For the Agenzia Spaziale Italian's (or ASI, the Italian Space Agency) PRISMA mission to be a success the namesake satellite required hyperspectral imagers, and in order for the designer of the hyperspectral instrument to successfully complete the task they required custom-designed infrared detectors. Sofradir, one of the world's largest developers of infrared imaging equipment, was happy to oblige.
PRISMA, or PRecursore IperSpettrale della Missione Applicativa (Hyperspectral Precursor of the Application Mission) is an Earth observation satellite intended to cover Europe and the Mediterranean region, and a platform for demonstrating new technologies. The five-year observation mission is designed to derive information about land cover, agriculture landscape, pollution, the quality of inland waters, status of coastal zones, soil mixture, and carbon cycle. The satellite may also have national security applications.
The PRISMA satellite, engineered by OHB Italia, a subsidiary of space and technology group OHB SE, is equipped with electro-optical instrumentation that combines a hyperspectral sensor with a medium-resolution panchromatic camera. Technology company Leonardo, prime contractor for PRISMA's hyperspectral instrument, solar panels, and power supply unit, turned to Sofradir to design a pair of infrared detectors that would serve as the heart of the hyperspectral instrument, each built around the Saturn model infrared detector.
The first is a Saturn 1000 x 256 resolution SWIR detector, with 30 µm pitch and a usable spectral band of 0.9 to 2.5 µm. The second is a Saturn 1000 x 256 VISIR detector with 30 µm pitch and a usable spectral band of 0.4 to 1.1 µm. The detectors are cooled via thermal link to a cold space-facing radiator, a system that Sofradir developed specifically for PRIMSA. The completed hyperspectral instrument can detect 239 hyperspectral bands of less than 12 nanometers wide each in the SWIR and visible range (400-2500 nm).
The PRISMA satellite was launched on the Vega rocket, from the Kourou, French Guiana Space Center, on March 22. A three-month testing phase will precede the beginning of operational activity in June 2019. The satellite will orbit the Earth at an altitude of 615 km and take up to 223 images per day, with each image encompassing 30 x 30 km.
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