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A team of astronauts working inside and out anchored a giant billion-dollar Japanese lab to the international space station Tuesday, making it the biggest room there.

The long-awaited moment of contact came as two of the crew were winding up a spacewalk.

Spacewalkers Michael Fossum and Ronald Garan Jr. took care of all the preliminaries, removing covers and disconnecting cables on the bus-size lab, named Kibo, Japanese for hope.

They left it to their colleagues inside to do the heavy lifting, by way of the space station's robot arm.

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The honor of operating the arm for the installation fell to Japanese astronaut Akihiko Hoshide, who accompanied Kibo to orbit aboard space shuttle Discovery.

"We have a new hope on the International Space Station," announced Hoshide.

"Fantastic job," Mission Control replied.

Kibo — a behemoth stretching 37 feet and weighing more than 32,000 pounds — became the largest lab at the space station by nine feet.

It's also more sophisticated. Kibo sports a hatch to the outside and a robot arm for sliding out science experiments. A smaller arm will arrive next spring, along with an outdoor porch for holding the experiment packages.

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The first part of Kibo — essentially a storage shed — was delivered by the last shuttle crew in March. The astronauts aboard the linked shuttle and station will attach the shed to the lab on Friday.

Japanese Space Agency officials estimate more than $2 billion went into all the pieces, which had to be split up to fit into three shuttle missions. The project has been in the works for more than 20 years.

The astronauts will enter Kibo on Wednesday.

The space station's two Russian residents, meanwhile, will spend the morning working on the space station's toilet; the shuttle crew hand-delivered a new pump for the malfunctioning commode.

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The lab work was just part of Tuesday's spacewalk, the first of three planned for Discovery's nine-day space station visit.

Coincidentally, it fell on the 43rd anniversary of America's first spacewalk, by Gemini 4's Edward White.

White spent 21 minutes outside his capsule on June 3, 1965. Fossum and Garan's spacewalk lasted nearly seven hours.

The spacewalkers got off to a late start because of a bad cable in Fossum's communications cap, but soon made up for lost time, helping to remove a 50-foot shuttle inspection boom from the space station.

The laser-tipped pole was left there by the last shuttle crew, for use by Discovery's astronauts to survey the shuttle's thermal skin before returning to Earth.

Kibo took up so much of Discovery's payload bay that there wasn't room for the boom.

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Fossum also took a stab at cleaning a solar wing rotating joint that is clogged with metal shavings, while Garan worked to put in a new bearing. The joint has been used only sparingly since last fall, hampering energy production.

NASA still does not know where the grit came from or how best to deal with the problem. Fossum confirmed that there is a pit in the gears of the joint; engineers expect the damage will spread.

It was the fourth spacewalk for Fossum, a colonel in the Air Force Reserves who is making his second shuttle flight, and the first for Garan, an Air Force pilot.

As the spacewalk got under way, Fossum offered this advice: "Enjoy the view, but don't look down."

As for Discovery, the photos taken by the space station residents just before Monday's linkup uncovered just four small areas of tile damage on the shuttle's belly.

The damage is so slight that no detailed inspection will be required, said LeRoy Cain, chairman of the mission management team.

NASA, meanwhile, is investigating the worst launch pad damage in 27 years of space shuttle flight.

A large section of the flame trench — 20 feet by 75 feet — broke apart, and chunks of the large heat-resistant fire bricks and concrete mortar were scattered all the way past the chain-link fence 1,800 feet away. The fence was damaged in places.

None of the debris appeared to hit Discovery, said LeRoy Cain, chairman of the mission management team.

The flame trench — dating back to the 1960s Apollo era and designed to deflect the exhaust of the booster rockets — is inspected regularly and undergoes periodic repair, Cain said.

NASA does not need to use the pad again until the next shuttle launch in October. That mission — the final trip to the Hubble Space Telescope — should not be delayed as a result of the damage, Cain said.