Copernicus Sentinel-6B entered operational service on 30 October 2026, ensuring that a satellite record of global sea level begun more than 30 years ago will continue into the 2030s. Operated by EUMETSAT on behalf of the European Commission, it will soon become the world’s reference satellite for high-precision ocean altimetry, the benchmark against which other sea-level missions are calibrated.
Weather forecasters use Copernicus Sentinel-6B data on timescales from days to months. Within hours of being collected, they go into the models of weather services, helping to forecast rough seas during Atlantic winter storms and Mediterranean cyclones, and how strong hurricanes will become. The sea-level record also informs seasonal forecasts, including predictions of El Niño and La Niña. A radio occultation instrument on board also adds data on atmospheric temperature and water vapour.
Copernicus uses Sentinel-6B’s observations across its services, including its climate services, which monitor long-term changes in the ocean, and its ocean forecasts. These forecasts help show major currents, and ships will change course depending on where they lie and the direction of the waves. A high-resolution mode on both Sentinel-6 satellites gives detailed measurements near coastlines and over inland waters, supporting safer maritime navigation, coastal protection and water-resource management.
Global average sea level has risen by more than 11.5 cm since December 1992, and the pace is accelerating, rising 2.8 cm during the first decade and as much as 4.0 cm over the most recent decade. The rise is driven by a combination of melting glaciers and ice sheets, and ocean warming which causes water to expand. To track sea level rise, Sentinel-6B and its twin, Sentinel-6 Michael Freilich launched in November 2020, will provide data on sea level across up to 95% of the ice-free ocean, along with ocean currents, wave height and wind speed, and water levels in rivers and lakes.
“No other technology can follow changes in sea level across the whole globe as consistently as satellite altimetry, and its data are essential for both climate research and policy and weather and ocean forecasting,” says Phil Evans, Director-General of EUMETSAT. “Around 900 million people live in low-lying coastal areas worldwide, and weather and ocean services across our Member States rely on Sentinel-6 data to protect people, infrastructure and ecosystems. Combined with altimetry from Copernicus Sentinel-3, Sentinel-6B gives a fuller picture of the oceans, and with wind and atmospheric data from our Metop satellites it supports weather forecasts every day. This European–US mission shows once again what we can achieve together.”
A transatlantic mission
Copernicus Sentinel-6 continues a sea-level record begun in 1992 by TOPEX/Poseidon and the Jason series, and a long-standing collaboration between European and United States partners. EUMETSAT operates the satellites around the clock and delivers their data within about three hours.
Sentinel-6 Michael Freilich and Sentinel-6B are twin satellites. Since December 2025, the two satellites have flown in tandem at 1,336km, 30 seconds apart, so that scientists can calibrate Sentinel-6B against its twin. Sentinel-6B is expected to become the internationally agreed reference in the coming months; Sentinel-6 Michael Freilich will then move to a new orbit, ending the tandem flight and giving more complete coverage of the oceans.