NASA'S Next Generation Space Telescope Marks Key Milestone

HUNTSVILLE, Ala. -- The first six of 18 segments that will form NASA'sJames Webb Space Telescope's primary mirror for space observations will begin final round-the-clock cryogenic testing this week. These tests will confirm the mirrors will respond as expected to the extreme temperatures of space prior to integration into the telescope's permanent housing structure.

The X-ray and Cryogenic Facility at NASA's Marshall Space Flight Center in Huntsville, Ala. will provide the space-like environment to help engineers measure how well the telescope will image infrared sources once in orbit.

Each mirror segment measures approximately 4.3 feet (1.3 meters) in
diameter to form the 21.3 foot (6.5 meters), hexagonal telescope
mirror assembly critical for infrared observations. Each of the 18
hexagonal-shaped mirror assemblies weighs approximately 88 pounds (40
kilograms). The mirrors are made of a light and strong metal called
beryllium, and coated with a microscopically thin coat of gold to
enable the mirror to efficiently collect light.

"The six flight mirrors sitting ready for cryogenic acceptance tests
have been carefully polished to their exact prescriptions," said
Helen Cole, project manager for Webb activities at Marshall. "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."

During cryogenic testing, the mirrors are subjected to extreme
temperatures dipping to minus 415 degrees Fahrenheit (-248C) in a
7,600 cubic-foot (approximately 215 cubic meters) helium-cooled
vacuum chamber. This permits engineers to measure in extreme detail
how the shape of the mirror changes as it cools. This simulates the
actual processes each mirror will undergo as it changes shape over a
range of operational temperatures in space.

"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 one millionth of an inch," said
Scott Texter, Webb Optical Telescope element manager at Northrop
Grumman in Redondo Beach, Calif.

A second set of six mirror assemblies will arrive at Marshall in July
to begin testing, and the final set of six will arrive during the fall.
The Webb Telescope is NASA's next-generation space observatory and
successor to the Hubble Space Telescope. The most powerful space
telescope designed, 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 telescope
will orbit approximately one million miles from Earth.

"The Webb telescope continues to make good technological progress,"
said Rick Howard, JWST Program Director in Washington. "We're
currently developing a new baseline cost and schedule to ensure the
success of the program."

The telescope is a combined project of NASA, the European Space Agency
and the Canadian Space Agency. Northrop Grumman is the prime
contractor under NASA's Goddard Space Flight Center in Greenbelt, Md.
Ball Aerospace & Technologies Corp. in Boulder, Colo., is responsible
for mirror development. L-3- Tinsley Laboratories Inc. in Richmond,
Calif. is responsible for mirror grinding and polishing.
For more information about the James Webb Space Telescope, visit:


Source: NASA

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