Sentinel-6B in orbit to continue decades-long sea-level observations
A new eye on the world's changing oceans has just awakened above Earth. With the Copernicus Sentinel-6B satellite now gliding into its orbital path, society has gained a powerful new observer dedicated to one of the most urgent indicators of climate change: sea surface height. Its arrival marks the next chapter in a continuous global effort to understand how the oceans are responding to a warming planet.
Sentinel-6B follows in the path of Sentinel-6 Michael Freilich, carrying state-of-the-art radar altimetry technology to extend the sea surface height record that began in the early 1990s. These long-term measurements give scientists essential insight into sea-level rise, a trend that influences climate strategy, coastal protection and the safety of millions of people who live near the shoreline.
The satellite was launched on 17 November aboard a SpaceX Falcon 9 rocket from Vandenberg Space Force Base in California. It was delivered into orbit just under an hour after lift-off, and not much later ESA’s European Space Operations Centre in Germany received the all-important signal via the Inuvik ground station in Canada, indicating that Sentinel-6B is alive and well.
Primary reference mission
Sentinel-6B is set to carry forward the legacy of Sentinel-6 Michael Freilich, launched in November 2020. The Sentinel-6 mission serves as the world’s primary reference mission for satellite sea surface height measurements. The continuous record of observations began in the early 1990s with the French-US Topex-Poseidon satellite and continued with the Jason series of satellite missions.
With sea-level rise high on the global agenda, numerous organizations have worked to make Copernicus Sentinel-6 the gold-standard reference mission for extending the record of sea surface height measurements – delivering data with greater precision than ever before.
Although part of the European Union’s family of Copernicus missions, Sentinel-6 is the product of exceptional international cooperation, involving the European Commission, ESA, NASA, Eumetsat and NOAA, with additional support from the French space agency CNES.
Simonetta Cheli, ESA’s director of Earth observation programmes, said: “Collaboration between partners is key to a mission such as Sentinel-6, and my thanks go to everyone involved in developing, launching and operating this exceptional satellite, which follows in the footsteps of the first Sentinel-6, Michael Freilich.”
“This achievement demonstrates what can be accomplished when international agencies and industries work together towards a shared goal. Sentinel-6B will ensure that we continue to collect the high-precision data needed to understand our changing climate, safeguard our oceans and support decisions that protect coastal communities around the world.”
Near-real-time ocean forecasting
As well as mapping the height of the sea surface to understand long-term change, Copernicus Sentinel-6 also provides data for practical ‘operational’ applications. For example, the mission measures significant wave height and wind speed, data that is used for near-real-time ocean forecasting. In fact, satellite altimetry provides the most comprehensive ocean sea state measurements available today.
The Sentinel-6 satellites carry an altimeter that works by measuring the time it takes for radar pulses to travel to Earth’s surface and back again to the satellite. Combined with precise satellite location data, altimetry measurements yield the height of the sea surface.
The satellites’ instrument package also includes an advanced microwave radiometer provided by NASA. Water vapour in the atmosphere affects the speed of the altimeter’s radar pulses – and therefore estimates of sea surface height. The advanced microwave radiometer accounts for this water vapour to ensure that measurements are accurate.
Sentinel-6B is now under the care of ESA’s mission control in Germany, where the team is taking the satellite through its ‘Launch and Early Orbit Phase’. Once this has been completed, control of the satellite will be handed over to Eumetsat.
