PUBLIC RELEASE DATE:

20-Mar-2014

Contact: Lynn Chandler Lynn.chandler-1@nasa.gov 301-286-2806 NASA/Goddard Space Flight Center

When you think of a mirror, there really isn't that much needed to describe it, but when you look at a mirror that will fly aboard NASA's next-generation James Webb Space Telescope, there's a lot to the anatomy of a mirror.

NASA's Webb telescope includes a primary, secondary and tertiary mirror. Although the relatively small secondary and tertiary mirrors are unique, it's the expansive primary mirror that has the most complicated anatomy with a number of components operating together to make the telescope work.

The mirrors were built by Ball Aerospace & Technologies Corp., Boulder, Colo. Ball is the principal subcontractor to Northrop Grumman for the optical technology and lightweight mirror system. Ball Aerospace also developed the secondary mirror, tertiary mirror and fine-steering mirror.

The raw power of any telescope is determined by the size of its main optic the bigger the first or "primary" optic, the betterand in the case of large telescopes, the optic is a mirror. Webb's primary mirror measures 6.5 meters (21 feet, 4 inches) across, and although that's respectable by ground-based telescope standards, it is absolutely huge for a space telescope. A mirror this large and in space is needed to capture the light from the most distant galaxies and stars in the universe, but it would too big to launch into space if it were one single piece, so that's why Webb's is composed of 18 smaller lightweight "segments" that can be folded up to fit into the nosecone of a rocket. Each of Webb's 18 hexagonal-shaped primary mirror segments measures just over 1.3 meters (4.2 feet) across, and weighs approximately 40 kilograms (88 pounds). All of the 18 primary mirror segment assemblies that will fly aboard NASA's James Webb Space Telescope have already arrived at NASA's Goddard Space Flight Center in Greenbelt, Md.

Each of the 18 mirror segments is not "just a mirror" but is a complex assembly of technologies that allows all of them to work together as one. Each mirror has an "anatomy" of many parts, from the reflective gold-coated Beryllium substrate or layer, down to a Beryllium structure of "whiffles" and a "Delta frame," plus precision actuators to position and shape the mirror, mounted on Backplane Interface Flexures.

"The complexity of the mirror assemblies comes from the fact that they are designed to be very lightweight, work at cryogenic temperatures below -400F, survive launch vibration and forces, be align-able on-orbit via actuators, and then stay aligned for up to two weeks as though they are a single large mirror," said Lee Feinberg, NASA Optical Telescope Element Manager for the James Webb Space Telescope at the Goddard Space Flight Center in Greenbelt, Maryland.

Beryllium Mirror Substrate (Smooth mirror surface)

See more here:

The amazing anatomy of James Webb Space Telescope mirrors