ISS Expedition 8 commander Mike Foale and flight engineer Alexander Kaleri spent three hours and 55 minutes Thursday retrieving and replacing science instruments on the station's Pirs docking compartment and Zvezda module. The spacewalk was cut short after it became clear that the cooling system in Kaleri's spacesuit was not working properly.

Aside from that hitch, the extravehicular activity (EVA) went well for NASA flight controllers, who touted the spacewalk as a success for the autonomous ability of the ISS. It was the first time the station was left empty during a spacewalk.

"This was a huge success," said Mike Suffredini, NASA's ISS manager for integration and operations, during a Friday press briefing. "I feel really good about how little, over all, we had to deviate from our plan."

The successful autonomous functions of the ISS during the Expedition 8 spacewalk encouraging for NASA officials planning similar two-person outings for the upcoming Expedition 9 to launch in April. The crew of that expedition, cosmonaut Gennady Padalka and astronaut Michael Fincke are scheduled to make two spacewalks, including a crucial one that will prepare the ISS to accept supply shipments from the European Autonomous Transfer Vehicle (ATV).

Foale and Kaleri started their spacewalk, the only one scheduled for the Expedition 8 crew, at about 4:17 p.m. (EST). The EVA was expected to run about five hours 45 minutes, but about midway through Kaleri reported seeing drops of water on the inside visor of his space suit. Russian flight controllers ordered the spacewalkers to return to ISS after initial attempts to restart Kaleri's suit cooling system failed.

Foale and Kaleri were able to board the ISS about 45 minutes after the problem was reported, 15 minutes faster than flight controllers had planned in the event of an emergency, NASA officials said.

A kink in a tube that circulated water throughout Kaleri's cooling garment was the apparent source of the malfunction, but Russian flight controllers have not determine exactly how it happened.

Suffredini said that while Kaleri was never in any danger, Orlan spacesuits are specifically designed not to kink. It is possibly, though, that the problem occurred while Kaleri first donned the suit inside the ISS, he added.

Michael Hembree, ISS lead EVA officer, said Russian flight controllers reported that Kaleri's spacesuit temperature was slightly higher than expected throughout the entire EVA. Russian officials repeatedly asked the cosmonaut how he was feeling along the way, Hembree added. While Kaleri felt warm he never complained of being uncomfortable during the spacewalk.

Thursday's EVA was the last use of the particular Orlan spacesuits worn by Foale and Kaleri. The space station does carry two brand new spacesuits for the Expedition 8 crew, should there be any need for an unscheduled spacewalk.

"If we had to do a contingency EVA, given the long history of success with these suits and the fact there are two new ones, I wouldn't have any concern about that," Suffredini said.