CHAMP rapid orbit determination for GPS atmospheric limb sounding

Abstract

In preparation of the CHAMP small satellite LEO (Low Earth Orbit) mission to be launched on July 15, 2000, the GeoForschungsZentrum Potsdam (GFZ) enhanced its high precision orbit determination capabilities in order to rapidly produce precise LEO and GPS (Global Positioning System) orbital products. These orbits shall be available at 3 hour intervals with a latency of 2 hours after the actual observation for the application of GPS atmospheric limb sounding. Rapid orbit determination will exploit spaceborne GPS high-low satellite-to-satellite tracking data, fast delivery GPS ground tracking data from a global network and on-board accelerometer data for surface force modelling. Rapidly available ground based laser ranges support the orbit determination task. Because of the timeliness requirements of the orbital products, the availability of input data in space and time for POD may be sub-optimal. It is planned to apply dynamic orbit integration and an either separate or combined adjustment for CHAMP and GPS satellites' routine rapid orbit determination. For quality control purposes and during the initial mission phase, when the available force models, in particular the gravity field model, are not accurate enough, the CHAMP orbit can also be computed in a purely kinematic/geometric approach not using any dynamical model.