Various approaches for gravity field recovery by using the GOCE satellite orbits

The energy conservation approach has been adopted to exploit GOCE orbit information in earlier GOCE time-wise and space-wise gravity field models which are two kinds of official ESA products, but the accuracy of long-wavelength gravity signal is low. Gravity field recovery with GOCE satellite data is an ill-posed problem and the precision of zonal coefficients is low due to the polar gaps, which needs be processed by regularization technique. This paper analyzes the accuracy of existing approaches for gravity field recovery in processing GOCE data and the selection of optimal regularization techniques and parameters. Several gravity field models were recovered based on GOCE precise orbits of 92-days from 2009-11-01 to 2010-01-31 with the energy conservation approach, short-arc integral approach and average acceleration approach. These approaches do not require any initial values of unknown parameters and reference gravity models. Besides, the Tikhonov regularization technique was applied to tackle the ill-posed problem. The results show that the highest accuracy of the model is recovered by the average acceleration approach, the lowest accuracy is the energy conservation approach, and the accuracy of short-arc integral approach is slightly worse than average acceleration approach. Therefore, such methods as the average acceleration approach or short-arc integral approach should be recommended to be applied when processing the GOCE orbit data. Gravity field models can effectively recovered by GOCE orbit data with the order and degree 120 when orbit and gradiometer data are combined to processes in the future. Kaula regularization and second-order Tikhonov (SOT) are superior to other regularization techniques in dealing with ill-posed problem of GOCE, and the corresponding optimal regularization parameters of both techniques are consistent. However, the effects of polar gaps could not be completely inhibited by regularization technique; it should be combined with other data, such as GRACE satellite data, to get the desired results. ©, 2015, SinoMaps Press. All right reserved.