Accuracy Analysis of the Calibration Satellite Orbit Determination Based on Onboard BDS Data

Launched in November 2018, the first calibration satellite carried onboard a spaceborne multimode receiver, which can get dual-frequency GPS and BDS B1I&B3I signals at the same time. In this paper, both of the GPS and BDS dual-frequency data of the satellite were used to determine the precise orbits by using the non-difference reduced-dynamic method. After a brief introduction of theory and strategy, the results and accuracy analysis of GNSS-based Precise Orbit Determination (POD) were detailed by employing the GPS-only derived orbits as a reference. In order to ensure the accuracy and reliability, the quality of GPS-only reduced-dynamic orbits was evaluated first. For GPS-only solution, the 3D position RMS error of the 6-h overlapping arcs is less than 1.2 cm when comparing two 30-h adjacent arcs, and the comparisons between reduced-dynamic orbit and kinematic orbit display a radial RMS error of 6 cm and 3D position RMS error of 10 cm, with an average of about 8 cm. For BDS-only solution, the experimental results show that, on the basis of 24-h dual-frequency data, the BDS-only orbits have a RMS error of 10 cm in three-dimensional position, with a RMS error of 4 cm, 8 cm, and 3.7 cm in the radial, along-track, and normal direction respectively, when compared with the GPS-only orbits. In conclusion, the experiments in this paper prove that using dual-frequency BDS data for precise orbit determination, POD for LEO satellites can achieve an orbital accuracy of 10 cm or even better.