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Astronauts Breeze Through Spacewalk at the International Space Station
NASA astronauts Mark Vande Hei and Randy Bresnik take a spacewalk outside the International Space Station on Oct. 10, 2017.
Credit: NASA TV

Two NASA astronauts ventured outside the International Space Station today (Oct. 10) to tackle the second in a series of three spacewalks taking place at the orbiting laboratory this month.

Expedition 53 Cmdr. Randy Bresnik and flight engineer Mark Vande Hei spent 6 hours and 26 minutes working on a number of maintenance tasks, including the lubrication of a new latching end effector (LEE) — the "hand" on the Canadarm2 robotic arm — which the two spacewalkers replaced during their last extravehicular activity (EVA) on Oct. 5.

After working together on a single task for the entirety of last week's spacewalk, the two astronauts spent much of their day flying solo while tackling a multitude of chores around the station. While lubricating the new LEE was a main objective, they also replaced and repaired external cameras and did some routine maintenance on the station's thermal control system. The astronauts breezed through their main tasks and accomplished some optional "get-ahead" tasks before wrapping up their work for the day. [Space Station Photos: Expedition 53 Mission Crew in Orbit]

This photo of NASA astronaut Randy Bresnik was taken by a new external camera that he and his crewmate Mark Vande Hei installed during a spacewalk on Oct. 10.
This photo of NASA astronaut Randy Bresnik was taken by a new external camera that he and his crewmate Mark Vande Hei installed during a spacewalk on Oct. 10.
Credit: NASA TV

Today's EVA officially began when the two spacewalkers switched their spacesuits over to battery power at 7:56 a.m. EDT (1156 GMT), after which they emerged from the Quest airlock and split up to conquer separate tasks. 

Vande Hei started off by heading up to the station's truss to the Mobile Transporter cart, where he retrieved a foot restraint and installed it on the Canadarm2 robotic arm. To do that, he first had to install a special socket onto the newly replaced LEE.

"I have a little bit of adrenaline going on right now. This view is amazing!" Vande Hei said as the space station passed over Rio de Janeiro. [Gallery: Amazing Photos of Earth from Space]

NASA astronaut Mark Vande Hei works on the latching end effector, or the "hand" at the end of the Canadarm2 robotic arm.
NASA astronaut Mark Vande Hei works on the latching end effector, or the "hand" at the end of the Canadarm2 robotic arm.
Credit: NASA TV

Bresnik kicked off his EVA by heading over to the high-pressure tanks just outside the airlock, where he reconfigured a handle that was "ever so slightly out of the locked configuration," NASA TV commentator Rob Navias said during a live webcast of the spacewalk. Four high-pressure tanks filled with nitrogen and oxygen are used to depressurize and repressurize the airlock before and after spacewalks, Navias said.

With the latch on the high-pressure tank back in place, Bresnik made his way over to the port side of the International Space Station (ISS) to work on a spare Pump Flow Control Subassembly (PFCS) outside the Destiny module. Vande Hei met up with Bresnik at the PFCS to help him rotate the assembly into an orientation that will allow an ammonia pad to be vented during a later spacewalk, NASA's EVA officer Glenda Brown explained in a briefing on Oct. 2.

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Then the spacewalkers briefly split up again, with Vande Hei heading back to Canadarm2 and Bresnik going to fetch a tool bag for his crewmate. That bag contained a replacement camera group to be installed on the Port 1 (P1) truss segment.

Vande Hei mounted the end of Canadarm2 using the foot restraint he installed earlier in the spacewalk. Inside the space station, European Space Agency astronaut Paolo Nespoli operated 58-foot (17.6-meter) robotic arm to bring Vande Hei right in front of the camera port where he needed to be to replace a failed camera group.

The camera group that was swapped out had a faulty color wheel that added a pink hue to the images, Navias said. During the next spacewalk on Oct. 18, Bresnik and NASA astronaut Joe Acaba will replace another faulty camera group that is causing a similar problem, producing images with a yellow hue.

Following Vande Hei's struggle to bolt down one of two secondary bolts that affix the camera group to the space station, the ground control team at NASA's Johnson Space Center in Houston decided it was alright to leave that bolt as is. "No worries, that new camera group is firmly affixed and will not float away," Navias said. With the new camera group in place and functioning properly, Bresnik returned to the Mobile Transporter to replace a smudged camera lens cover with a clean one.

NASA astronaut Mark Vande Hei holds the ballscrew lubrication tool in front of Canadarm2's latching end effector in this view from his spacesuit's helmet cam.
NASA astronaut Mark Vande Hei holds the ballscrew lubrication tool in front of Canadarm2's latching end effector in this view from his spacesuit's helmet cam.
Credit: NASA TV

Meanwhile, Nespoli used Canadarm2 to bring Vande Hei back to the forward face of the truss, where he dismounted the robotic arm and fetched another tool bag for his next big task: lubricating the LEE. For this he needed to pick up a device called a ballscrew lubrication tool —more commonly referred to as a BLT. The BLT looks a lot like a caulk gun, but instead of squirting a sealant around sinks and windows, the BLT is used to inject grease into various mechanisms on Canadarm2.

Vande Hei worked so efficiently lubricating the LEE's center ball screw that he had extra time to work ahead on tasks slated for next week's spacewalk, like lubricating four latch ball screws inside the grappling fixture. This will help take a load off next week's spacewalkers, who will finish lubricating the LEE on Oct. 18.

Before heading back, Bresnik relocated two handrails to make way for an antenna that will be part of a new external wireless system that will be installed on a future EVA.

After spending a total of 6 hours and 26 minutes working outside the ISS, the astronauts returned to the Quest airlock and concluded their spacewalk at 2:22 p.m. EDT (1822 GMT). It was "a very productive day for Bresnik and Vande Hei," Navias remarked at the end of the webcast.

Today's EVA marks the fourth in Bresnik's career and brings his cumulative spacewalking time to 25 hours and 11 minutes. Bresnik previously did two spacewalks during the space shuttle mission STS-129 in 2009. (He finished his very first EVA just hours before his wife gave birth to his daughter back on Earth.)

Vande Hei, a first timer aboard the ISS, has now completed his first two spacewalks, giving him a cumulative spacewalking time of 13 hours and 21 minutes.

Email Hanneke Weitering at hweitering@space.com or follow her @hannekescience. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.