With last Fridays' dedication by Tinsley Laboratories, of a new facility to grind and polish mirror segments for the James Webb Space Telescope to exacting degrees of accuracy, NASA's newest space observatory moved another step ahead.
Tinsley is part of a larger mirror manufacturing team, led by Ball Aerospace & Technologies, which includes Brush Wellman and Axsys Technologies. All are members of prime contractor Northrop Grumman's James Webb Space Telescope (JWST) design and development team.
The new 30,000-square-foot facility, in Richmond, Calif., is being equipped with nine specially designed computer-controlled optical surfacing (CCOS) machines that will perform high precision grinding and off-axis aspheric polishing.
Tinsley is also adding a state of the art optical test facility to control ambient temperature to one-quarter of a degree Fahrenheit to ensure precise measurements can be performed around the clock.
The new facility will enable Tinsley to process up to twelve JWST mirror segments simultaneously, completing the polishing of optical surfaces for JWST's 18 mirror segments in about two-and-a-half years. The first mirror segment, an engineering development unit, will be shipped to Tinsley next month.
"Tinsley's increased capacity will help us meet rigorous program requirements," says Maureen Heath, vice president, Civil Space, Northrop Grumman Space Technology.
"As a next-generation space telescope, JWST is pushing the edge of the envelope in design and manufacturing technology. We're pleased that Tinsley, with its understanding, experience and capability in manufacturing space telescope mirrors, is a teammate on this exciting program."
Using the JWST is a key mission in the president's Vision for Space Exploration strategy to search for Earth-like planets and potential life signatures on extra-solar planets. It will operate in an orbit about one million miles from Earth at the L2 Lagrange point after its launch, planned for 2011.
After initial polishing at Tinsley at room temperature, JWST's mirror segments will be tested at minus 243 degrees Celsius, or roughly minus 400 degrees Fahrenheit, in a cryogenic test chamber at NASA's Marshall Space Flight Center in Alabama.
The mirrors will then be returned to Tinsley's facility for further refinement and polishing to the final specifications at room temperature.
"We must polish the mirror segments at room temperature so that they make a perfect aspheric form at cryogenic operating temperatures, with only 20 nanometers maximum error," said John Kincade, vice president and general manager of Tinsley. (Twenty nanometers is about one 5,000th the thickness of a normal piece of paper.)
"We're able to do this with our proprietary CCOS equipment and precision metrology equipment, which has been specially designed and built for working on large optics to this precision."
Manufacturing the JWST's mirrors is a multi-step process that involves compressing beryllium into large segments called "blanks"; machining the blanks; grinding and polishing the mirrors; and incorporating the mirrors into optical assemblies and mounting them on the telescope structure.
Tinsley is a subsidiary of SSG Precision Optronics of Wilmington, Massachusetts. SSG Precision Optronics is a developer of major telescope and other opto-mechanical systems for spaceflight environments for both defense and civil applications.
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