Development of critical technologies for high-precision space optics

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We have performed the development and characterization of the graphite cyanate composite pipes for high-precision space optics such as the planned SOLAR-B satellite. Fundamental mechanical. thermal, and hygroscopic properties of unidirectional graphite-cyanate laminates were evaluated. The orientation of the fibers of a model pipe structure was designed to minimize the longitudinal thermal deformation. A model pike was fabricated based on the design, and we have performed series of measurements to evaluate the thermal expansion behavior (a few 0.1 ppm), the hygroscopic performance (10times better than the conventional graphite-epoxy composite), the thermal conductivity (111 w/mk), and the long-term stability. Excellent performance was verified, and the composite material was turned out to be the most promising candidate for the next-generation space-optics.We then proceeded to the design and fabrication of the ultra light-weight mirror that can be used as the primary mirror of a solar space telescope. The mirror consists of zerodure glass thin mirror supported by the graphite cyanate composite structure. The surface plate of the graphite cyanate composite structure that interfaces the glass mirror has an CTE matched to that of the glass over the surface, and the back-structure behind it has a large thermal conductivity to dump the heat load on the glass surface. The glass surface was polished to paraboloid with surface figure error as high as lambda/44 (lambda=633 nm), after the assembly of the structure (glass plate + composite material back structure). However, further investigation is needed to improve the long term stability of the surface figure.