Vital spacewalk completed

The spacewalkers had to avoid numerous obstacles on the outside of the ISS

By BBC News Online science editor Dr David Whitehouse

An American astronaut and a Russian cosmonaut have carried out a vital spacewalk that will allow a future crew to spend months on the International Space Station (ISS).

Malenchenko's second spacewalk

Atlantis docked with the ISS early on Sunday to enable its seven-member crew to deliver supplies and undertake vital maintenance work. The space shuttle blasted off on Friday on an 11-day mission.

Edward Lu and Yuri Malenchenko made a gruelling climb along the outside of the 42-metre (140 ft) exterior of the space station. Mission controllers said it was like working on the 11th story of a 13-story building - with the Earth 368 km (230 miles) below.

This truly is an astronaut's dream mission

Atlantis Commander Terry Wilcutt

Tethered to the space shuttle for safety they travelled further away from the shuttle than any other tethered astronauts performing a spacewalk.

They also had mini jetpacks for added safety. Only Malenchenko has made a spacewalk before.

Space compass

For the first time, Nasa adopted the Russian method of space walking, using a pair of tethers as rock climbers do - one line remains attached while they move to a new position and secure the other.

The International Space Station in orbit

The two spacewalkers had to scale Zvezda in order to erect a boom for a compass. By measuring the Earth's magnetic field, the compass, called a magnetometer, allows the space station to know which way it is pointed.

Most of the astronauts' time was spent connecting cables that will allow Zvezda to receive power from US solar-power panels once they are assembled on future missions.

The crew of Atlantis will spend a week transferring supplies to the Zvezda service module, the cornerstone of Russia's contribution to the ISS, which will serve as the early living quarters for the station.

The team is carrying supplies which include life-support equipment, computer hardware, and the ISS's first toilet.

The shuttle crew have been unable to get an air sample from inside the ISS but Nasa said it would not prevent them entering the complex on Tuesday to deliver supplies for the first residents, due in November.

Another suprise was a jammed solar panel on Zvezda, a Russian-built module, that did not deploy properly following its launch.

Nasa says there is roughly 250 cubic metres (8,800 cubic feet) of living space at the moment, about the same as comfortable apartment.