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Space Station Astronauts Are Taking a Spacewalk Today: Watch It Live
Astronauts Richard Arnold (bottom) and Joseph Acaba are pictured during a spacewalk in March 2009. The two astronauts were visiting the space station as STS-119 mission specialists aboard space shuttle Discovery.
Credit: NASA via collectSPACE.com

Two astronauts will take a spacewalk outside the International Space Station (ISS) today (Oct. 5), kicking off a trifecta of spacewalks set to take place over the next two weeks.

In this first spacewalk, NASA astronauts Randy Bresnik and Mark Vande Hei will replace an aging machine called the Latching End Effector (LEE) at the end of the Space Station Remote Manipulator System (SSRMS), or Canadarm2. The LEE works like a hand at the end of the robotic arm and grapples incoming cargo spacecraft like SpaceX's Dragon and Orbital ATK's Cygnus. 

At about 8 a.m. EDT (1200 GMT), Bresnik and Vande Hei will exit the Quest airlock and head out into the void of space to swap out the old LEE with a new one. The 6.5-hour spacewalk is expected to wrap up at around 2:30 p.m. EDT (1830 GMT). You can watch all the action in a livestream here, courtesy of NASA TV. 

Live coverage of the spacewalk will begin at 6:30 a.m. EDT (1030 GMT), when the two spacewalkers will put on their spacesuits. European Space Agency astronaut Paolo Nespoli and NASA astronaut Joe Acaba will assist the spacewalkers with their suits and help them out the door. [Space Station Photos: Expedition 53 Mission Crew in Orbit]

During three spacewalks on Oct. 5, 10 and 18, astronauts will replace an aging Latching End Effector (LEE) at the end of the Canadarm2 robotic arm. The LEE works as the "hand" of Canadarm2 and is used to grapple incoming cargo spacecraft.
During three spacewalks on Oct. 5, 10 and 18, astronauts will replace an aging Latching End Effector (LEE) at the end of the Canadarm2 robotic arm. The LEE works as the "hand" of Canadarm2 and is used to grapple incoming cargo spacecraft.
Credit: NASA

"The major objective of this first spacewalk is to swap out the degraded Latching End Effector on the Canadarm2 with an identical unit that's currently located on the mobile transporter" outside the space station, Judd Frieling, NASA's spacewalk flight director, said at a news conference Monday (Oct. 2).

Frieling said wear and tear on the LEE became problematic in August, when the latches inside the grapple fixture "stalled out" and "required a little bit more force than normal to extend." 

This came as no surprise, however, as the two LEEs on Canadarm2 have already exceeded their life expectancy, said Tim Braithwaite, the ISS program liaison for the Canadian Space Agency. Components of the LEEs were designed to last 10 to 15 years, and it's been 16 years since they were installed. "We're actually very pleased that both LEEs lasted this long," he said. "We thought we'd probably be doing this maintenance before now."

When the spacewalk begins, Nespoli will head to the robotic workstation, where he will be able to remotely operate Canadarm2 and help the two spacewalkers reach the LEE at the end of the arm. Nespoli will position the LEE between the two spacewalkers as they dangle from foot restraints on the space station's truss. 

While conducting a spacewalk during shuttle mission STS-123 in 2008, NASA astronaut Rick Linnehan is anchored to the end of Canadarm2. Expedition 53 astronauts Mark Vande Hei and Joe Acaba will also "stand" on Canadarm2 during spacewalks on Oct. 10 and Oct. 18.
While conducting a spacewalk during shuttle mission STS-123 in 2008, NASA astronaut Rick Linnehan is anchored to the end of Canadarm2. Expedition 53 astronauts Mark Vande Hei and Joe Acaba will also "stand" on Canadarm2 during spacewalks on Oct. 10 and Oct. 18.
Credit: NASA

After loosening some bolts and screws, the spacewalkers will stow the degraded LEE outside the space station and replace it with a spare LEE. Then, they'll gather their tools and head back to the Quest airlock. 

The next two spacewalks, on Oct. 10 and Oct. 18, will focus on lubricating the joints in the new LEE using a device called a ballscrew lubrication tool, or BLT. Bresnik and Vande Hei will conduct the second spacewalk together. For the third spacewalk, Acaba will join Bresnik instead. 

Today's spacewalk marks the third of Bresnik's career and the first for Vande Hei. To tell the two apart during the webcast, look for the red stripes on Bresnik's suit. As extravehicular crewmember 1 (EV 1), Bresnik gets to wear the suit with red stripes on it, while Vande Hei (EV 2) will wear a plain white suit. 

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