GRACE-C

GRACE-C [Astrium]

NASA's and GFZ's GRACE-C (Gravity Recovery And Climate Experiment - Continuty) mission is the successor to the GRACE-FO mission to provide month-to-month changes of Earth's gravity field to track water movement and surface mass changes across the planet, monitoring variations in ice sheets, glaciers, underground water storage, soil moisture, and sea levels..

Similar to the two previous GRACE-series missions, the GRACE-C science and applications objectives are achieved by continuously tracking small distance variations between twin satellites flying in formation around Earth in a co-planar polar orbit at an initial altitude of 500 km, separated by approximately 220 kilometers. These data are combined with observations of non-gravitational forces acting on the satellites and their orientation and position in inertial space to infer Earth’s varying gravity field and mass redistribution. Each satellite carries geodetic quality Global Navigation Satellite System (GNSS) receivers, attitude determination sensors, a laser ranging interferometer (LRI) for satellite distance change measurements, high accuracy accelerometers, and laser retro-reflectors for orbit determination. The LRI was first successfully demonstrated on GRACE-FO, and improves the precision of the distance fluctuation measurements by a factor of more than 20-30 over the previously used microwave instruments on GRACE and GRACE-FO. The LRI on GRACE-C will feature additional redundancy.

The GRACE-C satellites are essentially repeats of the GRACE-FO spacecrafts with updated avionics.

Launch of GRACE-C is scheduled for December 2028 from Vandenberg Space Force Base in central California, aboard a SpaceX Falcon-9 v1.2 (Block 5) launch vehicle. GRACE-C is planned to collect data for at least 5 years.