Improving BDS-3 precise orbit determination for medium earth orbit satellites

Abstract

As of June 2019, 18 BDS-3 medium earth orbit (MEO) satellites have been launched into orbit. We perform precise orbit determination for these BDS-3 satellites with the rate-limited attitude models and the a priori box-wing solar radiation pressure model. The BDS-3 MEO satellites employ continuous yaw-steering attitude mode. By using proper yaw-attitude models during deep eclipse seasons, the orbit overlapping can be reduced by (0.6, 0.5, 0.4) cm for satellites developed by China Academy of Space Technology (CAST) and (0.5, 0.4, 0.3) cm for satellites developed by Shanghai Engineering Center for Microsatellites (SECM) in along-track, cross-track, and radial components, respectively. Compared to nominal attitudes, the attitude models also reduce the RMS of ionospheric-free carrier-phase residuals from 1.87 cm and 1.83 cm to 1.74 cm and 1.79 cm for CAST and SECM satellites in deep eclipse seasons, respectively. In addition, the satellite clock residuals become smoother by using the rate-limited yaw-attitude models. By applying the a priori box-wing SRP model along with a 5-parameter extended CODE orbit model (ECOM1), the orbit overlapping can be reduced to (6.9, 3.8, 1.9) cm for CAST satellites and (10.6, 5.8, 2.4) cm for SECM satellites, which are (0.6, 0.7, 0.6) cm and (0.7, 0.5, 0.7) cm smaller compared to those of the updated ECOM model (ECOM2). The BDS-3 orbits are then validated by satellite laser ranging (SLR), and the results demonstrate mean biases of 0–5 cm with standard derivations of 3–6 cm. The SLR validation also reveals that using an a priori box-wing model can reduce the SLR mean biases and standard deviations when compared to the ECOM2 model.