Knowledge of Hubble's flaw will aid repair

PASADENA, Calif. - Scientists so clearly understand the cause of the flaw that has crippled the highly touted Hubble Space Telescope that they believe the $1.5 billion instrument can be fully repaired during a shuttle mission in 1993.

Until the completion of an investigation led by Lew Allen, director of Jet Propulsion Laboratory, scientists feared that they might never understand the problem well enough to build corrective lenses for a replacement camera that was already scheduled to be installed by a shuttle crew in three years. But now that concern has been greatly eased.

"There is no doubt now that knowing precisely how the error was made, one can bring the performance of the telescope back to its original specifications," Allen said.

The committee of experts, established by the National Aeronautics and Space Administration after the discovery that the telescope could not be focused properly, blamed the failure on two errors. The mistakes caused the manufacturer to build a primary mirror for the telescope that "was the most precise mirror ever made, but precisely wrong," Allen said.

The investigators found that one critical piece of equipment was used upside down, and a narrow beam of light designed to pass through a pinhole in a lens cap reflected instead off the cap itself.