GRACE Follow-On

GRACE Follow-On
Name	GRACE Follow-On
Mission type	Earth science, geodesy
Operator	NASA, Deutsches Zentrum für Luft- und Raumfahrt, Jet Propulsion Laboratory
Launch date	2018-05-22
Launch vehicle	Falcon 9
Launch site	Vandenberg Space Force Base
Orbit type	Low Earth orbit
Inclination	89°
Mission duration	2018–present (operational)

GRACE Follow-On

GRACE Follow-On is a twin-satellite Earth-observation mission that continues the gravimetric record begun by Gravity Recovery and Climate Experiment and extends measurements of Earth's time-variable gravity field. The mission, led by NASA and Deutsches Zentrum für Luft- und Raumfahrt, pairs closely with institutions such as Jet Propulsion Laboratory and builds on techniques developed at Massachusetts Institute of Technology and University of Texas at Austin. It provides key data for studies involving Intergovernmental Panel on Climate Change, National Oceanic and Atmospheric Administration, European Space Agency, United Nations Environment Programme, and national research programs.

Mission overview

The mission uses a dual-satellite configuration to measure subtle changes in Earth's gravity caused by mass redistribution related to Antarctic ice sheet, Greenland ice sheet, continental water storage, and ocean circulation phenomena including El Niño–Southern Oscillation and North Atlantic Oscillation. Designed as a follow-on to the Gravity Recovery and Climate Experiment, the project was proposed within the NASA Earth Science Division and coordinated with agencies like German Aerospace Center and academic groups at University of Bonn and University of Colorado Boulder. Its science objectives complement programs such as Gravity Field and Steady-State Ocean Circulation Explorer and feed assessments by the Intergovernmental Panel on Climate Change and regional bodies such as Arctic Council.

Spacecraft and instruments

Each spacecraft carries a microwave ranging system derived from prototypes tested at Jet Propulsion Laboratory and a technology demonstration laser interferometer developed in collaboration with Deutsches Zentrum für Luft und Raumfahrt and laboratories at University of Bremen and Stanford University. The microwave instrument is an evolution of hardware used on CHAMP (satellite) and GRACE. The payload suite includes GPS receivers sourced from suppliers with heritage from TOPEX/Poseidon and Jason-3, star trackers with lineage tracing to Hubble Space Telescope flight hardware, and accelerometers based on designs from GRACE and GOCE. Onboard systems rely on avionics practices validated by missions like Landsat 8 and Terra.

Launch and operations

Launched by SpaceX aboard a Falcon 9 rocket from Vandenberg Space Force Base, the mission entered a near-polar, low Earth orbit similar to that of its predecessor. Mission operations are managed jointly by flight teams at Joint Space Operations Center, NASA Goddard Space Flight Center, and control centers at German Space Operations Center. Routine calibration activities referenced models from JPL, GFZ Potsdam, and academic partners at Massachusetts Institute of Technology; contingency responses adapted procedures from NOAA and European Commission programs. Regular track maintenance, attitude control, and inter-satellite distance maneuvers were executed following standards established by International Telecommunication Union coordination and automated systems influenced by Deep Space Network practices.

Science goals and results

Primary science goals include quantifying temporal variations in terrestrial water storage, ice mass balance over Antarctica and Greenland, and observing ocean bottom pressure related to currents like the Gulf Stream and Kuroshio Current. Early results confirmed trends reported by IPCC assessments and regional studies from National Snow and Ice Data Center and International Arctic Science Committee. The laser-ranging demonstrator yielded instrument performance data of interest to teams at Max Planck Institute for Solar System Research, California Institute of Technology, and ETH Zurich. Studies using the data have been published by researchers at University of California, Irvine, University of Toronto, Potsdam University, and Columbia University and cited in reports by World Meteorological Organization and United Nations Office for Disaster Risk Reduction.

Data processing and applications

Processing pipelines run by science centers at University of Bonn, GFZ Potsdam, NASA Jet Propulsion Laboratory, and Earth System Research Laboratory generate gravity field solutions, time-variable mass change maps, and anomaly products used by hydrologists, glaciologists, and oceanographers. Data assimilation into models at European Centre for Medium-Range Weather Forecasts, NOAA Geophysical Fluid Dynamics Laboratory, and NASA Goddard supports improved seasonal forecasts, drought monitoring for agencies like U.S. Department of Agriculture, and sea level budgets used by Intergovernmental Panel on Climate Change. Applied uses include groundwater storage assessments for ministries in India, Netherlands, and Brazil, flood risk evaluation for United Nations Office for Disaster Risk Reduction, and coastal planning informed by National Oceanic and Atmospheric Administration.

International collaboration and legacy

The mission exemplifies multinational cooperation among agencies such as NASA, Deutsches Zentrum für Luft und Raumfahrt, European Space Agency, Canadian Space Agency, and academic partners across Germany, United States, India, Australia, and Japan. Its legacy includes sustaining the multi-decadal gravity record that underpins climate assessments by IPCC and operational services at NOAA and ECMWF, as well as technological maturation of inter-satellite laser ranging relevant to future missions conceived at institutions like Massachusetts Institute of Technology and Stanford University. Data stewardship practices developed in coordination with repositories such as National Snow and Ice Data Center and Pangeo ensure long-term accessibility for researchers cited in publications across Nature (journal), Science (journal), and discipline journals in geophysics and hydrology.

Category:Earth observation satellites Category:NASA satellites