo down, in the next year or two, what the local
impact would be. We will get to the technical experts. I had
assumed you are not an astrophysicist. Neither am I. Don't feel
bad about that. Go ahead and tell us the impact on Puerto Rico.
Mr. Fortuno. Thank you, and thank you for your comments.
Certainly. The impact, we are estimating that it will be about
$50 million for the Arecibo area, actually. On top of that, the
impact on those kids that may have an interest in science and
technology, that will not be able, otherwise, to visit a
facility like this one. If I may add, the Arecibo radio
astronomy led to the first discovery of a planet outside of our
own solar system, to the first discovery of a binary pulsar,
resulting in a Nobel Prize, and the first detailed, three
dimensional mapping of how galaxies are distributed in the
universe.
So, it is really, from the scientific point of view, it
will be priceless to our young students, that have an interest
in this area.
George Brown
Mr. Feeney. Any remaining time, I would be pleased to yield
to Congressman Rohrabacher.
Mr. Rohrabacher. Thank you very much. And thank you, Mr.
Chairman, for your kind words, and bipartisan words, and
holding the hearing. I can't help but notice George Brown's
picture right back there. I don't know how many people in this
room knew George Brown. I knew him. He was the Chairman here
when I came here 20 years ago, and he was a wonderful human
being. He was a man of integrity, and I am very pleased that
some of the work that I have done in this area actually bore
the name of George Brown, because he was just a fine person,
and had that very same bipartisan spirit that Mr. Udall has
been trying to demonstrate here today.
And hopefully, when we are talking about things that might
threaten the entire planet, that may well motivate Congress to
be bipartisan, if nothing else does. I mean, after all, it is
just the entire planet that may be destroyed. But George Brown
really gave me personal guidance, and his integrity was very
much appreciated.
Importance of Arecibo With Regard to Cost
When we are talking about Arecibo, I want to, of course,
recognize the hard work that Congressman Fortuno is actually
putting into this effort. It is a heroic effort. I am very
pleased to be assisting him. But of course, we are not trying
to do anybody any favors here. This isn't an issue of doing
anyone a favor.
First and foremost, the Arecibo telescope is doing work
currently that would cost us more, even outside of the area of
Near-Earth Objects. Even outside the area of Near-Earth
Objects, the Arecibo telescope is doing work that would be more
costly to do if, for example, we would send satellites. I
understand we sent a mission to Venus that cost a certain
amount of money, but the actual images that we got back from
Arecibo were better than sending the probe up to Venus. Now,
how much did that cost us? I mean, it probably cost us enough
to keep Arecibo going for a decade.
And clearly, also, when you look at the shutdown costs,
which has been mentioned here, if you take all of that
together, well, you could probably put that in the bank, and
the interest on that money would probably keep the Arecibo
telescope going. And this exemplifies sort of the screwball
nature of the way we do business up here on Capitol Hill
sometimes. And if we let this asset be set aside and closed
down, it would be a tragedy, but also, as I say, very symbolic
of the fact that we can't even do our job in Capitol Hill
enough to take a very cost-effective asset, and something that
is doing a mission that is vitally important to our security,
that we can't even get ourselves together enough to get a
limited amount of money to keep that project going. So, I think
this is very symbolic, and that we should all be working
together on this, and we are working on this.
Just a question. Now, you mentioned the kids that there
are, and you mentioned how this would affect your economy. Tell
me, if we didn't know that a Near-Earth Object was coming, and
thus, one snuck by and landed in the Caribbean, would it be
possible that Puerto Rico would be wiped out?
Mr. Fortuno. Well, actually, anything can happen, but
certainly, you could have the East Coast of the United States,
not just the Caribbean, affected by something like that. And
again, the cost-effectiveness of this facility has to be
highlighted, and I thank you, Mr. Rohrabacher, for your
leadership on this issue, not just on Arecibo, the issue in
general.
I think it is an issue that we need to devote resources and
time to it, and again, I thank the Chairman and all the Members
of this subcommittee.
Mr. Rohrabacher. Shutting down Arecibo means that we are
intentionally putting ourselves in a position of ignorance of
potential threats, and with that ignorance may come bliss for a
while. However, let us note it also not only gives us
ignorance, but it also prevents us from having any chance of
deflection if there is a threat. So, we are putting ourselves
in a position of being ignorant of a potential threat, and
also, making ourselves incapable of responding to the potential
threat. And Arecibo is in the middle of this. No one should
take us seriously about watching out for the long-term
interests if we let this asset go.
So, I thank you very much, and I am looking forward to
working with you, working with the Ranking Member, and working
with the Chairman. We need to work on this, and show that we
can actually--if we can't get this done, we can't get anything
done. I mean, it is as simple as that.
Mr. Fortuno. Thank you.
Mr. Rohrabacher. And thank you for your hard work.
Visiting Arecibo
Chairman Udall. I thank the gentleman from California. I
would note, for the record, that my colleague from Texas, Mr.
Lampson, is here. There is nobody more passionate an advocate
for NASA and all that NASA does. I do believe he does not have
a question----
Mr. Lampson. No, I don't.
Chairman Udall.--for his colleague from Puerto Rico.
Resident Commissioner, if you----
Mr. Lampson. I do look forward to visiting, however.
Chairman Udall. I am sorry, you----
Mr. Lampson. I do look forward to visiting the facility
some time.
Chairman Udall. That is an open offer, I am sure.
Mr. Fortuno. It is a beautiful facility, but actually, some
time between December and March is the best time to visit.
Chairman Udall. Well, I again want to thank the Resident
Commissioner, and at this time, would be pleased to excuse you.
I know you have other responsibilities and a busy schedule.
Thank you again for joining us.
Mr. Fortuno. Thank you, Mr. Chairman.
Chairman Udall. At this time, as the Resident Commissioner
departs, we will pause, while the second panel can take your
seats and get comfortable, and then, we will begin the
presentations from the second panel in a few minutes.
I want to welcome the panel, and at this time, it seems
appropriate to introduce all of the witnesses that have joined
us. I would, before I do so, just let the panel know, and the
others who are here with us, that there are votes pending at
some point in the next 25 to 30 minutes. We will, I think, have
a series of at least two votes, and we will do all we can to
move the testimony forward, and then we will recess for 40
minutes, and then reconvene the hearing.
Let me begin here, on my left to the audience's right, with
Dr. James Green, who is the Director of the Planetary Science
Division at NASA. Next to him is, moving from left to right
again, is Dr. Scott Pace, who is the Associate Administrator of
the Office of Program Analysis and Evaluation at NASA. Third on
the panel, Dr. Donald Yeomans, who is the manager of the Jet
Propulsion Laboratory's Near-Earth Object Program Office.
Proceeding down the line, Dr. Campbell, Dr. Donald Campbell,
who is a Professor of Astronomy at Cornell University, and a
former Director of the Arecibo Observatory. Next to Dr.
Campbell, Dr. J. Anthony Tyson, who is a Professor of Physics
at the University of California, Davis, and a Director of the
Large Synoptic Survey Telescope Project. And our last witness
on the second panel, we have Mr. Russell ``Rusty'' Schweickart,
former Apollo astronaut, Lunar Module pilot on Apollo IX, and
the Chairman and Founder of the B612 Foundation.
Welcome, gentlemen, to all of you. We are really pleased to
have you here today. I think all of you know, I think many of
you have been before the Committee before, that your spoken
testimony is limited to five minutes each, after which the
Members of the Subcommittee will have five minutes each to ask
questions.
So, Dr. Green, we will begin with you. The floor is yours.
Panel 2
STATEMENT OF DR. JAMES L. GREEN, DIRECTOR, PLANETARY SCIENCE
DIVISION, SCIENCE MISSION DIRECTORATE, NATIONAL AERONAUTICS AND
SPACE ADMINISTRATION (NASA)
Dr. Green. Thank you, Mr. Chairman and Members of the
Committee, for the opportunity to present information on NASA's
important efforts to find Near-Earth Objects or NEOs.
At the request of Congress, NASA currently conducts a very
successful NEO search program designed to find 90 percent of
the NEOs greater than one kilometer in diameter. Since the
program started in 1998, NASA has funded over $30 million in
NEO search efforts. During this time period, NASA has found, as
of Monday, I checked, 727 one kilometer or larger Near-Earth
asteroids and 65 Earth-approaching comets, as well as 4,198
smaller NEOs.
At the current discovery rate, we will have discovered more
than 50 large NEOs by the end of 2008, bringing us very close
to achieving our 90 percent discovery goal, according to our
current estimate of roughly 940 greater than one kilometer size
NEOs.
NASA currently funds four teams that operate eight ground-
based telescopes, of mostly one meter class, dedicated to
searching the skies and detecting NEOs. All NEO observations
that are collected are sent to an international clearinghouse
for small bodies. This organization is called the Minor Planet
Center. The Minor Planet Center determines the initial orbit
for any newly discovered NEO, so that observatories worldwide
may observe the object and confirm its existence. Once an NEO's
orbit has been determined, its potential for impacting the
Earth is assessed. Over 99 percent of the objects discovered by
our search efforts so far have no potential for Earth impacts
over many millennia, but a smaller number, which do, are tagged
potentially hazardous objects.
Now, more detailed and refined analysis of potentially
hazardous objects' orbits is then conducted by NASA's NEO
Program Office at the Jet Propulsion Laboratory. Observations
on potentially hazardous objects are also automatically
received, their orbits updated to determine the level of
probability of impacting the Earth in the next 100 to 200
years. The results of this analysis is constantly updated and
published on our NEO program website.
Now, the National Science Foundation's Arecibo Radio
Telescope, although it has no use in detecting NEOs, does
indeed provide us important observations for NEOs that pass
within 20 million miles of the Earth. Arecibo plays that
important role in refining the orbit, allowing us to obtain
information about the object's size, its shape, and its spin
rate. The only other facility currently being used by NASA for
routine planetary radar is NASA's own Goldstone facility, which
is part of our Deep Space Network. To date, no international
facilities are capable of performing this feat on a regular
basis.
Previous planetary spacecraft missions have not contributed
directly to detecting NEOs. NASA missions, such as the Near-
Earth Asteroid Rendezvous, Stardust, Deep Impact, and the
Japanese Hayabusa 1 missions, have all brought us fascinating
information on NEO composition, origin, and migration into the
inner solar system. The recently launched Dawn mission will
travel past the orbit of Mars and into the main asteroid belt,
observing both Vesta and Ceres, which are the largest objects
in that region. The asteroid belt has been shown to be the most
probable region where these objects are coming from, that we
now classify as NEOs.
In our report to Congress, requested by the 2005 Act, NASA
recommended that the current program be continued, and that we
would look at opportunities for potential dual use ground-based
telescopes, spacecraft, and also, partner with other agencies
as feasible. For example, we are actively planning to use the
Air Force Panoramic Survey Telescope and Rapid Response System,
also referred to as Pan-STARRS, after it becomes operational
with its very first telescope next year. When Pan-STARRS is
completed, and with its intended four telescope configuration,
by 2011, this system alone could discover up to 70 percent of
the potentially hazardous objects larger than 140 meters by
2020.
It is important to note that no significant NEO detection
efforts are currently conducted outside of NASA. However, there
is growing interest in international communities to contribute.
Most recently, the United Nations Committee on the Peaceful
Uses of Outer Space recently established a working group on
NEOs, to encourage more international work on the issue.
Other opportunities are beginning to materialize; that can
help us in these detection efforts. NASA's own Wide-Field
Infrared Survey Explorer, which is being developed for a late
2009 launch, is an astrophysics mission designed to map the
infrared sky. However, it is also capable of detecting many
asteroids, in which a portion will indeed be NEOs.
We have also been discussing with the Canadian Space Agency
how their upcoming Near-Earth Orbit Surveillance Satellite
(NEOSSat) mission would be able to contribute to NEO research
and detection, and other important missions like these are
being planned by the European Space Agency, the Japanese
Aerospace Exploration Agency, and for which we are in close
communications with.
In closing, let me again thank you for the opportunity to
appear at this hearing, and I would be happy to respond to any
of your questions.
[The prepared statement of Dr. Green follows:]
Prepared Statement of James L. Green
Mr. Chairman and Members of the Subcommittee, thank you for the
opportunity to appear today to discuss the goals and accomplishments of
NASA's Near-Earth Objects (NEOs) Observation Program. The
Subcommittee's invitation to testify identified a series of six
questions, and I have structured my testimony around your specific
concerns.
Question 1: Please describe NASA's NEO Program and the infrastructure
and operations in place to support the ongoing Survey (e.g., use of
observatories, survey processing and NEO databases, analysis of
identified objects, research, and sensor development)?
To achieve NASA's stated goal of finding over 90 percent of the
NEOs greater than one kilometer in diameter, the Agency's NEO
Observation Program currently funds four survey teams that operate
eight ground-based telescopes of mostly one meter class apertures
essentially dedicated to the NEO search effort. Two of the teams are
sponsored by the University of Arizona Lunar and Planetary Laboratory,
Tucson, Arizona, one by Lowell Observatory in Flagstaff, Arizona, and
one by the Massachusetts Institute of Technology Lincoln Laboratory.
Each team conducts independent operations for 14 to 20 nights per
month, as weather permits, avoiding approximately a week on either side
of the full moon when the sky is too bright to detect these extremely
dim objects from the ground.
All collected observations believed to be of known or previously
unknown NEOs are sent to the international ``clearinghouse'' for small
body observation data, the Minor Planet Center (MPC). The MPC maintains
the database of observations and orbits on all known small bodies
(asteroids, comets, dwarf planets, Kuiper Belt Objects (KBO), etc.) in
the Solar System under the sanction of the International Astronomical
Union. It is hosted by the Smithsonian Astrophysical Observatory's
Center for Astrophysics in Cambridge, Massachusetts, but is largely
funded by NASA. The MPC verifies and validates the observations by
determining if they are of an already known object (by comparing them
to the known orbits), or are indeed a new discovery. The MPC then
determines and publishes an initial orbit for the new discovery so that
observatories world-wide may look for the object and confirm its
existence. Sometimes it takes a few nights of additional observations
to adequately determine, or ``secure,'' the orbit of a new object so
that it may be regularly observed.
Once a new object's orbit is secured, its potential for impacting
the Earth is assessed. Well over 99 percent of all objects discovered
(which also include Main Belt Asteroids, comets, Trojans, Centaurs and
KBOs) have no potential for Earth impact even over many millennia, but
the small fraction which do are tagged as Potentially Hazardous Objects
(PHOs). More detailed and refined analysis of a PHO's orbit is
conducted by NASA's NEO Program Office at the Jet Propulsion Laboratory
in Pasadena, California, which also aids in coordinating the activities
and operations of NASA's NEO projects. Observations on PHOs are
automatically forwarded to JPL and their orbits updated with high
precision analysis to determine a level of probability of the object
impacting the Earth in the next 100 to 200 years. The results of this
analysis is constantly updated and published on the NEO Program website
at http://neo.jpl.nasa.gov.
Since the program's inception in 1998, NASA has funded over $30M in
NEO search efforts using funds from the Science Mission Directorate's
Research and Analysis program. To date, these efforts have found the
vast majority of the 724 one-kilometer Near Earth Asteroids and 64
Earth approaching comets now known, as well as the 4,128 known smaller
NEOs. At the current discovery rate, we will have found about 50 more
NEOs larger than one kilometer by the end of 2008, bringing us very
close to achieving our 90 percent goal, measured against the current
estimate of about 940 total one-kilometer objects. This work has
retired the majority of the risk that Earth could be struck by a large
asteroid in the foreseeable future.
Question 2: What roles do other U.S. Government institutions,
universities, private and not-for-profit organizations, and
international entities play in contributing to the NEO Survey and how
is NASA coordinating with these institutions?
As discussed above, NASA does not directly own or operate any of
the NEO Survey assets, but fully or partially funds several
universities and private institutions to conduct the necessary elements
of the survey using existing ground-based astronomical facilities. The
University of Arizona (UofA) operates most of the search telescopes,
either directly or in partnership with others. Two telescopes are
operated at Kitt Peak by the UofA Spacewatch project, while the UofA
Catalina Sky Survey operates two telescopes at Mt. Lemmon Observatory
and one in partnership with the Australian National Observatory at
Siding Spring Observatory in New South Wales, Australia, which is
currently our only southern hemisphere survey site. Lowell Observatory,
a private institution, operates a smaller search telescope outside
Flagstaff, Arizona. The remaining search team, funded by NASA at MIT/
Lincoln Laboratory, operates on two U.S. Air Force-owned one-meter
class telescopes at the Stallion Air Force Station on White Sands
Missile Range near Socorro, New Mexico. The Minor Planet Center is
operated by the Smithsonian Astrophysical Observatory using mostly NASA
funding, and the NEO Program Office is at the Jet Propulsion
Laboratory, managed by the California Institute of Technology.
No significant NEO detection efforts are currently conducted by the
international community. Less than two percent of NEOs detected in the
last ten years were found by systems other than those funded by NASA.
Currently, the only organized work in the international community
that is significant to the NEO Survey is the NEO Dynamics Site
(NEODyS), operated by the University of Pisa in Italy. NEODyS conducts
independent analysis on NEO orbits similar to that performed by NASA's
NEO Program Office at JPL. JPL and NEODyS constantly compare results
they obtain for PHO orbits and predicted impact probabilities. If the
results from one vary significantly from the other, they redo their
analyses until they can resolve the discrepancy. This work offers a
completely independent check of impact prediction results prior to an
announcement of any significant threat.
Also worth noting is the current significant role for new discovery
follow-up observations conducted world-wide by a dedicated amateur
astronomer community. Through its website, the MPC supplies position
information on newly discovered objects and solicits observations
needed to improve the orbit from anyone who may want to attempt the
work. Much of these follow-up observations are obtained by amateur
astronomer individuals or clubs with relatively sophisticated but
smaller telescope systems. However, once NASA moves the search to
objects much smaller than one kilometer, this work quickly becomes
beyond the capabilities of these amateur systems.
Coordination of efforts is largely voluntary through the use of
information published on the MPC and NEO Program Office websites. The
competitive nature of the grant program used to finance the search
teams has encouraged them to make improvements in their systems and
data processing to maintain their detection rates. This community meets
either in the U.S. or internationally annually, on average, to discuss
progress and improvements to the survey effort. In addition, last year
the United Nations Committee on the Peaceful uses of Outer Space
(COPUOS) established an Action Team on NEOs within its Scientific and
Technical Subcommittee to encourage more international work on this
issue. The Action Team is focused on identifying gaps in efforts and
coordination within the international community, as well as
recommending improvements. NASA is charter member of this new group.
Question 3: How do spacecraft missions to comets and asteroids, as well
as other scientific spacecraft, contribute to the NEO program?
Currently, spacecraft missions do not contribute to the detection
of NEOs. However, space missions do provide the most significant and
detailed information on what we know about the character and
composition of them. NASA Discovery missions such as the Near-Earth
Asteroid Rendezvous (NEAR), Stardust, Deep Impact, and the Japanese
Hyabusa mission have contributed important information to our
understanding of the origin of comets and asteroids, providing insight
on their evolution into the inner Solar System near the Earth, their
structure and physical properties, and their composition. The recently
launched Dawn mission will travel to the two largest objects in the
Main Belt of Asteroids--Vesta and the dwarf planet Ceres. This area of
the Solar System has been shown to be the region of origin for most of
the objects that now are near Earth, and the Dawn mission will tell us
many things about their nature. Other significant contributions by
spacecraft include studies by the Hubble Space Telescope, Spitzer,
Galileo, and other asteroid and comet flybys performed by several Solar
System exploration missions.
Not only are these data important to the development of concepts to
deal with any impact threat an NEO may pose, but they are also critical
to an understanding of the nature NEOs for possible destinations and
resources in our future exploration of the Solar System.
While NASA does not have any formal responsibility for the task of
mitigation, scientific missions such as Deep Impact and the current
Dawn mission to Vesta and Ceres provide information that may be
critical to planning an asteroid deflection. Likewise, many of the
systems and technologies that are being developed for exploration
missions are directly applicable to mitigation missions. These
capabilities are the hallmarks of a robust, space-faring nation.
Question 4: What is the Arecibo facility's role in the detection,
tracking, and characterization of Near-Earth Objects, and what
alternatives, if any, exist to carry out its role if the facility is
shut down? How do the capabilities of those alternatives compare to
those of the Arecibo facility?
The National Science Foundation's Arecibo Radio Telescope facility
has had no useful role in the detection of NEOs--its technical
characteristics make it incapable of conducting searches for these
relatively small and distant objects. However, once we know the
position of an object is accessible by a focused radar beam, Arecibo
plays an important role in the quick refinement of the orbit to a
precision not obtainable by other means, and for understanding the
object's size, shape and spin rate. Arecibo also aids in the detection
of possible binary objects, ( 15 percent of NEOs), which in turn
provides data that can be used to determine their mass. When an object
passes close enough to the Earth to achieve a measurable radar return
(about 20 million miles depending on the size), the use of radar is one
of several valuable tools for obtaining additional information about
these objects.
The only other facility currently being used by NASA for routine
planetary radar is NASA's own Goldstone facility, part of our Deep
Space Network (DSN) for communication with spacecraft on missions
beyond Earth's orbit. No international facility is capable of
performing this feat on a regular basis.
There are significant differences with the planetary radar
capability at Arecibo compared to Goldstone. The Goldstone radar is a
70-meter steerable dish, allowing it to access objects significantly
lower to the horizon than the more limited sky area accessible to the
limited pointing capability of the Arecibo radar. However, Arecibo is
twice as powerful as Goldstone and has a much larger (304 meter)
collection dish, which allows it to observe objects significantly
farther away than Goldstone.
Question 5: Will NASA's current NEO program satisfy the requirement
established in Sec. 321(d)(1) of the NASA Authorization Act of 2005,
and if not, what is NASA's plan for satisfying that requirement?
Although the current systems funded by NASA are capable of
detecting objects smaller than one kilometer in size, the objects must
come significantly closer to the Earth than a one kilometer object
needs to in order to be detected. It would take timescales much longer
than 15 years to observe 90 percent of these objects with the systems
we currently use.
As outlined in the report NASA submitted to Congress on March 7,
2007, pursuant to direction in section 321 of the NASA Authorization
Act of 2005 (P.L. 109-155), the Agency recommended that the current
survey program, funded at approximately $4M annually, be continued. In
addition, NASA indicated that the Agency would look for opportunities
using potential dual-use telescopes and spacecraft--and to partner with
other agencies as feasible--to attempt to achieve the legislated goal
within 15 years. Several alternatives as to how this might be
accomplished were presented and analyzed in the March 7 report.
However, due to current budget constraints, it is not possible for NASA
to initiate a new program. The costs for the alternative programs
ranged from $470M to in excess of $1.0B over 10 to 19 years, depending
on how aggressive of a timeline would be pursued.
The current NEO program is fully funded through 2012. In addition,
NASA is initiating plans to use other survey systems to increase the
survey's detection sensitivity and rates. For example, NASA has begun
providing funds to the Air Force Panoramic Survey Telescope and Rapid
Response System (Pan-STARRS) project so that it will be capable of
providing data on NEO detections after it starts operations on its
first telescope in the next year. If the Air Force continues to fund
this project to its intended four telescope configuration by 2010, this
system alone could discover over 70 percent of the potentially
hazardous objects larger than 140 meters by 2020. NASA is also
assessing the upgrades that must be instituted at the Minor Planet
Center to absorb the substantial increase in new detection data that
this system will provide.
Finally, NASA is also assessing what already planned spacecraft
might contribute to the detection effort. A leading example for
possible dual-use is the Wide-field Infrared Survey Explorer (WISE).
Currently being developed for a late 2009 launch for a six-month
astrophysics mission to map the infrared sky, the WISE instrument is
also capable of detecting many asteroids, of which a portion will be
NEOs. We are investigating improvements to the timeliness of the
spacecraft's data down-link and archival plans to increase its utility
for NEO detections, as well as a possible extended mission to double
the time available to detect these objects. The science community may
propose a NEO survey mission under the competitively-selected Discovery
program.
Question 6: What plans, policies, or protocols does NASA have in place
in the event that a previously unknown object on a near-term impact
trajectory is detected?
NASA has an NEO contingency notification plan to be utilized in the
very unlikely event an object is detected with significant probability
of impacting the Earth. The plan establishes procedures between the
detection sites, the Minor Planet Center, the NASA NEO Program Office
at JPL, and NASA Headquarters to first quickly verify and validate the
data and orbit on the object of interest, and then up-channel confirmed
information in a timely manner to the NASA Administrator. These
procedures were first exercised with the discovery of the object now
known as Apophis, which was found in December 2004 in a hazardous orbit
but determined to not have a significant probability of impacting the
Earth in the near-term. NASA will continue to refine this internal
contingency plan, and begin work with other U.S. Government agencies
and institutions when directed.
Again, thank you for the opportunity to testify today, and I look
forward to responding to any questions you may have.
Biography for James L. Green
Dr. Green received his Ph.D. in Space Physics from the University
of Iowa in 1979 and began working in the Magnetospheric Physics Branch
at NASA's Marshall Space Flight Center (MSFC) in 1980. At Marshall, Dr.
Green developed and managed the Space Physics Analysis Network, which
provided many scientists, all over the world, with rapid access to
data, other scientists, and specific NASA computer and information
resources. In addition, Dr. Green was a safety diver in the Neutral
Buoyancy tank making over 250 dives until he left MSFC in 1985.
From 1985 to 1992 he was the Head of the National Space Science
Data Center (NSSDC) at Goddard Space Flight Center (GSFC). The NSSDC is
NASA's largest space science data archive. In 1992 he became the Chief
of the Space Science Data Operations Office until 2005 when he became
the Chief of the Science Proposal Support Office. While at GSFC, Dr.
Green was a co-investigator and the Deputy Project Scientist on the
Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) mission.
From 1992 to 2000 he was also the Deputy Project Scientist for Mission
Operations and Data Analysis for the Global Geospace Science Missions
WIND and POLAR. He has written over 110 scientific articles in referred
journals involving various aspects of the Earth's and Jupiter's
magnetospheres and over 50 technical articles on various aspects of
data systems and computer networks.
In August 2006, Dr. Green became the Director of the Planetary
Science Division at NASA Headquarters. Over his career, Dr. Green has
received a number of awards. In 1988 he received the Arthur S. Flemming
award given for outstanding individual performance in the federal
government and was awarded Japan's Kotani Prize in 1996 in recognition
of his international science data management activities.
Chairman Udall. Thank you, Dr. Green. Dr. Pace.
STATEMENT OF DR. SCOTT PACE, ASSOCIATE ADMINISTRATOR, PROGRAM
ANALYSIS AND EVALUATION, NATIONAL AERONAUTICS AND SPACE
ADMINISTRATION (NASA)
Dr. Pace. Thank you, Mr. Chairman. Members of the
Committee, thank you for the opportunity.
I would like to review some of the findings and
recommendations of the report that we provided to the Congress
in response to the Authorization Act of 2005. The principal
findings of the report to Congress were the result of a study
led by my Office. The Study Team conducted an analysis of
alternatives, with inputs from several government agencies,
international organizations, and representatives of private
organizations. I think that we covered a wide spectrum of views
of the scientific and technical community in the effort.
NASA recommended that the existing Spaceguard survey
program continue, as currently planned. NASA would also take
advantage of opportunities using potential telescopes, such as
the Large Synoptic Survey Telescope, and the proposed Panoramic
Survey Telescope, otherwise known as Pan-STARRS, that you heard
mentioned, along with potential dual use spacecraft, some
partnerships with other agencies, as feasible, to make progress
toward achieving the legislative goal.
However, I have to say that due to budget constraints, NASA
cannot initiate a new program beyond Spaceguard at this time,
and however, as also was noted, that NASA, it is fair to say,
would be pleased to implement a more aggressive Near-Earth
Object program if, in fact, so directed by the President and
Congress. Given the constrained resources and strategic
objectives that the agency has already been tasked with, I
would have to say that NASA cannot place a new NEO program
above current scientific and exploration missions. But I
imagine that will be the subject of dialog and discussion with
you, and see how we can move forward.
The goal of finding 90 percent of potentially hazardous
objects 140 meters in diameter and larger is one to two orders
of magnitude more technically challenging than the existing
Spaceguard mission. To reach the goal within 10 to 15 years
would require at least one new dedicated ground or space
observatory, and we can share with other folks, but to really
hit the goal, you need a dedicated facility.
Cataloging the number of total objects, say 100,000, at the
rate they would be discovered, around 30 to 50 a day, would
require a new tracking and data management infrastructure,
whose ongoing operation may constitute a sizable portion of the
total cost. A delay of five to 10 years in achieving the
legislation goal, we think, carries little additional risk when
the impact interval for 140 meter objects is about once every
5,000 years. We think there is time to do the survey right.
This rate of impact indicates the system may need to operate,
conducting searches, tracking objects, for an extended period
of time before identifying a credible threat, and I would like
to describe really three periods in that process.
Today, we know where a few 140 meter objects are, but we
know little about when or if they will impact. We are ignorant.
For the initial 10 to 20 years the survey is progressing, the
average warning time will rise, the unwarned impact risk will
gradually decline, and during this period, potentially decades
of warning will become likely.
After 10 to 20 years of the survey, a steady state period
will be reached, where unwarned impacts of potentially
hazardous objects would be highly unlikely. Centuries of
warning time become possible in a steady state period.
The NASA identified, in its report, an exemplar NEO survey
program, with estimates for its architectural costs that, if
funded, could achieve the specified goal of surveying 90
percent of potentially hazardous objects by the end of 2020.
This would occur by constructing or funding a dedicated survey
asset, combined with NASA partnerships with other agencies on
future optical ground-based observatories. Details of the
exemplar program were provided in our report, and again, we
would be happy to discuss them.
I want to caution, however, that the budget estimates in
the report are what we call architecture costs, and a lot more
rigorous analysis would be needed before a program to be
assessed for implementation. So, more work needs to be done on
those cost estimates.
Finally, the current NEO Spaceguard survey program, really
without any augmentation, would not be able to satisfy the
requirements of the Authorization Act. In the Act right now,
the requirements of the survey program are to find only NEOs
greater than a kilometer in diameter, and therefore, if we
focused on things smaller than that, 140 meters, it would
require additional effort. Without major augmentation, NASA
estimates that we could detect 14 percent of the 140 meter or
larger potentially hazardous objects by 2020.
In our cooperative efforts with Air Force, the Pan-STARRS
program, it would be capable of providing data on NEO
detections after operations start. We think that this system
alone could discover about 70 percent of potentially hazardous
objects larger than 140 meters by 2020. So, we think there are
some promising approaches.
While NASA does not have any formal responsibility for the
task of NEO mitigation, as mentioned, scientific missions such
as Deep Impact and Dawn provide information that may be
critical to planning and asteroid deflection, and likewise,
many of the systems and technologies that are being developed
for exploration are directly applicable to mitigation missions.
These capabilities are the hallmarks of a robust and
spacefaring nation, capable of the many tasks that may be
assigned to it.
Thank you, Mr. Chairman. I would be pleased to respond to
any questions.
[The prepared statement of Dr. Pace follows:]
Prepared Statement of Scott Pace
Mr. Chairman and Members of the Subcommittee, thank you for the
opportunity to appear today to review the findings and recommendations
of NASA's report to Congress in response to the NASA Authorization Act
of 2005 (P.L. 109-155). Below, I have addressed the questions posed by
this Subcommittee in your invitation to testify.
Question #1: What were the principal findings and recommendations of
NASA's Near-Earth Object Survey and Deflection Analysis of
Alternatives: Report to Congress, March 2007, and what was the basis
for those findings and recommendations?
The principal findings were the result of a study team, led by
NASA's Office of Program Analysis and Evaluation (PA&E) that conducted
an analysis of alternatives with inputs from several other U.S.
Government agencies, international organizations, and representatives
of private organizations. The team developed a range of possible
options from public and private sources and then analyzed their
capabilities and levels of performance including costs, development
schedules, and technical risks. In order to meet the congressional goal
of completing the survey by 2020, the study team assumed primary
project elements would have started their development by October 1,
2007.
NASA recommended that the existing ``Spaceguard Survey'' program
continue as currently planned, and that NASA would also take advantage
of opportunities using potential dual-use telescopes\1\ and
spacecraft--and partner with other agencies as feasible--to make
progress toward achieving the legislative goal of discovering 90
percent of all potentially hazardous objects 140 meters in mean
diameter and greater. However, due to budget constraints, NASA cannot
initiate a new program beyond the Spaceguard Survey program at this
time.
---------------------------------------------------------------------------
\1\ The proposed Large Synoptic Survey Telescope (LSST) and
Panoramic Survey Telescope And the Rapid Response System (Pan-STARRS)
present possible future opportunities, if they are funded by other
agencies. Another possible opportunity would be the Lowell Discovery
Channel Telescope (DCT), but its contribution would be less than LSST
or Pan-STARRS.
---------------------------------------------------------------------------
NASA would be pleased to implement a more aggressive NEO program if
so directed by the President and Congress. However, given the
constrained resources and strategic objectives the Agency has already
been tasked with, NASA cannot place a new NEO program above current
scientific and exploration missions.
For ease of following the findings and recommendations, simplified
definitions are as follows:
``Detection'' is the act of finding the objects;
``Tracking'' is the act of determining their orbits;
``Characterization'' is the act of determining their
physical properties;
``Cataloging'' is the act of maintaining a data base
of the orbits and physical properties of known objects and
predicting potential impacts with the Earth; and
``Mitigation'' is the act of deflecting, destroying,
or reducing the impact consequences of a specific object that
is predicted to strike the Earth.
Key Findings for the Survey Program
The goal of the Survey Program should be modified to
detect, track, catalogue, and characterize, by the end of 2020,
90 percent of all Potentially Hazardous Objects (PHOs) greater
than 140 meters whose orbits pass within 0.05 AU (Astronomical
Units) of the Earth's orbit (as opposed to surveying for all
NEOs).
The Agency could achieve the specified goal of
surveying for 90 percent of the potentially hazardous NEOs by
the end of 2020 by partnering with other government agencies on
potential future optical ground-based observatories and
building a dedicated NE0 survey asset, assuming the partners'
potential ground assets come online by 2010 and 2014, and a
dedicated asset by 2015.
Together, the two observatories potentially to be
developed by other government agencies could complete 83
percent of the survey by 2020 if observing time at these
observatories is shared with NASA's NE0 Survey Program.
New space-based infrared systems, combined with
shared ground-based assets, could reduce the overall time to
reach the 90 percent goal by at least three years. Space
systems have additional benefits as well as costs and risks
compared to ground-based alternatives.
Radar systems cannot contribute to the search for
potentially hazardous objects, but may be used to rapidly
refine tracking and to determine object sizes for a few NEOs of
potentially high interest.
Determining a NEO's mass and orbit is required to
determine whether it represents a potential threat and to
provide required information for most alternatives to mitigate
such a threat. Beyond these parameters, characterization
requirements and capabilities are tied directly to the
mitigation strategy selected.
Key Findings for Diverting a Potentially Hazardous Object (PHO)
The study team assessed a series of approaches that could be used
to divert a NEO potentially on a collision course with Earth. Nuclear
explosives, as well as non-nuclear options, were assessed.
Nuclear standoff explosions are assessed to be 10-100
times more effective than the non-nuclear alternatives analyzed
in this study. Other techniques involving the surface or
subsurface use of nuclear explosives may be more efficient, but
they run an increased risk of fracturing the target NEO. They
also carry higher development and operations risks.
Non-nuclear kinetic impactors are the most mature
approach and could be used in some deflection/mitigation
scenarios, especially for NEOs that consist of a single small,
solid body.
``Slow push'' mitigation techniques are the most
expensive, have the lowest level of technical readiness, and
their ability to both travel to and divert a threatening NEO
would be limited unless mission durations of many years to
decades are possible.
30-80 percent of potentially hazardous NEOs are in
orbits that are beyond the capability of current or planned
launch systems. Therefore, planetary gravity assist swing-by
trajectories or on-orbit assembly of modular propulsion systems
may be needed to augment launch vehicle performance, if these
objects need to be deflected.
Question #2: How were the cost estimates and technical options
contained in the report arrived at, and was any independent assessment
of the cost estimates and technical options conducted?
Technical Options
The technical options contained in the report were developed
through a systematic exploration of the trade space for feasible
alternatives, followed by a conceptual design of selected options.
Concepts were selected to represent the available range of cost,
performance, and acceptable technical risk to complete the detection,
tracking, cataloguing, and characterization missions. Concepts were
based on historical and existing projects and on white papers presented
at a NASA-sponsored workshop of national experts.
Trade trees were developed to describe the technical options. The
detection and tracking trade tree consisted of existing and new ground-
and space-based observatories operating in the visible and infrared
spectra; ground based radars were considered for tracking. The
characterization trade tree contained existing, proposed, and new
remote and in-situ observing assets. Cataloguing considered a range of
operations and data management options based on historical, proposed,
and new information systems.
Cost Estimates
Life cycle costs were calculated as the total architecture cost in
fiscal year 2006 billions of dollars including development, production,
deployment, and operation of the alternatives. Life cycle costs for the
detection, tracking, and data management options were calculated both
for a fixed period (through 2020) and until the objective of
cataloguing 90 percent of specified threats was complete. For some
options that rely on existing systems or available technology,
operational costs were much higher than the development costs over the
15-20 year life cycle. In order to meet the Congressional goal of
completing the survey by 2020, the study team assumed primary project
elements would have started their development by October 1, 2007.
For space-based systems, the total life cycle costs included
estimated costs for program management, systems engineering, mission
assurance, launch vehicle, spacecraft, scientific instruments, mission
specific ground data systems, mission operations, and data analysis.
Ground-based systems included the cost of development, production, and
operations. Operations costs were calculated over either the survey
period for detection, tracking, and cataloguing missions or the
predicted duration of characterization missions.
The cost estimates for the space vehicles relied on multiple
methods including historical analogies and prior cost-estimating
experience. Cost-risk analyses were performed using these data as
inputs and assumed that every cost element could be represented by
statistical characteristics such as mean, standard deviation, and mode.
A cumulative probability distribution of total cost was generated for
this analysis by combining cost distributions from the different cost
elements, and costs were estimated at the 65 percent cost confidence
level when applicable. Programmatic costs were based on historical
actual costs and applied as a percentage of the space vehicle costs.
Launch vehicle costs were based on recent, publicly released estimates
for commercial launch vehicles.
Ground-based observatory costs were based on reported expenses for
currently operating systems or based on estimates for systems currently
in development. For several ground based options, concepts of
operations postulated utilizing (sharing) data that would be collected
on existing or planned systems without materially affecting the primary
mission of these systems. For these systems, it was assumed that the
NEO program would fund only a small portion (or none) of the
development costs, but that an equitable portion of the annual
operations costs would be funded by NASA. In cases where the ground
based systems were expected to be copies of systems that are currently
in development, only the production and operation costs of the NASA-
acquired systems were considered--substantially reducing their
development costs and cost-risk.
Although multiple cost-estimating methodologies, databases, and
organizations were used, truly independent cost estimates were not
generated as these are typically not within the scope of a conceptual,
architecture-level study. Likewise, assessments of the technical
options were carried out using an experienced team of personnel from
several organizations, but fully separate evaluations of the concepts
were not performed.
Question #3: What is the ``recommended option and proposed budget to
carry out the Survey program pursuant to the recommended option,'' as
called for in Sec. 321(d)(2)?
NASA recommended that the existing ``Spaceguard Survey'' program
continue as currently planned, and that NASA would also take advantage
of opportunities using potential dual-use telescopes\2\ and spacecraft-
and partner with other agencies as feasible-to make progress toward
achieving the legislative goal of discovering 90 percent of all
potentially hazardous objects 140 meters and greater.
---------------------------------------------------------------------------
\2\ The proposed Large Synoptic Survey Telescope (LSST) and
Panoramic Survey Telescope And the Rapid Response System (Pan-STARRS)
represent possible future opportunities, if they are funded by other
agencies. Another possible opportunity would be the Lowell Discovery
Channel Telescope (DCT), but its contribution would be less than LSST
or Pan-STARRS.
---------------------------------------------------------------------------
The goal of finding 90 percent of potentially hazardous objects 140
meters and larger is one to two orders of magnitude more technically
challenging than the Spaceguard mission. To reach this goal within 10-
15 years requires at least one new dedicated ground or space
observatory.
Cataloging the number of total number of objects--approximately
100,000--at the rate they would be discovered, which is between 30 and
50 per day, requires a new tracking and data management infrastructure
whose ongoing operations may constitute a sizable portion of total
costs.
A delay (e.g., 5-10 years) in achieving the legislative goal
carries little additional risk when the impact interval for 140m
objects is about once every 5,000 years. This rate of impacts also
indicates that the system may need to operate (searching and tracking)
for an extended period before identifying a credible threat. There are
three epochs to the problem of detection and tracking:
Now: We know where few 140m objects are and when/if
they will impact.
Initial 10-20 years of the survey: Average warning
time will rise, unwarned impact risk gradually decline. Decades
of warning become likely.
Steady-state: After 10-20 years of the survey,
unwarned impacts of 140m objects would be highly unlikely.
Centuries of warning become possible.
Currently, NASA carries out the ``Spaceguard Survey'' to find NEOs
greater than 1 kilometer in diameter, and this program is currently
budgeted at $4.1 million per year for FY 2006 through FY 2012. We also
have benefited from knowledge gained in our Discovery space mission
series, such as the Near-Earth Asteroid Rendezvous (NEAR), Deep Impact,
and Stardust missions that have expanded our knowledge of near-Earth
asteroids and comets. Participation by NASA in international
collaborations such as Japan's Hayabusa mission to the NEO ``Itokawa''
also greatly benefited our understanding of these objects. NASA's Dawn
mission, launched on September 27, 2007, will increase our
understanding of the two largest known main belt asteroids, Ceres and
Vesta, between the planets Mars and Jupiter. NASA conducts survey
programs on many celestial objects--the existing Spaceguard program for
NEOs, surveys for Kuiper Belt Objects, the search for extra-solar
planets, and other objects of interest such as black holes to
understand the origins of our universe. The science community could
propose such a NEO survey mission under the competitively-selected
Discovery program.
NASA also identified an exemplar NEO Survey Program and estimates
for its architectural costs that, if funded, could have achieved the
specified goal of surveying 90 percent of the PHOs by the end of 2020
by constructing or funding a dedicated survey asset combined with NASA
partnerships with other government agencies on potential future optical
ground-based observatories: the Panoramic Survey Telescope and Rapid
Response System (Pan-STARRS-4 or PS4) and the Large Synoptic Survey
Telescope (LSST). Details of the exemplar program were provided in
NASA's report. Note that budget estimates in the report are rough
``architecture costs'' and would require more rigorous analysis before
a program could be assessed for implementation.
Question #4: Will NASA's current NEO program satisfy the requirement
established in Sec. 321(d)(1) of the NASA Authorization Act of 2005,
and if not, what is NASA's plan for satisfying that requirement?
The current NASA NEO ``Spaceguard Survey'' program, without any
augmentation, would not be able to satisfy the requirements outlined in
section 321(d)(1) of the NASA Authorization Act for 2005. The
requirements for the Spaceguard Survey program are to find only NEOs
greater than one kilometer in diameter, and its funding is currently
budgeted at $4.1 million per year. NASA estimates that the current
program, if continued without major augmentation, would detect 14
percent of the 140 meters or larger potentially hazardous objects by
the end of 2020. However, NASA is initiating plans to use other survey
systems to increase the survey's detection sensitivity and rates. For
example, NASA has begun providing funds to the Air Force Panoramic
Survey Telescope and Rapid Response System (Pan-STARRS) project so that
it will be capable of providing data on NEO detections after it starts
operations on its first telescope in the next year. If the Air Force
continues to fund this project to its intended four telescope
configuration by 2010, this system alone could discover over 70 percent
of the potentially hazardous objects larger than 140 meters by 2020.
NASA recommended that the existing ``Spaceguard Survey'' program
continue as currently planned, and that NASA would also take advantage
of opportunities using potential dual-use telescopes and spacecraft--
and partner with other agencies as feasible--to make progress toward
achieving the legislative goal of discovering 90 percent of all
potentially hazardous objects 140 meters and greater.
NASA would be pleased to implement a more aggressive NEO program,
if so directed by the President and Congress. However, given the
constrained resources and strategic objectives the Agency has already
been tasked with, NASA cannot place a new NEO program above current
scientific and exploration missions.
Question #5: How is progress on meeting the requirements of Section 321
being measured and monitored?
Survey performance is tracked continuously by the NEO Program
Office at JPL, and reported monthly on NASA's NEO Program website at
http://neo.jpl.nasa.gov/stats. This database shows the performance of
each survey team and reports the number of NEOs, including Earth
approaching comets, found each month by orbit and size (larger or
smaller than one kilometer) class. It also breaks out the objects which
are potentially hazardous by size class. Specific orbit and estimated
size information for each discovered NEO can also been found on the
website, as well as probability of impact statistics for Potentially
Hazardous Objects.
The discovery statistics information is rolled up each year and
reported by the Science Mission Directorate as part of our Government
Performance Reporting Act (GPRA) submittal.
In closing, NASA recommends that the existing ``Safeguard Survey''
program continue, as planned, and that the Agency take advantage of
opportunities using potential dual-use telescopes and spacecraft, as
well as partner with other agencies, to make progress toward achieving
the legislative goal.
Mr. Chairman, I would be pleased to respond to any questions you or
the other Members of the Subcommittee may have.
Biography for Scott Pace
Scott Pace is the Associate Administrator for Program Analysis and
Evaluation at NASA. In this capacity, he is responsible for providing
objective studies and analyses in support of policy, program, and
budget decisions by the NASA Administrator. He previously served as
Chief Technologist for Space Communications in NASA's Office of Space
Operations where he was responsible for advising senior NASA management
on issues related to space-based information systems. He participated
in the negotiations that resulted in the 2004 GPS-Galileo Agreement
between the United States and the European Commission. Pace also
previously served as the Deputy Chief of Staff to NASA Administrator
Sean O'Keefe. His primary areas of responsibility included oversight of
the President's Management Agenda in Human Capital, Competitive
Sourcing, Expanding e-Government, Financial Management, and Integrating
Budget and Performance.
Prior to NASA, Pace was the Assistant Director for Space and
Aeronautics in the White House Office of Science and Technology Policy
(OSTP). There he was responsible for space and aviation-related issues
and coordination of civil and commercial space issues through the Space
Policy Coordinating Committee of the National Security Council. Pace
served on the Bush-Cheney Transition Team for NASA and the National
Science Foundation.
Prior to his White House appointment, Pace worked for the RAND
Corporation's Science and Technology Policy Institute (STPI)--a
federally funded research and development center for the Office of
Science and Technology Policy. In addition to his extensive research
into space policy, technology policy, and international competitiveness
at RAND, Pace also was a key member of a successful international
effort to preserve radio navigation satellite spectrum at the 1997
World Radiocommunication Conference (WRC97) and the addition of new
spectrum for satellite navigation at WRC-2000. He also was a member of
the Department of Defense Senior Review Group on Commercial Remote
Sensing and the National Research Council's Committee on Earth
Sciences.
From 1990 to 1993, Pace served as the Deputy Director and Acting
Director of the Office of Space Commerce (OSC), in the Office of the
Deputy Secretary of the Department of Commerce. Among his many
responsibilities at OSC, Pace coordinated space policy issues across
the Department and participated in efforts affecting export controls
for space technologies; space trade negotiations with Japan, Russia,
China, and Europe; the licensing process for private remote sensing
systems; missile proliferation; and the U.S. space industrial base.
Pace received a Bachelor of science degree in physics from Harvey
Mudd College in 1980; Master of science degrees in aeronautics and
astronautics and technology and policy from the Massachusetts Institute
of Technology in 1982; and a doctorate in policy analysis from the RAND
Graduate School in 1989. His dissertation was entitled ``U.S. Access to
Space: Launch Vehicle Choices for 1990-2010.''
Chairman Udall. Thank you, Dr. Pace. Dr. Yeomans.
STATEMENT OF DR. DONALD K. YEOMANS, MANAGER, NEAR-EARTH OBJECT
PROGRAM OFFICE, JET PROPULSION LABORATORY
Dr. Yeomans. Mr. Chairman and Members of the Subcommittee,
thank you for the opportunity to appear today.
Chairman Udall. Dr. Yeomans, I think you should turn on
your microphone, if you can.
Dr. Yeomans. Thank you for the opportunity to appear today
to discuss the potential threats of Near-Earth Objects,
progress toward meeting the discovery goal articulated in the
NASA Authorization Act of 2005, the role of the Arecibo
Planetary Radar within the Near-Earth Object Program, and the
response options available if a Near-Earth Object is found to
be on an Earth-threatening trajectory.
Near-Earth objects are comets and asteroids that can pass
within about 45 million kilometers of the Earth's orbit. While
some showy naked eye comets may occasionally pass close to
Earth, it is the difficult to find, but the far more numerous
asteroids are of the most concern in near-Earth space today.
About one-fifth of the near-Earth asteroids can approach the
Earth's orbit even closer, to within seven and a half million
kilometers, and these so-called potentially hazardous asteroids
are of most concern for near-term hazard avoidance.
As part of the NASA Authorization Act of 2005, NASA was
asked to consider options for extending the search down to
objects as small as 140 meters in diameter, and to find and
catalog them within 15 years of the Act becoming law. By
finding and cataloging 90 percent of this population of
potentially hazardous asteroids, the statistical or actuarial
risk to Earth from potentially hazardous asteroids of all sizes
would be reduced by 99 percent from pre-survey levels. We can
speak of risk reduction in this case, because once an object is
discovered and cataloged, its future motion can accurately be
predicted, and in the unlikely case where it does threaten
Earth, there would be sufficient time to deflect it, thus
saving the enormous costs due to fatalities and/or
infrastructure damage.
According to a 2003 NASA Near-Earth Object science
definition team study that undertook a cost-benefit analysis
for the discovery of potentially hazardous asteroids, the risk
reduction accruing from this next generation potentially
hazardous asteroid search would pay for itself in the first
year of operations.
While an impact by a 140 meter sized object would not
generate global physical consequences, its impact energy would
still be about 100 megatons of TNT explosive, and the
likelihood of one of these impacts is 100 times greater than an
impact by one of the less numerous one kilometer size
potentially hazardous asteroids.
With regard to the uncertainty associated with threats from
potentially hazardous asteroids, the largest factor, by far, is
the large number of undiscovered objects in the size ranges
that are small enough to be very numerous, yet large enough to
easily penetrate the Earth's atmosphere. For example, we have
only discovered about four percent of the 20,000 potentially
hazardous asteroids larger than 140 meters, and less than one
percent of the 200,000 objects larger than 50 meters.
The solution to this uncertainty is to continue and
hopefully accelerate the search for potentially hazardous
asteroids. Once we find the vast majority of them, they can be
tracked, cataloged, and then ruled out or in as threats during
the next 100 years or so.
The current NASA Near-Earth Object goal is focused upon the
discovery and tracking of objects one kilometer in diameter and
larger. It is not realistic to expect the current survey
program, with its modestly sized telescopes, to efficiently
find 140 meter sized objects that are nearly 50 times fainter
compared to the one kilometer sized objects at the same
distance and with the same reflectivity.
Because all potentially hazardous asteroids do eventually
come very close to the Earth, the current ongoing surveys could
complete the goal outlined in the 2005 NASA Authorization Act,
but it would likely take over a century to do so. We simply
cannot afford to wait that long.
At least two next generation ground-based wide-field search
telescope surveys are in development. Pan-STARRS is under
development at the University of Hawaii, with Air Force
funding, and will have one of its 1.8 meter telescopes
operational in Hawaii in early 2008. If the planned four
telescope version of Pan-STARRS is completed by 2010, it could
help reach the goal by about 2040.
Likewise, the 8.4 meter aperture LSST telescope that is
under development with funding from NSF, DOE, and other
partners, could help reach the goal by about 2034, if it began
operation in 2014.
If we assume that both the Pan-STARRS four telescope system
and the LSST operate in their planned shared mode, which
includes many observations unrelated to potentially hazardous
asteroids, then the goal could be reached by about 2026. The
potentially hazardous asteroid discovery rate could be
increased beyond the results shown in the NASA report, if the
observing times and sequences of Pan-STARRS and LSST were
optimized for potentially hazardous asteroid observations.
Both positional data for potentially hazardous asteroid
orbit determination and trajectory predictions are based upon
optical, plane-of-sky observations. Because the radars provide
line of sight, velocity, and range information to about one
millimeter per second and 10 meter accuracy levels, this data,
when used in conjunction with the optical data, provide a
secure orbit and trajectory far more rapidly than if only
optical data are available. With only a limited amount of
optical data to work with, the orbit of a newly discovered
potentially hazardous asteroid is often not accurate enough to
immediately rule out a future Earth impact.
However, with radar data in hand, the orbit of a newly
discovered potentially hazardous asteroid can be quickly and
more precisely determined, its motion accurately projected far
into the future, and future impact possibilities can usually be
quickly ruled out. Likewise, in the rare situation when an
object is actually on an Earth-impacting trajectory, radar
observations will be critical in quickly identifying this case.
A number of existing technologies can deflect an Earth-
threatening asteroid if there is time. The primary goal of the
potentially hazardous asteroid survey programs is to discover
them early and provide the necessary time. An asteroid that is
predicted to hit Earth would require a change in its velocity
of only three millimeters per second, if this impulse were
applied 20 years in advance of the impact itself. The key to a
successful deflection is having sufficient time to carry it
out, whether it is a slow, gentle drag of a gravity tractor, or
the more impulsive shove from an impacting spacecraft or
explosive device. In either case, the verification process will
be required to ensure the deflection maneuver was successful,
and to ensure the object's subsequent motion would not put it
on yet another Earth-impacting trajectory.
While suitable deflection technologies exist, none of them
can be effective if we are taken by surprise. It is the
aggressive survey efforts and robust radar systems that must
ensure that the vast majority of potentially hazardous objects
are discovered and tracked well in advance of any Earth-
threatening encounters.
The first three steps in any asteroid mitigation process
are find them early, find them early, and find them early.
Thank you.
[The prepared statement of Dr. Yeomans follows:]
Prepared Statement of Donald K. Yeomans
Mr. Chairman and Members of the Subcommittee, thank you for the
opportunity to appear today to discuss the potential threats of near-
Earth objects (NEOs), our progress toward meeting the discovery goal
articulated in the NASA Authorization Act of 2005, the role of the
Arecibo planetary radar within the NEO program and the response options
available if a NEO is found to be on an Earth impacting trajectory.
The Near-Earth Object Population: When the Earth was young, frequent
collisions of comets and asteroids likely delivered much of the water
and carbon-based molecules that allowed life to form, and once life did
form, subsequent collisions may have punctuated the evolutionary
process and allowed only the most adaptable species to progress
further. We may owe our very existence atop the world's food chain to
these objects. As the Earth's closest neighbors (some pass within the
Moon's distance), these icy comets and rocky asteroids have been termed
near-Earth objects. Their proximity to Earth presents an opportunity to
utilize their vast metal, mineral and water ice resources for future
space structures and habitats. Their water resources can be broken down
into hydrogen and oxygen--the most efficient form of rocket fuel. These
near-Earth objects may one day be the resources, fueling stations and
watering holes for human interplanetary exploration. While these
objects are of extraordinary scientific interest, likely enabled the
origin of life itself, and may loom large for the future development of
space exploration, their proximity to Earth also presents a potential
horrific threat should a relatively large near-Earth object once again
strike Earth without warning.
Potentially Hazardous Asteroids: Near-Earth objects are comets and
asteroids that can pass within 45 million kilometers of the Earth's
orbit. While some showy, naked-eye comets may occasionally pass close
to Earth, it is the difficult to find (but far more numerous asteroids)
that are of most concern in near-Earth space today. About one fifth of
the near-Earth asteroids can approach the Earth's orbit even closer (to
within 7.5 million kilometers), and these so-called potentially
hazardous asteroids (PHAs) are of most concern for near-term hazard
avoidance.
Celestial debris hits the Earth all the time, but the vast majority
of it is so small that it does not survive passage through the Earth's
atmosphere. The debris is created over millions of years, as asteroids
inevitably run into each other, producing smaller fragments, which
themselves collide yielding even more debris. Over time, the fragments
and debris spread out, and some of it migrates into Earth approaching
orbits. The Earth is pummeled with more than 100 tons of impacting
material each day but almost all of it is far too small to cause
anything other than a harmless meteor, or shooting star, or the
occasional fireball event. Larger objects are less numerous than
smaller objects and hit the Earth less often. While a basketball-sized
object strikes the Earth's atmosphere daily, larger car-sized impactors
hit only a few times each year, and even these generally break up into
smaller pieces as they streak through the atmosphere. Occasionally a
fragment of a larger impactor will reach the Earth's surface--one such
hit may have occurred less than two months ago when a reported asteroid
fragment perhaps one meter in diameter struck in southern Peru creating
a 13-meter crater near Lake Titicaca.
Larger impactors with diameters in the 50 to 140 meter range, while
they do not usually impact the ground, can result in damaging air
blasts that cause significant destruction. For example, on June 30,
1908, an impactor with a diameter of about 50 meters detonated over the
Tunguska region of Siberia and leveled trees for 2,000 square
kilometers. Its impact energy has been estimated at about 10 million
tons of TNT explosives (10 megatons or 10 MT), comparable in energy
with a modern nuclear weapon. Roughly speaking, PHAs that have
diameters larger than 140m can punch through the Earth's atmosphere and
cause regional damage if they strike land or create a harmful tsunami
should they impact into an ocean. There are thought to be about 20,000
PHAs in this size range, each with a potential impact energy of 100 MT
or more. On average, one of these objects would be expected to strike
Earth every 5,000 years and therefore would have a one percent
probability of impact in the next 50 years. Although their mean impact
frequency would be about once every 500,000 years, PHAs larger than a
kilometer in diameter could cause global consequences due to not only
the extraordinary blast itself (50,000 MT) but also the dust and debris
thrown into the air, and the subsequent firestorms and acid rain. The
extinction of the dinosaurs and a sizable fraction of the Earth's other
species some 65 million years ago is thought to be due to an impactor
with a diameter of about 10 kilometers that created an impact energy of
as much as 50 million MT. Over very long time intervals, PHAs with
diameters greater than one kilometer are statistically the most
dangerous objects because their impacts would cause global
consequences.
NASA Responses to the PHA Issues: In 1998, before the Subcommittee on
Space and Aeronautics, a NASA representative outlined the goal to
discover and catalog 90 percent of the NEOs larger than one kilometer
by the end of 2008. There are currently thought to be over 900 of these
objects, and about 80 percent of them have already been found and
cataloged. Roughly the same percentage of PHAs in this size range has
also been found. When this goal has been reached, 90 percent of the
global risk from PHAs would be retired. Almost all of these discoveries
have come by way of NASA supported search programs.
As part of the NASA Authorization Act of 2005, NASA was asked to
consider options for extending the search down to objects as small as
140 meters in diameter, and to find and catalog them within 15 years of
the Act becoming law (i.e., by the end of 2020). By finding and
cataloging 90 percent of this population of PHAs, the statistical or
actuarial risk to Earth from PHAs of all sizes would be reduced by 99
percent from pre-survey levels. We can speak of risk reduction in this
case because once an object is discovered and cataloged, its future
motion can accurately be predicted and, in the unlikely case where it
does threaten Earth, there would be sufficient time to deflect it, thus
saving the enormous costs due to fatalities and/or infrastructure
damage. According to a 2003 NASA NEO Science Definition Team study that
undertook a cost/benefit analysis for the discovery of PHAs, the risk
reduction accruing from this next generation PHA search would pay for
itself in the first year of operations. While an impact by a 140 meter-
sized object would not generate global physical consequences, its
impact energy would still be about 100 MT, and the likelihood of one of
these impacts is 100 times greater than an impact by one of the less
numerous one kilometer-sized PHAs.
With regard to the uncertainty associated with threats from PHAs,
the largest factor, by far, is the large number of undiscovered objects
in the size ranges that are small enough to be very numerous but large
enough to easily penetrate the Earth's atmosphere. For example, we have
discovered only about four percent of the 20,000 PHAs larger than 140
meters and less than one percent of the 200,000 objects larger than 50
meters. The solution to this uncertainty is to continue and hopefully
accelerate the search for PHAs. Once we find the vast majority of them,
they can be tracked, cataloged and then ruled out (or in) as threats
during the next 100 years or so. This process can continue year after
year so the window of safety is always at least 100 years. There are
other, less significant, uncertainties dealing with the refinement of a
particular object's size, mass and structure as well as the dynamical
model that is used to accurately predict the object's motion over 100
year time scales. For example, over long time intervals, the minute
pressure of sunlight and its thermal re-radiation can significantly
affect a PHA's motion. For a select number of Earth approaching
objects, we will need the use of the planetary radars, or possibly
rendezvous spacecraft missions, to better understand their sizes,
shapes, masses, surface properties, and possible binary natures.
The Next Generation of Search: As noted, the current NASA NEO goal is
focused upon the discovery and tracking of objects one kilometer in
diameter and larger. It is not realistic to expect the current survey
program, with its modestly sized telescopes, to efficiently find the
140 meter-sized objects that are nearly 50 times fainter compared to a
one kilometer-sized object at the same distance and with the same
reflectivity. Because all PHAs do eventually come very close to the
Earth, the current ongoing surveys could complete the goal outlined in
the 2005 NASA Authorization Act but it would likely take over a century
to do so. We cannot afford to wait that long.
In the report to Congress requested by the 2005 NASA Authorization
Act, several options were outlined, both ground-based and space-based,
that could meet the goal of finding 90 percent of the PHAs larger than
140 meters by the end of 2020. For example, a one-meter aperture
infrared telescope in a heliocentric orbit near Venus could do the job
three years early. Within this report, NASA noted that it did not have
the resources to carry out a survey option that would meet the 2020
deadline set by the 2005 Act and that, in an attempt to achieve the
legislative goal by the end of 2020, it would seek to continue the
current survey programs and look for opportunities to use dual use
telescope facilities and spacecraft along with partnering with other
agencies as feasible.
At least two next-generation, ground-based, wide-field search
telescope surveys are in development. The Panoramic Survey Telescope
and Rapid Response System (Pan-STARRS), under development at the
University of Hawaii with Air Force funding, will have one of its four
1.8 meter telescopes operational in Hawaii in early 2008. If the
planned, four telescope version of Pan-STARRS is completed by 2010, it
could help reach the goal by about 2040. Likewise the 8.4 meter
aperture Large Synoptic Survey Telescope (LSST) that is under
development with funding from NSF, DOE and other partners, could help
reach the goal by about 2034 if it began operation in 2014. If we
assume that both the Pan-STARRS four telescope system and the LSST
operate in their planned shared modes, which includes many observations
unrelated to PHAs, then the goal could be reached by about 2026. The
PHA discovery rate could be increased beyond the results shown in the
NASA response to the 2005 Act if the observing time and sequences of
Pan-STARRS and LSST were optimized for PHA observations.
In terms of actual discoveries of new PHAs, there has been little
success beyond the survey programs supported by NASA. However, the
international community, including many sophisticated amateur
astronomers, is very active in providing the follow-up observations
necessary to secure an object's orbit once it has been found. The
NEODyS program in Pisa, Italy works closely with, but independent of,
the NEO Program Office at JPL to compute impact probabilities for
predicted Earth close approaches for at least 100 years into the
future. It is also encouraging to note the activities of a NEO Action
Team within the UN Committee on the Peaceful Uses of Outer Space
(COPUOS) includes an effort to encourage more international efforts on
the NEO issues.
The importance of Radar Observations: There are only two planetary
radars in existence (and no alternatives) that can routinely observe
close Earth approaching asteroids, and both of them are critically
important for investigating the nature of these objects and for rapidly
refining their trajectories. The 70-meter Goldstone antenna in
California's Mojave desert is fully steerable, can track an asteroid
and can cover large regions of sky while the larger 305-meter Arecibo
antenna in Puerto Rico has twice the range but only observes within a
40-degree zone centered on the overhead position (20 degrees on either
side of zenith). The capabilities of these two telescope complement one
another and often a significantly better and longer set of observations
can be achieved using both radars on a close approaching target
asteroid.
Most positional data for PHA orbit determination and trajectory
predictions are based upon optical, plane-of-sky observations. Because
the radars provide line-of-sight velocity and range information
accurate to about the one mm/s and 10 meter levels, these data when
used in conjunction with the optical data provide a secure orbit and
trajectory far more rapidly than if only optical data are available.
With only a limited amount of optical data to work with, the orbit of a
newly discovered PHA is often not accurate enough to immediately rule
out a future Earth impact. However, with radar data in hand, the orbit
of a newly discovered PHA can be quickly and more precisely determined,
its motion accurately projected far into the future and future impact
possibilities can usually be quickly ruled out. Likewise, in the rare
situation when an object is actually on an Earth threatening
trajectory, radar observations will be critical in quickly identifying
this case.
Unfortunately the Arecibo radar program is not funded by the NSF
beyond FY 2007 and the planetary science community is in danger of
losing one of its instrumental crown jewels. As a measure of this radar
facility's importance, note that 65 percent of all radar experiments to
characterize near-Earth asteroids were performed at Arecibo, 47 percent
of all binary near-Earth asteroids were discovered at Arecibo and 85
percent of the near-Earth asteroids with the critical astrometric radar
data for orbit improvement have data from Arecibo. All of this was
accomplished with only five percent of this instrument's time. The
superior sensitivity of the giant Arecibo radar can determine the
sizes, shapes, rotation characteristics, surface characteristics and
binary nature for many PHAs. All of these physical characteristics are
important criteria to understand before a deflection mission is
considered. Radar observations are responsible for the best physical
characterization of any PHA as large as a kilometer (i.e., the binary
asteroid 1999 KW4). Radar observations reduce a PHA's orbit
uncertainties quickly and dramatically so that future impact
possibilities can be quickly knocked down thus reducing the odds that
we will need to invest in a spacecraft investigation to characterize
the PHA's nature in preparation for a precautionary deflection mission.
Thus the relatively modest costs of maintaining the Arecibo radar in a
robust state could prevent the future need for 100's of millions of
dollars per case for spacecraft reconnaissance of an object to
determine whether or not it is an actual threat.
What Should be Done in the Event of an identified NEO Threat? A number
of existing technologies can deflect an Earth threatening asteroid--if
there is time. The primary goal of the PHA survey programs is to
discover them early and provide the necessary time. An asteroid that is
predicted to hit Earth might require a change in its velocity of only
three millimeters per second if this impulse were applied twenty years
in advance of the impact. The key to a successful deflection is having
sufficient time to carry it out, whether it is the slow, gentle drag of
a gravity tractor or a more impulsive shove from an impacting
spacecraft or explosive device. In either case, a verification process
would be required to ensure the deflection maneuver was successful and
to ensure the object's subsequent motion would not put it on yet
another Earth impacting trajectory. While suitable deflection
technologies exist, none of them can be effective if we are taken by
surprise. It is the aggressive survey efforts and robust planetary
radars that must ensure that the vast majority of potentially hazardous
objects are discovered and tracked well in advance of any Earth
threatening encounters. The first three steps in any asteroid
mitigation process are: Find them early, find them early, and find them
early!
Biography for Donald K. Yeomans
At the Jet Propulsion Laboratory in Pasadena California, Donald K.
Yeomans is a Senior Research Scientist, supervisor of the Solar System
Dynamics Group, and manager of NASA's Near-Earth Object Program Office.
His group is responsible for providing position predictions for the
solar system's planets, natural satellites, comets and asteroids. For
the comets and asteroids that can approach the Earth, his group
monitors their motions and provides predictions and impact
probabilities for future Earth encounters.
Dr. Yeomans was the Radio Science team chief for NASA's Near-Earth
Asteroid Rendezvous (NEAR) mission. He is currently the NASA Project
Scientist for the Joint Japanese and U.S. mission to land upon, and
return a sample from, a near-Earth asteroid (Hayabusa) and he was a
scientific investigator on NASA's Deep Impact mission that successfully
impacted comet Tempel 1 in July 2005. He provided the accurate
predictions that led to the recovery of comet Halley at Palomar
Observatory on October 16, 1982 and allowed the discovery of 164 BC
Babylonian observations of comet Halley on clay tablets in the British
Museum.
He is a graduate of Middlebury College in Vermont and received his
doctorate degree in astronomy from the University of Maryland in 1970.
He has written numerous technical papers and four books on comets and
asteroids. He has been awarded 15 significant achievement awards by
NASA including an Exceptional Service Medal and a Space Act Award. To
honor his work in planetary science, asteroid 2956 was renamed 2956
YEOMANS.
Chairman Udall. Thank you, Dr. Yeomans. You all heard the
bells ringing. One vote has been called on the Floor of the
House, so we are going to continue the hearing. Congressman
Lampson will come back and relieve me, so we can make the best
use of your time and the Committee's time.
So, thank you, Dr. Yeomans. We will move to Dr. Campbell.
Looking forward to your testimony, sir.
STATEMENT OF DR. DONALD B. CAMPBELL, PROFESSOR OF ASTRONOMY,
CORNELL UNIVERSITY; FORMER DIRECTOR, ARECIBO OBSERVATORY
Dr. Campbell. Mr. Chairman and Members of the Committee,
thank you for this opportunity to address you on the role of
radar, and specifically, the radar system on the giant Arecibo
Telescope in Puerto Rico, in the tracking and characterization
of NEOs, and the current state of funding of this National
Science Foundation facility.
Dr. Yeomans has just described the importance of precision
radar measurements in predicting the future orbits of NEOs, and
determining which NEOs are really hazardous to Earth. For these
hazardous objects, additional precision radar measurements are
extremely important to assess the impact probability and the
need to take action to mitigate the threat.
Near-Earth asteroids form a very diverse population,
encompassing a large range of sizes, shapes, rotation states,
densities, internal structure, and binary nature. It is
important to understand the range of these characteristics in
order to design suitable mitigation strategies. While a very
small number of NEOs have been visited by spacecraft, radar
provides by far the best means to survey these characteristics
for a large number of objects. For an object that we know poses
a direct threat to Earth, radar can provide vital input to
mitigation planning.
As you have heard, there are only two very high powered
radars in the world capable of studying solar system bodies
including NEOs. One is on the NSF's Arecibo Telescope, and the
other is on NASA's Deep Space Network 70 meter antenna in
California. The Arecibo radar is over 20 times more sensitive
than the one on the Goldstone antenna, and has been the
dominant contributor to near-Earth asteroid characterization
and orbit prediction. However, the Goldstone antenna can look
at more of the sky than Arecibo, making the two systems very
complementary. They should both be preserved.
In 2005 and 2006, the NSF Division of Astronomical Sciences
undertook a Senior Review to examine the balance of its
investments in various astronomical facilities the Division
supports, including the Cornell University-based National
Astronomy and Ionosphere Center, which operates the Arecibo
Observatory for the NSF. The report was submitted to the NSF in
November 2006. Despite considerable input to the Committee from
both the National Astronomy and Ionosphere Center and the
planetary community, the Arecibo Planetary NEO Radar Program is
essentially ignored in the Committee's report.
The report recommended that NAIC's operating funds provided
by the NSF's Division of Astronomical Sciences be reduced over
the following three years from approximately $10.5 million to
$8 million, and then in Financial Year 2011, be halved again to
$4 million. At the $8 million level, budgetary pressures are
likely to make the termination of the radar and NEO program
unavoidable, unless additional funding is found. In the
slightly longer-term, if Cornell cannot find the additional
funding needed to keep the Observatory open, then, in the
report's words, ``The Senior Review recommends closure after
2011 if the necessary support is not forthcoming.''
If the Arecibo radar system is decommissioned, it would
leave the lower sensitivity NASA Goldstone system as the only
radar in the world capable of precise orbit determination for
NEOs and measurements characterizing their physical properties.
It will probably be unable to fill the void, especially with
the large number of NEOs likely to be detected over the next
decade or more.
Replacing the Arecibo Telescope and radar system with a
mission-specific facility of equal sensitivity would cost
several hundred million dollars. Given its contributions to the
NEO program and other research areas, and the relatively small
budget needed to keep it operating, closing Arecibo does not
make sense.
In answer to the question as to how much it would cost to
support Arecibo for NEO activities, independent of any other
use of the telescope, the budget would probably need to be very
roughly the same as the Observatory's current budget, about $10
million per year. Most of the operating costs of large
telescopes are fixed costs, relating to such things as
maintenance, independent of the science mission.
In summary, Earth-based radar provides critical information
related to NEO orbit prediction and characterization. Arecibo
is the primary radar involved in this activity, and will remain
so for at least the next 10 years provided that both the
Observatory and its radar system are adequately funded.
If the Arecibo Observatory is closed, a unique research
capability will be lost that makes valuable contributions not
only to the study of Near-Earth Objects, but in other areas of
astronomy and atmospheric science. One of Puerto Rico's main
research facilities, and a spectacular structure as you saw
earlier, the Arecibo Telescope is important to local education
and tourism. Its closing would be a major loss to both science
and the island.
Thank you for your attention.
[The prepared statement of Dr. Campbell follows:]
Prepared Statement of Donald B. Campbell
Mr Chairman and Members of the Committee, thank you for this
opportunity to address you on the important issue of near-Earth objects
and their potential threat to Earth.
I have been asked to address issues related to the use of radar
systems to track and characterize near-Earth objects (NEOs) and,
specifically, to address the role of the radar system on the giant
Arecibo telescope in Puerto Rico in this activity and the current state
of funding for this National Science Foundation facility. I will
address these questions in turn.
What role do Earth based radars play in the tracking and
characterization of Near Earth Objects (NEOs)? What role, if any, do
they play in providing information about specific hazardous objects?
Radar plays an important role in predicting the future orbits of
NEOs and measuring many of their physical characteristics such as size,
shape, rotation state and, in the case of binary objects, their mass
and density. Radar can measure distances to NEOs to an accuracy of
about 10m (30 ft) and their line-of-sight velocity to an accuracy of
about one mm per second (12 ft per hour), orders of magnitude better
than the equivalent optical measurements. For potentially hazardous
objects (PHOs), optical observations based on measuring their changing
position on the sky over days or weeks in many instances cannot rule
out a possible future impact with the Earth. To do so can require
optical positional measurements spanning years or decades. For future
searches, radar astrometry, the measurement of distance and line-of-
sight velocity, can be used to help cull the number of PHOs--not all
the newly detected NEOs will be observable with radar--so that we can
concentrate on the few that really are potentially hazardous. For these
objects, additional precision radar measurements are extremely
important to assess the impact probability and the need to take action
to mitigate the threat.
The more we know about NEOs in general and about specific ones that
pose a threat to Earth, the easier it will be to design effective
mitigation strategies. ``Know your enemy'' would seem to be good advice
in this instance. NEOs form a very diverse population encompassing a
large range of sizes, shapes, rotation states, densities, internal
structure and binary nature. While a very small number of NEOs have
been visited by spacecraft, radar provides by far the best means to
survey these characteristics for a large number of objects. Knowing the
range of characteristics facilitates the design of effective mitigation
techniques that can be applied to an object with any of these
characteristics. For an object that we know poses a direct threat to
Earth, radar can provide vital input to mitigation planning including
planning for any precursor space mission.
Over the past few years, the accuracy of the Earth impact
prediction based on precision radar astrometry for a few PHOs has been
limited not by the accuracy of the radar measurements but by the
inability to accurately model all of the very small forces on these
objects in addition to that due to the Sun's gravity. One of these
forces, the Yarkovsky effect, is related to sunlight absorbed by the
body and its re-emission as heat. Precision radar astrometry over
several years of a small asteroid, Golevka, demonstrated in 2003 that
this effect can modify the orbits of small asteroids over very long
periods of time. This has revolutionized our understanding of how small
asteroids in the main asteroid belt between Mars and Jupiter are
transported into the inner solar system to become NEOs and, some, PHOs.
This new understanding resulting from a basic science driven project
will also help in refining PHO Earth impact probabilities for the few
objects that may be of real concern.
What role has the Arecibo Observatory played in surveying
NEOs and what are the impacts to the NEO program should Arecibo be
decommissioned?
The radar system on the NSF's Arecibo Telescope in Puerto Rico is
one of only two very high powered radars in the world that are used for
studying solar system bodies including NEOs. The other one is on NASA's
Deep Space Network 70m antenna at Goldstone in California's Mojave
desert. With its 300m (1,000 ft) diameter telescope and radiated power
of one megawatt, the Arecibo radar is over 20 times more sensitive than
the one on the Goldstone antenna. However, because of its limited
steerability, Arecibo can only observe about half the sky observable
with the Goldstone antenna making the two systems very complementary.
Because of its greater sensitivity and availability, the Arecibo
radar system has carried out 65 percent of all radar observations
characterizing NEOs, 47 percent of the known binary NEOs were
discovered with Arecibo (most of the rest were discovered with optical
telescopes), and data from Arecibo was used for 85 percent of the NEOs
for which precision radar distance and velocity astrometric
measurements have been made for orbit determination.
If the Arecibo radar system is decommissioned it would leave the
lower sensitivity radar system on the NASA 70m Goldstone antenna as the
only radar system in the world capable of precise astrometry of NEOs
and measurements characterizing their physical properties. A tremendous
amount of basic science related to NEOs and other solar system bodies
would be lost and the highest sensitivity radar would no longer be
available to provide precision astrometry and characterization data
just as the NEO search programs are ramping to a new level. Given the
pressures on the 70m Goldstone antenna in carrying out its prime
mission, its lower sensitivity and the large number of NEOs likely to
be detected over the next decade or more, it seems unlikely that this
system could come close to filling the void. Replacing the Arecibo
telescope and radar system with a mission specific facility of equal
sensitivity would cost several hundred million dollars. Given its
contributions to the NEO program and other research areas in radio
astronomy and ionospheric physics and the relatively small budget
needed to keep it operating, closing Arecibo does not make sense. In
the words of Bill H.R. 3737, recently submitted by Congressman Fortuno
on behalf of himself, Congressman Rohrabacher and other Members of the
House of Representatives, ``The Arecibo Observatory is an invaluable
and unique asset in warning and mitigating potential hazards posed by
near-Earth objects.''
Did the recent National Science Foundation (NSF) Senior
Review of Arecibo evaluate the facility's role in surveying NEOs and
the impact of Arecibo's potential decommissioning on the NEO survey
program? If not, why not?
The National Astronomy and Ionosphere Center (NAIC), the formal
name for the Arecibo Observatory located in Puerto Rico, is one of the
four National Astronomy Centers plus the U.S. component of the
international Gemini observatory, funded through the Division of
Astronomical Sciences at the NSF and is operated by Cornell University
under a Cooperative Agreement with the NSF. NAIC is unique among the
Centers in that it supports research in three diverse areas, radio
astronomy, planetary radar astronomy including the study of NEOs, and
ionospheric physics. The first two are supported through funding from
the Division of Astronomical Sciences at the NSF while the ionospheric
program, about 15 percent of the budget, is funded through the Division
of Atmospheric Sciences at the NSF. NAIC has about 120 people working
at the Arecibo Observatory in Puerto Rico. In addition to providing
research facilities for its scientific user community, it operates a
visitor center that attracts about 120,000 visitors a year most from
Puerto Rico including about 25,000 school children.
In 2005-2006 the Division of Astronomical Sciences of the National
Science Foundation (NSF) undertook a ``Senior Review'' to examine the
balance of its investments in the various astronomical facilities that
the Division supports. The review was motivated by a combination of the
budget outlook at that time for the Foundation and the ambitions of the
astronomical community to invest in new facilities to address
fundamental questions as recommended in the previous Astronomy Decadal
Survey and other reports such as ``Connecting Quarks with the Cosmos.''
The Senior Review committee submitted its report to the NSF in
November, 2006.
The aims of the Senior Review were widely supported by the
astronomical community and it is not my intention to criticize its
major findings. However, its charge was to look at the ``big picture''
and in such a process small, high quality programs that are not central
to the priorities of the committee or the NSF can end up becoming a
casualty on the way to the main goal. Such seems to be the case for the
planetary/NEO radar program at the Arecibo Observatory. During the
review process, Cornell University and NAIC provided considerable input
to the committee about the Observatory's research programs including
the planetary/NEO radar program. Many planetary astronomers, especially
those interested in NEOs, wrote to the Committee strongly supporting
the Arecibo radar program. However, the Arecibo planetary/NEO radar
program was essentially ignored in the committee's report with the only
explanation I have heard being that the program was too small in
funding terms to be individually considered. There were no planetary
astronomers on the committee.
I should emphasize that the Senior Review report did not recommend
that the Arecibo planetary/NEO radar program be canceled but that is
likely to be the outcome of its budgetary recommendations vis-a-vis
NAIC. It recommended that NAIC's operating funds provided by the NSF
Division of Astronomical Sciences, about 85 percent of its yearly
budget with the rest coming from the NSF Division of Atmospheric
Sciences, be reduced over the following three years from approximately
$10.5M to $8M and then, in FY 2011, be halved again to $4M. By early
2009 Cornell is required to have definite commitments from other
entities for the additional operating funds needed to keep the
observatory open. If it cannot get these commitments then, in the
Senior Review report's words ``The Senior Review recommends closure
after 2011 if the necessary support is not forthcoming.''
The planetary/NEO radar program is scheduled to continue in
operation at a reduced level of activity through FY 2008 compared with
its normal use of about 400 hours of telescope time per year. If the
NSF implements the Senior Review's recommendations to reduce NAIC's
budget for astronomical research to the $8M level, budgetary pressures
and deferred maintenance are then likely to make termination of the
radar/NEO program unavoidable unless additional funding is found. Since
the planetary/NEO radar system has significant operational and
maintenance costs associated with the transmitting system, terminating
it is the only identifiable way to save about $1M in operating costs
short of canceling the observatory's entire radio astronomy program.
The NSF has said that they will not augment NAIC's budget to provide
support for the planetary radar/NEO program and has indicated that this
area of research should be supported by NASA. Until a few years ago,
NASA did provide partial support for the Arecibo radar program. In the
slightly longer-term, if additional operating funds are not found well
before the projected FY 2011 NSF/AST reduction to $4M then the Arecibo
Observatory will possibly be closed definitely terminating its
contributions to the tracking and characterization of NEOs.
What level of funding and technical support would be required
to carry out the NEO-related activities of Arecibo, independent of any
other astronomy-related activities? Will any upgrades to the facility
or its instruments be required?
The current yearly cost for operating Arecibo's planetary radar
system for about 400 hours a year is close to $1M. About 60 percent of
this time is devoted to NEO research. This covers the cost of the
operation and maintenance of the high powered transmitting capability
plus several engineers and a small scientific staff. It does not cover
major maintenance items for the transmitting system. It also does not
cover the cost for the operation and maintenance of the telescope and
the general support for grounds, buildings, etc., needed to keep the
observatory operating as a facility. Prorating these costs based on the
observing hours used would raise the current costs of the planetary
radar program to close to $2M/yr.
No study has yet been done of the precise role of the Arecibo radar
and how many hours of NEO observations will be needed when the new,
high sensitivity searches commence starting with Pan-STARRS. This needs
to be done. The demand for the use of the Arecibo radar will
undoubtedly increase significantly but whether by a factor of two or
five is uncertain. While maintaining the observatory's multi-
disciplinary program, some increase in the use of the radar system for
NEO observations can certainly be accommodated. A program using about
500 hours a year for NEO observations and, perhaps, 100 hours for radar
studies of other solar system bodies would cost $2M to $3M including
its share of general observatory support costs. The costs would prorate
roughly with observing time.
In answer to the question as to how much it would cost to support
Arecibo for NEO activities independent of any other use of the
telescope, the budget would need to be very roughly the same as the
observatory's current budget, about $10M per year. Most of the
operating costs of large telescopes are fixed costs related to
maintenance, etc., independent of the science mission. However, I want
to emphasize that any NEO radar program is unlikely to utilize all, or
even a majority, of the observing time available on the telescope.
The Arecibo telescope and radar system underwent a major NSF and
NASA funded upgrading about ten years ago. At this time some major
components of the transmitting system need refurbishment or replacement
and some of the data handling equipment used for the NEO program needs
updating. Total costs of this are estimated to be about $2M.
What are your perspectives on NASA's Near-Earth Object Survey
and Deflection Analysis of Alternatives Report to Congress?
NASA's report was a comprehensive discussion of the issues related
to the detection of 90 percent of all NEOs larger than 140m by 2020,
the requirement to determine their orbits, understand the broad
characteristics of different classes of asteroids in order to be able
to design mitigation strategies, and, of course, the range of possible
mitigation strategies. Staying within my area of expertise, the
report's discussion on the usefulness of determining orbits with radar
versus with optical means and the best means to characterize these
objects to, in the report's words, ``inform mitigation'' should be
revisited. For orbit determination the issue is whether a relatively
quick refinement of at least some percentage of the orbits of newly
discovered PHOs is preferable to waiting the 10 to 20 years that
optical means require for orbit determinations that will as stated in
the report ``nearly match the accuracy of radar-improved orbits.''
The role of the radar systems in surveying the broad range of NEO
types could also have been given more emphasis in the report. Radar is
currently the only Earth or Earth-orbit based technique that has the
resolution needed to provide information about a wide range of physical
properties important to mitigation planning. The images below show the
detailed shape model of the main component of the binary NEO 1999 KW4
and a simulation of the binary system, results obtained by Steven Ostro
of JPL and colleagues from observations using the Arecibo and Goldstone
radars. The work was described in the cover article of Science magazine
last November. We now know KW4's size, about 1.5 km (one mile) for the
main body, shape, rotation rate, mass, density and that it is a binary
object. The low density of the main body, about twice that of water,
tells us that it is rubble pile rather than a single large ``rock.''
This is all information that is critical to ``informing mitigation.''
Chairman Udall. Thank you, Dr. Campbell.
Next on the panel is Dr. Tyson, and I would, as a preface
to his remarks, mention that as a Member of the Armed Services
Committee, I am used to many, many acronyms, and I used one
earlier in my comments to begin the hearing, about the LSST,
which is the Large Synoptic Survey Telescope Project, and Dr.
Tyson is a key part of that effort.
So, Dr. Tyson, welcome, and the floor is yours.
STATEMENT OF DR. J. ANTHONY TYSON, PROFESSOR OF PHYSICS,
UNIVERSITY OF CALIFORNIA, DAVIS; DIRECTOR, LARGE SYNOPTIC
SURVEY TELESCOPE PROJECT
Dr. Tyson. Thank you, Mr. Chairman and Members of the
Committee. It is an honor to be asked to testify before you
today on this important subject.
The House Committee on Science has been a leader, on a
bipartisan basis, over two decades, in focusing attention on
the need to detect, characterize, and catalog near-Earth
asteroids. The passage of the George E. Brown Near-Earth Object
Survey Act was a landmark piece of legislation that sets a goal
of cataloging 90 percent of NEOs of 140 meters in diameter and
larger within 15 years.
The Committee is properly looking at the existing and
future capabilities of carrying out this goal and expanding the
existing Spaceguard program. LSST adopted the goal of surveying
NEOs at the outset as one of its major science capabilities. I
have attached to the statement a nine page summary of the
capabilities of LSST for detecting NEOs and obtaining their
orbits.
Until recently, the discussion of risk associated with an
impact of NEOs has been statistical. In other words, what is
the probability? This is similar to considerations of risk in
many other areas, such as weather and traffic accidents. What
if it were feasible to deploy a system that would alert me of
an impending traffic accident well in advance? That would
change the very nature of that risk from a probabilistic worry
to a deterministic, actionable situation. The ability to detect
virtually every potentially hazardous near-Earth object and
determine its orbit with precision transforms that statistical
threat into a deterministic prediction. We face many threats,
and virtually all of them are either so complex or
unpredictable that they are treated probabilistically, even
though the social and financial consequences are legion. With a
comparatively small investment, the NEO risk can be transformed
from a probabilistic one to a deterministic one, enabling
mitigation.
Ground-based optical surveys are the most cost-effective
tool for comprehensive NEO detection, determination of their
orbits, and subsequent tracking. Radar, as we have heard, also
plays an important role once the threatening NEO has been
found, in refining its orbit when the NEO is near. The first
job is to find the NEOs which are potentially hazardous, so-
called potentially hazardous objects, or potentially hazardous
asteroids, actually, from among the swarm of 10 million other
asteroids.
A survey capable of extending these tasks to NEOs with
diameters as small as 140 meters, as mandated by Congress,
requires a large telescope, a large camera, and a sophisticated
data acquisition, processing, and dissemination system. This
Congressional mandate drives the requirement for an eight meter
class telescope with a 3,000 megapixel camera and a
sophisticated and robust data processing system. These
requirements are met by the LSST.
The LSST is currently, by far, the most ambitious proposed
survey of the sky. With initial funding from the National
Science Foundation, Department of Energy laboratories, and
private sponsors, the design and development efforts are well
underway at many institutions.
Fortunately, the same hardware and software requirements
are driven by science unrelated to NEOs. LSST reaches the
threshold where different science drivers, and therefore,
different agencies, NSF, DOE, and NASA, can work together to
efficiently achieve seemingly disjoint but deeply connected
goals. This broad range of science has earned LSST the
endorsement of a number of committees commissioned by the
National Academy of Sciences. Because of this synergy, the
Congressional mandate can be reached at only a fraction of the
cost of a mission dedicated exclusively to NEO search.
We have carried out over 100 computer simulations of the
LSST operations for a variety of NEO optimized scenarios. The
planned LSST baseline survey cadence on the sky, that is to
say, the way you tile the sky with time, during the night, is
capable of providing orbits for 82 percent of potentially
hazardous asteroids larger than 140 meters after 10 years of
operation, and is 90 percent complete for objects larger than
230 meters. This baseline cadence assumes that five percent of
the total observing time is spent on NEO specialized observing.
This is what is currently planned.
By increasing this fraction of NEO specialized surveying to
15 percent, that is to say, from five to 15 percent, and by
running the survey longer, the Congressional mandate of 90
percent completeness for potentially hazardous asteroids of 140
meters and greater size, can be fulfilled after 12 years of
operation, with 60 percent completeness level reached after
only three years. These specialized observations would be of
limited use to other science programs, and they require 15
percent of the observing time.
The current cost estimate for LSST in 2006 dollars is $389
million for construction, and $37 million per year for
operations. For a 12-year long survey, 15 percent of this total
cost is $125 million. Thus, we could deliver the performance of
a full NEO dedicated LSST to NASA and to the world at a small
fraction of the total cost to build and operate such a system.
This cost is equivalent to 30 percent of operations, which
would commence in 2014.
Note that by operating LSST in this special NEO optimized
mode, we would have the performance equivalent of an LSST fully
dedicated to NEO serving. By supporting only 15 percent of the
total cost, NASA would be essentially getting an NEO dedicated
LSST. This is a key new insight, relative to the costing model
in the 2007 NASA NEO report to Congress.
Thank you.
[The prepared statement of Dr. Tyson follows:]
Prepared Statement of J. Anthony Tyson
Mr. Chairman and Members of the Committee. It is an honor to be
asked to testify before you today on this important subject. By way of
identification, I am an astrophysicist and Professor of Physics at the
University of California, Davis, and Director of the Large Synoptic
Survey Telescope (LSST) project; before coming to UC-Davis four years
ago I did research and development at Bell Labs for 34 years.
The House Committee on Science has been a leader on a bipartisan
basis for over two decades in focusing attention on the need to detect,
characterize, and catalog near-Earth asteroids. The passage of the
``George E. Brown Jr. Near-Earth Object Survey Act'' was a landmark
piece of legislation that sets a goal of cataloging 90 percent of NEOs
of 140 meters in diameter and larger within 15 years. The Committee is
properly looking at the existing and future capabilities for carrying
out this goal and expanding the existing Spaceguard program. LSST
adopted the goal of surveying NEOs at the outset as one of its major
science capabilities.
Until recently, the discussion of risk associated with an impact of
a NEO has been statistical; what is the probability? This is similar to
considerations of risk in many other areas such as weather and traffic
accidents. What if it were feasible to deploy a system that would alert
me of an impending traffic accident well in advance? That would change
the very nature of that risk from a probabilistic worry to a
deterministic actionable situation. The ability to detect virtually
every potentially hazardous Near-Earth object and determine its orbit
with precision transforms that statistical threat into a deterministic
prediction. We face many threats, and virtually all of them are either
so complex or unpredictable that they are treated probabilistically
even though the social and financial consequences are legion. With a
comparatively small investment the NEO risk can be transformed from a
probabilistic one to a deterministic one, enabling mitigation.
The First Job: Finding the NEOs
Ground-based optical surveys are the most efficient tool for
comprehensive NEO detection, determination of their orbits and
subsequent tracking. (Radar also plays an important role once a
threatening NEO has been found, in refining its orbit when the NEO is
near.) The first job is to find the NEOs which are potentially
hazardous (so-called Potentially Hazardous Asteroids) from among the
swarm of ten million other asteroids. A survey capable of extending
these tasks to NEOs with diameters as small as 140m, as mandated by
Congress, requires a large telescope, a large camera, and a
sophisticated data acquisition, processing and dissemination system.
The Congressional mandate drives the requirement for an eight-meter
class telescope with a 3000 Megapixel camera and a sophisticated and
robust data processing system. These requirements are met by the LSST.
Why is a large telescope required? A typical 140-meter NEO appears
very faint (visual magnitude of 25). Multiple NEO detections in a
single night are required to estimate its motion, so that its future or
past detections can be linked together. This linkage has to be done
exceedingly robustly because the near-Earth objects will be outnumbered
nearly a thousand to one by main-belt asteroids (between Mars and
Jupiter) which present no threat to Earth. By reliably linking
detections on multiple nights, the NEO's orbit can be reconstructed and
used to compute its impact probability with Earth. Despite their name,
NEOs are typically found far from Earth. In principle, very faint
objects can be detected using long exposures, but for objects moving as
fast as typical NEOs, the so-called trailing losses limit the exposure
time to about 30 seconds. In order to detect 140-meter NEOs in 30
seconds, an eight-meter class telescope is required.
Why is a large camera required? The need for a very large field of
view comes from the requirement that the whole observable sky should be
observed at least every four to five nights. For comparison, we need a
field of view thousands of times larger than the Hubble Space
Telescope's Advanced Camera for Surveys. With its 10 square degree
field of view, LSST will be able to reach the mandated high NEO
completeness.
Finding Near-Earth Objects with Ground-based Surveys
Ground-based optical surveys are a very cost effective tool for
comprehensive NEO detection, determination of orbits, and subsequent
tracking. A survey capable of extending these tasks to NEOs with
diameters as small as 140m, as mandated by Congress, drives the
requirement for a large telescope, a large camera, and a sophisticated
data acquisition, processing and dissemination system.
To find a significant fraction of the faint NEOs one must
essentially make a movie of the deep sky. Each faint asteroid must be
captured in many separate exposures in order for computers to
distinguish it from the numerous other asteroids and then piece
together its orbit. A large area of the sky (ideally all the sky
visible from some location on Earth, at least 20,000 square degrees)
must be surveyed rapidly and deeply in order to survey a large volume
for these faint asteroids. The ability of a telescope and camera to
take rapid deep repeated images of the entire sky is proportional its
``throughput.'' Throughput (sometimes called etendue) is simply the
product of the telescope light collection area (units: square meters)
times the camera field of view in a single snapshot (units: square
degrees). Thus throughput of a survey facility is measured in units of
square meters square degrees. The throughput of LSST is 320 square
meters square degrees. High throughput is a necessary condition for
such a facility to carry out its mission, but not a sufficient
condition: one must also arrange to have high observing efficiency
(access to the sky) and highly efficient optics and imaging detectors
in the camera, as well as superb image quality.
For an efficient NEO survey, the whole observable sky should be
observed at least every four to five nights, with multiple observations
per night. In order to do so with exposure time of about 30 seconds per
observation, a 10 square degree large field of view is required. Such a
large field of view, with pixel size sufficiently small to fully sample
the image at a good observing site, implies a multi-billion pixel
camera. Indeed, at the time of its completion, the 3.2 billion pixel
LSST camera will be the largest astronomical camera in the world.
With a 3.2 billion pixel camera obtaining images every 15 seconds
(individual 30 second exposures are split into two 15 second exposures
for technical reasons), the data rate will be about 20 thousand
gigabytes per night. Not only is this a huge data rate, but the data
have to be processed and disseminated in real time, and with exquisite
accuracy. It is estimated that the LSST data system will incorporate
several million lines of state-of-the-art custom computer code.
State of the LSST project
The Large Synoptic Survey Telescope (LSST) is currently by far the
most ambitious proposed survey of the sky. With initial funding from
the U.S. National Science Foundation (NSF), Department of Energy (DOE)
laboratories and private sponsors, the design and development efforts
are well underway at many institutions, including top universities and
leading national laboratories. The main science themes that drive the
LSST system design are Dark Energy and Dark Matter, the Solar System
Inventory, Transient Optical Sky and the Milky Way Mapping. It is this
diverse array of science goals that has generated the widespread
excitement of scientists ranging from high-energy physicists to
astronomers and planetary scientists, and earned LSST the endorsement
of a number of committees commissioned by the National Academy of
Sciences.
Fortunately, the same hardware and software requirements are driven
by science unrelated to NEOs: LSST reaches the threshold where
different science drivers and different agencies (NSF, DOE and NASA)
can work together to efficiently achieve seemingly disjoint, but deeply
connected, goals. Because of this synergy the Congressional mandate can
be reached at only a fraction of the cost of a mission dedicated
exclusively to NEO search.
The scientific priority for constructing a large aperture ground
based survey telescope was recommended in the astronomy and
astrophysics Decadal Survey 2000 report entitled Astronomy and
Astrophysics in the New Millennium. Since then, LSST has reached a high
state of design maturity. LSST has recently passed the NSF Conceptual
Design Review for construction, which puts it on track for transition
to Readiness in spring 2008. LSST is a public-private project. To date
$44M in private funding has been raised. Twenty two institutions have
joined the effort and have contributed significant in-kind technical
labor. LSST R&D continues for another three years under NSF support
along with in-kind contributions. The project is on track for first
light in 2014. It is proposed that the DOE (because of the importance
of LSST for addressing the mystery of dark energy) support the $80M
cost of constructing the camera. Foreign support now appears likely,
and this in-kind would offset the camera cost.
Method of Study: the LSST Operations Simulator
The LSST Operations Simulator was developed to be able to do just
the sort of assessment described in this document. It contains detailed
models of site conditions, hardware and software performance, and an
algorithm for scheduling observations which will, eventually, drive the
robotic LSST observatory. The resulting sky coverage for the LSST
baseline cadence is shown in Figure 1.
For the currently planned LSST baseline cadence, objects counted as
cataloged are observed on 20 different nights on average. A more
stringent requirement could decrease the completeness by up to three
percent. The completeness is also a function of the assumed size
distribution: the flatter the distribution, the higher the
completeness. If the latest results for the NEO size distribution by A.
Harris are taken into account, the completeness increases by one to two
percent. Due to these issues, the completeness estimates have a
systematic uncertainty of two percent. Our analysis assumes that no
NEOs are known prior to LSST. Current surveys make a negligible
contribution to the 90 percent completeness for NEOs of 140m and up.
The NEO survey completeness achievable with LSST
The LSST system is the only proposed astronomical facility that can
detect 140-meter objects in the main asteroid belt in less than a
minute. The LSST system will be sited at Cerro Pachon in northern
Chile, with first light scheduled for 2014. In a continuous observing
campaign, LSST will cover the entire available sky every four nights,
with at least two observations of an NEO per night. Over the baseline
survey lifetime of 10 years, each sky location would be observed over
800 times. Two NEO detections in a single night are required to
estimate its motion, so that its future or past detections can be
linked together. This linkage has to be done exceedingly robustly
because the near-Earth objects will be outnumbered a hundred to one by
main-belt asteroids which present no threat to Earth. By reliably
linking detections on multiple nights, the NEO's orbit can be
reconstructed and used to compute its impact probability with Earth.
The currently planned LSST baseline observing cadence on the sky,
described in the Major Research Equipment and Facilities Construction
proposal submitted to NSF, is simultaneously optimized for all four
main science drivers: Characterizing Dark Energy and Dark Matter, the
Solar System Inventory, Transient Optical Sky, and the Milky Way
Mapping (see Figure 1). Computer simulations of LSST observing show
that the data stream resulting from this baseline cadence on the sky is
capable of providing orbits for 82 percent of Potentially Hazardous
Asteroids (PHA) larger than 140 meters after 10 years of operations.
The completeness curve as a function of time since the start of the
survey is shown in Figure 2 (second curve from top). This baseline
cadence spends five percent of the total observing time on NEO-
optimized observations in the north region of the ecliptic (plane of
the solar system).
Various adjustments to this baseline cadence can boost the
completeness for 140m and larger PHAs to 90 percent. Based on about 100
different simulations, we find that such adjustments to the baseline
cadence or filter choices can have unacceptably large impact on other
science programs, if the 90 percent completeness is to be reached
within 10 years from the beginning of the survey. However, with a minor
adjustment of the baseline cadence and additional specialized observing
for NEOs, this completeness level can be reached with a 12-year long
survey, and with a negligible effect on the rest of science goals.
These specialized observations would be of limited use to other
science programs, and they require 15 percent of the observing time.
The dependence of completeness for 140m and larger objects on time is
shown in Figure 2. For LSST, Figure 2 shows the baseline survey and the
special NEO-optimized survey. In addition, we also show completeness
curves for the same observing cadence and under the same assumptions
regarding seeing and efficiency for smaller versions of LSST of less
throughput. The lowest curve (black line) in Figure 2 shows the
completeness for current NEO assets (ca. 2014-) for comparison.
Conclusions
The ability of LSST to reach the mandated 90 percent completeness
for 140m and larger PHAs in 10 years by the so-called ``dedicated''
option described in the 2007 NASA NEO report is supported by our
detailed and realistic simulations. An important additional insight
from these simulations is that we can deliver the performance of a
``dedicated'' system by spending 85 percent of the total observing time
on a general survey useful for all LSST science programs, and by
specializing only about 15 percent of the total observing time for NEO
surveying. If such an NEO-optimized program is executed for 12 years,
the 90 percent completeness for 140m and larger PHAs can be reached
without a significant negative impact on other science programs.
The current cost estimate for LSST in 2006 dollars is $389M for
construction and $37M per year for operations. For a 12-year long
survey, 15 percent of the total cost is $125M. Thus, we could deliver
the performance of a full NEO-dedicated LSST to NASA at a small
fraction of the total cost to build and operate such a system. This
cost is equivalent to 30 percent of operations, which would commence in
2014. To assure LSST keeps on schedule, about $5M should be spent on
optimized NEO orbit software pipeline development in the last phase of
R&D and the construction phase, 2009-2014.
Executive Summary
In December 2005 Congress directed NASA to implement a near-Earth
object (NEO) survey that would catalog 90 percent of NEOs larger than
140 meters in 15 years. In order to fulfill the Congressional mandate
using a ground-based facility, an eight-meter class telescope equipped
with a 3200 Megapixel camera, and a sophisticated and robust data
processing system are required. These criteria are met by the Large
Synoptic Survey Telescope (LSST). We have carried out over 100
simulations of the LSST operations for a variety of NEO-optimized
scenarios. The planned LSST baseline survey cadence on the sky,
simultaneously optimized for all main science drivers, is capable of
providing orbits for 82 percent of PHAs larger than 140 meters after 10
years of operation, and is 90 percent complete for objects larger than
230 meters. This baseline cadence assumes that five percent of the
total observing time is spent on NEO-specialized observing. This is
what is currently planned. By increasing this fraction to 15 percent
and by running the survey longer, the Congressional mandate of 90
percent completeness for NEOs of 140m and greater size can be fulfilled
after 12 years of operation, with 60 percent completeness level reached
after only three years.
Note that by operating LSST in this special NEO-enhanced mode we
would have the performance equivalent of an LSST fully dedicated to NEO
surveying. By supporting only 15 percent of the total cost, NASA would
be essentially getting a NEO-dedicated LSST. This is a key new insight
relative to the costing model in the 2007 NASA NEO report to Congress.
Biography for J. Anthony Tyson
J. Anthony ``Tony'' Tyson, distinguished Professor of Physics at
University of California, Davis, is an experimentalist interested in
gravitational physics. His current research is in cosmology: dark
matter distribution, gravitational lens effects, cosmic shear, and the
nature of dark energy. These investigations involve software for
pattern recognition, detection of transients in images, large database
handling and processing, and new instrumentation for optical astronomy.
He directs a national effort to build a new kind of telescope/camera
called the Large Synoptic Survey telescope (LSST). With its large
aperture and wide field of view, LSST promises to shed light on the
mysterious ``dark energy'' that is considered to be the most urgent
problem in the physics of our universe.
Tony Tyson received his B.S. in Physics from Stanford in l962 and a
Ph.D. from University of Wisconsin at Madison in 1967, and a
postdoctoral fellowship at the University of Chicago. He is a Fellow of
the American Physical Society and the American Academy of Arts and
Sciences, and a member of the National Academy of Sciences and the
American Philosophical Society.
Mr. Lampson. [Presiding] Thank you, Dr. Tyson. Mr.
Schweickart.
STATEMENT OF MR. RUSSELL ``RUSTY'' L. SCHWEICKART, CHAIRMAN AND
FOUNDER, B612 FOUNDATION
Mr. Schweickart. Mr. Chairman, Mr. Ranking Member Feeney,
and Members of the Committee, Mr. Lampson, I thank you for
giving me the opportunity here to testify on the Near-Earth
Object situation, on NASA's report to Congress on the matter,
and on where we need to go from here.
With very limited time, I will jump right into the four
questions I was asked to address, and our six specific
recommendations pertaining to it. We were asked first to
provide our perspectives on NASA's report to Congress, and
whether we agree or disagree with the report's findings and
recommendations.
The first two elements of the Congress' directive related
to analyzing ways of meeting the new goal, as we have heard,
and a specific directive to recommend a program and a budget to
support it. NASA completely ignored Congress' direction to
recommend a search program and supporting budget. I want to
emphasize here, picking up on Chairman Udall's earlier comment
that not only did the Congress direct NASA to make a
recommendation and a budget to support it, but the President
signed that into law, so it is in law by both the President and
the Congress.
So, our first recommendation is that Congress should again
direct NASA, in the clearest language possible, to comply with
the law, and recommend a search program and supporting budget.
With regard to Congress' directive, the third task of NASA,
that they analyze possible alternatives that could be employed
to divert an object on a likely collision course with Earth, we
highlight only two of the many technical flaws in NASA's report
to Congress. The first of those, NASA misinterpreted the
Congressional intent, and elected to consider forward
deflection, to look at what would be required, only a set of
very large, very improbable Near-Earth Objects, rather than the
far more frequent but still devastating impacts which we are
much more likely to encounter.
Assuming, therefore, this extraordinary demand, NASA
naturally came up with an extraordinary response, namely, the
use of nuclear explosives. In fact, 99 percent of the NEOs most
likely to trigger a call for deflection can be diverted by non-
nuclear kinetic impacts, that is, simply running into the Near-
Earth Object with a spacecraft, similar to what was done by
NASA on July 4, 2005, in the Deep Impact crash into Comet
Tempel 1.
In a letter clarifying the Congressional intent,
Congressman Dana Rohrabacher stated that: ``The first order of
business is to ensure that we have a clear understanding of
what the options are for the situations we are most likely to
encounter.'' When shown this letter, NASA's comment to us, in a
June 18, 2007 meeting was, to paraphrase it: ``If we had seen
this letter at the time we began the study, we might have come
out with a different report.'' Bottom line, nukes are not
necessary, except in extremely rare and unusual circumstances.
The second serious flaw in NASA's report is that NASA
failed to understand and address the fact that whenever an
asteroid passes near the Earth, for example, as the result of a
deflection, it passes through a region in which are scattered
hundreds of impact keyholes, small areas through which, if the
asteroid passes, it will return in a few years to impact the
Earth. Any deflection which causes an impacting asteroid to
avoid hitting the Earth will end up, instead, passing through
this minefield of impact keyholes. A successful deflection,
therefore, depends upon the use of both a primary deflection,
that is, to miss the Earth, using an appropriate impulsive
technique, that is, a kinetic impact, or in exceptional cases,
a nuclear explosion, and a potential secondary deflection, if
it is headed for a keyhole, using a slow push capability, to
ensure that the NEO both misses the Earth and misses the
keyholes, therefore avoiding placing it on a return trajectory
with an impact in a few years.
Again, in our meeting on June 18, 2007 with NASA, they
acknowledged that at the time the analysis was done, it did not
understand the importance of this issue. Bottom line, both
strength and precision are necessary for a successful
deflection.
Moving on, the second question I was asked to address was
which relevant factors, data, or options are not addressed in
the report, and how should NASA investigate those areas. Given
the two serious flaws in NASA's report, which I just cited, as
well as many others that are outlined in detail in my written
testimony, we recommend, number two, that NASA should produce a
supplement to its report to Congress, based on new knowledge
which has come to light since it began its analysis.
The third question Congress asked me to respond to was what
does NASA need to do now to understand and mitigate the risks
of potential NEO impact? Absent someone in NASA going beyond
the search and discovery challenge, and thinking through the
complex issues of NEO deflection, we stand justly accused of
focusing on numeric goals for the sake of meeting an abstract
quota, that is, 90 percent of so many objects, et cetera, et
cetera. We therefore recommend that NASA, our third
recommendation, that NASA should assign someone in its NEO
program to the specific task of thinking through, analyzing,
and understanding the NEO deflection challenge.
And in addition, our fourth recommendation, based on this
question, is that NASA should validate the basic NEO deflection
capability, through the execution of a demonstration asteroid
deflection mission. That is, we should not be put in the
position of doing a deflection mission for the first time when
lives actually count on it.
Finally, we were asked what governance structure should be
established to address potential NEO threats. This is, by far,
the most important question that I was asked by the Congress.
NASA, as the U.S., and arguably the world's premier space
agency, should have the responsibility for both fully
understanding the NEO deflection challenge and developing and
testing deflection technology. It does not have that
responsibility now.
Therefore, our fifth recommendation is that the Congress
expressly assign to NASA the technical development elements of
protecting the Earth from NEO impacts as a public safety
responsibility. That is, without NASA having the specific
responsibility assigned to it to develop the technical means of
protecting the Earth from NEO impacts, it will not be done.
They must be assigned this responsibility. Otherwise, there
will not be action in this regard.
The larger question, however, is to which agency of
government should the overall responsibility for protecting the
Earth from NEO impacts be assigned, not just the technical
development aspects, but the policy and political
responsibility. This inherently international issue will
involve complex and very sensitive coordination and
negotiation, and the U.S. involvement will place in the hands
of the agency responsible the lives and property of potentially
the entire population.
We, therefore, recommend as our final and sixth
recommendation that the Congress study the issue of overall
governmental responsibility for protection of the Earth from
NEO impacts, perhaps with the assistance of specialized policy
entities, and ultimately, to hold public hearings to engage a
wide perspective on this issue.
The logical candidates, obviously, for this overall
responsibility are the Department of Homeland Security, the
Department of Defense, and of course, NASA itself.
This has been, of necessity, a very cursory review of a
very important set of issues and questions. I thank you for the
opportunity to discuss them with you, and I look forward to
responding to any questions you may have.
[The prepared statement of Mr. Schweickart follows:]
Prepared Statement of Russell L. Schweickart
Mr. Chairman and Members of the Committee:
Thank you for the opportunity to testify on this important subject;
an issue of increasing interest regarding the protection of life and
property around the planet.
I represent B612 Foundation (B612), a private non-profit
corporation founded in 2002 by a group of astronauts, astronomers,
planetary scientists and engineers to advocate and develop the means of
diverting a near-Earth object (NEO) threatening an impact with Earth.
B612 has developed several alternative concepts for deflecting NEOs and
we have actively urged NASA, the Congress, and others to pursue the NEO
challenge beyond search and discovery and into mitigation and
prevention.
I will start by commending the Committee for its efforts since the
early 1990s in seeing that this public safety issue is responsibly
addressed. The impact of near-Earth objects with the Earth is properly
described as a cosmic natural hazard of potentially unprecedented
dimension, threatening both life and property. Unlike other natural
hazards, however, we can in this instance, using current space
technology, both predict and prevent the occurrence of such a disaster.
No other natural hazard presents such a wide range of potential
destruction, but in no other case are we fortunate enough to have at
hand the advanced technology and creative imagination to mitigate such
a catastrophic event. The range of explosive impacts we may be called
on to prevent extend from the ``Tunguska Event'' of 1908, approximately
a five megaton (MT) explosion over Siberia (equivalent to over 300
Hiroshima bombs) up to impacts 100,000 times larger--large enough to
destroy civilization and threaten the survival of humanity. We intend
to prevent such infrequent but devastating events by slightly and
precisely modifying the orbit of a threatening NEO, causing it to pass
harmlessly by the Earth. Stated differently, we intend, using available
space technology, to slightly alter the workings of the solar system in
order to enhance human survival on planet Earth.
To realize such a bold claim we must put in place three critical
components of a response system. They are: advanced notice (i.e., an
early warning system), a demonstrated deflection capability, and a
standing decision process to enable timely action.
The Congress, NASA, and other key global players are to be
congratulated for their excellent work in implementing the first phase
of the early warning system, the Spaceguard Survey, which has been in
operation since 1998. The Congress is to be further commended for its
vision in mandating that NASA take the next critical steps as expressed
in the George E. Brown, Jr. Near-Earth Object Survey Act of 2005 (the
Act). The Act extends the Spaceguard Survey goal, directing NASA to
``detect, track, catalogue, and characterize . . . near-Earth objects
equal to or greater than 140 meters in diameter. . .'' and to ``achieve
90 percent completion of [the survey] within 15 years after the date of
enactment of this Act.''
The Congress also directed that ``The Administrator shall transmit
to Congress not later than one year after the date of enactment of this
Act an initial report that provides the following:
(A) An analysis of possible alternatives that NASA may employ
to carry out the Survey program, including ground-based and
space-based alternatives with technical descriptions.
(B) A recommended option and proposed budget to carry out the
Survey program pursuant to the recommended option.
(C) Analysis of possible alternatives that NASA could employ
to divert an object on a likely collision course with Earth.''
It is NASA's mixed response to these three directives which prompts
my testimony here today.
I have been specifically requested to address the following four
questions;
1. What are your perspectives on NASA's Near-Earth Object
Survey and Deflection Analysis of Alternatives Report to
Congress? Do you agree or disagree with the report's findings
and recommendations?
2. Which, if any, relevant factors, data, or options are not
addressed in the report and how should NASA investigate those
areas?
3. What does NASA need to do now to understand and mitigate
the risks of potential NEO impacts?
4. What governance structures should be established to address
potential NEO threats?
1. Perspectives on the NASA Report
My response to the first question is in three parts, corresponding
to the three components of the Congressional direction to NASA.
a) Analysis of Survey Program Alternatives:
I believe that NASA did a very good job (with the exception of the
NASA life cycle cost estimation for the several survey alternatives) in
developing and comparing a set of alternative Survey designs to meet
the 140-meter goal. While I am not personally qualified to comment on
the NASA costing I note that knowledgeable Pan-STARRS and LSST
personnel challenge the NASA figures used. These experts claim that the
actual costs for both cooperative and dedicated use of such telescopic
facilities are considerably lower than those projected by NASA.
One factor not addressed in NASA's analysis of options to meet the
revised Survey goal was the capability of various search system options
for NEO tracking vice NEO discovery. While all of us in the NEO
community strongly support moving aggressively to meet Congress's 140-
meter discovery goal the fundamental intent of this enterprise is to
protect the Earth from NEO impacts. This ultimate purpose is achieved
by both the discovery of NEOs which might pose a threat AND also by
tracking them accurately to determine whether or not a deflection
campaign is necessary.
It is an unfortunate reality that ground-based telescopic tracking
produces, for many challenging NEOs, discontinuous information; data
dropouts may last for several years at a time. Should such a critical
data dropout occur just as a NEO is found to threaten an impact, the
decision on mounting a deflection campaign may well have to be made on
the basis of uncomfortably ``stale'' tracking data. The well-known NEO
Apophis, which currently has a one in 45,000 probability of collision
with the Earth in 2036, is in such a data dropout period at this time.
We were last able to see Apophis in August 2006 and we will not see it
again until 2011-2012. For Apophis this data interruption is
uncomfortable, but not critical since we will see it again before we
need to decide on a deflection campaign. This is, however, simply a
matter of chance and in many instances in the future we will not be so
fortunate.
The orbital phasing responsible for this interrupted tracking can
be eliminated by selecting any of several space-based search options in
NASA's analysis to augment the ground-based systems. While NASA reports
that overall costs for space and ground tracking are comparable (a
controversial claim), the tracking quality provided by a telescope in a
Venus-like orbit, in particular, is vastly superior. The dual-band IR
telescope is especially preferable since it also improves greatly our
estimates of NEO mass (and thus impact energy).
In summary, NEO search and discovery is extremely important. NEO
tracking, however, is equally important for deciding whether and when
to mount a deflection campaign. The dual-band IR telescope in a Venus-
like orbit offers both discovery and tracking advantages at a cost
comparable to the best ground-based telescopic options.
b) Recommended Program and Supporting Budget:
With respect to the second Congressional charge to recommend a
program to meet the 140-meter search goal and a budget to support it,
NASA failed to respond. NASA opted instead to state the obvious, that
``. . . due to current budget constraints, NASA cannot initiate a new
program at this time.'' Of course NASA's tight fiscal situation is
precisely why the Congress requested not only a recommended program but
also a proposed budget necessary to carry it out.
One can sympathize with NASA's fear of the dreaded ``unfunded
mandate'' from Congress while decrying the Agency's decision to defy
the Congressional directive and to delay the initiation of this
critical search program. Congress, however, must also recognize and
confront the dilemma it imposes on NASA (and other agencies) when it
directs action without the specific identification of funds to support
the work. Yet given that Congress explicitly directed in its mandate
that NASA provide it with a proposed budget to support the program NASA
cannot be excused.
I can only urge that the Congress should again direct NASA in the
clearest language possible to comply with the law and recommend a
search program and supporting budget. (Recommendation 1) It is time for
the Nation to aggressively pursue this urgent NEO program.
c) Analysis of Deflection Alternatives:
B612 Foundation believes that NASA's analysis of deflection
alternatives, as reported to the Congress, has serious technical flaws.
NASA's findings and recommendations misunderstand, mischaracterize, and
misrepresent many of the critical issues and options involved in the
diversion of a threatening NEO. Furthermore the NASA Report fails to
address a number of crucial issues which lie at the very heart of the
deflection challenge.
An analysis of the errors of both commission and omission are too
numerous and detailed to include in this testimony. I have therefore
attached to this written testimony, and urge the Members and their
staff to read, several documents which address these errors in depth.
These documents include:
1. An exchange of correspondence with Congressman Dana
Rohrabacher regarding clarification of the intent of the
Congress in the nature of the NEOs to be considered for
diversion (attachments 1 & 2),
2. An ``Independent Analysis of Alternatives that could be
employed to divert a NEO on a likely collision course with
Earth.'' (attachment 3; also available at http://
www.b612foundation.org/press/press.html, #15), and
3. Two detailed critiques of the NASA Report addressing on a
point-by-point basis specific errors in the NASA analysis.
(attachments 4 & 5; also available at http://
www.b612foundation.org/press/press.html, #16).
To appreciate the depth of the technical errors in the Report, I
strongly urge that these appended documents be reviewed in detail. I
will summarize here a few of the key points.
Size matters
In examining the technical alternatives for diverting threatening
NEOs, NASA selected ``. . . a set of five [note: there were actually 7]
scenarios representing the likely range of threats.'' In fact, the set
of impact scenarios NASA chose as ``typical'' were extraordinarily
challenging, resulting in a preference for a deflection concept
delivering extraordinary capability, i.e., nuclear explosives.
The least challenging of the NEOs NASA considered in its analysis
is part of a group that comprises just two percent of the potential
impact cases. The impact frequency of such an object is once every
35,000 years. The remaining objects considered by NASA range upward to
a one kilometer asteroid (one impact per million years) and a one-
kilometer, long-period comet (even more rare).
In fact, objects which hit much more frequently and yet deliver
considerable impact energy make up 98 percent of the likely impact
threat. The most likely of these objects to impact is comparable to the
Tunguska event of 1908 in Siberian Russia. That event is estimated to
have exploded with the force of about five megatons of TNT equivalent,
or over 300 Hiroshima bombs. Had the Tunguska event been instead the
``London event,'' or ``Moscow event,'' it would have destroyed not just
800 square miles of forest and a few reindeer but an entire city and
its population.
As Congressman Dana Rohrabacher stated in his clarification letter
to B612 on this subject, ``While it is important to understand what
technology exists or needs to be developed to divert the larger and
more devastating NEOs the first order of business is to insure that we
have a clear understanding of that the options are for the situations
we are most likely to encounter.''
A random impact occurring directly over a major city is, of course,
highly unlikely. Yet when the possibility of such an event and the
means of preventing it from occurring are known to exist by the general
population it is reasonable to conclude that public pressure on the
international community will successfully demand that we initiate a
deflection.
Given then a cohort of ``most likely NEOs to be deflected'' ranging
from a Tunguska-like object at the smallest and most frequent end of
the scale up to events 100 times less frequent, we find that over 99
percent of them can be deflected using non-nuclear means.
The need for the availability of nuclear explosions for deflection
in extreme cases cannot currently be ruled out, but the likelihood of
such a demand materializing over the next several decades is extremely
small. Furthermore our search efforts will make the need for such a
solution increasingly unlikely over time.
Precision matters
NASA uses the word ``effectiveness'' in its Report purely as a
measure of how much momentum change can be imparted to the asteroid.
e.g., in its ``Key Findings for Diverting a Potentially Hazardous
Object,'' the first sentence of the first finding states ``Nuclear
standoff explosions are assessed to be 10-100 times more effective than
the non-nuclear alternatives analyzed in this study.'' The technical
term for NASA's undefined word ``effectiveness'' in this instance is
``total impulse,'' i.e., the amount of momentum imparted to the
asteroid in the process of the deflection.
Without doubt the total impulse available is a key measure of any
deflection concept. However all of the impulsive (i.e., relatively
instantaneous as juxtaposed with slow) deflection techniques evaluated
are, while quite powerful, highly uncertain with regard to predicting
the precise total impulse delivered. Experts in the field estimate
uncertainties ranging from factors of two to five or even higher in the
resulting total impulse delivered by either the nuclear or kinetic
impact deflection concepts.
Certainly ``strength'' may well be needed in the deflection of an
object on an impact trajectory. The first order of business is, without
question, to ensure that the NEO is deflected sufficiently that it miss
the planet.
What NASA totally missed however is that whenever an asteroid
passes near the Earth (or any planet) it passes through a region in
which are scattered hundreds of small impact ``keyholes,'' small areas
in Earth's proximity through which if the asteroid passes it will
return within a few years and impact the Earth. Any deflected asteroid
which misses the Earth must transit this minefield of impact keyholes.
Because the percentage of space taken up by such keyholes is small
compared with the space between them the probability of the NEO passing
through one is fairly low. However the consequences of passing through
such a keyhole are severe. Thus, whether or not a deflected NEO misses
the keyholes cannot be left to chance. A successful deflection must
therefore be defined as one which causes the potentially impacting
asteroid to not only to miss the Earth but also to miss all impact
keyholes. Without this constraint any deflecting agency would be
limited to declaring, ``we successfully deflected the asteroid away
from an impact with Earth. . . and it is unlikely that it will return
for an impact any time soon.''
A successful deflection requires both adequate strength and high
precision. Immediately following an impulsive deflection the new orbit
of the asteroid must be precisely determined and examined for a future
keyhole transit. if headed for a keyhole then a small ``trim'' maneuver
can be executed using a weak but precise ``slow push'' (as NASA refers
to it) deflection to avoid that critical passage.
This combination of imprecise strength and precise adjustment is
both necessary and sufficient to declare to the world that a fully
successful deflection has been achieved. NASA completely missed this
essential point in its analysis.
These two key flaws are illustrative of the quality of the analysis
on deflection alternatives in the NASA Report. I again refer you to the
attachments for greater detail.
2. How should NASA now proceed on these issues?
I believe that NASA should produce a supplement to its Report to
Congress based on new knowledge which has come to light since it began
its analysis. (Recommendation 2) The state of knowledge of the NEO
deflection challenge is increasing very rapidly and NASA has not stayed
abreast of recent developments. This is not entirely NASA's fault since
it has no assigned responsibility in this critical area. Nevertheless
given the Congressional request for an analysis of alternatives, and
the urgent need for a legitimate understanding of these options, I urge
that NASA revisit this matter. I list below, inter alia, a few
suggestions in this regard.
a) NASA should re-examine the NEO deflection challenge
utilizing the most likely set of threatening NEOs that we will
likely confront. The lower bound of this cohort should lie in
the range of the 1908 Tunguska event. (Note: This does not
imply a change in the 140 meter search goal. In meeting the
140-meter goal NASA will discover a large fraction of the
Tunguska sized NEO cohort as well.)
b) NASA should examine the need for precision and control in
the deflection process taking particular account of the role
impact keyholes play during a deflection.
c) NASA should further review and analyze its current (and
future) database of NEOs to determine the frequency with which
close gravitational encounters occur between the time of NEO
discovery and the time of potential impact. In the case where
such encounters occur (e.g., Apophis, the most threatening NEO
in the current database) analysis shows that a single mission
can often be employed to both determine if an impact is indeed
threatened and take ``slow push'' preventive action if
necessary. We must understand this class of prospective impacts
and capitalize on the potential for a simple and less costly
deflection mission.
d) NASA should fully assess the value of a dual-band IR
telescope in a Venus-like orbit for search and tracking
purposes. NASA has already analyzed this instrument's search
capability, but it should extend its thinking to evaluate how
to use such an instrument to support our impact prevention
capability.
e) NASA should correct its faulty analysis of the cost and
technological readiness of the Gravity Tractor.
3. What needs to be done to mitigate the risks of potential NEO
impacts?
There are two key actions to be taken that would make significant
progress toward protecting the Earth from the potential devastation of
NEO impacts. Neither of them is expensive yet both of them are
extremely important, even urgent, in light of the anticipated rapid
rise in the NEO discovery rate in the near future.
a) NASA should assign someone in its NEO Program to the
specific task of thinking through, analyzing and understanding
the NEO deflection challenge. (Recommendation 3) So long as the
NASA effort, and therefore thinking, is restricted to the NEO
discovery process only, the government will lack the critical
information and understanding needed to protect the Earth from
NEO impacts. There is critical linkage between the upstream
process of NEO search and orbit analysis and the downstream
information needed to deflect NEOs. Absent someone explicitly
thinking this through we stand justly accused of focusing on
numeric goals for the sake of meeting an abstract quota. I
hasten to point out that NASA cannot make such an assignment
without being given the explicit responsibility for this
critical function.
b) NASA should validate a basic NEO deflection capability
through the execution of a demonstration mission.
(Recommendation 4) While deflection concepts can and indeed
must first be worked out conceptually, in an endeavor as
critical to public safety as deflecting an asteroid bound for
an impact, our ultimate success in such a vital undertaking
cannot depend solely on a paper analysis. A demonstration
program can be performed on a non-threatening asteroid at a
cost no more than that of a typical small scientific mission.
This effort need not, and perhaps should not, be undertaken as
a U.S. mission per se. The European Space Agency (ESA) has
already performed the initial feasibility and design phase of
such a mission (though it should be modified to validate the
``slow push'' component). Were an international partnership
agreement negotiated a reasonable cost estimate for a complete
NEO deflection demonstration campaign could be performed for
about the cost of a single scientific mission.
4. What governance structures should be established to address
potential NEO threats?
I believe this to be the single most important question of this
hearing. Until and unless an explicit assignment of responsibility
within government is made to protect the Earth from NEO impacts, no
significant advances in our capability will be made, and the US public,
and indeed the world public, will remain unnecessarily at risk.
Ironically and somewhat counter intuitively, the full cost of
assigning such responsibility and paying for its operations is almost
vanishingly small. It is, nevertheless, a sobering responsibility, and
an historic one. The very concept of being able to slightly alter the
workings of the cosmos to enhance the survival of life on Earth is
staggeringly bold. Yet this very capability lies within our technical
means today. The missing element, the fatal missing element, is a
governmental assignment of responsibility.
I would break this charge into two logical pieces.
a) First it seems to me that there exists today a single
logical entity that should be responsible for the analysis,
design, manufacturing and testing of a NEO deflection
capability. That entity is NASA. NASA is our national space
agency and is clearly charged with the development of our
national space capability. This is, I believe, a clear and
obvious choice.
NEO work in NASA is, however, administratively in an
orphaned status. Protecting the Earth from NEO impacts is
neither space science nor exploration, although there are
elements of both involved. Protecting the Earth from NEO
impacts is a public safety activity. Yet today within NASA and
its supporting space science and exploration communities the
strong perception is that a dollar spent on NEO work is a
dollar taken from space science or exploration. This ``zero-sum
game'' presumption cannot be allowed to persist. Yet until
explicit responsibility and funding for NEO research, as a
public safety responsibility, is assigned to NASA by the
Congress, this terrible conflict will persist. I therefore
recommend that the Congress expressly assign to NASA the
technical development elements of protecting the Earth from NEO
impacts as a public safety responsibility. (Recommendation 5)
b) The second element is considerably more challenging and
controversial. That is, to which agency of government should
fall the overall responsibility for protecting the Earth from
this infrequent, but devastating natural hazard? This
responsibility is greater than and somewhat separate from the
technical issues discussed above.
While we have not addressed this matter above I will simply
state unequivocally that the NEO mitigation decision process
and the policies embedded within it are inherently
international. Any NEO deflection will necessarily shift risk,
however temporarily, between people and property across the
planet. As we move a NEO away from an Earth impact, we
necessarily shift its impact point from one region to another
until we complete the deflection.
Given this characteristic, and I ask that you grant this
arguendo, the response to a threatening NEO will involve
complex and very sensitive international coordination and
probably negotiation. This is a planetary challenge, not a
national one. The policies, procedures, criteria, thresholds,
and agreements which must be addressed are international
political challenges and the U.S. involvement will place in the
hands of the agency responsible the lives and property of the
world's entire population.
It would frankly be presumptuous of me to make a specific
recommendation here. Obvious candidates for such a
responsibility include the Department of Homeland Security
(DHS), the Department of Defense (DOD), and of course NASA.
Many other agencies will clearly need to be involved in the
decision processes given the potential of evacuation, migration
(including cross border), and potentially unprecedented
property destruction.
I therefore recommend that the Congress study the issue of
overall governmental responsibility for protection of the Earth
from NEO impacts, perhaps with the assistance of specialized
policy entities, and ultimately hold public hearings to engage
a wide perspective on the issue. (Recommendation 6)
In closing I would suggest a personal perspective based on having
spent the last six years of my life studying this issue. NEOs are part
of nature. A NEO impact is a natural hazard in much the same way as are
hurricanes, tsunamis, floods, etc. NEO impacts are deceptively
infrequent, yet devastating at potentially unimaginable levels. NEOs
are however not our enemies. We do not need to ``defend'' against NEOs,
we need to protect ourselves from their occasional impact, as we do
with other natural hazards.
Unlike other natural hazards, however, NEO impacts can be predicted
well ahead of time and actually prevented from occurring. If we live up
to our responsibility, if we wisely use our amazing technology, and if
we are mature enough, as a nation and as a community of nations, there
may never again be a substantially damaging asteroid impact on the
Earth. We have the ability to make ourselves safe from cosmic
extinction. If we cannot manage to meet this challenge, we will, in my
opinion, have failed to meet our evolutionary responsibility.
Thank you.
Biography for Russell L. Schweickart
Russell L. (Rusty) Schweickart is a retired business and government
executive and serves today as Chairman of the Board of the B612
Foundation. The organization, a non-profit private foundation,
advocates the development of a space system to protect the Earth from
future asteroid impacts. The Foundation's goal is ``to significantly
alter the orbit of an asteroid, in a controlled manner, by 2015.''
Schweickart is the founder and past president of the Association of
Space Explorers (ASE), the international professional society of
astronauts and cosmonauts. .He currently serves as Chairman of the
ASE's Committee on Near-Earth Objects. The organization promotes the
cooperative exploration and development of space and the use of space
technology for human benefit. The ASE has a current membership of over
390 astronauts and cosmonauts from 31 nations. The Association's first
book, The Home Planet, with a preface by Schweickart, was published
simultaneously in 10 nations in the Fall of 1988 and was an immediate
international best seller.
In 1987-88, Schweickart chaired the United States Antarctic Program
Safety Review Panel for the Director of the National Science Foundation
(NSF) in Washington, DC. The resulting report, Safety in Antarctica, a
comprehensive on-site review of all U.S. activities in Antarctica, led
to a restructuring of the program, increasing the safety of operations
in that hazardous environment. At the request of the National Science
Foundation, Schweickart also served on the 1997-1998 United States
Antarctic Program Outside Review Panel, which reported to the White
House (OSTP) and Congress on the future of U.S. facilities in
Antarctica. The U.S.' Amundson-Scott South Pole station is currently
being fully rebuilt as a result of this work.
In 1977 Schweickart joined the staff of Governor Jerry Brown of
California, and served in the Governor's office for two years as his
assistant for science and technology. In 1979 Schweickart was appointed
to the post of Commissioner of Energy for the State of California and
served on the Commission for five and a half years. The Commission,
which was chaired by Schweickart for three and a half years, was
responsible for all aspects of energy regulation in the state other
than rate setting, including energy demand forecasting, alternative
energy development, power plant siting and energy performance
regulation for appliances and buildings.
Schweickart joined NASA as one of 14 astronauts named in October
1963, the third group of astronauts selected. He served as lunar module
pilot for Apollo 9, March 3-13, 1969, logging 241 hours in space. This
was the third manned flight of the Apollo series and the first manned
flight of the lunar module. During a 46 minute EVA Schweickart tested
the portable life support backpack which was subsequently used on the
lunar surface explorations. On the mission with Schweickart were
commander James A. McDivitt and command module pilot David R. Scott.
Schweickart served as backup commander for the first Skylab mission
which flew in the Spring of 1973. Following the loss of the thermal
shield during the launch of the Skylab vehicle, he assumed
responsibility for the development of hardware and procedures
associated with erecting the emergency solar shade and deployment of
the jammed solar array wing, operations which transformed Skylab from
an imminent disaster to a highly successful program.
After the Skylab program, Schweickart went to NASA Headquarters in
Washington, DC as Director of User Affairs in the Office of
Applications. In this position he was responsible for transferring NASA
technology to the outside world and working with technology users to
bring an understanding of their needs into NASA.
Prior to joining NASA, Schweickart was a research scientist at the
Experimental Astronomy Laboratory of the Massachusetts Institute of
Technology (MIT). His work at MIT involved research in upper
atmospheric physics, star tracking and the stabilization of stellar
images. His thesis for a master's degree at MIT was an experimental
validation of theoretical models of stratospheric radiance.
Schweickart served as a fighter pilot in the U.S. Air Force and the
Massachusetts Air National Guard from 1956 to 1963. He has logged over
4000 hours of flight time, including 3500 hours in high performance jet
aircraft.
Schweickart was awarded the NASA Distinguished Service Medal (1969)
and the Federation Aeronautique Internationale De La Vaux Medal (1970)
for his Apollo 9 flight. He also received the National Academy of
Television Arts and Sciences Special Trustees Award (Emmy) in 1969 for
transmitting the first live TV pictures from space. In 1973 Schweickart
was awarded the NASA Exceptional Service Medal for his leadership role
in the Skylab rescue efforts.
He is a Fellow of the American Astronautical Society and the
International Academy of Astronautics, and an Associate Fellow of the
American Institute of Aeronautics and Astronautics. Schweickart is a
Trustee and a Fellow of the California Academy of Sciences.
Schweickart was born on 25 October 1935 in Neptune, NJ. He is
married to Nancy Ramsey of West Hartford, CT. He has seven children and
eleven grandchildren. He graduated from Manasquan High School, NJ;
received his Bachelor of Science degree in 1956 and his Master of
Science degree in 1963, both from the Massachusetts Institute of
Technology.
His hobbies include golf, bicycling, and hiking.
Discussion
Mr. Lampson. Thank you, sir, very much. Thank all of you,
the whole panel. It is really been a pretty fascinating topic
for us to be taking up.
At this time, each Member will be given five minutes to
question the panel, and I will yield myself, as Chairman, the
first five minutes.
Importance of Surveying Objects Larger Than 140m
And Dr. Yeomans, is it correct that you pretty much agree
with the importance of surveying all potentially hazardous
objects, down to 140 meters in size?
Dr. Yeomans. Yes. I think that is the next step. By doing
so, by finding 90 percent of these objects, we would
effectively reduce the risk of all Near-Earth Objects to Earth
by 99 percent. Now, Rusty mentioned the smaller objects still,
but that could be the subject of a third generation search. But
the 140 meter and larger objects are primarily, necessarily the
focus of the next survey.
Mr. Lampson. Well, the Authorization Act of 2005 directs
NASA to implement a program to catalog 90 percent of all the
140 meter or larger NEOs by the end of 2020. Is that still a
realistic goal, or should the scope or timetable be adjusted,
and if so, what would you recommend that new goal to be?
Dr. Yeomans. Well, I think the 2020 timeline was selected
because we needed some sort of a metric to judge progress by,
but it has been pointed out that the impact interval for a 140
meter sized object is about 5,000 years, so my personal opinion
would be that we could afford to wait another couple of years,
and perhaps do the survey by the end of 2030 or thereabouts,
and explore some options that would be easier and less
expensive to carry out within that timeframe.
Risk of Changing the Project Timeline
Mr. Lampson. Maybe our technology even would have grown
more, and we will be able to do it more effectively, or at a
lesser cost.
Dr. Tyson indicates that the LSST could meet the 90 percent
goal by 2026, at an average cost to NASA of about $10 million a
year for 12 years. From a risk reduction standpoint, how
serious would a 6-year delay in meeting that Congressional goal
be, and would anybody else after that, after your comment,
would anybody else like to make a comment on it?
Dr. Tyson. I think that the risk reduction is significant,
if one is able to go down to these small sizes. In 12 years, as
opposed to 10 years, my personal opinion is the same as Don's.
I think that one has to just get on with it and do these
surveys, and if it takes 12 years instead of 10 years to reach
90 percent, then we should just do that.
Mr. Lampson. Dr. Yeomans, would you comment also, please?
Dr. Yeomans. I agree with what Tony said. I would like to
see, perhaps, an extension of our report to Congress, whereby a
few options are looked at in far more detail, in a more
rigorous fashion, and costing is done in a more rigorous
fashion. And perhaps one of the options, one of the few options
that would be examined, would be the LSST, working in
cooperation with Pan-STARRS, and also one, perhaps two space-
based options. Infrared surveys are still very effective, but
that would be my suggestion.
Non-U.S. NEO Characterization
Mr. Lampson. Anybody else want to make a comment on that
before I ask my next question? Okay, let me go on, because we
are going to get to all of you.
Dr. Yeomans, what if any contributions are non-U.S.
organizations or agencies providing to the detection, tracking,
and characterization of NEOs?
Dr. Yeomans. Well, as was pointed out, in terms of
discovering them, NASA is doing the lion's share of the work,
certainly more than 98 percent of all discoveries are by NASA-
supported facilities. But there are international efforts
underway to characterize these objects. Our colleagues in ESA,
the European Space Agency, are making strides. The Japanese
have a mission currently underway to visit a Near-Earth
asteroid and bring a sample back, so that is important.
We have a group at Pisa, Italy, that is also working with
us very closely to determine independently impact probabilities
for various objects, and so, we are constantly in touch with
those folks to verify our results, and they are doing the same,
and verifying their results with us, and if we come up with
interesting objects like Apophis, for example, the object that
will get very close to the Earth in 2029, we wait until we have
verified our results with our colleagues in Italy before we
make any formal announcements. So, that is working very well.
Increasing International NEO Collaboration
Mr. Lampson. Is there more that should be done? And if so,
what steps ought to be being taken? Can we build greater
relationships, obviously through science we can, but is this
one of those areas?
Dr. Yeomans. I think it is. We should continue to encourage
our international colleagues to participate more in the
discovery area, more in the characterization area. And those
activities are ongoing, through the Action Team that was
mentioned, the UN Action Team 14, for the Peaceful Uses of
Outer Space. So, those international discussions are going on.
We certainly would appreciate more international efforts in
these areas.
Mr. Lampson. Dr. Green, what if any plans does NASA have to
engage other nations or international entities in efforts to
direct and characterize NEOs?
Dr. Green. Currently, through our bilateral discussions
with many of the other space agencies, such as ESA, such as the
Canadian Space Agency, this is, indeed, a topic that comes up
on every agenda. And indeed, we do see, as I mentioned in my
testimony, growing international interest in this area. There
are several missions that ESA has been studying, and most
recently, in what they call Cosmic Visions, there is another
mission called Marco Polo, that does have a much better chance
now of making it through their budgetary process, that will
also add information that is important for us.
The Canadians will be launching a spacecraft called
NEOSSat. We have been discussing about how it can be utilized,
and making the data more available. So, indeed, in summary,
that interest now is becoming more international. It is getting
into the plans, future plans of our space agency partners. And
as I mentioned, it is, indeed, a topic that we will continue to
discuss and promote.
Mr. Lampson. Anyone else want to--Mr. Schweickart.
Public Safety
Mr. Schweickart. Yes, Mr. Lampson. Let me simply second
what has been said, but go a bit beyond it. I think one of the
most important things that can come out of this hearing is to
explicitly recognize that what we are discussing here is not
science. What we are talking about here is public safety. This
is not a subject in which relatively small amounts of money,
frankly, should be traded off with the scientific research that
goes on in NASA and elsewhere.
We are talking here about two separate things, and they
should not be mingled and seen as a zero-sum game, which is the
way in which expenditures for issues related to Near-Earth
Objects are seen by many people today. This is not a zero-sum
game. We are talking about two things. One is science and
exploration. Another is public safety. And we should not
sacrifice public safety for science. These things are very
important.
I think when you go to the international community for
additional support, it would be very helpful if the U.S., in
its presentations in COPUOS, in the United Nations, were to
appeal for additional support, on the basis that we are talking
about, public safety on a worldwide basis. I think that may
make a real difference.
Thank you.
Mr. Lampson. Thank you very much for your comments. Anyone
else? Thank you very much. I will yield the next five minutes
to Mr. Feeney, the Ranking Member.
Mr. Feeney. Well, thank you, Mr. Chairman, and I am struck
by your remark, Mr. Schweickart, that the way to appeal for
international support on this is through safety and security,
and I happen to agree with that. I mean, a lot of exploration,
especially space exploration, is not a zero-sum game, but there
are winners and losers. There are property rights issues. There
are capabilities, in terms of geopolitics. But certainly, when
you are talking about the potential to deflect a threat to the
entire Earth, it seems to me that had the dinosaurs had the
capability to deflect these things 65 million years ago, they
might still be around. And maybe we can convince some of our
international partners to bear some of the load; this is a win-
win for everybody involved.
NEO Deflection Technology
So, because there are so many fascinating parts of this,
Dr. Yeomans, your remarks did not specifically talk about the
technology that Mr. Schweickart did. You said that existing
technologies can deflect an Earth-threatening asteroid if there
is time. Can you describe those technologies, and can you give
us your assessment of Mr. Schweickart's discussion of nuclear
versus kinetic and the size of the objects?
Dr. Yeomans. Well, there is basically two groups of
mitigation techniques. There is the fast, flyby, or impacting
techniques. You run into it, as we did with the Deep Impact
mission, back in July of 2005, and simply slow the object down,
if it is small enough to do that, and you have time enough, so
that in 20 or 30 years time, when it was predicted to hit the
Earth, its orbit would have been changed, so that it wouldn't
hit. So, there is the fast or impulsive techniques, where you
run into it, or if it is a large object, you would use nuclear
explosives, perhaps.
And then, there is the slow push techniques, where you
rendezvous with the object, fly alongside it, and you do a
number of techniques, possibly. A gravity tug has been
suggested, where you just take your spacecraft, and put it up
next to your asteroid, and just use the gravitational
attraction between the two to move them just a little bit. Now,
that is a technique that, as Rusty pointed out, can be used for
so-called trim maneuvers. That is not what you would do
primarily, but you would use that as a secondary device to
alter the orbit of the object, in the event that your primary
technique, the impulsive technique, perhaps didn't do the job,
or knocked it into one of these subsequent keyholes that he
talked about, where a subsequent impact would be likely.
So, in any event, you need a spacecraft nearby to verify
the result. That is clear, so--or that would be the optimal
technique. So, again, you have to find them early to allow that
to happen.
Mr. Feeney. Mr. Schweickart, staying on the deflection
capabilities for a second. You know, NASA says the slow push
mitigation techniques are the most expensive, and we are
furthest behind in technological capabilities. You seem to have
a very different view from NASA's preference for a nuclear
device.
In terms of whether we use the slow push versus nuclear, in
terms of where we could intercept a Near-Earth Object, is there
a difference, in terms of when we can intercept the object in
the two techniques, and what are the relative advantages and
disadvantages, depending on size of the NEO?
Mr. Schweickart. Yes, thank you very much for the question.
First, let me endorse everything that Don just said in
response to your earlier question. I don't think we have any
daylight between us, frankly. I think the daylight is between
what Don just said and what I also believe, and what the NASA
report to Congress said. There is quite a bit of difference in
there.
Mr. Feeney. Let me say that NASA knows we have nuclear
capabilities, and they know that they had a mission with one
kilometer NEOs. What they did was to take the limited number of
threats that they knew how to deal with very comfortably, but
they avoided the more complex and more numerous problems. Is
that maybe----
Mr. Schweickart. Yes, I think that is a fairly good
representation. Let me give you an idea that the nuclear, I
would not, our organization would not suggest that nuclear can
be ruled out. However, statistically, if you look at the
probability of needing to use nuclear, as opposed to nonnuclear
means, the frequency of that occurrence would become necessary
about once every 100,000 years. So, you are talking about a
very improbable frequency of need, and it is that issue which
we have with what appeared in the NASA report.
And let me emphasize, again, that as I stated in my report,
that NASA in our discussions with them after they submitted
their report, acknowledged that they did not fully understand
this issue at the time the report was written. Don has now
reflected, in fact, a current, and I believe a view which we
totally support and agree with.
Let me go to something which you mentioned, which is an
extremely important, let me say misperception, and that is that
in some way, what we are talking about is a slow push technique
versus nuclear or kinetic impact. The thrust of my, no pun, the
thrust of my testimony is to point out that both strength and
precision are needed for a successful deflection when an
asteroid is headed, let me say, for a direct impact with the
Earth. You need the strength of a kinetic impact, in general or
under exceptional conditions, a nuclear explosion, but you need
to follow that up, potentially, if in fact, the deflection has
now caused the asteroid to head for a keyhole which will cause
it to come back, you need now this trim capability of the slow
technique, gravity tractor or other slow technique, which can
make a precision correction, to ensure that you don't have that
asteroid coming back and hitting. Those two things are
necessary for a successful deflection.
Now, the one final thing which you mentioned, and we have
not addressed it yet, but it is very important, and that is
that NASA did not, in completing its report on the deflection
capabilities, understand that the precision deflection that we
are talking about could be done with existing space hardware.
They used, for their analysis, the assumption of a very large,
very complex spacecraft for a gravitational tractor, and that
was incorrect. It was a misunderstanding, and in fact, that
error should be corrected. Existing ordinary technology can be
used, it is very mature, and it is very inexpensive, in fact.
Deflection of NEOs into Keyholes
Mr. Feeney. Just very briefly, with my colleagues'
indulgence. I am fascinated by these keyholes. So we are
successful with the deflection for the time being, we miss, and
it, for whatever reason, it comes into a keyhole. Don't we get
a second shot to play ping pong with the thing?
Mr. Schweickart. The basic sequence, which Don outlined,
and which we advocate, is that any, first of all, we don't talk
about a deflection mission. We should be talking about a
deflection campaign, because one of the things that you need to
have in place at the asteroid that you intend to deflect is a
transponder, a spacecraft that has rendezvoused with it that
has a transponder, so that we can do precise radio tracking.
Number one, we need to determine, in fact, is that asteroid
headed for an impact with the Earth. Number two, if it is, then
you send up a deflection mission, a strong one, a kinetic
impact, to make the primary deflection so that it misses the
Earth.
The next thing you do is go over to it with that same
spacecraft which has now been observing that impact, to again
precisely determine the success of that primary deflection, and
very important, is it now going to pass through one of these
nearby keyholes. If, and it is improbable, but if it is heading
now for a keyhole, then you need to make a small adjustment in
the deflection, using that same spacecraft with the transponder
that has a gravity tractor capability, to make a small
adjustment to make it miss that keyhole. Now, you have missed
the Earth and all return keyholes, and therefore, you have a
successful mission.
That is a deflection campaign, involving basically two
spacecraft.
More on International Collaboration
Mr. Feeney. Mr. Rohrabacher.
Mr. Rohrabacher. Thank you very much, and I have certainly
found this hearing to be fascinating, as I expected it to be,
and I would hope that we attract enough attention from the
general public and from decision-makers, to understand that
there are some things that we have to do, and I certainly agree
with Rusty when he suggests that this is a safety issue and not
a science issue. I would call it planetary defense, for lack of
a better description, and I would hope that as we do enlist
others, our European allies and the Japanese and others, I
would hope that we also include the Russians in this equation
as well. No one mentioned the Russians. I think a Russian-
American partnership in this endeavor, I think they have a lot
to contribute, and I think it would go a long way towards
establishing the type of cooperation we need in space with the
Russians.
Probability of a 10km NEO Hitting Earth in the Near Future
And with that, I see Arecibo, when we talked about, is a
short-term issue in what we are talking about here. I mean,
Arecibo is step number one, and we've got to get that done, and
then, we are talking about this further threat. I understand
that the object that hit the Earth and now is being credited
with eliminating the dinosaurs happened about 65 million years
ago, but I understand that they say that an object like that,
odds-wise, would be about every 50 million years. So, are we
not now in a cycle that would put us in the probability that
there is another such object that may head to the Earth, not in
the near future in terms of our lifetime, but in terms of the
lifetime of the planet? Is that accurate to say?
Dr. Yeomans. If I may respond. Statistically, the
likelihood of an object that size happening, first of all, that
was a 10 kilometer sized object, and there currently are no
potentially hazardous asteroids that are that size. The largest
is Toutatis, which is 5.4 kilometers, so we are not likely to
see another dinosaur-like event.
And the probabilities are such that an impact of an object
of a particular size could happen tomorrow. It could happen in
5,000 years. So, they are not really on cycles, as such.
Mr. Rohrabacher. Well, but we are just talking about the
levels of probability or likelihood, and people chart out what
these objects are, you know, every so many thousand years, you
can expect something to happen, just with the likelihood of the
objects that are out. I think we are just talking about
mathematical likelihood, and not necessarily anything else.
Apophis NEO
I would like to note that just a few years ago, there was a
Near-Earth Object that passed between, or at least as close to
the Earth as would have been between the Earth and the Moon, it
was that close, and we didn't actually see it until it was
actually past. And when you are talking about Apophis, it is a
Near-Earth Object, that as we say, and I think Rusty mentioned
it, in 2029 is when it will come close to the Earth.
Is it true that we do not know if that object will, after
it goes past the Earth the first time, that we do not know if
the Earth's gravity will actually impact its trajectory to the
point that it then becomes a threat? Is that correct?
Dr. Yeomans. That is correct. Apophis will make a close
approach on April 13, 2029, Friday the 13th.
Mr. Rohrabacher. Friday the 13th.
Dr. Yeomans. It is within 4.5 Earth radii of the surface,
well within the geosynchronous altitude of our satellites.
Mr. Rohrabacher. So, it is actually closer than some of our
satellites.
Dr. Yeomans. It is.
Mr. Rohrabacher. And we don't know what the Earth's gravity
will do to that trajectory, and so, it may, 10 years later, we
may, as Rusty is talking about a campaign, we may be facing a
second onslaught that may be even more dangerous 10 years
later.
Dr. Yeomans. Well, it has a one in 45,000 chance of passing
through one of these keyholes that Rusty mentioned, and hitting
us in April 13, 2036, but with the help of radar, Arecibo and
Goldstone in 2013, we have a 95 percent chance of eliminating
that threat altogether. So, it is a very unlikely situation,
and one that we can drive to zero, probably.
Understanding the Threat Posed By NEOs
Mr. Rohrabacher. Now, I will tell you that unlikely is, I
remember the very first hearing we had on this, and I keep
remembering, maybe it was one of you, we suggested the chances
of anyone ever being hurt on this planet by a Near-Earth Object
is, you know, about the same chance as you getting a royal
straight flush in Las Vegas, and it just happens that I had
gone to Las Vegas and got a royal straight flush once, and so,
that is really actually what made it real for me, is when
someone said that. And also, now, I have three children at home
that are three years and three and one-half years old. We are
not just talking about my lifetime or your lifetime, we are
talking about their lifetime as well.
So, I think that Rusty calculated right. However, let me
just note, from what you said, Rusty, that you know, this is,
when we are dealing with people, we have got to deal with this
as a safety issue. It shouldn't be a tradeoff for science. That
works internationally, maybe, and it may not work, in terms of
getting the job done here. But that may be the only type of
trading game that we can do here on Capitol Hill and still get
the job done.
And this issue is a priority for me. As far as I can see,
we need to understand the threat, and that is what we are
talking about right now. We don't even fully understand the
threat yet. Then we need to know what we should do, which is a
matter of discussion, and we have not even come close to that
yet.
Future Responsibility
And finally, we need to know who is going to be in charge
of doing what needs to be done. And so we need a lot of
discussion on this, and make those determinations. We are just
now at the ``should we even take the steps necessary to
understand the threat'' stage, and I think there is no question
about that.
Rusty, do you want to comment?
Mr. Schweickart. Yes. I think it is very important, your
last point, Congressman Rohrabacher. What we know now is that
NASA is responsible. NASA is in charge of discovering,
tracking, cataloging, et cetera, Near-Earth Objects. What we
also know, but we don't seem to acknowledge, is that no one is
in charge of protecting the Earth from impacts.
Mr. Rohrabacher. Right.
Mr. Schweickart. So, that next step is extremely important.
At the moment, NASA has not yet adequately thought through the
deflection issues. They have not, because they have not been
told to. They do not have that responsibility. Until NASA or
someone is given the responsibility to think through all of the
implications and decisions and international cooperation, et
cetera, for protecting the Earth from impacts, not just finding
them, that job will not be done.
So, this is extremely important.
Mr. Rohrabacher. All right. Mr. Chairman, I would suggest
that that is our job, that is our job as Congress, is to
designate who is going to be responsible for that, what Rusty
was just talking about, and we should do that in this session
of Congress. It is that important an issue, and if another
Near-Earth Object sneaks up on us, and we don't even know who
we are going to, what procedure we are going to use to try to
thwart the threat, then we haven't done our job.
Thank you very much, and I appreciate you, Mr. Chairman,
and yield back.
Chairman Udall. Thank you, Mr. Rohrabacher. We, as you all
know, have another vote underway. I am going to recess the
Committee for a very short period of time, given it is one
vote, and we will return as quickly as we can, and continue the
questioning. We will have another round. I know Mr. Feeney
intends to return, and I will see if Rohrabacher wants to ask
another round of questions when we reconvene the Committee.
So, the Committee stands in recess.
[Whereupon, at 11:40 a.m., the Subcommittee was recessed,
to reconvene at 12:08 p.m.]
Chairman Udall. The hearing will reconvene. Again, I want
to thank the panel for your forbearance with all the votes. We
do, I believe, have another vote in an hour, so I understand
that we can probably conclude the hearing in the hour we have
left to us.
Potential NASA Partnerships
At this time, the Chairman will yield himself five minutes.
And I would like to focus, Dr. Green, on the testimony, as
delivered by you and Dr. Pace, recommends that NASA continue
the existing Spaceguard survey and also take advantage of
opportunities using potential dual use telescopes and aircraft,
and partner with other agencies, as feasible, to make progress
toward achieving the legislative goal.
We have heard today at least two examples of potential
partnerships with other agencies supporting the planetary radar
at Arecibo and funding the NEO operations of the LSST, that
would make significant progress toward achieving the
legislative goal for NEO detection and tracking at, I believe,
a modest annual cost to NASA.
What, specifically, is NASA doing to take advantage of
either of these two potential partnership opportunities?
Dr. Green. Indeed, we do want to continue on with our
discussions with NSF for the use of the LSST. We have,
certainly, an infrastructure in place with the Minor Planet
Center, and our ability to utilize that data for NEO detection
and orbit determination.
Also, I had mentioned in my testimony the importance of
using the Pan-STARRS system that the Air Force is currently
putting into place, and in fact, we have provided them with a
small amount of funds to be able to upgrade their software such
that they are able to do some tracking, which is extremely
important, and they have been very receptive. And that
relationship is also quite strong.
So, our intent is, indeed, to leverage these two important
facilities as they are available, and as they come online.
NASA Funding NEO Partnerships
Chairman Udall. Thank you, Dr. Green. To follow on, I
wanted to ask if you have entered into any concrete discussions
with NSF or DOE on potential partnerships addressing this
Congressionally directed NEO survey task, and if not, why not?
Dr. Green. Okay. Indeed, as I mentioned, we have concrete
discussions with the Air Force, utilizing the Pan-STARRS
system, and they are fully aware of what our intent is. NSF,
indeed, is aware of our interest in using the LSST, and I
anticipate that within this next year, that those discussions
will become more firm, as we do understand how the funding
becomes available for them to be able to actually build that
system.
Chairman Udall. Thank you, Dr. Green. To continue this line
of inquiry, you mentioned that you are providing funding to the
Air Force for Pan-STARRS. Did NASA do an analysis of the
relative merits of providing NASA funding for Pan-STARRS,
versus funding for the LSST or the Arecibo Planetary Radar,
before deciding to give these resources to the Air Force? And
if not, why not, and how much money is being provided, and
where is it coming from in NASA?
Dr. Green. The funding that we are utilizing to support
small upgrades in the software for Pan-STARRS is a fairly
modest amount. I would have to come back to the record to give
you the exact amount, but it is within the $100,000 to $200,000
range.
[The information follows:]
Material Requested for the Record
The NASA Near Earth Objects (NEO) Program started limited funding
to the Pan-STARRS project in 2007 with a partial award to a proposal
submitted to the program by the University of Hawaii, who manages the
Pan-STARRS development for the Air Force. This partial award was a one-
year grant to the University of Hawaii of $450,000. Any future funding
will depend on the success of pending and future proposals Pan-STARRS
submits to competitive opportunities of the NEO Program that NASA
announces through its annual Research Opportunities in Space and Earth
Sciences.
Indeed, what we have arranged, with time, has been
utilizing the funding for our NEO search opportunities with
NSF, as Arecibo's telescope, by allowing us to increase the
number of observers on utilizing that facility, with time. And
then NSF taking over more of the operational activities. And
then, we are following the National Academy report that did,
indeed, suggest that NSF should support their ground-based
facilities, and that allows us to better utilize the funding
that we have available.
Chairman Udall. Is NASA prepared to consider providing
funding to Arecibo or the LSST project, as is being done with
Pan-STARRS? And again, if not, why not, and if I can add a
comment, why wouldn't it be logical to support those other
activities, if you are prepared to support Pan-STARRS?
Dr. Green. Well, currently, our arrangement with NSF has
been to follow the NRC report that came out in 2001, which
delineated roles and responsibilities for the funding of
infrastructure. Indeed, we have worked with NSF in the past to
be able to develop Arecibo capability for its radar use, and
therefore, we leveraged that, as the rest of the community
does, for that kind of research.
So, with respect to that, I believe we have a working
relationship is what it boils down to. NSF is funding their
infrastructure capability. We are able to, with time, as I
mentioned with Arecibo and also with the Pan-STARRS system,
that the Air Force provide incrementally small amounts of funds
to be able to meet and satisfy our requirements and needs, and
that has worked extremely well, and we will continue to pursue
that approach in the future.
The LSST activity, of course, is one that needs to be
resolved, in terms of whether they will have sufficient
funding, and be able to put together the capability before we
can begin to figure out how to work with them and leverage that
system.
Chairman Udall. Dr. Yeomans or anybody else on the panel,
would you care to comment?
Dr. Yeomans. I would just like to add that the modest
funding to Pan-STARRS was done under a peer review process.
They submitted a proposal to the Near-Earth Object Observations
Program in NASA Headquarters, which is a modest program in and
of itself, and it was thought at the time that their proposal
was of sufficient merit that it should be awarded this modest
sum. So, that was the process by which Pan-STARRS was funded at
a modest level.
Chairman Udall. Anybody else on the panel would like to
comment? Dr. Campbell.
Dr. Campbell. If I may, I would, just on the Arecibo
situation, like to comment that perhaps the NSF hasn't read the
NRC report, but it is my understanding they feel strongly that
the solar system research, and especially research related to
the NEO issue, is a NASA responsibility, and that they are very
reluctant to provide additional funding to carry out that
activity.
Their plans to act on the recommendations of the Senior
Review to reduce Arecibo's operating budget to $8 million, the
concern, as Dr. Green just pointed out, is that NASA feels that
they shouldn't really be supporting the operations of a
National Science Foundation facility, as opposed to supporting
some of the science which makes use of it. And what we are
talking about here are the operational costs of the radar
system at Arecibo.
Chairman Udall. Dr. Tyson.
Using LSST for NEO Detection
Dr. Tyson. Yes, thank you. I would like to make a couple of
comments. First of all, the progress, we are on schedule on
LSST towards a first light in 2014. We have a grant already
from the National Science Foundation for R&D. We are about two-
thirds of the way through that. We have put in, earlier this
year, a construction grant, a construction proposal to the NSF.
We just had this review, a very good positive result from that,
and we are going towards readiness, into the National Science
Board. So, we are on schedule, actually, for a 2014 first
light.
What is needed here to address this modified mission,
beyond what we intend to do, this extra 15 percent of Near-
Earth asteroid observing, is some extra support, starting now,
with the collaborating with the computer science community on
new ways of linking the small tracklets that one has when you
take multiple images. Each one of these, LSST will see about
150, each one of these small asteroids, about 150 times. You
have to link all of these little tracks together.
The problem is, the challenge is this. I just wish we had
special glasses that we could put on when we look out at the
night sky, and we only see the nearby Earth-threatening
asteroids. Unfortunately, when you look out deeply in the night
sky for things that are moving, you are confusion limited by
this huge cloud of 10 million main belt asteroids, and you
actually have to track all of those guys. You actually have to
know each one of those orbits in order to separate out the
Earth-threatening ones. So, that is the challenge, and that
takes a lot of, millions of lines of computer code. There are
some clever computer scientists out there that think they have
a solution to some of those problems, and we need to get on
with it. That is about $1 million a year, starting in next year
or the year after, four or five years, and then we will have
the software in place. And then, that extra 15 percent effort
would cost us somewhere around $12 million a year during
operations.
Radar Versus Optical NEO Detection
I wanted to make a comment, if I may, about radar versus
optical. I think you need both. One is not the replacement for
the other. Radar is not a method of discovering all of these
things, and winnowing down this 10 million objects into the few
that are threatening. But once you have done that with optical,
then radar is absolutely critical on the ones that you are
really concerned with, to refine the orbit.
Importance of Arecibo Radar
Chairman Udall. Mr. Schweickart.
Mr. Schweickart. Yes, Chairman Udall. I would like to just
pick up on where Tony left off, and give slightly different
language, perhaps, or perspective on the Arecibo radar and its
criticality.
As Tony said, these two are not, I mean the Arecibo radar
is not simply another thing to look for asteroids with. Number
one, radar is not a good instrument to find or discover, to
meet the quota that you guys have essentially dumped on NASA,
you know, a certain number by a certain year. However, when
what you are looking at or thinking about is protecting the
Earth from impacts, picture yourself with a few hundred
baseballs headed for your head. If you willingly take your pen
and poke out one eye, you are now left with monocular vision.
You don't have binocular vision. And if you want to get depth
perception, you need both eyes. And yet, what we are doing is
we are about to head into a serious decision-making process
over the next 15 years on do we or do we not have to deflect
something, and what you have done is, if you eliminate Arecibo,
is you wiped out, willingly, your binocular vision.
Now, that is extremely important. It is a little different
way of thinking about the essential nature of Arecibo. It
complements the optical view, and the most critical decisions
we are going to make, or the most frequent ones, are the
relatively small objects, which are numerous, which we are
going to have to make decisions about. Those are the very ones
that you get the least amount of data on, and where the Arecibo
contribution is extremely critical. Because the next time you
see that asteroid, it may be on final approach, and that first
vision you get of it needs both optical and radar, you need
both eyes.
So, that is a different take on it. But it is not meeting
the search goal which NASA has been assigned. It doesn't help
in that, but it does help if what you are interested in is
protecting the Earth.
Chairman Udall. Thank you. That is very, very helpful to
get that perspective.
The Chair now recognizes, as we begin another round, the
Ranking Member, Mr. Feeney.
Mr. Feeney. Thank you, Mr. Chairman.
Radius of NEO Surveys
This first question is for Dr. Tyson, Mr. Schweickart, Dr.
Yeomans, and Dr. Campbell. The NASA recommendations are that we
survey objects that come within .05 AU of Earth's orbit,
instead of 1.3 AU, as required by the 2005 authorization. Do
you agree or disagree with that recommendation, and why don't
you give us some comments? If we need to change our
recommendation, this is a place to start discussing it.
Dr. Tyson. Congressman, I do agree with that. If you are
calculating, if you are interested in, as I think we are,
completeness in a survey of Earth-threatening objects, then you
should have a survey of Earth-threatening objects, and those
are the ones that come within----
Mr. Feeney. Is .05 the number? Do you think that is a
reasonable number?
Dr. Tyson. That is right.
Mr. Feeney. Okay.
Dr. Tyson. I agree with that.
Ramifications of an Asteroid Hitting Earth
Mr. Feeney. Okay. And no dissension? Okay. If anybody has
an opinion, they agree with you, Dr. Tyson. I want to get an
idea of the potential ramifications from a strike of Earth. A
couple of months ago, we had a one meter object strike in Peru,
roughly. We think it created about a 13 meter crater. Is that
impact, I mean, if I am looking at a 100 meter object, am I
looking at, you know, 1.3 kilometer crater? If I am looking at
a kilometer object, am I looking at, you know, 13 kilometers?
And outside the actual kinetic strike, and the damage done
by things being broken apart by the actual collision, are there
other things, like radiation or heat, or damages that would
impact the environment or humans? This is for anybody who
wishes to----
Mr. Schweickart. Mr. Feeney, a relatively easy number is a
100 meter object is about 100 megatons of explosive energy, or
picture it as 100 one megaton nuclear bombs going off in one
place without the radiation, without the nuclear radiation
issue. But the explosive force is tremendous. Now, the other
effects, I mean, the detailed effects of shock and that sort of
thing, or even if there is a crater in the ground, are not as
significant. When you talk about an explosion in the low
atmosphere equivalent to 100 megatons, the impact on the ground
is tremendous. The Tunguska event is thought today to have been
about a five megaton explosion.
Mr. Feeney. That was in 1908?
Mr. Schweickart. 1908. We are celebrating the hundredth
anniversary of that event next year, celebrating----
Mr. Feeney. We are very familiar with floods and hurricanes
in Florida. We refer to things as a 10 year event, a 20 year
event, a 100 year event. What was the 1908 event, in your
estimate? Is that one in 5,000 years, one in 100?
Mr. Schweickart. Well, it is about a one in 600 to 800 year
event, something like that. The size estimates have recently
come down, so the frequency at which it occurs has gone up
slightly. But I think the point is that that explosion, which
flattened 2,000 square kilometers of forest and set them afire
in Siberia. Luckily, it didn't kill anyone, maybe one person,
that was only about a five megaton event, and it never got to
the ground, there is no crater. But the impact would have wiped
out all of London or Moscow or Washington, D.C., or any other
city, had it unfortunately come, or exploded over one of those
cities.
So, the impact of these things does not necessitate a
crater in the ground, but they are extremely powerful, even
down to objects as small as, say, 40, 45 meters in diameter.
Mr. Feeney. Dr. Tyson.
Dr. Tyson. Yes. I would like to point out that it certainly
would ruin my afternoon if one of these things hit close to my
house. But most of the Earth's surface is covered by water, and
studies of the actual physical damage from objects that are
less than about a few hundred meters in size come really from
the tidal waves that are set off when these objects would hit
the ocean. There is much more danger that all coastal cities
would experience a huge tsunami from such objects.
The actual physics of what happens with larger objects is
different. They are so large, these several kilometer size
rocks are so large that they actually go down to the bottom,
all the way through the water, and punch a hole into the ocean
floor, and put all of that mud up into the stratosphere,
creating nuclear winter. It is a very different scenario. So,
for these smaller objects, it is a different and a somewhat
scarier scenario, because there are so many more of them. As
somebody pointed out, there is a factor of 100 more of these
things. And there is a problem with, you know, I have a problem
with probability. You know, you can say----
Mr. Feeney. Probably.
Dr. Tyson. Well, most likely. You can say that, well,
actually, maybe we should spend $1 million on something else,
because actually, the probability of this is rather low. But if
a 100 meter object could be on its way towards Earth right now,
and hit next week, for example, even though its probability,
the probability per unit time is very low. So, I think what we
need to do is to get on with these discovery surveys, which
find virtually all of the Earth-threatening asteroids, and find
their orbits, and then it changes the whole equation.
Mr. Feeney. Thank you, Mr. Chairman. I yield back.
Chairman Udall. Thank you. I am not sure, Dr. Tyson, you
ruined my afternoon with that image, but that is a very
powerful image and very compelling reason to do the work we are
talking about here today.
The Chairman recognizes the gentleman from California, Mr.
Rohrabacher.
Mr. Rohrabacher. Let us see. It is going to create a huge
wave. I think I am the only surfer on this panel. One hand, we
got another one here. All right.
Now, let me see if I have got this right, Rusty, that the
one, the object that exploded over this, was it Tunguska?
Mr. Schweickart. Tunguska, yes, sir.
Mr. Rohrabacher. Okay, was only the equivalent of a five
megaton? And the one----
Mr. Schweickart. Yes, sir. The most recent analytic work at
Los Alamos indicates it was about five megatons, about 45
meters.
Mr. Rohrabacher. And you are saying the ones we are looking
for are 140, would be the equivalent of 140 megatons, if it is
a 140 meter object. Is that right?
Mr. Schweickart. Approximately, yes, sir.
NEO Survey Objectives
Mr. Rohrabacher. So, you are talking about something that
would be 100 times more powerful than the one at Tunguska, is
what we are just trying to observe?
Mr. Schweickart. Yes, sir. That is correct. But let me
emphasize, sir, that the 140 meter search goal is, in fact, at
this time, the correct goal. Because, among other things, it is
extremely difficult to find things as you get smaller and
smaller. So 140 meters is a good goal, and in the process of
finding 90 percent of the 140 meter objects, we are also going
to find something on the order of 40 to 50 percent of the
objects down to 45 or 50 meters. So, we will not have, let me
say, a complete survey of those things which can do serious
damage on the ground, but we will learn a great deal about them
in the process of meeting this appropriate goal.
Mr. Rohrabacher. Right. From what you said, we are talking
about a huge potential destructive power. I mean, we are
talking about something beyond, I think, the imagination of any
of us here. What is the estimate of the number of undiscovered
asteroids that are of 140 meter range? How many have we yet to
discover? What are we talking about?
Mr. Schweickart. Don has probably got the best number,
but----
Dr. Yeomans. The 140 meter sized objects, we think there is
approximately 20,000 that are in the category of potentially
hazardous asteroids, and we have discovered less than four
percent of them.
Mr. Rohrabacher. So, there are 20,000, and we have actually
charted only about four percent of them? And it is 100 times
stronger than what flattened all of that territory up in
Russia?
Dr. Yeomans. It is like your statement, sir, ignorance is
bliss.
Mr. Rohrabacher. Yes, sir. Dr. Tyson.
Dr. Tyson. Just to add a data point. It is hard to
comprehend the destructive force of something like this, but a
300 meter asteroid, of which there are many, has the potential
to wipe out entire countries.
Mr. Rohrabacher. Well, obviously, there is a need for us to
be prepared to try to do what we could. If we could mitigate
that, we are talking about minimal expense, as compared to
what, the cost of actually having to absorb this type of
damage.
Planetary Defense Responsibilities
I would like to talk a little bit about that. Who should be
in charge? NASA is obviously involved with the efforts of
identifying this, and with the Jet Propulsion Laboratory, and
the assets that we are talking about. And NASA has been tasked
with this. Once we determine that there is a threat, Rusty is
suggesting that this is no longer a science issue. This is a
defense issue at that point. Should the Defense Department be
the ones who are then tasked with immediately taking over
responsibility? Do you have some ideas as to who should, then,
be the entity that is responsible for planetary defense? To
start with NASA, and then work our way down.
Dr. Pace. Thank you, sir. Well, as you probably know, there
is no one who is tasked specifically with that responsibility
right now. That is not a settled policy question. And I think
it is also fair to say that it would be something that would
take the resources and capabilities of multiple federal
agencies, if they were to be so tasked.
So, as Mr. Schweickart says about, these things are safety
issues versus sort of science issues, I would also submit this
is really a policy question as to where you want to assign
policy responsibilities for this, and what sort of importance
you want to give to it.
I think NASA's traditional role certainly is stronger in
the science and in the technology side of it, and therefore,
you know, it wouldn't be obvious that we would be the lead
agency for something like that, although if so directed, we
would certainly participate with other federal agencies who
were assigned.
Mr. Rohrabacher. Does anyone else have a thought on that?
Dr. Tyson. Mr. Rohrabacher, I would like to comment just a
bit, and I thank you very much for highlighting that issue,
because as I said, I believe this is really the most important
single issue before the world, frankly. It is not only the
United States, the Congress, and the Administration, but every,
this is a global issue. It is not a national issue.
Mr. Rohrabacher. Well, the first part of it is, are we
going to do what is necessary to identify the threat, and then,
the issue is who is going to do it?
Dr. Tyson. Right. And I think that the identification of
the threat has been relatively well dealt with. NASA has
explicit responsibility, in terms of discovering. The
identification of a threat comes right up to the point of
warning, and issuing warnings has not been assigned to anyone,
including NASA. So, that assignment has not been made.
And I think that, in fact, it probably was avoided at the
time, several years ago, because of this fundamental policy
question. Who is to make these large international policy
decisions, and I think that it is important that we look at the
logic of it, and who should be involved? NASA clearly is the
world's premier agency for developing and testing and
demonstrating space capability, and space capability is the
sine qua non of protecting the Earth against asteroid impacts.
However, the policy issues are a larger issue, which
involves cooperation between nations, agreements, tradeoffs of
risk and many, many other things. And so, the policy issue is
somewhat separable. Now, the Department of Homeland Security,
it would seem, on plain reading of the language, might be one
logical agency. The Department of Defense is clearly another
potential agency, and NASA itself has many international
responsibilities, for example, the International Space Station,
in which it makes policy decisions on behalf of the Nation. So,
to me, those three agencies are the prime candidates.
I, frankly, because of the need for international
cooperation and worldwide public confidence, would argue
against the Department of Defense being the principal agency.
The Department of Homeland Security certainly has a large
responsibility, but it seems to me that the Congress needs to
hold hearings to allow many, many people and perspectives and
issues to be openly aired in this regard. But it is extremely
important, because these international decisions are being
forced on us by the very search programs that we have been
talking about.
In the next 10 to 15 years, we are going to discover
hundreds of thousands of asteroids, and some of them, probably
in the hundreds, will look as though they are headed for an
impact. And somebody is going to have to make a decision,
within the next 15 years, of do we or do we not take protective
action?
Now, those decisions are going to involve tradeoffs between
nations and national policy issues, and it seems to me we need
to get on with this critical decision, so that we are in a
place to contribute.
Mr. Rohrabacher. Thank you very much, and Mr. Chairman, I
appreciate your holding this hearing, and I would like to
personally thank the witnesses. This has been very
illuminating, if not hair-raising. Thank you.
Chairman Udall. I thank the gentleman from California, and
I know within his political party and his circles, there is a
lot of debate about the prefix NEO, and to which words you then
apply it, but since Mr. Rohrabacher may be more of a neo-
internationalist now than he perhaps has been in the past, when
it comes to supporting a worldwide effort to make sure that the
planet doesn't suffer from one of these impacts.
Goldstone Antenna Upgrades
We are approaching another vote. I would like to ask a
couple of additional questions of the panel, and then, we will,
my questions will conclude the hearing. And I wanted to start
with Dr. Green. NASA is planning to replace the existing deep
space antennas at Goldstone with an upgraded system. Will NASA
maintain the current planetary radar capability at Goldstone as
part of the upgrade, and if not, why not?
Dr. Green. Indeed, the organization in NASA that manages
the Deep Space Network is the Space Operations Mission
Directorate. They have the responsibility for developing an
evolutionary plan for that system. It is used for
communications, in addition to the science that we utilize that
system for, and our radar requirements have been given to that
organization as they develop their plan. In the near future, we
anticipate seeing those requirements met in the newly
redesigned Deep Space Network.
Chairman Udall. Dr. Yeomans, how important is it?
Dr. Yeomans. How important is it to maintain the radar with
the DSN? I think it is very important. As was mentioned by a
number of folks on the panel here, the Goldstone radar and the
Arecibo radar are the only two we have, in terms of planetary
observations, and they are very complementary. Goldstone covers
a large area of sky. It can actually track the objects, whereas
Arecibo is fixed, and can track 20 degrees on either side of
directly overhead, so very often, an object will come into the
Arecibo window, pass out of it, and pass into the Goldstone
window and vice versa. So, it is important to keep both of
these facilities robust.
Future Steps in NEO Detection and Deflection
Chairman Udall. I would like to follow another line of
questioning, but start with Dr. Yeomans again, and just give
the panel a heads-up, and invite each one of you to comment
before we conclude the hearing. And the focus will be where do
we go from here? NASA submitted its report to Congress on
options for the expanded NEO program for approaches to deflect
NEOs.
What do you believe, Dr. Yeomans, the relative priority for
resources should be between NEO detection, tracking,
cataloging, characterizing, and development of deflection
approaches? In other words, what is most important to do next,
and what specifically should NASA do next? Easy question, I
know.
Dr. Yeomans. Well, I am a bit biased. We have to find them
early was my first, second, and third priority. And I do think
finding them is the first priority. Obviously, we can't
mitigate if we don't find them. We can't characterize if we
don't find them.
Having said that, we do need to characterize, because there
is an enormous diversity amongst Near-Earth asteroids. They
range all the way from a fluffy, wimpy, ex-cometary fluff ball
to a rubble pile, to a slab of solid rock, to a slab of solid
iron. So, you wouldn't mitigate each of those objects with the
same technique, perhaps. So, we do need to characterize these
objects, and we do need to at least study techniques for
mitigation. There is computer simulation work that needs to be
done to understand how an impact or an explosion would interact
with a rubble pile, with a slab of iron. So, we do need to
understand the mitigation and the characterization, but I think
discovery is still the most important.
Orbital Determination
Chairman Udall. Dr. Campbell, Dr. Tyson, Mr. Schweickart in
turn, would you each like to comment on the question of
priorities?
Dr. Campbell. I think there is little doubt that discovery
is the most important thing. If you haven't found them, you
certainly can't track them and characterize them. It is clear,
though, that there is little point in just making a catalog of
a lot of objects in the sky, with poorly defined orbits. And
therefore, I think that the two, orbit determination and
discovery have to go hand-in-hand. And it seems to me the most
important thing to do is to cull the number of objects that you
have found as quickly as possible, so that you can actually
concentrate on the ones that actually do pose a threat. We have
already got thousands of potential objects here, we are going
to be finding tens of thousands. We need to know which ones of
these are a potential threat to Earth, and for the very
smallest objects, we have potentially very little time to do
that, in terms of the fact that they will be rather close to
the Earth in orbits, and pass rather quickly, and not be
detectable in the future.
Chairman Udall. Dr. Tyson.
Dr. Tyson. Thank you, Chairman. Discovery involves
obtaining orbits. You can find a rock that is in the sky and
then lose it, and it is of no use, and that doesn't count as a
discovery. So, with LSST, one sees each one of these asteroids
100 to 200 times, even more. So, it is possible to derive a
pretty good orbit for those, and distinguish them from the
background.
So, that facility would get orbits for the Earth-
threatening, so-called potentially hazardous asteroids. What is
not widely known is that we observe the whole sky every several
nights. We just repeat the whole sky every several nights,
often in a different color band. So, we have a huge amount of
color information in a six color system on each one of these
Earth-threatening asteroids, and that, it turns out, as you
might imagine, tells you a fair amount of information about the
character of its surface and what it is made out of. So, we
will gain some knowledge for characterization as well from this
data.
But I think we need, actually, the bottom line, I think, is
we need to start this process of discovery. I agree with Don
that one has to actually discover these things and get their
orbits first, and that involves a multi-agency cooperation in
these new facilities. I am thinking of the Department of Energy
Office of Science, NASA, and the National Science Foundation.
Chairman Udall. Mr. Schweickart.
More on Detection and Deflection
Mr. Schweickart. Yes, Mr. Chairman. Thank you.
I would like to suggest that your, the way in which you
have posed the question is somewhat purist, I guess I would use
the word. Like most things in life, we are confronted with
things which are, they can be posited as either/or, but the
reality is that they are usually not, and I would suggest that
this is the case here.
There is absolutely no question that finding them is
absolutely the highest priority. Finding them early is very
critical. At the same time, the most important thing to keep in
mind is that we are finding them in order to protect the Earth
from impacts, and so, I would also suggest that at the same
time that we are spending money on finding them, we can also
direct JPL or NASA to put one or two people to thinking about
and working through and understanding the ultimate issue of
protecting the Earth, mitigating ones that would be coming at
us. And right now, unfortunately, that additional task of
thinking through the deflection issue is not there.
And all that takes is a clever person, which JPL has lots
of, frankly, thinking about it. But right now, no one is
assigned to that, because their job is to find them. And so, I
suggest that we do both. And I don't think it's either/or.
Chairman Udall. Knowing your history, and also having
viewed with Mr. Feeney the movie Armageddon, I am sure you
would be willing to volunteer for one of those missions,
because the spirit is still willing.
Thank you.
Mr. Schweickart. Well, luckily, we don't have to have a
human mission to one of these things.
Chairman Udall. Thank you again for your testimony, for
appearing here today. I want to turn to the representatives of
NASA and Dr. Green and Dr. Pace. Would you care to comment as
well, and well, you will have the final word today.
Dr. Pace. Yes, I just wanted to address a point that any of
these sort of mitigation techniques that one would want to use,
of course, depends on the situation. As I said, many, many of
these different objects have different technical
characteristics, and different mitigation techniques may be
appropriate.
And so, in that regard, I just, I wanted to go back and
clarify one point, that our report, I hope, did not give the
impression that we had a preference for use of nuclear
explosives. So, those are simply one of the items in the
toolkit, and people can disagree over whether it is appropriate
or not, depending on the situation. I just want to stress that
we did not want to express a preference.
The second thing is that we are trying to not only find
objects, and obviously, more can be done, but that
characterizing these objects is really also part of our science
program. The missions, such as Dawn, that are being done, our
international cooperation, what we learn about these objects
with our science missions, we think is also directly helpful,
should and if a mitigation mission ever be necessary.
And then, finally, I wanted to agree with Dr. Tyson's point
about the importance of turning a probabilistic threat into a
deterministic one. That is, with a survey effort, and one can
go faster or slower, depending on available resources, that one
can get to a point where you know where these things are, and
whether or not you have thousands of threats, hundreds of
threats, one, or none. And that is also achievable. Progress is
being made in ground-based optical telescopes at an amazing
rate. LSST is one particularly notable one. And that if we
simply proceed on the path we are on, we will, in fact, get
good survey information. We will get good characterization of
objects with our existing science program, and make progress,
you know, toward the legislative goal.
Thank you.
Chairman Udall. Dr. Green, did you have anything else to
add?
Importance of NEO Characterization
Dr. Green. I certainly would echo a number of things that
have been stated here. We know enough about the asteroids to
know that not all are created equal. They are very
heterogeneous, not only in composition in size, but also in
their structure. Some are rubble piles. Some are, indeed, irons
and quite different in shapes. And therefore, that
characterization aspects, which is important from the
scientific point of view, understanding their origin and their
evolution, is extremely important for any, the next step, which
would be consideration of mitigation, provided we understand
that they are potentially hazardous objects, and when they
might pose an important threat to us.
So, I believe we have started that first baby step. We are
moving out with existing assets. And we are excited about the
near-term future, with new assets coming online. We will
definitely step up our effort, in terms of utilizing those, and
I believe, as we learn more about them, both from in situ
observations, but continuing to utilize our radar facilities,
not only in NASA, but we sincerely hope that NSF will continue
to support the Arecibo radar, that that will enable us to then
take more of those steps, which will lead up to some sort of
mitigation information necessary to avoid these hazards in the
future.
Chairman Udall. Thank you, Dr. Green. I think I speak on
behalf of Congressman Feeney, the Ranking Member, in offering
my thanks to all of you for taking your valuable time today to
appear before us, both panels, including Congressman Fortuno,
have been very, very useful to the Committee.
I would like to make note if there is no objection, the
record will remain open for additional statements from the
Members, for answers to any followup questions the Subcommittee
may ask of you all on the panel. Without objection, so ordered.
The hearing is now adjourned.
[Whereupon, at 12:50 p.m., the Subcommittee was adjourned.]
Appendix 1:
----------
Answers to Post-Hearing Questions
Responses by James L. Green, Director, Planetary Science Division,
Science Mission Directorate, National Aeronautics and Space
Administration (NASA)
Questions submitted by Chairman Mark Udall
Q1. NASA submitted a 2007 report to Congress on NEO search and
deflection options, but the report doesn't provide a recommended
option, as required in the 2005 NASA Authorization Act. What approach
does NASA recommend that complies with the legislated mandate and what
steps have NASA taken to begin implementing any of the options
identified in the report?
A1. NASA will look for opportunities using potential dual-use
telescopes and spacecraft--and partner with other agencies as
feasible--to attempt to achieve the Congressional goal outlined in
Section 321 of the NASA Authorization Act of 2005 (P.L. 109-155). The
Agency has already begun work with Pan-STARRS to ensure its capability
for use in the NEO survey effort, and is beginning work to assess what
might be done with the Wide-field Infrared Survey Explorer (WISE), and
to upgrade the capabilities of the Minor Planet Center (MPC).
Q1a. NASA's report to Congress mentions search options that would rely
on planned ground-based telescopes that have been proposed for
development under the auspices of other agencies. What role, if any,
should NASA play in supporting the NEO-related operations of those
telescopes? What alternatives exist if those assets are not funded and
developed?
A1a. Maximizing use of the Pan-STARRS and eventually the LSST, if they
are developed by other agencies, may be a very cost-effective way for
NASA (though perhaps not the Federal Government as a whole) to meet the
90 percent goal, though not on the timeline outlined in Section 321 of
the NASA Authorization Act of 2005 (P.L. 109-155). At the present time
NASA does not have a commitment from the sponsoring agencies that the
assets will be developed. However, the Agency has begun discussions
with the University of Hawaii regarding use of the Pan-STARRS prototype
telescope and will continue to monitor its further development, as well
as the possible eventual support of LSST by the National Science
Foundation, in order to insert at the appropriate time capabilities and
commitments for their use in the NEO survey effort. In fact, LSST (or a
generic equivalent) is expected to be reprioritized by the National
Academies in its upcoming astronomy and astrophysics decadal survey
process, and this report will play a significant role in future
prospects for LSST within the Foundation's broader set of priorities.
Q2. Dr. Yeomans testified that optical observations alone are often
not ``accurate enough to immediately rule out a future Earth impact''
once a potentially hazardous asteroid is detected. Dr. Campbell
testified that the Goldstone antenna alone would be unlikely to fill
the void if Arecibo were to be shut down. What specifically are NASA's
plans for calculating the risk of potentially hazardous objects in a
timely fashion, especially given the expected increase in NEOs detected
from an expanded survey with Pan-STARRS or LSST? Do those plans involve
either Arecibo or Goldstone?
A2. The Spaceguard System, which was setup and supported by NASA, will
continue to process NEO observations for impact prediction analysis by
the Agency's NEO Program Office in a near real-time manner through the
established procedures with the Minor Planet Center of obtaining timely
follow-up optical observations and reviewing archived data and
photographic records for ``pre-discovery observations.'' As the
proposed expanded survey efforts (potentially with assets like Pan-
STARRS and LSST) come on line to detect significantly fainter (i.e.,
smaller) NEOs, these types of instruments will have the coverage
capacity to essentially be responsible for obtaining their own optical
follow-up observations.
Although the radar capabilities of both Arecibo and Goldstone are
able to provide precise refinement of NEO orbits, their observations
are only available on a limited subset of NEOs--those that happen to be
passing close enough to Earth to be within their range. NASA will use
these observations when available, but by far the majority of NEOs
orbits must still be determined via optical observations. Once a NEO
has been initially detected and its approximate position determined, a
whole host of other optical assets can be brought to bear on that NEO's
location to determine the orbit as precisely as our orbit models allow.
Over time periods significantly smaller than the average impact rate (a
few years versus hundreds of years between significant impacts) a
collection of optical observations will approach the accuracy that can
be obtained via radar observations.
Q3. What are the requirements for data management to support the
expanded Survey? How big a job is it likely to be?
A3. Data throughput required as an expanded Survey reaches peak
discovery productivity is estimated to reach as much as 100 times the
current discovery and observation rates, with the associated needs for
expanded data archives. The current Minor Planet Center computer
systems are at least two generations obsolete, and will therefore need
to be upgraded. However, the anticipated capabilities needed are well
within the capabilities of modern desktop computer network systems.
Q3a. Your testimony indicates that NASA has started to evaluate the
needs of the Minor Planet Center to accommodate the increase in
detection that will result from an expanded survey. What, in specific
terms, are NASA's plans for the Minor Planet Center and any changes
that may be required to support the expanded survey? What, if any,
costs are associated with those plans? How do those plans relate to
options on data management presented in the report to Congress?
A3a. In 2008, NASA's Science Mission Directorate plans to solicit for
proposals from the small Solar System bodies community for management
and operations of the Minor Planet Center--first to modernize the
current computer systems and operations, and then to accommodate
expanded data throughput for an anticipated expansion of the Survey
effort. Costs will be determined based on the proposals received, but
NASA does not anticipate costs beyond $1.0 million per year initially.
Later options may look at back-up facility needs. This approach most
closely relates to the ``Scale Existing Data Management Systems''
alternative outlined in the NASA report on NEOs submitted to Congress
in March 2007.
Q3b. Does NASA have any plans to compete the data management task for
the expanded search?
A3b. The Minor Planet Center solicitation will be a full and open
competition.
Q4. The European Space Agency (ESA) has conducted a study for a
mission (Don Quixote) that would test NEO deflection technologies. Has
ESA expressed any interest in international cooperation on a mission,
if it were to go forward? If so, has NASA explored the possibility of
contributing?
A4. The Don Quixote mission concept has been discussed at bilateral
meetings with ESA as a potential area for cooperation. However, NASA
understands that further development of this mission has been placed on
hold by ESA.
Q4a. Your testimony noted that ``ESA has been studying . . . another
mission called Marco Polo, that does have a much better chance now of
making it through their budgetary process, that will also add
information that is important for us.'' Could you please describe the
potential Marco Polo mission and how it would benefit NASA's NEO search
and/or the characterization of NEO's? What is the status of any
discussions between NASA and ESA on collaboration or access to data
from this potential mission?
A4a. Marco Polo is a proposed near-Earth object sample return mission
to a primitive asteroid whose objective is to return samples that are
otherwise not available among known meteorites. Primitive bodies are
leftover building blocks from the earliest era of Solar System
formation and may have contributed water and organics to Earth, thereby
providing a foundation for life. Primitive meteorites are among the
least frequently sampled by falling to Earth and all samples received
are biased by their ability to survive atmospheric passage. Direct
investigation of both the fresh regolith and fresh lithospheric
fragments is also impossible by any means other than sample return.
Marco Polo will conduct a broad in situ analysis of the target and the
geologic context for the samples prior to their acquisition. Sample
return enables the power of the Earth's laboratories to identify major
chronological events in solar system history, to search for pre-solar
material yet unknown in meteorite samples, and to characterize in depth
the nature of organic compounds that may be present. Thus, Marco Polo
will provide extensive information for the characterization of NEOs. A
participating scientist proposal has been submitted by a team of U.S.
scientists to the ESA Cosmic Vision solicitation for this mission and
we are in the preliminary stages of the process to award to this
proposal.
Q4b. You also testified that ``The Canadians will be launching a
spacecraft called NEOSSat. We have been discussing about how it can be
utilized and making the data more available.'' Could you please
describe the NEOSSat mission and how the data would benefit NASA's NEO
search and/or characterization effort? What is the status of any
discussions between NASA and the Canadian Space Agency on collaboration
or access to data from this potential mission?
A4b. The Canadian Space Agency (CSA) Near Earth Object Surveillance
Satellite (NEOSSat) is a small satellite with a 0.15 meter aperture
visible sensor which we understand will be launched sometime in 2009.
The small aperture of the sensor means it will have little advantage
over current ground based capabilities to detect and track NEOs.
However, the continuous access offered by a space-based asset may
provide some advantage to augment our capabilities, perhaps in the area
of obtaining follow-up observations. NASA is in preliminary discussions
with the CSA about collaboration or access to the data.
Q5. Dr. Tyson testified that the estimated the cost for a 12-year long
survey would be $125 million. You testified that ``The LSST activity,
of course, is one that needs to be resolved, in terms of whether they
will have sufficient funding, and be able to put together the
capability before we can begin to figure out how to work with them and
leverage that system.'' Is NASA ruling-out partial support for
development, even though such support could help ensure the
availability of a system that could complete the expanded Survey at a
considerably lower estimated cost than the options provided in NASA's
report to Congress?
A5. Maximizing use of the proposed LSST is probably part of the most
cost-effective way for NASA to meet the 90 percent goal, though not on
the timeline specified in the NASA Authorization Act of 2005 (P.L. 109-
155). LSST (or a generic equivalent) is expected to be reprioritized by
the National Academies in its upcoming astronomy and astrophysics
decadal survey process, and this report will play a significant role in
future prospects for LSST within the Foundation's broader set of
priorities. NASA will continue to monitor its further development in
order to insert at the appropriate time capabilities and commitments
for its use in the NEO survey effort.
Q6. NASA Ames recently hosted a workshop on the potential of low-cost
spacecraft to characterize NEOs. What, if any, plans does NASA have to
pursue such missions?
A6. NASA held a workshop on low-cost missions to NEOs at Ames Research
Center on October 20-21, 2007. The workshop agenda blended three major
themes: (1) the importance of characterizing small NEOs and the kinds
of science measurements that need to be made; (2) how to get to the
targets (i.e., target populations, orbital dynamics, direct vs.
gravity-assist trajectories, opportunities for secondary payloads and
missions of opportunity); and (3) options for low-cost missions (i.e.,
small spacecraft, instruments, proximity operations, propulsion,
landers, and impactors).
A primary conclusion from the workshop is that low-cost missions to
NEOs can play a role in exploring and characterizing these objects.
Since a major objective is to explore the diversity of the NEO
population and characterize their physical properties, launching
multiple small missions could be cost-effective if the technology can
be sufficiently matured. NASA already plans numerous ``mission of
opportunity'' solicitations for which such proposals could be
submitted.
Questions submitted by Representative Tom Feeney
Q1. NASA's Near-Earth Object (NEO) report, delivered this March,
provides several options for meeting the goal of achieving 90 percent
detection, tracking and characterization of Potentially Hazardous
Objects (PHOs), and the report establishes a clear relationship between
resources invested and the time needed to achieve 90 percent coverage.
In essence, the report shows that for an additional investment of
approximately $536 million, we could buy-down a decade of time to
complete the survey. In your view, is that additional investment
necessary? Does the threat posed by PHOs compel faster completion of
the survey?
A1. NASA's analysis shows that not completing the NEO survey down to
140 meters until the 2025-2030 timeframe does not statistically carry a
level of risk that requires costly actions.
Q2. What are the most difficult types of NEOs to detect? Is there, for
instance, a portion of the sky that won't be covered by ground-based
facilities? Are there certain types of orbits that make it difficult to
detect and track asteroids and comets?
A2. Small NEOs composed of dark, carbonaceous materials are difficult
to detect because they are intrinsically faint. NEOs of any size and
composition on very Earth-like orbits can be potentially difficult to
detect because they may spend a considerable number of years far from
Earth on the other side of the Sun. Such objects may spend many years
being effectively unobservable to ground- or Earth-based telescopes
because of their apparent faintness or apparent proximity to the Sun.
In general, the present bias toward NEO survey programs being
located in the northern hemisphere does not significantly affect
progress in completing the Spaceguard Survey for kilometer and larger
NEOs; objects not detected during a southern-hemisphere-visible close
approach will most likely be detected on a subsequent northern-
hemisphere close pass. The present baseline survey plan for the Large
Synoptic Survey Telescope (LSST) as developed by the project's
proponents, which will, if funded, be based in the southern hemisphere
and be a significant contributor to a follow-on survey for 140m and
larger NEOs, conversely leaves some time gap in northern hemisphere NEO
detection capabilities. The LSST project proponents are, however,
actively exploring options for modifications to their baseline
observing plan to include a portion of the northern ecliptic (the
central plane of the solar system--where most NEOs spend most of their
time) in order to increase their detection rate of NEOs.
In any case, all surveys able to find 90 percent of potentially
hazardous objects reduce the actuarial risk by the same amount, even if
some small percentage of the objects is more difficult to detect by a
specific system.
Q3. Once the LSST and Pan-STARRS telescopes are operating, and surveys
for PHOs that are 140 meters or larger has commenced, what is the
business and public safety case for expanding the search to detect and
track smaller PHOs--or instance, down to a size of 50 meters? What are
the cost and schedule implications?
A3. An object of about 50 meters and average density would not be
expected to survive all the way through the Earth's atmosphere and
strike the surface, but this depends on the object's composition and
structure. It could be expected to cause an explosion a few kilometers
above the Earth's surface and may therefore cause some blast damage at
ground level.
The number of objects and frequency of impact increases as
threshold size decreases, roughly based on the following figure, which
is also Figure 2 in the report on NEO's NASA submitted to Congress in
March 2007.
Therefore, it is estimated that, while there may be about 20,000
Potentially Hazardous Object (PHO)s 140 meters and larger, there are
estimated to be about 100,000 PHOs 50 meters and larger and impacts by
these smaller objects will therefore be more frequent.
Simulations suggest that a next generation search for potentially
hazardous objects (PHOs) down to 140 meters that includes only Pan-
STARRS (assumed 2010 start) and LSST (assumed 2014 start) would
discover roughly 42 percent of the PHOs larger than 50 meters by the
end of 2020 and 59 percent by the end of 2029. Using a one-meter
infrared telescope in a Venus-like orbit (assumed 2014 operations
start) in addition to the ground-based Pan-STARRS and LSST surveys, the
discovered population of 50 meters and larger sized objects would be
complete to the level of 78 percent at the end of 2020 and 92 percent
complete by the end of 2029. This assumed timeline would require that
these systems operate for over a decade, and therefore might require
multiple advanced spacecraft to be built (depending on design life),
and would also require an even more capable operational data management
infrastructure.
Although no estimated costs for such a program are available, it is
likely that such a search would require significantly more resources
than necessary for the Congressional goal of 90 percent of 140 meters
objects outlined in the NASA Authorization Act of 2005 (P.L. 109-155).
The completion of the Congressional goal alone would retire 99 percent
of the actuarial risk from PHOs of all sizes. Once significant progress
has been made toward the Congressional goal, more consideration may be
given to finding and tracking all potentially hazardous objects.
Q4. During the hearing several witnesses mentioned the Air Force's
funding of the Pan-STARRS telescope facility in Hawaii as a possible
new ground observatory that would be very adept at detecting NEOs. What
is the status of Pan-STARRS and the likelihood that all four telescopes
will be built? Would the Air Force be willing to make available a
portion of the telescope's time to NEO surveys if less than four
telescopes are built?
A4. NASA understands that the Pan-STARRS Project Office acts as the Air
Force's agent for discussion of capabilities related to NEO detection
and survey, so all discussions have been directly with that project
office at the University of Hawaii. Pan-STARRS currently is in check-
out of its first prototype telescope at the Air Force facility on
Haleakala, Maui. NASA cannot speculate on the future funding that will
be made available by the Air Force to this project. However, the Pan-
STARRS Project Office has already begun discussions with our NEO
Program on how the single prototype telescope could be used to complete
our currently ongoing one kilometer NEO survey, so it is likely they
will work with the survey effort at whatever level of capability they
are able to achieve.
Q5. How adaptable are current and proposed space-based infrared
satellites to the role of NEO detection, tracking, and
characterization? For instance, can Spitzer be used, even if its
cryogenic coolant is depleted? And what about WISE (Wide-field Infrared
Survey Explorer), due to be launched in 2009?
A5. The majority of existing astronomical telescopes are designed with
limited fields of view so they can focus on a specific object of
interest. The fewer number of telescopes designed for survey work has
relatively large fields of view (FOV) so that they can cover more sky
more quickly. For instance, the Spitzer telescope's largest FOV is only
five arc minutes by five arc minutes, or less than 10 percent of the
area size that would be useful for a survey effort, usually considered
to be at least one by one degree FOV. In ``back of the envelope''
terms, this means it would take Spitzer more than ten times longer to
conduct the survey effort than a telescope designed for it, even if it
were dedicated to the effort full-time. This of course is not possible.
Of greater potential is the Wide-field Infrared Survey Explorer
(WISE) since, as its name implies, it has a wide FOV instrument.
Currently being developed for a late 2009 launch for a six month
astrophysics mission to map the infrared sky, the WISE instrument is
also capable of detecting many asteroids, of which a portion will be
NEOs. NASA is evaluating what it will take to make its operations
useful to the NEO survey effort. However, the limitations of WISE
relative to what it takes to do the NEO survey will limit the results
NASA can get from it. Those limitations are its static pointing
capability, because it only points along the plane of its orbit so a
NEO must pass through that plane at some time to be detected by WISE,
and its limited lifetime of only six months--although NASA is exploring
what it would take to double that lifetime. If a spacecraft with the
capability of WISE could operate for 10 years, it could go a long way
towards completing the survey effort, but in only six months it may
detect only about 400 previously unknown NEOs.
The NASA study looked at all known spacecraft, including those
operated and planned by the Air Force, and although several of these
projects provided potential technology that could be used in a NEO
survey spacecraft, no others had the right combination of capability
and operational application that would be useful to the effort.
Q6. The NEO Survey Analysis indicates that a space-based observatory
has certain advantages over ground-based telescopes. How seriously is
NASA giving consideration to building and launching a space-based
observatory?
A6. The space-based alternatives have both benefits and risks when
compared with ground-based assets. However, both types of systems can
meet the Congressional goal of surveying 90 percent of 140 meters
objects outlined in the NASA Authorization Act of 2005 (P.L. 109-155).
If a system is built, the benefits and risks would be weighed against
cost differences to make a selection. NASA does not have plans for
building either a ground or space-based asset for NEO detection within
its budgeted program. However, there are a few programmed space flight
opportunities for competitive selection to which a capability might be
proposed by the external community.
Q7. One deflection solution, suggested by NASA, is to detonate a
nuclear device in the vicinity of a PHO. What are the advantages and
disadvantages of using this approach? What circumstances would argue
against using a nuclear device in lieu of alternative approaches?
A7. The report on NEOs NASA submitted to the Congress in March 2007 did
not recommend any one specific deflection solution--different scenarios
might require completely different combinations of systems and
solutions. However, the alternatives analysis for this report found:
Deflection systems using nuclear explosives carry the
highest deflection capability per kg of payload launched of the
alternatives studied, therefore significantly reducing launch
costs and increasing launch opportunities.
Deflection systems using nuclear explosives were
evaluated to be applicable to the widest range of threats
(size, composition, shape, spin rate, etc.), although other
alternatives may have advantages in certain scenarios.
Nuclear explosives were evaluated to be among the
most reliable and repeatable of the deflection techniques
evaluated, with the highest level of technology readiness
relative to alternatives.
Impulsive methods, including nuclear explosives and
kinetic impactors, provide their deflection instantaneously.
This improves performance in ``quick response'' scenarios and
permits multiple successive attempts that are likely to be
necessary to achieve desired levels of deflection campaign
reliability.
Deflection systems using nuclear explosives are
likely to be among the lowest cost due to significantly lower
launch costs, lower payload development costs, and lower
operations costs than slow push methods.
Deflection systems using nuclear explosives carry
unique operations and launch safety risks, all of which must be
evaluated in the event a credible threat to the Earth is
actually detected.
Possible deflection scenarios cover a wide range of
threat characteristics including size, mass, composition, spin
rate, shape, cohesion, and number of gravitationally bound
objects. As the NASA study indicated, the alternatives studied
provide a ``tool kit'' of options to a decision-maker when an
actual threat becomes apparent.
Nuclear deflection is possibly the most effective option when cost,
schedule, technology readiness, operational issues, and the need for
characterization are considered, but it does have unique political,
policy, and safety considerations. A series of one or more standoff
nuclear devices may be the only option as the mass of the threat grows,
but there are some instances (e.g., when the risk of fragmentation is
high) where they may not be the primary selection.
To achieve the level of reliability likely to be required to
mitigate a potential threat, it is likely that multiple deflection
techniques would need to be pursued as part of a deflection campaign
such that no technology or system is a single point of failure. The use
of nuclear explosives is evaluated to be very effective for many threat
scenarios, and it is one of many options in the tool kit of defection
alternatives.
Questions submitted by Representative Dana Rohrabacher
Q1. The need for a comprehensive potentially hazardous Near-Earth
Objects (NEO) program seems to require expertise of several agencies.
How do you suggest coordination be handled?
A1. At present, no department or agency of the United States is
assigned the responsibility for a NEO contingency notification plan or
the responsibility to mitigate threats posed by potentially hazardous
near Earth asteroids and comets. As with other major natural disasters,
a coordinated approach involving multiple federal agencies would
clearly be required. NASA has not developed a position on how
responsibilities should be assigned among U.S. departments and
agencies.
Q2. Describe some of the proposed mitigation techniques and their
trade offs.
A2. The report on NEOs NASA submitted to the Congress in March 2007
examined a number of techniques for deflecting a Potentially Hazardous
Objects (PHO) that have been categorized as either ``impulsive'' or
``slow push.'' The tables below provide an overview of the impulsive
methods and the slow push techniques, where the velocity change results
from the continuous application of a small force, considered in the
report. Each of these concepts is developed further in the report.
In the impulsive category, the use of a nuclear device was found to
be the most effective means to deflect a PHO. Because of the large
amount of energy delivered, nuclear devices would require the least
amount of detailed information about the threatening object, reducing
the need for detailed characterization. While detonation of a nuclear
device on or below the surface of a threatening object was found to be
10-100 times more efficient than detonating a nuclear device above the
surface, the standoff detonation would be less likely to fragment the
target. A nuclear standoff mission could be designed knowing only the
orbit and approximate mass of the threat, and missions could be carried
out incrementally to reach the required amount of deflection.
Additional information about the object's mass and physical properties
would perhaps increase the effectiveness, but likely would not be
required to accomplish the goal.
Non-nuclear kinetic impact alternatives are the most effective non-
nuclear option, transferring 10-100 times less momentum than nuclear
options for a fixed launch mass. Impact velocities, varying from 10-50
km/s, produced a factor-of-three variation in deflection performance.
In addition, kinetic impacts are also sensitive to the porosity,
elasticity, and composition of the target and may require large
performance margins if these characteristics are not well determined.
Slow push techniques analyzed in this study included a gravity
tractor, which could alter the course of an object using the
gravitational attraction of a massive spacecraft flying in close
proximity, and a space tug, which could attach itself to a PHO and move
it using high-efficiency propulsion systems. An attached space tug has
generally 10-100 times more performance than the gravity tractor, but
it requires more detailed characterization data and more robust
guidance and control and surface attachment technologies. This
technique could be effective in instances where small increments of
velocity (less than one mm/s) could be applied to relatively small
objects (less than 200 meters in diameter) over many decades. In
general, the slow push systems were found to be at a very low
technology readiness level (with the exception of the gravity tractor,
which was medium) and would require significant development efforts.
Q3. What is your assessment of the need for a nuclear deflection
capability?
A3. There is no need for any deflection capability at this time. No
impact threat has yet been identified. If a timely detection capability
is fielded, there will most likely be significant warning time in which
to develop other parts of the system such as sufficiently capable
characterization and deflection spacecraft.
Q4. What are the weakest links in the ``system'' considering the
overall goal to protect Earth from asteroid impacts?
A4. Finding any potential threats so that their orbits can be
determined is the weakest link by far. Unless we find threats, we will
be unable to react. If we do find threats in a timely manner, there
will very likely be significant warning time in which to develop other
parts of the system such as sufficient characterization and deflection
spacecraft.
Q5. Dr. Donald Yeomans stated that the highest priority regarding NEOs
is to ``find them early, find them early, find them early.'' Yet NASA
refused to recommend a program to find them (140 meters and larger)
early as directed by law. Why? How does NASA justify this refusal?
A5. NASA recommended an approach commensurate with the resources the
Agency has been appropriated to accomplish its task.
Q6. What is your estimate on the number of undiscovered asteroids in
the 140 meter and above range? Describe the potential damage that an
asteroid in the 140 meter range could cause striking an ocean within,
say, 500 miles from a U.S. coast.
A6. The latest estimate of the total number of near-Earth asteroids
(NEAs) larger than 140 meters in diameter is at least 20,000, but could
be higher. However, the mean time between impacts of an object 140
meters in size anywhere on the Earth's surface is estimated as about
5,000 years; larger objects would be even less frequent. Objects
striking the ocean within about 500 miles of a U.S. coast would be very
infrequent, considerably longer than 100,000 years between events.
The impact of a 140-meter-size object, striking at a typical impact
speed of about 20 km/s, would deliver and explosive energy equivalent
of some 170 megatons. Estimates of the tsunami effects from asteroid
impact vary from researcher to researcher, but recent analyses, based
on studies of waves generated by underwater explosions, indicate that
the risk of impact tsunami from asteroid impacts in this size range has
previously been overstated. Assuming precisely where an ocean impact
might occur and then extrapolating potential damage from a related
tsunami event lends to analysis of a ``worst on worst'' scenario that
couples one highly improbable event to another and biases any resulting
assessment. However, the recent studies have indicated the deepwater
tsunami wave height at a point 1000 km ( 600 miles) from the impact of
a 140-meter diameter stony asteroid might be on the order of only a few
meters, but this deepwater wave height can increase dramatically when
the waves reach the shoreline because the waves slow in shallow water
and concentrate the wave energy. Based on recent assessments of tsunami
risks for various locations, estimates are that the typical run-up
factor (the ratio of the vertical height above sea level of the tsunami
at its furthest point inland to its deepwater wave height) for impact
tsunamis is only two to three, but this can vary considerably,
depending on local topography and the direction of travel of the wave.
All this suggests that one might expect a run up tsunami wave height of
up to 10 meters or so from an ocean impact of a 140-meter diameter
stony asteroid. This is roughly comparable to the measured run-ups from
the tsunami that accompanied the Sumatra earthquake of December 26,
2004.
Q7. Asteroids are more easily detected in the infrared spectrum. An
asset such as the Wide-field Infrared Survey Explorer (WISE) satellite
has an effective capability for searching for NEO's infrared output. Is
WISE being tasked for this role? What other infrared detection devices
can or will be used to detect NEOs?
A7. WISE is not currently tasked for this role, but NASA is beginning
to investigate what might be done with the WISE spacecraft that could
be useful to the NEO survey effort. However, because of the limited
duration of the WISE mission, its usefulness to the survey effort will
be limited.
NASA continues to look at other infrared capabilities in
development or planning, but no other possibilities have yet been
identified.
Answers to Post-Hearing Questions
Responses by Scott Pace, Associate Administrator, Program Analysis and
Evaluation, National Aeronautics and Space Administration
(NASA)
Questions submitted by Chairman Mark Udall
Q1. Dr. Green's testimony notes that ``The science community may
propose a Near Earth Object (NEO) survey mission under the
competitively-selected Discovery program.'' While some space science
missions may offer the potential to contribute to NEO detection, in
addition to their scientific investigations, a NEO survey mission is
not a science mission if its purpose is primarily to detect NEOs. Does
NASA have any plans to consider developing a dedicated Discovery-class
space-based NEO survey mission to respond to the directive in the NASA
Authorization Act of 2005? If so, how would NASA carry out such a
development-what organization within NASA would have responsibility for
it?
A1. A great deal of science can be learned about the history and
evolution of the Solar System by inventory of all the pieces of mass
that exist in it, including those as small as a few 100 meter sized
objects, and understanding how they evolved to their current positions.
Exciting theories about the repositioning of the outer planets have
recently come to light based on studies of the dynamics of the small
body population.
Although a small body survey mission has not yet be selected in the
Discovery program, there have been a few missions proposed to
accomplish this type of work. There are no plans to ``dedicate'' a
Discovery mission to an NEO survey effort, but NASA solicitations will
remain open to these types of proposals. If the selection process
determines that such a mission is the best option, considering many
technical feasibility factors in addition to the science, it will also
be managed under the highly successful structure that has been
instituted by NASA's Science Mission Directorate in the Planetary
Science Division's Discovery Program.
Q2. NASA is planning to replace the existing Deep Space Network (DSN)
antennas at Goldstone with an upgraded system. Will NASA maintain the
current planetary radar capability at Goldstone as part of the upgrade?
When, in concrete terms, will NASA know the specifics of plans for the
DSN upgrade and planetary radar capability at Goldstone?
A2. NASA is in the process of evaluating the driving requirements for
capabilities provided by the DSN. These requirements, which include
planetary radar capability at Goldstone, are being worked jointly among
three Mission Directorates--Space Operations, Exploration Systems, and
Science. This collaboration will drive the decision on the needed
capabilities and will formulate the options for maintaining or
upgrading the DSN assets. NASA expects to complete these plans by May
2008.
Q3. NASA is providing funding to the Air Force's Pan-STARRS project.
Q3a. When did NASA start funding the project and how much funding is
being provided on an annual basis? Is the funding provided through a
grant, contract, or other type of agreement? How much funding does NASA
plan to provide in total? Is the funding being provided to the Air
Force or the University of Hawaii?
A3a. The NASA NEO Program started limited funding to the Pan-STARRS
project in 2007 with a partial award to a proposal submitted to the
program by the University of Hawaii, who manages the Pan-STARRS
development for the Air Force. This partial award was a one-year grant
to the University of Hawaii of $450,000. Any future funding will depend
on the success of pending and future proposals Pan-STARRS submits to
competitive opportunities of the NEO Program that NASA announces
through its annual Research Opportunities in Space and Earth Sciences.
Q3b. What, specifically, is the funding being used for and what will
be provided to NASA in return?
A3b. The funding is largely being used to adapt existing ``moving
object detection'' software from a current Spaceguard project for use
by the Pan-STARRS data processing system. This allows the option for
NASA to make use of Pan-STARRS for NEO detection in the future.
Q3c. Who made the decision to fund Pan-STARRS--and did NASA approach
the Air Force or did the Air Force approach NASA?
A3c. The decision to fund a part of the proposal submitted by the
University of Hawaii to the NEO Program was made through NASA's
Research and Analysis peer review process. The final selecting official
was Dr. James Green, Planetary Science Division Director.
Q3d. Has NASA discussed with the Air Force or University of Hawaii any
changes to the observing times and sequences of Pan-STARRS to optimize
the telescope for an expanded NEO search? If so, what is the status of
those discussions?
A3d. As Pan-STARRS nears operational capability, there have been
preliminary discussions with the project office about what observing
techniques and cadences could be used to best optimize the Pan-STARRS
operations to achieve all its requirements, to include NEO detection.
NASA has not had any direct discussions with the Air Force, as the
Agency understands that the Pan-STARRS Project Office acts as its agent
for these matters.
Q4. Dr. Green's testimony described NASA's NEO contingency
notification plan, which lays out the procedures for notification up
through the NASA Administrator if a NEO is detected with a significant
probability of impacting Earth.
Q4a. Does a notification or warning system exist beyond NASA for
informing the public and federal and State disaster and emergency
response agencies? If not, what should be done?
A4a. At present, no department or agency of the United States is
assigned the responsibility for a contingency notification plan
regarding threats posed by potentially hazardous near Earth asteroids
and comets. As with other major natural disasters, a coordinated
approach involving multiple federal agencies would clearly be required.
NASA has not developed a position on how responsibilities should be
assigned among U.S. departments and agencies.
Q4b. How will policy and legal issues involved in addressing NEOs--
e.g., when and how to warn the public and whether to use nuclear
explosives to deflect an asteroid--be handled on national and
international levels? What steps have NASA and other federal agencies
taken to date to address such issues?
A4b. At present, no department or agency of the United States is
assigned the responsibility to mitigate threats posed by potentially
hazardous near Earth asteroids and comets. As with other major natural
disasters, a coordinated approach involving multiple federal agencies
would clearly be required. NASA has not developed a position on both
the policy and legal issues addressing NEOs or how responsibilities
should be assigned among U.S. departments and agencies. NASA would
defer to the Department of State to assess the best approaches to
international cooperation on this issue.
Questions submitted by Representative Tom Feeney
Q1. Once the LSST and Pan-STARRS telescopes are operating, and surveys
for potentially hazardous objects (PHOs) that are 140 meters or larger
has commenced, what is the business and public safety case for
expanding the search to detect and track smaller PHOs--for instance,
down to a size of 50 meters? What are the cost and schedule
implications?
A1. An object of about 50 meters and average density would not be
expected to survive all the way through the Earth's atmosphere and
strike the surface, but this depends on the object's composition and
structure. It could be expected to cause an explosion a few kilometers
above the Earth's surface and may therefore cause some blast damage at
ground level.
The number of objects and frequency of impact increases as
threshold size decreases, roughly based on the following figure, which
is also Figure 2 in the report on NEO's NASA submitted to Congress in
March 2007.
Therefore, it is estimated that, while there may be about 20,000
PHOs 140 meters and larger, there are estimated to be about 100,000
PHOs 50 meters and larger and impacts by these smaller objects will
therefore be more frequent.
Simulations suggest that a next generation search for potentially
hazardous objects (PHOs) down to 140 meters that includes only Pan-
STARRS (assumed 2010 start) and LSST (assumed 2014 start) would
discover roughly 42 percent of the PHOs larger than 50 meters by the
end of 2020 and 59 percent by the end of 2029. Using a one-meter
infrared telescope in a Venus-like orbit (assumed 2014 operations
start) in addition to the ground-based Pan-STARRS and LSST surveys, the
discovered population of 50 meters and larger sized objects would be
complete to the level of 78 percent at the end of 2020 and 92 percent
complete by the end of 2029. This assumed timeline would require that
these systems operate for over a decade, and therefore might require
multiple advanced spacecraft to be built (depending on design life),
and would also require an even more capable operational data management
infrastructure.
Although no estimated costs for such a program are available, it is
likely that such a search would require significantly more resources
than necessary for the Congressional goal of 90 percent of 140 meters
objects outlined in the NASA Authorization Act of 2005 (P.L. 109-155).
The completion of the Congressional goal alone would retire 99 percent
of the actuarial risk from PHOs of all sizes. Once significant progress
has been made toward the Congressional goal, more consideration may be
given to finding and tracking all potentially hazardous objects.
Q2. How adaptable are current and proposed space-based infrared
satellites to the role of NEO detection, tracking, and
characterization? For instance, can Spitzer be used, even if its
cryogenic coolant is depleted? And what about WISE (Wide-Field Infrared
Survey Explorer), due to be launched in 2009?
A2. The majority of existing astronomical telescopes are designed with
limited fields of view so they can focus on a specific object of
interest. The fewer number of telescopes designed for survey work has
relatively large fields of view (FOV) so that they can cover more sky
more quickly. For instance, the Spitzer telescope's largest FOV is only
five arc minutes by five arc minutes, or less than 10 percent of the
area size that would be useful for a survey effort, usually considered
to be at least one by one degree FOV. In ``back of the envelope''
terms, this means it would take Spitzer more than ten times longer to
conduct the survey effort than a telescope designed for it, even if it
were dedicated to the effort full-time. This of course is not possible.
Of greater potential is the Wide-field Infrared Survey Explorer
(WISE) since, as its name implies, it has a wide FOV instrument.
Currently being developed for a late 2009 launch for a six month
astrophysics mission to map the infrared sky, the WISE instrument is
also capable of detecting many asteroids, of which a portion will be
NEOs. NASA is evaluating what it will take to make its operations
useful to the NEO survey effort. However, the limitations of WISE
relative to what it takes to do the NEO survey will limit the results
NASA can get from it. Those limitations are its static pointing
capability, because it only points along the plane of its orbit so a
NEO must pass through that plane at some time to be detected by WISE,
and its limited lifetime of only six months--although NASA is exploring
what it would take to double that lifetime. If a spacecraft with the
capability of WISE could operate for 10 years, it could go a long way
towards completing the survey effort, but in only six months it may
detect only about 400 previously unknown NEOs.
The NASA study looked at all known spacecraft, including those
operated and planned by the Air Force, and although several of these
projects provided potential technology that could be used in a NEO
survey spacecraft, no others had the right combination of capability
and operational application that would be useful to the effort.
Q3. The NEO Survey Analysis indicates that a space-based observatory
has certain advantages over ground-based telescopes. How seriously is
NASA giving consideration to building and launching a space-based
observatory?
A3. The space-based alternatives have both benefits and risks when
compared with ground-based assets. However, both types of systems can
meet the Congressional goal of surveying 90 percent of 140 meters
objects outlined in the NASA Authorization Act of 2005 (P.L. 109-155).
If a system is built, the benefits and risks would be weighed against
cost differences to make a selection. NASA does not have plans for
building either a ground or space-based asset for NEO detection within
its budgeted program. However, there are a few programmed space flight
opportunities for competitive selection to which a capability might be
proposed by the external community.
Q4. One deflection solution, suggested by NASA, is to detonate a
nuclear device in the vicinity of a PHO. What are the advantages and
disadvantages of using this approach? What circumstances would argue
against using a nuclear device in lieu of alternative approaches?
A4. The report on NEOs NASA submitted to the Congress in March 2007 did
not recommend any one specific deflection solution--different scenarios
might require completely different combinations of systems and
solutions. However, the alternatives analysis for this report found:
Deflection systems using nuclear explosives carry the
highest deflection capability per kg of payload launched of the
alternatives studied, therefore significantly reducing launch
costs and increasing launch opportunities.
Deflection systems using nuclear explosives were
evaluated to be applicable to the widest range of threats
(size, composition, shape, spin rate, etc.), although other
alternatives may have advantages in certain scenarios.
Nuclear explosives were evaluated to be among the
most reliable and repeatable of the deflection techniques
evaluated, with the highest level of technology readiness
relative to alternatives.
Impulsive methods, including nuclear explosives and
kinetic impactors, provide their deflection instantaneously.
This improves performance in ``quick response'' scenarios and
permits multiple successive attempts that are likely to be
necessary to achieve desired levels of deflection campaign
reliability.
Deflection systems using nuclear explosives are
likely to be among the lowest cost due to significantly lower
launch costs, lower payload development costs, and lower
operations costs than slow push methods.
Deflection systems using nuclear explosives carry
unique operations and launch safety risks, all of which must be
evaluated in the event a credible threat to the Earth is
actually detected.
Possible deflection scenarios cover a wide range of
threat characteristics including size, mass, composition, spin
rate, shape, cohesion, and number of gravitationally bound
objects. As the NASA study indicated, the alternatives studied
provide a ``tool kit'' of options to a decision-maker when an
actual threat becomes apparent.
Nuclear deflection is possibly the most effective option when cost,
schedule, technology readiness, operational issues, and the need for
characterization are considered, but it does have unique political,
policy, and safety considerations. A series of one or more standoff
nuclear devices may be the only option as the mass of the threat grows,
but there are some instances (e.g., when the risk of fragmentation is
high) where they may not be the primary selection.
To achieve the level of reliability likely to be required to
mitigate a potential threat, it is likely that multiple deflection
techniques would need to be pursued as part of a deflection campaign
such that no technology or system is a single point of failure. The use
of nuclear explosives is evaluated to be very effective for many threat
scenarios, and it is one of many options in the tool kit of defection
alternatives.
Questions submitted by Representative Dana Rohrabacher
Q1. The need for a comprehensive potentially hazardous Near-Earth
Objects (NEO) program seems to require expertise of several agencies.
How do you suggest coordination be handled?
A1. At present, no department or agency of the United States is
assigned the responsibility for a NEO contingency notification plan or
the responsibility to mitigate threats posed by potentially hazardous
near Earth asteroids and comets. As with other major natural disasters,
a coordinated approach involving multiple federal agencies would
clearly be required. NASA has not developed a position on how
responsibilities should be assigned among U.S. departments and
agencies.
Q2. Describe some of the proposed mitigation techniques and their
trade offs.
A2. The report on NEOs NASA submitted to the Congress in March 2007
examined a number of techniques for deflecting a PHO that have been
categorized as either ``impulsive'' or ``slow push.'' The tables below
provide an overview of the impulsive methods and the slow push
techniques, where the velocity change results from the continuous
application of a small force, considered in the report. Each of these
concepts is developed further in the report.
In the impulsive category, the use of a nuclear device was found to
be the most effective means to deflect a PHO. Because of the large
amount of energy delivered, nuclear devices would require the least
amount of detailed information about the threatening object, reducing
the need for detailed characterization. While detonation of a nuclear
device on or below the surface of a threatening object was found to be
10-100 times more efficient than detonating a nuclear device above the
surface, the standoff detonation would be less likely to fragment the
target. A nuclear standoff mission could be designed knowing only the
orbit and approximate mass of the threat, and missions could be carried
out incrementally to reach the required amount of deflection.
Additional information about the object's mass and physical properties
would perhaps increase the effectiveness, but likely would not be
required to accomplish the goal.
Non-nuclear kinetic impact alternatives are the most effective non-
nuclear option, transferring 10-100 times less momentum than nuclear
options for a fixed launch mass. Impact velocities, varying from 10-50
km/s, produced a factor-of-three variation in deflection performance.
In addition, kinetic impacts are also sensitive to the porosity,
elasticity, and composition of the target and may require large
performance margins if these characteristics are not well determined.
Slow push techniques analyzed in this study included a gravity
tractor, which could alter the course of an object using the
gravitational attraction of a massive spacecraft flying in close
proximity, and a space tug, which could attach itself to a PHO and move
it using high-efficiency propulsion systems. An attached space tug has
generally 10-100 times more performance than the gravity tractor, but
it requires more detailed characterization data and more robust
guidance and control and surface attachment technologies. This
technique could be effective in instances where small increments of
velocity (less than one mm/s) could be applied to relatively small
objects (less than 200 meters in diameter) over many decades. In
general, the slow push systems were found to be at a very low
technology readiness level (with the exception of the gravity tractor,
which was medium) and would require significant development efforts.
Q3. What is your assessment of the need for a nuclear deflection
capability?
A3. There is no need for any deflection capability at this time. No
impact threat has yet been identified. If a timely detection capability
is fielded, there will most likely be significant warning time in which
to develop other parts of the system such as sufficiently capable
characterization and deflection spacecraft.
Q4. What are the weakest links in the ``system'' considering the
overall goal to protect Earth from asteroid impacts?
A4. Finding any potential threats so that their orbits can be
determined is the weakest link by far. Unless we find threats, we will
be unable to react. If we do find threats in a timely manner, there
will very likely be significant warning time in which to develop other
parts of the system such as sufficient characterization and deflection
spacecraft
Q5. Dr. Donald Yeomans stated that the highest priority regarding NEOs
is to ``find them early, find them early, find them early.'' Yet NASA
refused to recommend a program to find them (140 meters and larger)
early as directed by law. Why? How does NASA justify this refusal?
A5. NASA recommended an approach commensurate with the resources the
Agency has been appropriated to accomplish its tasks.
Answers to Post-Hearing Questions
Responses by Donald K. Yeomans, Manager, Near-Earth Object Program
Office, Jet Propulsion Laboratory
Questions submitted by Chairman Mark Udall
Q1. Planetary radar facilities have been cited as critical for
providing more precise orbital determinations of potentially hazardous
NEOs. However, the two radar facilities currently being used to obtain
data on NEOs [Arecibo and Goldstone] may not be available in the
future. What are the implications should existing planetary radar
facilities become unavailable?
A1. While the two mentioned planetary radars cannot participate in the
near-Earth object (NEO) discovery process, they do provide very
accurate range and velocity information that is not available with the
traditional optical positional data used to discover these objects.
Together with optical observations, the use of radar data within the
NEO orbit determination process immediately refines the object's orbit
and allows the NEO's future motion to be accurately determined so that
future close Earth approach distances can be ascertained far earlier
than would be the case without the radar data. After several years of
optical data taken at multiple returns of the NEO to the Earth's
neighborhood, a NEO orbit computed based solely upon the optical data
can also accurately predict the object's future motion. However, it
often takes many years before the necessary optical data are in hand
and for the more numerous smaller NEOs, the first discovery opportunity
is often the best opportunity to gather the necessary data prior to a
potentially threatening pass near the Earth. In short, radar data are
most critical for quickly identifying the most threatening objects and
should one be found on an Earth threatening trajectory, the use of
radar data could make the difference between having the time to
mitigate the threat or not.
Q2. Could you please explain how the Arecibo and Goldstone planetary
radar facilities work together? How, if at all, would the loss of one
of the facilities affect the orbital determination of a potentially
hazardous object? Would there be a potential effect on the accuracy,
the time required for determining a trajectory, the number of objects
to be tracked, or some combination of these factors?
A2. As noted in the response to Question 1, the use of radar data
allows for a rapid identification of a potentially hazardous object
(PHO) and a potentially Earth threatening future encounter. Although
the two planetary radars cannot ``see'' every PHO at every return to
the Earth's neighborhood, the loss of one of the planetary radars would
substantially decrease the number of PHOs having the radar data
necessary to quickly secure their orbits. Hence, without these radar
observations, it would take several years more of the optical data to
secure their orbits to a point where an Earth threatening encounter
could be ruled out (or in). With the use of radar data in the PHO orbit
determination process, there would be far more time to deal with the
PHO if it turned out to be on an Earth threatening trajectory. The
Arecibo and Goldstone radar facilities are very complementary in that
the 70 meter sized Goldstone antenna is movable and can track objects
within its range from horizon to horizon (8-10 hours). The 305 meter
Arecibo antenna has nearly three times the reach, or range, of the
Goldstone antenna but can only track objects for about two hours within
20 degrees of its overhead (zenith) position. Often a PHO is first
tracked by Arecibo and then by Goldstone (or vice versa) so the use of
both instruments is particularly valuable in terms of providing the
extended observations necessary to characterize the PHO's size, shape,
density, spin state and whether or not it has a moon. Knowledge of
these latter characteristics will be invaluable for science and for
selecting an appropriate mitigation technology--should that become
necessary.
Q3. The asteroid Apophis has been identified as an object that has a
small chance of impacting Earth in 2036. What role will Arecibo and/or
Goldstone play in improving our understanding of Apophis and refining
predictions of a potential impact?
A3. Potentially hazardous asteroid Apophis will make a very close
approach to Earth on April 13, 2029 coming as near as 4.6 Earth radii
from the Earth's surface (i.e., lower than communication satellites in
geosynchronous orbits about Earth). With the aid of radar data taken in
2005 and 2006, the orbit of Apophis has been accurately determined and
an Earth collision in 2029 ruled out. However, in the unlikely event
that Apophis passes within a 600 meter sized ``keyhole'' in space
during the 2029 close Earth passage, Apophis will return seven years
later and strike the Earth (April 13, 2036). To further refine the
existing orbit for Apophis and rule out a passage through this tiny
keyhole, we will need to understand and model some very subtle
perturbative effects due to the pressure of sunlight and the radiation
of heat from the surface of Apophis. In order to do this, it will be
important to determine the size, shape and spin state of Apophis.
Arecibo radar observations made in early 2013 would allow these
physical observations to be made. Together with optical data, radar
observations in 2013 would reduce the 2029 orbit uncertainties by more
than 90 percent. Thus, it is very likely that the passage of Apophis
through the 2029 keyhole (and impact in 2036) can be ruled out.
Q4. How do the capabilities of Pan-STARRS compare to that of LSST? Are
they complementary facilities for an expanded NEO Survey, or could one
facility meet the goal of detecting NEOs as small as 140 meters in size
in a timely fashion?
A4. Both Pan-STARRS and LSST have the capability to be far more
efficient in finding NEOs than any of the currently operating surveys.
The efficiency with which a search telescope can detect NEOs is
proportional to the size of the telescope's aperture area multiplied by
the telescope's field of view. The four telescope array of the planned
Pan-STARRS has four 1.8 meter telescopes each with a field of view of
seven square degrees. LSST has a single 8.4 meter telescope (effective
aperture = 6.7 meters) with a 9.6 square degree field so LSST would be
about five times more efficient in terms of NEO discoveries. However,
Pan-STARRS will be located on Hawaii in the northern hemisphere while
LSST will be located in the southern hemisphere so these telescopes
will be viewing different regions of the sky and will have different
weather patterns. Thus they will be very complementary search systems
and their observing schedules, search regions and data reduction
techniques could be coordinated to ensure a more efficient and robust
search strategy. With a start in 2014, the LSST, optimized for NEO
searches (as described in Dr. Tyson's testimony), could reach the goal
of discovering 90 percent of the potentially hazardous asteroids 140
meters and larger by 2026. In addition, with the Pan-STARRS four
telescope array also operational by 2010, the goal could be reached
almost two years earlier. Furthermore, the placement of Pan-STARRS in
the north and LSST in the south would provide for an increase in
warning efficiency for those smaller and more numerous objects that are
discovered on their final approach to Earth.
Q5. The Discovery Channel Telescope is under construction and expected
to become operational in 2010. The telescope design is expected to
enable versatility in its use, which could include the detection of
near-Earth asteroids. One estimate puts the total cost of building the
telescope at $40-50 million. What contribution, if any, would this type
of low-cost telescope provide to the expanded NEO Survey? Should this
system be considered as part of the next-generation search or as part
of a gap-filler until a Survey using LSST and/or Pan-STARRS gets
underway?
A5. The Discovery Channel Telescope has an aperture size of 4.2 meters
and when used in the (as yet unfunded) prime focus mode, will have a
field of view of 2.3 square degrees. For NEO discovery, it will then be
about two times less efficient than Pan-STARRS and 11 times less
efficient that LSST. However, the Discovery Channel Telescope will be
far superior to any currently used NEO search telescopes and could by
itself discover more than 50 percent of the PHAs larger than 140 meters
within ten years time. It will be located in Arizona so that it will be
in a different region of the world (with different weather patterns)
from both Pan-STARRS and LSST. The Discovery Channel Telescope should
indeed be considered part of the next generation search.
Q6. What are the data management requirements to support the expanded
Survey and what should the priorities be in addressing those
requirements? How big a job is it likely to be?
Q6a. Dr. Green's testimony indicates that NASA has started to evaluate
the needs of the Minor Planet Center to accommodate the increase in
detection that will result in an expanded survey. Should NASA consider
other entities for handling data management under the expanded search?
Should the data management task be competed?
A6a. Currently the Minor Planet Center (MPC) is receiving, processing
and archiving up to 75,000 observations each day and as the next
generation of search gets underway, that amount could increase 100-
fold. Steps are already underway to establish the interfaces necessary
for the MPC to interact with the next generation surveys and manage the
enormous increase in data they will provide. In a change from the
current survey data processing procedures, the next generation surveys
(e.g., Pan-STARRS, LSST) will do much of their own data processing,
including the identification of their nightly observations with
existing asteroids, the computation of preliminary orbits for newly
discovered objects and the archiving of these data. This moving object
pipeline system (MOPS) is well along in its development and both Pan-
STARRS and LSST will take advantage of it. Hence, while the increased
work load on the MPC will be significant, much of the work will be
carried out by the surveys themselves. Steps are being taken to ensure
that the transition to the next generation search is smooth and that
the data processing is nearly completely autonomous so only a modest
increase in staffing at the MPC will be required. In the NASA call for
Near-Earth Object Observations peer-reviewed proposals in early 2008,
there will be an opportunity for other institutions to compete for the
role that the MPC in Cambridge Massachusetts is currently fulfilling.
Q7. How much time would be required to prepare a mitigation approach
if a hazardous object were discovered to be on a collision course with
Earth? How much time would likely be available?
A7. Once the current NEO survey goal has been reached, some 90 percent
of the one kilometer and larger sized NEOs will have been discovered.
Once the next generation search is complete, all of the one kilometer-
sized NEOs will have been discovered along with 90 percent of those
potentially hazardous objects larger than 140 meters. At that point, 99
percent of the statistical or actuarial risk from NEOs will have been
retired since it will then be possible to track their motions decades
into the future and determine if any among them represent a threat to
Earth. This is the key issue for getting on with the next generation
search--we must find them early enough to allow the time to mitigate if
a true Earth threatening object is discovered. After the next
generation of search is complete, 90 percent of the 140 meter sized
objects will have well understood future motions and should one of them
have a significant non-zero Earth impact probability, there would be
typically decades to further refine the orbit using optical and radar
data and in the vast majority of cases, these additional data will
collapse the orbital uncertainties to such an extent that troublesome
future Earth encounters can be ruled out. If, in the unlikely event
that an Earth impact cannot be ruled out, there should be the necessary
number of years to place a spacecraft in orbit about the asteroid,
track it and hence accurately monitor the asteroid's motion to
determine if the threat remains real. In addition, this rendezvous
spacecraft would then be available to monitor the asteroid's motion
subsequent to a deflection attempt (e.g., by an impacting spacecraft)
to verify that the attempt had been successful in avoiding the
potential Earth impact at the predicted time. This monitor spacecraft
could also verify that the deflection attempt did not push the asteroid
into a tiny nearby keyhole in space that would bring it back to a
subsequent Earth impact. This latter possibility, while very unlikely,
could then be mitigated using the small gravitational ``pull'' of the
close neighboring spacecraft being used as a gravity tractor.
The development and flight of a rendezvous spacecraft along with
the mitigation approach would likely take 10-20 years depending upon
the impactor's orbit, the available launch vehicle, the launch
opportunities and the mitigation technique itself. The next generation
of search is designed to provide many decades of advance warning time
for the vast majority of Earth threatening asteroids.
Q8. Dr. Green's testimony described NASA's NEO contingency
notification plan, which lays out the procedures for notification up
through the NASA Administrator if a NEO is detected with a significant
probability of impacting Earth. Does a notification or warning system
exist beyond NASA for informing the public and federal and State
disaster and emergency response agencies? If not, what should be done?
A8. To my knowledge, there currently exists no notification or warning
system beyond NASA for informing the public and federal/State disaster
and emergency response agencies. However, the next generation of search
for potentially hazardous objects (PHOs) will dramatically increase
both the number of known PHOs in the population and the number of
warnings where the risk of a PHO Earth impact cannot be immediately
ruled out. During the next generation of PHO search, these warnings
could increase by up to a factor of 40 over what we currently
experience. I would recommend that the lines of communication be opened
between NASA's NEO program and the U.S. disaster response agencies to
begin the long-term planning for these warnings and for the rare
circumstance where one of these PHO warnings turns into a real threat.
Questions for the Record Submitted by Representative Tom Feeney
Q1. NASA's NEO report, delivered this March, provides several options
for meeting the goal of achieving 90 percent detection, tracking and
characterization of Potentially Hazardous Objects, and the report
establishes a clear relationship between resources invested and the
time needed to achieve 90 percent coverage. In essence, the report
shows that for an additional investment of approximately $536 million,
we could buy-down a decade of time to complete the survey. In your
view, is that additional investment necessary? Does the threat posed by
PHOs compel faster completion of the survey?
A1. While the mean time between impacts for 140 meter sized potentially
hazardous objects (PHOs) is approximately 5,000 years, the next impact
is equally likely to occur tomorrow morning or in 5,000 years. The mean
time between impacts of the far more numerous 50 meter sized PHOs is
about 700 years and hence the impact probability for one of these
impacts in this century is about 13 percent. NASA currently invests
approximately $4 million dollars per year in its NEO Observations
program and if the current NEO surveys continue at the current level of
activity, it would take more than a century to reach the goal of
finding 90 percent of the PHOs larger than 140 meters. To reach this
goal by the end of the 2020, as requested in the NASA Authorization Act
of 2005, the survey could be done with the aid of a dedicated LSST
class 8.4 meter telescope (2015 start time) or done using a space-based
infrared telescope of 0.5 or 1.0 meters (2012-2014 start). If the 2020
goal line is relaxed a few years, the 90 percent completion goal could
be achieved in 2026 with the LSST used in a shared mode with only 15
percent of the time being devoted exclusively to PHO searches. As
outlined in the testimony of Dr. Tyson, this option would require about
$125 million dollars for the entire effort through 2026.
The threat posed by PHOs is real and the impact of a 140 meter
sized PHO would strike the Earth's surface with the energy equivalent
of about 100 mega tons of TNT explosives--roughly 7,700 times more
energetic than the Hiroshima nuclear device. Nevertheless, it is my
personal opinion that, given the infrequency of impacts by relatively
large PHOs upon the Earth, there is no compelling reason to insist upon
a survey completion by 2020; a relaxation of the completion date by 5-
10 years would be acceptable.
Q2. What are the most difficult types of NEOs to detect? Is there, for
instance, a portion of the sky that won't be covered by ground-based
facilities? Are there certain types of orbits that make it difficult to
detect and track asteroids and comets?
A2. With the exception of a single search telescope located in Siding
Spring Australia, all current NASA supported NEO search telescopes are
located in the northern hemisphere. However, the orbits of NEOs will,
over time, bring them into view from the northern hemisphere so that
for discovery purposes, the paucity of search telescopes in the south
is not a particular problem. However, for warning of objects that are
on a final Earth threatening trajectory, northern and southern
hemisphere observation capabilities are required. The most difficult
NEOs to detect include those objects that 1.) spend most of their time
interior to the Earth's orbit (i.e., they are rarely visible in a dark
sky) or 2.) they do not often return to the Earth's neighborhood. This
latter scenario can arise because they have relatively long orbital
periods about the sun or their orbital periods are similar to that of
the Earth so they can spend long periods of time before approaching the
Earth or becoming visible in the night sky.
Q3. Once the LSST and Pan-STARRS telescopes are operating, and surveys
for PHOs that are 140 meters or larger has commenced, what is the
business and public safety case for expanding the search to detect and
track smaller PHOs--for instance, down to a size of 50 meters? What are
the cost and schedule implications?
A3. Fifty meters is roughly the lower size limit where a rocky Earth
impacting object could be expected to cause ground damage from an air
blast. That is, an object of this size would not generally punch
through the Earth's atmosphere and strike the Earth but it would be
expected to cause an explosion a few kilometers above the Earth's
surface and hence cause ground damage. For example, nearly 100 years
ago in June 1908, a 50 meter sized object is thought to have created a
5-10 megaton (of TNT) explosive event in the Tunguska region of Siberia
causing ground damage over a region of 2,000 square kilometers.
As one moves down to smaller and smaller PHOs, they become more and
more numerous so while there may be more than 10,000 PHOs larger than
140 meters, there is likely to be seven times that number of PHOs
larger than 50 meters. The current ongoing survey goal to discover and
track 90 percent of the one kilometer and larger sized objects has
discovered about five percent of the smaller objects down to 140 meters
in size. Similarly, simulations suggest that the next generation search
for PHOs down to 140 meters that includes only Pan-STARRS (2010 start)
and LSST (2014 start) will discover roughly 42 percent of the
potentially hazardous objects (PHOs) larger than 50 meters by the end
of 2020 and 59 percent by the end of 2029. If one were to include in
the next generation search a one meter infrared telescope in a Venus-
like orbit (2014 start) in addition to the ground-based Pan-STARRS and
LSST surveys, the discovered population of 50 meter and larger sized
objects would be complete to the level of 78 percent at the end of 2020
and 92 percent complete by the end of 2029. However, this latter result
would depend upon a rather long 15 year lifetime for the infrared space
telescope and would entail significant data down-link issues.
I am not aware of a study to determine survey costs for discovering
and tracking 90 percent of the 50 meter sized PHOs but it would likely
require far more resources than have been considered to date. It is
true that the likelihood of Earth being struck with a 50 meter sized
PHO is about seven times that for a PHO of 140 meters. However, at some
point there is a crossing between the diminishing hazard from smaller
and smaller objects and the increasing costs required to find them. It
should be noted that the completion of the goal to discover and track
90 percent of the PHOs larger than 140 meters would retire 99 percent
of the actuarial risk from PHOs of all sizes so this is the appropriate
goal for the next generation of search. A future study of this issue
would have to determine whether or not a comprehensive survey to
discover 90 percent of the smaller PHOs down to 50 meters in the near
future would be cost effective.
Q4. During the hearing several witnesses mentioned the Air Force's
funding of the Pan-STARRS telescope facility in Hawaii as a possible
new ground observatory that would be very adept at detecting NEOs. What
is the status of Pan-STARRS and the likelihood that all four telescopes
will be built? Would the Air Force be willing to make available a
portion of the telescope's time to NEO surveys if less than four
telescopes are built?
A4. The Pan-STARRS project is a University of Hawaii Institute for
Astronomy effort that has been sponsored through United States Air
Force grants beginning in FY 2002. The project has been proceeding well
in developing the world's largest digital cameras, high precision wide
field optics, and software systems to process and archive an
unprecedented stream of world class astronomical research data. The
ownership and operations of the Pan-STARRS systems is under the
authority of the University of Hawaii.
The ultimate goal is to construct four co-located 1.8 meter
aperture telescopes (PS4) that will function as a single unit each
clear night to search the entire accessible sky twice each lunar month
(about 28 days). It seems likely that the PS4 four telescope system
will be built within a few years, but the precise schedule will depend
upon the availability and timing of the necessary funding as well as
completing the construction permitting process that includes a federal
environmental impact statement (EIS). As noted in the EIS Preparation
Notice published in the Federal Register in January 2007, the preferred
site is at the Mauna Kea summit on the Big Island of Hawaii, and the
alternate site is the Haleakala summit on the island of Maui.
Prior to construction of the four telescope array, a prototype
single 1.8 meter telescope (PS1) has been built and sited at the
Haleakala summit. The state-of-the-art 1400 megapixel (1.4 billion
pixel) CCD camera has been built, tested and mated to the telescope,
and the telescope itself achieved ``first light'' on Aug. 22, 2006.
Development is nearly complete of the image processing pipeline (IPP)
and the Moving Object Processing System (MOPS) that is designed to
identify moving objects within our Solar System (mostly asteroids), and
preliminary testing is well underway. An international consortium has
committed $10M to fund a 3.5 year PS1 science mission that should begin
in mid-2008. Once operational, the primary objective of PS1 is to
discover near-Earth objects and it should be more than 20 times more
efficient at finding them than any currently operational NEO search
effort. This will be true even though the telescope will be conducting
a suite of other scientific observations including studies of outer
solar system objects, planets around other stars, supernova, galaxy
clusters, and gravitational lensing. The supernova and gravitational
lensing studies will significantly clarify our current understanding of
the dark energy and dark matter issues at the forefront of modern
cosmology.
At this time, the best estimate for beginning PS4 construction is
late 2009 or early 2010. This is primarily due to the timescale for
completing the EIS and obtaining the necessary construction approvals.
If sufficient funding continues to be available, the likelihood is high
to successfully complete the full system. Commissioning of the first
one or two PS4 telescopes should begin in 2011 with the completed four
telescope suite becoming fully operational in 2013.
Q5. One deflection solution, suggested by NASA, is to detonate a
nuclear device in the vicinity of a PHO. What are the advantages and
disadvantages of using this approach? What circumstances would argue
against using a nuclear device in lieu of alternative approaches?
A5. There are two categories of mitigation responses for Earth
threatening PHOs: a relatively quick flight time impulsive push
(perhaps by an impacting spacecraft or a nuclear device) or a longer
flight time rendezvous mission followed by either an impulsive or slow
push technique (e.g., gravity tractor). If there is sufficient time,
the longer flight time rendezvous is preferred because a resident
spacecraft can provide both a verification that the asteroid is
actually on an Earth threatening trajectory or not and it can verify
that a deflection maneuver was successful. A nuclear device could be
used in a stand-off mode where the explosion is above the asteroid's
surface so that the resultant neutron radiation then ablates the
asteroid's front side and introduces a thrust in the direction opposite
to the vaporizing material. A far more efficient, but less controlled,
technique could be achieved by placing the nuclear device upon, or
below, the asteroid's surface. A nuclear response may be required for a
large (larger than a few hundred meters) PHO that is found to be on an
Earth-threatening trajectory and for which there is not sufficient time
to use an alternate technique. This is a very unlikely scenario since
the larger objects that might require a nuclear response are also the
easiest to discover so a large Earth threatening object will likely be
discovered many decades in advance of the potential impact event thus
allowing the use of an alternate technology that lacks the problems of
the nuclear option--problems that include launch safety, public concern
and the possible necessity to modify existing treaties. The advantages
of using a nuclear device are that one or more devices could deliver to
an Earth threatening asteroid far more energy per kilogram of delivered
(launch) mass than any alternative mitigation technique and the
technology is mature. The disadvantages include the surface interaction
of such a powerful impulsive device with a PHO of unknown structure,
which would introduce an uncertainty in the deflection response and
possibly a partial breakup of the asteroid itself. The latter scenario
might introduce a shotgun-like effect upon the Earth unless the breakup
and subsequent dispersal could be initiated soon enough prior to a
potential collision that the vast majority of the small fragments would
miss the Earth altogether. In short, a nuclear device option should be
maintained as a viable mitigation technology but utilized only in the
relatively rare situations when a more controlled deflection technique
is not adequate or possible.
Questions submitted by Representative Dana Rohrabacher
Q1. The need for a comprehensive potentially hazardous NEO program
seems to require expertise of several agencies. How do you suggest
coordination be handled?
A1. NASA has been properly given the responsibility to discover, track
and catalog near-Earth objects (NEOs) and to determine if any of these
objects pose a future threat to Earth. For these efforts, a number of
governmental and academic agencies have provided advice and expertise
along with survey search and computing facilities. My suggestion would
be to maintain NASA's lead role in these activities. In the event a
potentially hazardous object (PHO) is found to be on an Earth
threatening trajectory, a mitigation technology effort may be required.
Such an effort would require that a spacecraft be built, launched,
tracked and navigated to rendezvous with the PHO to monitor its motion
and conduct a mitigation procedure if that were warranted. Within the
U.S., only NASA has that type of experience so it would seem to me that
NASA should be given the U.S. lead in mitigation technology planning as
well. NASA should, of course, solicit suggestions and advice from other
relevant agencies. In particular, should a nuclear deflection
mitigation attempt become necessary, other U.S. agencies (e.g., DOD,
DOE) would need to be intimately involved in the mitigation attempt.
The threat of a PHO impact is an international problem and should
have an internationally agreed upon solution. Such a threat could
generate far more problems than just the technologies required for
mitigation--including effective communication with the public and
disaster preparedness. To my knowledge, there has been very little
discussion within the international community to address the totality
of the PHO threat issues. There is an ongoing activity within the
Association of Space Explorers to address some of these issues and they
plan to introduce a draft NEO deflection protocol to the Scientific and
Technical Subcommittee of the U.N. Committee on the Peaceful Uses of
Outer Space (COPUOS) during their 2009 session. One possible way
forward would be the assignment of responsibility to a particular U.S.
government agency to begin interagency discussions to define the NEO
mitigation responsibilities of specific government agencies and to
establish a recommended strategy for selecting a mitigation technology
option. These U.S. discussions and recommendations would then need to
be coordinated and integrated with those arising from the activities of
the UN/COPUOS Scientific and Technical Subcommittee in 2009.
Q2. Describe some of the proposed mitigation techniques and their
trade offs.
Q3. What is your assessment of the need for a nuclear deflection
capability?
A2,3. Some of the following discussion has been mentioned in response
to Representative Feeney's question 5. For completeness, some points
are repeated below.
Viable mitigation techniques for deflecting Earth threatening
asteroids can be grouped into two categories. The first category of
mitigation techniques includes ``slow push'' technologies that are
designed to change the asteroid's orbital velocity over relatively long
periods of time. The second category includes impulsive events that are
designed to change the asteroid's orbital velocity using the energy of
an explosive device or the energy imparted to the asteroid as a result
of a high velocity impacting spacecraft. Either category of mitigation
technology would benefit from a rendezvous spacecraft that would be
placed in orbit around, or hover near, the hazardous asteroid.
Radiometric tracking of this ``monitor spacecraft'' could be used to
dramatically improve the orbit of the asteroid and hence determine
whether or not it was actually a threat to Earth. Should a deflection
maneuver prove necessary, this monitor spacecraft could continue to
track the asteroid during and after the deflection attempt to verify
that the deflection was successfully carried out and the asteroid would
indeed miss the Earth at the predicted impact epoch. Finally, in the
very unlikely scenario that the deflection maneuver prevented an Earth
impact at a certain future epoch number 1 but pushed it toward a tiny
keyhole in space that would allow it to strike Earth at a subsequent
impact epoch number 2, the monitor spacecraft could be used as a
gravity tug to move the asteroid the few hundred meters necessary to
prevent the asteroid from entering the impact plane keyhole. In short,
if there is sufficient time, a monitor spacecraft should be maintained
in the immediate neighborhood of the Earth threatening asteroid.
Within the first category of slow push techniques, there are only a
few viable methods that could be used including the ``tugboat''
approach where the spacecraft attaches to the asteroid and uses its
thrusters to slowly tow it and the so-called gravity tractor where a
massive spacecraft uses its thrusters and the gravitational attraction
between the spacecraft and asteroid to gently pull the asteroid and
alter its orbital velocity and position in space. The tugboat approach
presents significant engineering challenges in that it must first
secure the asteroid in its grip, and then tow it using its thrusters,
being careful to thrust only when the asteroid's rotation brings it
back to the same position in space. The gravity tractor approach, with
its tiny pull capability, needs to be very close to a rotating
irregular asteroid so it has challenges in safely maintaining the
necessary close proximity to the asteroid. Some attention has been
given to other slow push techniques including solar concentrators or
pulsed lasers that could focus intense radiation on the asteroid,
ablate or vaporize the near side material and thus introduce a small
thrust in the opposite direction from the material that is streaming
off the asteroid's side nearest the solar concentrator or laser device.
Both of these techniques would provide significant engineering
challenges and each system would have vaporizing material driven back
toward the devices themselves--thus attenuating the intensity of the
focused radiation and perhaps contaminating the system's optics.
Within the second category of impulsive deflection techniques, the
high velocity spacecraft impact and the explosive device impulse
techniques (including nuclear devices) are mature technologies. A high
velocity impact of a spacecraft with comet Tempel 1 was successfully
carried out by NASA in July 2005 so the autonomous navigation
technologies for such a deflection technique have already been
demonstrated. However, a high velocity impact of a spacecraft with a
target asteroid will produce only a modest change in the asteroid's
velocity and is only a useful technology if the asteroid is smaller
than a few hundred meters in diameter or there are many years available
between the deflection attempt and the predicted Earth impact.
One or more nuclear devices could be used in a stand-off mode where
the explosion is above the asteroid's surface so that the resultant
neutron radiation then ablates the asteroid's front side and introduces
a thrust in the opposite direction to the vaporizing material. A far
more efficient, but less controlled, technique could be achieved by
placing the nuclear device upon, or below, the asteroid's surface. This
nuclear response may be required for a large (larger than a few hundred
meters) PHO that is found to be on an Earth threatening trajectory and
for which there is not sufficient time to use an alternative technique.
The advantages of using a nuclear device are that one or more devices
could deliver to an Earth threatening asteroid far more energy per
kilogram of delivered (launch) mass than any alternative mitigation
technique and the technology is mature. The disadvantages include the
interaction of such a powerful impulsive device with the surface of a
PHO of unknown structure, which would introduce an uncertainty in the
deflection response and possibly a partial breakup of the asteroid
itself. The latter scenario might introduce a shotgun-like effect upon
the Earth unless the breakup and subsequent dispersal could be
initiated soon enough prior to a potential collision that the vast
majority of the small fragments would miss the Earth altogether. In
short, a nuclear device option should be maintained as a viable
mitigation technology but utilized only in the relatively rare
situations when a more controlled deflection technique is not adequate
or possible.
Answers to Post-Hearing Questions
Responses by Donald B. Campbell, Professor of Astronomy, Cornell
University; Former Director, Arecibo Observatory
Questions submitted by Chairman Mark Udall
Q1. The asteroid Apophis has been identified as an object that has a
small chance of impacting Earth in 2036. What role will Arecibo play in
improving our understanding of Apophis and refining predictions of a
potential impact?
A1. During the close approach of Apophis to the Earth in 2013 at a
distance of about nine million miles, it is my understanding that radar
observations with Arecibo and Goldstone combined with optical
measurements will significantly reduce the probability of a potential
impact during its passage by the Earth in 2036. Arecibo observations in
2013 will provide some information about Apophis's size but its large
distance will preclude the high resolution characterization
measurements that would provide detailed information about its shape
and size.
Q2. Your testimony notes that ``No study has been done of the precise
role that the Arecibo radar and how many hours of NEO observations will
be needed when the new, high sensitivity searches commence. . .. This
needs to be done.'' What, specifically, would such a study entail, what
entity or entities would be capable of conducting it, and how much time
do you believe such a study would require?
A2. Such a study would entail determining the number and distribution
of the hours of use of the radar system on the Arecibo telescope that
would be needed for follow-up astrometric and characterization
observations of newly discovered NEOs once the Pan-STARRS and LSST NEO
searches are underway. Such a study would be best carried out by the
National Astronomy and Ionosphere Center, which operates the Arecibo
Observatory for the NSF, with input from the scientists involved with
NEO radar observations and orbit determination at Arecibo and the Jet
Propulsion Laboratories. The first Pan-STARRS system is expected to
come online in the next year leading to a significant increase in the
NEO detection rate. Direct experience with this system will provide the
best guide as to the needed increase in the hours of operation of the
Arecibo radar. Based on this, the study should be completed by early
2009.
Q3. What is the estimated cost of decommissioning the entire Arecibo
observatory and what is the estimated time that would be required to
disassemble the facility?
A3. There is no current reliable estimate for the cost of
decommissioning the entire Arecibo Observatory. The National Science
Foundation has contracted for a study of the decommissioning costs. My
understanding is that the contractor will deliver their report to the
NSF in February, 2008.
Questions from Representative Tom Feeney
Q1. NASA's NEO report, delivered this March, provides several options
for meeting the goal of achieving 90 percent detection, tracking and
characterization of Potentially Hazardous Objects, and the report
establishes a clear relationship between the resources invested and the
time needed to achieve 90 percent coverage. In essence, the report
shows that for an additional investment of $536 million, we could buy
down a decade of time to complete the survey. In your view, is that
additional investment necessary? Does the threat posed by PHOs compel
faster completion of the survey?
A1. Given the relatively low probability in any given year of an impact
by a NEO, in my view significant expenditures to complete the survey in
a shorter time period are not justified. If significant cost savings
can be achieved by extending the deadline a small number of years
beyond 2020 then this should be seriously considered. Dr. Tyson's
testimony indicated that by devoting 15 percent of the observing time
on the LSST to NEO searches the 90 percent requirement could be
achieved in about 12 years. Assuming that the LSST begins operations in
2014, this would mean a completion of the survey by 2026. This date
does not include contributions from other searches such as Pan-STARRS.
Providing partial support for the construction and operating costs of
the LSST for a NEO survey would appear to be a cost effective method
for completing the survey.
Q2. What are the most difficult NEOs to detect? Is there, for
instance, a portion of the sky that won't be covered by ground-based
facilities? Are there certain types of orbits that make it difficult to
detect and track asteroids and comets?
A2. NEOs whose orbits are primarily interior (i.e., closer to the Sun)
to Earth's orbit are more difficult to detect from Earth than those
NEOs that spend most of their time outside the Earth's orbit because
they need to be observed shortly after sunset or shortly before
sunrise.
Q3. Once the LSST and Pan-STARRS telescopes are operating, and surveys
for PHOs that are 140 meters or larger has commenced, what is the
business and public safety case for expanding the search to detect and
track smaller PHOs--for instance, down to size 50 meters? What are the
costs and schedule implications?
A3. As discussed during the Hearing, the difficulties of finding NEOs
increases as their size gets smaller. The 140 meter size limit for 90
percent completion seems a sensible and achievable goal for now in
terms of the potentially available resources and costs. As pointed out
by Mr. Schweickart, this search, if it is carried out, should also find
close to 50 percent of objects down to 50m in size. As the search
progresses, the issues related to a ``complete'' survey of smaller NEOs
can be realistically addressed and decisions made.
Q4. You state that Cornell was required by NSF to seek other funding
commitments to fill the void left by NSF's reduction. What has been
Cornell's experience finding new funding? Are you optimistic that other
sources will be found?
A4. Cornell representatives are in ongoing discussions with
governmental and educational bodies in Puerto Rico and they are
moderately optimistic that funding for programs that enhance the role
of the Arecibo Observatory in education and public outreach can be
obtained through, or in collaboration with, Island institutions.
However, these programs would not, and should not, be a substitute for
the observatory's basic research mission. It appears very unlikely that
year-on-year funding can be obtained from sources within Puerto Rico or
elsewhere to partially support the operation of the observatory as a
federally owned and funded scientific research institution except
possibly, in the case of the observatory's planetary radar program,
from NASA.
Q5. One deflection solution, suggested by NASA, is to detonate a
nuclear device in the vicinity of a PHO. What are the advantages and
disadvantages of this approach? What circumstances would argue against
using a nuclear device in lieu of alternative approaches?
A5. I have not spent adequate time studying this issue to make an
informed response to the question.
Questions submitted by Representative Dana Rohrabacher
Q1. With regard to NASA's Spaceguard program, what changes, if any, do
you recommend to make the program more effective? In your view, is
further legislation required from Congress to implement needed changes?
A1. I am not directly involved with NASA's current Spaceguard program
aimed at discovering 90 percent of NEOs with sizes larger than one km.
This program was a search program and appears to be largely achieving
its objectives. It is now important to move to the next stage currently
under discussion, the discovery of 90 percent of NEOs larger than 140m,
determination of which ones are truly potentially hazardous via orbit
determination and the investigation of possible mitigation schemes
based on characterization studies.
Q2. How important do you consider characterization in the overall NEO
issue priorities?
A2. Characterization has two objectives: 1) The understanding of the
range of properties exhibited by NEOs to inform the design of
mitigation strategies; 2) The characterization of specific objects that
pose a definite threat to Earth so that the appropriate mitigation
strategy can be implemented. The first of these is ongoing and the
coming more sensitive searches will potentially provide a larger range
of asteroid characteristics to be included in mitigation studies. These
studies need to be pursued. For the second case, clearly the
identification of PHOs via searches coupled with precise orbit
determination to identify any objects that truly do threaten Earth
comes first with characterization an input to mitigation planning.
Q3. What capabilities are required for a comprehensive deflection
campaign?
A3. As discussed by Mr. Schweickart and others, the technology needed
for a comprehensive deflection campaign largely already exists. What is
missing is a program with clear responsibility for its implementation
vested in one organization.
Q4. What is your estimate of the number of undiscovered asteroids in
the 140 meter and above range? Describe the potential damage that an
asteroid in the 140 meter range can cause striking an ocean within,
say, 500 miles of a U.S. coast?
A4. The March 2007 NEO Report to Congress gives the estimated number of
NEOs greater than 140m in size as approximately 100,000. The impact
energy for a 140m NEO would be about 100 megatons of TNT equivalent.
Published studies have shown that the release of this much energy as a
result of an impact into the ocean would certainly have the potential
for a very serious consequences to the local and, perhaps, distant
seaboards.
Q5. Asteroids are more easily detected in the infrared spectrum. An
asset such as the WISE satellite has an effective capability for
searching for NEO's infrared output. Is WISE being tasked for this
role? What other infrared detection devices can or will be used to
detect NEOs?
A5. I am not involved with the WISE satellite program. This question
would be better answered by NASA.
Q6. Could you describe some of the losses that might occur to U.S.
research in radio and radar astronomy, and atmospheric sciences if the
facility were to close as threatened by one of the supporting NSF
directorates? How is the telescope unique? What unique research
opportunities does Arecibo offer the U.S. and global scientific
community? What new research is scheduled and proposed for Arecibo?
A6. Arecibo is the world's largest single dish radio telescope with
sensitivity in its frequency band that is four to five times higher
than any other single dish radio telescope. It is also unique in that
it is equipped with two very high powered transmitters used for radar
studies of solar system bodies including NEOs and for studies of the
Earth's ionosphere. Its great sensitivity has allowed Arecibo to play a
critical role in the study of pulsars with one notable example being
the discovery of the binary pulsar PSR 1913+16 for which timing
measurements, also using Arecibo, gave the first strong evidence for
the existence of gravitational waves. Russell Hulse and Joseph Taylor
received the Noble prize in 1993 for this work. Arecibo's sensitivity
will continue to make it a major contributor via pulsar observations to
study of gravitational waves, tests of General Relativity, the
properties of nuclear matter in neutron stars, the electron density
distribution and magnetic fields in our galaxy and, potentially, black
holes via the hoped for discovery of a black hole--neutron star (i.e.,
pulsar) binary system.
Because of it sensitivity, Arecibo is the only radio telescope than
can study gas (i.e., neutral hydrogen in distant galaxies) over a
cosmologically significant volume allowing it to study how gas and dark
matter are distributed and evolve through cosmic time. This is one of
the major current research programs at the Arecibo Observatory with
participants from a significant number of universities and research
institutions in the U.S. and abroad.
Arecibo's ionospheric research program is supported by the NSF
Division of Atmospheric Sciences. Arecibo is the most sensitive
component of a chain of incoherent scatter ionospheric radars supported
by the NSF stretching from the polar regions to the magnetic equator.
The results from coordinated observations by all the participants in
the chain provides input into ionospheric modeling programs the results
of which impact the study of Space Weather and are potentially
important for climate change studies. Arecibo's location allowing it to
study the ionosphere at mid-magnetic latitudes makes it a unique
contributor to this effort.
Arecibo is one of only two high powered radar systems with the
capabilities for studying solar system bodies and it is the most
sensitive by a factor of about 20. It makes major contributions to the
orbit determination and characterization for NEOs including comets, to
studies of the surfaces and internal structure of the Moon and
terrestrial planets, and to the study of planetary satellites.
The closing of the world's largest radio telescope means that its
great sensitivity will not be available for the ongoing research work
described above or for other continuing research efforts. Perhaps just
as importantly, it also means that Arecibo will not be available to
pursue new research opportunities that may arise in the future that can
be best exploited by utilizing a telescope with Arecibo's sensitivity.
The discovery of pulsars is a classic example, it was almost as if the
designers of the Arecibo telescope had pulsar research in mind before
pulsars were discovered.
Q7. Please describe some of the resources that Arecibo provides for
discovery and research programs and examples of results.
A7. As described above, Arecibo's huge collecting area makes it the
most sensitive single dish telescope in the world. Its two high powered
transmitters give it unique capabilities for radar studies of solar
system bodies and the Earth's ionosphere. The Observatory is also
equipped with an array of optical instruments that are used for studies
of the lower part of the ionosphere.
Among Arecibo's many accomplishments are: 1) the discovery of a
significant number of known pulsars including the binary pulsar that
led to our best indication that gravitational radiation exists and the
first milli-second period pulsar, a class of very fast rotating pulsars
that are the most precise pulsar ``clocks'' needed, for example, in the
proposed pulsar gravitational wave ``observatory''; 2) The discovery of
the first planets around another star, in this case a neutron star; 3)
The mapping of the structure of the local universe from redshift
(recessional velocity) measurements based on observations of neutral
hydrogen in galaxies; 4) The discovery that Mercury rotates 1.5 times
for each orbital ``year'' about the Sun and, in conjunction with the
Goldstone radar and the NSF Green Bank Telescope, that Mercury has at
least a partially molten core; 5) The first mapping of the surface of
Venus at high enough resolution to study its surface features; 6)
Confirmation of the existence of binary NEOs; 6) The confirmation of
the Yarkovsky leading to a revolution in our ideas on how small
asteroids move from the main asteroid belt between Mars and Jupiter
into the inner solar system to become NEOs; 7) Detailed studies of the
electron density distribution, temperature, winds and composition of
the Earth's ionosphere.
Answers to Post-Hearing Questions
Responses by J. Anthony Tyson, Professor of Physics, University of
California, Davis; Director, Large Synoptic Survey Telescope
Project
Questions submitted by Chairman Mark Udall
Q1. Your testimony notes that by making adjustments to the LSST
observations, the expanded NEO survey could be completed within 12
years and that ``the current cost estimate for LSST in 2006 dollars is
$389M for construction and $37M per year for operations. For a 12-year
long survey, the 15 percent of the total cost is $125M.'' What is the
breakdown of the $125M estimate for the NEO-related activities, and is
it inclusive of the 12-year operations? How confident are you of that
cost estimate, and why?
A1. The LSST construction and operations budget are based on proven
estimating practices of dividing the entire project into over 1,000
individual work tasks and obtaining documented cost estimates on each
task either from commercial vendor estimates or engineering estimates.
The total cost estimate also contains a 30 percent contingency to
absorb unexpected technical problems and/or higher costs than estimated
today. The costing process and the estimates have been peer reviewed
and endorsed by an NSF panel of external experts. The $125M figure was
calculated from the extra effort in an LSST survey of the sky required
to reach the Congressional goal of 90 percent completeness for
Potentially Hazardous Asteroids (PHA) of 140 meter diameter and larger.
This extra effort was quantified through multiple simulations of LSST
operations. We are confident that this is an accurate estimate of the
level of effort required. This extra effort devoted to the PHA
discovery program amounts to $120M during operations, plus $5M for
development of advanced orbit linking and operations pipeline software.
The $120M is inclusive of the added PHA portion of operations during
the full 12-year survey.
Q1a. Your testimony also mentions that ``To keep LSST on schedule,
about $5M should be spent on optimized NEO orbit software pipeline
development in the last phase of R&D and the construction phase. . ..''
Is this funding included in the $125M overall cost required to modify
LSST for the NEO survey?
A1a. Yes.
Q1b. When would the required software development for the NEO survey
need to begin in order to start the Survey in 2014, assuming LSST
commences operations at that time?
A1b. 2009.
Q1c. What approvals and funding are required before LSST can be
developed and how confident are you that LSST will be ready for
operations in 2014-2015, as noted in your testimony?
A1c. The LSST project has been funded for R&D by the NSF. The
construction proposal to the NSF was reviewed in September 2007 and the
project had been recommended to move on to the next milestone review in
the fall of 2008. At this time we are on track for NSF construction
start in FY 2011. Long lead sub-component fabrication has begun (such
as the $21M primary mirror), with private funding.
Q2. You testified that ``with LSST, one sees each one of these
asteroids 100 to 200 times, even more. So, it is possible to derive a
pretty good orbit for those, and distinguish them from the
background.'' What is the level of accuracy in NEO orbits that you
estimate would be possible with LSST? What implications, if any, would
this have for further orbital determination from planetary radar
facilities.
A2. In very general terms, the orbits from a single apparition set of
observations will be good enough for the NEO to be predicted and
located again any time it comes within range for the next several
decades, and the path can be predicted well enough to rule out any
future impact with the Earth for many decades to come, for the vast
majority (over 99 percent) of detected objects. However, there will be,
as there are now (e.g., the asteroid Apophis) cases where the optical
position data will be unable to rule out a future impact, and radar
facilities will be key assets for providing the observations needed to
rule out (or in, if we should be unlucky) future impacts for a small
number of cases. It can be expected that radar will continue to be
needed for a similar number of key observations in the future as it has
been in the past. Radar however cannot be used to survey the sky and
discover PHAs.
Questions submitted by Representative Tom Feeney
Q1. NASA's NEO report, delivered this March, provides several options
for meeting the goal of achieving 90 percent detection, tracking and
characterization of Potentially Hazardous Objects, and the report
establishes a clear relationship between resources invested and the
time needed to achieve 90 percent coverage. In essence, the report
shows that for an additional investment of approximately $536 million,
we could buy-down a decade of time to complete the survey. In your
view, is that additional investment necessary? Does the threat posed by
PHOs compel faster completion of the survey?
A1. One can hasten the survey to some degree with greater expenditure
on other complementary systems. However, there is a natural limit to
the minimum time that a survey can be completed to, say 90 percent,
which results from the fact that the asteroids move in orbits with
orbital periods of several years and often spend years at a time simply
out of the range of visibility from the Earth, or in some cases, even
from space. Thus, it is not possible with any detection system, no
matter how capable, to see all PHAs instantly, or even in a very short
time. The fundamental ``time constant'' for surveying is the timescale
of the orbit periods, that is, a few years. This amounts to the
``exponential time constant'' of a survey, and to reach 90 percent
takes a factor of two or three times the time constant, or about a
decade. Speeding things up from a decade requires near-Herculean
effort, for example putting a rather large telescope in a ``Venus-
like'' orbit, and even that reduces the time by only a few years. On
the other hand, time is our friend if we consider going a little more
slowly. Thus, backing off to a capable ground-based survey can reach
the goal set by Congress in only a few years longer than the 15 years
(from 2005) originally mandated by the Congress. It is more important
not to back off in the completeness level than in the time to achieve
it. I share the opinion of many in the NEA community that it is key to
get started now on a capable survey, but that it is not worth the
investment in a space facility to shorten the survey by a few years.
Q2. What are the most difficult types of NEOs to detect? Is there, for
instance, a portion of the sky that won't be covered by ground-based
facilities? Are there certain types of orbits that make it difficult to
detect and track asteroids and comets?
A2. Some NEOs are more difficult to detect than others, although
``blind spots'' in the sky not covered by the surveys is not the cause
of that difference. Any asteroid in an orbit that can hit the Earth
will spend some time in the visible part of the sky, so it is only a
matter of time before it passes into a visible region. The goal of the
survey is to find PHAs decades before an impact, not on final approach
only days before an impact. In the latter case, yes, an impactor can
arrive from the direction of the sun and not be seen until it hits. But
in the former case, during a close (but not impacting) pass by the
Earth, if it comes from the direction of the sun it will become visible
after closest approach as it moves away, and vice versa if it comes
from outside moving in. Thus, in either case, it will be seen by the
survey and duly cataloged for any future approaches or impact paths.
The difficulty of finding PHAs is therefore mostly a matter of how
often an asteroid passes within range of the survey. One class that is
difficult are objects in very long orbits, similar to comets, that only
come in close to the Earth every decade or so. We simply have to wait
until they come around. Another group are resonant objects that have
orbit periods that are close to multiples (including 1.0) of the
Earth's orbit period. Imagine an asteroid with a period very near 5.0
years, which comes close to the Earth's orbit when the Earth is on the
other side of the sun. Every five years it is behind the sun, so we
can't see it. At other times it is far from the sun (and also the
Earth), so even when it is in the view range of the survey it is very
faint. Yet another group are asteroids with very nearly 1.0 year orbit
period. A number of these have been discovered which appear to ``loop''
the Earth in eccentric or inclined orbits. These objects drift away
from the Earth's vicinity after several annual loops, not to return
again for decades or longer, after they lose or gain one full circuit
of the sun relative to the Earth. There are undoubtedly other such
objects currently parked on the opposite side of the Earth's orbit that
will slowly drift into near-Earth space, and could be an impact hazard,
but we cannot find them from the Earth until after they move out from
behind the sun. Nevertheless, an Earth-based survey would find them
years before any possible impact. One can find them sooner with a
space-based survey in a different heliocentric orbit (say near Venus),
but is it worth it? It is improbable that there is even one object as
large as one km in diameter, and maybe only a few larger than 140m, in
such orbits, so the value of taking the extra effort to find them is
questionable.
Finally, comets are intrinsically difficult to track, due to the
non-gravitational forces of the gasses being emitted. Thus, it would be
impossible to predict an impact with certainty very long in advance
even if we found a rare comet on a potentially collision course. And of
course the long-period comets come around less than once in a lifetime,
so new ones never seen before keep coming. Finding and cataloging
comets far in advance of an impact is thus not possible with today's
technology or any foreseeable technology.
Q3. Once the LSST and Pan-STARRS telescopes are operating, and surveys
for PHOs that are 140 meters or larger has commenced, what is the
business and public safety case for expanding the search to detect and
track smaller PHOs--for instance, down to a size of 50 meters? What are
the cost and schedule implications?
A3. In my response to question 1 above, one can see that there is a
clear diminishing return in value for cost of ever larger surveys of
ever smaller PHAs. See also the NASA report on the feasibility of
extending the search for near-Earth objects to smaller limiting
diameters: http://neo.jpl.nasa.gov/neo/report.html The first generation
``Spaceguard'' survey has reduced the impact risk from about 1,000
casualties per year to about 100 per year, at a cost of a few tens of
millions of dollars. This is certainly quite good value returned. The
next generation survey, to 140 meter diameter, should reduce risk by
another 90 casualties per year, at a cost of some hundreds of millions
of dollars. The cost/benefit ratio of such a survey appears to be in a
justifiable range that is worthy of policy consideration. A further
step, say to 50 meter diameter, would seem on the face of it to be
beyond the range of what could be justified on a cost/benefit basis. In
terms of cost and schedule, we do not possess the technology at present
to catalog 50 meter objects at large enough distances to find a large
fraction of them in, say, ten years at reasonable cost. However, the
same systems that find 90 percent of objects larger than 140 meters in
ten years will find 90 percent of objects to 50 meters diameter over a
longer time, of order of a human lifetime. So by about 2100, we will
eventually find nearly every PHA that can make it through the
atmosphere. That is sooner than the odds of the next one hitting the
Earth, so the level of patrolling of the skies contemplated by LSST
will very likely find the next impacting object before it finds us.
Q4. One deflection solution, suggested by NASA, is to detonate a
nuclear device in the vicinity of a PHO. What are the advantages and
disadvantages of using this approach? What circumstances would argue
against using a nuclear device in lieu of alternative approaches?
A4. Many of the implications of this question are matters of policy
rather than science. However, there are technical aspects. My comments
are based on the 2006 NASA NEO workshop in Vail. A major disadvantage
of nuclear approaches is that we do not know how efficient a nuclear
standoff explosion might be, or if it would disrupt the body into
fragments still largely traveling on the same path, or if it would push
it aside, as proposed. Thus, one cannot know in advance whether a
standoff explosion would be effective, or even if shown to be effective
in a test case, whether it would be equally effective on another
asteroid--the one actually coming our way. The same uncertainty
accompanies the ``kinetic impactor'' method of deflection, but it is
vastly more politically acceptable to conduct impact experiments, such
as the ``Deep Impact'' comet mission, than it would be to conduct
nuclear tests in space. Furthermore, the most likely scenario we may be
faced with is the case of an object that may, but with less than 100
percent certainty, be on a collision course, but we will not know for
sure until after the optimum time to take action. In such a case, it
would be politically difficult, as well as strategically dangerous, to
take action with nuclear explosions when such action might not be
needed at all, and even if so could produce unpredictable results. Much
more prudent would be an approach that is more controllable and can be
monitored for effect, such as the proposed combination of a rendezvous
vehicle that can monitor the effect of a kinetic impactor and serve as
a ``gravity tractor'' as needed for fine-tuning the deflection. In any
case, one should weigh the benefit of developing deflection plans in
advance of a discovered need.
Questions submitted by Representative Dana Rohrabacher
Q1. With regard to NASA's Spaceguard program, what changes, if any, do
you recommend to make the program more effective? In your view, is
further legislation required from Congress to implement needed changes?
A1. The Pan-STARRS and LSST surveys are planned to use somewhat
different search patterns, and object identification algorithms, than
those used by the current surveys. Whether it would be cost-effective
to implement changes of this nature in the current surveys is
questionable when they will become obsolete in terms of depth of survey
very soon anyway. It would certainly be short-sighted to shut down the
current surveys in anticipation of the next generation before those
surveys come on line at some decent level, but NASA, and the Congress,
should be prepared to make the transition to the next generation as
soon as it is possible to do so. To retire the risk from Potentially
Hazardous Asteroids, Congress could do two things: (1) assure that a
ground-based survey capable of achieving 90 percent completeness for
PHAs of larger than 140 meters gets started as soon as possible and,
(2) assure availability of the Arecibo radar (since that will continue
to be an occasionally essential asset into the next generation of
surveys.)
Q2. How important do you consider characterization in the overall NEO
issue priorities?
A2. Physical observations, to measure sizes, shapes, spins, densities,
mineralogy, and so forth of discovered asteroids is of very high
scientific interest, but is of secondary importance as far as the
impact hazard issue is concerned. The statistical characterization
method has serious limitations when a robust characterization of that
particular asteroid with our name on it is required. Characterizing a
statistically meaningful subset of discovered objects is necessary in
order to understand the population (for example, to even know what
fraction of objects larger than a given size have been discovered), but
this can be done from observations of a small fraction of the
discovered population that happens to be most easily observable, thus
it is not necessary to have a large commitment of telescopes as large
or even larger than the survey instruments, as has sometimes been
claimed. This is not to say that no commitment is needed, but it can be
satisfied with existing facilities currently engaged in asteroid
observations.
Q3. What capabilities are required for a comprehensive deflection
campaign?
A3. This is outside the purview of the LSST project. While R&D is
needed, my personal opinion is that deployment of deflection hardware
should wait until a demonstrated need is discovered.
Q4. What is your estimate on the number of undiscovered asteroids in
the 140 meter and above range? Describe the potential damage that an
asteroid in the 140 meter range could cause striking an ocean within,
say, 500 miles from a U.S. coast.
A4. It is estimated that there are about 20,000 NEAs larger than 140
meter in diameter, and presently, there are somewhat over 3,500 known,
leaving about 17,000 undiscovered. In terms of Potentially Hazardous
Asteroids, there are approximately 4,000 total estimated, and about 600
known. A 140 meter diameter asteroid striking the ocean 500 miles (800
km) from shore might produce a tsunami wave a meter or two in height as
it approaches the shore. The ``run up'' amplification depends a great
deal on the off-shore depth profile, but might be a factor of two or
three, to a height of five meters or so. Such a wave might run inland a
km or so, depending on the flatness of the land on shore. The effects
of such an impact tsunami could be comparable to a major hurricane, and
the chance that the impact would be at a particularly vulnerable
location rather than somewhere else is comparable to that for a
hurricane.
Q5. Asteroids are more easily detected in the infrared spectrum. An
asset such as the WISE satellite has an effective capability for
searching for NEO's infrared output. Is WISE being tasked for this
role? What other infrared detection devices can or will be used to
detect NEOs?
A5. Infrared technology is not yet mature enough to be competitive with
optical (reflected sunlight) surveying. From the ground, the highly
emissive and absorbing atmosphere reduces thermal IR sensitivity to
less than that of optical, regardless of detector technology. From
space, IR has a modest theoretical advantage, less than one might
suppose because the resolution of a given aperture telescope in the
thermal IR is about twenty times less than at visible wavelengths, and
the background level of sky brightness and confusing sources, after
allowing for the reduced resolution, is substantial. There are some
technological problems: detector arrays are not yet as large as those
for optical wavelengths, to operate efficiently they need to be cooled
to the limit (or beyond) of passive cooling systems, and with many
images each with billions of pixels there would be on-board computation
challenges.
While WISE will survey the entire sky and, indeed, detect many
asteroids, there are a number of reasons that it will not be capable of
making a substantial contribution to the PHA survey. First, the WISE
survey strategy does not have a cadence that is tuned to discovering
and cataloging moving objects. Moreover, with only a six-month mission,
many PHAs will be out of range and completely unobservable during the
brief period of mission operations. Finally, its modest instrument (0.4
meter aperture, 0.8 degree field of view) is not well-suited for this
purpose. However, WISE will make great strides in the realm of asteroid
characterization. The four separate IR band passes will allow the
characterization of a large number of asteroids, some of which may not
be actually discovered until later. This information, combined with
optical catalogs, such as the Sloan Digital Sky Survey, will enable
subsequent PHA surveys such as LSST to make good statistical inferences
about the makeup and size of new discoveries. WISE will detect a lot of
asteroids, but is not capable of replacing even present optical survey
systems, let alone systems like Pan-STARRS or LSST, even if re-tasked
solely to the NEA survey. The advance of IR technology should be
monitored for its potential to contribute to NEA surveys, but at
present it does not appear to be mature enough to contemplate changing
from ground-based optical surveys to space-based IR surveys.
Answers to Post-Hearing Questions
Responses by Russell ``Rusty'' L. Schweickart, Chairman and Founder,
B612 Foundation
Questions submitted by Chairman Mark Udall
Q1. How well understood are the potential approaches to deflecting
asteroids? What is the confidence level in the technologies that would
be required? What information is needed to assess the various
approaches, and how will decisions be made on which mitigation strategy
to take?
A1. The basic elements of an asteroid deflection are quite well
understood. One must alter the orbit of the asteroid to 1) miss a
direct Earth impact, and 2) avoid passing through any of the hundreds
of return keyholes as the asteroid passes by the Earth. The
technologies which have the required capability for the first of these
objectives are kinetic impact (KI) and nuclear stand-off explosion. KI
is essentially running into the asteroid in a specific direction with a
specific velocity, similar to what was done in 2005 by the Deep Impact
spacecraft running into comet Tempel 1. A stand-off nuclear explosion
in space has never been done but on a theoretical basis should work.
Both techniques can be characterized as strong but imprecise. Therefore
essentially all asteroids which might threaten impact can be deflected
from a primary impact (98-99 percent can be deflected using KI).
However such a deflection has no possibility of insuring that the
asteroid will not pass through any of hundreds of return keyholes
resulting in a certain impact within several years. Therefore a
precision deflection capability using the gravitational tractor (GT)
concept (or other if any become available) is needed to immediately
follow-up the imprecise primary deflection to insure that no keyhole
passage is permitted.
There need to be detailed analytic assessments and simulations
performed on all three techniques. The KI and GT techniques should
ultimately be flight tested on a real (but non-threatening) asteroid to
fully validate a deflection campaign. I do not recommend demonstrating
the nuclear explosion concept, although simulations could, and should
be run.
An actual deflection decision is virtually independent of the
technology. A deflection campaign would require two coordinated
missions, first a transponder/gravity tractor (t/GT) mission to
precisely pin down the asteroid orbit and confirm a pending impact. If
confirmed the t/GT would observe the subsequent KI impact from a safe
distance, then pull in close to the asteroid to 1) confirm a successful
primary deflection, and 2) determine whether or not the asteroid is
headed for a return keyhole. In the unlikely case that the asteroid is
headed for a keyhole the t/GT would then be employed to make a small
but precise modification in the asteroid's new orbit to assure the
asteroid misses the keyhole. This sequence is the only way, using
existing technology, to guarantee a successful deflection. In the
extremely improbable event (probability of occurrence once per 100,000+
years) that the asteroid at issue is too large for a KI deflection, a
nuclear stand-off explosion would be needed as a substitute. The
precision component (t/GT) would still be essential to the success of
the deflection campaign.
The decision to deflect, per se, would of necessity be an
international decision due to the inherent shifting of risk from one
geographic region to another during any deflection. The Association of
Space Explorers (ASE) is working on the deflection decision process in
cooperation with the United Nations. While the action will of necessity
be the responsibility of one or more space-faring nations, the decision
process will involve many nations since the uncertainty in the impact
point and the shifting of risk during any deflection will involve
nations across the planet.
Q2. How mature are the non-nuclear versus the nuclear technologies for
deflecting an asteroid?
Q2a. What should the priorities be in further developing those
technologies?
A2a. The non-nuclear (KI) technology is a flight proven technique
having been used (albeit for different purposes) during the Deep Impact
mission of July 4, 2005. The primary difference is that comet Tempel-1
(the target of the Deep Impact spacecraft) was significantly larger
than those asteroids likely to require deflection. Furthermore there is
an unknown (likely small) possibility of fragmentation of the asteroid.
Finally the ``momentum multiplier,'' the degree to which the ejection
of debris from the kinetic impact multiplies the effectiveness of the
impact, is highly variable and uncertain. The last two factors can, and
should, be validated by an actual demonstration mission.
The nuclear stand-off explosion is entirely theoretical. While
terrestrial weapons effects analysis is a highly developed and
sophisticated field of knowledge the use of nuclear explosions in space
is not well understood and cannot, without modification of existing
treaties, be tested. Proponents of the use of nuclear explosions
generally feel very confident in their computer models, but atmospheric
and vacuum explosions are very different from one another. Additionally
the concerns mentioned above re KI also apply to the nuclear option,
i.e., the possibility of fragmentation and the uncertainty of the
``multiplier'' effect. The primary difference in eliminating these
uncertainties is that there is no impediment to testing KI in a
demonstration mission whereas demonstrating a nuclear stand-off in an
actual mission would be a major international political challenge, not
to mention arguably a treaty violation.
The gravity tractor (GT) is not in a ``versus'' situation, being a
necessary component of any deflection campaign, nuclear or non-nuclear.
In terms of technology maturity the primary challenge for the GT is
engineering the control and guidance software for the ``towing''
maneuver. Engineering simulations of the GT are about to get underway
and testing should be done in an actual flight demonstration. A
slightly modified Don Quixote mission (a NEO deflection mission
considered by the European Space Agency) could simultaneously
demonstrate both the KI and t/GT concepts.
Priority should clearly be given to developing and testing the KI
and t/GT concepts since they are the most likely to be called on for
deflection. Only one to two percent of potential deflection challenges
would require a nuclear option and that percentage will drop
essentially to zero as the revised search program is executed over the
next 15-20 years.
Q3. What do you see as the most important next step in advancing our
understanding of deflection approaches?
A3. Testing and demonstrating both the kinetic impact (KI) and gravity
tractor (t/GT) concepts. As mentioned above a slight modification of
ESA's Don Quixote mission could fully validate both components of a
deflection campaign in a single program for a total cost of between
$500M and $1B dollars. In a cooperative program with ESA, NASA's share
of this would be comparable to the cost of an average low-cost
scientific mission.
Q4. What do you think would be the most appropriate next steps in
addressing the governance issues discussed at the hearing?
A4. Step 1 would be to assign responsibility to NASA for 1) analyzing
and developing NEO impact warning concepts, and 2) for developing and
testing NEO deflection technology.
Search is important, without question. However someone now needs to
be working through the complex issues of what we do when we discover a
NEO which ``has our address'' on it. . . or, more likely appears to
have our address on it. With the exception of flight testing the
deflection concepts, these actions require very little money; the task
is primarily to conceptually work through the complex issues involved.
Step 2 would be to address the larger question of overall
responsibility for handling this devastating but preventable natural
hazard. This issue is particularly challenging in that unprecedented
levels of destruction are at issue and in the process of eliminating
the risk of an impact for everyone certain nations will of necessity
have to accept a temporary increase in risk to their populations. Such
a collective international decision will require considerable
diplomatic efforts involving not only cost sharing, but also liability,
indemnification, oversight and other sensitive considerations. While
the technical aspects of warning and deflection will inform many of
these considerations the primary challenge embedded here is national
and international policy.
In addressing this it would seem that no single Congressional
committee has appropriate jurisdiction. Therefore at the outset the
Congress and the Administration would benefit from the issue being
considered in depth by an appropriate highly-regarded professional
organization, such as the National Academies.
Questions submitted by Representative Tom Feeney
Q1. NASA's NEO Report, delivered this March, provides several options
for meeting the goal of achieving 90 percent detection, tracking and
characterization of Potentially Hazardous Objects, and the report
establishes a clear relationship between resources invested and the
time needed to achieve 90 percent coverage. In essence the report shows
that for an additional investment of approximately $536 million, we
could buy-down a decade of time to complete the survey. In your view,
is that additional investment necessary? Does the threat posed by PHOs
compel faster completion of the survey?
A1. This is an excellent public policy question, not a technical one. I
believe that the following are considerations which should be taken
into account in addressing the issue.
1. A growing segment of the general public is aware of the NEO
threat. A smaller, but also growing segment of the public is
aware that we have the technology today to not only warn us of
a pending impact but also to prevent a devastating impact. Over
the next decade, under any circumstances, there will be a
number of what will be reported in the press as ``close
calls.'' There will also likely be several, perhaps even
hundreds, of NEOs that will appear to be threatening and will
be reported (and misreported) by the public media. The issue,
and its ``solution,'' will become widely known to the public.
2. A widely stated fact is that ``If we know about them, we
can do something about it. The ones we need to worry about are
the ones we don't know about.'' The public will come to know
that the survey could be accelerated by 10 years at the cost of
foregoing a single scientific satellite, or less (see comment
below). Alternatively adding $500M to the NASA budget over 5-7
years would suffice.
3. 2008 is the 100th anniversary of the ``Tunguska Event.''
There will be a great deal of publicity about this and many
legitimate and not so legitimate presentations and discussions.
4. Every hurricane, earthquake and tsunami which creates great
damage in the next decade will be another poster child for the
possibility of a NEO impact, especially if one occurs in
temporal proximity to a NEO ``near miss.''
5. From an ``objective'' perspective the NASA/JPL staff could
compute the probability of an impact of various sizes occurring
in the absence of the faster survey and compute the cost-
effectiveness of the additional $536M of ``insurance.'' (In
rough terms, using Apophis as an example, the cost of an impact
is approximately $400B. If the probability of an Apophis impact
(and its unfound cohorts) not being found is one in 1000 then
the actuarial value of finding it in time to prevent the impact
is $400M. Such an actuarial analysis could be performed).
Note: Dr. J. Anthony Tyson, Director of the LSST, testified at the
hearing that if NASA were to fund 15 percent of the LSST costs it would
effectively have at its disposal, for $125M, a dedicated LSST and be
able to meet the Congressional 140 meter goal within 12 years from LSST
by 2026.
Q2. What are the most difficult types of NEOs to detect? Is there, for
instance, a portion of the sky that won't be covered by ground-based
facilities? Are there certain types of orbits that make it difficult to
detect and track asteroids and comets?
A2. There are two factors which are critical; size and type of orbit.
Small NEOs can only be seen when they are very close to the Earth
compared with larger NEOs. There are also many more small NEOs than
large ones (e.g., 1,000 NEOs larger than one km in diameter vs. 40,000
NEOs larger than 140 meters diameter, and 800,000 at 40 meters and
larger.) and therefore the vast majority of unfound NEOs are at the
smallest end of the spectrum of those which can do damage on the
Earth's surface.
The second factor is the orbit size. Those NEOs whose orbits are
smaller than the Earth's, i.e., whose orbits lie primarily inside the
Earth's orbit, spend most of their time with a ``look angle'' too close
to the Sun and its glare to be seen by optical telescopes. They are
typically seen for a month or two for several years in succession,
followed by many years when they cannot be seen at all. These NEOs are
classified as Atens. When an Aten is also small the two issues compound
such that a 40-140 meter diameter object may be seen only once or twice
in a decade. Obtaining an accurate orbit is therefore quite difficult
for these objects.
As pointed out in the NASA report, a space-based telescope placed
in a Venus-like orbit would be able to look outward (i.e., away from
the Sun) and both discover and track these Atens which are challenging
to observe from the Earth's surface.
Comets (long period comets) orbit the Sun in very large orbits
which extend beyond the orbit of Jupiter. They are only detected when
they approach the Sun within the orbit of Jupiter and begin to out-gas
due to gradual heating. From detection to the time they cross the
Earth's orbit is typically only several months. This is inadequate time
to mount a deflection and they are generally not considered objects
from which we can protect ourselves. Happily they are also one percent
of the asteroid problem and are therefore (currently) disregarded.
Q3. Once the LSST and Pan-STARRS telescopes are operating, and surveys
for PHOs that are 140 meters or larger has commenced, what is the
business and public safety case for expanding the search to detect and
track smaller PHOs--for instance, down to a size of 50 meters? What are
the cost and schedule implications?
A3. As regards ``the business case'' (the potential for ``mining''
asteroids) essentially the only issue is the cost to get to the
asteroid. This depends entirely on the specific orbit, with those in
Earth-like orbits being the least costly to target. Even a 40 meter
diameter asteroid weighs in at 100,000 metric tons; a great deal of
potentially useful resource for development. Therefore since there are
many more small asteroids than large the most promising targets for
resource utilization will be found among this population.
Public safety is at issue any time an asteroid impacting the Earth
can cause significant damage at the surface. The Earth's atmosphere
protects us from NEOs smaller than 30-40 meters. Those in the vicinity
of 40-100 meters may not reach the surface but will explode with such
energy in the lower atmosphere that they create devastation at the
surface even without reaching it per se. At sizes larger than 100-150
meters they reach the surface of the Earth substantially intact causing
even greater damage and potentially tsunamis if they impact the ocean.
It is clearly a policy judgment but I (representing the Association
of Space Explorers) consider a Tunguska-like impact to be approximately
the threshold size at which public demand would mandate a deflection
effort (this assumes that the NEO is known in advance and projected to
impact). Had the Tunguska asteroid (approximately 45 meters in
diameter, exploding with five megatons of energy or 333 Hiroshima
bombs) exploded over a city instead of the middle of a Siberian forest
it would likely have killed everyone in the city. It therefore seems
prudent, from a public safety consideration, to ultimately extend the
search down to this (or some equivalent) threshold limit.
What needs to be recognized is that in the process of reaching the
goal of 90 percent of the population of NEOs 140 meters and larger we
will also discover approximately 40-50 percent of the NEOs 50 meters
and larger. Without any further investment in larger telescopes an
additional two decades (i.e., 2040) of search (which will be done in
any case in order to monitor the larger NEOs) will ultimately extend
this figure to near 90 percent. If one chooses to reach the 90 percent
discovery level for 50 meter objects earlier (say by 2030) then either
larger ground based telescopes or a modest ( 1 meter) space telescope
in Venus-like orbit would have to be employed. The life cycle cost of
this would approximate $1B according to NASA's estimation in their NEO
Report to Congress.
Q4. One deflection solution, suggested by NASA, is to detonate a
nuclear device in the vicinity of a PHO. What are the advantages and
disadvantages of using this approach? What circumstances would argue
against using a nuclear device in lieu of alternative approaches?
A4. The only advantage of using a nuclear device over a kinetic
impactor (KI) is in those rare instances where the total impulse
required to deflect the NEO at issue is greater than can be provided by
the KI. Assuming adequate warning (i.e., 15-20 years) this threshold is
reached at approximately a 400 meter diameter NEO. An object of this
size is statistically encountered only once every 100,000 years. At the
current time we have discovered about 40 percent of NEOs this size and
the probability that any of these will impact Earth in the next 100
years is zero. By completion of the new survey (140 meters) we will
have discovered about 95 percent of the 400 meter NEOs. Assuming that
none of them is about to strike the Earth (very highly likely) it is
only the remaining five percent still unknown which would pose a threat
necessitating the use of a nuclear device for deflection. The
probability of one of these residual five percent striking Earth is
once per 2,000,000 years.
The other, also very unlikely circumstance in which a nuclear
device would be required is if, in the next few decades we discover a
NEO of almost any size which is predicted to impact within 5-10 years
from discovery. Since the probability of the smallest objects of
concern (therefore the most populous and most likely to impact) is once
in 1,000 years, the probability of encountering one of these in the
next 10 years is one in 10,000. This small number is further reduced by
the fact that at the completion of the 140 meter survey we will have
discovered only (say) 50 percent of the 50 meter objects and therefore
there would be only a 50 percent chance that we would have discovered
such an impactor before it hit.
The bottom line is that non-nuclear means are able to handle 98-99
percent of the current population of dangerous asteroids (those above
the threshold mentioned above) and this will grow to well over 99.9
percent within the next two decades as we discover most of the
remaining NEOs which would require nuclear means.
But why not (NASA asks) use nuclear if it will work? Because the
entire issue of NEO deflection is ultimately a collective (i.e.,
international) decision and the world has clearly and unequivocally
stated in treaties and elsewhere that it wants to keep nuclear weapons
out of space. Can the U.S. act unilaterally? Of course. Is this wise?
Absolutely not. Where non-nuclear means are adequate to do the job
there is no objective reason for considering nuclear explosives.
From the technical perspective the use of a nuclear device will
also be highly unpredictable. The potential for fragmenting the NEO
will be extremely difficult to rule out given the very unlikely case
that an actual flight demonstration on an asteroid will be available.
Furthermore the total impulse imparted to the NEO will be highly
uncertain (as will be that of the kinetic impactor) and unlike the
kinetic impactor which is easily tested, this uncertainty will remain.
In any circumstance both the kinetic impactor and the nuclear stand-off
explosion (or any other impulsive deflection technique) will not
provide the precise orbit change needed to insure that the NEO will not
pass through a return keyhole after the primary deflection maneuver.
Therefore a deflection campaign must of necessity include the weak but
precise deflection capability of a gravity tractor (GT) or other
precision deflection technique to ``trim'' or slightly adjust the
primary deflection in the event that it is headed for a keyhole post-
primary deflection.
In summary; those circumstances requiring the strength of a nuclear
deflection are extremely improbable (and will become much less probable
over time) and, given international treaties and world opinion against
nuclear explosives in space the sufficiency of non-nuclear means will
be the option of choice.
Questions submitted by Representative Dana Rohrabacher
Q1. With regard to NASA's Spaceguard program, what changes, if any, do
you recommend to make the program more effective? In your view, is
further legislation required from Congress to implement needed changes?
A1. Reading the question in the narrow sense, i.e., the Spaceguard
Survey per se, I would emphasize recommendation #1 in my written
testimony that the Congress, whether through Authorization or
Appropriations, should require that NASA comply with the law and both
recommend and initiate a search program (and supporting budget) to meet
the 140 meter goal. Whether it takes 15 years or 17 years is far less
important than that a specific program be committed to and initiated.
Reading the question in its broader sense, i.e., the Spaceguard
Survey as the overall initiative to protect the Earth from asteroid
impacts, I would call on the Congress to expand NASA's current limited
activities to include 1) developing a recommended NEO impact warning
concept, and 2) developing and testing NEO deflection technology.
(These are contained as recommendations #3 & 4 in my written
testimony.) Not only is it important that we move ahead regarding the
issue of ``what do we do when we find one with our address on it?'' but
by systematically thinking through the issues involved in warning and
mitigation, the search program per se will begin to focus on the most
critical information needed rather than simply meeting a somewhat
abstract numerical quota.
One further observation here; under any circumstance the discovery
rate of NEOs will dramatically increase in the immediate future due to
the introduction of Pan-STARRS and LSST into the search process. There
is no doubt whatever that given the considerable expansion in the
number of NEOs discovered we will find many that will appear to
threaten impact with Earth. If, by way of illustration, the current
discovery rate of NEOs that appears to threaten impact is one per year,
then even without any further commitment by NASA, that rate of
discovery of apparently threatening NEOs will rise to 30 or more per
year over the next 5-7 years. This will, without question, get the
attention of the press and the public. Therefore it is critical that
specific action beyond the search program be underway to assure the
public that their safety is being responsibly attended to.
Q2. How important do you consider characterization in the overall NEO
issue priorities?
A2. Let me emphasize immediately that I am in the minority in what I am
about to say, even among my fellow NEO community peers. I believe that
my minority position is justified, having arguably thought through the
deflection issues more thoroughly than most of my compatriots.
I believe that characterization of NEOs, in the classic sense of
learning the specific technical characteristics of asteroids per se
(thermal, structural, mineralogical, and other descriptive
characteristics) is not a priority in regard to protecting Earth from
impacts. With respect to classical scientific values it is very
important; but protection of the Earth from impacts is a public safety
issue, not a scientific one.
The basis for this low priority is that the inherent performance of
the kinetic impact deflection concept (and nuclear explosion as well)
is highly uncertain and variable. The momentum imparted to a NEO by
crashing into it is determined more by the energy and the variable
nature of the impact geometry than by any knowledge that can be gained
through classical characterization efforts. Each NEO is unique and
likely non-homogeneous. The effect of an impact will vary depending on
the slope of the surface on which it happens to impact as well as on
the specific local structural characteristics. The rotation of the NEO,
whether it is hit a glancing blow, and whether there happens to be
buried ice or other volatiles at the specific impact site are also both
unknowable and likely highly variable.
Therefore the technical parameter beta (the ``momentum
multiplier'') has a wide range, usually approximated today as ranging
from two to 10 or more. This large uncertainty, even assuming heroic
characterization efforts, will never be reduced to a reliably
predictable single value. Therefore a kinetic impact or nuclear
explosion will always produce a range of predicted deflection results,
e.g., 3-20 Earth radii, or 2-15 Earth radii. It is this intrinsically
uncertain nature of the impulsive deflection techniques which risks
deflecting the NEO such that it will miss the Earth (good) but risk
passing through a return keyhole (bad). For this reason it will always
be necessary to have an observer spacecraft, with a transponder and
precision deflection capability (e.g., gravity tractor), standing by in
real time to both confirm the success of the primary deflection and
execute a precise adjustment to the deflection to avoid a future
keyhole passage and subsequent impact.
Given that the primary deflection will always have a degree of
uncertainty sufficient to risk passage through any of hundreds of
return keyholes, a precision orbit adjustment capability will always be
required. This statement will remain true regardless of any amount of
money spent on NEO characterization, given the many variables of a
kinetic impact or nuclear explosion having nothing to do with NEO
characteristics. So why spend the money when the inherent uncertainties
can (and must) be handled by the precision trim capability?
Conversely, if one is (and we should be) interested in the
potential for utilization of asteroidal resources at some future time,
then characterization of NEOs is very important indeed. This is,
however, classical science in its proper role and not public safety.
Q3. What capabilities are required for a comprehensive campaign?
A3. A comprehensive deflection campaign (for a ``direct'' NEO impact
threat) will consist of the following 5 steps;
1) The launch and rendezvous of a transponder equipped
spacecraft (t/GT) with the NEO,
2) The determination (confirmation) of a pending impact based
on the dramatically improved orbit determination,
3) The launch and impact of a kinetic impactor (KI),
4) The determination of the precise post-impact NEO orbit, and
5) A precise orbit adjustment (trim) maneuver if the NEO is
determined to be headed toward a return keyhole (t/GT).
Given that the primary deflection may place the NEO on a path
toward a return keyhole, a precision deflection capability will always
be necessary. Therefore since a gravity tractor (or other future
precision deflection technology becomes available) will also have a
transponder aboard the spacecraft for steps 1, 4, and 5 would logically
be a single transponder/gravity tractor (t/GT) combination.
If the threatening asteroid is being deflected not from a direct
impact but rather from a keyhole (with subsequent impact), then only
steps 1, 2, and 5 need be employed. An example of this situation is the
current Apophis case where, if in 2013 it is determined that the NEO is
indeed headed for the 7/6 keyhole in its 2029 close approach to Earth,
a t/GT mission alone can be utilized to affect the deflection (i.e.,
steps 1, 2 and 5 above.)
Q4. The need for a comprehensive potentially hazardous NEO program
seems to require expertise of several agencies. How do you suggest
coordination be handled?
A4. The primary technical expertise required for a comprehensive NEO
impact mitigation capability lies within NASA per se. The exception to
this is the remote possibility of encountering a NEO threat which
exceeds the capability of the kinetic impactor for primary deflection.
If it is deemed prudent to prepare for this unlikely eventuality then
NASA will need to coordinate with DOE regarding nuclear stand-off
deflection capabilities and requirements. This coordination can be done
in much the same manner as currently done when NASA utilizes nuclear
materials (e.g., RTGs) or as was done in the recently canceled
Prometheus program which utilized a nuclear reactor.
Q5. Describe some of the proposed mitigation techniques and their
trade offs.
A5. There are three techniques available with no new technological
developments required prior to use. In all three cases there is
significant engineering required. (Many neutral observers would
challenge these statements for the nuclear stand-off option, however I
will not challenge the advocates here.) These three divide into two
types; the impulsive (virtually instantaneous action) techniques of
kinetic impact (KI) and nuclear stand-off explosion, characterized by
significant total impulse capability but with a highly unpredictable
outcome, and the ``slow push'' technique (using NASA's term) of the
gravity tractor, characterized by a modest total impulse capability but
high precision and full controllability. Either of the impulsive
techniques would necessarily be used in concert with the latter to
insure a fully successful deflection.
The nuclear option has the disadvantages of both political
opposition, especially international, and technological uncertainties
which can never (in all likelihood) be tested prior to potential use.
The guidance and timing constraints to achieve a planned result in
addition to the possible fragmentation of the NEO are all significant
challenges which will persist until actual use is attempted. A further
leap of faith is taking at their word the nuclear effects experts who
claim that the behavior of a NEO exposed to a pulse of neutrons will
behave as the computer models predict. On the positive side the total
impulse available for altering the orbit of a NEO is potentially
greater than any other option.
The kinetic impact (KI) and gravity tractor (GT) technologies use
available and proven technology, albeit in both cases engineering
software needs to be developed and tested. Both techniques can, and
should, be fully tested and demonstrated. This should be done in the
near future to provide both official and public confidence prior to the
time that a threatening NEO is discovered. The KI concept could also
cause NEO fragmentation, but in this case it can be tested early and
inform operational design to provide confidence in actual use. The GT
concept is completely benign since it makes no contact with the NEO and
can easily be tested and its performance validated in the immediate
future.
There have been other deflection concepts proposed but all, in one
way or another, require advanced technology development, the resolution
of key unknown factors, or pose less cost effective solutions than
those currently available. All such techniques should be further
investigated and analyzed to support decisions on future technology
development and testing. None, however, should be considered to be
currently ready for deployment as are the three recommended above.
Q6. What is your assessment of the need for a nuclear capability?
A6. There is a very limited, near-term value in having a nuclear
capability conceptually available for NEO deflection. The need is very
limited, however, and a determination of the high cost and complexity
of further development of this technique must be judiciously weighed
against the very low probability of it being needed viz. non-nuclear
techniques.
Based on current analysis it appears that the KI technique can
provide the total impulse to deflect any NEO up to approximately 400
meters in diameter given 15-20 years of warning. Given that the
statistical frequency of a 400 meter NEO impacting Earth is about once
per 100,000 years the probability of needing to use nuclear deflection
is approximately .05 percent over the next 50 years. (I use 50 years on
the assumption that by that time more capable non-nuclear technologies
will be developed.) Further reducing this probability is the fact that
we have already discovered about 40 percent of the 400 meter NEOs and
none has any possibility of impacting Earth in the next 100 years. The
likelihood therefore drops to .03 percent based on the remaining 60
percent of yet to be discovered 400 meter NEOs. However based on
similar reasoning, by the completion of the new 140 meter search
program in 15 years the completion rate for 400 meter NEOs will
approximate 95 percent of the population reducing further the
probability of needing to use nuclear technology to about .004 percent.
Finally, for warning times exceeding 20 years or so any significant
development costs can await such warning and still be ready for
deployment if needed.
The missing element in the above paragraph is the similarly very
low probability that within the next 15 years a 400 meter or larger NEO
will be discovered with an impact date within 20 years, i.e., an
``immediate'' impact. In this instance only the extant nuclear
technology would be available for use. The probability of this
situation arising can be approximated based on the statistical impact
rate of 400 meter NEOs at once per 100,000 years. This is based on all
of the 400 meter NEOs being unknown. If we assume that it will take
approximately 20 years to discover ``all'' of the 400 meter NEOs then
the probability a 400 meter NEO impacting within the next 20 years is
one in 2,000 or .05 percent. However since we have already discovered
40 percent of the 400 meter NEOs and will reach about 95 percent within
the next 15 years, this probability is .03 percent now and will
diminish to .004 percent within 15-20 years.
The public policy question is then, what expense is justified in
investing specifically in preparing nuclear technology for use in
deflecting NEOs over the next 20 years with the probability of use
being about one in 10,000? Beyond that timeframe adequate warning time
will permit this investment if and when needed.
My personal opinion is that this investment is not justified, other
than perhaps some minor analytic studies.
Q7. Why, in your written testimony, do you state that the most
important question you have been asked by the Committee is ``What
governance structures need to be established to address potential NEO
threats?''
A7. From my work on this issue over the past six years it has become
evident to me that the most challenging aspect of protecting the Earth
from NEO impacts will be the decision-making process. Without
elaboration, ``we can know something is coming at us, and we can have
something to do about it, but unless we can make the decision to take
action, we will still end up like the dinosaurs.'' Clearly this is an
overly dramatic statement since the likelihood of being struck by a
small NEO which might devastate a city-sized area is 1000s of times
more likely than an extinction event. Nevertheless it clearly makes the
point that warning and deflection are simple compared with the world
making a coordinated decision to mount a NEO deflection campaign.
The key to understanding this claim lies in the use of the word
``world.'' Without going into too much technical detail the need for a
coordinated international decision arises from a combination of the
orbital mechanics of NEO impact and the need for those nations at risk,
and those nations placed at risk by the deflection itself, being
involved in the decision. Such up front questions as who pays?, will
there be indemnification for the deflecting entity?, will a deflection
be mounted at all or should we ``take the hit'' are all examples of the
need for international coordination.
What has not yet been generally recognized, even within the ``NEO
community'' is that in many (if not most) instances we will not be able
to wait until after it is certain that a NEO will impact before
launching a deflection campaign. The slow development of precise
knowledge of the NEO's orbit over time, combined with the episodic
nature of the collection of this knowledge assures that in many cases
the quality of our knowledge at the latest possible time a deflection
can be launched will require that we launch on probabilities of impact
less than one. In certain instances where the threat is a NEO headed
for a return keyhole prior to impact this launch decision may have to
be made with the probability of impact being as low as one in 100 or
even less.
These observations translate on the ground into challenging
international socio-political issues. When the probability of Earth
impact is less than one, all we know is that there is a risk corridor
extending completely across the Earth's surface, anywhere within which
the NEO could hit, if it is indeed headed for impact. This generally
narrow corridor (usually only 10s of kilometers wide) will cross many
national boundaries thereby limiting which countries are at risk of an
impact. However which specific country is destined for impact if a
deflection is not completed is unknown, and will generally remain so
until a transponder is brought into position at the NEO by the t/GT
spacecraft, the first element of a deflection campaign. Therefore a
decision to deflect will be of great interest to many but not all
countries (the risk corridor may cross as few as two to or as many as
10 or more countries). Will only these few countries called on to
decide on a deflection and bear the cost? Or is the world community as
a whole to debate the justification for sharing the cost? Will all, or
a few, or none provide indemnification for the designated deflection
entity? And by whom is the deflection to be performed and how will that
nation, or consortium be chosen? Etc., etc. This is only a small
sampling of the many difficult decisions that must be made in order to
initiate a NEO deflection. Can such a decision be made unilaterally? Of
course. However the implied liability and international furor should
such an act be executed will likely inhibit such action. Even if, e.g.,
the U.S. is threatened by such an impact and a unilateral action would
seem justified, the consequence of such action would be to place other
nations temporarily at risk in the process of deflecting the impact
away from the planet.
Clearly from this brief discussion it can be seen that the
deflection (or mitigation) decision process will involve very difficult
international political negotiations and trade-offs. The U.S. will have
to be represented and indeed may well play a dominant role in such
determinations. However the nature of the issues, while informed by
technical realities, is primarily socio-political and it is doubtful
that this responsibility would logically fall to NASA. Other logical
candidates, in my personal order of priority would be Department of
State, Department of Homeland Security, and Department of Defense.
How this assignment of responsibility is to be determined is the
public policy challenge to which I referred in my written testimony.
Notwithstanding the challenging nature of the issues I believe the
process of deciding this issue should start immediately given the
protracted debate which will soon be initiated within the United
Nations. This issue is currently on the UN Committee on Peaceful Uses
of Outer Space (COPUOS) agenda for 2009 and the Association of Space
Explorers is leading an international effort to draft a proposed UN
Program for Asteroid Threat Mitigation which will be presented in the
2009 COPUOS session. The U.S. needs to be prepared to not only
participate but lead in these discussions.
Q8. You've made a number of recommendations regarding actions that
should be taken by NASA and/or the Congress. Could you please estimate
the cost of implementing these recommendations?
A8. B612 Foundation has no credible capability to make such cost
estimates. Nevertheless, with this being said I will address the
question as best I can based on many years of working in the industry
and on analogous program experience. I will refer, without elaboration,
to the recommendations in my written testimony in addressing the
question.
Recommendation 1. ``. . .the Congress should again direct NASA in the
clearest language possible to comply with the law and recommend a
search program and supporting budget.''
The cost of complying with this recommendation is specifically
addressed in the NASA report to Congress. In addition, however, I
strongly advise consideration of the oral and written testimony
presented at the hearing by Dr. J. Anthony Tyson, Director of the LSST
Project. Dr. Tyson pointed out that NASA could, in fact, and contrary
to the NASA estimated cost in its report, obtain effectively a
dedicated LSST for 15 percent of the life cycle cost of the telescope
by contributing a total of $125M to the LSST Project.
Recommendation 2. ``. . .NASA should produce a supplement to its Report
to Congress based on new knowledge which has come to light since it
began its analysis.''
Given the baseline work already accomplished in the preparation and
delivery of the NASA NEO Report to Congress and the relatively few but
critical issues missed by NASA, it would seem that this supplement to
the Report could be accomplished at 15-25 percent of the cost of the
initial report. This is, however, purely a guess.
Recommendation 3. ``NASA should assign someone in its NEO Program to
the specific task of thinking through, analyzing and understanding the
NEO deflection challenge.''
The cost of implementing this recommendation is simply the cost of
one or possibly two additional FTEs at JPL.
Recommendation 4. ``NASA should validate a basic NEO deflection
capability through the execution of a demonstration mission.''
As described in my testimony a slight modification to ESA's
proposed Don Quixote program could validate the fundamental elements of
a full deflection campaign. Were NASA to undertake this full program on
its own the program would involve the design, launch and execution of
two relatively simple space missions in concert. The cost should
therefore approximate the cost of two typical scientific missions or
$600-800M.
If, as should certainly be seriously considered, NASA were to cost
share a cooperative program based on ESA's Don Quixote program with the
Europeans, its cost share should drop to below $400M.
Recommendation 5. ``. . .that the Congress expressly assign to NASA the
technical development elements of protecting the Earth from NEO impacts
as a public safety responsibility.''
This recommendation's costs are largely covered by the combination
of recommendations 3 & 4 above. The primary issue here is not any
specific action but rather a clear and unequivocal assignment of
responsibility. The development and/or testing of any new technology,
in addition to that in recommendation 4, would be handled and cost
justified on a case by case basis in future NASA budgets based on
justified need.
Recommendation 6. ``. . .that the Congress study the issue of overall
governmental responsibility for protection of the Earth from NEO
impacts, perhaps with the assistance of specialized policy entities,
and ultimately hold public hearings to engage a wide perspective on the
issue.''
The cost of this recommendation would be the cost of a directed
policy study (e.g., contracted to the National Academies by NASA) for
perhaps $1-2M plus the cost of Congressional hearings on the issue.
Q9. Can you give an example or two of why NASA needs to think about
deflection and not just about search and discovery?
A9. I interpret this question to mean not ``why NASA?'' but rather
``why does deflection and not just search and discovery need to be
thought about now?''
The answer is that within the next 15 years, assuming that the
Congressional 140 meter goal is responsibly addressed, we will be
adding hundreds of thousands of NEOs to the existing database. Of this
total approximately 150,000 of the NEOs discovered would, if they
threaten an Earth impact, be equivalent to the Tunguska impact or
larger and therefore be candidates for deflection. The remaining
hundreds of thousands would be small enough that the atmosphere would
prevent serious damage.
Working by similarity to the existing NEO database, of these
150,000 NEOs there will likely be 4500 or more ( 3.2 percent of the
total database) with a non-zero (i.e., some actual) probability of
Earth impact within the next 100 years. Of these 4500, if one or two
percent are of comparable or greater concern than Apophis and 2004 VD17
in the current database (both mentioned in the NASA Report) then there
will be on the order of 45-90 NEOs of what might be called elevated
concern by 2022. Of these NEOs it is highly likely that several, if not
many, will have potential impact dates which will challenge our
readiness to respond, i.e., by 2022 we will have dozens, and perhaps as
many as 100 NEOs in our database which appear to be threatening, and
many of them will have uncomfortably short response times.
Knowing this to be the situation (and the numbers are clearly only
approximate) from both statistics and similarity to our actual
experience to date, it would be irresponsible to wait until the
completion of the survey program and only then begin to develop a
response plan. Were we to do that it would be immediately clear that
our response capability would be delayed by perhaps 10 years or more.
The consequence of such a delay would be that for 10s of potential
impact threats, which we could have responded to if we had directed
NASA to ``think about deflection and not just search and discovery''
could not be prevented but only mitigated through evacuation, etc.
Is it likely that any of these NEOs of elevated concern would
actually impact? By definition, elevated concern means that they would
have an unusually high probability of impact. If this elevated impact
probability averaged one in 1,000 than in the example above the
probability of any of them being an actual impact would be 4.5-9
percent. This, as in most things NEO, is a public policy/public safety
call. But given the relatively low cost of being prepared I believe
that the public would be justifiably outraged if they were asked to
accept a five percent chance of an impact for 10 years which could have
been prevented by thinking ahead and allocating less than one half of
one percent of the NASA budget to being prepared.
Appendix 2:
----------
Additional Material for the Record
NASA Rebuttal to remarks made by Mr. Schweickart during the November 8,
2007, hearing regarding Near Earth Objects
The report on Near-Earth Objects NASA submitted to the Congress in
March 2007 explicitly addressed a keyhole scenario on page 22, scenario
A1. Figure 4 in this report shows that in any case where a small
momentum change is required to deflect a threat, such as with a
keyhole, the number of deflection options increases. The NASA report
does not agree with the characterization that ``primary'' and then
``potentially secondary'' deflections are required. Instead it finds
that, more generally, a series of missions will most likely always be
planned to ensure that a particular threat does not impact the Earth
with acceptable certainty. The study team also found that the options
analyzed in the study would be a toolkit from which a deflection
campaign could be designed, depending on the specifics of the threat
scenario. The NASA report does not characterize post-deflection
keyholes as a ``minefield.'' The report found that the likelihood of
diverting a threatening object by a well-designed deflection mission
into a keyhole to be very unlikely, and that even in this unlikely
occurrence, a follow-on mission would by design be ready to complete
the deflection. The report also does not indicate that this secondary
deflection, if necessary, would necessarily be best performed by a slow
push method.
Statement of The Planetary Society
in Support of Planetary Radar
at the Arecibo Observatory
PROTECTING THE EARTH
Less than a century ago, a near-Earth object (NEO) slammed into
Siberia, devastating 1,000 square miles. If it had struck just a few
hours earlier or later in a populated area, it could have killed
several hundred thousand people. NEOs pose a real and dangerous threat
to Earth.
In the past few years, we have been discovering, tracking, and
characterizing the comets and asteroids that travel through our
neighborhood of space. We have learned much--about near-misses, the
probability of collisions, the diversity of asteroid and comet physical
properties, and the effects of impacts in the past. We have even
learned that one asteroid, named Apophis, will pass closer to Earth in
22 years than our geosynchronous communications satellites, and its
trajectory has a small probability of taking it on a collision course
with Earth seven years after that.
Radar tracking is the only way to precisely know the probability of
impact, and the Arecibo telescope is the most powerful instrument for
the job, 20 times more sensitive for NEO radar tracking than any other
instrument in the world. Unfortunately, Arecibo is slated to be closed
by the National Science Foundation in a misguided attempt to free up
funding for new projects that do not yet exist.
Arecibo is the largest radio-telescope in the world. It has been,
and continues to be, an enormously productive scientific facility,
covering a broad range of science studies. While its contributions to
radio astronomy, ionospheric and atmospheric observations have proven
valuable for the past several decades, it is its planetary radar
capabilities that remain unique. Because of Arecibo's powerful one-
million watt transmitter, and the large 1,000-foot aperture, the
telescope is uniquely able to characterize potentially hazardous NEOs
and determine the danger they pose. Radar signals from this facility
are the only ones that can be regularly used for reaching and tracking
NEOs that may be coming close to Earth.
The cost of operating Arecibo is just a few million dollars per
year. Isn't the safety of Earth worth that?
In addition to tracking NEOs, Arecibo has returned other recent
important results from planetary radar, including the best physical
characterization of any potentially hazardous asteroid as large as a
kilometer, ultra precise determinations of Mercury's spin state that
reveal that planet to have a molten core, and the identification of
several binary asteroids in the near-Earth population.
Arecibo is caught in a bureaucratic argument. The Arecibo
Observatory is a National Science Foundation (NSF) operation, but they
consider the subject of NEOs and planetary radar to be in NASA's
bailiwick. NASA supports ground-based astronomy, and supported the
Arecibo radar for many years, but the agency now objects to picking up
the funding of what is currently an NSF program.
The House Science and Technology Committee has been the leading
government advocate for understanding the nature and possible threat
from objects (NEOs) that might impact the Earth. In the past, the
Committee has had to direct NASA to provide increased support to this
area. The Planetary Society has no position on whether this should be a
NSF program or a NASA program; but, we strongly feel that it should be
an American program with congressional support. We urge you to provide
such support to keep the Arecibo planetary radar operating.
The Planetary Society recently conducted a privately funded,
international competition to design a mission to tag the asteroid
Apophis, in case its Earth approach is close enough to require higher
accuracy tracking. The competition attracted thirty-seven proposals and
has generated much public interest.
The cost of a tagging mission to Apophis would be at least $100
million--and the only way to know if such a mission is necessary is to
refine the current estimate of Apophis' orbit with the powerful radar
tracking of a telescope like Arecibo. Avoiding one unnecessary tagging
mission would more than pay back any investment of funds to keep
Arecibo open. And if some object out there really is on a collision
course with Earth and we don't have the means to track it properly, the
price we would pay would be astronomical.
Thank you for your consideration.