GPS PRECISE TRACKING OF TOPEX POSEIDON - RESULTS AND IMPLICATIONS/

A reduced dynamic filtering strategy that exploits the unique geometri c strength of the Global Positioning System(GPS) to minimize the effec ts of force model errors has yielded orbit solutions for TOPEX/POSEIDO N which appear accurate to better than 3 cm (1 sigma) in the radial co mponent. Reduction of force model error also reduces the geographic co rrelation of the orbit error. With a traditional dynamic approach, GPS yields radial orbit accuracies of 4-5 cm, comparable to the accuracy delivered by satellite laser ranging and the Doppler orbitography and radio positioning integrated by satellite (DORIS) tracking system. A p ortion of the dynamic orbit error is in the Joint Gravity Model-2 (JGM -2); GPS data from TOPEX/POSEIDON can readily reveal that error and ha ve been used to improve the gravity model.