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.