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StatusOngoing
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Status date2024-11-04
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Activity Code4D.067
The objective is to develop and qualify for GEO applications a new type of Optical Solar Reflector (from now on FF-OSR) that combines the high performance and durability of quartz OSRs with the easy handling and flexibility of Ag-FEP Second Surface Mirrors. The solution is based on patented “Interferential CERMET” (IC) coating technology designed and qualified for the extreme environments of the Bepi Colombo mission and now flying on the High Gain Antenna of the Mercury Planet Orbiter. With First-Flex, the IC coating is transferred from small rigid metal parts to large sheets of polyimide tape.
The main challenge is to ensure good adhesion and reduced mechanical stress between a fully inorganic coating and a thin polymer substrate.
Compared to quartz OSRs, FF-OSRs easier handling and application on both planar and curved surfaces, with higher fill factor and lower costs.
Compared to Second Surface Mirrors, FF-OSRs feature superior resistance to the space environment and all its ageing factors, from ATOX to radiation and Xenon ions.
The base product is a sheet of coated polyimide tape 610 x 200 mm, that can be cut into smaller pieces with a scalpel, razor blade, or cutting plotter. Key properties at BoL are α = 0.10 ± 0.01, ε ≥ 0.81, and sheet resistance Rs < 1E+6 Ω/square. FF-OSRs can also be offered with perforated interconnects that establish electrical contact between the two sides of the sheet, to ease grounding. Coating adhesion is excellent both at BoL and after storage, TVAC, and bending, and thermo-optical and electrical properties remain extremely stable against ATOX, UV, electrons and protons.
The base product is built on a polyimide sheet of Kapton HN or FPC, 2÷3 MIL thick. The front side of the sheet is coated with Interferential CERMET, a multi-layer coating topped by a thin layer of Indium Tin Oxide (ITO). The back side is glued to a commercial non-conductive acrylic transfer tape (3M 966 or 3M 9460). After applying the sheet to the radiator panel, grounding is established by a conductive strip glued to the IC coated surface.
FF-OSRs can also be offered with perforated interconnects. In this case the transfer tape is conductive (3M 9703), and the Kapton sheet has a regular pattern of small perforations and a metal layer on the second surface. The two sides of the sheet are in electrical contact and grounding is established automatically when the product is applied to the radiator panel.
The project consists of two phases, the first aiming at the development of the technology up to TRL 6, the second at the qualification of the technology for GEO missions.
The project was successfully completed and FF-OSRs are now qualified for application on 15-years GEO missions. Thermo-optical properties at the end of the qualification tests show negligible degradation, with αEoT < 0.12 and εEoT ≥ 0.79. Complementary tests indicate that FF-OSRs are also very resistant to Atomic Oxygen and to Xenon ions and fit for use in a much wider range of missions and environments, from LEO to cislunar. Results confirm that FF-OSRs combine the performance and durability of quartz OSRs with the easy handling of SSMs, at fair costs. Delta qualification for specific missions is currently underway and the product is expected to fly by 2026.
