Global geopotential modelling from satellite-to-satellite tracking
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Date
1981-10
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Publisher
Ohio State University. Division of Geodetic Science
Abstract
The error analysis of the global modelling of the geopotential has been carried out up to degree and order 331 of the spherical harmonic expansion, for data from a low-low satellite-to-satellite tracking (SST) mission. The sphericity and the rotation of the Earth have been considered, as well as the discrete nature of the data, assumed to consist of time averages of the measured range-rate sampled at regular intervals. The expansion of the potential has been truncated at degree n = 331, because little information on higher degrees is likely to be present in the data. Two theories have been used: that of least squares adjustment, and that of least squares collocation; above degree n = 200 the accuracies predicted according to collocation are significantly better than those according to least squares. In this report there is also a discussion on how to process SST data to obtain very high resolution models of the gravitational field. Descriptions and listings of computer programs are included. To reduce the computer time and storage needed to set up and to invert the normal matrix, a somewhat simplified orbital geometry and an approximate model of the data have been adopted; no orbit determination errors have been considered. Some arguments are given to justify these shortcuts, which may not affect seriously the validity of the results. An extention of the theory to non-polar orbits is given. [Full text of abstract available in document.]