IMPROVEMENT OF THE EMPIRICAL THERMOSPHERIC MODEL DTM - DTM94 - A COMPARATIVE REVIEW OF VARIOUS TEMPORAL VARIATIONS AND PROSPECTS IN SPACE GEODESY APPLICATIONS

The Drag Temperature Model (1978) has been improved to respond better to the actual requirements of space geodesy, especially under extreme solar and geomagnetic conditions. Extended data and an improved algori thm have been considered, leading to valuable improvements. Temporal v ariations of temperature of the thermopause, total density and :major chemical constituent density are reviewed and compared to the DTM94, D TM78 and MSIS86 models. A comparison with data is performed, giving th e mean ratios between observed and model values with their root mean s quares for different physical and geometric conditions. This compariso n is made for the three models and includes data used in the modelling as well as external data. The limits of the thermosphere modelling ar e discussed.