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Saturday, 2 March, 2002, 20:17 GMT
Hitch threatens Hubble mission
Crowds watch Columbia streak away, AP
The launch was delayed because of cold weather
American space agency (Nasa) officials are meeting to decide whether to continue with the latest mission of the Columbia space shuttle after a problem was discovered in the craft's cooling system.

Spokesman Bill Jeffs told the BBC that the fault was still within the mission flight rule limits and the shuttle and its seven-person crew were not in any danger.

A decision on whether to push ahead with the mission is expected later on Saturday.

Columbia blasted off on Friday for an intended 11-day mission to service the Hubble Space Telescope (HST).

Hubble, Nasa/STSCI
Eagle Nebula: Hubble has produced so many great images
The launch, which was delayed by a day due to freezing temperatures, took place amid tight security - fighter jets were on a patrol and a 56-kilometre (35 mile) no-fly zone was established around the Kennedy Space Center.

The astronauts are scheduled to conduct at least five spacewalks to install new equipment and replace other worn-out components on the 12-year-old telescope.

The problem on the orbiter concerns the coolant loop that removes heat from the shuttle's electronics system.

Flight rules insist on two working loops, and one was slightly blocked, although ground controllers did not expect it to fail completely.

If Columbia has to return from orbit on Saturday, it will probably land at Edwards Air Force Base in California's Mojave Desert. The main landing strip at Kennedy is likely to be closed by bad weather.

The orbiting Hubble observatory has proved to be one of the triumphs of modern astronomy - it has taken some astonishing pictures of deep space - but could do even better science if it received an upgrade.

Dormant instrument

The upgrade will require Hubble to be completely powered down at one point and Nasa cannot guarantee that it will be able to switch the observatory back on again.

"That scares me a lot," Ed Weiler, the agency's head of space science said at a recent briefing.

"It kind of violates a long standing policy in the space business that if something is working well, you don't turn it off and just hope it comes back on."

The Columbia crew must fit Hubble with a new camera, solar wings, power-control unit, steering mechanism and a refrigerator system that should allow scientists to use an infrared camera that has lain dormant on the HST since 1999.

The most daunting part of the STS-109 shuttle mission will be the fitting of the new power unit, currently set for 5 March.

Hubble replacement

Astronauts John Grunsfeld and Richard Linnehan will first have to remove the degraded, old unit, "switching off" Hubble in the process.

It will then be a race against time to fit the new unit and power up the observatory again before the extreme cold of space does any damage to the telescope's instruments.

If the worst happens and Hubble cannot be turned back on, Nasa will have little choice but to abandon the observatory.

This would be a disaster, as the HST's replacement - the Next Generation Space Telescope - is still only in the design phase and is many years away from getting into orbit.

Hubble history
1977 - Project begins
1985 - Hubble built
1990, 24 April - Hubble launched
1990, 18 May - First light
1993, December - Flawed mirror corrected
1997, February - Second servicing mission
1999, December - Emergency service to repair gyroscopes
2002, March - Repairs not done in 1999
2010 - End of Hubble mission
Anne Kinney, Nasa's director of astronomy and physics, said: "Do we think we can do it all? Yes, we do. We wouldn't plan it if we didn't think that. But it is very ambitious. It's not easy. We'll worry all the way."

The mission is called the 3B servicing mission. It includes work not carried out when astronauts did an emergency repair on Hubble's gyroscopes in 1999.

If all goes well, Hubble will be back online to gather even more data about the Universe. Currently, it delivers daily between 10 and 15 gigabytes of data to astronomers all over the world.

This mission also marks Columbia's debut following the most extensive shuttle overhaul in years. The orbiter has not flown since July 1999, since which time it has undergone 133 modifications including the installation of a completely modernised cockpit.

The BBC's Emil Petrie
"This was its first return flight"
The BBC's Damian Grammaticus
"If two fail at the same time there might be a problem"

See also:

28 Feb 02 | Sci/Tech
High hopes for new Hubble camera
14 Apr 00 | Sci/Tech
Ten years of Hubble science
14 Apr 00 | Sci/Tech
Hubble's vision is blurred
14 Apr 00 | Sci/Tech
Building the first space telescope
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