EFFECTS OF SPACE EXPOSURE ON ION-BEAM-DEPOSITED SILICON-CARBIDE AND BORON-CARBIDE COATINGS

Two recently developed optical coatings, ion-beam-deposited silicon ca rbide and ion-beam-deposited boron carbide, are very attractive as coa tings on optical components for instruments for space astronomy and ea rth sciences operating in the extreme-UV spectral region because of th eir high reflectivity, significantly higher than any conventional coat ing below 105 nm. To take full advantage of these coatings in space ap plications, it is important to establish their ability to withstand ex posure to the residual atomic oxygen and other environmental effects a t low-earth-orbit altitudes. The first two flights of the Surface Effe cts Sample Monitor experiments flown on the ORFEUS-SPAS and the CRISTA -SPAS Shuttle missions provided the opportunity to study the effects o f space exposure on these materials. The results indicate a need to pr otect ion-beam-deposited silicon-carbide-coated optical components fro m environmental effects in a low-earth orbit. The boron-carbide thin-f ilm coating is a more robust coating able to withstand short-term expo sure to atomic oxygen in a low-earth-orbit environment. (C) 1998 Optic al Society of America.