COST-G: The new International Combination Service for Time-variable Gravity Field Solutions of the IAG/IGFS

COST-G is the new combination service for time-variable gravity field solutions of the International Association of Geodesy (IAG). In the frame of COST-G monthly GRACE (and in the future GRACE-FO) gravity fields of all associated analysis centers undergo
- strict quality control to guarantee correct signal content,
- careful noise assessment to derive relative weights,
- combination on normal equation level to correctly consider all correlations,
and
- transformation of the combined gravity fields into user-friendly L3-products, to provide to the users unique, robust and reliable gravity field solutions that profit from reduced noise compared to the individual contributions.
We apply the mechanisms of quality control and noise assessment of COST-G to the new GRACE-RL06 time-series and compare to RL05 and to alternative time-series provided in the frame of the European Gravity Service for Improved Emergency Management (EGSIEM).