Jun 16 1981
From The Space Library
NASA announced that Perkin-Elmer Corporation's Danbury, Connecticut, facility had finished shaping and polishing the 94-inch (2.4-meter) diameter primary mirror for the space telescope, main optical component of the telescope assembly. Launched on the Shuttle early in 1985, the 12-ton unmanned telescope would orbit at 600 kilometers (370 miles) above the interfering haze of Earth's atmosphere. It would be able to see objects 50 times fainter than observable from Earth telescopes, observing about 350 times more volume of space and 7 times further into space than now possible, up to 14 billion light-years. To make full use of this undistorted view of space, telescope parts had to be much more accurate than those in Earth telescopes. The mirror exhibited a deviation at any point on its surface of less than one millionth of an inch from an ideally perfect surface.
Manufacture of the mirror blank began in October 1977 at Corning Glass Works, which delivered it to Perkin-Elmer in December 1978. The blank was made of a Corning product called ultra-low-expansion glass, which has extremely low thermal expansion properties. Optical fabrication began with rough grinding of front and back surfaces of the blank, followed in August 1980 by fine polishing of the front surface, using; a computer-controlled polisher. The next stage of fabrication would be the application to the polished surface of two uniform extremely thin coatings, one a reflective layer of pure aluminum, the other a protective layer of magnesium fluoride to prevent oxidation of the aluminum. Coating would take place at Perkin-Elmer in the world's largest vacuum chamber, which operates at a vacuum very near that of space. After coating, the mirror would be installed in the optical telescope and aligned to the secondary mirror, focal plane, scientific instruments, and guidance sensors. The completed optical telescope would then be integrated into a support-systems module, a major element of the space telescope, under construction by Lockheed.
The space telescope project was managed by MSFC. (NASA Release 81-82)
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