NASA astronauts Jeff Williams and Kate Rubins are taking their second stroll through space together today, just two weeks after their last spacewalk to install a new docking adapter to the outside of the International Space Station. But this time, their spacewalk will involve doing some outside cleanup.

The main purpose is to retract and cover a back-up thermal radiator

The main purpose of the spacewalk is to retract and cover a back-up thermal radiator that’s part of the station’s cooling system. The radiator was extended in 2012 to help fix a coolant leak, but it’s not in use anymore. So NASA wants to pack the radiator up so that it doesn’t get damaged by any orbital debris. However, NASA has had problems with this radiator before. Astronauts Scott Kelly and Kjell Lindgren tried to retract it in a November spacewalk, but were unable to keep it in place. So they were forced to extend it again.

Hopefully, Williams and Rubins can get the radiator fully retracted and covered this time around. If they’re successful, they will then have some struts to tighten on a solar array, which have been vibrating a bit lately, as well as a new camera lightbulb to install; even in space, your bulbs burn out. The team will also install an enhanced HD-camera to the outside of the ISS. The camera is the first of many that will be used to monitor what’s going on outside the station, such as all the cargo and crew that make their way to the ISS. If Williams and Rubins work fast enough, they have the option of installing another one of these cameras at the end of the spacewalk today.

The two astronauts have already gotten started after leaving the ISS a little before 8AM ET this morning. NASA’s spacewalks are typically planned to last 6.5 hours, so there's still plenty of time to watch them hard at work in the vacuum of space.