The crew members were awakened at 11:29 a.m. CDT, to Heartland's 'I Loved Her First.' The song was played for Endeavour Commander Dominic Gorie.
Preparations for today's spacewalk are scheduled to resume at 12:08 p.m., and Mission Specialists Mike Foreman and Robert L. Benhken should be ready to begin the spacewalk by 4:23 p.m.
The first task on the astronauts' agenda is to store on the station's truss the Orbiter Boom Sensor System -or OBSS -used in Friday's inspection of Endeavour's heat shield. Normally, the OBSS is brought back by the space shuttle on each trip. This time, however, the OBSS is being left on the station to leave extra room in the cargo bay of space shuttle Discovery, the next shuttle to visit the space station. Discovery will be bringing the Japanese Experiment Module to the station, and there is not enough room in the cargo bay for both it and the OBSS. Discovery will bring the OBSS back to Earth at the end of its mission.
After the OBSS is safely stored, the astronauts will split up for the spacewalk's other tasks. Behnken will again try to install the Materials International Space Station Experiment 6 (MISSE-6) on the exterior of the Columbus laboratory. Behnken and Mission Specialist Rick Linnehan attempted to install the MISSE-6 experiment during the mission's third spacewalk, but were unable to engage latching pins used to hold the experiment packages onto the hull of Columbus. This time around Behnken has a few troubleshooting methods he can try if he runs into the same problem again.
While Behnken works on installing the experiment, Foreman will inspect the station's right Solar Alpha Rotary Joint. The 10-foot-wide, 2,500-pound rotary joint, which rotates the station's starboard solar arrays to track the sun, began showing increased vibrations and power usage last fall. Previous inspections have found metal shavings under the rotary joint's insulation covers, and Foreman will be looking at an area previously photographed to determine whether a pockmark seen in the photos is more metal shavings or damage from micrometeoroid orbital debris.