Incorporating Satellite Laser Ranging observations into BDS analysis: from the perspectives of orbit validation, precise orbit determination, and geodetic parameters estimation

In February 2023, the International Laser Ranging Service started the tracking of additional medium Earth orbit satellites from the global BeiDou navigation satellite system (BDS) constellation, increasing the total number of tracked BDS satellites to 27. As an optical space geodesy technique, the Satellite Laser Ranging (SLR) provides another important measurement for BDS other than the microwave (L-band) one. Based on three years of data from June 2021 to May 2024, the potential benefits of introducing SLR data into BDS processing and analysis are investigated from three key aspects: orbit validation, precise orbit determination, and geodetic parameters estimation. The independent SLR validations of BDS precise orbit products from four analysis centers show that using the a priori box-wing model for solar radiation pressure (SRP) modeling can achieve superior performance than purely empirical models. The results also indicate the existence of SRP modeling deficiencies for some satellites such as C45 and C46 with Search and Rescue payloads. Given a sparse ground network with 5 stations, the introduction of SLR significantly stabilizes the SRP parameter estimates and improves the orbit accuracy by 44.4%. In terms of geodetic parameter estimation, the scatter of the Z-component geocenter motion can be effectively reduced with the inclusion of SLR data, presenting 10.9–15.3% smaller root mean square (RMS) values during February 2023 and May 2024, depending on the SRP models. In addition, the annual amplitudes of the Z-component geocenter motion are reduced by 7.2–48.2%. The improvement is more pronounced with a limited number of microwave stations, due to the greater strength of SLR observations in geocenter motion estimation. On the other hand, since the SLR observations are unhomogeneously distributed in both space and time, the incorporation of SLR does not evidently enhance the accuracy of Earth rotation parameters, and may even to some extent contaminate the results when the number of microwave stations is limited.