GRACE (Gravity Recovery and Climate Experiment) maps variations in Earth's gravity field. GRACE consists of two identical spacecraft that fly about 220 kilometers (137 miles) apart in a polar orbit 500 kilometers (310 miles) above Earth. GRACE maps Earth's gravity field by making accurate measurements of the distance between the two satellites, using GPS and a microwave ranging system. It is providing scientists from all over the world with an efficient and cost-effective way to map Earth's gravity field with unprecedented accuracy. The results from this mission are yielding crucial information about the distribution and flow of mass within Earth and its surroundings.
The gravity variations studied by GRACE can be used to determine ground water storage on land masses. By comparing current data to an average over time, scientists can generate an anomaly map to see where ground water storage has been depleted or increased.
GRACE is a joint partnership between the National Aeronautics and Space Administration (NASA) in the United States and Deutsche Forschungsanstalt für Luft und Raumfahrt (DLR) in Germany. Project management and systems engineering activities are carried out by the Jet Propulsion Laboratory.