Spacewalkers Replace Station Gyroscope, 3 Days Added to Shuttle Mission

August 13, 2007

Astronaut Rick Mastracchio holds the failed control moment gyro shortly after its removal from the Z1 truss. Image: NASA TV

STS-118 spacewalkers Dave Williams and Rick Mastracchio installed a new control moment gyroscope (CMG) into the International Space Station’s Z1 truss. They will secure the faulty CMG and equipment before wrapping up the excursion.

The new CMG replaced a faulty gyroscope, which was removed during the first half of the spacewalk. The failed gyro will remain at its temporary stowage location on the station’s exterior before it is returned to Earth on a later shuttle mission. The new gyroscope is one of four CMGs that are used to control the station’s attitude in orbit.

The excursion began 11:32 a.m. EDT. Mission Specialist Tracy Caldwell is serving as the spacewalk coordinator, and STS-118 Pilot Charles Hobaugh and Expedition 15 Flight Engineer Clay Anderson are operating the station’s robotic arm. The spacewalk is scheduled to wrap up about 6 p.m.

Meanwhile, crew members are transferring cargo between Endeavour and the station. Experts on the ground continue to analyze imagery collected Sunday during the STS-118 crew’s focused inspection of five areas of concern on the Endeavour’s heat shield.

Managers Add Three Days to Shuttle Mission

Mission managers decided Sunday to extend the STS-118 mission by three days. The decision came after the successful operation of the new Station-to-Shuttle Power Transfer System (SSPTS).

Endeavour is now scheduled to undock from the International Space Station on Aug. 20 and land 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.

The SSPTS reroutes power from the space station to the shuttle during docked operations, allowing the orbiter to conserve materials needed to generate power and spend more time in space.

Source: NASA