Rick Mastracchio and Mike Hopkins removed a faulty ammonia pump Saturday, December 21 while working outside the orbiter for more than five hours.
In this image made from video provided by NASA, astronaut Rick Mastracchio performs a space walk outside the International Space Station, Dec. 21, 2013.
Astronaut Rick Mastracchio (L) checks out the spacesuit that he will wear during a spacewalk with crew member Mike Hopkins at the International Space Station in this undated image taken from video from NASA TV.
Astronaut Mike Hopkins checks out the spacesuit he will be wearing on a spacewalk at the International Space Station, in this undated handout photo from NASA.
Flight engineers Michael Hopkins and Rick Mastracchio perform a series of spacewalks outside the International Space Station in this Dec. 21, 2013 still image taken from a NASA handout video.