Hubble project officials, however, were not quite ready to call the rescue a done deal. Still to come: a functional test of the new guidance sensor, which will be carried out overnight by engineers at NASAs Goddard Space Flight Center in Greenbelt, Md.
"So far, were just thrilled with everything thats been done, and everything thats been done looks good," Hubble senior project scientist David Leckrone told space.com. "I just like to always be cautious and not say its over until its over."
What turned out to be an 8 hour, 10-minute spacewalk -- the third longest ever -- began Thursday afternoon as shuttle Discovery soared more than 360 miles above the Australian continent.
Decked out in bulky white spacesuits, Foale and Nicollier floated out of Discoverys airlock hatch at 2:06 p.m. EST, and in doing so, the latter became the first European to perform a spacewalk from the shuttle.
"Welcome to the [spacewalk] fraternity," astronaut Steven Smith radioed the Swiss astronaut from inside Discoverys flight deck.
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| Coupled with the repair Wednesday of Hubbles failed pointing control system, the laborious servicing job completed all work NASA said the spacewalkers must finish in order to consider the $205 million mission a complete success. |
Decked out in bulky white spacesuits, astronauts Foale and Nicollier floated out of Discoverys airlock hatch at 2:06 p.m. EST, and in doing so, the latter became the first European to perform a spacewalk from the shuttle. |
The only other hitch that cropped up during the excursion came when a medical sensor glitch erroneously indicated that carbon dioxide levels had soared to dangerous levels within Nicolliers spacesuit. |
"Thanks. Its a pleasure," said Nicollier, who is trained as an astrophysicist. "Its a great privilege to work on Hubble for the astronomical community all over the world."
Nicollier, a veteran of three previous shuttle flights and a robot arm expert, was obviously elated as he took in the expansive view of the blue orb Earth from his orbital perch.
"Well Claude, what do you think?" Smith asked.
"Wonderful. Beautiful," Nicollier replied.
With the four-story telescope towering at the rear of the shuttles cargo bay, Foale and Nicollier first opened an equipment compartment housing the old computer before removing it.
Working with stiff spacesuit gloves that are difficult to manipulate, the task called for Foale to unhook nine computer connectors. Foale then pulled the old computer which is about the size of a breadbox out of the telescope so Nicollier could stow it in a cargo bay storage bin.
Nicollier then handed the new computer to Foale, who placed it within the telescope before hooking up its cable connectors, which each have 100 fragile gold pins within them. The whole job took about two hours and 15 minutes.
"The brains of Hubble have been replaced," astronaut John Grunsfeld called out from inside Discoverys cockpit once the work was done.
"Great job to both Claude and Mike," astronaut Steven Robinson radioed up from NASAs Mission Control Center here.
Ground controllers at NASAs Goddard Space Flight Center in Greenbelt, Md., conducted a so-called "aliveness test" to make certain the new computer is working properly, which it is.
"The Hubble not only has new brains, its thinking," Robinson told the crew.
"Well, Im glad to hear that," said Smith. "Thank you, Houston."
"Thats terrific news," added Grunsfeld. "And I guess all 1,000 gold pins worked."
The new $7 million computer is not exactly state of the art. In fact, the new computer is based on an Intel 486 microchip now considered all but obsolete on Earth.
NASA officials, however, are quick to point out that it takes four years to develop a computer that will operate properly in a high-radiation environment. And while the new unit doesnt have the speed of a Pentium chip, the replacement still will be 20 times faster and have six times the memory of the old Hubble computer.
"Its not quite like going from a slide rule to a Macintosh or IBM but its close," NASA space science chief Ed Weiler said before the flight.
With the computer swap done, Foale and Nicollier moved on to another major chore: replacing one of Hubbles three Fine Guidance Sensors with a refurbished unit. Shaped like a baby grand piano, the $13 million sensors give Hubble the ability to remain locked on to an astronomical target for days at a time.
The resulting stability can be compared to holding a laser beam on a dime that is 200 miles away, or the distance between Washington, D.C. and New York City.
Leckrone put it another way: "Thats the equivalent of hitting a tee shot in Washington, D.C., and sinking a hole in one in Denver."
Foale and Nicollier had a bit of trouble with their second chore, though.
The spacewalking duo first removed an old guidance sensor so it could be stowed in the cargo bay for a return trip to Earth. But when it came time to install the refurbished unit, the 500-pound instrument hung up on guide rails within the observatory.
The astronauts, consequently, were unable to slide it into place on the first try. A vigorous wiggle was needed to free up the stuck sensor so it could be pulled part way out of the telescope and then, finally, reinserted into its proper place.
"Great work," Robinson told the spacewalkers. "Persistence pays."
The only other hitch that cropped up during the excursion came when a medical sensor glitch erroneously indicated that carbon dioxide levels had soared to dangerous levels within Nicolliers spacesuit.
Flight surgeons in Mission Control quickly determined the real nature of the problem. But the flight surgeons and Nicolliers crewmates nevertheless keep a close eye on the rookie spacewalker throughout the rest of the spacewalk.
"How are you feeling?" Smith asked his crewmate several times during the cargo bay foray.
"I feel fine. Really. Im working pretty hard, but I feel fine," Nicollier said. "Im thirsty and I have no more water, but thats okay."
The spacewalkers, in fact, offered to work a little overtime to do some Hubble wiring work scheduled for the missions third and final spacewalk Friday. Houston flight controllers, however, told the crew the spacewalkers already had worked long and hard enough.
"You just cant beat that kind of attitude. We appreciate it," Robinson told the crew. "Thanks for the offer but the consensus down here is that ought to be enough."
The spacewalking work followed an initial excursion conducted by Smith and Grunsfeld Wednesday. The duo fixed Hubbles failed pointing control system during an 8-hour, 15-minute excursion that turned out to be the second longest spacewalk in history.
A state-of-the-art science data recorder and a new radio transmitter will be installed on Hubble during the third spacewalk, which Smith and Grunsfeld will carry out beginning at 2:50 p.m. EST Friday.
If all goes well, Hubble will be released from the shuttle at 6:03 p.m. EST on December 25. The shuttle and its crew are due to land at NASAs Kennedy Space Center in Florida at 5:24 p.m. Monday.
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