Observability of Satellite to Satellite Passive Tracking from Angles Measurements

A single satellite to satellite passive tracking from angles measurements have great significance in space surveillance system. This paper focuses on the state observability problem, which is the important theory issue for satellite to satellite passive tracking. The state motion equation and measurement equation are deduced in three-dimensional modified spherical coordinates (MSC) based on Cartesian coordinates. A necessary and sufficient condition for state observability is deduced accommodating any motion forms, which accelerations are decided by position and velocity vectors. Finally the system observability can be fulfilled in satellite to satellite passive tracking is proposed and proven in detail.