Satellite Orbit Perturbations Due to the Geopotential

Satellite-borne radar altimeters have the capability of measuring the distance from the satellite platform to the ocean surface with an accuracy of five centimeters or less. To fully exploit the geophysical information contained in this data, it is necessary to have independent knowledge of the geocentric satellite distance to a comparable level of accuracy. Current altimeter satellite ephemerides fail this requirement by at least an order of magnitude. The radial errors contained in the estimated orbits are primarily a result of inadequacies in the modeling of the Earth's gravity field. To better understand the limitations this orbit error imposes on the analysis of the altimeter data, this study details the temporal and spatial characteristics of the radial orbit perturbations produced by the geopotential. The temporal description fully describes the frequency spectrum of the perturbations, and the spatial description provides a direct method for quantifying the perturbations on a geographical basis. These results are used to analyze the expected radial orbit perturbations of the altimeter satellite to be flown by the proposed TOPEX Mission. To facilitate other possible applications, the geopotential perturbations in the along-track and cross-track directions are presented also.Aerospace Engineering and Engineering Mechanic