Design of All-SiC Lightweight Secondary and Tertiary Mirrors for Use in Spaceborne Telescopes

We report on the design of the secondary and the tertiary mirrors used in lightweight assemblies made entirely of silicon carbide (SiC). The essential design points are weight reduction within the ac-ceptable deformation of the mirror surface by gravity release, temperature change, and vibration during or after space launch. To find a design that achieves the target requirements, we established finite ele-ment models for various candidate designs and subjected each one to wave front error analyses along gravity directions and in operation temperatures. We also calculated the natural frequencies of the can-didate assemblies. Our study suggested that a triangular cell with bipod flexure support can satisfy the target weight within the requirements.