The German Space Operations Center (GSOC) performs collision avoidance for 11 LEO and 2
GEO satellites. Risk detection and maneuver decisions strongly depend on the computed probability
of collision that is driven by the anticipated orbit precision of chaser and target. While the orbits of
operational satellite are well known this is usually not the case for space debris. Therefore, an
improved collision assessment requires refined orbit determination of the chaser object.
This paper describes the achievable orbit precision for a small object based on radar
measurements. The Tracking and Imaging Radar (TIRA) of Fraunhofer FHR in Wachtberg,
Germany, was used to track the Canadian nanosatellite CanX-2 over a period of five days. CanX-2
is a triple CubeSat of the size 10x10x34 cm carrying a dual frequency GPS receiver. A reference
trajectory is established by precise orbit determination (POD) from GPS measurements. Radar
tracking measurements and derived orbital information are evaluated by comparison against the
reference orbit. Statistics of the orbit determination and orbit prediction precision using different
radar measurement data arc lengths is presented leading to a better understanding of the prediction
uncertainty of critical close approaches between an active satellite and a small object
