Improved Measurement of Earth's Gravity Field

Before the launch of NASA's Gravity Recovery and Climate Experiment (GRACE) in 2002, scientists' knowledge of Earth's gravity field was based upon decades of data from geodetic satellites (left image). GRACE has allowed monthly gravity measurements that are more than 100 times more accurate than these previous models, permitting scientists to characterize how Earth's gravity field varies over time and space, as illustrated by the map on the right, produced after just 13 months of GRACE data.