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- SPACE, Page 78Roots of the Hubble's Troubles
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- NASA could have spotted the telescope's flaw before the launch
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- By David Bjerklie -- Reported by Jerry Hannifin/Washington
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- Anyone can make a mistake. But when it sabotages a $1.5
- billion project, the blunder is not easily forgiven. And when
- evidence of the mistake is repeatedly ignored until it is too
- late to fix the problem, then the episode becomes scandalous.
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- That was the case with the ill-fated Hubble Space Telescope,
- according to a remarkably frank investigative report issued
- last week by the National Aeronautics and Space Administration.
- The flaw that crippled the telescope's primary mirror was not
- obvious until after the instrument was launched last spring.
- Yet technicians at the company that made the mirror had
- indications of trouble long before the telescope went into
- space -- and apparently never told the design team about the
- disturbing signs. Meanwhile, managers at NASA who had
- responsibility for the Hubble project paid little attention to
- the details of the telescope's construction. "There were at
- least three cases where there was clear evidence that a problem
- had developed, and it was missed all three times," said Lew
- Allen, the director of NASA's Jet Propulsion Laboratory and the
- head of the six-member investigating committee that wrote the
- Hubble report.
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- There was more than enough time to catch the telescope's
- flaw. Rough grinding of the mirror began in 1978, final
- polishing was not finished until 1981, and the completed
- telescope sat on the ground for four years after the space
- shuttle program was disrupted by the Challenger explosion. The
- mirror's manufacturer, Connecticut-based Perkin-Elmer Corp.,*
- told NASA that the standards of precision established for the
- mirror were not only met but exceeded. The only problem was that
- the mirror had been painstakingly polished into the wrong
- shape.
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- To achieve the exacting specifications for the mirror,
- Perkin-Elmer used an optics template, a tubular array of
- smaller mirrors and lenses linked by connecting rods, to guide
- the grinding and polishing processes. When the Allen committee
- tested this template assembly, it found that there was a
- critical error of 1.3 mm (0.05 in.) in the placement of the
- template's components. The Hubble mirror was carefully fashioned
- to match exactly this error in the template.
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- What was worse, the company's reliance on this system was
- absolute. Though backup analyses pointed to a major flaw in the
- mirror, stated the report, these "indicators of error were
- discounted at the time as being themselves flawed." The
- evidence of the problem was never analyzed in detail by the
- engineers and scientists most qualified to do so. NASA accepted
- Perkin-Elmer's decision to rely solely on the precision of the
- template, when instead the space agency should have been alert
- "to the fragility of the process and the possibility of gross
- error."
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- Fortunately, the damage is not beyond repair. NASA plans to
- perform an in-orbit service call on the space telescope in
- 1993. In the meantime, pictures from the Hubble can be
- sharpened by computer enhancement. The telescope has taken some
- surprisingly good shots, including images of a gas jet
- streaming from a newborn star and a huge storm on Saturn.
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- But the Hubble cannot focus on distant stars nearly as
- sharply as had been expected. Its performance was compromised
- by mistakes that were easily avoidable. That is clear even
- without the benefit of optically perfect hindsight.
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- * The company's optics division has since been sold to a General
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- Systems.
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