BDS Precise Orbit Determination with iGMAS and MGEX Observations by Double-Difference Method

Abstract

The double-difference method is used to determine the BeiDou Navigation Satellite System (BDS) orbit with 5 stations of the first phase of international GNSS Monitoring and Assessment Service (iGMAS) and 8 stations of Multi-GNSS Experiment (MGEX). The code multipath errors RMS of B1, B2 and B3 are 0.45, 0.43 and 0.26 m for iGMAS observations, respectively, which are comparable to that of MGEX stations. The average carrier phase errors RMS is 1.79 cm for iGMAS observations and 0.82 cm for MGEX data. Moreover, the precise orbit determination (POD) results of BDS with only 5 iGMAS stations are presented. The post-fit residuals RMS of the double-difference ionosphere-free code and carrier phase are 1.9 m and 7.4 mm. The accuracies of GEO, IGSO and MEO are 0.34, 0.20, 0.71 m in the radial component, while the 3D-RMS are 1.48, 0.66 and 3.05 m. Furthermore, 8 MGEX stations are added to solve the BeiDou satellites orbit. The radial RMS of orbit overlapping is approximately 0.2 m. The 3D-RMS is 0.88 m for GEO and 0.61 m for MEO. The tracking geometry is enhanced by adding the MGEX stations, which improves the accuracies of GEO and MEO satellites. However, the overlapping RMS of IGSOs is not improved. Additionally, the RMS of phase post-fit residuals is beyond 2 cm for some baselines and is obviously larger than that of the baselines between iGMAS stations. The enlarged residuals indicate some potential discordance for the observations between iGMAS and MGEX stations.