Abstract: The low energy proton in space radiation environment results in solar absorptance increase of external thermal control coatings since low-energy proton deposits all its energy at surface.The experiments of low proton irradiation test was performed for six types of thermal control coating as S781 organic white paints,SR107-ZK organic white paints,ACR-1 organic white paints,OSR second-surface mirror,F46 second-surface mirror,and Kapton second-surface mirror. The 48keV proton irradiates theses samples for about 360 hours under vacuum condition, accumulated flux to 2×10~(15) p/cm~2.The in-situ measurements for solar absorptance were carried out during irradiation.All six thermal control coatings increase in different extent.The organic white paints are the highest one.Two polymer film second-surface mirrors are the second.The OSR sec- ond-surface mirrors is the best stable in solar absorptance.SEM and XPS analysis shows that the structure of ZnO pigments,polymerized film and bond are degraded during irradiation of low- energy protons,making high reflective pigment and transparent polymer dark and opaque,causing increases of solar absorptance of thermal control coatings.

Key words: Thermal control coatings, Proton irradiation, Solar absorptance, Space environment, Satellite