Over 25 Years of International Cooperation of Gravity Missions: Past, Present, Future

The GRACE and GRACE-FO Earth missions, launched in 2002 and 2018 respectively, enable monitoring of global mass changes with far-reaching impact on our understanding of Earth's changing water distribution (surface and ground water over land, glacier melt, and sea level change). The nearly continuous monthly data from these satellite gravity missions, through the international partnership and cooperation between NASA/JPL, GFZ, DLR, Airbus, and ONERA (The French Aerospace Lab), provide the science communities with unique and highly valuable observations of Earth's changing water cycle and climate system, which is now in its 3<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rd</sup> decade. Increasingly, this unique knowledge is informing decisionmakers and stakeholders for managing vital water resources sustainably and assessing climate risks, in support of NASA's Earth Science to Action strategy. Identified as a Designated Observable in the 2017 Decadal Survey, the continued observations of Mass Change will be achieved by the NASA-DLR partnership on the forthcoming GRACE-Continuity mission, currently in implementation and scheduled for launch in December 2028, to continue this cornerstone climate measurement. Just like the previous GRACE missions, GRACE-Continuity (GRACE-C) builds on successful past partnerships with NASA/JPL, GFZ (German Research Center for Geoscience), DLR (German Aerospace Center) and ONERA (French Aerospace Lab), to ensure mission success with a fast-paced schedule and minimum cost impact to NASA. GRACE-C entered Phase C in May of 2024, after completing the System Requirements Review, Mission Design Review and Preliminary Design Review within the previous 12 months.