Analysis of the effect of gravity field models on precise orbit determination of Swarm satellites

In order to obtain the precise orbits of the Swarm satellite, the satellite-borne GPS data and reduced-dynamic orbit determination method are adopted, and the pseudo-stochastic pulse parameters are introduced into the equation. The influence of GOCO06s Earth gravity field model with different degree on the accuracies of the solved orbits for Swarm satellite are analyzed in detail, and the orbit accuracies of Swarm satellite are investigated and compared using PGM2000a, EIGEN-2, EGM2008 and GECO gravity field models with 100 degree. The results show that when the degree of GOCO06s gravity field model increase between 30 and 100, the orbit accuracies of Swarm-A, Swarm-B and Swarm-C satellite in radial, tangential and normal directions will be higher and higher. However, when the degree is higher than 100, the orbit determination accuracy is basically stable, and the orbit determination accuracy is better than 3 cm in all directions. In addition, the EGM2008, GECO and EGM2008 GOCO06s models with 100 degree are used to determine the orbit of three Swarm satellites. The orbit accuracy of the solutions is equivalent and higher than that of other gravity field models of the same degree.