Animation shows the PMA being removed from its temporary storage site on the Z1 truss. Photo: NASA TV/Spaceflight Now

Atlantis' spacewalking astronauts Tom Jones and Bob Curbeam plan to step outside the shuttle again on Monday to lend a hand attaching a cone-shaped docking port to the newly-installed Destiny lab.

The primary goal of the mission's second spacewalk is to move pressurized mating adapter No. 2 from its temporary mounting point on the Z1 truss and to attach it to the far end of the Destiny module to permit subsequent shuttle dockings.

Jones and Curbeam also plan to install a so-called power and data grapple fixture to Destiny's hull that later will serve as the mounting point for the space station's Canadian-built robot arm.

Other tasks include attachment of a slidewire for use by future spacewalkers and installation of thermal covers over the massive trunnion pins used to mount the lab in the shuttle's cargo bay.

While the spacewalk is going on, flight controllers will begin testing the control moment gyroscopes, making for another busy day in space for the astronauts and ground crews alike.

"The first spacewalk is basically to prepare Destiny for activation," Curbeam said. "The second spacewalk is basically to get ready for the rest of the assembly sequence."

A half-hour or so before Jones and Curbeam exit Atlantis' airlock, Ivins will grapple PMA-2 with the robot arm. But the common berthing mechanism on the temporary attachment fitting is a manually operated system.

"We have to get Tom up there first before we can do anything," Cockrell said. "He has to come up and be ready to unlatch PMA-2 from the Z1. Marsha grapples PMA 2. Tom unlatches it. And then she takes it down to the end of the lab and installs it on the leading edge of the front-end cone of the lab.

"PMA 2, on the front of the lab, will be where the next several flights dock to. So, it's important that it gets installed there; otherwise, there's a break in the assembly process."

But the crew will take its time tightening the 16 bolts in the lab's active common berthing mechanism.

PMA No. 2 is attached to the end of Destiny. Photo: NASA TV/Spaceflight Now

"Because it's been in a different thermal condition up on Z1 than the front of the lab has been, we will only partially bolt it down," Cockrell said. "We'll bolt it down tight enough to where she can let go of it with the arm, but then it needs to sit there and wait 12 hours while the temperatures equalize on the two interfaces.

"We'll come back to it later and do the final torquing of those bolts," he added. "It depends on how smoothly that goes what else we get done on EVA two."

Once PMA-2 is attached to the lab, Ivins will be free to help Jones and Curbeam attach the power and data grapple fixture to Destiny's hull.

Jones, anchored to the end of the arm, will retrieve the grapple fixture from its mounting point in the cargo bay while Curbeam peels back micrometeoroid shielding protecting Destiny's outer skin where the PDGF will be installed.

"It's just a grapple fixture that you've seen on all sorts of payloads on shuttle and space station elements," Jones said. "But this one's a little bit more capable in that it provides electrical connections into the laboratory from the outside.

"And not only electrical connections but a video feed so that the cameras on the arm can be monitored from inside the laboratory and later from other workstations inside the station cupola, for example."

The new grapple fixture -- highlighted in light blue -- is installed on Destiny. Photo: NASA TV/Spaceflight Now

It will take the spacewalkers two hours or so to complete the installation, attaching power lines, installing a video signal converter for a fiber optic link to the interior of the station and then re-installing the debris shielding.

"There are a number of other minor outfitting chores on the EVA and installing a slide wire for translation safety up and down the lab, installing foot restraints for other work that we're going to be doing and other crews will be doing on the spacewalk.

"But the major tasks are getting that docking port relocated and then providing the foundation for the robotic operations outside."

The spacewalk is scheduled to last about six hours. Overnight, while the crews sleep, flight controllers in Houston will send commands to complete the tightening of the bolts in the lab's forward common berthing mechanism to firmly lock PMA-2 in place.

Hatches between Atlantis and the space station will remain closed throughout the day on Tuesday. The astronauts will enjoy a bit of off-duty time and carry out another in the series of reboost operations to increase the station's altitude.