[Congressional Record Volume 162, Number 146 (Tuesday, September 27, 2016)]
[Extensions of Remarks]
[Pages E1367-E1370]
From the Congressional Record Online through the Government Publishing Office [www.gpo.gov]




     COAST GUARD AND MARITIME TRANSPORTATION AMENDMENTS ACT OF 2016

                                 ______
                                 

                               speech of

                          HON. JOHN GARAMENDI

                             of california

                    in the house of representatives

                       Monday, September 26, 2016

  Mr. GARAMENDI. Mr. Speaker, I include in the Record the following 
materials:


 statement from dhs press secretary laura keehhner on the adoption of 
                     national backup system to gps

                           (February 7, 2008)

       Today the U.S. Department of Homeland Security will begin 
     implementing an independent national positioning, navigation 
     and timing system that complements the Global Positioning 
     System (GPS) in the event of an outage or disruption in 
     service.
       The enhanced Loran, or eLoran, system will be a land-based, 
     independent system and will mitigate any safety, security, or 
     economic effects of a GPS outage or disruption. GPS is a 
     satellite-based system widely used for positioning, 
     navigation, and timing. The eLoran system will be an enhanced 
     and modernized version of Loran-C, long used by mariners and 
     aviators and originally developed for civil marine use in 
     coastal areas.
       In addition to providing backup coverage, the signal 
     strength and penetration capability of eLoran will provide 
     support to first responders and other operators in 
     environments that GPS cannot support, such as under heavy 
     foliage, in some underground areas, and in dense high-rise 
     structures. The system will use modernized transmitting 
     stations and an upgraded network.
                                  ____



national pnt advisory board comments on jamming the global positioning 
 system--a national security threat: recent events and potential cures

                           (November 4, 2010)

       Summary: The United States is now critically dependent on 
     GPS. For example, cell phone towers, power grid 
     synchronization, new aircraft landing systems, and the future 
     FAA Air Traffic Control System (NEXGEN) cannot function 
     without it. Yet we find increasing incidents of deliberate or 
     inadvertent interference that render GPS inoperable for 
     critical infrastructure operations.
       Most alarming, the very recent web availability of small 
     GPS-Jammers suggests the problem will get worse. These so-
     called personal protection devices (PPDs) as well as other, 
     readily available, more powerful devices can deliberately jam 
     the Global Positioning System (GPS) signal over tens of 
     square miles. They also can be devastating to the other, new 
     foreign satellite navigation systems being deployed 
     worldwide.
       PPDs are illegal to operate, but many versions are 
     available (for as little as $30) from foreign manufacturers 
     over the Internet. The simplest models plug in to a cigarette 
     lighter and prevent all GPS reception within a line of sight 
     range of 5 to 10 miles. Current penalty for operation is 
     simply that the device is confiscated.
       We currently lack sufficient capabilities to locate and 
     mitigate GPS jamming. It literally took months to locate such 
     a device that was interfering with a new GPS-based landing 
     system being installed at Newark Airport, NJ.
       This paper provides background on satellite navigation and 
     describes the impact of these dangerous PPDs and other 
     disruptive radio frequency interference (Jamming). It also 
     suggests needed action and discusses technical measures 
     needed to harden GPS receivers against PPDs. The PNT Advisory 
     Board believes that countermeasures and actions must be 
     urgently developed.
       We strongly believe that the Executive Branch should 
     formally declare GPS a ``Critical Infrastructure.'' But that 
     is clearly only the first action and is by no means 
     sufficient. A multiple agency approach must be urgently 
     developed and executed.
       We must quickly develop and field systems that will rapidly 
     locate, mitigate and shutdown the interference. In addition, 
     laws are needed with the power to arrest and prosecute 
     deliberate offenders. [This would be similar to legal action 
     in response to the recent spate of laser attacks on pilots in 
     flight].
       Finally, we discuss the need for alternate navigation 
     systems such as eLoran or a backup system currently being 
     configured by the Federal Aviation Administration (FAA). 
     While the foreign GPS-equivalent systems may offer some help 
     against accidental interference, web sites are already 
     offering devices that will effectively shut down all 
     satellite-based radio navigation signals.
       Note that all of these actions and jamming countermeasures 
     tend to deter those who would deliberately interfere with the 
     signals.
       Specific Recommendations:
       1. National Focus.
       GPS should be formally declared critical infrastructure by 
     Executive Branch and managed as such by DHS.
       2. National Alerting and Pinpointing Interference 
     Locations.
       The National Executive Committee should establish and 
     sponsor a National GPS Interference Locating, Reporting, and 
     Elimination System; coordinating and expanding on the 
     resources of several Departments.
       3. Shutting Down and Prosecuting Interferers--
       Legal and Law Enforcement actions. The National Executive 
     Committee should examine whether or not they should sponsor 
     Legislation in Congress that addresses interference to GPS 
     that provides substantial fines and jail time for both 
     possession and use of GPS jammers.
       4. Hardening GPS Receivers and Antennas.
       Government should foster and help to stimulate 
     Manufacturers to speed up the development and offering of 
     interference resistant GPS receivers, especially for safety-
     of-life applications such as commercial air and maritime.
       5. Fund a National back-up capability to insure continuity 
     of PNT Operations.
       We strongly recommend that the previously announced 
     decision (to deploy eLoran as the primary Alternate PNT) 
     should be reconfirmed and quickly implemented.
       We support the FAA's efforts to provide Alternate PNT 
     options that can provide a robust backup to GPS and deter 
     malicious interference.


                      justification and rationale

     Background
       The utility of GPS continues to increase with an ever-
     broadening set of applications including military use, 
     aircraft guidance, harbor navigation, car navigation, 
     emergency response and personal navigation. It is now 
     estimated there are close to one billion users.
       GPS is a one-way system; it broadcasts line-of-sight 
     signals from a set of satellites in medium earth orbit (MEO) 
     to the earth-bound users carrying GPS receivers. The 
     satellites are approximately 12,000 miles above the 
     receivers. These satellites are placed at this altitude, so 
     that the coverage of an individual satellite is over one 
     third of the Earth's surface. With 30 satellites carefully 
     arranged in MEO, all earthbound users of GPS (with a clear 
     view of the sky) can see at least the prerequisite four 
     satellites to determine user location instantaneously. MEO is 
     used so that a reasonably sized constellation can aid 
     navigation worldwide. Lower orbits would require much larger 
     constellations for worldwide instantaneous coverage.

[[Page E1368]]

       For the reason described above, all GNSS satellites are 
     placed in medium earth orbit (MEO). However, because the 
     journey from MEO to the surface of the earth is 12,000 miles 
     long, the GNSS signals are weak. They have a received power 
     of only 10-16 Watts (equivalent to a Los Angeles 
     user receiving the light from 60 watt lightbulb in New York), 
     and can be easily overwhelmed by earth-sourced interfering 
     transmissions at the GPS frequency. As described below, this 
     radio frequency interference (RFI) can be: scheduled, 
     accidental, or malevolent.
     Critical Dependency on GPS
       Much of our infrastructure is critically dependent on 
     Positioning and Time from GPS. Two such dependencies 
     illustrate this.
       First, most telephone cell towers require GPS time to 
     insure they are synchronized and cooperate. Recent instances 
     of jamming in New York have rendered whole neighborhoods 
     without cell service including Emergency Service Providers.
       A Second example is the use of GPS for Aircraft Approach to 
     Landing Fields. These GPS-based systems are being deployed 
     and are particularly useful at airports where good 
     alternatives are not available such as at Aspen, CO and 
     Juneau, AK. There are now more FAA-sanctioned GPS approaches 
     than the older beam-steering type. (Over 2000 GPS 
     approaches). The value of these systems is enormous but the 
     vulnerability is not universally appreciated: it took over a 
     month to locate the deliberate small Jammer that was 
     periodically driven by Newark airport. This example is 
     particularly pertinent because the FAA's NextGen Air Traffic 
     Control System is critically dependent on GPS. Proliferated 
     Jammers would cripple the new system which is expected to 
     greatly reduce aircraft delays.
       Other Applications: GPS as a ``Stealth'' Utility. GPS has 
     been aptly called the Stealth Utility. There are literally 
     100s of additional application examples. Some are safety-of-
     life (e.g., air and marine), some are startling productivity 
     improvements (e.g., agriculture) and some are simply 
     convenience or recreation (e.g., car navigation). It is now 
     estimated that there are close to 1 Billion GPS receivers 
     worldwide.
     The GPS Jamming Threat
       Scheduled RFI is probably the largest cause of GPS outages 
     today. The military testing of GPS jamming causes these 
     outages. The events are localized (usually in the 
     Southwestern US), scheduled (during periods of light air 
     traffic), and approved/coordinated by the Federal Aviation 
     Administration. The FAA announces all upcoming events in 
     Notices to Airmen. Because of the ever-greater Airway-
     Dependency on GPS, the FAA is increasingly reluctant to grant 
     permission for these tests.
       Accidental RFI has certainly interfered with GPS countless 
     times, both domestically and internationally. Most events are 
     probably not reported. The user who is denied service may not 
     even know to whom it should be reported. These disruptive 
     events include unintentional interference due to harmonics 
     from broadcast television, and improperly designed wireless 
     data communication systems.
       Deliberate interference, called jamming, is the looming 
     threat. Many of the billion GPS users have become extremely 
     dependent on GPS accuracy, 24 hour availability, and 
     outstanding integrity. This dependency makes GPS a very 
     appealing target for sabotage or malicious mischief.
       This white paper is a plea that the National Decision 
     Makers address this situation.
     Deliberate Jamming: the so-called ``Personal Privacy 
         Devices''
       In the past year, so-called personal privacy devices (PPDs) 
     have become widely available on the Internet. A simple 
     example of such products is shown in Figure 1. The most 
     inexpensive PPDs are single antenna devices that jam the one 
     GPS signal frequency (L1) that is used by most users. More 
     expensive units have multiple antennas and attack all three 
     GPS signal frequencies (L1, L2 and L5). As such, these 
     attackers anticipate the next generation of GPS user 
     equipment that would continue to function if only one or two 
     of the three frequencies were jammed. Others PPDs jam cell 
     phone frequencies at the same time, shutting down all calls. 
     They are preferred by car thieves that wish to prevent an on-
     car warning systems to report the location of a stolen car to 
     the authorities using a GPS receiver connected to a cell 
     phone link.
       As shown in Figure 2 (Eldredge, 2010), PPDs range in price 
     from $30 to over $300 based on the number of frequencies 
     under attack and the transmitted power. Some radiate only a 
     few milli-watts and other broadcast several watts. The former 
     knock out GPS receivers for hundreds of yards, and the latter 
     can have dangerous effects for many miles.
       As their name suggests, PPDs are marketed to individuals 
     that fear for their privacy. This sales strategy seems to be 
     effective. An investigation recently initiated by the FAA 
     revealed that trucks traveling on the New Jersey Turnpike 
     were carrying these devices. Perhaps, these drivers worry 
     that the company dispatcher was monitoring their locations. 
     Ironically, the attention of the dispatcher must be drawn 
     to the truck that never provides location reports.
     Jamming Examples--the threat is real and getting worse.
       Newark Airport. In any event, a PPD can cause collateral 
     damage much greater than any privacy protection the user may 
     possible enjoy. The above-mentioned FAA investigation was 
     sparked while the FAA was installing a new GPS-based landing 
     system for aircraft at Newark International Airport. This new 
     system uses GPS receivers on the ground to aid GPS receivers 
     in the approaching aircraft. This technique allows the use of 
     all runways during restricted visibility conditions. The 
     antennas for the FAA's ground receivers are shown in Figure 3 
     (Eldredge, 2010), which also shows the proximity to the New 
     Jersey Turnpike. During system test, the FAA noticed that the 
     GPS ground receivers suffered one or two breaks in reception 
     on many days. PDDs were identified as the cause of the 
     continuity breaks after an investigation that lasted several 
     months. If PPDs gain notoriety, they could gain the interest 
     of hackers. These people may not be particularly worried 
     about their location privacy, but may simply enjoy the notion 
     of jamming GPS over wide areas.
       Military--North Korean Incident. Malevolent RFI is known as 
     jamming. Enemy Jammers were deployed in Iraq to interfere 
     with US weapons systems during Operation Desert Storm. Most 
     recently, military analysts have expressed concern about 
     recent GPS jammers tested by the North Koreans. (Telematics, 
     2010). On August 23 and 25 of this year, jamming signals 
     emanating from the North Korean city of Kaesong. These 
     attacks interfered with South Korean GPS military and 
     civilian receivers on land and at sea. Officials say the 
     jammers were repeatedly switched on for 10-minute periods 
     over a number of hours during the three days. South Korea's 
     defense minister, Kim Tae-young, voiced concern to members of 
     the National Assembly. He correctly observed that the North 
     Koreans can mount transmitters on vehicles that can jam GPS 
     signals within a 50 to 100 kilometer radius. Professor Park 
     Young-wook, with Kwangwoon University's Defense Industry 
     Research Institute, states that such jamming must be 
     considered a serious threat if it reoccurs because GPS is an 
     integral part of the infrastructure, not only for the 
     military but for many other industries.
       We certainly share the concerns voiced by Minister Tae-
     young and Professor Young-wook. However, we feel that the 
     greater danger is posed by the propagation of GPS jamming 
     technology to the wider public through devices sold on the 
     Internet. These threats were described earlier.
       Maritime Controlled-Jamming Experiments. Until recently, 
     GPS receivers for non-aviation purposes have not enjoyed the 
     scrutiny or extensive testing used by the aviation community. 
     Because of their designs and clear line-of sight exposure, 
     Maritime receivers can certainly be more vulnerable then 
     aviation receivers. The following figures (Last, 2010) depict 
     some disquieting results from recent trials conducted by the 
     General Lighthouse Authorities (GLA) of the United Kingdom 
     and Ireland.
       During these trials, a jammer was deployed shown in Figure 
     4. As shown in Figure 5, this jammer had a devastating effect 
     on the shipborne GPS receiver carried through the jamming 
     zone. The receiver reports a faithful position track (in 
     light blue) when the ship is far to the Northwest or far to 
     the Southeast of the jamming wedge.
       Within the wedge, the receiver is overwhelmed and reports 
     no position fix--the jammer breaks GPS continuity. GPS shows 
     no solution. As the receiver approaches or has just departed 
     the wedge, an extremely hazardous result occurs. The receiver 
     suffers large position errors without an accompanying 
     warning--integrity is broken. This is shown as the string of 
     dots to the south and to the southeast of the actual blue 
     track. These last results are most troubling, because the 
     bridge personnel would not be warned that the navigation 
     system was degraded.
       In another set of trials, the GLA placed a low power jammer 
     on board the Trinity House Vessel Galatea. As shown in Figure 
     6, this jammer induced position reports that skipped across 
     Scandinavia and Ireland while the ship sat steadfastly in the 
     English Channel (the yellow track). Among the systems 
     affected by the interference were the ship's radar and 
     gyrocompass, key reversionary systems when GPS fails.
       The worrisome results shown in Figures 5 and 6 would not 
     affect an aviation receiver, because aviation standards 
     insist on an internal set of tests (algorithms) for RFI. We 
     later recommend that these algorithms or equivalents become 
     part of the standards for receivers used in any safety-of-
     life applications.
     Recommended Actions to Counter the Threat of GPS Interference
       There is not any practical way to completely eliminate GPS 
     interference. But steps can be taken to greatly reduce the 
     frequency and impacts of such interference. Further, actions 
     can be taken to insure that GPS receivers do not give false 
     indications of position or time. Our recommendations are:.
       1. National Focus. GPS is absolutely critical US National 
     Infrastructure. This has not been formally recognized. GPS 
     should be formally declared critical infrastructure by 
     Executive Branch and managed as such by DHS. This is 
     necessary to elevate the importance of GPS to our critical 
     infrastructure and bring the needed attention to the 
     interference problem. The various existing national 
     interference programs must be coordinated and gaps must be 
     filled with additional

[[Page E1369]]

     funded efforts (see later recommendations). Senior leadership 
     must recognize the vulnerabilities of the current critical 
     infrastructure and give high priority to budgets and 
     solutions.
       2. National Alerting and Pinpointing Interference 
     Locations. The NATIONAL EXECUTIVE COMMITTEE should establish 
     and sponsor a National GPS Interference Locating, Reporting, 
     and Elimination System; coordinating and expanding on the 
     resources of several Departments. It took several months to 
     locate the PPD that shut down the Newark landing system. 
     Technology exists to locate such sources much more quickly. 
     To rapidly alert and pinpoint interference, two elements are 
     required: 1. sensing of the interference and 2. a 
     communications channel to report the problem in real-time. 
     For example, every cell phone tower could be configured to 
     expand the functionality of their GPS timing receiver by 
     promptly recognizing and reporting interference, including 
     pertinent characteristics. The incremental cost would be 
     extremely small. Another example: many toll booths routinely 
     videotape vehicles including license plates. A properly 
     configured GPS receiver at the booth could identify vehicles 
     that are broadcasting interference. There are many more 
     national reference receivers that could be so configured. 
     Cell phones that include GPS receivers can be configured to 
     sense and automatically report suspected interference. This 
     would constitute a near instantaneous reporting channel, 
     worldwide. Of course a central data-gathering location is 
     needed; it could be collocated with preexisting civil/
     military resources such as WAAS, NGPS or the Air Force's 
     2SOPS. In turn, the located sources must be reported for 
     appropriate action. No such National (or International) Real-
     Time System exists today or is even currently planned.
       3. Shutting Down and Prosecuting Interferers--Legal and Law 
     Enforcement actions. When the mobile jammer was finally 
     located at Newark, the only punitive action for the 
     deliberate interference was to confiscate the Jammer. The 
     coordination of FAA, FCC, FBI, and DOD was commendable, but 
     ad hoc and very tardy. The PNT Executive Board should sponsor 
     Legislation in Congress that addresses interference to GPS 
     with laws that provide substantial fines and jail time for 
     both possession and use of GPS jammers. Precedents have 
     already been established with the laws enacted to prevent and 
     deter lasers being aimed at Pilots as they attempt to land 
     airplanes. Australia, which is also very reliant on GPS for 
     Air Traffic control, has a law that fines the possessor of a 
     GPS jammer $100,000. In addition, operational procedures for 
     rapid interdepartmental reaction and mitigation of 
     interference must be established. A reasonable goal is to 
     locate and shut down any jammer in a matter of hours.
       4. Hardening GPS Receivers and Antennas. In addition to 
     legal action, we wish to galvanize a technical effort to 
     strengthen all GPS receivers. GPS receivers should never give 
     the Hazardous and Misleading Information (HMI) that is shown 
     in figure 6. The techniques to avoid this are well known and 
     specified for all FAA certified equipment. All GPS safety-of-
     life receivers should include the integrity algorithms 
     specified by the FAA. There are also well-known design 
     techniques to greatly reduce outages of GPS receivers due to 
     interference. Examples include: special antennas that null 
     interference, coasting thorough interference by using 
     inertial components and/or small atomic clocks, as well as 
     physical shielding in the direction of presumed jamming. Some 
     would add significant cost but may be warranted for safety-of 
     life and other critical applications. New supplementary 
     devices can make GPS receivers more robust and are becoming 
     more affordable. (e.g. miniature accelerometers, chip scale 
     atomic clocks etc.)
       Some actions are being taken. For example, the FAA is 
     already hardening the GPS receivers and antennas placed on 
     the ground at Newark International Airport. Changes include: 
     GPS antennas that are less vulnerable to radio frequency 
     interference; improved practices for placement of GPS 
     antennas on the airport (farther from public roadways); and 
     receiver algorithms that more quickly recover when the PPD 
     moves away from the GPS antenna. Manufacturers should speed 
     up the offering of interference resistant GPS receivers, 
     especially for safety-of-life applications such as commercial 
     maritime. These receivers should use FAA techniques to insure 
     they do not display Hazardous and Misleading Information 
     during periods of interference.
       5. Establishing GPS Backups to insure continuity of PNT 
     Operations. As described above, GPS receivers should 
     certainly be made more robust against jamming. In addition, 
     we feel that the nation should vigorously support efforts to 
     provide Alternate Position, Navigation and Time (APNT). In 
     this final section, we first describe the role of planned 
     foreign satellite systems (GNSS) that are similar to GPS. 
     Unfortunately they have the same susceptibility to 
     interference as GPS. Next we describe two alternate 
     techniques to determine PNT (APNT) that are more jam-
     resistant and could be readily made operational.
       GNSS. GPS is now recognized worldwide, and other nations 
     are responding with satellite navigation systems of their 
     own. The Russians are reinvigorating their satellite 
     navigation system called GLONASS, and new systems are being 
     developed in China, Europe, Japan and India. Taken together, 
     GPS and these other systems are called Global Navigation 
     Satellite Systems (GNSS).
       These other systems are valuable for improved accuracy and 
     integrity. In addition they will offer frequency diversity. 
     Therefore they will be helpful in countering unintentional 
     interference at a single frequency. The new PFD (Jammers) 
     being sold on the web will also prevent use of these foreign 
     GPS-like systems as well as cell phones. Thus these new 
     foreign systems will not be helpful in operating during 
     deliberate jamming radiated by the better devices currently 
     available.
       While a number of backup PNT systems have been considered, 
     there are two major alternatives for APNT that have emerged 
     as being particularly useful:
       1. e-Loran: Loran is a ground-based radio-navigation system 
     that preceded satellite navigation. It finds its origins in 
     World War II, and enjoyed wide spread adoption after the 
     grounding of the Argo Merchant on Georges Bank. At that time, 
     the U.S. Coast Guard began to require Loran carriage by ships 
     over a certain tonnage in the Coastal Confluence Zone of the 
     United States. Importantly, Loran is based on the broadcast 
     of extremely high power signals in the low frequency portion 
     of the radio spectrum. The frequency of transmission is 
     10,000 lower than the GPS frequencies in the microwave band, 
     and the power of the transmission is 1000 times greater than 
     the GPS transmission power. An updated version of called 
     eLoran has now been developed and tested. It is very robust, 
     resistant to interference and has two dimensional accuracies 
     of about 20 meters in critical areas. It is not nearly as 
     accurate as the best GPS, and the lack of the vertical 
     dimension reduces eLoran's effectiveness, yet it is a very 
     robust APNT system.
       In December 2006, an Independent Assessment Team was 
     appointed, reporting to DOT and DHS. It was under the 
     administration of the Institute for Defense Analysis (IDA). 
     After careful review over many weeks, they unanimously 
     recommended that the eLoran deployment be completed as a 
     backup for GPS. Yearly cost to maintain this in the US was 
     about 20 $M. This is about 1/10th the cost of a single GPS 
     satellite. The DHS then made an announcement that eLoran was 
     the official APNT system for the US. The Schlesinger-chaired 
     PNT Advisory Board has also unanimously recommended that 
     eLoran be deployed and maintained as a GPS backup.
       For these reasons, the international navigation community 
     has also strongly supported the upgrade and sustainment of 
     the Loran system in any number of forums. This recommendation 
     has been heeded in Europe. Indeed, Figure 7 shows the 
     faithful position track provided by enhanced Loran (e-Loran) 
     as the ship traverses the jamming wedge generated by the 
     General Lighthouse Authorities from Flamborough. Figure 7 
     provides a stark contrast to the GPS-based results in Figure 
     5. Unfortunately, DHS has not followed through with their 
     announcement: the Loran system in the United States has been 
     turned off.
       We strongly recommend that the previously announced 
     decision (to deploy eLoran as the primary APNT) should be 
     reconfirmed and quickly implemented. The reasons for this are 
     clearly stated in the IDA white paper. It is the most viable 
     and robust backup to GPS and can be implemented in a way that 
     is virtually seamless to the user.
       2. Alternate Navigation for the Next Generation Air 
     Transportation System: Today, the FAA uses an extensive 
     network of terrestrial navigation aides to mitigate GPS 
     outages. This backup navigation capability is based on 
     ground-based navigation aids that precede GPS. All of these 
     extant systems support point-to-point navigation. Even though 
     these transmissions are reasonably robust against RFI, this 
     point-to-point capability may not be suitable for the Next 
     Generation Air Transportation System (NextGen). NextGen 
     anticipates an increase in air operations by a factor of two 
     or more by 2025, and will enable a host of operational 
     improvements needed to smoothly support this traffic 
     increase. NextGen is based on GPS, satellite-based 
     augmentation systems (SBAS), and ground-based augmentation 
     systems (GBAS). All of these systems provide so-called area 
     navigation (RNAV). In other words, they provide guidance over 
     a volume, and the alternate navigation system of 2025 also 
     needs to provide a volumetric aid to navigation.
       Thus, the FAA is actively exploring alternate position, 
     navigation time (APNT) as part of their NextGen effort, 
     because the airspace should not revert to inefficient point-
     to-point navigation should RFI interrupt GPS-based operations 
     in the 2025 timeframe. This APNT capability would be based on 
     a reconfiguration of existing or planned FAA ground 
     facilities (Eldredge, 2010), and Figure 8 shows part of the 
     ground infrastructure that can be utilized to provide this 
     APNT area navigation capability.
       Time Synchronization: As part of their APNT effort, the FAA 
     has identified three architectures that may be suitable for 
     alternate area navigation in 2025. These straw men are based 
     on the sites shown in Figure 8, but two of these APNT 
     architectures require time synchronization of neighboring 
     ground sites. To this end, the FAA has investigated time 
     transfer based on hardened GPS receivers and low earth 
     orbiting satellites (LEOs). In the former case, jammers are 
     attenuated by so-called controlled radiation pattern 
     antennas. In the latter case, the

[[Page E1370]]

     needed processing gain derives from the proximity of the 
     LEOs. Indeed, the altitude of the LEOs is approximately 
     twenty times less than the GNSS altitude. Thus LEOs have 
     small earth footprints and cannot provide the navigation 
     performance associated with GNSS. However, the signal 
     received from this nearby source is approximately 400 times 
     greater than the power received from GNSS. Thus, LEOs could 
     provide the robust time transfer capability needed to support 
     APNT, because time transfer only requires one satellite to be 
     in the common view of the ground stations to be synchronized.
       We encourage the FAA to continue efforts and to provide an 
     APNT that is a robust backup to GPS and deterrent to 
     malicious interference.
     Summary and Conclusions:
       The interference threats to GPS are very real and promise 
     to get worse. These threats potentially imperil much of the 
     US. infrastructure. It will take some time to field a full 
     set of countermeasures and systems. Failure to act will be a 
     serious abdication of our national responsibility.

                          ____________________