Sentinel-6B Satellite Captures First Data Set

16 December 2025

Sea-level rise in the Gulf Stream. (Image credit: ESA, Sentinel-6B)

Copernicus Sentinel-6B, launched last month, has reached its orbit and delivered its first set of data, which shows variations in sea level in the North Atlantic Ocean. This data underlines how the mission will continue to strengthen the long-term reference record of sea levels, a key parameter of climate change.

Following its launch on November 17, 2025, the first data from Sentinel-6B was captured on November 26 by the satellite’s Poseidon-4 altimeter. The image, shown below, is a combination of altimeter data from five sea-level tracking satellites: Sentinel-6B; its twin, Sentinel-6 Michael Freilich, which was launched in 2020; Sentinel-3A and Sentinel-3B, as well as Jason-3.

The image, shown below, is a combination of altimeter data from both the Sentinel-6 sea-level tracking satellites: Sentinel-6B and its twin, Sentinel-6 Michael Freilich, which was launched in 2020. The image shows the Gulf Stream current in the North Atlantic Ocean, off the eastern coasts of the US and Canada.

The Gulf Stream is a hugely important area of the North Atlantic Ocean, not only for the role it plays in global weather patterns and climate, but also because it’s a busy shipping route as well as a key ecosystem for marine species and therefore an important fishing zone.

ESA’s Project Manager for Sentinel-6, Pierrik Vuilleumier, acknowledged the teams’ efforts, “This is the second launch for the Sentinel-6 mission and I am very pleased to see that industry and agency teams have managed again to guarantee the essential continuity of the mean sea-level record, adding five years to the 35 years already accumulated.”

State-o -the-Art Altimetry

The image was created using data from the mission’s Poseidon-4 dual-frequency (C- and Ku-band) radar altimeter, which uses an innovative mode that has improved performance and resolution compared to previous satellite altimeter designs. Radar altimeter instruments measure the time it takes for radar pulses to reach Earth’s surface and bounce back to the satellite. Sentinel-6 also carries a microwave radiometer, which estimates the delay to the radar pulses caused by Earth’s atmosphere. Both these instruments work together to enable very precise measurements of the sea-surface height as well as wave height and wind speed.

Sentinel-6 also provides data for operational ocean forecasting by providing near-real-time data on extreme weather at sea. The mission provides data to support safer navigation at sea, better coastal protection, and smarter water-resource management.

ESA’s Director of Earth Observation Programs, Simonetta Cheli, said, “Developing missions that can track sea-level rise with such precision and long-term reliability is fully aligned with ESA’s core values and strategic goals. The agency’s Earth Observation programs are focused on providing environments that nurture innovative technology for such satellites. We also establish the crucial collaborations that enable these missions to become key sources of actionable data for the science community and for climate policy. I thank our European partners as well as NASA and NOAA, and I look forward to seeing this mission continue the legacy of reference data on ocean conditions.”

ESA’s Mission Scientist for the Sentinel-6 mission, Alejandro Egido, said, “It is very encouraging to see Sentinel-6B performing so well soon after launch. While the instruments will undergo a careful calibration phase over the coming months, the quality of the initial dataset is very promising. Once this phase is completed, the mission will be fully prepared to extend the sea-surface height measurement record through at least 2030.”