Twin Spacecraft to Weigh in on Earth’s Changing Water

Twin Spacecraft to Weigh in on Earth’s Changing Water

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A pair of new spacecraft that will observe our planet’s ever-changing water cycle, ice sheets and crust is in final preparations for a California launch no earlier than Saturday, May 19. The Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission, a partnership between NASA and the German Research Centre for Geosciences (GFZ), will take over where the first GRACE mission left off when it completed its 15-year mission in 2017.

GRACE-FO will continue monitoring monthly changes in the distribution of mass within and among Earth’s atmosphere, oceans, land and ice sheets, as well as within the solid Earth itself. These data will provide unique insights into Earth’s changing climate, Earth system processes and even the impacts of some human activities, and will have far-reaching benefits to society, such as improving water resource management.

“Water is critical to every aspect of life on Earth – for health, for agriculture, for maintaining our way of living,” said Michael Watkins, GRACE-FO science lead and director of NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California. “You can’t manage it well until you can measure it. GRACE-FO provides a unique way to measure water in many of its phases, allowing us to manage water resources more effectively.”

Illustration of the NASA’s Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) spacecraft, which will track changes in the distribution of Earth’s mass, providing insights into climate, Earth system processes and the impacts of some human activities. GRACE-FO is a partnership between NASA and the German Research Centre for Geosciences.

Like GRACE, GRACE-FO will use an innovative technique to observe something that can’t be seen directly from space. It uses the weight of water to measure its movement – even water hidden far below Earth’s surface. GRACE-FO will do this by very precisely measuring the changes in the shape of Earth’s gravity field caused by the movement of massive amounts of water, ice, and solid Earth.

“When water is underground, it’s impossible to directly observe from space. There’s no picture you can take or radar you can bounce off the surface to measure changes in that deep water,” said Watkins. “But it has mass, and GRACE-FO is almost the only way we have of observing it on large scales. Similarly, tracking changes in the total mass of the polar ice sheets is also very difficult, but GRACE-FO essentially puts a ‘scale’ under them to track their changes over time.”

At the Harris facility at Vandenberg Air Force Base in California, one of the twin GRACE-FO satellites are integrated with the multi-satellite dispenser structure that will be used to deploy the satellites during launch.