November 21, 2017



Sentinel-3 satellite - © ESA

a Constellation of Satellites


Sentinel-3A in the clean room © ESA - A. Le Floc'h

The Sentinel-3 mission is built around a constellation of two satellites orbiting Earth at an altitude of 814.5 km. This configuration ensures optimal global coverage and revisit rates.

Sentinel-3A and Sentinel-3B will provide global coverage every day for the SLSTR instrument and every two days for the OLCI instrument. Most data will be processed systematically and available to users within 3 to 48 hours after acquisition.

The satellites were developed with the expertise of a number of firms overseen by prime contractor Thales Alenia Space in France. The satellites and instruments also draw on the design heritage of ESA missions such as ERS, Envisat and CryoSat, as well as the French VEGETATION instrument on the SPOT satellites and the Jason series.

Both satellites have a design life of at least 7 years and enough fuel for 12 years of continuous operation.

Alongside their sister satellites in the Sentinel fleet, Sentinel-3A and Sentinel-3B are set to make a unique contribution to acquiring more and improved Earth remote-sensing data in the decades ahead.

Facts and figures


  • Sentinel-3A: 16 February 2016
  • Sentinel-3B: planned for 2018

Launch vehicle

  • Sentinel-3A : Rockot from Plesetsk, Russia
  • Sentinel-3B : Vega from Kourou, French Guiana


    • Polar, Sun-synchronous at an altitude of 814.5 km with a local descending node crossing time of 10:00 at the equator.

    Revisit rate (ocean)

      • SLSTR - 1 day, OLCI - 2 days, for SRAL the inter-track separation is 52 km after 27 days – in all three cases using both satellites at the equator.

      Design life

        • 7 years (extendible to 12 years)

        Satellites dimensions

          • 2.2 m long, 2.2 m wide, 3.7 m high, mass 1,150 kg (including 130 kg of fuel)


            • Ocean and Land Colour Instrument (OLCI) covering 21 spectral bands (400–1020 nm) with a 1,270-km swath
            • Sea and Land Surface Temperature Radiometer (SLSTR) covering 9 spectral bands (550–12 000 nm), dual-view scanning with swath width of 1,420 km at nadir and 750 km looking aft
            • Synthetic Aperture Radar Altimeter (SRAL), operating in Ku band (300 m after SAR processing) and C band
            • Microwave Radiometer (MWR), dual frequency (23.8 GHz and 36.5 GHz)
            • Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS), transmitting an omnidirectional signal of known frequency (2 GHz and 400 MHz)
            • GNSS, with 8 channels for tracking GPS signals

            Receiving stations

              • Science data: downloaded to ground stations in the Sentinel programme
              • Telemetry data: sent from Kiruna, Sweden

                Main applications

                • Mapping of sea level and ocean surface temperature variations, water quality management, mapping of sea ice extent and thickness, numerical ocean modelling
                • Mapping of land cover, vegetation health monitoring
                • Glacier monitoring
                • Water resource monitoring
                • Fire detection
                • Numerical weather forecasting

                Key contractors

                • Thales Alenia Space France for the satellite and OLCI and SRAL instruments
                • Selex Es Italy for the SLSTR instrument
                • EADS-CASA for the MWR instrument
                • TSA for the DORIS instrument
                • RUAG for the GNSS instrument

                Data access