NASA is carrying out emergency repairs on the International Space Station today to try to fix an ammonia coolant leak discovered earlier this week. While the crew of the ISS is safe, NASA has sent astronauts Tom Marshburn and Chris Cassidy on a short-notice spacewalk to attempt to find the source of the leak. According to NASA, the spacewalk will last for about six-and-a-half hours. If the two astronauts are unsuccessful, NASA may decide to shut down one of the power systems abord the space station. Such a move would hamper research efforts of the current ISS crew. You can watch a livestream of the spacewalk, which began at 8:44AM EDT, below.

Update: NASA has announced on Twitter that the astronauts have successfully replaced the pump controller box, which was suspected to be the cause of the ammonia leak.