Hubble Telescope Flaw Blamed on Faulty Manufacturing Tool

The defect that blurred the Hubble space telescope’s view of the heavens may have been caused by a flaw in an instrument used to measure the observatory’s mirror when it was built, officials said today.

Preliminary results of tests conducted on a device called a “null corrector” found spacings in the instrument were about 1 millimeter off from design specifications, according to a statement from the National Aeronautics and Space Administration.

“The reflective null corrector is an optical reference device, which was used to measure very precisely the surface figure of the (telescope’s) primary mirror during its manufacture” in 1981, the statement said.

The device was found in the factory in Danbury, Conn., where the mirror was built, by a NASA investigative panel led by Lew Allen of the Jet Propulsion Laboratory in Pasadena, which ordered the tests.

“Over the past two weeks tests have been run, systematically checking various aspects of this device,” the statement said.

“Preliminary results of a test conducted . . . (Wednesday) to look at the spacings of the elements in the corrector have revealed a clear discrepancy of approximately 1 millimeter between the design of the null corrector and the device as it now exists,” the statement said.

One millimeter is about 1/25 of an inch, or about the diameter of the point of a ball-point pen.

“Preliminary analysis indicates that a discrepancy of this magnitude could cause spherical aberration similar to that observed in the (telescope’s) primary mirror,” it said.