Gravity Model TUM-2Sp Based on the Energy Balance Approach and Kinematic CHAMP Orbits

We have used one year of CHAMP data for deriving a gravity field model based on the energy balance approach. In order to avoid the use of any a priori gravity information, purely kinematic orbits have been computed from GPS measurements only. Subsequently velocities have been derived from these kinematic positions by two different methods, namely smoothing splines and Newton- Gregory interpolation. Using the principle of energy conservation, the satellite's positions and velocities are transformed into gravitational potential. CHAMP onboard micro-accelerometry is used to correct for surface forces. For spherical harmonic analysis the so-called direct approach has been implemented using the full normal equation matrix. The model, called TUM2Sp, was found to be a more accurate gravity field than EIGEN-2 model.