Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: THURSDAY, June 28, 1990 TAG: 9006280685
SECTION: NATIONAL/INTERNATIONAL PAGE: A/12 EDITION: EVENING
SOURCE: Associated Press
DATELINE: WASHINGTON LENGTH: Medium
NASA's announcement of the problem Wednesday sent a shudder of disappointment through an astronomy community that has waited years for what were expected to be unprecedented views of the universe from the orbiting telescope.
The space agency said the focusing problem in the Hubble mirrors cannot be fixed from the ground and at least two of the five instruments aboard the spacecraft will be virtually useless until a repair mission is flown by the space shuttle.
Plans call for such a mission in 1993, but the National Aeronautics and Space Administration said it hopes to make the flight sooner.
The flawed mirrors on Hubble cannot be taken out and replaced by the shuttle, but replacement instruments could compensate for the misfocused mirrors with special optics.
"We are pretty optimistic that we can take out all of the aberration," said NASA scientist Ed Weiler.
An official of the Danbury, Conn., company that made the mirrors said the flaw may have been caused by a human error in testing of the primary and secondary Hubble telescope mirrors as they were being ground and polished.
"It appears that one of the elements may have been manufactured to a prescription that wouldn't give you the desired result," said Jack Rehnberg, chief of the space science office at the Hughes Danbury Optical Co. "It could have been a human error."
Rehnberg said the problem could be either in the primary or secondary mirror or the manner that the two work together.
Jean Olivier, Hubble deputy project manager, said the Hubble mirrors were tested individually on the ground but never as a combination because that would have cost "hundreds of millions of dollars."
Hughes Danbury Optical, then a division of Perkin-Elmer, built the Hubble telescope assembly under a $450 million contract that included performance incentives.
A NASA investigation, led by Lew Allen of the Jet Propulsion Laboratory in Pasadena, Calif., is expected to start this week.
Hubble was placed in a 381-mile orbit on April 25 amid dazzling promises by NASA that the telescope could revolutionize the human concept of the universe.
The telescope, circling the Earth far above the obscuring effects of the atmosphere, was expected to be able to see objects such as stars and galaxies that are 25 times fainter than those seen by telescopes on the ground.
For the first time, Hubble would permit humans to look up to 14 billion light years into space - some 84 billion trillion miles. This could give a glimpse of objects as they were just a few billion years after the "big bang" that is thought to have started the universe.
Instead, images captured by the flawed Hubble now will be little better than what can be done by telescopes on Earth.
"It is very disappointing, extremely disappointing," said Kim Leschly of the Jet Propulsion Laboratory.
"Many people were hoping to see new views of the universe. Now we'll have to wait. That's very, very disappointing," said David Koo, an astronomer at the University of California, Santa Cruz.
Blaming the mirrors came as a surprise because NASA had touted Hubble's 94-inch primary mirror as the smoothest large mirror ever made.
The focusing problems mean that a faint-object camera, designed to detect objects not otherwise visible, will see no better than instruments on the ground. And a wide-field camera will be virtually useless, NASA's Weiler said.
Three instruments that study stars in ultraviolet and infrared radiation will not be as seriously affected, although a high-speed photometer will be able to do "about half the science" scheduled, Weiler said.
Hubble has had problems from early in the program. It was originally scheduled for launch in 1986, but was delayed for four years when the shuttle fleet was grounded following the Challenger accident.
After the telescope was deployed in orbit on April 25, engineers learned that a cable was blocking rotation of an antenna. The problem was corrected by limiting the antenna movement. Then engineers learned that a computer program was pointing the telescope at the wrong points in the sky. Computer software was changed.
by CNB