Yaw attitudes for BDS-3 IGSO and MEO satellites: estimation, validation and modeling with intersatellite link observations

Abstract

Previously disclosed satellite metadata, as well as previous estimations using the reverse kinematic precise point positioning approach with L-band data, have already demonstrated the use of a continuous yaw-steering model by the BDS-3 Medium Earth Orbit (MEO) satellites manufactured by the China Academy of Space Technology (CAST) in deep eclipse periods instead of the orbit-normal mode. However, the yaw model has not been validated for MEO satellites manufactured by the Shanghai Engineering Center of Microsatellites (SECM), as the horizontal phase center offsets are close to zero. Moreover, the attitude model has also not been confirmed for BDS-3 Inclined Geostationary Orbit (IGSO) satellites. In this study, the intersatellite link (ISL) data are used to estimate the yaw angles of BDS-3 IGSO and MEO satellites with an accuracy of approximately 3.0° to investigate their yaw behaviors, particularly in deep eclipse periods. The estimates confirm that the IGSO and MEO satellites from CAST show the same yaw behaviors, while the SECM MEO satellites do not fully comply with the attitude law published by the China Satellite Navigation Office (CSNO). The attitude transition deviates from that predicted by the CSNO yaw law and occurs when the elevation angle of the Sun above the orbital plane (beta -angle) crosses 0° and the absolute value of the yaw angle is no more than 5°. The transition is completed within three to five minutes at a rate of approximately 0.055°/s. A model is proposed to predict these behaviors, and the ISL residuals return to normal levels and become more stable adjacent to midnight and noon points when the yaw models are used.