NASA Astronauts Go on a Spacewalk

Canadian astronaut Dave Williams and NASA’s Rick Mastracchio embarked on another spacewalk Monday at the International Space Station.

The primary task of the 6 1/2-hour spacewalk was to replace a faulty attitude control gyro. The spacewalk officially began at 11:32 a.m. EDT and was the second of four to take place during the shuttle Endeavor’s stay at the station.

The faulty gyro is one of four devices, called control moment gyros, or CMGs, that are used to control the station’s orientation. Endeavour delivered the new CMG to the station.

Astronaut Tracy Caldwell is serving as the mission’s spacewalk coordinator, with shuttle pilot Charles Hobaugh operating the station’s robot arm.

Mission managers Sunday decided to extend the STS-118 mission by three days. Endeavour is now scheduled to undock Aug. 20 and land back on Earth Aug. 22. In addition to the extra time at the orbital outpost, managers added a fourth spacewalk that is scheduled to take place Aug. 17.