Spacewalkers work on station before shuttle visit

CAPE CANAVERAL, Florida (Reuters) - A pair of spacewalking astronauts slipped outside the International Space Station on Tuesday to finish some maintenance chores before the shuttle Discovery's scheduled arrival on Friday.

Dressed in Russian spacesuits, station commander Michael Fincke and flight engineer Yury Lonchakov floated outside the orbiting outpost for six hours of work, including setting up a European materials science experiment.

Meanwhile, at the Kennedy Space Center in Florida, work to prepare Discovery for a 9:20 p.m. EDT Wednesday (0120 GMT Thursday) blastoff was proceeding smoothly.

"At this point, we have no real concerns," said Steve Payne, a manager overseeing Discovery's launch preparations. "We are ready for the exciting mission that lies ahead."

Discovery will deliver the last segment of the space station's exterior support structure. The $300-million, 16-tonne piece includes the station's final U.S.-built power module.

Connecting the beam will be the focus of the first of four spacewalks planned by the shuttle crew. If Discovery is launched as planned on Wednesday, it will arrive at the station on Friday.

Fincke, on his sixth spacewalk, and Lonchakov, on his second, hustled through a list of chores that included cutting six flapping straps near the docking port used by Russian spaceships.

The primary purpose of the spacewalk was to install and activate a European Space Agency experiment that exposes plant seeds, spores, microbes and bacteria to the harsh radioactive environment of space.

Fincke and Lonchakov attached the suitcase-sized experiment to a bracket outside the station's Zvezda command module, where it will remain for about 14 months.

The spacewalkers also took hundreds of pictures of antennas, handrails, radiator vents and other equipment on and around Zvezda that will be assessed by engineers to see how they have held up during nine years in orbit.

Speaking in Russian to flight controllers, the men were struck by the view as the outpost sailed 220 miles over Egypt.

"There are no words in any language to describe what we are seeing now," one said through an interpreter.

The station, a $100 billion project of 16 nations, is nearing completion after more than a decade of construction. NASA has up to nine assembly missions remaining, as well as a final flight to service the Hubble Space Telescope before the shuttle fleet is retired in 2010.

(Editing by Jim Loney)