Optical polishing of JWST's first flight-mirror segment is complete

Oct. 8, 2010
The first flight-mirror segment for NASA's James Webb Space Telescope's primary is now polished; it is one of 18 segments that will make up the observatory's 21 ft primary mirror.

Redondo Beach, CA--The first flight-mirror segment for NASA's James Webb Space Telescope (JWST) primary mirror has completed its final polishing process. It is one of 18 segments that will make up the observatory's 21 ft primary mirror. (This same mirror segment completed its "cryopolishing"--an earlier step--in March of this year.)

The JWST is the successor to the Hubble Space Telescope. Northrop Grumman Corporation (NYSE: NOC) is leading the design and development effort for NASA's Goddard Space Flight Center.

"With the contributions of our JWST subcontractor L3-Tinsley, we've put forth a sustained effort over a number of years to achieve this milestone," said Scott Willoughby, Webb Telescope program manager for Northrop Grumman Aerospace Systems.

The optical fabrication, including high-precision grinding, aspheric polishing, and testing, is being done at Tinsley Laboratories (Richmond, CA). Each mirror segment is polished and tested at least 30 times. After each polishing cycle, the mirror segment is cooled to 80K in a liquid-nitrogen chamber to ensure that when the mirror segment reaches cryogenic temperatures, it will change its shape into the exact optical prescription needed for the mission.

The mirror segment will next be sent to Quantum Coatings (Moorestown, NJ) where it will receive a 120-nm-thick reflective gold coating. It will next be shipped to Ball Aerospace where actuators will be added, and then on to NASA's Marshall Space Flight Center (Huntsville, AL), for a cryotest at near absolute zero. The first mirror segment will be closely followed by the remaining 17 segments.

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About the Author

John Wallace | Senior Technical Editor (1998-2022)

John Wallace was with Laser Focus World for nearly 25 years, retiring in late June 2022. He obtained a bachelor's degree in mechanical engineering and physics at Rutgers University and a master's in optical engineering at the University of Rochester. Before becoming an editor, John worked as an engineer at RCA, Exxon, Eastman Kodak, and GCA Corporation.

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