US and German engineers hail launch of mission to track Earth's water from space

The so-called Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) – a collaboration between NASA and the German Research Centre for Geosciences (GFZ) - will use two satellites to precisely track variations in the Earth’s gravitational pull resulting from the movement of water around the planet.

These gravitational changes will cause the distance between the two satellites to vary slightly. Although the two satellites orbit 137 miles (220km) apart, advanced instruments continuously measure their separation to within the width of a human red blood cell.

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

Initial telemetry gathered following the launch showed that the satellites are performing as expected, travelling at 7.5 kilometres per second at an altitude of around 490km and circling Earth once every 90 minutes.