Abstract: GLONASS system generates inter-frequency bias (IFB) using frequency division multiple access technology to distinguish satellite signals in the process of GPS/GLONASS satellite clock estimation. Base on the analysis of IFB parameter characteristics in the orbit determination process, the IFB is considered on the real-time GPS/GLONASS satellite clock estimation. At the same time, in order to solve the problem of weak real-time caused by excessive parameters in this estimation process, the mathematical model is improved based on the non-difference pseudo-range observation value and the difference phase observation between the epochs. The results show that the clock estimation needs to consider the IFB and optimize its estimation strategy. The real-time clock is calculated by the MGEX and iGMAS tracking stations data and only costs 1.6 s of an epoch. Compared with the final precision satellite clock provided by GBM, the accuracy of GPS satellite clock is about 0.210 ns, and the GLONASS is about 0.298 ns.

Key words: GPS/GLONASS, real-time satellite clock, inter-frequency bias, fast estimation