Washington  - Two Discovery space shuttle astronauts began their third spacewalk Monday to complete maintenance work on the International Space Station.

During the planned six-and-a-half hour spacewalk, astronauts Joseph Acaba and Richard Arnold were to reposition an equipment cart, complete the deployment of an external cargo mounting mechanism, lubricate the space station's robotic arm and reconfigure some cables that power the station's gyroscopes.

This is the second spacewalk for both Acaba and Arnold and the final one of the current mission.

On Friday, the Discovery crew completed installation of the station's final pair of solar panels, which will expand the satellite's power supply.

Discovery docked last Tuesday with the ISS, bringing the fourth and final solar panel.

The mission also delivered astronaut Koichi Wakata, who has officially joined the permanent crew on the orbiting space station as its first Japanese member. He replaces US astronaut Sandra Magnus, who will join the Discovery crew for the flight back to Earth.

The shuttle launched March 15 after weeks of delays to inspect and study the hydrogen fuel valves and a later leak in a fuel vent.

Discovery is scheduled to end its 13-day mission on Saturday. dpa