U.S. Department of Transportation (DOT) Global Positioning System (GPS) Interference Detection and Mitigation (IDM) Program

Abstract

Global Positioning System (GPS) Based Positioning, Navigation, and Timing (PNT) services support the United States transportation sector in safely transporting people and goods and enabling efficiencies resulting in benefits to national and economic security. GPS signals are broadcasted from a constellation of satellites orbiting in Medium Earth Orbit (MEO) and their signal strength at the user receiver is very low in signal power density magnitude and thus susceptible to unintentional and intentional signal disruption or manipulation from undesired sources. Two recent real-world events in the transportation sector highlight the impacts related to the susceptibility of these GPS signal disruptions and the constant need to improve the GPS Interference Detection and Mitigation (IDM) posture of the Department of Transportation with the goal to restore GPS based PNT services to the expected levels of availability and reliability. This IDM mission goal contributes to an overall resilient PNT services posture when GPS is quickly restored to the expected normal operating conditions. On January 21, 2022, the GPS signal-in-space around the city of Denver, CO was degraded by the presence of unwanted emissions south of the Denver International Airport1 . Numerous aircraft, train stations, emergency response communication towers and medical messaging services detected and experienced varying levels of GPS signal reception degradation for a period of approximately 33 hours until the unwanted emissions source was positively identified and shut down. On October 17, 2022, the GPS signal-in-space around the cities of Dallas and Fort Worth, TX was degraded by the presence of unwanted emissions southwest from the Dallas-Ft. Worth International Airport. Numerous aircraft in the terminal and air route airspace detected and experience GPS signal reception degradation for a period of approximately 44 hours. Ground infrastructure recordings of GPS signal degradation effects were absent during the active event affecting aircraft. The unwanted emissions source ceased without positively being identified.