Raffaello is mounted to the international space station to deliver supplies, equipment and experiments to the outpost. Photo: Spaceflight Now/NASA TV

With the shuttle's cabin air pressure back up to 14.7 psi, hatches between Endeavour and the station will be opened for the first time early the next morning.

The station crew plans to begin tests and checkout of the new robot arm while the shuttle astronauts use Endeavour's robot arm to attach the Italian-built Raffaello cargo carrier to Unity module's nadir port.

Raffaello is the second such cargo carrier provided by the Italians. It is loaded with some 7,500 pounds of equipment, experiment racks and supplies, including enough food to last the Expedition Two crew for two full months. The crew will not enter the module until the next day, after its interior has been warmed up.

While the Raffaello work is going on, Helms and Hadfield will be putting the new arm through its paces from a robotic work station in the Destiny module.

"We'll just basically be moving the joints through some of the range of travel ... and doing a checkout of the primary string and a little bit of the backup string," Engelauf said. "We've prioritized the checkout activities to get the most important things (done first) to ensure we've got a functional arm before we transfer power to the station grapple fixture."

The next day, with hatches between Endeavour and the station once again sealed, the Expedition Two crew will enter Raffaello to begin moving supplies and equipment aboard while the shuttle crew stages another spacewalk.

A view inside Raffaello's twin -- the Leonardo module that flew to the station on the last shuttle mission a month ago. Photo: NASA

The primary goal of the second excursion is to make electrical connections needed to route power to the new robot arm's PDGF. Parazynski, riding on the end of the shuttle's robot arm, will make those connections at a utility panel.

"We'll be doing a lot of the re-wiring to basically enable the space station arm to live on the space station permanently," Parazynski said. "We'll go out and with Chris's help, take off a shield on the side of the laboratory module and I'll spend the next hour and a half or so doing some fairly delicate work, surgery almost, rewiring some very delicate fiber optic cables to enable the space station arm to live permanently on the station."

Hadfield, meanwhile, will remove a no-longer-needed UHF antenna from Unity's starboard port, where the station's main airlock will be installed during a mission in June, before disconnecting the Spacelab Pallet umbilicals that initially powered the SSRMS.

Once the station's arm is powered through the PDGF, Helms will use it to lift the Spacelab Pallet off the lab cradle assembly to make room for Parazynski to mount a 400-pound spare DC power converter on the station's hull.

The arm, with the 3,000-pound Spacelab Pallet attached to one end, will be left in an extended position overnight. The shuttle crew, meanwhile, will repressurize Endeavour's cabin to 14.7 psi and re-open hatches to the station.

The next day, Helms and Hadfield will continue testing the new arm's capabilities with a so-called "loaded checkout."

"This is basically moving the Spacelab Pallet through a series of motions to demonstrate the capability of the arm to operate with an object on the end of it," Engelauf said.

Illustration of the Spacelab pallet being handed from one robot arm to the other in a dramatic show above Endeavour's payload bay. Photo: Spaceflight Now/NASA TV

"We will hand off the Spacelab Pallet to the shuttle arm during this day. And this is a first time activity, we've not done anything like this in spaceflight history. It will demonstrate a truly integrated operation between the crews and should be quite interesting to watch."

After the handoff is complete, Ashby will re-berth the pallet in the shuttle's cargo bay for return to Earth. And while all of that is going on, the combined crews will be continuing work to unload the Raffaello module and to install powered experiments from the shuttle's middeck to the newly installed lab racks in the Destiny module.

Because of the sheer complexity of the work planned to this point, Engelauf has included a possible third spacewalk in the crew's flight plan to handle any unfinished business. If the spacewalk is required, it would be carried out on flight day 8, the day after the loaded checkout of the SSRMS.

If a third spacewalk is not required, however, the crews will instead focus on continuing to unload Raffaello and carrying out additional tests of the new robot arm.

The arm must be fully operational before the next station assembly mission in June to deliver the facility's main airlock. The shuttle arm does not have a long enough reach to mount the airlock on Unity's starboard hatch.

Animation shows the station's arm raising the airlock out of shuttle Atlantis' payload bay during the STS-104 mission planned for June. Photo: Spaceflight Now/NASA TV

"Every one of these flights is related, so we have got to get that arm fully checked out and functional and ready to provide a 'go' for the 7A airlock installation that is planned for the next shuttle mission," said station flight director John Curry.

So on flight day eight, the crew will run through what amounts to a dry run of the airlock installation procedure to make sure everything works as expected.

"Not everything will be checked out by the end of the shuttle mission, we just prioritize what had to get done for us to say the arm was fully functional and ready to go," Curry said. "After the shuttle has undocked ... we will work what we need to do between the undocking on April 28 and the 7A mission, which is now launching on June 14.

"During that period of time, six weeks or so, we want to completely check out the arm, every system, every string, we've got to do additional camera checkouts, etc. My plan for that period of time is to actually schedule once a week where Jim or Susan can actually do some functional checkouts of the arm and also get some stick time, some crew proficiency time, to operate the arm."

The day after the SSRMS dry run on April 26, Raffaello, now loaded with station trash and discarded equipment, will be detached from Unity's nadir port and re-berthed in Endeavour's cargo bay.

If all goes well, the shuttle will undock the following day - around 11:45 a.m. EDT on April 28 - filming the station with a large-format IMAX camera before departing for good. Landing is targeted for around 9:35 a.m. on April 30.

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