A US–German gravity-mapping mission that launched in May has not gathered science data since mid-July because of a problem with a key instrument. The twin satellites of the Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission measure minute differences in the distance between them to chart changes in Earth’s gravity. Doing so can reveal the distribution and flow of water and ice across the planet.
But part of a microwave instrument aboard one of the satellites shut itself down on 19 July following signs of an electrical problem. Mission managers are investigating the cause and plan to switch to a back-up system later this month, NASA’s Jet Propulsion Laboratory in Pasadena, California, announced on 14 September.