One of the GRACE-FO satellites in a clean room.

GRACE Follow-On in a clean room
Image credit: Airbus DS GmbH/A. Ruttloff


Size: 10 feet, 3 inches (3.123 meters) long, 2 feet, 6.7 inches (0.78 meters) high, 6 feet, 4.5 inches (1.943 meters) wide at bottom, 2 feet, 3.3 inches (0.69 meters) wide at top

Mass: 1,323.2 pounds (600.2 kilograms) each, including onboard propellant at launch

Power: Panels of gallium arsenide solar cells mounted on satellite's top and side exterior surfaces

Batteries: 78-ampere-hour battery consisting of lithium-ion cells

Instruments: Microwave instrument, accelerometer, laser ranging interferometer (technology demonstration), laser retro-reflector

Artist's concept of GRACE-FO orbiting Earth

Illustration of GRACE-FO orbiting Earth
Image credit: NASA/JPL-Caltech


Launch: No earlier than May 19, 2018

Prime mission: Five years

Orbit altitude: Approximately 305 miles (490 kilometers)

Orbit's inclination to Earth's equator: 89 degrees (near-polar)

Orbit duration: Approximately 90 minutes

Orbits per day: Approximately 15

Velocity: Approximately 16,800 mph (7.5 km/s)

Separation between spacecraft: 137 miles (220 kilometers) optimal separation, plus or minus 31 miles (50 kilometers)


Launch is scheduled for no earlier than May 19, 2018, from Vandenberg Air Force Base, California, aboard a SpaceX Falcon 9 launch vehicle as a rideshare with five Iridium NEXT communications satellites.


NASA investment: Approximately $430 million