Objectives At present, low earth orbit (LEO) satellites with missions, such as LEO navigation enhancement, earth observation and scientific application, require higher accuracy and real-time performance of orbit parameters. Because of the limitations of GPS broadcast ephemeris errors, the accuracy of traditional real-time orbit determination using space-borne GPS measurements is still a long way to catch up with real-time centimeter-level orbit demand. The use of real-time orbit and clock corrections for precise positioning applications will be extended into orbit if they are available via a satellite link to geostationary orbit(GEO) satellites. However, the data link to GEO constellation may not be available over the polar regions.
Methods The centimeter-level real-time precise orbit determination (RTPOD) method using space-borne GPS measurements with international global navigation satellite system service real-time service (IGS-RTS) data receiving interruption in the polar regions is studied. Firstly, the characteristics of ephemeris comprehensive errors caused by real-time corrections and its short-time extrapolation are analyzed. Based on the analysis, a pseudo-ambiguity is modeled as a stochastic process with piecewise random walk and estimated in the mathematical model of RTPOD to reduce the ephemeris comprehensive error, and then the centimeter-level accuracy can be realized. Finally, using GPS broadcast ephemeris and IGS-RTS products(CLK93), the onbroad RTPOD data processing for one week GPS measurements from the GRACE C satellite is simulated by the SATODS software.
Results The experimental results show that, considering the receiving interruption of real-time corrections in polar regions, the position and velocity accuracies are 7.04 cm and 0.20 mm/s, respectively.
Conclusions The proposed method is feasible and effective.