Space telescope mirrors pass 'chill' test

HUNTSVILLE, Ala., Dec. 22 (UPI) -- NASA says it has completed cryogenic testing in Alabama for the final six primary mirror segments that will fly on the James Webb Space Telescope.

The Webb telescope has 21 mirrors, with 18 mirror segments working together as a large 21.3-foot primary mirror, and each individual mirror segment now has been successfully tested to operate at minus 387 degrees Fahrenheit, the space agency said in a release Wednesday.

The testing of the successor to the Hubble Space Telescope took place at the X-ray and Cryogenic Test Facility at Marshall Space Flight Center in Huntsville.

"Mirrors need to be cold so their own heat does not drown out the very faint infrared images," Lee Feinberg, at the agency's Goddard Space Flight Center in Greenbelt, Md., said. "With the completion of all mirror cryogenic testing, the toughest challenge since the beginning of the program is now completely behind us."

During the tests engineers took extremely detailed measurements of how each individual mirror's shape changed as it cooled to ensure each one will be the correct shape upon reaching the extremely cold operating temperature in deep space.

"This testing ensures the mirrors will focus crisply in space, which will allow us to see new wonders in our universe," Helen Cole, project manager for Webb Telescope mirror activities at the Huntsville facility, said.