Optical Solar Reflectors (OSRs) constitute the physical interface between radiator panels and outer space and allow for radiative cooling of the spacecraft. The performance of an OSR is defined mainly by two Thermo-Optical (T.O.) parameters: solar absorptance ? (the lower the better) and IR emittance ? (the higher the better). The market of OSRs is dominated by OSR quartz tiles, and by flexible Second Surface Mirrors (SSMs). Quartz OSRs exhibit excellent T.O. properties and durability, but are expensive and tend to break during assembly, integration and testing. Conversely, SSMs are easy to handle and apply, but age rapidly in space, due to the effects of UV radiation, charged particles and atomic oxygen on the polymeric support of SSM tape. First-Flex is a brand-new OSR technology that aims at combining the performance and durability of quartz OSRs with the flexibility and easy handling of SSMs, at fair costs. First-Flex consists of a fully inorganic coating sputter-deposited onto the first surface of polyimide film. The coating provides the required T.O. properties, while the film remains protected from the environment and serves only as mechanical support for the coating. First-Flex stems from a study for the Bepi Colombo mission, that led to the development and qualification of an extremely durable white coating named "Interferential CERMET" (IC), now flying around Mercury on the High Gain Antenna feed of the MPO. Subsequently, in the frame of the ESA ARTES AT and C&G programs, the IC coating was transferred from rigid metal substrates to polyimide tape, to be used as a flexible OSR. This paper reports on the final stages of development and industrialization of the technology and includes, in particular, the results of qualification tests for the application of Fiirst-Flex in various environments, including GEO.
Mengali et al. (Sun,) studied this question.
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