Two spacewalking astronauts have left the International Space Station to retrieve a critical inspection boom needed to check the shuttle Discovery for damage. They are preparing to install Japan's new research lab Kibo on the orbital outpost.
Veteran spacewalker Michael Fossum and his rookie partner Ronald Garan floated into open space as the station sailed about 340 kilometers over southeast Asia.
The spacewalkers were about an hour late getting started due to a problem with communication equipment.
Fossum and Garan's major task is to remove protective covers from the boom's laser and camera and disconnect cables so it can be returned to the shuttle for an inspection later in the mission.
The astronauts are also scheduled to inspect a damaged metal ring needed to move the station's solar wing panels to track the sun for power. They will use a tool similar to a dentist's pick to try to scrape away debris and see if they can clean the ring. If the technique works, NASA intends to have its next service crew attempt a full cleanup.
Later on Tuesday, astronauts Akihiko Hoshide and Karen Nyberg, working from inside the station, will use the station's robot arm to pluck the Kibo lab from the shuttle's cargo bay and attach it to the Harmony module.
Discovery is scheduled to spend 2 weeks in orbit.
The main goal of Discovery's mission is to deliver Japan's one billion US dollar Kibo laboratory.