An assessment of new satellite total density data for improving upper atmosphere models

The DTM series of atmospheric density models (Barlier et al., 1977; Berger et al., 1998) have been developed for atmospheric constituent representatio n and precise orbit computation. They are based upon satellite drag total d ensity data which are implicitly averaged over one or more days. Our approach consists of refining the computation of the density model coef ficients with more precise orbit computation, using the information contain ed in the tracking data. Satellite Laser Ranging (SLR) in case of Starlette (800 km) and GFZ-1 (380 km), Doppler-DORIS in case of SPOT? (800 km). This has been verified by comparison of the new density values to Dynamic E xplorer 2 (DE-2) measurements, as well as by precise orbit computation. In both cases, an improvement of a few percent has been achieved, showing the interest of the method. This study has been done in preparation for the new accelerometric mission CHAMP for which we prepare a new gravity field (GRIM5) using the orbit pert urbation technique, as well as an improved density model, hence improving t he drag modeling. (C) 1999 Published by Elsevier Science Ltd. All rights re served.