The twin-spacecraft Gravity Recovery and Climate Experiment (GRACE) mission measures changes in the Earth’s gravity with unprecedented accuracy, providing crucial information about the distribution and transport of mass within the Earth system’s surface and deep ocean currents, surface and ground water storage, ice sheets and glaciers, and other hydrological and terrestrial features.

GRACE was launched on March 17, 2002 as a joint mission of NASA and German Aerospace Center (DLR). GRACE was selected in 1997 as second mission in NASA’s Earth System Science Pathfinder (ESSP) program. Dr. Byron Tapley was the Principal Investigator responsible for the mission. Originally planned as a 5 year mission, GRACE collected valuable data for over 15 years and finally decommissioned in 2017 due to loss in battery capacity on one of the satellites.

Over the 15 years GRACE provided scientists with unprecedented information about the Earth system. Scientists use measurements of very small changes in the separation of the two satellites in low Earth orbit to calculate local changes in gravitational field caused by mass variations in the Earth. Those measurements can, in turn, be used to track motions of water around the Earth caused by seasonal patterns and climate processes.

“Using cutting-edge technology to make exquisitely precise distance measurements, GRACE improved our scientific understanding of our complex home planet, while at the same time providing information — such as measurements related to ground water, drought and aquifer water storage changes worldwide — that was used in the U.S. and internationally to improve the accuracy of environmental monitoring and forecasts,” said Michael Freilich, then director of NASA’s Earth science division, in a statement.

CSR is the home institution of the PI of the GRACE mission, Dr. Byron Tapley. The team at CSR lead the mission design and development of the system requirements in collaboration with NASA-JPL. The team at CSR was also responsible for the science operations management and science data system for the mission.