WASHINGTON - The National Aeronautics and Space Administration's (NASA) Jet Propulsion Laboratory (JPL) awarded Airbus Defense and Space in Friedrichshafen, Germany to design and build the GRACE-C twin spacecraft.
This new mission of NASA and the German Space Agency at the German Aerospace Center (DLR) continues the partnership between the USA and Germany to ensure uninterrupted measurement of the Earth's gravity field, which started in 2002 with GRACE and continues with GRACE Follow-On, launched in 2018.
During its five-year nominal mission lifetime, the Gravity Recovery And Climate Experiment-Continuity (GRACE-C) mission will continue the series of measurements observing how Earth’s groundwater, oceans, ice sheets, and land shift, month-to-month, by measuring changes in the planet’s gravity field.
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GRACE-C consists of two identical satellites flying around 200 km apart at an orbit altitude of 500 km with an inclination of 89 degrees. Each satellite will measure approximately 3 x 2 x 1 metres and weigh around 600 kg. The launch is planned no earlier than late 2028 from the USA.
Like its predecessors, the GRACE-C mission is designed to precisely measure small distance changes between the satellites due to gravity variations, with precision down to the micron. As the pair of satellites circle the Earth, areas of slightly stronger gravity (greater mass concentration) will affect the spacecraft’s positions and hence the distance between them. The extremely precise microwave ranging system will detect these changes and enable the mapping of Earth’s gravity field with unmatched accuracy.
Over the months and years, the comparison of these gravity maps, or the evolution of mass concentrations, will enable scientists to assess the global water balance, including groundwater tables and ice sheets, and the influence of climate change. It will also provide insights into deep and surface currents in oceans and ocean height contributors.
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GRACE-C is a rebuild of the two GRACE Follow-On satellites with upgraded avionics based on state-of-the-art technology and the joint US-German Laser Ranging Interferometer (LRI), already flown on GRACE Follow-On as an experimental payload, now being the main ranging instrument.
The mission is based on a NASA/DLR interagency partnership: German contributions are funded by the Federal German Ministry of Economic Affairs and Climate Action as well as the Federal Ministry of Education and Research. The optical bench of the LRI instrument is built by SpaceTech GmbH in close cooperation with the Max Planck Institute Gravitational Science (Albert Einstein Institute).
