[SatNews] The first completely finished primary mirror segment for NASA's James Webb Space Telescope has passed its final cryotest in the X-ray & Cryogenic Facility at NASA's Marshall Space Flight Center in Huntsville, Alabama.

This last successful cryotest demonstrates that the mirror segment, an engineering development unit and flight spare, has fully demonstrated its ability to meet the needs of the Webb Telescope program. Northrop Grumman Corporation (NYSE:NOC) is leading the Webb Telescope design and development effort for the space agency's Goddard Space Flight Center. Ball Aerospace, Boulder, Colorado, is the principal optical subcontractor for the Webb Telescope program, responsible for developing the telescope optics.

The mirror segment was recently coated to maximize its reflectivity in the infrared part of the spectrum. During the final cryotest, the mirror segment is chilled to -415 degrees F and telescope engineers take extremely detailed measurements of how the mirror's shape changes as it cools. Cryotesting verifies that the mirror will change shape into the exact optical prescription needed to accurately image distant stars and galaxies. The primary mirror engineering development unit will be closely followed by 18 primary mirror flight segments. The segments will be coated before the final cryotest at Marshall, the world's largest X-ray telescope test facility, which is also a unique site for cryogenic, clean-room optical testing. The James Webb Space Telescope is the world's next-generation space observatory and successor to the Hubble Space Telescope. The most powerful space telescope ever built, the Webb telescope will observe the most distant objects in the universe, provide images of the very first galaxies ever formed and see unexplored planets around distant stars. The Webb telescope is a joint project of NASA, the European Space Agency and the Canadian Space Agency.