Observed orbit perturbations of the near-Earth orbiting satellite CHAMP are analysed to recover the long-wavelength features of the Earth's gravitational potential. More precisely, by tracking the low-flying satellite CHAMP using the high-flying satellites of the Global Positioning System (GPS) the kinematic orbit of CHAMP is obtainable from GPS tracking observations, i.e. the ephemeris in Cartesian coordinates in an Earth-fixed coordinate frame (WGS84) becomes available.
In this study we are concerned with two tasks: first we present new methods for pre-processing, modelling and analysing the emerging tracking data. Then, in a first step we demonstrate the strength of our approach by applying it to simulated CHAMP orbit data. In a second step we present results obtained by operating on a data set derived from real CHAMP data.
The modelling is mainly based on a connection between non-bandlimited spherical splines and least-square adjustment techniques to take into account the non-sphericity of the trajectory. Furthermore, harmonic regularization wavelets for solving the underlying satellite-to-satellite tracking (SST) problem are used within the framework of multiscale recovery of the Earth's gravitational potential leading to SWITCH-03 (Spline and Wavelet Inverse Tikhonov regularized CHamp data). Further we show how regularization parameters can be adapted adequately to a specific region thereby improving a globally resolved model. Finally we compare the developed model with the EGM96 model, model UCPH2002_02_0.5 from the University of Copenhagen and the GFZ models EIGEN-1s and EIGEN-2.
