For two Americans, Christmas Eve will be celebrated in outer space.
In orbit more than 200 miles above the planet, Flight Engineers Rick Mastracchio and Mike Hopkins are set to embark on a spacewalk to repair part of the International Space Station's cooling system.
It will be the second Christmas Eve spacewalk in history, according to NASA.
Here on Earth, astronaut Mike Massimino—who has performed four spacewalks himself—explains how the astronauts are setting up for the endeavor.
“Both of the astronauts are out there, making sure their tethers are good, and they’re getting in position to start their day's activities,” Massimino says.
The two engineers will be carrying out the second in a series of expeditions needed to replace a malfunctioning pump, which circulates ammonia through loops outside the station to keep equipment cool.
The pump developed problems December 11, when an internal valve stuck in an incorrect position. The space station's life support system remains up and running, but operations were cut back as a result of the failure, NASA said.
The two astronauts spent about five and half hours outside the space station on Saturday working to remove the problematic pump.
Massimino describes the difficulty of their task.
“It is a completely different environment,” he says. “The suit, the tools are different. Things float around. You have to constantly check your suit and make sure that’s all good. That makes it a little more challenging. But it’s also a lot of fun.”
If everything goes according to plan, the repair job will be completed today.