Parameter estimation of GNSS real-time satellite clock error and its application in PWV retrieval

GNSS real-time PPP have been demonstrated to be applicable to PWV retrieval effectively. The GNSS real-time satellite clock error is one of the essential factors that affects the accuracy of PPP, and its estimation method is usually considered to be white noise random processes which ignore the stable periodic variation characteristics of GNSS atomic clocks. In addition, the GNSS satellite clock offsets real-time service have low timeliness due to the time consumption of clock offsets series estimation and fitting of quadratic polynomial coefficients, even when communication is interrupted for a short period of time, RTS cannot be obtained. Thus, we developed a method that directly estimate satellite clock model coefficients simultaneously with tropospheric wet delay, receiver clock error, and phase ambiguity parameters from global GNSS code and phase measurements. The difference from traditional RTS is that the satellite clock model coefficients can be delivered to PPP users once estimated process is completed without the step of fitting. Several satellite clock models composed of polynomial and harmonic-based functions are applied to the parameter estimation of real-time satellite clock error, we compared the accuracy of estimated model parameters to IGS real-time satellite clock offsets, and discussed its performance of PPP positioning and PWV retrieval. Finally, we simulated the performance of proposed parameter estimation scheme of satellite clock error and PWV retrieval for different update interval in case of communication interruption for several minutes.