Spacewalking astronauts had to put a refurbished pair of gyroscopes
into the Hubble Space Telescope after a brand new set refused to go in Friday,
but scientists were satisfied nonetheless and confident the observatory would
point precisely to ever more distant objects in the
cosmos.
Replacing the gyroscopes was the top priority of
the repair mission, and the struggle had NASA on edge for two
hours.
Thanks to the spacewalkers' effort, Hubble ended up
with four brand new gyroscopes and two refurbished ones that were original
19-year-old telescope parts, said to be almost as good as the new ones. The
telescope also got fresh batteries.
It was the second
spacewalk in as many days for the Atlantis astronauts, who once again were
bedevilled by problems. On Thursday, another two-man team installed a powerful
new camera and a computer data unit, after struggling with a stubborn bolt. NASA
had hoped for an easier, less stressful spacewalk, but instead had to endure
more drama.
As on Thursday, the astronauts got their work
done, but it was harder and took longer than expected. Friday's spacewalk was
one of the longest ever, lasting nearly 8 hours, and Mission Control told the
weary crew members that they could sleep in and start Saturday's spacewalk a
little late.
Hubble chief scientist David Leckrone said he
had a pet theory on "why things have been a little turbulent for the crew for
two days in a row".
"After seven years of not having
people around, Hubble has lost its accommodation to people," Leckrone said at a
late Friday news conference. "It's gone wild again. So we have to tame it. That
will happen I'm sure."
And the first two spacewalks have
gone "a long way" to extending Hubble's life, Leckrone said. And Hubble's new
main camera installed on Thursday passed its functional
test.
Leckrone said Saturday's spacewalk, which is one of
the most challenging involving never-before done in-space repairs of a science
instrument, will probably go smoothly because that was his big worry. And
nothing has gone quite as expected, he said.
On Friday,
Michael Massimino, who was working from inside Hubble, and his partner, Michael
Good, had no problem removing all six of Hubble's 10-year-old gyroscopes. But
the last set of new gyroscopes wouldn't fit
properly.
Mission Control instructed the men to go get a
spare box of gyroscopes from the shuttle, and put that one in. This spare set
originally was launched aboard Hubble in 1990 and returned in
1999.
The astronauts successfully installed the
refurbished set. By then, however, five hours of the spacewalk had passed and
they had yet to start on the other major chore of the day, the battery
swap.
The gyroscopes were the No 1 task, though. Three of
the old gyroscopes no longer worked, and two others had been acting up. The
other had seen a lot of use.
"My friend Leonidas has a
couple of words for you guys that are appropriate right now," shuttle commander
Scott Altman told the spacewalkers, referring to the ancient Spartan king.
"Remember this day, men, for it will be yours for all time." Then Altman
laughed. Leonidas died in battle in 480 BC.
"We've got a
little more work to do, but thanks," replied
Massimino.
Hubble's deputy senior project scientist, Mal
Niedner, said he was not concerned the astronauts had to resort to refurbished
gyroscopes. They lack the latest anticorrosive wiring, but it's "the difference
between an A and an A-plus".
In all, five spacewalks are
planned so that the observatory - beloved by astronomers and many others for its
breathtaking views of the universe - is at its apex while living out its
remaining years. Scientists expect the upgraded Hubble to look back even further
in time, to within 500 million to 600 million years of
creation.
Good was so tired near the end of Friday's
spacewalk that he asked "Can I come in?"
Good drove in the
bolts for the gyroscope boxes as Massimino, a returning Hubble mechanic who is
over 1.8m tall, worked from inside the telescope, where he had wedged himself in
head first. "Trained my whole life for this," he
said.
Massimino had a brief scare when his communication
system fouled up at the start of the spacewalk. For a minute or two, no one
could hear him.
That wasn't the only unnerving thing about
this mission.
Space is particularly littered in this
560km-high orbit, and Atlantis and its crew face a greater risk of being slammed
by a piece of junk. As a precaution, NASA has a rescue shuttle on standby, ready
to launch in just three days if necessary.
Even though the
spacewalk was running behind, the astronauts pressed on and replaced some
batteries.
The hefty, nickel hydrogen batteries that came
out were built before the telescope was launched in 1990. They come three to a
pack, about the size of a big TV set with a mass of nearly 225kg. The final
three batteries will be replaced early next week.
The
unused new gyroscopes, meanwhile, will be analyzed once they're returned to
Earth.
NASA hopes to get another five to 10 years of use
out of Hubble, once the Atlantis astronauts plug in all the new equipment. They
also will take a crack at fixing two broken science instruments this
weekend.
The mission cost NASA more than US$1 billion,
one-tenth of what has been spent on Hubble over the
decades.
AP