PRECISION ORBIT DETERMINATION FOR THE GEOSAT FOLLOW-ON SATELLITES

The potential radial orbit accuracy of satellites in low Earth orbits has been investigated through simulation analysis and the reduced dyna mic technique. Toward that end, a simulation interface has been develo ped so that the GIPSY OASIS IP orbit determination software system may be used in simulation analyses. In simulation mode, orbits and measur ement data are generated with a given set of models, after which the s imulated data are processed with a different set of models. The result s are compared to the simulated data, and the difference is due solely to modeling differences and data noise. By introducing model errors o f appropriate size, realistic orbit error may be simulated, The simula tion technique described has been applied to the GEOSAT Follow-On and TOPEX/Poseidon satellites. The results of the study, incorporating onl y six ground station into the solution, show that radial orbit accurac y in the GEOSAT orbit will be approximately 4.3 cm rms. When the numbe r of ground tracking stations was increased to 13 and the parameters f or the reduced dynamic orbit determination technique were tuned, the r adial error was reduced from 4.3 to 3.0 cm in the GEOSAT orbit and fro m 1.9 to 1.6 cm rms in the TOPEX/Poseidon orbit.