This story was updated at 9:10 p.m. EDT.
HOUSTON ? Two spacewalking astronauts help deliver a majornew addition, the giant Japanese Kibo laboratory, to the International SpaceStation (ISS) Tuesday in the first of three excursions planned for theirmission.
Spacewalkers MikeFossum and Ron Garan also tested methods of cleaning the orbital lab'ssticky solar wing joint and retrieved their shuttle's inspection boom duringtheir nearly seven-hour venture outside the station.
The astronauts officially began their spacewalk about anhour late at 12:22 p.m. EDT (1622 GMT) because of a communications glitch inFossum's spacesuit, which was emitting a loud squeal. The crew was able toreconnect a cable and fix the problem.
The fix delayed the start of the spacewalk about 50 minutespast its planned beginning, but otherwise had no effect on the six-hour,48-minute excursion.
Fossum and Garan arrivedat the station Monday along with the other members of the space shuttleDiscovery's seven-person crew, led by commander Mark Kelly.
The wholecrew had a role in the spacewalk, with pilot Ken Ham choreographing theventure from inside the station, and mission specialists Karen Nyberg, AkihikoHoshide and Greg Chamitoff driving the shuttle and space station robotic arms.
While the spacewalkers were trampling around the outside ofthe station, Ham called out, "Watch your feet on my roof!"
The spacewalk began on the 43rd anniversary of thefirst-ever U.S. spacewalk, a 23-minute excursion by astronaut Ed White duringthe Gemini 4 mission on June 3, 1965.
The spacewalkers began their trip outside by retrievingDiscovery's sensor-tipped heat shield inspection pole from the ISS.
"Alright, boys, it's time to rock and roll," Hamcalled out at the start of the spacewalk.
Usually, shuttles carry their own inspection poles, whichattach to the shuttle's robotic arm and are used to scan heat tiles for signsof damage. In this case, however, Discovery couldn't fit the 50-foot (15-meter)boom in its payload bay, which was crowded by Kibo, so the previous shuttlemission, Endeavour's STS-123 flight last March, left the boom outside thestation for Discovery.
After viewing photographs taken of the shuttle?s belly rightbefore it docked at the space station, mission managers said they have clearedthe shuttle for landing in the case of an emergency. They have also determinedthat no further focused inspection will required, Mission management chairLeRoy Cain said today after the spacewalk.
Once the two spacewalkers released the restraints holdingthe pole in place on the space station's truss, the inspection tool was pickedup by the space station's robotic arm, steered by Hoshide, and passed off tothe shuttle arm, driven by Nyberg. Then Nyberg safely stowed the boom away,where it will stay until Friday when it is due to be used to perform a detailedinspection of Discovery's heat shield.
After recovering their shuttle's inspection pole, the twospacewalkers set to work preparingthe new Kibo module to be installed on the station. It was secured in tightin Discovery's payload bay, so the bolts and straps that held it in had to beremoved before it could be unberthed.
Once the spacewalkers had freed up the Japanese lab,Japanese astronaut Hoshide picked it up with the station's robotic arm andcarried it "carefully, methodically and glacially" over to its new,permanent perch on the ISS's Harmony node, said NASA commentator Rob Navias.
At about 6:15 p.m. EDT (2215 GMT) 'Hope' finally reachedHarmony, and about half an hour later the two modules attached.
"You are go for first stage capture," astronautGarrett Reisman told Hoshide, instructing him to move forward with the firststeps of installing the new module.
"Sweet!" Hoshide replied.
By 7:01 p.m. EDT (2301 GMT), the lab was finally secured onits permanent roost.
Clogged joint cleaning
While the station arm was moving Kibo across the sky, thetwo spacewalkers moved on to their planned inspection of a troublesomejoint on one of the space station's solar panel wings.
The joint, called the Solar Alpha Array Rotary Joint (SARJ),is a huge gear that serves to rotate the station's outboard solar wings like apaddlewheel to keep them facing the sun to draw in as much pressure. The starboardjoint has been clogged by metallic grit lodged inside it, which has damaged itsrotating ring and caused odd power spikes and vibrations that were firstdetected last October.
Fossum tested cleaning techniques, including scraping thearea with a dentist's pick-like tool and using a grease gun to lubricate thegear and dislodge debris.
"The initial scraping probably did the most good,"Fossum said.
He also helped determine that one area of interest, anapparent divot in the gear's metal ring, was actually etched into the surfacerather than raised above it.
"That mark was actually an indentation," said KirkShireman, NASA's deputy station project manager, after the spacewalk. "Sothat was good data for us."
If NASA decides the cleanaing techniques are successful,they plan to send a later mission to use them on a spacewalk to perform a morethorough cleaning.
Meanwhile, Garan worked to reinstall a previously-removedset of bearings that the gear rings roll on.
With one spacewalk in the books, Discovery's STS-124 crewand the station's Expedition 17 astronauts are now looking ahead to officiallyopening the new Kibo laboratory on Wednesday. They are also set to fix thestation's balky space toilet, a Russian-built commode that has been acting uplately.
- New Video: Liftoff! Discovery Launches Into Space
- Video: STS-124 Mission Preview ? Delivering Kibo
- Complete Space Shuttle Mission Coverage
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Clara Moskowitz is a science and space writer who joined the Space.com team in 2008 and served as Assistant Managing Editor from 2011 to 2013. Clara has a bachelor's degree in astronomy and physics from Wesleyan University, and a graduate certificate in science writing from the University of California, Santa Cruz. She covers everything from astronomy to human spaceflight and once aced a NASTAR suborbital spaceflight training program for space missions. Clara is currently Associate Editor of Scientific American. To see her latest project is, follow Clara on Twitter.