New Space Telescope Mirrors Get Frosty Treatment
During cryogenic testing, the mirrors will be subjected to temperatures dipping to -415 degrees Fahrenheit, permitting engineers to measure in extreme detail how the shape of each mirror changes as it cools.
Credit: NASA/MSFC/David Higginbotham/Emmett Given

NASA is putting the mirrors for its ambitious new James Webb Space Telescope through the ultimate cold test ? one that exposes them to temperatures hundreds of degrees below freezing to make sure they will work in space.

Six of the space telescope's big beryllium mirrors were subjected to temperatures as low as minus 415 degrees Fahrenheit (minus 248 Celsius) so engineers could measure in extreme detail how their shape deformed as they cooled. 

The test will allow engineers to fine-tune the mirrors' polish so that next time they are cooled to cryogenic temperatures extreme cold bends them into the perfect shape

NASA's James Webb Space Telescope is slated to launch in 2014 to begin scanning the universe in the infrared range of the light spectrum to peer farther back into the universe's history than ever before.  The telescope's mission is expected to cost about $5 billion.

But first, its vital mirror system must pass their endurance trials.

The ultra-cold tests are being performed at the X-ray & Cryogenic Facility at NASA's Marshall Space Flight Center in Huntsville, Ala. The building is the largest X-ray facility to test big space telescopes.

These experiments tell scientists how well each mirror handles changes in temperature over a range of environments in space, NASA officials said in a statement.

The deep cold required by the space telescope's mirror system is around minus 379 degrees F (minus 228 Celsius), NASA said in a statement. Inside the operating telescope, the mirrors must be cooled to extremely low temperatures in order to generate a high sensitivity to faint infrared light. Otherwise, distant galaxies would be lost in the infrared glow created by the mirrors themselves. 

Ultimately, the James Webb Space Telescope will use a set of 18 connected mirrors to detect infrared light from space. The next set of telescope mirrors are expected to arrive at the testing site in August.