Improvement in the radial accuracy of altimeter-satellite orbits due to the geopotential

The application of satellite altimetry in geosciences needs a precise computation of the orbit positions of the satellites with altimeters. In particular the knowledge of the radial orbit error is of high interest in this context. Rosborough's theory [Rosborough, G.W., 1986 Satellite Orbit Perturbations due to the Geopotential, CSR-86-1 rep., Center for Space Research, Univ. of Texas, Austin.], ammended by our newer works, describes Earth static gravity induced radial orbit error as a function of latitude, longitude and pass direction. Using this theory applied to precise long-term measurements of crossover altimetry we demonstrate the improvement in the accuracy of the orbit radius due to Earth gravity models, from the early 1980s (order of tens of meters), to the present (order of centimeters and less). The early models, with higher correlations between potential coefficients, show strong variations of the error in longitude as well as latitude, compared to the more recent fields. Currently the static gravity errors in the best of the Earth models are believed to be below the systematic environmental errors in the long-term altimetry.