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Tuesday, 5 March, 2002, 13:55 GMT
Astronauts fit Hubble array
Astronaut Michael Massimino holds on to new assembly while being moved into position
"Incredible," said astronaut Michael Massimino
Two astronauts have attached a second solar array on the Hubble Space Telescope in the second of five spacewalks planned this week.

"Beautiful day for a spacewalk," said astronaut James Newman as he went out.

"Incredible," commented Michael Massimino, on his first walk in space.

Working 580km (360 miles) above Earth, the astronauts removed and packed away the old solar array, and then unpacked and lifted the new one into position - without any apparent difficulty.

'Working well'

The astrnauts have turned their attentions to replacing an unreliable steering mechanism. One of Hubble's four reaction wheels briefly malfunctioned in November.

On Monday, astronauts John Grunsfeld and Rick Linnehan spent more than seven hours replacing the first of the solar wings - or photovoltaic generators - which capture energy from the Sun to power the observatory.

Mission controllers reported that it was working well and had passed an "aliveness test".

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
The new wing arrays are smaller - each just eight metres long - but will deliver 20% more power than the old pair, damaged by eight years of wear and tear.

The HST is 12 years into a 20-year mission and has already established itself as one of history's finest scientific instruments, having proven the existence of super-massive black holes, witnessed the formative stages of solar systems and given scientists their best estimate yet for the age of the Universe.

But the current servicing mission, being undertaken by a seven-member crew on the Columbia shuttle, should substantially improve Hubble's abilities.

Nasa confident

The new Advanced Camera System (ACS) to be fitted later this week will be able to see finer detail and will have a much wider field of view than the Wide Field Camera that it replaces.

The trickiest upgrade, however, is likely to come on Wednesday, when Nasa has to "switch off" Hubble so astronauts can fit a new power control unit.

The spacewalkers will have to work fast to prevent the extreme cold of space doing damage to sensitive components on the observatory.

There is also no guarantee the power will come back on once the unit is installed - although Nasa says it is confident it will happen.

Columbia launched from the Kennedy Space Center on Friday and is set to land there on 12 March after releasing Hubble back into orbit.

See also:

02 Mar 02 | Sci/Tech
Nasa gives Hubble mission go-ahead
02 Mar 02 | Sci/Tech
Hitch threatens Hubble mission
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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