Research on Improving Orbit Determination Accuracy of BDS-3 Full Operational Constellation by Ground Observations Enhanced with Inter-satellite Links

To reduce the number of monitoring stations while maintaining orbit and clock offset accuracy in the Precise Orbit Determination (POD) and time synchronization of the BeiDou satellite based on the data fusion of Inter-Satellite Links (ISL) and L-band ground-based receivers, a joint data experiment scheme was designed using a one-way ISL data processing method and applied to the full BeiDou constellation. The relationship between the reduction in the number of global network monitoring stations and the variation in POD and clock offset accuracy was calculated, as well as the orbit and clock offset changes when the ground-based tracking network was reduced to a regional network. The results show that the overall orbit accuracy of ISL-ground data fusion is superior to that of pure ground-based data, while the clock offset accuracy is also affected by specific data processing strategies. The orbit accuracy of MEO satellites is 8 cm, and the satellite clock offset accuracy is better than 0.1 ns. Under data fusion conditions, when the number of global network ground stations is reduced to eight, the orbit accuracy remains at the 10 cm level; when the number of ground stations is reduced to seven domestic regional stations, the orbit accuracy is maintained at 13 cm.