CAPE CANAVERAL, Fla., Jan. 26 -- Leaving the international space station unattended while they stepped outside, its two crewmen hooked up a robotic arm Wednesday and found a substance on the spacecraft's vents that might explain the frequent breakdowns in its air-supply equipment.
Spacewalkers Leroy Chiao of the United States and Salizhan Sharipov of Russia did not make all the electrical connections on the experimental mini-arm tight enough. They had to redo part of the job but got full power flowing with minutes remaining in their 5 1/2-hour outing.
"Everything's perfect," Mission Control radioed.
"Well, thank God, thank God," came the reply. Before going back inside, they were advised: "Take a breather."
During their 225-mile-high excursion, the spacewalkers also inspected the station's vents and found a large patch of dark, oily residue and a white, honeycombed substance. It was not immediately known what the substances were.
The space station's Russian oxygen generator has broken down repeatedly, and engineers speculate that its vent might be clogged or corroded. The air-cleansing equipment has a history of malfunctions.
It was the first spacewalk in this mission for Chiao and Sharipov. They are 3 1/2 months into a six-month stay.
"Hello, space, my old friend," Chiao, a veteran spacewalker, said as he exited.
Because of the grounding of NASA's shuttle fleet, the space station has been limited to two residents instead of three. As a result, no one was left inside during the spacewalk, but ground controllers kept watch over the spacecraft, an increasingly common practice since the Columbia disaster two years ago.
The German-made, $10 million arm is a smaller, simpler version of what engineers hope will lead to satellite-repair robots in a few years.