Sentinel-6B

Sentinel-6B (S6B) is a radar altimeter satellite developed in partnership between several European and American organizations. It is part of the Jason satellite series. S6B includes a synthetic-aperture radar altimetry instrument designed to improve ocean topography measurements, as well as topography of rivers and lakes.^[1] The spacecraft is expected to operate for 5.5 years after entering service.^{[2][3][4][5][6][7]} The main objective of the Sentinel-6 mission is to measure sea surface topography with high accuracy and reliability to support ocean forecasting systems, environmental monitoring, and climate monitoring.^[8][9]

Sentinel-6B

Illustration of the Sentinel-6B spacecraft in orbit above Earth with its deployable solar panels extended
Names	Sentinel-6B Jason-CS B
Mission type	Oceanography mission
Operator	EUMETSAT / NASA
Website	www.eumetsat.int/sentinel-6
Mission duration	5.5 years (planned)
Spacecraft properties
Bus	Sentinel-6
Manufacturer	Airbus Defence and Space
Launch mass	1,192 kg (2,628 lb)
Dimensions	5.13 x 4.17 x 2.34 metres
Power	891 watts
Start of mission
Launch date	16 November 2025
Rocket	Falcon 9 Block 5
Launch site	Vandenberg, SLC-4E
Contractor	SpaceX
Orbital parameters
Reference system	Geocentric orbit
Regime	Low Earth orbit
Altitude	1,336 km (830 mi)
Inclination	66.0°
Repeat interval	10 days
Instruments
Radar altimeter Advanced Microwave Radiometer (AMR-C) GNSS Precise Orbit Determination (POD) Receiver DORIS Receiver Laser Reflector Array (LRA) Radio-occultation instrument
Sentinel ← Sentinel-1D Sentinel-3C → Jason satellite series/Sentinel 6 ← Sentinel-6A

Background

Since the launch of TOPEX/Poseidon on 10 August 1992, high-precision satellite altimeters have been essential for monitoring how the ocean stores and redistributes heat, water, and carbon in the climate system. The Sentinel-6 program is a continuation of this series of mesurements. It includes two identical satellites launched five years apart, Sentinel-6 Michael Freilich, which launched on 21 November 2020,^[10] and Sentinel-6B, expected to launch on 16 November 2025.^[11] They are designed to extend the legacy of satellite altimetry at least through 2030, which will provide a nearly forty-year record of sea level rise as well as changes in ocean currents.^{[11][12][13][14]}

Launch

During 2025, Sentinel-6B underwent a series of checks at IABG in Ottobrunn, Germany and it was later transported by truck to Bremen, Germany. In July 2025, the satellite was transported from Bremen to Galveston, Texas aboard the cargo ship Industrial Dolphin.^[15] In late August 2025, the satellite arrived by truck at Vandenberg Space Force Base in California.^[16] On 24 September 2025, the satellite was transferred to the Astrotech Space Operations processing facility. By 1 October 2025, the satellite was unpacked from its storage container and prepared for its launch campaign.^[17][18] Meanwhile at ESOC, the simulation campaign for the satellite's Launch and Early Orbit Phase (LEOP) started on 2 September 2025.^[19]

Instruments

• POSEIDON4, a radar altimeter, developed by ESA, based on the Sentinel-3 SRAL instrument, but with a design adopted to allow an interleaved mode combining a synthetic-aperture radar High-Resolution (HR) mode and a low resolution (LR) mode based on pulse-limited altimetry
• Advanced Microwave Radiometer (AMR-C) provided by NASA
• Global Navigation Satellite System Precise Orbit Determination (GNSS POD) receiver, developed by ESA and derived from the GNSS Receiver on Sentinel-3
• Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS Receiver), identical to the one used on Jason-3 and Sentinel-3
• Laser Reflector Array (LRA), used for satellite laser ranging, identical to the one used on Jason-3, provided by NASA
• GNSS Radio Occultation (GNSS-RO) based on a Tri-G receiver, provided by NASA ^[20]

Partnership

Sentinel-6 was developed by European Space Agency (ESA) in the context of the European Copernicus Programme led by the European Commission, the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT), NASA, and the National Oceanic and Atmospheric Administration (NOAA), with funding support from the European Commission and technical support from France's National Centre for Space Studies (CNES).^[21]

The mission definition is driven by the need for continuity in provision of TOPEX/Poseidon mission and Jason satellite series (Jason-1, OSTM/Jason-2, and Jason-3) with improvements in instrument performance and coverage.^[22] ESA, NASA, and EUMETSAT provide mission management and system engineering support. EUMETSAT and NASA are responsible for long-term archives of altimetry data products. All partners were involved with the selection of science investigators.^[22]

ESA has responsibility for procurement of Sentinel-6B on behalf of EUMETSAT and the European Commission, and for conducting the Launch and Early Orbit Phase (LEOP) of the satellite. ESA also supports flight operations performed by EUMETSAT.

EUMETSAT has responsibility for ground segment development and coordination at system level, including for operations preparation, for conducting operations of the satellite after LEOP performed by ESA, and for conducting operations of the European part of the ground segment, including processing of altimeter data and delivery of product services to European users.

NASA has responsibility for the development and delivery of the U.S. payload instruments, the microwave radiometer and the GNSS radio occultation receiver. NASA also provides launch services for the satellite and ground segment development support. NASA will contribute to operations and data processing on the U.S. side, including processing of GNSS radio occultation data, and together with NOAA, shares responsibility for the distribution of products to research and operational users in the U.S.

NOAA provides a U.S. ground station for tracking and command of the satellite and data downlinks. Togethre with NASA, NOAA shares responsibility for the distribution of products to research and operational users in the U.S.

CNES has responsibility for processing higher-level products (L2P, L3) and for providing precise orbit determination and support for Doris and altimeter operations.^[20]

See also

• List of European Space Agency programmes and missions