NASA's next generation space telescope marks key milestone

Apr 15, 2011
NASA engineer Ernie Wright looks on as the first six flight ready James Webb Space Telescope's primary mirror segments are prepped to begin final cryogenic testing at NASA's Marshall Space Flight Center in Huntsville, Ala. (NASA/MSFC/David Higginbotham)

(PhysOrg.com) -- The first six of 18 segments that will form NASA's James 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 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 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 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.

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SemiNerd
5 / 5 (1) Apr 15, 2011
Given the large number of potential catastrophic failure points in the deployment of this telescope, I am worried that it will fail before getting to where it is able to be used. However, given the enormous size of the telescope I am equally excited by the possibility of seeing further and clearer than we ever have before.

Crudo's on the team for this important milestone.
Moebius
not rated yet Apr 16, 2011
I hope the shuttle is still flying and able to service this if it runs into trouble deploying.
Eikka
4.5 / 5 (2) Apr 16, 2011
I hope the shuttle is still flying and able to service this if it runs into trouble deploying.


The shuttle can't go that far. Hubble was about the furthest away they could go with enough fuel left to get back, and it's only at 347 miles above the earth. If filled with fuel in-orbit I think it might have been possible to fly the shuttle to the moon and back, but that's still only 240,000 miles.

And then there's the further problem that to go further you need more speed, and to come back the shuttle would have to aim for and brake in the atmosphere, so even if it could go as far as the moon, it would burn up on coming home.

You really need a different kind of ship to travel in space. Preferably one that's about 200,000 pounds lighter than the space shuttle and has a motor you can run for months instead of seconds so you're not just travelling as the ball in a Newtonian space pinball.
Gthedon
not rated yet Apr 18, 2011
All true... yet the article did say that they were worried about malfunctions around the time of lift off... so i mean if something goes wrong during launch then telescope could be maintenance in earth orbit... no?
LKD
not rated yet Apr 20, 2011
Clearly we will not have another Hubble debacle. But is this that much better then using multiple smaller telescopes that are tied in an array?

If someone knows a reliable link to that topic, I would love to read about it more.