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memetical's Avatar Jump to comment 21 by memetical

Lets not forget the grinding, polish'g and tests check'g error made to Hubbles primary mirror! . . . . . . .

"NASA has established how a mirror aboard its $1.5 billion Hubble Telescope came to be the wrong shape. The agency said last week that errors in a test instrument apparently led Perkin-Elmer, which fabricated the optics, to finish the 2.4-metre primary mirror of the Hubble Space Telescope incorrectly. Tests by NASA earlier this month showed that a lens in the test instrument, called the 'reflective null corrector', is about a millimetre askew. Preliminary analysis indicates that an error of this magnitude could cause the spherical aberration that prevents Hubble from focusing sharply. The crucial error, the misalignment of a lens by a millimetre, is 'very large' by optical standards, says Daniel Schroeder, an astronomer at Beloit College in Wisconsin, and a codesigner of Hubble. In some optical instruments, positions are measured to a fraction of the wavelength of light, less than a thousandth of a millimetre. Ironically, Perkin-Elmer ignored warnings ..." (NewScientist '90)

Fri, 15 Jun 2012 00:35:48 UTC | #947502