Determination of non-gravitational accelerations from GPS satellite-to-satellite tracking of CHAMP

Extensive recovery experiments based on real CHAMP GPS satellite-to-satellite tracking (SST) data show that instead of directly measuring non-gravitational accelerations using an onboard accelerometer, it is also possible to derive these accelerations indirectly from GPS SST observations. The recent gravity field model improvements from the CHAMP and GRACE missions contribute significantly to a more accurate recovery. Using the first published GRACE models, non-gravitational along-track accelerations were recovered with a precision better than 10% of the total signal at a time resolution of 1 min. The quality of the recovered accelerations depends strongly on proper regularisation of the associated normal equations. The possibility of using overlap analysis for deriving the regularisation parameters was assessed, indicating that for the moment this method is sub-optimal.