Sentinel-2 Data

The full SENTINEL-2 mission comprises twin polar-orbiting satellites in the same orbit, phased at 180� to each other.

The mission will monitor variability in land surface conditions, and its wide swath width and high revisit time (10 days at the equator with one satellite, and 5 days with 2 satellites under cloud-free conditions which results in 2-3 days at mid-latitudes) will support monitoring of changes to vegetation within the growing season.The coverage limits are from between latitudes 56� south and 84� north.

SENTINEL-2 mission objectives are to provide:
- systematic global acquisitions of high-resolution, multispectral images allied to a high revisit frequency
- continuity of multi-spectral imagery provided by the SPOT series of satellites and the USGS LANDSAT Thematic Mapper instrument
- observation data for the next generation of operational products, such as land-cover maps, land-change detection maps and geophysical variables.

With its 13 spectral bands, 290 km swath width and high revisit frequency, SENTINEL-2's MSI instrument supports a wide range of land studies and programmes, and reduces the time required to build a European cloud-free image archive. The spectral bands of SENTINEL-2 will provide data for land cover/change classification, atmospheric correction and cloud/snow separation.

Each of the SENTINEL-2 satellites weighs approximately 1.2 tonnes, and is designed to be compatible with small launchers like VEGA and ROCKOT. The satellite lifespan is 7.25 years, which includes a 3 month in-orbit commissioning phase. Batteries and propellants have been provided to accommodate 12 years of operations, including end of life de-orbiting manoeuvres.

Two identical SENTINEL-2 satellites will operate simultaneously, phased at 180� to each other, in a sun-synchronous orbit at a mean altitude of 786 km. The position of each SENTINEL-2 satellite in its orbit will be measured by a dual-frequency Global Navigation Satellite System (GNSS) receiver. Orbital accuracy will be maintained by a dedicated propulsion system.

The MSI works passively, by collecting sunlight reflected from the Earth. New data is acquired at the instrument as the satellite moves along its orbital path. The incoming light beam is split at a filter and focused onto two separate focal plane assemblies within the instrument; one for Visible and Near-Infra-Red (VNIR) bands and one for Short Wave Infra-Red (SWIR) bands . The spectral separation of each band into individual wavelengths is accomplished by stripe filters mounted on top of the detectors.

Level-1B Top-of-atmosphere radiances in sensor geometry
Level-1C Top-of-atmosphere reflectances in cartographic geometry
Level-2A Bottom of atmosphere reflectances in cartographic geometry (prototype product)

Products are a compilation of elementary granules of fixed size, along with a single orbit. A granule is the minimum indivisible partition of a product (containing all possible spectral bands).
- For Level-1B, a granule covers approximately 25 km AC and 23 km AL
- For Level-1C and Level-2A, the granules, also called tiles, are 100 km2 ortho-images in UTM/WGS84 projection.
The UTM (Universal Transverse Mercator) system divides the Earth's surface into 60 zones. Each UTM zone has a vertical width of 6� of longitude and horizontal width of 8� of latitude.