Broadband Reflective Coating Process for Large FUVOIR Mirrors

ZeCoat Corporation will develop and demonstrate a set of revolutionary coating processes for making broadband reflective coatings suitable for very large mirrors (4+ meters). Decades of research and flight missions (Hubble, GALAX and FUSE) have utilized metal fluorides such as, MgF2 and LiF, applied to Al to achieve FUVOIR coating requirements. While metal fluoride-protected Al remains the best option for meeting broadband reflectance requirements (90-nm to 2500-nm), ZeCoat offers a means to build upon the best known and proven coating recipe (the GSFC 3-step process) by: 1) utilizing ZeCoat's unique precision motion-controlled deposition system to uniformly apply a 5-nm layer (a requirement of the GSFC recipe) of coating material to a large coating area, 2) protecting mirror assemblies from damaging high temperatures by heating only the mirror surface using radiant heat (the GSFC process requires a 220C metal-fluoride deposition temperature), 3) using an FUV reflectometer (120-nm to 180-nm) integrated into the coating chamber to optimize the coating process for FUV reflectance and 4) investigating the feasibility of using a layer of Sn to protect LiF from degradation due to atmospheric moisture and organic contamination during ground storage and re-evaporate the Sn once the observatory is placed in-orbit.