Sensor fusion for sense and avoid for small UAS without ADS-B

Small UAS have highly constrained payload capacity, which dictates what sensors and transmitters can be selected as part of the electronics suite. We present elements of a sense and avoid (SAA) system which enables UAVs to track intruder aircraft not broadcasting ADS-B. Such SAA methods help assure safety in cases of late encounters with non-cooperative threats. This paper presents an approach to selecting a multi-modal sensor suite and fusing measurements without reliance on ADS-B broadcasts. Dubbed ASSIST (AsynchronouS Sensor fusIon SysTem) for UAS, the system fuses whatever sensors are available when ADS-B is not available, such as camera, ground-based radar (GBR) and airborne-based radar (ABR) measurements with Mode C Transponder information to achieve threat estimation accuracy similar to that obtained using ADS-B. By using the GBR as the baseline, ASSIST effectively removes both ground and aerial clutter.