The two International Space Station crewmen floated outside the complex Monday to perform some maintenance chores and help prepare it for the resumption of assembly when the space shuttle returns to flight. The spacewalk lasted five and a half hours.

It was the first spacewalk for Russian flight engineer Valery Tokarev, but the third for U.S. station commander Bill McArthur, whose enthusiasm for the view from orbit apparently has not waned with experience.

"Oh, that's beautiful," he said. "Aw, that's gorgeous!"

Mr. McArthur made the comment as he opened the hatch door to the U.S. module, an event that occurred one hour later than planned because of difficulties reducing the pressure in the airlock.

Despite the time setback, the two crewmen worked quickly to install a camera and lights that will be used to guide future station construction when shuttles return to flight, planned for next year. U.S. mission control in Houston advised them that their speed put them back on schedule.

Other tasks the spacewalking pair finished included the removal of an experiment that measured the electrical environment around the outside of the station and removal of a failed electronics box that controlled a motor rotating a heat-dissipating radiator.

Under normal circumstances, there is a third crewmember inside to help the spacewalkers in and out of their bulky spacesuits and oversee their outside activities. But the station has been without a third person aboard since the moratorium on shuttle flights after the Columbia disaster in 2003. This is because Russian cargo craft are not large enough to carry enough supplies for a trio.

So U.S. flight controllers in Houston, Texas ran the station during the spacewalk, or, as mission directors call it, an EVA for extra-vehicular activity.

"This is not the first EVA that we've been a part of without anyone inside," said lead flight controller Sally Davis. "We've actually done several of them out of the Russian segment. It is the first time we've done a U.S. EVA without anyone inside."

It was also the first outing in two-and-a-half years overseen by U.S. mission control and conducted in American space suits from the U.S. module. Recent spacewalkers wore Russian apparel and departed from the Russian module guided by flight directors near Moscow because the U.S. airlock's cooling system had corroded, causing debris to contaminate the portal and the suits. An earlier station crew repaired the cooling system and new U.S. outfits arrived with the August shuttle mission.