Second release of combined monthly gravity fields of the GRACE and GRACE-FO satellite missions in spherical harmonic representation (Level-2 product) generated by the Combination Service for Time-variable Gravity Fields (COST-G; Jäggi et al., 2020), a product center for time-variable gravity fields of IAG's International Gravity Field Service (IGFS).

COST-G RL02 is a combination of gravity field time series provided by the following analysis centers (ACs) and partner analysis centers (PCs) of COST-G:

ACs:
- GFZ Helmholtz Centre for Geosciences: GFZ RL06 (GRACE), GFZ RL06.3 (GRACE-FO)
- Graz University of Technology, Institute of Geodesy: ITSG-Grace2018 (GRACE), ITSG-Grace_op (GRACE-FO)
- Centre National d’Etudes Spatiales, Groupe de Recherche de Geodesie Spatiale: CNES_GRGS_RL05_CHOL (GRACE & GRACE-FO)
- Astronomical Institute University of Bern: AIUB-RL03 (GRACE), AIUB-GRACE-FO_rl02op (GRACE-FO)
- Leibniz Universität Hannover: LUH-GRACE-2020 (GRACE), LUH-GRACE-FO-2020 (GRACE-FO)
- Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences: APM-SYSU (GRACE)
- HuaZhong University of Science and Technology: HUST-Grace2024 (GRACE & GRACE-FO)
- Southern University of Science and Technology, Department of Earth and Space Sciences: SUSTech2025 (GRACE)
- Tongji University, College of Surveying and Geo-informatics: Tongji-Grace2022 (GRACE)

PCs:
- Center for Space Research at University of Texas: CSR RL06 (GRACE), CSR RL06.3 (GRACE-FO)
- NASA Jet Propulsion Laboratory: JPL RL06 (GRACE), JPL RL06.3 (GRACE-FO)

Version History:

4 July 2025:
Release of Version 2.1. This is an update of Version 2.0 of the same data set including the following changes: Replacement of Tongji-Grace-Costg (nonofficial release) by Tongji-Grace2022; replacement of HUST-Grace2023 (nonofficial release) by HUST-Grace2024 (currently also not yet officially released); use of GFZ RL06.3, CSR RL06.3, JPL RL06.3 and CNES_GRGS_RL05_CHOL for the entire GRACE-FO period.

25 April 2025:
Initial release of the data (Version 2.0).

COST-G performs a harmonization and quality control of the individual input solutions of the COST-G ACs and PCs. The combination of COST-G GRACE RL02 is then performed applying variance component estimation on the solution level, where only coefficients up to order 60 are considered for the derivation of the relative weights (Meyer et al, 2024). The resulting COST-G RL02 combined gravity fields are validated assessing their signal and noise content in the spectral and spatial domain (Meyer et al., 2024) and by the COST-G Product Evaluation Group (PEG).