GRACE-FO successfully completed its five-year prime mission phase in May 2023, and is currently in its extended mission phase.

Together, the GRACE and GRACE-FO multi-decade data records provide foundational observations of monthly to decadal global mass changes and transports in the Earth system, derived from temporal variations in the Earth’s gravity field.

In parallel, a continuity mission called GRACE-Continuity (GRACE-C), scheduled for launch in 2028, is being developed in partnership between NASA (US) and DLR (Germany). While its design heavily leverages heritage elements, one notable departure is that the primary ranging instrument on GRACE-C will be a higher-precision laser interferometer, capitalizing on the successful demonstration of this technology on GRACE-FO.

All GRACE missions consist of two identical satellites that act in unison as a single primary instrument. The two satellites comprising each mission orbit one behind the other in the same orbital plane, maintaining an approximate distance of 220 km (137 miles).

As the pair circles the Earth, areas of varying gravity cause the distance between the two satellites to fluctuate ever so slightly. This variation is continuously measured by precise onboard intersatellite ranging instruments (GRACE: Microwave; GRACE-FO: Microwave and Laser; GRACE-C: Laser). The distance variations are measured with an accuracy of a few micrometers (Microwave), or even nanometers (Laser). Additional instruments measure satellite attitude, non-gravitational forces, and precise orbital position. These observations are then processed on the ground to map Earth’s month-to-month gravity and mass changes.