A new global Earth gravity field model from satellite orbit perturbations for support of geodetic/geophysical and oceanographic satellite missions Reference frame and low degree gravity field solution (GRIM5 - step 1)

GFZ Potsdam and GRGS, Toulouse, are preparing in a joint effort of a new generation of Earth gravity field models called GRIM5. Based upon the analyses of gravitational induced satellite orbit perturbations, satellite tracking data obtained from numerous satellites are going to be exploited to solve simultaneously for gravitational and ocean tide potential and tracking station positions parameters. The GRIM5 task was split up into two steps. Within step1 the algorithm and software development was accomplished to establish up-to-date computational standards which considerably differ from the former GRIM4 standards. In particular, emphasize was laid on the consideration of temporal gravitational and reference system related tidal and on-tidal variations due to Earth rotation, and ocean and atmosphere dynamics. The implementation of the new computational standards was numerically validated by adjusting for a new reference frame (195 tracking station positions and velocities), low degree gravitational coefficients and selected secular rates of change, for cyclic geocentre variations and pole tide related Love numbers in a simultaneous solution derived from laser, DORIS, PRARE and GPS-SST tracking data of 9 satellites. From this solution, which is called GRIM5-Step1 and which is documented and discussed in this report, sound expertise on the treatment of satellite tracking data for precise orbit and Earth parameter recovery within the new computational and software environment could be acquired to enter into the Step2 processing for a complete GRIM5 Earth gravity field model solution. This model shall be created in preparation of the coming gravity field dedicated satellite missions, like CHAMP, and altimeter missions like Jason. (orig.)Summary in German and FrenchSIGLEAvailable from TIB Hannover: RR 6134(98/18) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany); DLR Deutsches Zentrum fuer Luft- und Raumfahrt e.V., Bonn (Germany)DEGerman