OHB System AG will develop Sentinel-3 Next Generation Topography under a €554 million contract announced on November 4, 2026. The European Space Agency commissioned the company as prime contractor for the Copernicus mission, with an option for a second satellite.
The mission will measure the height of ocean surfaces, coastal waters, inland waters and ice. OHB will lead a European industrial consortium, drawing on experience accumulated through earlier satellite altimetry missions. Altimetry is the measurement of surface height from above.
Separating Optical and Height Measurements
The next generation changes how Sentinel-3’s observations are organized. The existing spacecraft design combines radar measurements of surface height with optical instruments that measure color and temperature. The new architecture separates those tasks into dedicated missions.
Under the announced arrangement, optical instruments will collect visible and infrared observations and measure surface temperature on a separate mission. Sentinel-3 Next Generation Topography will carry the radar altimetry instruments. OHB describes a planned pair of identical spacecraft in sun-synchronous orbit, with the second satellite covered by the contract option.
This division preserves the different types of information associated with Sentinel-3 while assigning height measurements to a specialized spacecraft mission.
How Sentinel-3 Measures Surface Height
The established Sentinel-3 topography package helps explain the measurements that the new mission will continue. Its radar altimeter operates in two frequency bands, Ku and C, and uses synthetic aperture radar processing to distinguish observations along the satellite’s direction of travel. ESA gives an along-track resolution of approximately 300 meters after processing.
A microwave radiometer supports the height measurements by observing atmospheric water vapor. Water vapor affects the radar signal’s travel through the atmosphere, so atmospheric corrections form part of producing accurate surface measurements. The instruments work together to turn observations from orbit into information about the surface below.
Sentinel-3 altimetry covers sea-surface height, wave height and ocean surface wind speed, as well as topography over sea ice, ice sheets, rivers and lakes. These are different physical quantities derived from the observing system. Height data support the study of ocean circulation and changes in water and ice.
The broader Sentinel-3 mission also supplies information for ocean forecasting and environmental monitoring. Its color and temperature instruments add observations of ocean ecosystems, vegetation and surface conditions, explaining why the successor architecture retains both optical and topographic measurement roles.
For the new topography mission, OHB identifies more precise height measurements, wider coverage and shorter intervals between observations as planned improvements. ESA describes the development as a continuation of Sentinel-3 and Sentinel-6 altimetry, extending the measurements used to observe oceans, inland waters and ice.
