The day after docking, Wetherbee will use Endeavour's robot arm to carefully pull P1 from its perch in the cargo bay. He then will hand the truss off to Canadarm2, operated by Whitson and Bowersox, who then will move it into position for attachment to the left side of S0.

The hand-off is required because the station arm can't reach into the cargo bay from its current position without hitting the shuttle's own robot arm support equipment.

"The P1 is unberthed from the shuttle using the shuttle (robot) arm, said Kirasich. "We tilt it up to get a little bit of additional clearance from the tail and then the shuttle arm performs what we call an arc maneuver that moves the truss from inside the shuttle bay out over the port wing of the space shuttle to what we call the handoff position.

"At the handoff position, the space station arm goes and grapples a second grapple fixture on the truss, we back the shuttle arm off and the shuttle arm is maneuvered to a position where it will provide camera views of the mating interface.

"At that point, the station arm maneuvers the truss to the pre-install position where we do a fine alignment," Kirasich said. "And then we perform a maneuver we call 'press to readies.' We bring the truss close enough where the truss can be captured by the capture latch on the segment-to-segment attachment system."

While the truss is being moved into position and attached to S0 with the capture latch and a set of four motorized bolts, Lopez-Alegria and Herrington will be preparing for the first of three spacewalks to complete the segment's installation and activation.

As the motorized bolts drive home, pulling S0 and P1 together with 13,500 pounds of force, the spacewalkers will exit the Quest airlock module and get to work.

Lopez-Alegria, call sign EV-1, will make the first of two sets of eight electrical connections needed to power-up the P1 truss' computers and other systems. Herrington, meanwhile, will release launch locks holding a new CETA cart in place on the truss rails, the station's second. The station's first CETA cart, carried into orbit attached to S1 last month, currently is coupled to the mobile transporter atop S0.

While Herrington - EV-2 - works to release the various CETA cart launch locks, Lopez-Alegria will install six SPDs on flexible hose radiator coupler fluid lines between the truss and its folded radiator panels.

The SPDs were ordered after an engineering analysis showed ammonia leakage past one of two seals in a typical quick-disconnect fitting could have the effect of pressurizing the fitting, making it difficult for future spacewalkers to release. The SPDs effectively pull each quick-disconnect apart slightly, just enough to allow any leakage to vent harmlessly into space.

Thirty-three SPDs were installed during Atlantis' mission last month. During the current flight, 43 more will be installed, six on the first spacewalk, four on the second and 33 on the third. Two more will be installed on the next shuttle visit in March.

After the first six are installed on the first spacewalk of Endeavour's mission, Herrington and Lopez-Alegria will remove and stow structural supports called "drag links" that helped hold P1 in the shuttle's cargo bay. They must be removed, as well as two massive keel pins, to clear the rails for eventual movement of the mobile transporter and CETA carts.

Once that work is done, Lopez-Alegria will make a second set of electrical connections between S0 and P1 before working with Herrington to mount a spacesuit "helmet cam" TV antenna on the back of the Unity node.

At present, video from the helmet cams of spacewalkers wearing U.S. spacesuits can only be seen inside the station when a shuttle is docked. The new WETA - wireless EVA television antenna - system will allow station crews to receive such video during spacewalks when the shuttle is not present.

At the end of the spacewalk, the Canadarm2 robot arm, attached to the mobile transporter on the S0 truss, will "walk off," inchworm style, and attach itself to a grapple fixture on the hull of the laboratory module. This will clear the way for the mobile transporter to be moved out onto P1 during the third spacewalk.

The day after the first spacewalk, the combined crews will focus on moving equipment and supplies from the shuttle to the station to support the Expedition 6 crew before staging a second EVA the next day. If time permits, they may also begin work to repair the carbon dioxide removal system in the Destiny module. The CDRA system has had problems in recent weeks and spare parts were launched aboard Endeavour.

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