Sea-level rise is one of the most immediate consequences of climate change, as highlighted recently through urgent pleas from leaders of island nations at the COP26 summit. Global measures of sea-level rise are imperative to underpinning global policy and for strategies to protect coastlines and low-lying lands. Measuring tiny differences in the height of the sea surface from space is no easy task—but that's exactly what the Copernicus Sentinel-6 Michael Freilich satellite is doing. And, after a year of exhaustive testing, this new mission is now delivering the world's most accurate data on sea-level rise.