Evaluation of a silicon carbide telescope mirror for the vacuum ultraviolet

Abstract

Evaluations of the SiC demonstration telescope mirror for the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) instrument for the Solar and Heliospheric Observatory (SOHO) mission have been carried out at the Diffraction Grating Evaluation Facility (DGEF)1 at Goddard Space Flight Center. These evaluations include: image quality at 124 nm; scatter into off-specular angles at 124 nm; visible image quality; figure assessment using a ZYGO Mark IV interferometer; microroughness evaluation of the surface using a WYKO optical interference heterodyne profilometer; and scatter photographs of the mirror surface illuminated with a collimated beam at off-specular angles. An analytical model of the vacuum ultraviolet experiments has been developed2 to predict the experimental outcomes. Experiments are described and results are compared to analytical predictions based on the surface metrologic data gathered.