Gold Mirror Coatings for James Webb Space Telescope (JWST) 

Quantum Coating, Inc is pleased to announce a milestone in both optical coating and space exploration: The successful gold mirror coating on all flight optics for the Webb Telescope program. Over the past 15 months twenty-one of the most sophisticated and near irreplaceable optical elements were treated with Quantum's unique gold deposition process. All coatings were completed on schedule, meeting every requirement on every mirror.

Finishing all mirror coatings on schedule is another major success story for the Webb telescope mirrors" (Lee Feinberg, NASA).

It represents not just the coating event, but the completion of a huge engineering project" (John Mather, senior project scientist, JWST).

The James Webb Space Telescope's 18 special lightweight beryllium mirrors have to make 14 stops to 11 different places around the U.S. to complete their manufacturing. The 18 mirror segments will form the Webb telescope's huge primary mirror. There are 18 segments, because it takes a large mirror to look back farther in time than ever before. They come to life at beryllium mines in Utah, and then move across the country for processing and polishing. In fact, the mirrors make stops in eight states along the way, visiting some states more than once, before journeying to South America for lift-off and the beginning of their final journey to space. This graphic shows the different places they have to travel, and what is accomplished at each location. 

The principal assembly is the 6.5m Primary Mirror, which is an array of 18 hexagons, each 1.5m across and made from light weighted beryllium (Be). The telescope also has Secondary, Tertiary and Fine Steering mirrors. Transforming these mirrors from metal blanks took multiple trips across the US as they were machined, ground, polished and tested. The mirrors then traveled to Moorestown, NJ for the final, critical application of Quantum's proprietary reflective gold coating: a 120nm thick film that boosts the infrared reflectance to 99%.

The JWST demanded near-perfect precision in every aspect of the project, from handling the large, almost irreplaceable Be substrates, to achieving near-perfect thickness uniformity over 1.5m curved surfaces. Quantum delivered on each requirement while managing film reflectance, stress and durability with the ability to survive cryogenic cycling to near absolute zero.

"We are very proud," said Quantum President Dan Patriarca, "not just of our successful coating effort, but that we were able to play a very significant role in a scientific program of this magnitude. The technical challenges of this program, uniformity of less then 10nm over a 1.5M curved surface, high reflectivity from 0.8 to 26 microns and survivability in the extreme environment of outer space to name a few, presented a daunting task for our team. The successful completion of this program without error or exception has affirmed our competency and ability to meet such demands. It also expands our experience to take on similarly challenging programs in the future. We look forward to moving beyond this program and establishing ourselves as a premier coating house to the scientific community."

Quantum's involvement began in 2001, when the first gold coated Be samples were produced and dropped in liquid nitrogen, demonstrating their ability to withstand cryogenic temperatures. At that time, the program was known as Next Generation Space Telescope (NGST), replacing the venerable Hubble Telescope. In 2007 Quantum was awarded the contract for gold coatings on the telescope, by then known as James Webb Space Telescope (JWST), named for the NASA administrator.

Over the next two years, Quantum expanded to meet its new needs, investing in a new 1800ft2 Class 1000 cleanroom facility, a custom designed 96" coating chamber and a metrology laboratory with a variety of specialized instruments for testing reflectance, thickness, stress, roughness and cryo-cycling.

Four years later the investment has proved to be well worth it: the final primary segment was coated last month, bringing to a spectacularly successful end Quantum's 10 year involvement in the Webb Telescope program.


NASA astrophysicist Dr. Amber Straughn takes you on a quick journey of facts and images to explain what the Webb Space Telescope will tell us about the cosmos. Credit: NASA/Goddard Space Flight Center

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