We report progress in the fabrication of very low areal density (<5 kg/m{sup}2) optical mirrors usingspace-flight-qualified graphite-fiber-reinforced cyanate ester composite materials. Previous attemptshave been thwarted by fiber print-through at the surface. We find that the problem can besuccessfully overcome if the composite is processed to leave a very thin layer of resin at the surface.Results thus far include replicas with surface microroughness <1 nm rms, midfrequency ripples <3nm rms, areal density 2 kg/m{sup}2 at 42-cm aperture, and freedom from print-through aftervacuum drying and ion milling. The process is being extended to the fabrication of very lightweightmeter-class optics for space UV astronomy applications, x-ray optics, and other ground- andspace-based applications.
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