In the final spacewalk of their 11-day mission, Astronauts Tanner and Stefanyshyn-Piper unpacked the station's new radiator and carried out a series of maintenance tasks.

"We have to say, what a wonderful job you both did today, " Pam Melroy in Mission Control told them.

The Atlantis shuttle is due to take its crew of six home from the ISS later today. It needs to be clear of the platform to allow a Russian Soyuz craft, carrying a new ISS crew and the first female space tourist, to dock next week.

Atlantis' mission to the station is only the third shuttle flight since the orbiter Columbia broke up on re-entry after being damaged by launch debris in 2003. Nasa, plans at least 14 more construction missions to the space station over the next four years. It must complete assembly before the orbiter fleet is retired in 2010.