Design of lightweight primary mirror and metering structure for spaceborne telescope

Abstract

The spaceborne telescope assembly, which incorporates the primary mirror and secondary mirrors, baseplate, and metering structure, must retain the alignment after launch and during operation in space. A trend in spaceborne telescopes has been an increase in collection area and in resolution. Both of these demands in performance require larger primary mirror aperture sizes. Since the primary mirror often dominates the mass budget of the telescope, either of these options imply larger mass for the overall system. Technologies that enable lighter primary mirror will enable lower mass telescopes with larger apertures to reduce the launch costs of these missions. Primary mirror has much to gain from a significant reduction in areal density. Areal density is often limited by the stiffness to weight ratio of the primary mirror. Two key factors drive these criteria: telescope strucural characteristics and fabrication requirements. Major efforts in spaceborne telescopes have inspired research in lightweight optics. Also, metering strucure requires high stiffness, high dimensional stability and minimum obstruction of the telescope aperture to get high quality images. This paper describes a conceptual design trade studies that explores the structural views for the lightweight primary mirror as well as the metering structure in sub-metric class spaceborne telescope.