The Gravity Recovery and Climate Experiment (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 [Tapley et al., 2004].

The LAser GEOdynamic Satellite (LAGEOS) was designed by NASA and launched May 4, 1976. It was the first spacecraft dedicated exclusively to high-precision laser ranging and provided the first opportunity to acquire laser-ranging data that were not degraded by errors originating in the satellite orbit or satellite array. LAGEOS-2, based on the original LAGEOS design, was built by the Italian Space Agency and launched on October 22, 1992.