Operational Results of Conjunction Assessment and Mitigation at German Space Operations Center

Abstract

Results of the collision avoidance operation at the German Space Operations Center (GSOC) are presented in this paper. Currently, five operational satellites in the LEO region are supported in the monitoring system. In addition to the daily prediction using Two-Line Elements (TLEs) as source of orbital elements for space objects, possible critical approaches are also detected by the proximity search performed by Joint Space Operations Center (JSpOC). An automated alarming system is available for both screening results, and the detailed risk evaluation is performed by the Flight Dynamics team in case of a remaining high risk. After the introduction of the operational collision avoidance procedure, the risk assessment process for critical close approaches as well as the maneuver planning strategy are further discussed in this paper. For the two operational satellites TerraSAR-X and TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurement), which are controlled against a reference orbit inside a control tube with a diameter of 500 m and in a very close formation (min. distance of about 400 m), a dedicated mitigation strategy has to be applied to minimize the violation of strict mission requirements. Two cases of the recent critical approach are presented for these satellites, which lead to the execution of a collision avoidance maneuver after a careful risk assessment, followed by the operational experiences and feedbacks.