National Aeronautics and Space Administration officials said each segment will be tested to make sure it will survive the extreme temperatures it will encounter in space.

The cryogenic testing will take place in a helium cooled vacuum chamber, chilling the mirrors from room temperature to minus 414 degrees Fahrenheit, NASA said. While each mirror changes temperature, engineers will measure its structural stability.

The James Webb Space Telescope will be a large, infrared-optimized space telescope and the premier observatory of the next decade, NASA said. It will have a large mirror, 6.5 meters (21.3 feet) in diameter that will consist of 18 segments, each about 1.5 meters (4.9 feet) in size.

NASA said the completed primary mirror will be more than 2 1/2 times larger than the diameter of the Hubble Space Telescope's primary mirror.

The James Webb Space Telescope is to be launched in 2013 and will be positioned about 1 million miles from Earth.