Joint SST and SGG gravity field solutions using the torus approach

Abstract

Global gravity field recovery from the dedicated gravity field satellite missions like CHAMP, GRACE and GOCE, is a computationally demanding task. This paper makes use of a torusbased “lumped coefficients” approach, which is able to deal with any geopotential functionals. Firstly, as a demonstration of its feasibility and efficiency, gravitational disturbing potentials from real CHAMP SST and simulated gravity gradient tensors from GOCE-like SGG are processed through the torus approach individually. The spherical harmonics solutions validate that SST is only sensitive to the low degrees of spherical harmonics while SGG better resolves the high degrees. Therefore, in order to cover the whole gravity spectrum, the block-diagonal order-wise normal matrices from SST and SGG data are merged in the least-squares adjustment using proper weighting factors. The optimal weighting factors will firstly be estimated by a parametric covariance method in an iterative way. We also apply the variance components estimation as an alternative method. The joint SST and SGG solutions show better performances than either one of the stand-alone inversions in the presence of full gravity field spectrum and minimization of geoid height errors.