Making Webb’s mirrors
For each of the Webb’s 18 glimmering mirror segments, the journey to space began in the mountains of the western Utah desert — the only site in the
Western Hemisphere where beryllium is mined. The raw material was shipped to Ohio, where it was processed and pressed into “blanks,” one for each mirror segment. In
Alabama, these blanks were shaped and lightened by machining away some material, leaving a triangular pattern of ribs on their backsides. In California, their faces were ground and polished.
Then, Ball Aerospace in Colorado mounted the mirrors and began a series of optical tests. These continued in Alabama at NASA’s Marshall Space Flight
Center (MSFC), where Ball used a cryogenic vacuum chamber to measure the tiny distortions the mirrors will experience in the coldness of space. After post-processing back in Colorado, the mirrors received their final polishing in
California — performed precisely, to correct for the measured cryodistortion. After another stop in Colorado to be cleaned, the mirrors were sent to New Jersey to be coated with gold.
After Ball remounted the mirrors in Colorado and carried out more cryogenic checks at MSFC, the finished mirrors traveled to NASA’s Goddard Space Flight Center in Maryland, where the telescope was assembled. More cryogenic tests to the entire telescope were performed at NASA’s Johnson Space Center in Houston. Then, the telescope was shipped to California, where Northrop Grumman completed final assembly, attaching the telescope to the sunshade and spacecraft.