Orbit determination requirements for Topex

The orbit determination requirements for the Ocean Topography Experiment (Topex/Poseidon) are discussed. A radial orbit accuracy of 13 cm for a period of three to five years is required for the mission. The factors which limit the orbit accuracy for the geopotential, the solar radiation pressure, and the atmospheric drag model are examined. Also, the effects introduced by variations with aspect angle in the spacecraft area-to-mass ratio are considered.