The twin satellites that have been critical in measuring the world’s melting ice sheets for 15 years will soon shut down — months before their replacement is launched into orbit, NASA announced, creating a gap in the ice data record that has been instrumental in studying the impacts of global warming.
The Gravity Recovery and Climate Experiment satellites (GRACE-1 and GRACE-2), a U.S.-German collaboration, have run for a decade past their expected life, but are nearly out of fuel, Science magazine reported. The satellites measure tiny shifts in the Earth’s gravity that represent the flow of mass on the planet, including the melting of ice in the poles and the drawdown of groundwater aquifers.
The GRACE-2 will make its last data-gathering runs around the planet from mid-October to early November, after which both GRACE-1 and GRACE-2 will be decommissioned. A replacement for the twin satellites is ready — the $550 million GRACE Follow-on (GRACE-FO) — but NASA has had a difficult time securing a ride for the new satellite into space. It is now scheduled for launch into orbit in early 2018.
But Eric Rignot, a glaciologist at NASA’s Jet Propulsion Lab in Pasadena, California, told Science it will be difficult to stitch the ice data together into a seamless record. Other satellite data may provide some information, but not at the level of minute detail or covering the wide variety of earth processes that the GRACE satellites provide. “It would be an impossible task to fill that gap,” Rignot said.