GOCE gravity models and gravity gradient assessment

Abstract

The GOCE (Gravity field and steady-state Ocean Circulation Explorer) mission launched on 17 March 2009 provides for the first time Satellite Gravity Gradiometer (SGG) data. It is designed to recover the Earth gravity anomaly field with an accuracy of better than 1 to 2 mGal with a spatial resolution of 100 km or less. It is necessary to assess the signal and noise in the GOCE data before use. In this thesis, three GOCE global gravity field models and the gravity gradient observations of level 2 products are assessed with external gravity models and observations. Three GOCE gravity fields are the sets of spherical harmonics produced by GOCE High level Processing Facility (HPF). They are evaluated in the spectral domain globally and in an area around the Reykjanes Ridge part of the mid-ocean ridge south of Iceland. Three GOCE gravity fields are compared to the global geopotential model EGM2008 and to a state-of-the-art model based only on measurements of the GRACE satellite mission, ITG-Grace2010s. Furthermore ship gravity measurements around the Reykjanes Ridge and a simple parametric geophysical model are used. Before gravity gradient assessment, a Butterworth band-pass filter was applied to the gradiometer observations at orbit height, because of the 5-100 mHz measurement bandwidth of the GOCE gradiometer. The GOCE gravity gradient measurements of repeat tracks around Reykjanes Ridge are compared after correction from the reference gravity field model (EGM2008). The outcome of this study will be very helpful for explaining the quality of the GOCE level 2 products which will service in the fields of solid earth physics, oceanography, geodesy and glaciology.