The Datum Optimization Method for Satellite Clock Batch Estimation

Objectives: The ultra-rapid satellite clock product is the premise of high-precision Precise Point Positioning (PPP) service for users with limited network. The satellite clock stability affected by the clock datum is crucial for the positioning accuracy of PPP. The traditional clock datums fix an individual receiver clock for satellite clock batch estimation. However, the reference receiver clock is unstable caused by clock noise, which will reduce the stability of batch estimated satellite clock. Methods: By constructing quasi-stable constraints weighted by the receiver clock model accuracy, an optimized clock datum is constructed based on the robust partial barycenter datum for receiver clock group to improve the stability of satellite clock batch estimation. Results: One-month GPS satellite clock batch estimation experiments based on global network observation data have been implemented. By comparing with the traditional and the proposed clock datums, for different satellite types of BLOCK IIF Rb, BLOCK IIF Cs, BLOCK IIR Rb, BLOCK IIR-M Rb and BLOCK III Rb, the stability evaluation results have revealed that the satellite clock model accuracy is improved by 43.10%, 1.73%, 23.47%, 16.34% and 47.49%, respectively. The frequency stability of 1,000 seconds is improved by 9.59%, 0.04%, 0.35%, 0.33% and 11.22%, respectively. The frequency stability of 10,000 seconds is improved by 11.53%, 0.60%, 7.62%, 4.83% and 18.21%, respectively. Conclusions: The proposed method can effectively reduce the impact of unstable reference receiver clock on the stability of satellite clock batch estimation, and improve the stability of ultra-rapid satellite clock product. The accuracy of satellite clock prediction and PPP are then improved, respectively.