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The first ESA Earth Explorer Core Mission GOCE (Gravity Field and Steady-State Ocean Circulation Explorer) entered the operational measurement phase in September 2009. Before gravity field processing, the quality of the GOCE gradients in the measurement bandwidth (5-100 mHz), MBW, has to be assessed. Here, two procedures have been developed in Hanover, the mutual comparison and analysis of observed gradients in satellite track crossovers and the application of terrestrial gravity data which are upward continued and transformed into reference gradients for the GOCE gradiometer measurements. First the gravity gradients are filtered, where the longer wavelength signals below the MBW are replaced by global geopotential model (GPM) information. The filtered time series is used as input signal for both validation methods. 1

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Abstract. The accuracy and spatial resolution expected from GOCE gravity gradiometry might deteriorate due to temporal gravity variations, which are mainly induced by mass redistributions in the System Earth. These mass redistributions occur in the atmosphere at various time scales, in the oceans as ocean tides and currents and on the continents as solid Earth tides, loading and hydrological effects. Opposite to GRACE, GOCE is developed to measure the static gravity field. Therefore, any time variable effects have to be removed from the measured data prior to further processing in a dealiasing step. In this report the effects mentioned above are analysed by means of available models in order to investigate if they deliver significant contributions to the GOCE gradiometer measurements. Simulations of the different system parts (Atmosphere, Hydrosphere, Cryosphere and Solid Earth) are run. The gravitational effect of the simulated mass changes is expanded into spherical harmonics from which gravitational gradients are computed along a simulated GOCE orbit. The resulting gradients are compared with the specifications of the GOCE gradiometer. Furthermore, the residual (i.e. atmospheric and oceanic parts removed) time variable part of the gravity field as detected by GRACE is discussed with respect to its impact on GOCE gradiometry.