Washington, July 27 (DPA) US astronauts Tom Marshburn and Chris Cassidy installed video cameras Monday on the International Space Station's new Japanese porch.

The work was the main task of a planned six-and-a-half-hour spacewalk that began about an hour ahead of schedule at 11:33 GMT.

The two cameras will help astronauts and ground crews to dock an unmanned Japanese cargo craft to the station. It is to make its first delivery of supplies in September.

The astronauts also fixed insulation on a robotic arm and did electrical work.

It was the fifth and final spacewalk of the space shuttle Endeavour's mission at the ISS. During the mission, an external porch was installed on Japan's Kibo laboratory and will be used to expose experiments to the extremities of space.