Precise orbit determination method for BeiDou mixed constellations with layered constraints

Considering the unique GEO+IGSO+MEO constellation design of the BeiDou Navigation Satellite System (BDS), a method for BeiDou satellite precise orbit determination that adopts different constraints and data processing strategies for different constellations is studied. And a precise orbit determination scheme with layered constraints for BeiDou mixed constellation is proposed. BeiDou satellites are divided into two parts, non-GEO (IGSO/MEO) and GEO, to be solved step by step. The public parameters calculated by GPS are used to form effective constraints on BeiDou IGSO/MEO precise orbit determination. Then the GPS and BeiDou IGSO/MEO calculation results are fixed, and BeiDou GEO satellites orbit determination is performed under strong constraints.The results of precise orbit determination tests based on real observation data show that, using the method proposed in this paper, the 3D position RMS (root mean square) of overlapping orbit differences of the BeiDou GEO satellites and non-GEO satellites reach 0.688 m and 0.042 m, yielding an improvement of 54.2% and 72.4% compared to that of using the traditional method. In addition, the satellite laser ranging (SLR) validation and static precise point positioning (PPP) of station coordinates results are analyzed to verify the orbit accuracy. The SLR validation accuracy increased by 44.3%, and the accuracy of station coordinates in horizontal and vertical directions increased by 21.5% and 20.7% on average, respectively