Corrections to fix Hubble telescope by 1994 to cost about $20 million

WASHINGTON - It will be four years late and cost an extra $20 million, but by early 1994 the Hubble Space Telescope should finally work the way it was supposed to.

The National Aeronautics and Space Administration is quietly moving to correct last year's great embarrassment: the discovery that a giant lens on the $1.5 billion telescope had been ground improperly, causing it to be nearsighted.

Although no formal announcement has been made, a NASA contractor is building corrective lenses that will be installed by spacewalking astronauts late in 1993 or, more likely, early in 1994. A replacement for the Hubble's jitter-causing solar arrays also is in the works

"The new Hubble will do everything the original could ever do," Charles Pellerin, director of NASA's astrophysics division, said in a recent interview. It will have, he said, "a couple of very tiny shortfalls, but it will be able to fulfill 97 percent of its complete scientific promise."

That promise was spectacular. "The Hubble Space Telescope will gather light from objects 25 times fainter than today's best telescope," one pre-launch blurb proclaimed. "It will see several times farther into space, and view objects with 10 times the clarity of the best Earth-based instruments. The telescope's optics are the finest ever created."

But a "spherical aberration" of the lens prevents the telescope from seeing the faintest light, which originated billions of years ago when the universe was young.

The Hubble's problems have been magnified by comedians and NASA detractors, but Pellerin said it is still "the best telescope in the world, bar none."

Its accomplishments, all at relatively close distances, include pictures of a remarkable storm on Saturn; seeing a star "incredibly rich" in platinum; finding a galactic jet stream of gas moving at hundreds of thousands of miles an hour.

NASA has not announced a final decision on the Hubble repair but the manufacturing is under way, Pellerin said. Plans are being drawn to train two astronauts to make three spacewalks each.

The first day, they will replace the Hubble's solar arrays that provide the telescope with electrical power for instruments and transmitters.

On the second day, the astronauts will replace the Hubble's Wide-Field Planetary camera. They also will install a 700-pound box called COSTAR. This device contains the mechanism to place pairs of mirrors the size of postage stamps in front of two spectrographs and a faint-object camera.

On the third spacewalk day, a new set of gyros will be installed in the Hubble, which has four sets of two. A few months ago, one of the gyros developed an electronic noise and it was shut down. The gyros are the instruments that tell controllers what movements the telescope is making.