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An unmanned aerial system (UAS) based system has been developed to be able to rapidly localize the source of GNSS interference to minimize the impact interference would have on critical infrastructure, such as an airport. Previously, the project, known as Jammer Acquisition with GPS Exploration and Reconnaissance or JAGER, has demonstrated capabilities of localizing a signal source in real time by physically rotating the antenna, however this approach proved to be a slow approach to localization [1]. Since that demonstration, the sensor has been upgraded to be electronically steered, the localizing algorithm and path planning has been improved to account for the higher rate of bearing measurements, and a GNSS independent navigation system has been developed. Each of these pieces have been demonstrated individually in both flight tests and simulation, however, until now, the full system has not been operated together in real-time [2]–[4]. This paper presents the real-time implementation of all the core sub-systems making up the JAGER platform working together to localizing a signal source in a GNSS denied environment. The JAGER system is made up of three sub-systems: the interference localization system, a GNSS denied navigation system, and a path planning system. The interference localization system is comprised of an electronically beam steered antenna making signal strength measurements to create received signal strength (RSS) patterns from which bearing information can be used to estimate the RFI source location. The GNSS denied navigation system is built around using optical flow from a gimbal stabilized FLIR Systems Boson infrared (IR) camera to measure velocity and in turn estimate the position of the vehicle. Finally, the path planning system sends velocity commands to the autopilot to fly a desired trajectory to get the best bearing measurements for estimating the RFI source. Flight tests were performed at Edwards Air Force Base with a 2W, 5MHz wide, 2.48 GHz signal source being localized by JAGER. The GNSS denied environment was created in software by disabling the use of GNSS by the autopilot for real time guidance and control. The flight tests were conducted at night, in the early morning (pre-sunrise), and in the late morning to stress test the IR based vision system and demonstrate the capabilities in a range of time periods. The location chosen at Edwards Air Force Base also consisted of a large hangar door that presented “urban environment”-like challenges (namely reflections of the signal source). The flight tests comprised of 35 different mission attempts, where a mission consists of starting from a known location and fully autonomously executing the localization of the signal source with no user interaction until the source was determined to be localized. Of the 35 different mission attempts, 16 successfully localized the signal source with an average final 2D localization error of 13m, and the vision system demonstrated a drift rate of 4% and 6.1% during the day and night, respectively. |
