The Research And Program Design Of GPS Satellite Orbit Determination Based On Ground Reference Station Observation

Satellite orbit determination is the core to determine the security and the availability ofsatellite system. So it has become a research hotspot in the field of satellite navigation.Especially at present, China is building our BDS global satellite navigation system. How toaccurately and quickly obtain a high-precision orbit has also become a serious problem. Theprecision orbit determination technology of GPS and other satellite navigation systems isrelatively mature, but due to the different characters of constellation、a small number ofreference stations、can not be globally distributed and many other factors, the currentrelatively lower accuracy of the BDS global satellite navigation system is difficult to meet thedemand of high-precision real-time positioning and navigation.As the world’s most widely used satellite navigation system, GPS’s orbit accuracy canreach2cm.Because the reference stations of the GPS are all around the world, we can takeadvantage of the GPS to study the precise orbit determination theory and analysis the impactof the number and distribution of reference stations to the satellite orbit. Then conclusion putforward the improved orbit determination method and conclusion analysis the referencestations’ influence on the precision orbit determination and expand into the orbitdetermination research of our own BDS global satellite navigation system. This paper beginswith the basic theory of satellite orbits, then has a detailed analysis of the impact of thenumber and distribution of the reference stations to the satellite ephemeris and real-timeephemeris solver. Based on the relevant theory and research, I designed an orbit integrationprocess. Specific researches are as follows:(1) Based on the satellite orbit determination theory and research methods, usingdifferent numbers of regional stations to improve the broadcast ephemeris, and getting theresult of20cm-30cm. Then using different numbers of global stations to improve thebroadcast ephemeris, and getting the result of centimeter-level.(2) Using the real-time data of the regional and global reference stations to constrain thesatellite orbit. The results showed that the accuracy of the real-time orbit with the data ofreference stations improves significantly in most of the time, but there is a great volatility in the initial period of time.(3) Imitating analytic center and using three days as an arc to solve the rapid andultra-rapid ephemeris continuously for one month. Then getting the rapid ephemeris whichhave a delay for one day and the ultra-rapid ephemeris. The ultra-rapid ephemeris updatesevery6hours, and attaches the real-time data constraints. The results showed that the rapidephemeris’s accuracy is around6.8cm and the ultra-rapid ephemeris’s precision remain lessthan20cm except for a few outliers.(4) Using seven days as an arc to solve the afterwards ephemeris. The results showedthat the radial accuracy is about3cm and it is superior to the shorter arcs solution. But thealong accuracy and the cross accuracy are lower.(5) Based on GPS satellite orbit determination research foundation, using theexperimental data of BDS navigation system to calculate the orbit. Results show that theGEO satellite orbit determination’s result is128.9cm, IGSO satellites orbit determination’sresult is36.9cm. And GEO satellites make the accuracy of IGSO satellites orbitdetermination reduce when they calculate together.(6) Based on the foregoing theories and research, I prepared the core part of orbitintegration of software modules. The results showed that the designed orbit integrationprogram can complete orbit integration process well. After one day’s orbit integration, theaccuracy of the entire constellation is roughly about20cm.