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Proceedings Paper • Open Access

The multispectral instrument of the Sentinel2 program
Author(s): V. Cazaubiel; Vincent Chorvalli; Christophe Miesch

Paper Abstract

The Sentinel-2 program will provide a permanent record of comprehensive data to help inform the agricul-tural sector (utilisation, coverage), forestry industry (population, damage, forest fires), disaster control (management, early warning) and humanitarian relief programmes. Sentinel-2 will also be able to observe natural disasters such as floods, volcanic eruptions, subsidence and landslides.

In the Sentinel-2 mission programme, Astrium in Friedrichshafen is responsible for the satellite’s system design and platform, as well as for satellite integration and testing. Astrium Toulouse will supply the Multi-Spectral imaging Instrument (MSI), and Astrium Spain will be in charge of the satellite’s structure and will produce its thermal equipment and cable harness. The industrial core team also comprises Jena Optronik (Germany), Boostec (France), Sener and GMV (Spain). Sentinel-2 is intended to image the Earth’s landmasses from its orbit for at least 7.25 years. In addition, its onboardresources will be designed so that the mission can be prolonged by an extra five years. From 2012 onwards, the 1.1-metric-ton satellite will circle the Earth in a sun-synchronous, polar orbit at an altitude of 786kilometres, fully covering the planet’s landmasses in just ten days. The multi-spectral instrument (MSI) will generate optical images in 13 spectral channels in the visible and shortwave infrared range down to a resolution of 10 metres with an image width of 290 kilometres.

The instrument is composed of two main parts:

• The telescope assembly , combining in one instrument both VNIR and SWIR channels, is mounted on the upper plate of the Bus

• The Video and Compression Electronic Units mounted inside the Bus.

This telescope is based on a Three Mirror Anastigmat optical concept. This three mirror optical combination is corrected from spherical aberration, coma and astigmatism. It provides a large field of view with very good optical quality. The telescope mirrors and structural baseplate are made of Silicon Carbide material in order to minimise thermo-elastic distortions. Isostatic mounts decouple the instrument from potential deformations of the platform upper plate.

The optical beam is spectrally separated thanks to a dichroic filter towards two different focal planes with different detector technologies: Silicon is used for the VNIR domain whereas Mercury Cadmium Telluride is required for the SWIR spectral domain. The VNIR detector is a CMOS device. The SWIR detector is a hybridised component where the MCT photosensitive arrays are hybridised on top of a CMOS circuit. The separation of the individual spectral bands(10 spectral bands, for the VNIR detectors and 3 spectral bands for the SWIR detectors) is performed by specific strip filters mounted on top of the detectors. The telescope is thermally decoupled from the external environment and the platform thanks to a thermal enclosure. A calibration and shutter mechanism avoids direct sun incidence inside the telescope during launch, specific platform manoeuvres and safe mode. The video signals coming out of the VNIR and SWIR focal planes are digitised and compressed inside the Video and Electronic Units prior to be sent to the bus.

Paper Details

Date Published: 21 November 2017
PDF: 6 pages
Proc. SPIE 10566, International Conference on Space Optics — ICSO 2008, 105660H (21 November 2017); doi: 10.1117/12.2308278
Show Author Affiliations
V. Cazaubiel, EADS Astrium (France)
Vincent Chorvalli, EADS Astrium (France)
Christophe Miesch, EADS Astrium (France)

Published in SPIE Proceedings Vol. 10566:
International Conference on Space Optics — ICSO 2008
Josiane Costeraste; Errico Armandillo; Nikos Karafolas, Editor(s)

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