Astronauts from the U.S. space shuttle have set out on thefirst spacewalk of their mission at the International Space Station.
Veteranspacewalker Dave Wolf and newcomer Tim Kopra floated out of the hatchSaturday to help the crew install an external platform on the massiveJapanese lab at the station.
The six-and-a-half hour operationwill require a hands-on effort by the spacewalkers, in addition tousing the shuttle's and station's robotic arms.
The platform will complete the lab and allow scientists to conduct experiments in the vacuum of space.
In order to cut down preparation time, Wolf and Kopra "camped out" in the space station's airlock entrance Friday night.
Theirs is the first of five planned spacewalks during 11-day mission.
The shuttle docked with the Space Station earlier Friday, after a two-day trip from Earth.
With the shuttle crew, the station's population grew to 13, the highest number in the outpost's history.
Kopra is taking the place of Japan's Koichi Wakata, who has been on the space station since March.
OnThursday, the U.S. space agency said foam insulation that broke off external fuel tank shortly after liftoff is no cause forconcern.
NASA's shuttle program manager, John Shannon, said theloss of the foam insulation did not hurt the because itoccurred "so late" after takeoff.
The debris could be seenhitting the spacecraft about two minutes after Wednesday's liftoff fromthe Kennedy Space Center in the southeastern state of Florida.
NASAhas been concerned about debris from the external fuel tanks since theshuttle disaster in 2003. Foam insulation damaged theshuttle's heat tiles during launch, which led to breakingapart upon re-entry. All seven astronauts aboard the flight werekilled.