Endeavour astronauts on spacewalk

US astronaut Tim Kopra was making his first ever spacewalk

Astronauts have begun the first of five spacewalks to be performed by the crew of the shuttle Endeavour at the International Space Station (ISS).

American astronauts Tim Kopra and Dave Wolf are preparing Japan's space lab Kibo for the installation of its final piece - a large external platform.

It will be used in experiments requiring materials to be exposed to the harsh environment of space.

Endeavour docked on Friday, uniting a record 13 astronauts at the ISS.

Saturday's spacewalk was expected to last more than six hours.

The 1.9-tonne platform will be attached to Kibo's two pressurised modules that were delivered to the space station last year.

Once the pieces are ready, the astronauts will manoeuvre the robotic arms on the station and put the section into place with the help of the two spacewalkers.