The crew of the space shuttle has successfully completed its mission to help extend the orbiting platform.

Two Endeavour spacewalkers fixed a new 13.5-metre-long (45 feet) hi-tech beam to the station's growing structure.

The truss, or girder, contains part of the cooling system for the ISS.

Third walk

Returning on Endeavour is Expedition Five - Valery Korzun, Peggy Whitson and Sergei Treschev. The resident crew has been living aboard the platform for six months.

Staying behind is Expedition Six - Ken Bowersox, Nikolai Budarin and Don Pettit. The relief crew went up on the orbiter and will now live and work in space until at least March next year.

Astronaut John Herrington was the hero of the day on Saturday when he came up against a tough problem in the third and final spacewalk of the mission.

He managed to free a two-tonne, $190m trolley car that had become stuck on the tracks that run along the top of the truss.

Pushed higher

Herrington's and Michael Lopez-Alegria's three walks outside the ISS to fit and plumb the new segment lasted 20 hours in total.

One of the last tasks for Endeavour before undocking has been to raise the altitude of the space station.

The shuttle commander Jim Wetherbee made a series of firings of the orbiter's thrusters to take the platform about 4.5 kilometres (2.8 miles) further away from the Earth.

The ISS is now almost 10.5 km (6.5 miles) higher than it was when the shuttle docked on 25 November. Its average altitude is 397 km (247 miles).

Endeavour's landing is scheduled for Wednesday at the Kennedy Space Center in Florida, US.