Mirror, mirror . . .

Scientist says errors discounted in making of Hubble

DANBURY, Conn. - Errors detected during the manufacturing of the Hubble Space Telescope's flawed main mirror repeatedly were discounted by officials of the company that built it, a scientist assigned to the project says.

Dr. Robin Laurance, a scientist with the European Space Agency, which is attached to the NASA board investigating the mirror, said that from the beginning of the manufacture of the mirror, test results indicated that something "went radically wrong."

But each time, officials of the manufacturer, Perkin-Elmer Corp., discounted the test results because of their confidence in what they considered a flawless test device known as a reflective null corrector. That device showed the 94-inch primary mirror surface to be nearly perfect, Laurance said.

Investigators have found that a 1.3-millimeter spacing error in the null corrector - caused by a misplaced cap on a measuring rod - has resulted in the blurry images being transmitted from the $1.5 billion telescope, greatly reducing its capabilities.

Laurance said that repeated tests with a device called an inverse null - which took the place of the primary mirror in the test setup to check the alignment of the equipment - showed problems that were later discounted.

The alignment check with the inverse null was performed after every test on the mirror's surface during the polishing phase of manufacture, he said.

But, he explained, so long as the test equipment was found to be aligned properly, evidence of the other problems was discounted.

NASA officials already have said that at least twice during the mirror's manufacture a decade ago, yet another testing device, a refractive null lens, showed something amiss.

One of those tests with the refractive null - near the completion of the project in 1981 - showed the mirror to have a spherical aberration of the same magnitude that has crippled the Hubble. But those test results also were discounted, the officials have said.

"The real error, in my opinion, was that there was no requirement for an independent check," said Laurance.

Low-level officials of the company, now known as Hughes Danbury Optical Systems Inc., were aware of the conflicting test results but apparently did not report them to their supervisors, Laurance said. So far, investigators have not found evidence that NASA was aware of those results.