First Surface Flexible Optical Solar Reflectors - Technology and product development of first-surface flexible Optical Solar Reflectors

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The objective is to develop and qualify for GEO applications a new type of Optical Solar Reflector 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” 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 Interferential CERMET 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.


Lower costs and easier handling / assembly / grounding /repair than quartz OSRs; suitable for application on both planar and curved surfaces, with high fill factor.

Better performance than Second Surface Mirrors, and superior resistance to the space environment, from radiation to Atomic Oxygen.


The base product is a foil of coated polyimide tape of typical size 620 x 210 mm, that can be cut into smaller pieces with a scalpel or a razor blade. Typical properties at BoL are α ≤ 0.10, ε ≥ 0.80, and sheet resistance < 1E+6 /square. The product can be offered also with perforated interconnects to establish electrical contact between the two sides of the tape, with R < 2E+5 . Coating adhesion resists very well to TVAC, humidity, and bending, and thermo-optical and electrical properties remain extremely stable against ATOX, UV, electrons and protons.

System Architecture

The base product consists of polyimide film preferably 2-3 MIL having one side coated with the IC coating plus a thin layer of conductive ITO, and the second side glued to commercial non-conductive acrylic PSA. Grounding is via application of conductive tape onto the coated surface.

The perforated product utilizes conductive PSA and has a regular pattern of small perforations in the polyimide film, through which electrical contact is made between the ITO layer on the first surface and a metal layer on the second.  Grounding is established automatically upon application of the product onto 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.

Current status

Development phase completed with very minor degradation of properties after a test sequence including 100 Thermal Vacuum Cycles from -180°C to +180°C, GEO life doses of e- and p+, and 2800 ESH of UV radiation (EoT values were α < 0.13 and ε ≥ 0.79). Within the dose range explored, UV radiation has beneficial rather than detrimental effect on α. A separate test with ATOX indicates no mass loss and no measurable variation of thermo-optical properties after 2E+21 atoms/cm2.  
Qualification phase just started.

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