Astronauts aboard the American space shuttle Endeavour have begun the process of linking together the first two components of the International Space Station: the Russian module Zarya, already in orbit, and the American module,Unity, which they've carried into space.

The crew have gripped Zarya with the shuttle's 17-metre robot arm to manoeuvre it into position to connect it to Unity, still in Endeavour's cargo bay.

The attitude of the craft means the astronauts can't see the Russian module -- and so for the first time, a docking manoeuvre is being carried out using a computerised vision system.

The final connections between the two modules will be made during a space walk on Monday.

Unity will link together science, service, and living modules.

It also has a docking port for the space shuttle.