[meteorite-list] NASA'S Webb Telescope Completes Mirror Coating Milestone

[Ron Baalke]

Sept. 13, 2011

Trent J. Perrotto 
Headquarters, Washington 
202-358-0321 
trent.j.perrotto at nasa.gov 

Lynn Chandler 
Goddard Space Flight Center, Greenbelt, Md. 
301-286-2806 
lynn.chandler-1 at nasa.gov   


RELEASE: 11-298

NASA'S WEBB TELESCOPE COMPLETES MIRROR COATING MILESTONE

GREENBELT, Md. -- NASA's James Webb Space Telescope has reached a 
major milestone in its development. The mirrors that will fly aboard 
the telescope have completed the coating process at Quantum Coating 
Inc. in Moorestown, N.J. 

The telescope's mirrors have been coated with a microscopically thin 
layer of gold, selected for its ability to properly reflect infrared 
light from the mirrors into the observatory's science instruments. 
The coating allows the Webb telescope's "infrared eyes" to observe 
extremely faint objects in infrared light. Webb's mission is to 
observe the most distant objects in the universe. 

"Finishing all mirror coatings on schedule is another major success 
story for the Webb telescope mirrors," said Lee Feinberg, NASA 
Optical Telescope Element manager for the Webb telescope at the 
agency's Goddard Space Flight Center in Greenbelt, Md. "These 
coatings easily meet their specifications, ensuring even more 
scientific discovery potential for the Webb telescope." 

The Webb telescope has 21 mirrors, with 18 mirror segments working 
together as one large 21.3-foot (6.5-meter) primary mirror. The 
mirror segments are made of beryllium, which was selected for its 
stiffness, light weight and stability at cryogenic temperatures. Bare 
beryllium is not very reflective of near-infrared light, so each 
mirror is coated with about 0.12 ounce of gold. 

The last full size (4.9-foot /1.5-meter) hexagonal beryllium primary 
mirror segment that will fly aboard the observatory recently was 
coated, completing this stage of mirror production. 

The Webb telescope is the world's next-generation space observatory 
and successor to the Hubble Space Telescope. The most powerful space 
telescope ever built, the Webb telescope will provide images of the 
first galaxies ever formed, and explore planets around distant stars. 
It is a joint project of NASA, the European Space Agency and the 
Canadian Space Agency. 

Mirror manufacturing began eight years ago with blanks made out of 
beryllium, an extremely hard metal that holds its shape in the 
extreme cold of space where the telescope will orbit. Mirror coating 
began in June 2010. Several of the smaller mirrors in the telescope, 
the tertiary mirror and the fine steering mirror, were coated in 
2010. The secondary mirror was finished earlier this year. 

Quantum Coating Inc. (QCI) is under contract to Ball Aerospace and 
Northrop Grumman. QCI constructed a new coating facility and clean 
room to coat the large mirror segments. QCI developed the gold 
coating for performance in certain areas, such as uniformity, 
cryogenic cycling, durability, stress and reflectance, in a two-year 
effort prior to coating the first flight mirror. 

In the process, gold is heated to its liquid point, more than 2,500 
Fahrenheit (1,371 degrees Celsius), and evaporates onto the mirror's 
optical surface. The coatings are 120 nanometers, a thickness of 
about a millionth of an inch or 200 times thinner than a human hair. 

"We faced many technical challenges on the Webb mirror coating 
program," said Ian Stevenson, director of coating at Quantum Coating. 
"One of the most daunting was that all flight hardware runs had to be 
executed without a single failure." 

The mirror segments recently were shipped to Ball Aerospace in 
Boulder, Colo., where actuators are attached that help move the 
mirror. From there, the segments travel to the X-ray and Calibration 
Facility at NASA's Marshall Space Flight Center in Huntsville, Ala., 
to undergo a final test when they will be chilled to -400 Fahrenheit 
(-240 degrees Celsius). The last batch of six flight mirrors should 
complete the test by the end of this year. 

For images related to this story, visit: 

http://www.nasa.gov/topics/technology/features/webb-mirror-coating.html 

For more information about the Webb telescope, visit: 

http://jwst.nasa.gov   
	
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