Post-Flight Reflectance of COSTAR and WF/PC 2 Pickoff Mirrors Upon Their Return from Space

摘要

This paper summarizes a comparison of pre- and post-flight optical performance on optical components (mostly mirrors) from the Corrective Optics Space Telescope Axial Replacement (COSTAR) instrument and the Wide Field Planetary Camera 2 (WF/PC 2) pickoff mirror. These measurements were carried out after both the COSTAR and WF/PC 2 were retrieved from the Hubble Space Telescope in May of 2009 and returned to GSFC in July of 2009. Both of these instruments had a highly UV-reflecting coating of Al with a MgF2 layer on top for protection on their reflecting optics. We studied these in order to document the aging process on these coatings while in space for more than 15.5 years. When compared to data before flight and witness coupons kept on the ground, we find a severely degraded UV performance for the coatings that flew in space, particularly at the Lyman-a wavelength. Based on similar observations seen earlier on the WF/PC1 POM, the current degradation, of the latest optical components removed from HST, are a result of outgassing of substances such as hydrocarbons and silicone from nearby hardware on the spacecraft and UV light that photo-polymerize those materials on the mirror surfaces.