A US Program to Identify, Geolocate, and Mitigate Sources of GPS Interference But are we serious? Terry McGurn/Consultant Presented to the EXEC PNT Advisory Board Meeting of 5-6 November 2009

Background & Motivation Motivation: NSPD-39, Dec 2004 –Maintain Continuity of GPS service in an interference environment –Deny hostile exploitation of this service. NSPD-39 Actions (From Fact Sheet) –Establish a PNT EXCOM to address these issues, among others –Establish the EXCOM Advisory Board –Establish Agency Roles

CONCLUSIONS Language of the NSPD-39 Fact Sheet is vague. Open to Various Interpretations of Assignments. NSPD-39 Muddies the Issues (friendly protection & hostile denial). I Believe The Program is Headed in the Wrong Direction. But I believe we can get back on track.

DHS: The Action Agency DHS has taken action on this program. –DHS developed an IDM paper to address this issue, published in Largely reflects NSPD-39 –The DHS, as well as its contractors, have been very forthcoming when I’ve contacted them to obtain information on their program. But we differ greatly on the proper approach.

So What’s Wrong? No one is tasked to develop and array sensors to detect/geolocate interferers. The fact sheet, as well as responses to it, reflect a belief that we have these assets already in place, and the task is primarily to coordinate these assets. There are assets available that could be netted to support the program, but these are only mentioned in passing.

So What’s Wrong? (Cont,d) The responsible DHS body for this program appears to be the Office of Infrastructure Protection within the Directorate for National Protection & Programs, and several of its high level appointees are not yet in place. I believe the present DHS approach puts the cart before the horse. (i.e., developing the “data repository” before developing the sensors that will provide the “reposing” data.) In fact, the sensors should dictate the degree of processing to be done at the repository vice in the field.

So: What Can We Do Now? DHS should address the pieces of the issue. The “one size fits all” approach not practical Intentional jamming, spoofing, unintentional interference are different problems. But, at present, unintentional jamming appears to be the most frequent source of signal loss. So Let’s develop a capability to minimize the occurrence of unintentional jamming? You don’t get partial credit if you lose a critical function unintentionally.

Recommendations Define Specific Responsibilities for the Various Components of the Network. (An EXCOM role?) Suggest Several Small Funded Efforts. (Requires more selective expertise/less PPT.) Responsible Dept/Agency should have System Engineering Support. Let’s Get a Significant Start. First Address the Unintentional Jamming Issue.

Examples of Unintentional Jamming Rome, NY, ADC (3 days/5 watts/ several hundred kilometers) ( ) St. Louis Airport (1990s) Butte, Montana (? days, spurious harmonics) Monterey Bay (many months/ VHF/UHF TV antenna radiating above the L-band noise floor) (~2001) San Diego Navy Test Center (4 hrs, 500 mw) (2004)

DGPS Site Inoperative 2 Hours AIS Display Console Anomaly Cell Provider Network 150 sites detected error 2 sites inoperative Medical Services Paging Provider Network Inoperative 1.5 Hours – 20 sites General Aviation Pilot Report GPS Malfunction Potential for First Responder Impacts Interference Case Study

Introduction - Typical digital GNSS receiver block diagram RF front end

Introduction - GNSS receiver front end with Digital Gain Control ADC Digital Gain Control Analog IF J/N Meter Digital IF Down Converter Antenna Preamp Digital Attenuator Gain Controlled Analog IF

Final Thoughts Mitigation: –Where possible, geolocate and prosecute –Otherwise: Back-up Systems –Inertial (short term only. Present inertial trends are for poorer performance, low-cost systems. –eLoran: Provides high availability, good anti- jam, and good timing performance (sigma about 30 nsec). –Smart receivers, for situational awareness.

Final Thoughts (Continued) “When everyone’s in charge, no one’s in charge”. (A retired Russian Colonel, in discussing the problems in the GLONASS program) This is a hard problem. But a challenging one. Tackle it bit by bit.