NASA astronauts Rick Mastracchio and Michael Hopkins are several hours into the first of three spacewalks intended to repair the International Space Station's malfunctioning coolant system. On December 11th, one of the station's two coolant loops unexpectedly shut down; soon after, astronauts turned off some nonessential equipment in an effort to reduce power load. NASA says that none of the six ISS crew members are in any immediate danger, but the space agency still wants the problem fixed to avoid any other sudden failures. The live feed of the spacewalk can be viewed below.

During the spacewalks (each is expected to last around 6.5 hours), Mastracchio and Hopkins will attempt to replace a faulty cooling module. The repair mission will mark the first time Mike Hopkins has conducted a spacewalk; NASA showed Hopkins preparing for the task on its Instagram feed yesterday. Mastracchio is no stranger to leaving the confines of the ISS, as he has already been involved in six other spacewalks.

Retired Canadian astronaut Chris Hadfield, who earlier this year led the ISS during Expedition 35 (and made some history of his own), is currently answering questions about the spacewalk mission on Twitter.

.@Murmannnn We're limited by CO2 removal, battery power, and crew fatigue. About 9 hours absolute maximum. — Chris Hadfield (@Cmdr_Hadfield) December 21, 2013

Update: The New York Times reports that the crew has partially repaired the ammonia pump needed for the ISS coolant system ahead of schedule. The next repair walk is set for Tuesday.