Two astronauts have carried out the first spacewalk of Space Shuttle Discovery?s 12-day mission to the International Space Station (ISS).

The pair installed a truss that forms the backbone of the station during their walk of more than six hours. Earlier, the crew used a camera on the ISS?s robotic arm to examine an area on the shuttle?s left wing where sensors detected a ?very low? impact. Nasa officials said they did not expect the incident to affect the mission. The shuttle docked with the ISS at 2206 GMT on Monday, ahead of a week-long stay to carry out a range of tasks in what Nasa has described as one of the most complex missions to date.

Engineers will examine data gathered during the inspection of the shuttle?s wing before deciding whether any further inspections are necessary.