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Sue Nelson, Science Correspondent
"It will return to earth on Monday"
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The BBC's Cary Johnstone
"This is NASA's last space mission of the century"
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Nasa spokeswoman Kelly Humphries
Hubble is securely latched in place
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Thursday, 23 December, 1999, 21:43 GMT
Successful start to Hubble repairs

Astronaut John Grunsfeld John Grunsfeld during the eight-hour space walk

Two astronauts have completed an eight-hour space walk as they carried out the first of several vital repairs to the Hubble Space Telescope.

The astronauts, Steve Smith and John Grunsfeld from the shuttle Discovery, replaced six navigational gyroscopes, four of which were broken and had rendered the telescope useless to astronomers since mid-November.

The most important thing is that the gyros are in
John Campbell, Hubble project manager
Two more space walks are scheduled to replace the module's elderly computer and install a new guidance system.

But these first repairs are considered to have been by far the most important.

'Hello Hubble'

"Beautiful sight out here, John," Steve Smith said to mission control as he began the space walk. "Hello Hubble."

The two astronauts took turns to work inside the tight confines of satellite with just inches of clearance. Their work was made more difficult by stiff bolts, awkward latches and reluctant power tools.

Grunsfeld with drill Power tools helped the astronauts tackle stubborn bolts and latches

As the three units, each containing two gyroscopes, were installed, controllers on the ground began running initial tests.

"We watched as each of them got its power on - cheered each one of the six," said Hubble project manager John Campbell.

"The most important thing is that the gyros are in," he said.

The telescope needs a minimum of three functional gyroscopes to maintain its position in space and to gather information effectively.

Earlier, French astronaut Jean-Francois Clervoy snared the observatory with Discovery's 15-metre (50-feet) robotic arm.

"Houston, we have a good capture," he said. "We have a good grapple."

Controlled approach

It was an extraordinary manoeuvre given that both shuttle and telescope were moving side by side at 28,000 km/h (17,000 mph), some 600 km (370 miles) above Earth.

Unlike earlier approaches, the shuttle moved vertically towards Hubble while decreasing its speed from one metre per second at 600 meters from the telescope, to 0.02 metres per second at 36 metres.

Hubble Discovery caught up with Hubble over the Gulf of Mexico

"I am fantastically pleased," said John Campbell, Hubble programme manager at the Goddard Space Center in Maryland. "You can talk to an old friend on the phone but there is nothing like seeing him face to face."

As well as the broken gyros, Hubble has a broken radio transmitter, an outmoded computer and data recorder, peeling thermal blankets, and batteries that are increasingly prone to overheating.

Nasa hopes to sort all these problems over the next few days, with perhaps the blankets being the one exception.

Discovery's delayed launch means time is now short if the shuttle is to be back on the ground before millennium eve and any potential Y2K computer problems.

Christmas gift

If all goes well, Hubble will be released on Christmas Day - Nasa calls it a gift to the world's astronomers. The Hubble rescue mission has been a top priority for the space agency.

Discovery's crew is one of the most experienced the space agency has sent into orbit - an indication of the telescope's importance.

The Hubble images are the best images ever returned of the Universe," said Dr Ed Weiler, Nasa's associate administrator for space science.

The current servicing mission, STS-103, is the third in a series of five planned maintenance expeditions before Hubble's retirement, scheduled for 2010.

Discovery, the first manned shuttle flight in five months, should be back on Earth on Monday.

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See also:
23 Dec 99 |  Sci/Tech
In pictures: Space walk
20 Dec 99 |  Sci/Tech
Discovery blasts off on Hubble mission
13 Dec 99 |  Sci/Tech
Shuttle fuel pipe repaired
09 Nov 99 |  Sci/Tech
Hubble's house call
 |  Sci/Tech
Hubble shuts its eyes

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