* First spacewalk by an Italian astronaut
* Astronauts install power cable for new Russian lab (Updates with spacewalk completion)
By Irene Klotz
CAPE CANAVERAL, Fla., July 9 (Reuters) - Two astronauts left the International Space Station on Tuesday for a day of maintenance tasks, including installing a power cable needed for a new Russian laboratory due to be installed this year.
Veteran NASA astronaut Christopher Cassidy and rookie partner Luca Parmitano, the first Italian to make a spacewalk, left the station's Quest airlock shortly after 8 a.m. EDT (1200 GMT) as the orbital outpost sailed about 260 miles (418 km) over the Arabian Sea.
"Have fun out there," crewmate Karen Nyberg radioed from inside the station, a $100 billion research complex owned by the United States, Russia, Japan and 11 European nations, including Italy.
Cassidy's first task was to replace a failed backup component of the station's Ku-band communications system.
Parmitano, meanwhile, maneuvered himself to the right side of the station's solar power truss to pick up a pair of science experiments that will be returned to Earth aboard a future Space Exploration Technologies' cargo ship.
The privately owned California-based company, also known as SpaceX, is one of two U.S. firms hired by NASA to fly cargo to the station since the retirement of the space shuttles in 2011.
SpaceX's Dragon cargo capsules, which also are being developed to fly astronauts, are the only ones that return to Earth. Other cargo ships, including those flown by Russia, Europe and Japan, incinerate in the atmosphere after they leave the station.
Cassidy, who was making his fifth spacewalk, installed a power and data cable from the station's Unity connecting node to the Russian part of the International Space Station, completing one of the main goals of the outing.
The cable is part of a system that will be needed for a new Russian multi-purpose laboratory called Nauka that is due to launch later this year.
The new module will replace Russia's Pirs airlock, as well as serve as a research laboratory and berthing port. Russian cosmonauts will install the rest of the cable on a future spacewalk.
Before heading back inside the station's airlock around 2 p.m. EDT/1800 GMT, Cassidy and Parmitano retrieved a failed camera, put a cover on the shuttle's no-longer-needed docking port and began reconfiguring cables that could be used to control the station's electrical system in case of a partial power outage.
They also repositioned some equipment delivered aboard a Dragon capsule in March. The gear - two grapple bars - may be needed by future spacewalkers removing station radiator panels.
The astronauts plan to resume work on the jumper cables during a follow-up spacewalk on July 16. (Editing by Kevin Gray and Doina Chiacu)
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