Performance of lightweight large C/SiC mirror

Abstract

Very lightweight mirror will be required in the near future for both astronomical and earth science/observation missions.Silicon carbide is becoming one of the major materials applied especially to large and/or light space-borne optics, such as Herschel, GAIA, and SPICA. On the other hand, the technology of highly accurate optical measurement of large telescopes, especially in visible wavelength or cryogenic circumstances is also indispensable to realize such space-borne telescopes and hence the successful missions.We have manufactured a very lightweight =800mm mirror made of carbon reinforced silicon carbide composite that can be used to evaluate the homogeneity of the mirror substrate and to master and establish the ground testing method and techniques by assembling it as the primary mirror into an optical system. All other parts of the optics model are also made of the same material as the primary mirror.The composite material was assumed to be homogeneous from the mechanical tests of samples cut out from the various areas of the 800mm mirror green-body and the cryogenic optical measurement of the mirror surface deformation of a 160mm sample mirror that is also made from the same green-body as the 800mm mirror.The circumstance and condition of the optical testing facility has been confirmed to be capable for the highly precise optical measurements of large optical systems of horizontal light axis configuration.Stitching measurement method and the algorithm for analysis of the measurement is also under study.

Examination of the Blank Error on Mirror Accuracy of Lightweight SiC Mirror and a Compensation Method

“…Due to the mass restrictions of rockets, the mirrors need to be lightweight designed. The goal of mirror design is to satisfy the requirements of mirror surface accuracy and location which are obtained by optical error analysis and technical specifications [3][4][5][6]. When designing the mirror assembly, these requirements should be taken as objectives and constraints.…”

A Finite Element Analysis for Improvement of Shaping Process of Complex-Shaped Large-Size Silicon Carbide Mirrors

“…Given this, it is deemed necessary to find an appropriate technique to fabricate a lightweight SiC ceramic optical mirror. For example, Yui et al [ 13 ] have attempted to optimize the manufacturing process of the lightweight large silicon carbide mirror, from designing the structure and mixing the raw material to final polishing. Zhang et al [ 14 ] utilized the finite element analysis method to investigate the stress and displacement distribution of the large-scale fabrication of the lightweight Si/SiC ceramic composite optical mirror under a factual condition.…”

Optical testing of lightweight large all-C/SiC optics

“…Photos of it are shown in the top of Figure 1. For details on HB-Cesic material and the manufacturing of the primary mirror, see [3,4,5].…”

“…Among the various types of carbon fiber-reinforced SiC materials, HB-Cesic is a material that was developed jointly by ECM and Mitsubishi Electric Corporation (MELCO) [3,4] and is not only very strong but also has improved uniformity and homogeneity. We selected this material for our large optics study program and manufactured 800-mm-diameter aperture, lightweight optics to verify and establish the technology of designing and manufacturing very lightweight mirrors for visible use, to shorten the manufacturing lead time including the polishing process of the mirror surface, to confirm the uniformity of the mirror material by applying the mirror to cryogenic surface figure measurement, and to master and establish the technology of ground optical testing using the mirror [5].…”