Twin spacecraft to track Earth's water cycle successfully launched

A twin spacecraft to track the global water cycle has been successfully launched aboard the a SpaceX rocket, along with five communications satellites today, NASA said.

The Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) is a joint mission by NASA and the German Research Centre for Geosciences (GFZ).

It lifted off on a SpaceX Falcon 9 rocket from the Vandenberg Air Force Base in California, US, sharing their ride into space with five Iridium NEXT communications satellites.

Ground stations have acquired signals from both GRACE-FO spacecraft. Initial telemetry shows the satellites are performing as expected. The GRACE-FO satellites are at an altitude of about 490 kilometers, traveling about 7.5 kilometers per second. They are in a near-polar orbit, circling Earth once every 90 minutes.

"GRACE-FO will provide unique insights into how our complex planet operates," said Thomas Zurbuchen, associate administrator of NASA's Science Mission Directorate at NASA Headquarters in Washington.

"Just as important, because the mission monitors many key aspects of the Earth's water cycle, GRACE-FO data will be used throughout the world to improve people's lives - from better predictions of drought impacts to higher-quality information on use and management of water from underground aquifers," said Zurbuchen.

Over its five-year mission, GRACE-FO will monitor the movement of mass around our planet by measuring where and how the moving mass changes Earth's gravitational pull.

The gravity changes cause the distance between the two satellites to vary slightly. Although the two satellites orbit 220 kilometres apart, advanced instruments continuously measure their separation to within the width of a human red blood cell.

The original GRACE mission, which operated from 2002 through 2017, created monthly maps of regional gravity variations, providing new insights into how the Earth system functions and responds to change.

Among its innovations, GRACE was the first mission to measure the amount of ice being lost from the Greenland and Antarctic ice sheets.

The mission improved our understanding of the processes responsible for sea level rise and ocean circulation, provided insights into where global groundwater resources are shrinking or growing, showed where dry soils are contributing to drought, and monitored changes in the solid Earth, such as from earthquakes.

Frank Webb, GRACE-FO project scientist at NASA's Jet Propulsion Laboratory in Pasadena, California, noted that to understand changes taking place in the climate system, scientists need data records several decades long.

"Extending the data record from GRACE will allow us to better distinguish short-term variability from longer-term trends," he said.

The GRACE-FO satellites will spend their first few days in space moving to the separation distance needed to perform their mission. When they reach this distance, the mission will begin an 85-day, in-orbit checkout phase.

Mission managers will evaluate the instruments and satellite systems and perform calibration and alignment procedures. Then the satellites will begin gathering and processing science data.

The first science data are expected to be released in about seven months.