GPS Satellite Orbit Analysis Based-on IGS Precise Ephemerides

GPS satellite precise ephemerides provided by IGS describe there dimension position of GPS satellites in ITRF. This paper focuses on how to calculate GPS satellite orbit parameters through IGS data. Choosing a group of appropriate parameters, and the relationship between satellite position in ITRF and these parameters are founded, and these parameters can be estimated using some successive ephemerides. Three different methods are introduced detailedly. Because the variations of satellite orbit parameters reflect that of disturb perturbation forces, studying on the variations of satellite orbit parameters can help to find the regularity of perturbation forces.The result of this study provides a method calculating GPS satellite orbit parameters through IGS precise ephemerides. Orbit parameters of each GPS satellite at each epoch over a long period are calculated, which can be used for further research. Then some GPS satellites orbit parameters over a long time (for example, 800 days) are calculated and these parameters' regularity in terms to time is analyzed, and some primary conclusions are drawn. Parameters used in GPS broadcast ephemerides are also assessed.In chapter 2, the base knowledge of satellite is introduced. In chapter 3, GPS satellite ephemerides are discussed briefly. Then in chapter 4, the main mathematic model and three methods are introduced detailedly. In chapter 5, based on nine-parameters, orbit parameters of many satellites are calculated. Then some conclusions are drawn, and parameters used in GPS broadcast ephemerides are evaluated.