Low-Complexity Direct Geolocation of Terrestrial GNSS Jammers from Low Earth Orbit

Abstract: This paper introduces a low-complexity technique named quasi-direct geolocation (QDG) to perform passive radio-frequency (RF) geolocation of emitters directly in the position domain, akin to direct geolocation (DG) and direct position determination (DPD). The proposed technique drastically reduces the complexity of DG/DPD and is experimentally demonstrated in geolocating a terrestrial jammer at Jammertest 2025 from a repurposed satellite in low Earth orbit (LEO): OPS-SAT PRETTY. The goal of QDG is to enable satellites to contribute to a multi-constellation system for RF interference (RFI) monitoring as opportunistic spectrum sensors in global navigation satellite systems (GNSS) bands, even if these are constrained by low size, weight, and power (SWaP). They can serve as data collectors and/or edge computers. In the former case, QDG can be used to compress large volumes of I/Q samples into minimal signal information, which can be relayed to ground for post-processing via low-capacity downlinks. In the latter case, QDG can be used to compute the geolocation of RFI sources in orbit on low-power on-board computers (OBC). The drawback of these capabilities is lower sensitivity and accuracy than DG/DPD plus limitations on the types of signal sources that can be geolocated, which, nonetheless, include the most common GNSS jammers.