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Hubble Error Due to Upside-down Measuring Rod

September 14, 1990

DANBURY, Conn. (AP) _ A worker accidentally inserted a 2-foot metal rod upside-down in a measuring instrument while making the Hubble Space Telescope’s primary mirror, causing a flaw that blurred the $1.5 billion scope’s view, NASA officials said.

″This particular day, he didn’t notice that the rod went in upside-down,″ said Charles Pellerin, director of astrophysics for NASA. ″So he made an ... error and never knew it.″

Pellerin spoke Thursday at a news conference at Hughes Danbury Optical Systems Inc., where a NASA investigative team had concluded two days of meetings. The company manufactured the Hubble’s primary mirror in the late 1970s and early 1980s when Hughes Danbury was a division of Perkin-Elmer Corp.

There was no way the person who inserted the rod could have known it was upside-down, said Lew Allen, director of NASA’s Jet Propulsion Laboratory, who led the investigative team. Allen declined to identify the person.

″It was a technical error made by people of good will who made a mistake,″ he said. The rod, made of the temperature-insensitive metal invar, was used in a measuring device that guided the polishing of the mirror, Allen said.

Because it was inserted incorrectly, it caused a 1.3 millimeter spacing error that led to the mirror being manufactured with a flaw, he said.

The flaw, called a spherical aberration, has blurred the view of the much- acclaimed Hubble. The orbiting observatory was supposed to take razor-sharp pictures of the outer reaches of space.

The flaw will be corrected during a previously scheduled 1993 space shuttle mission to replace the Hubble’s most powerful instrument, the wide-field planetary camera, said Pellerin.

It will cost an extra $15 million to build the new planetary camera to make up for the flaw, Pellerin said. The National Aeronautics and Space Administration originally estimated the new camera would cost up to $65 million, he said.

Many tests could have been done to detect the error during the manufacturing process, but Perkin-Elmer scientists and engineers didn’t do them because were under tremendous pressure to finish the project, Allen said.

The pressures, including cost overruns and time constraints, distracted those working on the mirror, he said. Also, some tests that had detected the error were considered unreliable at the time, he said.

″With 20-20 hindsight, one would clearly say there was negligence ...,″ Allen said. ″But you have to take into account the situation that actually existed.″

This was the investigative team’s third and final visit to Hughes Danbury, Allen said. The team will issue a final report on their findings as soon as possible, he said.

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