Moment of the undocking of the Sentinel-6B satellite to begin orbiting the Earth © SpaceX/NASA. © European Space Agency (ESA).

At 6:21 of the 17th of November (CET time), the second Sentinel-6 satellite, the reference oceanographic mission of the European Commission’s ‘Copernicus’ Earth Observation programme, took off. The launch took place aboard a SpaceX Falcon 9 rocket from Vandenberg Air Force Base, California.

The Sentinel-6B satellite will provide high-precision data essential for climate monitoring and short- and long-term ocean forecasts. The satellite payload incorporates the Poseidon-4 radar altimeter, a sensor that measures, among other things, the average sea level rise. It is the same as its predecessor, Sentinel-6A, launched in November 2020.

isardSAT has developed the algorithms and operational processor for the mission’s satellites, which will allow the satellite’s data to reach scientists so that they can extract sea level estimates and other oceanographic and climatic parameters. isardSAT is already responsible for the internal and external calibration of the Sentinel-6A satellite, as well as other validation activities. The company has designed and demonstrated the effectiveness of innovative calibration methods, such as passive reflectors.

Launch of the Sentinel-6B satellite at 6:21 a. m. CET on 17th November 2025 aboard a Falcon 9 rocket from the air base from Vandenberg, in California (USA). © European Space Agency (ESA).

“Thanks to the development of new data processing algorithms, we increasingly have more precise information on sea level, which helps us better understand how climate change affects us,” explains Mònica Roca i Aparici, director of isardSAT. The engineer will attend the launch of the satellite from Vandenberg Air Force Base (California, USA), where the annual scientific meeting of experts in altimetry (OSTST) is being held. “The launch of Sentinel-6B is a step forward in ensuring the continuity of these essential data for the coming years,” she says.

You can see the satellite in detail in this reconstruction created by EUMETSAT.

Corrner reflector for satellite calibration, located at the Montsec Observatory, in Sant Esteve de la Sarga. © isardSAT.

More than three decades of sea level monitoring

Satellite sea level monitoring began in 1991 with the ERS-1 mission (1991-2000), and has continued with the TOPEX/Poseidon (1992-2006), ERS-2 (1995-2011), GFO (1998-2008), Jason 1 (2001-2013), Envisat (2002-2012), Jason -2 (2008-2019), CryoSat-2 (2010-present), SARAL (2013-2024), Jason-3 (2016-present), Sentinel-3A (2016-present), Sentinel-3B (2018-present), Sentinel-6A (2020-present), and SWOT (2022-present) missions.

Evolution of mean sea level from 1991 to the present day, through satellite altimetry missions © EUMETSAT.

During this period, observations have shown how global mean sea level has risen due to the melting of polar ice caps and glaciers, and the thermal expansion of the oceans. Since 1999, global sea level has risen by 9.38 cm (3.7 mm/year on average) and in the last ten years this rate has accelerated by 46%, from 2.9 mm/year (1999–2009) to 4.2 mm/year (2014–2024).

The Sentinel-6 mission is a collaboration between the European Space Agency (ESA), the European Commission through the Copernicus programme, the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT), NASA’s Jet Propulsion Laboratory, and the US National Oceanic and Atmospheric Administration (NOAA). Its data is in the public domain, and the mission is expected to continue until at least 2030.