An optical solar reflector (OSR) is a component of a vehicle or machine designed to fly in outer space.
[1] OSRs are often used in Geostationary orbits, where high radiation levels would cause other thermal surface coatings to rapidly degrade.
This is due to the fact that the vast majority of geostationary orbits lie in the Van Allen Radiation Belt.
[2] Optical solar reflectors are a type of second surface mirror.
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