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.
This work was done by Eui-Hyeok Yang of Caltech for NASA’s Jet Propulsion Laboratory. For fur ther information, access the Technical Support Package (TSP) free online at www.techbriefs.com/tsp under the Physical Sciences category. NPO-42106
This Brief includes a Technical Support Package (TSP).
Lightweight, Segmented, Mostly Silicon Telescope Mirror
(reference NPO-42106) is currently available for download from the TSP library.
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Overview
The document is a Technical Support Package from NASA's Jet Propulsion Laboratory, detailing the development of a lightweight, segmented telescope mirror primarily made of silicon. This innovative design aims to address two critical requirements for large optical apertures: achieving a high degree of surface control while maintaining a low-mass deployable capability, and utilizing advanced membrane mirror technology for optical quality.
The core concept revolves around a re-configurable mirror technology that employs silicon mirror segments supported by flexures and microactuators. Each mirror segment is designed to allow for precise adjustments in curvature and alignment, which is essential for optimal optical performance. The system includes microactuators for both tip-tilt alignment (three per segment) and gap adjustment, as well as aperture curvature control (twelve per segment). This configuration enables the mirror to adapt dynamically to various operational conditions.
The approach to achieving this re-configurability involves the integration of cryogenic actuators with the flexure structure, allowing for significant travel and displacement adjustments at cryogenic temperatures, specifically at 20K and maintaining performance at 4K. This capability is crucial for space applications where temperature variations can significantly impact mirror performance.
The document also includes cross-sectional schematics of the mirror segments, illustrating the structural design and the arrangement of the microactuators and flexures. The emphasis on silicon as the primary material highlights its advantages in terms of weight and performance, making it suitable for space missions where every gram counts.
Overall, the document outlines a forward-thinking approach to telescope mirror design that leverages advanced materials and technologies to enhance the capabilities of future space telescopes. By demonstrating this re-configurable mirror technology, NASA aims to pave the way for more efficient and effective astronomical observations, potentially leading to significant discoveries in our understanding of the universe. The research and technology discussed in this package are part of NASA's broader initiative to share aerospace-related developments with wider scientific and commercial applications, fostering innovation across various fields.
