Covariance analysis and its impact on the operational conjunction assessment

Abstract

Korea Multi-Purpose SATellite(KOMPSAT) series in the low earth orbit(LEO) region and Communication, Ocean and Meterological Satellite(COMS) in the geostationary earth orbit(GEO) region are operated by KARI. The conjunction assessment for operational satellites against space objects, which are cataloged by Joint Space Operation Center(JSpOC) is conducted twice a day to ensure the safety of satellites. The conjunction anlaysis provides the time of closest approach(TCA), the minimum distance, the radial distance, the collision probability and geometric information based on the orbit prediction. Espectially, the collision probability which is major criteria for the preparation and execution of risk mitigation maneuver, depends on the hardbody radius(HBR) of two objects and the orbit uncertainty. In this paper, the sensitivity analylsis on collision probability due to the influence of object size and covariance is performed. First, the covariances of operational satellites are generated by carrying out the orbit estimation. Then the covariances are propagated by using position uncertainty within three days before TCA. The characteristic of collision probability in accordance with each covariance and the space object size is presented. In addition, a comparative analysis was performed with the conjunction data message(CDM) from JSpOC and the collision probability by applying the covariance and size through the real conjunction event.