The two crewmembers aboard the International Space Station successfully completed an extended 6-hour spacewalk early Friday to fix equipment and retrieve science experiments from the outside of the complex.

U.S. Science Officer Jeffrey Williams (L) in a televised view during his spacewalk with International Space Station Commander Pavel Vinogradov of Russia (obscured, R) from aboard the orbiting laboratory June 1, 2006. Vinogradov and Williams, wearing Russian Orlon spacesuits, will repair a vent on the station's oxygen-producing Elektron unit, retrieve experiment results and replace a camera on the station's rail car system during their scheduled 5-hour 41-minute spacewalk. [Reuters]

The spacewalk was marred only by the loss of a 12-inch metal foot restraint adapter that had been on the Russian telescoping work boom.

"We have a problem," a translator reported station commander Pavel Vinogradov saying to the Russian flight control team. "We have the foot restraint gone. It was in the closed position. We don't understand it. That's bad."

Vinogradov and crewmate Jeffrey Williams had finished their work on the Russian parts of the station and did not need the device for the remaining task, said NASA spokesman Rob Navias.

Earlier in the outing, the spacewalkers installed a new vent port for the station's oxygen generator, which makes breathable air by separating oxygen molecules from water. The water's hydrogen is dumped overboard.

The Russian-made device has had to share a vent port since its original one was contaminated. An electrical problem however was complicating its operation since sharing the vent required the device to be turned off for days at a time.

Vinogradov and Williams then inspected and photographed two navigational antennas, which will be needed next year when Europe's unmanned cargo ship makes it debut flight to the station. One had a cable lying across it that was interfering with its radio signal. The other is suspected of blocking movement of a sun shield.

The men also retrieved a contamination monitoring device and a science experiment, both of which will be sent back to Earth for analysis.

Running behind schedule, NASA and Russian flight controllers discussed dropping the final task of the spacewalk, but decided to extend the outing an hour so that a broken camera on the U.S. mobile transporter could be replaced. The camera helps station and shuttle crews position equipment and modules during construction.

NASA hopes to resume assembly of the half-built outpost later this year. Work has been on hold since the 2003 Columbia accident, when the shuttle fleet was grounded for safety upgrades.

The second and final post-Columbia test-flight is currently scheduled for launch in July. If the redesigned shuttle fuel tank works as expected and no large pieces of foam fall off during launch, NASA may resume station assembly during the shuttle's next mission, which could launch as early as Aug. 28.