REDONDO BEACH, Calif., April 15, 2011 -- Today marks a significant milestone for NASA's James Webb Space Telescope mirror test program as the first six of the 18 flight mirror segments that have fully completed the mirror manufacturing process are readied for final cryogenic tests. The mirrors will once again experience the harsh temperatures of space in the X-ray & Cryogenic Facility at Marshall Space Flight in Huntsville, Ala., to verify they meet test program requirements.
Northrop Grumman Corporation (NYSE:NOC) is the prime contractor for the Webb telescope, leading a design and development team under contract to NASA's Goddard Space Flight Center in Greenbelt, Md.
"This final cryotest is expected to confirm the exacting processes that have resulted in flight mirrors manufactured to tolerances as tight as 20 nanometers or less than a millionth of an inch," said Scott Texter, Northrop Grumman Webb Optical Telescope Element manager. "It is a significant program accomplishment and an engineering marvel."
The mirrors are mounted to a test fixture and will undergo round-the-clock testing that will begin on April 15 and continue for eight weeks. This is the first of three acceptance tests for the flight mirror assemblies. A second set of six coated mirror assemblies are scheduled to arrive at Marshall in July, and a final set of six in the fall of 2011.
Each mirror segment measures approximately 1.32 meters (4.3 feet) in diameter flat-to-flat to form the 6.5-meter diameter (21.3 feet) hexagonal Webb telescope, critical for future infrared observations. Each of the 18 hexagonal-shaped mirror assemblies weighs approximately 40 kilograms (88 pounds) after light-weighting. The mirrors are made of beryllium and coated with a microscopically thin coat of gold to enable the mirror to collect light more efficiently.
"The six flight mirrors sitting ready for cryogenic acceptance tests have been carefully polished to their exact prescriptions and coated with an ultra thin gold coating," said Helen Cole, project manager for the Webb Telescope activities at NASA's Marshall Space Flight Center, Huntsville, Ala. "It's taken the entire mirror development team, including all the partners, over eight years of fabrication, polishing and cryogenic testing to get to this point. Seeing the mirrors arrive today is a testament to the entire team's hard work and dedication."
During cryogenic testing, the mirrors are subjected to extreme temperatures dipping to -415 degrees Fahrenheit (-248 C) in the 7,600 cubic-foot (~215 cubic meter) helium-cooled vacuum chamber, which permits engineers from Ball Aerospace and Technologies Corp., in Boulder, Colo., to measure in extreme detail how the shape of the mirror changes as it cools -- just as each mirror will change shape over a range of operational temperatures in space. The cryogenic test series helps NASA predict how well the telescope will image infrared sources in those conditions.
The Marshall Center has been performing cryogenic testing on the Webb telescope primary mirror segments since 2009 and will continue through 2012. Each mirror has been through the first of two cryogenic temperature tests required for each mirror segment at the Marshall Center. The first cryogenic test measures distortion of each mirror surface as it cools from room temperature to the Webb telescope's on-orbit operating temperature. This surface distortion is mapped and subsequently removed in the final mirror polishing operations. The second cryogenic test performed on each mirror will verify that the warm-to-cold surface distortion has been properly removed in final polishing.
The James Webb Space Telescope is NASA's next-generation space observatory and successor to the Hubble Space Telescope. The most powerful space telescope ever built, Webb will observe the most distant objects in the universe, provide images of the very first galaxies ever formed and help identify unexplored planets around distant stars. The Webb Telescope is a joint project of NASA, the European Space Agency and the Canadian Space Agency.
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CONTACT: Mary Blake Northrop Grumman (310) 812-6291 office (424) 254-6170 mobile email@example.com Dwayne Brown NASA Headquarters, Washington (202) 358-1726 firstname.lastname@example.org Kimberly Newton NASA Marshall Space Flight Center, Huntsville, Ala. (256) 544-0371 email@example.com Lynn Chandler/Rob Gutro NASA Goddard Space Flight Center, Greenbelt, Md. (301) 286-2806/(301) 286-4044 firstname.lastname@example.org email@example.com