Integration of laser ranging range-rate observations into the GRACE Follow-On processing at the AIUB

We study temporal gravity field determination from GRACE Follow-On satellite-to-satellite tracking data using the inter-satellite link of the K-Band Ranging System (KBR) and kinematic positions of the satellites as observations and pseudo-observations, respectively. In addition, we introduce the range-rate observations collected by the Laser Ranging System (LRI) as further observation group. We compute our solutions with the Celestial Mechanics Approach using next to the kinematic positions either only LRI range-rate observations or combining them with the KBR derived range-rate data by the means of Variance Component Estimation (VCE). The stochastic noise of the KBR and LRI data is modelled with an empirical description of the noise based on the post-fit residuals between the final GRACE Follow-On orbits, that are co-estimated together with the gravity field, and the observations, expressed in position residuals to the kinematic positions and in KBR and/or LRI range-rate residuals. We validate the LRI-only and KBR+LRI monthly solutions by comparing them with the KBR-only derived models from the operational GRACE Follow-On processing at the AIUB, by examining the stochastic behaviour of respective post-fit residuals and by inspecting areas where a low noise is expected. Last but not least, we investigate the influence of LRI-only and KBR+LRI monthly gravity field solutions in a combination of monthly gravity fields based on other approaches as it is done by the Combination Service for Time-variable Gravity fields (COST-G) and make use of noise and signal assessment applying the quality control tools routinely used in the frame of COST-G.