13 September 2011 Cryogenic performance of the JWST primary mirror segment engineering development unit
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Proceedings Volume 8150, Cryogenic Optical Systems and Instruments XIII; 815008 (2011); doi: 10.1117/12.892337
Event: SPIE Optical Engineering + Applications, 2011, San Diego, California, United States
Abstract
The JWST (James Webb Space Telescope) primary mirror consists of 18 hexagonal mirror segments each approximately 1.5 meters point to point. The mirror segments are constructed from a lightweight beryllium substrate with both a radius-of-curvature actuation system and a six degree-of-freedom hexapod actuation system. The manufacturing process for each individual mirror assembly takes approximately six years due to limitations dealing with the number of segments and manufacturing & test facilities. In order to catch any manufacturing or technology roadblocks, as well as to streamline specific processes, an Engineering Development Unit (EDU) was built to lead the mirror manufacturing flow. This development unit has all of the same requirements as the flight units and is actually considered to be one of the flight spare mirrors. The EDU was manufactured with a lead time of approximately six months over the other mirrors to assure adequate time to optimize each step in the manufacturing process. Manufacturing and tests occurred at six locations across the U.S. with multiple trips between each. The EDU recently completed this arduous process with the final cryogenic performance test of the mirror assembly taking place at Marshall Space Flight Center's (MSFC) X-Ray & Cryogenic Facility (XRCF). Testing included survivability tests to 25 Kelvin, hexapod & radius-of-curvature actuation systems testing, and cryogenic figure & prescription testing. Presented here is a summary of the tests performed along with the results of that testing.
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David M. Chaney, James B. Hadaway, Jake Lewis, Benjamin Gallagher, Bob Brown, "Cryogenic performance of the JWST primary mirror segment engineering development unit", Proc. SPIE 8150, Cryogenic Optical Systems and Instruments XIII, 815008 (13 September 2011); doi: 10.1117/12.892337; https://doi.org/10.1117/12.892337
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KEYWORDS
Mirrors

Cryogenics

Manufacturing

James Webb Space Telescope

Distortion

Computer generated holography

Interferometers

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