Jason-1 precision orbit determination using GPS combined with SLR and DORIS tracking data
Jason-1, a follow-on altimeter mission to the TOPEX POSEIDON (T/P) mission, carries receivers for DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite), SLR (Satellite Laser Ranging) and GPS (Global Positioning System) in support of the Precision Orbit Determination (POD) function. The radial orbit accuracy of the Jason-1 is expected to be 2 cm RMS or better in dynamic approach with the objective of achieving an accuracy of 1 cm RMS through the improved dynamic models and measurement models. This will require significant improvement in current knowledge of surface force effects as well as improvement in knowledge of gravity field model. Jason-1 orbits were computed with various combinations of three different types of tracking data to investigate the contribution of each tracking system to the accuracy of orbits. The GPS tracking data were analyzed and utilized for POD with the DORIS and SLR tracking data using a dynamical approach. Parameterization related to empirical acceleration and antenna phase center was studied, and optimal relative weighting for each tracking system was examined. The effect of ground station selection on the orbit accuracy was also studied and a method of an optimal network selection was developed. The orbit quality tests were performed through the analysis of tracking residuals SLR residuals with high-elevation passes, orbit overlap comparisons, and altimeter crossover analysis. The study showed that the contribution of GPS tracking is significant to the improvement of orbit accuracy, especially when GPS tracking is supported by SLR tracking. The SLR residual RMS test, which is an independent and absolute measure of the radial orbit error, clearly indicates that we are approaching the 1-cm radial orbit accuracy for Jason-1.