Rapid Emitter Geolocation

A comprehensive survey of threat radar positions (range as well as bearing) including short up-time and intermittent (on/off) emitters is extremely valuable during a conflict. A safe course can be plotted for friendly aircraft, electronic warfare (EW) systems can effectively jam radars using far less power (Electronic Attack (EA)), or a missile can be launched to neutralize possible threats (Kinetic Attack (KA)). Adversaries understand the need to limit their emissions. To decrease their vulnerability, radar operators perform searches using short up-time scanning techniques to avoid detection and/or geolocation. Solid-state transmitters utilizing agile, low-power pulse Doppler waveforms are becoming increasingly prevalent in modern radar threats. These low-power emitters may also be intermittent and adaptive making them difficult to detect or geolocate. Active Electronically Scanned Arrays (AESAs) employ random beam azimuths and countermeasures to avoid detection. Surface-to-Air Missile (SAM) threats to aircraft have become increasingly mobile and difficult to detect from the air before an engagement e.g., Shoot-and-Scoot (S&S) SAMS.  Historically, passive airborne radar locating systems have relied on a time-intensive process (Radio Frequency Direction Finding (RFDF)) to cumulatively plot successive Lines of Bearing (LoBs) to the target radar until an accurate geolocation (fix) of the radar could be determined. Usually, minutes are required for RFDF to achieve a suitable angular bearing spread to develop a reasonable geolocation estimate for an emitter. Alternative approaches such as time difference-of-arrival (TDOA) require precise coordination between multiple platforms, which can greatly increase system cost and complexity and are not practical during tactical encounters in contested airspace. ISL has developed a passive approach to rapidly geolocate both littoral and land-based radars. We envision this technology implemented as an automated software mode resident on a (group 2 or 3) Unmanned Air System (UAS).  In this proposal, we propose to expand the technique to militarily relevant emitters that employ random beam azimuths such as an AESA. Our initial approach emphasizes progressively complex simulation to validate the concept. In Phase I (base), the geolocation performance and approach will be demonstrated using simulated data from our commercial M&S environment, RFView® (see recent SBIR Success Story press release https://www.sbir.gov/node/1526807). Using RFView®, we don’t need RF measurements to develop the solution. In the Phase I (option), we will port the primary software routine to an extremely low power computational adjunct and demonstrate the reduced timeline.