Space Telescope goes into hibernation, observations halted

Monday, November 15th 1999, 12:00 am

By: News On 6

CAPE CANAVERAL, Fla. (AP) -- The Hubble Space Telescope went into hibernation over the weekend, its astronomical observations halted, when one of its pointing units failed, NASA said today.

The telescope will remain in this so-called safe mode, which is akin to being asleep, until space shuttle astronauts arrive to install new pointing devices, or gyroscopes, and other crucial replacement parts. The mission is set for next month.

The gyroscope, needed for aiming and holding the telescope steady, "just stopped in its tracks" on Saturday morning, said John Campbell, NASA's Hubble program director. The unit had been acting up for the previous 12 hours, becoming less and less accurate in its guidance, he said.

It was the fourth of six gyroscopes to fail on Hubble. A minimum of three are needed in order for the telescope to conduct
observations. When the gyroscope failed, Hubble's computer sensed the problem
and ordered the aperture door to be closed, Campbell said.

"It's quite safe," he said. "We're not doing science, so the power load has been reduced. But everything is quite OK." Campbell said "it could have been a lot worse," considering
that the next Hubble servicing mission originally was set for June 2000. The flight was split into two, and the first part scheduled
for this fall, when the third gyroscope failed in February.

Hubble was launched in 1990. Four of the six gyroscopes were replaced and its seven-man crew will take up six new gyroscopes, as well as another data recorder, radio transmitter
and improved computer. Liftoff is targeted for Dec. 6, almost two months late because of shuttle wiring repairs and an engine
replacement.

"We're certainly more anxious for it (the mission), that's for sure," Campbell said.
NASA never built the computer software that would have allowed Hubble to work with only two gyroscopes. "We had never seen a way that we could do science" with two gyroscopes, Campbell said. "So we designed it that if we were going to have less than three, that the easiest thing to do was to
build one safe mode that required none."
The two remaining gyroscopes were working fine, Campbell said.