At 11:41 a.m. EST (1641 GMT), astronaut Peggy Whitson operated the station's Canadarm2 and grabbed hold of the P1 truss, taking it from the shuttle's arm to move it into its final attachment position next to the S0 truss that is bolted atop the Destiny science module.

At that point the shuttle's robot arm was finished with its heavy lifting and officials later noted there were no problems with the arm as a result of the damage inflicted on it by a work platform back at the Kennedy Space Center.

As all of this was going on, Endeavour mission specialists Michael Lopez-Alegria and John Herrington were suiting up to go outside on the first of three spacewalks planned for this mission.

Those preparations were complicated just a little bit by the failure of the station's bicycle device, which is used by the spacewalkers as part of an exercise protocol to help them pre-breathe pure oxygen more quickly.

Like deep sea divers, spacewalkers must purge nitrogen gas from their bodies before going outside or they could risk an attack of severe cramps, commonly known as the bends.

Wearing portable oxygen masks, Lopez-Alegria and Herrington rode the shuttle's exercise equipment to complete the job without delaying the start of the spacewalk.

The pair officially began their spacewalk at 2:49 p.m. EST (1949 GMT) and ended it six hours and 45 minutes later. The extravehicular activity was the third for Lopez-Alegria, but the first for Herrington, a space rookie.

"What a fabulous view," Herrington said as he left the orbiting outpost for the first time and saw the scene of Earth below.

A few moments later, Lopez-Alegria -- speaking as the voice of experience -- attempted to remind Herrington about what to expect in space compared to the simulations in the swimming pool: "The biggest difference you're going to notice, John, is the, um..."

"Is the Earth?" Herrington interrupted, laughing.

"OK, the second biggest difference," Lopez-Alegria said, "is that you don't have any brakes out here." Without the dampening effect from the water, things move a lot easier in the vacuum of space. "Slow is good, take your time. You've got six and a half hours, give or take."

During that time the duo completed all the tasks on their "to do" list, including:

• Connecting 16 power, data and fluid lines to two trays on the P1 truss, supplying it with the energy it needed to come alive electrically and be ready to support keeping the station cool when all of its systems are activated some time next year.

• Installing small brackets on the ends of several ammonia quick-disconnect valves that will make it easier for future spacewalkers to service those lines as needed.

• Removing locks that held a mobile equipment cart in place during launch and braces that securely held the truss within the shuttle's cargo bay during the climb to orbit.

• Attaching a set of antennas to the outside of the station that will help transmit helmetcam pictures from future spacewalkers. Currently those remarkable views can only be seen when a shuttle is present to relay the signals. The new wireless system will take care of that limitation.