The goal of the second excursion is to install ammonia fluid-line jumpers, to remove the two keel pins used to physically secure P1 in the shuttle's cargo bay for launch, to install a second WETA antenna system on the P1 truss and to move the new CETA cart from the P1 truss to the S1 truss on the opposite side of the station.

The latter promises to be particularly dramatic. Herrington, anchored to the end of the station's robot arm, will manually hold the 600-pound CETA cart while the arm, operated by Pettit and Bowersox, swings him through a sweeping 180-degree arc to the opposite side of the truss.

The cart must be moved before the third spacewalk of the flight to permit the Canadarm2's mobile transporter to move from its current location at worksite 4, on the front of S0, to worksite 7 on the far end of P1, where it will be needed to complete EVA-3 activities.

"One of the neat things I get to do at the end of EVA-2 - this will probably be the high point of all the EVAs for me - is to climb on board the robotic arm with Don at the controls," Herrington said. "And I'll be taking the CETA cart from the left side of station to the right side of station.

"I'll lift it off, we'll back away from the truss a little bit, then Don will put the arm through a maneuver that will take me completely past the tail of the shuttle and back up around to the right side of the station where we'll move it back in slowly, with Mike guiding me, and we'll put it back onto the rails. So that's going to be a real exciting time, I'll get to see the station from a pretty neat perspective."

But Pettit said the drama will be a strictly slow-motion affair.

"Nothing like this happens really fast," he said. "I mean if you sat there and watched the arm move, you've got to blink a few times to see whether it's really moving. So we're not going to be trying to set any world records here. It takes about 20 minutes to do this trajectory, so there'll be plenty of time to run off to the refrigerator and grab another soft drink."

The first item on the agenda for EVA-2 is to install fluid jumpers between S0 and P1 to connect ammonia coolant lines. Both spacewalkers, their feet anchored in foot restraints, will be required to complete this objective.

"These are large hoses that actually connect the S0 truss to P1 truss and it'll allow us to flow ammonia, which is a cooling agent we use with the radiators," Herrington said. "That's our first task, that's probably the hardest task in that EVA."

Herrington and Lopez-Alegria then will remove and stow the starboard keel pin before using the CETA cart to carry the second WETA antenna assembly to the end of P1. Lopez-Alegria will mount the assembly while Herrington releases clamps on electrical cables that will be used on an upcoming assembly flight. He also will inspect the system that will be used to clamp the next port-side truss element to P1.

Both spacewalkers then will remove and stow the port keel pin before performing the CETA cart relocation maneuver to conclude the six-and-a-half-hour excursion.

The next day, the shuttle astronauts will continue moving supplies and equipment to and from the shuttle while the incoming and outgoing station crews spend most of the day in handover activities to familiarize Bowersox and company with the intricacies of station operations.

Then the stage will be set for the third and final spacewalk the following day, a complex set of activities needed to complete P1's installation and at the same time, test the techniques and procedures needed to move the station's robot arm back and forth along the truss for upcoming assembly missions.

"What you're going to see on this EVA, while the spacewalkers are in the airlock performing their pre-breathe activities, you're going to see a ballet, or a choreographed sequence of events that will move the mobile transporter from its current location at worksite 4 (on S0), down the tracks to worksite seven (at end of P1)," Kirasich said.

The next elements in the port-side truss build-up "can only be installed with the arm on the mobile transporter and the mobile transporter at worksite 7," he said. "So it's very important we can get the MT to that location."

To make that happen, the robot arm was walked off the MT to the lab module, the astronauts removed the keel pins and drag links and moved CETA cart 2 from P1 to S1.

Before the third spacewalk begins, the mobile transporter will be commanded to move from worksite 4 to worksite 7 on the end of P1. Once the transporter is plugged into its power-and-data socket at work site 7, Canadarm2's free end will lock onto one of the transporter's grapple fixtures. The crane then will release a fixture on the lab module to complete the "walk off" to the transporter.

With the arm now ready for work in its new position, Lopez-Alegria will install two SPDs on ammonia lines at the interface between the Z1 and P6 trusses atop the Unity module. He will install two more in the "rat's nest" of coolant lines and cables between Z1 and the lab module.

Finally, Lopez-Alegria will hook up two more SPDs on a heat exchanger below the outer skin of the lab's end cone.

While that work is going on, Herrington will install 18 SPDs on the rotary beam valve modules on the back of P1 where quick-disconnect fittings link ammonia lines leading from the truss to the radiators. Twelve of those fittings will be attached while Herrington is on the Canadarm2. He then will get off the arm, the arm will walk back off to the lab and Herrington will install the final 6 SPDs as a "free floater."

Lopez-Alegria, meanwhile, will install four SPDs on P1's ammonia pump module, reconfigure power cables, hook up the truss ammonia tank and prepare the ammonia system for filling during a flight next year.

The spacewalk will end after installation of a final set of SPDs on the flexible hose rotary coupler, part of the system that enables the radiators to rotate to ensure maximum cooling.

At the conclusion of the third spacewalk, P1 will be ready for attachment of the next port-side truss segment and 76 of 78 required SPDs will have been installed. The final two will be installed during the next station assembly mission in March.

"STS-112, the S1 truss installation (in October), went extremely well," said station program manager Bill Gerstenmaier. "It was a very good rehearsal for the STS-113 P1 truss. When you take a look at the mission, it's going to appear to you that STS-113 P1 looks a lot like the STS-112 flight. And I would tell you that it's really not.

"We're going to move a CETA cart, a crew EVA translation aid cart, from one side of the truss to the other, and that'll be a big movement. And then you'll also see the mobile transporter being moved from worksite 4, at kind of the center of the truss, out to worksite 7, which will be on the P1 truss.

"So this will be the first time the mobile transporter has moved across an interface between two truss segments," he said. "The reason we're doing this on this flight is to set ourselves up for next year's activities. We need to operate off of that worksite to install some of the outboard truss elements and we want to gain some experience in using the mobile transporter, seeing how it operates, actually moving it in a time critical fashion out to this worksite.

"You'll also notice when this activity occurs that we don't move the arm on top of the mobile transporter," Gerstenmaier said. "The arm will be walked off the mobile transporter to the lab. Then the mobile transporter will be moved out and then the arm will walk back onto the truss. So when you see that activity, that's dramatically different from what we did back on the last flight on the S1 install.

"On the S1 install, we stayed on one worksite, we used the arm all from that worksite. On this flight, you'll see a lot of mobile transporter movement, you'll see a lot of arm activity moving to different locations. That was done really because of where we have to reach on this P1 truss and it's also driven by the fact that we want to test in advance these new capabilities we're going to use on future flights.

"So just as we've been doing throughout the assembly sequence, anything we can do ahead of time to make sure it's operating, to make sure it works ... we do that," Gerstenmaier said. "So we're really getting prepared on this flight, this P1 flight, for future activities that we're going to have to do next year."

Following the third spacewalk, the Endeavour astronauts and the Expedition 6 crew will enjoy a half-day off and a bit of final transfer activity before undocking the next day.

With pilot Lockhart at the controls, Endeavour will pull straight away from the station to a distance of about 400 feet. From there, Lockhart will guide the shuttle through a photo-documentation loop around the outpost before leaving the area for good. Endeavour is scheduled to land Dec. 4 at the Kennedy Space Center.

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