The Sentinel-4 Mission and its Implementation
Stark, Hendrik R.; Möller, Hermann Ludwig; Bazalgette Courrèges-Lacoste, Grégory; Koopman, Rob; Mezzasoma, Silvia

The Sentinel-4 mission, as part of the Global Monitoring for Environment and Security (GMES), has the primary objective of observing the diurnal cycle of the tropospheric composition in support of the air quality applications of GMES Atmosphere Services. The Sentinel-4 mission is composed of essentially two elements:

  • the Sentinel-4/Ultra-violet/Visible/Near-Infrared (S4/UVN) instrument(s), being embarked on the geostationary Meteosat Third Generation Sounder (MTG-S) satellite(s);
  • the Sentinel-4 Ground Segment, being embedded in the EUMETSAT MTG Ground Segment with the respective Level 1b (L1b) and Level 2 (L2) processors and further infrastructure elements like the S4/UVN Instrument Quality Tool (IQT) and the Mission Performance Centre (MPC). The expected launch date of the first MTG-S platform is 2019, and the expected mission duration is 15 years, accomplished by the serial launch of the two MTG-S satellites with the S4/UVN instruments. The S4/UVN instrument will provide data products for continuous monitoring above Europe and northern Africa with additional complementary value with respect to low earth orbit predecessor missions, like GOME, SCIAMACHY, OMI, GOME-2 and future missions like Sentinel 5. The instrument design enables a short revisit time from east to west in one hour with sufficient east-west spatial dimension. The key features of the S4/UVN instrument are the spectral range from 305 nm to 500 nm with a spectral resolution of 0.5 nm, and from 750 nm to 775 nm with a spectral resolution of 0.12 nm, in combination with low polarization sensitivity and a high radiometric accuracy. The data acquired by the instrument are downloaded via the normal MTG-S payload data downstream to the EUMETSAT Ground Segment where further processing will be performed at various levels. The Level 1b processor will generate data products like Earth Radiance, Solar Irradiance, Calibrations, Data Processing Parameters File and Star products. In a second step the Level 1b products are further processed by the Level 2 processor facility to generate Core products and Innovative products. The innovative products are synergetic making use of the data from the MTG Flexible Combined Imager (FCI) or the MTG InfraRed Sounder (IRS). It is envisaged that the quality of the products and the performances of the Sentinel-4 system, mission and instrument are constantly monitored both on-line and off-line via the IQT and MPC. The paper will address the operational concept of the Sentinel-4 mission and principles of the mission planning such as the employment of the Instrument Measurement Sequences containing the sequence of instrument / measurement configurations to be executed during each orbit.