Astronauts from the International Space Station on Monday embarked on a third spacewalk to fix the orbiting station's busted cooling system, NASA said.
Spacewalkers Doug Wheelock and Tracy Caldwell Dyson began their work on installing a spare ammonia pump module on the ISS at 6:20 am (1020 GMT) the US space agency said.
Flight Engineer Shannon Walker assisted the effort from inside the ISS by operating the station's robotic arm.
The ammonia pump failed unexpectedly on July 31 and was removed from the station during a spacewalk last Wednesday.
A first spacewalk to begin repairs on the cooling system took place on August 7 and lasted a record eight hours, three minutes.
Astronauts have been using a back-up cooling system, and NASA said conditions on the ISS are stable and the station's crew of three Americans and three Russians are not in danger.
Copyright 2010 AFP American Edition
