Two astronauts have started the first of three planned spacewalks to fix a problem with the International Space Station's cooling system, according to Space.com.
Astronauts Rick Mastracchio and Michael Hopkins stepped outside the station today, Dec. 21, at 7:01 a.m. to replace an ammonia pump containing a bad valve.
The next spacewalk has been scheduled for Dec. 23, and another will take place on Christmas Day.
NASA TV is broadcasting the entire 6.5-hour extra-vehicular activity, also known as a spacewalk, according to Space.com.
"It's a beautiful day," Mastracchio said as he stepped outside of the orbiting outpost.
One of the station's ammonia cooling systems shut down on Dec. 11, causing astronauts to power down "unnecessary equipment." The crew was not in any danger as is doing fine, according to NASA.
The cooling systems shut down due to an apparent faulty valve inside a pump, located outside the station. Engineers on the ground attempted to avoid the spacewalks, but as of Dec. 16, the cooling system was still down.
Mastracchio, who is making his seventh spacewalk, and Hopkins, making his first, could be seen wearing extra safety gear as they floated outside.
"Beautiful day," Mastracchio said outside the space station.
The pump replacement is a huge task attempted only once before, back in 2010. The 780-pound pump is about the size of a double-door refrigerator and extremely difficult to handle, with plumbing full of toxic ammonia.
"Of course, the bad news is the station's having problems and we have to go out and do a repair," said Mastracchio, according to the Associated Press. "The good news is we have the spare parts. We have the training. We have the skills and, of course, going out and doing a spacewalk is always very exciting, yet very challenging."
NASA delayed a delivery mission from Wallops Island, V.A., because of the spacewalks. That flight by Orbital Sciences Corp. is now set for a Jan. 7 launch.
The spacewalk is the first by NASA astronauts since July.
See Now: OnePlus 6: How Different Will It Be From OnePlus 5?