Panel blames design defect for Hubble telescope problems

A design defect in a measuring device, probably compounded by human error in the device's assembly, caused the mirror flaw in the $1.5 billion Hubble Space Telescope, a federal panel said Thursday.

The panel had previously reported that there was a 1.3-millimeter spacing error in the assembly of an optic instrument used to guide the machines that ground the surface of the telescope's main mirror. As a result, the mirror was deformed and it is unable to produce the precise images its designers hoped to achieve.

On Thursday, the panel reported that the spacing error was specifically caused by a defect in a metering rod, a measuring device used in the assembly the optic instrument.

The defect in the device was reported by the team after two days of meetings at Hughes Danbury Optical Systems in Danbury, Conn., maker of the mirror. The team is lead by Dr. Lew Allen, director of NASA's Jet Propulsion Laboratory.

In a statement, Allen said his panel was "fairly confident" it has pinned down all the important details of how the telescope's mirror came to be flawed. "It appears that the board has obtained the necessary date to reconstruct the events," he said.

Thursday's brief statement is likely to be the last major technical revelation of the Hubble investigation. But Allen noted that the board's final report, due in November, would detail "various indications existing during the mirror manufacture process which could have revealed the problem but weren't recognized at the time."