About Science-Nature – Hubble’s new spectrograph fitted
About Science-Nature –
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.
He was joined by Andrew Feustel to install a new $88m (£58m) spectrograph.
The instrument will provide greater insight into how planets, stars and galaxies are formed.
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HUBBLE SPACE TELESCOPE
 Named after the great US astronomer Edwin Hubble
Launched in 1990 into a 600km-high circular orbit
Equipped with a 2.4m primary mirror and five instruments
Length: 15.9m; diameter: 4.2m; Mass: 11,110kg
In pictures: The best of Hubble
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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.
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.
"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.
Last mission
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.
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 and 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.
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.
