Northrop Grumman is to begin mirror production within a few weeks for a redesigned, 6.5m (21ft)-aperture, James Webb Space Telescope (JWST). The programme has been restructured to reflect budget cuts and risk-reduction efforts, but the company says the JWST can still achieve its original goal of probing deep into the origins of the universe.
Mirror production will begin in advance of a systems requirements review by NASA, scheduled in late December, to establish the JWST's baseline design. The telescope is expected to be launched in August 2011, on an Ariane 5 donated by the European Space Agency.
A key theme of technical decisions to date has been to reduce the risk of the $825 million project. A Hubble Space Telescope-like in-orbit rescue is out of the question as the JWST will orbit at the L2 Lagrange point about 1.5 million km (930,000 miles) away. The telescope must be cooled to 30-55K so its payload of infrared optics and sensors can probe for the first signs of light that followed the Big Bang.
Beryllium has been chosen as the material for the primary mirror, which has been scaled back from a surface area of 29.5m2 (318ft2) to 25m2 and from 30 actively controlled segments to 18, because it was less risky than ultra-low-expansion (ULE) glass, says Charles Atkinson, Northrop Grumman deputy programme manager. ULE is easier to produce, but that advantage was offset by a lack of testing in an extreme cryogenic environment, he says.
Source: Flight International
