This article is from the source 'bbc' and was first published or seen on . It will not be checked again for changes.

You can find the current article at its original source at http://news.bbc.co.uk/go/rss/-/1/hi/sci/tech/8054055.stm

The article has changed 12 times. There is an RSS feed of changes available.

Version 4 Version 5
Hubble's new spectrograph fitted Hubble's new spectrograph fitted
(40 minutes later)
Astronauts upgrading the Hubble Space Telescope have made a third spacewalk in as many days to make repairs deep inside the orbiting observatory.Astronauts upgrading the Hubble Space Telescope have made a third spacewalk in as many days to make repairs deep inside the orbiting observatory.
Mission chief mechanic John Grunsfeld delved into the interior of Hubble to replace computer circuitry that was never meant to be repaired in space. They ventured outside the shuttle Atlantis for more than six hours to install a new instrument.
He was joined by Andrew Feustel to install a new $88m (£58m) instrument. The $88m (£58m) Cosmic Origins Spectrograph will probe the formation of planets, stars and galaxies.
The Cosmic Origins Spectrograph (COS) will provide greater insight into how planets, stars and galaxies are formed. John Grunsfeld and Andrew Feustel also carried out physical repairs to Hubble's broken main camera.
The Advanced Camera for Surveys (ACS) was never meant to be repaired in space, but Atlantis' commander described the spacewalk as "smooth sailing".
The astronauts were able to restore the camera's wide-field channels, with which most of its astronomical observations are made. But a power problem was encountered during the check-out of its high-resolution channel.
This channel remains offline, but engineers are hopeful it can be revived another way.
HUBBLE SPACE TELESCOPE Named after the great US astronomer Edwin HubbleLaunched in 1990 into a 600km-high circular orbit Equipped with a 2.4m primary mirror and five instrumentsLength: 15.9m; diameter: 4.2m; Mass: 11,110kg In pictures: The best of HubbleHUBBLE SPACE TELESCOPE Named after the great US astronomer Edwin HubbleLaunched in 1990 into a 600km-high circular orbit Equipped with a 2.4m primary mirror and five instrumentsLength: 15.9m; diameter: 4.2m; Mass: 11,110kg In pictures: The best of Hubble
Mr Grunsfeld, a 50-year-old astronomer, and Mr Feustel, a 43-year-old geologist, also attached a new external power source.Mr Grunsfeld, a 50-year-old astronomer, and Mr Feustel, a 43-year-old geologist, also attached a new external power source.
As part of the seven-hour long operation Mr Grunsfeld removed 32 tiny screws using an assortment of hand ratchets and cutters. During the third extra-vehicular activity (EVA) of the mission, Mr Grunsfeld removed 32 tiny screws using an assortment of hand ratchets and cutters.
On Friday, the astronauts struggled to complete a critical repair to the telescope, refurbishing a pair of gyroscopes into the telescope after a new set refused to go in.On Friday, the astronauts struggled to complete a critical repair to the telescope, refurbishing a pair of gyroscopes into the telescope after a new set refused to go in.
The troubled spacewalk - the second - was the longest yet, lasting eight hours.The troubled spacewalk - the second - was the longest yet, lasting eight hours.
"At times, I felt like I was wrestling a bear," Mike Massimino was quoted as saying by AFP news agency, as he and Mike Good struggled to install the gyroscopes, or "rate sensing units" (RSUs)."At times, I felt like I was wrestling a bear," Mike Massimino was quoted as saying by AFP news agency, as he and Mike Good struggled to install the gyroscopes, or "rate sensing units" (RSUs).
Previously, only three of the six gyroscopes worked, now Hubble has four brand new sets and two refurbished ones. Only two are needed to orient the telescope properly.Previously, only three of the six gyroscopes worked, now Hubble has four brand new sets and two refurbished ones. Only two are needed to orient the telescope properly.
There have now been 21 spacewalks undertaken in the service of the 19-year-old observatory.There have now been 21 spacewalks undertaken in the service of the 19-year-old observatory.
On Thursday, the telescope's Wide Field Camera was replaced, giving the telescope an even deeper view into space - and back into the history of time.On Thursday, the telescope's Wide Field Camera was replaced, giving the telescope an even deeper view into space - and back into the history of time.
A data processing unit that failed in 2008 was also replaced.A data processing unit that failed in 2008 was also replaced.
There are no plans for further trips to Hubble after this mission ends which is why the repairs are so crucial.There are no plans for further trips to Hubble after this mission ends which is why the repairs are so crucial.
"We're enjoying the moment and savouring it... the goal is to make the next two days go as well as today went," senior spokesman for Nasa Preston Burch said."We're enjoying the moment and savouring it... the goal is to make the next two days go as well as today went," senior spokesman for Nasa Preston Burch said.
If all goes well, the fifth and final spacewalk is set for Monday and the telescope will be released from the cargo bay of the Atlantis shuttle on Tuesday.If all goes well, the fifth and final spacewalk is set for Monday and the telescope will be released from the cargo bay of the Atlantis shuttle on Tuesday.