Designing a robust detect and avoid alerting function

In the context of the development of the Minimum Operational Performance Standards (MOPS) for UAS Detect and Avoid (DAA) systems by RTCA Special Committee 228 (SC-228), three new traffic-related alerts have been defined: Preventive, Corrective and Warning. To achieve an acceptable balance between missed/late alerts and incorrect alerts and minimize the occurrence of realerts on the same target, mitigations are needed that increase the robustness against measurement and prediction inaccuracies. This paper discusses how the use of time to co-altitude, data filtering, alert filtering, alert hysteresis and sensor specific adaptive thresholds can be applied to increase the robustness of the alerting function.