Two crew members on the International Space Station will spend their Christmas Eve taking a stroll through the vacuum as they finish up repairs to a faulty pump that threatened the station's cooling systems. A "degraded ammonia pump module" was removed from the station's exterior during a five-hour-plus spacewalk on Saturday, and a replacement pump will be installed in the empty slot on Tuesday. (The pump just happens to weigh 780 pounds and is about the size of a double-door refrigerator, so it might take awhile.)

If all goes well, the entire repair job will be completed in just two spacewalks, and not the three that NASA originally anticipated.

That's good news, considering the problems the walkers have had with their pressure suits during the last two spacewalks. Saturday's walk was actually cut short after Flight Engineer Rick Mastracchio had trouble regulating the temperature in his space suit. Then during re-pressurization, his suit began to fill with water, causing Mastracchio to go with a backup suit for today's walk. Back in July, Italian astronaut Luca Parmitano of the European Space Agency nearly drowned when his helmet began to fill with water during a space walk, although the two water issues were unrelated.

NASA fully admits that problem might have something to do with the fact that suits in question are nearly 35 years old, and were designed for the original space shuttle missions.

You can watch the NASA livestream of the mission below and follow along on their Twitter feed, too. The actual spacewalking part is scheduled to begin around 7:00 a.m. ET.

Live streaming video by Ustream

This is actually the second time astronauts have conducted a spacewalk on Christmas Eve. Another repair job was carried out on the Hubble Telescope 14 years ago today.