Spacewalkers dispatched to prepare Japanese lab

HOUSTON (Reuters) - A pair of spacewalking astronauts leftthe International Space Station on Tuesday to retrieve acritical inspection boom needed to check shuttle Discovery fordamage and to prepare Japan's new research lab for installationon the orbital outpost.

After camping out in the station's airlock overnight toprepare their bodies for the outing, veteran spacewalkerMichael Fossum and his rookie partner Ronald Garan floated intoopen space at about 11:30 a.m. CDT (5:30 p.m. British time) asthe station sailed 210 miles over southeast Asia.

The spacewalkers were about an hour late getting starteddue to a problem with communications equipment.

"All right boys, it's time to rock and roll," saidDiscovery astronaut Ken Ham as Fossum and Garan were finallyready to begin the planned 6.5-hour spacewalk.

The primary goal of Discovery's mission, which began onSaturday with liftoff from the Kennedy Space Centre in Florida,is to deliver Japan's $1 billion (509 million pound) Kibolaboratory, the cornerstone of that country's 20-year effort tojoin in as a permanent player in human space exploration andresearch.

"It's going to be a really big day for Japan," said spacestation flight director Emily Nelson.

At 37 feet long and just over 14 feet wide, Kibo, whichmeans "hope", is so big that Discovery didn't have room in itscargo bay for its inspection boom, a piece of equipment thatdoubles the length of the shuttle's 50-foot robot arm so thatcameras and sensors can inspect the ship's wings and nosecapfor damage.

The boom was part of NASA's safety upgrades following thefatal 2003 Columbia accident, which was triggered by damagefrom a debris impact.

The last shuttle crew to visit the space station left itsboom behind, temporarily stashed alongside a segment of thestation's external framework, for the Discovery astronauts touse and return to Earth.

Fossum and Garan plan to remove protective covers from theboom's laser and camera and disconnect cables so it can bereturned to the shuttle for an inspection later in the mission.Discovery is scheduled to spend 14 days in orbit.

LAB TO BE ATTACHED

Later in the day, astronauts Akihiko Hoshide and KarenNyberg, working from inside the station, will use the station'srobot arm to pluck the 16-ton Kibo lab from the shuttle's cargobay and attach it to the Harmony module, which serves as aconnecting node for several station components.

Fossum and Garan also were scheduled to inspect a damagedmetal ring needed to pivot a pair of the station's solar wingpanels to track the sun for power.

Engineers last year discovered the rotary joint was usingmore power than expected and sent a pair of astronauts outsideto investigate. They found widespread contamination of the mainmetal ring, which should be completely smooth.

Fossum and Garan will use a tool similar to a dentist'spick to try to scrape the debris away and then wipe the areawith a light lubricant to see if they can clean the ring up abit. If the technique works, NASA intends to have its nextshuttle servicing crew attempt a full cleanup.

The solar wing has been mostly parked since the damage wasdiscovered but by next year, when the station nears completion,NASA will need the rotary joint working to fully power theoutpost.

The U.S. space agency has seven space station constructionmissions remaining and two resupply flights. Upon completion in2010, the shuttle fleet, which has been flying since 1981, willbe retired.

(Editing by Jim Loney)