Hubble telescope panel says maker of flawed mirror withheld test data

November 28, 1990|By Luther Young | Luther Young,Sun Staff Correspondent

WASHINGTON -- An independent panel investigating the Hubble Space Telescope mirror flaw concluded yesterday that the manufacturer discounted and withheld critical test data that would have alerted NASA overseers to a problem during the fabrication of the huge mirror.

In the final report on its five-month study, the panel also scolded the space agency for accepting the "closed environment" at Perkin-Elmer Corp. of Danbury, Conn., that allowed the flaw to occur and to go undetected until after the $1.5 billion telescope's launch in April.

"Perkin-Elmer should not have allowed a situation that inhibited communication," said Lew Allen, chairman of the six-member Hubble Optical Systems Board of Investigation. "But NASA had the fundamental responsibility and should have been aware of what was happening."

But the 120-page "Optical Systems Failure Report" -- released yesterday at a news conference at NASA headquarters in Washington -- does not identify officials at Perkin-Elmer responsible for the slip-up, nor does it suggest that NASA now has evidence to sue the company for breach of contract.

"We're reviewing our options on that," said Lennard Fisk, associate NASA administrator for space science and applications. "It's premature to make that judgment. But the Allen report was one of the things we've been waiting for."

Other members of the panel were astronomer Roger Angel of the University of Arizona; John D. Mangus, head of the optics branch at Goddard Space Flight Center; George A. Rodney, NASA's quality assurance administrator; Robert Shannon, director of the Optical Sciences Center at the University of Arizona; and Charles Spoelhof, a retired vice-president of Eastman-Kodak.

The report confirmed earlier findings that the flaw -- which prevents accurate focusing on distant, faint celestial objects -- resulted because the primary mirror was precisely polished to the wrong shape, an error known as spherical aberration.

Perkin-Elmer's proposal to achieve and verify the correct shape involved sole reliance on a testing device called a reflective null corrector, described as an optical "template" used to guide the process of grinding and polishing the mirror to specifications.

When the investigative panel unearthed the null corrector, stored in Danbury for nearly a decade, testing revealed a spacing error of 1.3 millimeters in the placement of its optical elements that corresponded almost exactly to the amount of error observed in the Hubble mirror.

The cause?

Technicians assembling the null corrector inserted a metering rod between two lenses in the device upside-down and added washers to make up for a difference that resulted, apparently unaware that the "first opportunity to catch" the Hubble flaw had just been missed.

There were also later clues, "at least three cases where there was clear evidence that a problem had developed, and it was missed all three times," Dr. Allen said.

One involved a check on the mirror's radius with another device, known as a refractive null corrector, which clearly revealed the spherical aberration but which was discounted by Perkin-Elmer as a flaw in the less-sophisticated refractive null.

The report strongly criticized Perkin-Elmer for excluding overseers from within their own company and from Marshall Space Flight Center -- the NASA center that directed the project -- from "key areas and at critical times."

William Fastie, a retired Johns Hopkins University astronomer who served as a NASA consultant during the mirror's manufacture, said yesterday that "none of us saw any data that suggested anything wrong."

But the panel found NASA at fault for "inadequately staffing" the oversight function with qualified people. It also should not have accepted in the first place Perkin-Elmer's "fragile philosophy" of relying only on the reflective null corrector.

One curious revelation in the report was that Perkin-Elmer involved the very best optics experts in designing the mirror and in fabricating a smaller test mirror that helped the company win the contract.

But fabrication then was handed off to the Optical Operations Division, "which was insulated from review or technical supervision," the report said.

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