Station commander Gennady Padalka and flight engineer Yuri Malenchenko opened the hatch on the station's airlock at 11:37 a.m. EDT to begin a spacewalk to relocate a construction crane, install debris shields and release a small satellite into orbit.

Their departure was delayed about an hour while engineers assessed a leak between the Pirs docking module and Russian segments of the station, a $100 billion laboratory for microgravity experiments and technology testing that flies about 250 miles above Earth.

But the issue was resolved and the experienced spacewalkers more than made up the lost time.

Padalka, who was making his ninth spacewalk, and Malenchenko, on his fifth, moved a hand-operated, 46-foot (14-meter) crane, called Strela-2, from the outside of Pirs to Zarya, the cornerstone of the station. Pirs is due to be detached from the station next year to make room for a new Russian laboratory and docking module.

The United States completed construction of its part of the outpost last year and retired its three space shuttles. Europe, Japan and Canada also are partners on the project.

With the crane in place, the spacewalkers then used a hand tool to launch a 20-pound (nine-kg) spherical satellite on a path behind the space station.

"Nice throw," a flight director in the Russian mission control center outside Moscow said through a translator monitoring radio communications with the cosmonauts.

The satellite, which is expected to remain in orbit for about three months, is intended to serve as a target for Russian engineers working on computer models that evaluate orbital tracking.

The spacewalkers' last major task was to install five debris shields to the outside of the Zvezda module, the crew's primary living quarters. They also retrieved a briefcase-sized experiment that has been exposing various materials to the harsh environment of space and installed two support struts on a ladder.

Padalka and Malenchenko returned through an airlock and shut the hatch at 5:28 p.m. EDT, completing the 163rd spacewalk for station assembly and maintenance.

On August 30, NASA astronaut Sunita Williams and Japanese astronaut Akihiko Hoshide, both station flight engineers, are scheduled to make another spacewalk to replace a power relay unit on the station's truss, set up power cables for the Russian laboratory module scheduled to launch next year and install a thermal cover on a docking port.

(Editing by Tom Brown, Eric Beech and Philip Barbara)

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