Dual-Satellite Geolocation of Terrestrial GNSS Jammers from Low Earth Orbit

Abstract

This paper explores two-step and direct geolocation of terrestrial Global Navigation Satellite System (GNSS) jammers from Low Earth Orbit (LEO). Within the past decade, there has been a sharp increase in GNSS outages due to deliberate GNSS jamming. Receivers in LEO are uniquely situated to detect, classify, and geolocate terrestrial GNSS jammers. The conventional two-step geolocation method first estimates the differential delay and differential Doppler, then uses a time history of these to estimate the transmitter location. By contrast, direct geolocation is a single-step search over a geographical grid that enables estimation of the transmitter location directly from the observed signals. Signals from narrowband, matched-code, and chirp jammers recently captured in the GNSS frequency bands by two time-synchronized LEO receivers over the Eastern Mediterranean are analyzed and the emitters geolocated. It is demonstrated that the direct approach is effective even for low signal-to-noise ratio interference signals based on short captures with multiple emitters. Moreover, the direct approach enables geolocation of multiple emitters with cyclostationary signals (e.g., chirp jammers), whereas the two-step method struggles in such cases to associate emitters with their corresponding structures in differential delay and Doppler space.