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Zusammenfassung:
The GRACE and GRACE-FO missions have been fundamental in establishing a near-continuous time series of global mass transport since 2002. However, gravity field recovery using these mission data includes errors limiting the spatial and temporal resolution of gravity field solutions. The primary error contributions arise from instrument noise, temporal aliasing errors, uncertainties in the de-aliasing models, and imperfect ocean tide models. Particularly the latter will remain a limiting factor in determining high-resolution gravity fields from Next-Generation Gravity Missions.The topic has been investigated within the DFG research unit NEROGRAV and ESA´s Third Party Mission Program. One of the projects concerns stochastic modeling of ocean tide background models utilizing covariance information for eight major tidal constituents. The repeatable pattern of the tidal signal enables the extraction of uncertainty information by an ensemble of different ocean tide models. This information is introduced into the gravity field recovery process as a covariance matrix while expanding the parameter space by additional tidal parameters.An overview is provided of the recovered monthly gravity fields from GRACE/GRACE-FO when applying this covariance information. Additionally, realistic simulations have been performed for GRACE-like and MAGIC constellations to assess the impact that covariance information has on tidal errors and tidal constituents which have been co-estimated over one year and used to generate an improved ocean tide model for gravity field recovery. It is shown that the application of ocean tide covariance information contributes to the reduction of temporal aliasing caused by the mismodeling of ocean tide background models.
