Lightweight, Segmented, Mostly Silicon Telescope Mirror

A document presents the concept of a curved telescope primary reflector structure, made mostly of silicon, that would have an areal mass density = 1 kg/m2 and would be deployed in outer space, where it would be operated at a temperature in the cryogenic range. The concept provides for adjustment of the shape of the mirror to maintain the required precise optical surface figure despite the flexibility inherent in the ultra-lightweight design. The structure would include a thin mirror layer divided into hexagonal segments supported by flexure hinges on a lightweight two-layer backing structure. Each segment would also be supported at three points by sets of piezoelectric linear microactuators that could impose small displacements along the optical axis. The excitations applied to the aforementioned microactuators would be chosen to effect fine adjustments of the axial positions and the orientations of the segments relative to the supporting structure. Other piezoelectriclinear microactuators embedded in the backing structure would enable control of the displacements of the segmentsalong the hexagonal axes; they would also enable control of the curvature ofthe backing structure and, thus, additional control of the curvature of the reflector.