P1 was removed from Endeavour's payload bay at 9:22 a.m. CST by the shuttle's robotic arm, operated by Commander Jim Wetherbee. He handed it off to the station's Canadarm2, operated by Expedition 6 commander Ken Bowersox and Expedition 5 NASA ISS Science Officer Peggy Whitson, and released the shuttle arm's grip on P1 a little before 11 a.m. Whitson and Bowersox maneuvered the 14-ton, 45-foot truss segment to its installation position.
P1 is the third segment of the Integrated Truss Structure to be installed this year. A fourth segment, the P6 truss, supports the 240-foot-long solar arrays atop the station. It was installed there in December 2000 and will be moved later to the left end of the station's backbone. At completion, the integrated truss will consist of 11 segments stretching the length of a football field.
The spacewalk began at 1:49 p.m., about 30 minutes earlier than planned, after the four bolts securing the P1 to the S0 truss centerpiece had been driven home by remote commands. The spacewalk ended a little before 8:35 p.m. for a total time of 6 hours and 45 minutes.
Herrington and Lopez-Alegria hooked up electrical connections between P1 and the station, installed spool positioning devices designed to ensure that quick disconnect devices in fluid lines will function properly, and released launch locks securing the Crew and Equipment Translation Aid (CETA) cart, a kind of hand car for the truss railway. The two spacewalkers also removed two drag links, large metal rods that had supported P1 during launch, and stowed them in the P1 framework. Finally, after Herrington had topped off his oxygen supply in the airlock, they installed Node Wireless video system External Transceiver Assembly (WETA) antennas allowing reception from spacewalkers' helmet cameras without a shuttle present.
Endeavour Pilot Paul Lockhart, with help from Bowersox and Expedition 6 Science Officer Don Pettit, served as intravehicular officer during the spacewalk, coaching Lopez-Alegria and Herrington through their tasks and keeping them on the timeline.
The spacewalk was the 22nd station-based spacewalk, and brought the total time for space station spacewalks to 292 hours, 10 minutes. There have been 25 shuttle-based assembly spacewalks.
Lopez-Alegria, wearing the spacesuit with red stripes, and Herrington, in the all-white spacesuit, will conduct two more spacewalks, each scheduled for 61/2 hours, on Thursday and Saturday. Both will focus on making additional connections between the new truss segment and the station, and outfitting the P1.
Expedition 5 Commander Valery Korzun, Whitson and Flight Engineer Sergei Treschev conducted handover discussions with their Expedition 6 successors, Bowersox, Pettit and Flight Engineer Nikolai Budarin, during parts of the Tuesday spacewalk.