Performance assessment of the earth's gravity field models in precise orbit determination of LEO satellites

Dynamic orbit determination is the conventional technique that has been commonly used for precise orbit determination (POD) of satellites at various orbital altitudes. The performance of this technique is mainly limited by inaccurate modelling of force perturbations acting on satellites. The perturbations include the Earth's gravity field, atmospheric drag, solar radiation pressure etc. Due to the fact that low Earth orbit (LEO) satellites are highly sensitive to the Earth's gravity field, the accuracy of the gravity field model used in the dynamic POD technique directly affects the accuracy of POD of LEO satellites. Therefore, selection of an accurate gravity field model for improving the POD accuracy plays a significant role in meeting the stringent requirements of space applications such as radio occultation, remote sensing and altimetry. Nowadays, with the successful launches of the CHAMP,GRACE and GOCE gravity missions, various high accuracy gravity field models have been developed and made publicly available at the International CentreIn this study, the performance of13 selected gravity models applied in the dynamic POD was assessed using space-borne dual-frequency GPS measurements from the twin GRACE satellites during the period from 1st to 31st March 2008, and the effects of time-varying low-degree spherical-harmonic coefficients20C,30C and40Con POD for the twin GRACE satellites were also analysed. The results of tracking data residuals, orbital overlap, external orbit comparison and independent satellite laser ranging (SLR) validation demonstrated that the highest POD accuracies of GRACE-A and -B are about 2.1 cm and 2.7 cm with respect to SLR measurements respectively and this is achieved using those combined models ,i.e. EIGEN-51C, GO_CONS_GCF _2_DIR_R3, andGOCO03S.