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Gold-coated Primary Mirror Segment — Fotopedia
Ball Aerospace lead optical test engineer Dave Chaney inspects six primary mirror segments, critical elements of NASA's James Webb Space Telescope, prior to cryogenic testing in the X-ray & Cryogenic Facility at NASA's Marshall Space Flight Center in Huntsville, Ala. The James Webb Space Telescope will be launched in 2014 to study the formation of the first stars and galaxies and shed new light on the evolution of the universe.

Credit: NASA/MSFC/David Higginbotham

More information: www.nasa.gov/centers/marshall/multimedia/photos/2010/phot...

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Segmented mirror

A segmented mirror is an array of smaller mirrors designed to act as segments of a single large curved mirror. The segments can be either spherical or asymmetric (if they are part of a larger parabolic reflector). They are used as objectives for large reflecting telescopes. To function, all the mirror segments have to be polished to a precise shape and actively aligned by a computer controlled active optics system using actuators built into the mirror support cell. The concept and necessary technologies were initially developed under the leadership of Dr. Jerry Nelson at the Lawrence Berkeley National Laboratory and University of California during the 1980s, and have since spread worldwide to the point that essentially all future large optical telescopes plan to use segmented mirrors.