Replace 11 Of 12 Bearings In Solar Array Joint

The crew of the International Space Station celebrated the orbiting lab's 10th anniversary Thursday with a spacewalk by astronauts Heidemarie Stefanyshyn-Piper and Shane Kimbrough.

The second of four planned spacewalks planned for STS-126 began 45 minutes early, at 12:58 pm EST, and ended at 7:43 pm, running 15 minutes longer than its scheduled 6-and-a-half hours. Replacement of 11 of the 12 trundle bearings in the starboard Solar Alpha Rotary Joint race ring was successfully completed.

The repair comes almost a year after astronaut Dan Tani, in a spacewalk on November 24, 2007, noticed metallic debris on a main gear bearing race, suggesting metal-on-metal grinding which could lead to a failure of the joint.

The bearings allow rotating the solar array to track the position of the sun, which is essential to maximize power generation. The first of the 12 bearings was replaced back in June.

Now safely put in the shuttle Endeavour's payload bay, the bearings will be returned to Earth, where they'll be inspected, and engineers will try to determine what caused premature failure by subjecting the remaining good bearings to further analysis.

FMI: www.nasa.gov/station