The Fast Analysis of the GOCE Gravity Field

The semi-analytical (SA) approach is proposed for the fast determination of gravity field from the GOCE (Gravity Field and steady-state Ocean Circulation Explorer) observations. In this paper, we discuss the principle and the characteristics of the SA approach in detail, and point out that based on the application of FFT and the introduction of the nominal orbit (circular, exact repeat orbit, uninterrupted measurement time series, and constant inclination), the SA approach can effectively recover the potential coefficients from large observations. This method can give a fast diagnosis of the GOCE system performance in parallel to the running of the GOCE mission by comparing the estimated noise characteristics of the SGG (Satellite Gravity Gradiometry) time series with the gradiometer error PSD (Power Spectrum Density) (prior). The performance of this method is evaluated using the simulated observations generated in different cases (ideal and practical). The results in this paper show that this method can be applied to the practical cases of non-circular, non-repeat orbits and non-constant inclination in the time series of observations by the iteration algorithm which can eliminate or weaken the approximate errors in the observation model. The test examples show that to recover the high degree gravity field model, the optimal regularization parameter should be selected in the Kaula regularization technique.