Astronauts start dangerous Hubble repair
Thursday 14 May 2009
Atlantis' astronauts grabbed the Hubble Space Telescope today, then quickly set their sights on the difficult, dangerous and unprecedented spacewalking repairs they will attempt over the next five days.
Hubble and Atlantis are flying in a 563 kilometre high orbit littered with space junk. And some of that debris put a bit of scare into Nasa late Wednesday afternoon. The Air Force noticed a 10 centimetre piece of debris was on a path to come close to the shuttle.
Left over from the 2007 Chinese destruction of a satellite during a weapon test, the debris was predicted to come within 2.7 kilometres of Atlantis.
It is close enough to watch, but far enough that Nasa determined it didn't need to move Atlantis out of the way, said agency space debris scientist Mark Matney.
The debris missed the shuttle and Mission Control let it pass by without noting it.
The international space station also is watching a different piece of debris at its lower altitude that has a slight chance of coming close on Friday.
The shuttle already has an ugly stretch of nicks from Monday's launch, but the damage is considered minor and poses no safety threat. Nasa continued to prep another shuttle, though, just in case Atlantis is damaged and the crew needs to be rescued.
Late Wednesday, Mission Control told astronauts that engineers determined Atlantis' heat shield was in such good shape that no extra inspection would be needed next week.
After seven years of orbital solitude, Hubble looked surprisingly well. Flight controllers gasped when the telescope first came into view.
"It's an unbelievably beautiful sight," reported John Grunsfeld, the telescope's chief repairman. "Amazingly, the exterior of Hubble, an old man of 19 years in space, still looks in fantastic shape."
Nasa astrophysics chief Jon Morse said when Hubble scientists and managers saw the first picture of Hubble there were "audible gasps of elation."
Nasa hopes to get another five to 10 years of dazzling views of the cosmos from Hubble, with all the planned upgrades, which should leave the observatory more powerful than ever.
Shuttle robot arm operator Megan McArthur used the 15-metre boom to seize the school bus-sized telescope as the two spacecraft sailed 563 kilometres above Australia.
Then she lowered the observatory into Atlantis' payload bay, where cameras checked it out.
Going into the mission, Hubble scientists and managers warned that Hubble might look a little ragged because it hasn't had a tune-up since 2002. But initial observations showed nothing major.
"Everybody's very excited up here, I can tell you," said Grunsfeld, who will venture out with Andrew Feustel. They will replace an old Hubble camera that's the size of a baby grand piano, as well as a science data-handling unit that failed in September and delayed Atlantis' flight by seven months.
Nasa Wednesday found a strange problem of odd particles around equipment in the cargo bay that are used for telescope repairs.
Along one hand rail, white particles look like someone had sprinkled large grain salt from a salt shaker on the rail "from one end to the other," deputy shuttle program manager LeRoy Cain said in a late afternoon news conference. He said it is probably debris that fell off insulation blankets.
The initial worry was that it could contaminate Hubble, but further examination showed that it should not be an issue, said Hubble repair mission operations manager Keith Walyus.
Astronauts will be told to "try to stay out of the way" of the particles, Cain said. There are places where they can grab the handrail and not touch debris.
This is the fifth time astronauts have called upon Hubble. The previous overhauls went well, but those repairs were straightforward, with spacewalkers pulling equipment in and out. This time, Grunsfeld and his team will venture into the guts of broken instruments.
"Don't hold us to too high a standard," Nasa space operations chief Ed Weiler warned before Monday's launch. "We're trying to do two things that we've never done before, take apart instruments that aren't designed to be taken apart in space and operated on by gloved astronauts, and fix them after pulling out 110 or 111 screws.
"That's one heck of a challenge."
Two teams of spacewalking astronauts - two men per team - will take turns stepping outside. Besides swapping out the old camera and science data unit, they will replace Hubble's batteries, gyroscopes and a pointing mechanism. They also will install fresh thermal covers on the telescope, along with a docking ring so a future spacecraft can guide the telescope into the Pacific Ocean sometime in the early 2020s.
And in the toughest challenge, they will open up the two broken science instruments to replace fried electronics.
The first spacewalk, swapping out Hubble's workhorse 15-year-old camera for a newer and better one, "is crucial," Morse said. "This is our highest priority science instrument."
Walyus compared Wednesday's grab of the telescope and Thursday's work to a baseball game: "We've got to the plate. Now we're ready to go."
No one will visit Hubble after the Atlantis astronauts leave next week, so Nasa crammed as much as it could into the five spacewalks and poured more than $1 billion into the mission.
Managers also chose two experienced spacewalkers who have been to Hubble before, Michael Massimino and Grunsfeld, who is making a record third visit.
Science Writer Seth Borenstein contributed to this report from Greenbelt, Md.
Taken from the New Zealand Herald
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