The world’s oceans are the motor of Ecosystem Earth, and yet we know relatively little about them. The European earth observation satellite Sentinel-3A is supposed to change that. Yesterday, on 16 February 2016, Sentinel-3A was successfully launched at 18.57 Central European Time from the Russian space centre in Plesetsk. Some of the data collected by this satellite will be processed and archived at EOC. On behalf of ESA, DFD operates a Sentinel-3 Processing and Archiving Centre (PAC).
Sentinel-3 is designed to aid understanding of global phenomena like El Niño, improve climate models, monitor the condition of the oceans and vegetation on land, and make it possible to better manage our resources by providing up-to-date status messages. Sentinel-3A is the third satellite in a series of six satellite families planned for the Copernicus programme, which is run by the European Union (EU) and ESA.
From its orbit at an altitude of 815 kilometres the satellite can supply data about the ocean and land surfaces continuously for large areas, thanks to its wide swath width. Carrying four earth observation sensors, Sentinel-3 is the most elaborate satellite in the Copernicus programme. The SLSTR instrument (Sea and Land Surface Temperature Radiometer) measures, accurate to a third of a degree centigrade, the temperature of the ocean and the land surface and can also detect high temperature events on land such as forest fires. OLCI (Ocean and Land Colour Instrument) scans the earth in 21 wavelengths in a range from visible light to near-infrared. It can see “colours” and distinguish “shades” that are invisible to the human eye, and thereby provide information about the condition of water bodies, the development of plants, and the aerosol content of the atmosphere. SRAL (SENTINEL-3 Ku/C Radar Altimeter) uses two radar frequencies to ascertain the heights of oceans and waves, wind speeds, and the heights of sea ice and ice fields. MWR (MicroWave Radiometer) records atmospheric values like water vapour content, which makes it possible to remove from the acquired measurements the effects of the atmosphere.
Sentinel-3A carries on the work of earlier satellites – especially the ESA satellite ENVISAT, which was taken out of operation in 2012. However, the instruments on Sentinel-3A have better spectral resolution, higher temporal resolution, and they measure atmospheric parameters more precisely. Sentinel-3 is designed to monitor Earth for seven years, although its service life might extend up to 12 years under favourable conditions. The structurally similar Sentinel-3B satellite is planned for launch in 2017. It will orbit Earth on an identical but time-delayed polar orbit. This doubles the recording capacity and makes it possible for this pair of satellites to provide global coverage daily or every two days, depending on the instrument.
Three Processing and Archiving Centres (PACs) process the data from the Sentinel-3 mission. DFD in Oberpfaffenhofen is the PAC for the data collected by the OLCI instrument. The measurements acquired at Norway’s Svalbard (Spitzbergen) receiving station undergo two-stage processing in Oberpfaffenhofen to yield value-added products. These will be stored in a Long-Term Archive (LTA) and made available to users worldwide for several years.
The EOC staff was already at work just a few days after the launch of the satellite. At the latest, one half year after the start of the mission the data will be available to the general public on a European platform. Each year, up to 300 terabytes of OLCI data will accumulate. DFD is not only a Processing and Archiving Centre for Sentinel-3, but also for the Sentinel-1 mission. Just a few days ago, after only 14 months, the management of the first petabyte (one million gigabytes) of data from the Sentinel-1 mission could be celebrated. Enormous amounts of data have to be processed, stored and maintained long-term. The next mission, Sentinel-5P, is to follow shortly, and DFD will not only have responsibility for a PAC, but also for data acquisition.