Gravity Recovery and Climate Experiment

Gravity Recovery and Climate Experiment (GRACE), U.S.-German Earth-mapping mission consisting of twin spacecraft GRACE 1 and 2 (nicknamed Tom and Jerry after the cartoon characters). GRACE 1 and 2 were launched on March 17, 2002. By tracking the precise distance between the two spacecraft and their exact altitude and path over Earth, scientists could measure subtle variations in Earth’s gravitational field and detect mass movements due to such natural activity as sea level changes, glacial...