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 SENTINEL-2 satellite system is being developed by an industrial consortium led by Astrium GmbH (Germany). Astrium SAS (France) is responsible for the MultiSpectral Instrument (MSI).
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.
Figure 1: Schematic View of the Deployed SENTINEL-2 Spacecraft (image credit: EADS Astrium)
The optical design of the MSI telescope allows for a 290 km Field Of View (FOV).
A shutter mechanism prevents the instrument from direct illumination by the sun in orbit and to avoid contamination during launch. The same mechanism functions as a calibration device by collecting the sunlight after reflection by a diffuser.