Apr 15, 2011 07:24 GMT  ·  By
Six of the 18 JWST mirror segments are being prepped to move into the X-ray and Cryogenic Facility, at the NASA Marshall Space Flight Center in Huntsville, Alabama
   Six of the 18 JWST mirror segments are being prepped to move into the X-ray and Cryogenic Facility, at the NASA Marshall Space Flight Center in Huntsville, Alabama

This week marks an important milestone for the James Webb Space Telescope project, say mission managers at NASA. The first six of 18 mirror segments on the future observatory are scheduled to begin non-stop cryogenic tests.

JWST will feature a large primary mirror assembly, which will have a diameter of 6.5 meters (21.3 feet). This device will be made up of 18 individual segments, hexagonal in shape, and which will have the capability to move separately from each other.

These segments need to be absolutely perfect if the telescope is to become capable of peering into the early Universe, and observing the first stars and galaxies that developed after the Big Bang.

Their surface needs to be absolutely flawless, and there is little room for error in polishing and coating the individual mirrors, say experts with the NASA Goddard Space Flight Center. The Greenbelt, Maryland-based GSFC manages the construction of the new observatory.

The 6 segments are are scheduled to begin tests this week are now housed in the X-ray and Cryogenic Facility at the NASA Marshall Space Flight Center (MSFC), in Huntsville, Alabama. This facility has the ability to replicate the conditions the mirrors will be subjected to while in outer space.

Conducting these investigations is absolutely necessary before the mirror segments are included in the permanent structure housing the JWST components. Using the MSFC compound, investigators will be able to determine how the observatory will see infrared light sources, once in orbit.

“The six flight mirrors sitting ready for cryogenic acceptance tests have been carefully polished to their exact prescriptions,” explains the MSFC JWST activities project manager, Helen Cole.

“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,” she goes on to say, adding that each mirror is about 1.3 meters in diameter, and that it weighs about 40 kilograms (88 pounds).

All the mirror segments are made of the light and strong metal beryllium, the NASA team says. Their surface is coated in a thin layer of gold, that contributes to increasing the mirrors' ability to collect light from extremely distant sources.

“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,” explains expert Scott Texter.

He is the JWST Optical Telescope element manager at the Northrop Grumman corporation, in Redondo Beach, California. The company is the primary constructor of the new telescope, which is scheduled to launch around 2015.

“The Webb telescope continues to make good technological progress. We're currently developing a new baseline cost and schedule to ensure the success of the program,” says the director of the JWST program, Rick Howard.