Chapter 4 Precise Orbit Determination for COMPASS IGSO Satellites During Yaw Maneuvers

摘要

Contrary to GPS and GLONASS, the COMPASS IGSO satellites use two different attitude modes depending on the Sun's elevation angle with respect to the orbital plane, namely yaw-steering regime and yaw-fixed regime. However, transition of attitude modes will cause the significant degradation of the orbit accuracy. We present two approaches to improve the orbit accuracy based on Extended CODE Orbit Model (ECOM) and Adjustable box-wing model. The differences of overlapping orbits and SLR validation indicate that the orbit accuracy could increase to better than 30 cm from several meters level during yaw maneuvers. Furthermore, we investigate the possible reasons of orbit accuracy degradation with telemetry data, and the reasons are likely the variations of non-gravitational forces in along- and cross-track directions caused by attitude mode switches, temperature variations of －X bus and some devices on －X surface which result in non-systematic geometry of －X and ＋X bus.