Space to earth geodetic observations: approaching the atmospheric effect

Abstract One of the major problems in evaluating space to Earth geodetic observations is the elimination of the atmospheric influence. Several models have been proposed and used to improve the results. For some of them, the accuracies, as about the mean error, seem to be very close to each other. The main difference comes from the parameterization of the models' variables, using geographic or atmospheric parameters, which lead to quite different rms error values. Model's variables estimated with geographic parameters show a strong dependence on atmospheric parameters. This first approach depends on the rough assumption of a homogeneous spherically stratified atmosphere, something not true. Errors coming out from this are examined in the second part of this report where the case of a 3D atmosphere is examined. Finally another task is discussed dealing with the radio source elevation angle in use. Taking into account that the radio wave bends downwards as it travels through the atmosphere, theoretically there is a possibility of an error in the radio source elevation angle used in delay mapping functions. Some results are given and the cases of GPS satellites or other possible radio sources are discussed.