Improved De-Aliasing for Gravity Field Modelling with GRACE

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The work proposed addresses one of the main remaining problems in the GRACE data analysis, which is the atmospheric and oceanic de-aliasing. From the current perspective this is the limiting factor for the GRACE gravity field performance and for all follow-on studies. The de-aliasing is the process to remove apparent mass variations caused by the under-sampling of the GRACE orbit and its observations. The de-aliasing can be improved in two ways. (1) The atmospheric and oceanic pressure fields required for the de-aliasing shall not be regarded as error free. For this purpose extensive analysis of the key parameters by comparison with other model data or with independent observations shall be done. Outcome of this work shall be representative error measures for the required parameters. (2) The complete sampling and aliasing model shall be better understood and the error propagation from the representative errors to the gravity field shall be developed and implemented. For the sampling and aliasing model all known mass effects as well as the orbit characteristics and available observations shall be taken into account. In a final step all results shall be taken into account for a re-computation of a homogeneous GRACE gravity field time series, which shall be used as input for subsequent studies within the priority programme.