November 21, 2017

Ground segment


After the launch of Sentinel-3A on 16 February 2016, teams spent the next five months checking it out to make sure everything was working properly in orbit. This phase was conducted by ESA’s European Space Operations Centre (ESOC) in Darmstadt, Germany. Once in-orbit commissioning was complete, ESA handed over operations to Eumetsat, also based in Darmstadt. Housekeeping telemetry and commands are uplinked from ESA’s ground station in Kiruna, Sweden.

Eumetsat operates the satellite, while ESA provides support monitoring the health of the satellite, including the bus and instruments, and supplying specific services such as the S-band ground station in Kiruna and the back-up control centre.

Once Sentinel-3 data have been acquired, they are downlinked to ground and received at ESA’s X-band station in Svalbard, Norway. They are then processed and archived by a network of centres. ESA is in charge of Sentinel-3 ground segment operations for all land surface products, as well as for mission data quality control. Eumetsat supplies ocean surface products.

All products are archived and distributed to users on line.


While the ground segments for each Sentinel mission feature their own specific components, all of them are linked up to form the Copernicus Space Component (CSC) Ground Segment. Access to CSC data is coordinated by ESA through the CSC Data Access System.

Here, data from the various ground segments and missions are collected as transparently as possible to users. Eumetsat distributes basic marine products through the EUMETCast system.

The CSC Ground Segment is complemented by the Sentinel Collaborative Ground Segment, which supports data use for ESA’s member states. This means additional elements are required for specialist technology solutions, for example for data acquisition, extra data production and dissemination of innovative tools and applications, as well as support for calibration and validation.

The CSC Ground Segment and the Coordinated Data Access System are coordinated by ESA (and by Eumetsat for the relevant Sentinel missions), while the Sentinel Collaborative Ground Segment is funded and managed by third parties like national space agencies.

To cater for needs in France, CNES has set up its PEPS Sentinel Product Exploitation Platform, which allows users to search, select and download data from the Sentinel-1, Sentinel-2 and Sentinel-3 satellites. Within the next few months, PEPS will also be offering users the ability to process data on line to avoid having to store large volumes locally.


Quicklook of OLCI data from the Sentinel-3A satellite of 25/01/2017 - © ESA



All the instruments on the Sentinel-3 satellites acquire data systematically.

There are four separate processing chains for the three main instruments, SLSTR (Sea and Land Surface Temperature Radiometer), OLCI (Ocean and Land Colour Instrument) and SRAL (SAR Radar Altimeter), and for combined SLSTR/OLCI data.

These processing chains generate ocean colour and land surface reflectances from OLCI data, land surface and sea temperatures from SLSTR data, ocean and land surface products and vegetation products (from combined SLSTR/OLCI data) as shown in the schematic diagram above.

Products are typically available within 3 hours of data acquisition.

A Sentinel-3 toolbox lets users view and analyse products.