Flexible and Broadband Long-Wavelength Infrared Radiator Based on a Pixel Pattern Metamaterial for Space Cryogenic Applications

This study proposes the design of an ultra-far-infrared broadband metamaterial radiator for space cryogenic applications. To achieve a flexible broadband radiator without significant structural complexity, the proposed radiator employs a flexible glass sheet as an intermediate dielectric layer and a QR code-like pixel-patterned periodic metal structure. A genetic algorithm is used to design the radiator, followed by fabrication using microfabrication techniques. The results of the reflectance spectrum measurements by FTIR were in general agreement with the analytical results, thereby confirming the broadband radiation characteristics. The total hemispherical emittance, which is an evaluation index for space radiators, was estimated to be 0.57 at 20 K. Compared with the conventional radiator material of 80-μm black paint, the total hemispherical emittance was markedly enhanced, despite a film thickness ratio of 19.9 % and an area density ratio of 53.7 %. Therefore, the proposed radiator is expected to facilitate the development of cryogenic radiators with reduced weight and flexibility while minimizing the risk of contamination. This is a significant consideration for infrared astronomy missions that require cryogenic temperatures.