This research aims at developing methods to meet safety targets for sense and avoid (SAA) sensors of Unmanned Aircraft Systems (UAS) through integrity and continuity risk evaluation. The SAA problem is presented as a three-dimensional, two-body problem. A Kalman filter approach is introduced to accommodate arbitrary sensor suites. Aircraft relative position and velocity estimates, referred to as trajectory state estimates, are transformed into hazard state estimates, which are used to quantify integrity and continuity risks. A sensitivity analysis is performed based on a set of representative, near-worst-case, three-dimensional intruder trajectories. The resulting impact on integrity and continuity is quantified for a composite nominal sensor. The concepts and methods in this research are intended to be used as a tool for certification authorities to set potential requirements for integration into the national airspace system.