A report proposes a design concept for synthesizing a reflecting telescope with a large-aperture (diameter ≈100 m) primary mirror from a sparse arrangement of four smaller (diameter ≈10 m) primary mirrors. The telescope would be placed in orbit for viewing Earth with high resolution. The primary and secondary mirrors would be mounted on a lightweight structure that would be deployed in orbit.
This work was done by Philip Moynihan of Caltech for NASA's Jet Propulsion Laboratory. To obtain a copy of the report, "Ultra-Sparse Aperture Concentrator with Full-Area Coverage," access the Technical Support Package (TSP) free on-line at www.nasatech.com/tsp under the Physical Sciences category.
NPO-21103
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Large-Aperture Telescope Synthesized From Small Mirrors
(reference NPO-21103) is currently available for download from the TSP library.
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Overview
The document presents a novel design concept for a large-aperture telescope intended for high-resolution Earth observation from orbit. Developed by Philip Moynihan at NASA's Jet Propulsion Laboratory, the design addresses the challenge of deploying large mirrors in space, which are constrained by launch size limitations. The proposed solution involves synthesizing a 100-meter diameter primary mirror using a sparse arrangement of four smaller 10-meter diameter mirrors.
The innovative approach, termed the Ultra-Sparse Aperture Concentrator, allows for full-area aperture coverage despite the limited number of mirrors. Each of the four 10-meter mirrors functions as a concentrator, and they are mounted on a lightweight, collapsible structure equipped with rotating arms. This design enables the mirrors to maintain alignment on an imaginary spherical or parabolic surface centered on a stationary secondary mirror. Over a period of several minutes, the motion of the primary mirrors sweeps out the area necessary to simulate a large, solid mirror.
The secondary mirror is integrated with adaptive optics to compensate for image distortions, enhancing the quality of the captured images. The telescope captures images on the focal plane during brief frame periods of 0.2 seconds. These images are then processed and synthesized to create a high-resolution image from the sequence of sparse-aperture images.
The document emphasizes the motivation behind this design, which stems from the need for high-resolution imaging in Earth observation missions from synchronous orbit. Traditional methods often require multiple strategically placed mirrors, but this new approach simplifies the configuration while still achieving the desired resolution. The rotating structure of the mirrors, combined with image summation techniques at the detector, enhances resolution and reduces the signal-to-noise ratio.
Overall, this work represents a significant advancement in telescope technology, providing a cost-effective and practical method for deploying large space mirrors in the near to mid-term. The Ultra-Sparse Aperture Concentrator not only meets the requirements for future Earth observation missions but also showcases innovative engineering solutions to overcome existing limitations in space telescope design.
