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Abstract:
Over the last twenty years the satellite missions GRACE and GRACE Follow-On have provided a unique insight into Earth’s gravity field. A lot of effort has been and is still put into understanding the measurement data to supply the analysis with up-to-date and consistent Level-1B data products. The Astronomical Institute of the University of Bern (AIUB) has published several time series of monthly GRACE gravity fields and is currently operationally computing GRACE Follow-On gravity field models, which are incorporated into the Combination Service for Time-variable Gravity fields (COST-G). In order to bring the time series to a consistent and up-to-date level, we re-process both GRACE and GRACE Follow-On with the newest Level-1B data, incorporate the most recent AOD1B-RL07 de-aliasing models, and possibly update the ocean tides background force model. Furthermore, we revise our processing strategy for consistency and efficiency. In an attempt to come up with reasonable error estimates, we model the stochastic noise of the data with an empirical description of the noise based on the post-fit residuals between the final satellite orbits, that are co-estimated together with the gravity field, and the observations. We compare and validate the new solutions by examining the stochastic behaviour of post-fit residuals, by investigating areas where low noise is expected and by inspecting mass trend estimates. Finally, we address the influence in a combination of monthly gravity fields based on different approaches as it is done by COST-G and make use of the quality control tools used in the frame of COST-G.
