Studies in thin diffraction gratings for flight applications

The quest for maximum throughput in high energy astronomy instruments has influenced an increasing trend in spectrograph design toward closely packed mirror and grating arrays. Gratings have additional challenges to those required for mirrors and are evaluated separately in this study. Since these instruments typically operate above earth's atmosphere, grating arrays are subject to a launch vehicle environment. Packing gratings close together in a confined space decreases substrate thickness below traditionally accepted standards for maintenance of surface figure. The everpresent pressure to minimize mass in flight payloads drives substrates even thinner. The University of Colorado has performed a study of several methods that may be employed to make thin gratings. In this paper, some traditional techniques are compared to less conventional ideas for using thin substrates. Environmental effects necessary for flight applications are also folded into the analysis for each thin grating type.