The project aims at delivering a radically new type of smart and flexible OSR. That is, an Optical Solar Reflector (OSR) that combines easy handling, durability in space, and temperature variable emissivity.

The SMART-FLEX OSR is an extremely thin, fully inorganic, metamaterial coating deposited on the first, space-facing surface of a flexible foil, that can be easily glued on the outer skin of radiator panels, or of any other curved or bendable structure directly exposed to the space environment.

The foil rejects solar radiation, and regulates passively – without the intervention of the thermal control system – the heat exchanged between the satellite and the space environment, so avoiding overheating in the hot phase, and overcooling when the satellite is in eclipse or in safe mode.

The coating consists primarily of a three-layer structure known – in the jargon of the plasmonic community -as a Perfect Metamaterial Absorber (PMA): a metal ground-plane (bottom layer), a dielectric spacer, and a 2D array of nano-antennas made of thermochromic material.

At high temperatures, the interaction between the conductive nano-antennas and the ground plane generates close to unit broadband absorption in the thermal IR (that is high emissivity), matched to high reflectivity in the solar spectrum.

Below the transition temperature of the thermochromic material, the nano-antennas become dielectric and plasmonic resonance is inhibited, causing a substantial reduction of emissivity.

The PMA can be completed with a few additional layers grown on top of the nano-antennas, that improve the thermo-optical performance of the coating and provide protection against ageing and electro-static discharge.