NASA astronauts Rick Mastracchio and Michael Hopkins are once again floating outside the International Space Station, in the second scheduled effort to repair the station's malfunctioning coolant system and only the second Christmas Eve spacewalk in NASA history.

The need for repairs was brought about by one of the ISS' two coolant loops unexpectedly shutting down on December 11th. Since then, the crew has had to turn off nonessential equipment to conserve power. Today's effort follows Saturday's successful mission, during which the engineers managed to remove a failing ammonia pump. The live feed of the repairs can be viewed below:


Live streaming video by Ustream

The last Christmas Eve spacewalk took place in 1999, when astronauts conducted repairs on the Hubble Space Telescope.

Update: The crew has successfully installed a new ammonia pump, negating the need for a third spacewalk:

Update 2: NASA announced on Twitter that the spacewalk is finally over. The astronauts have logged a total of 46 days outside the ISS doing maintenance, including this mission: