"So, if we're going to run the space station robotic arm properly, it's very important that these cables get routed and connected."

Considered the heart of Canada's contribution to the station project, the 57-foot (17-meter) robot arm is to be hauled up to the outpost by a visiting shuttle crew in mid April. Able to "inch-worm" from work site to work site outside the station, the crane-like device must be put in place and activated before construction of the growing station can continue.

Thomas and fellow astronaut Paul Richards will pick up the wiring work -- which was left undone after a spacewalk Sunday -- during a 6.5-hour excursion that is scheduled to begin at 11:47 p.m. EST Monday (04:47 GMT Tuesday).

The spacewalking partners also plan to place a stowage platform and spare cooling system equipment outside the $1.4 billion U.S. Destiny science laboratory, which was delivered to the outpost last month.

Additionally, Thomas and Richards aim to scale to the top of the 17-story station to fix a metal latching bar that failed to snap firmly in place when a $600 million U.S. electric power tower was erected at the outpost last October.

The hodge-podge of station outfitting and repair work will follow the successful mounting of the Italian moving van Leonardo to a berthing port on the station's Unity module, which is a pressurized passageway that leads to all parts of the outpost.

Wielding the shuttle's 50-foot (15-meter) robot arm, Thomas snatched the 11-ton cargo carrier from a shuttle cargo bay cradle before slowly lifting it toward Unity's nadir, or Earth-facing, port.

A series of motor-driven latches and computer-controlled bolts then snapped shut, forming an airtight seal between the two pressurized modules.

"Just one word for Andy: Outstanding!" German astronaut Gerhard Thiele said from NASA's Mission Control Center in Houston, Texas.

"Thank you, Gerhard," Thomas replied. "We aim to please."

~

Named after famed Italian inventor and artist Leonardo da Vinci, the cylindrical module houses five tons of supplies and equipment for the station's second resident crew, which includes Russian commander Yuri Usachev and U.S. flight engineers Susan Helms and Jim Voss.

Among the gear:

• The station's first scientific research package.

  Known as NASA's Human Research Facility, the refrigerator-sized rack houses experiment apparatus for research into the adverse effect of weightlessness on the human body, scientific work deemed key to preparing for human expeditions to Mars.

• Key space-to-ground communications gear.

  The equipment will enable Usachev and his crew to activate the station's Ku-band communications antenna, which was set up outside the outpost by a spacewalking assembly crew last October.

  Designed to beam back high-quality audio and video through NASA relay satellites, the dish-shaped antenna will replace the comparatively primitive U.S. communications system now onboard the outpost while reducing reliance on widespread Russian ground stations.

• Station robot-arm work stations.

  Once activated, the sophisticated computer work stations will enable outpost crews to control the station's soon-to-be-delivered robot arm from inside the Destiny laboratory.

The 10 astronauts and cosmonauts aboard the joined shuttle-station complex will spend much of the coming week unloading Leonardo, which features a large hatch designed to accommodate hefty outpost science and systems racks.

Other shuttle-borne carriers are linked to the station by tunnels that are too narrow to pass bulky cargoes through.

One of three such moving vans built by the Italian Space Agency at a total cost of $450 million, the Leonardo module also serves a second purpose: It can be filled up with research apparatus, experiment samples, discarded equipment and trash for return trips to Earth.

Some 2,630 pounds (1,183 kilograms) of surplus gear and garbage will be stuffed into the 21-foot (6.4-meter) module before it is stowed back in Discovery's cargo bay for the last leg of the shuttle's 12-day crew exchange mission.

Launched last Thursday aboard Discovery, Usachev, Helms and Voss late this week will replace the outpost's inaugural tenants: U.S. astronaut Bill Shepherd and Russian cosmonauts Yuri Gideznko and Sergei Krikalev.

The so-called Expedition One and Expedition Two crews are in the midst of the first changing of the guard at the international station.

To that end, Usachev and Gidzenko switched ships Saturday, and the station's incoming skipper has been holding detailed briefings with current commander Shepherd ever since.

Voss and Krikalev traded places Monday. Shepherd will join the shuttle crew Tuesday as Helms floats over to the station for a planned four-month tour of duty.

The Expedition Two crew, however, will not take official command of the outpost until hatches between the shuttle and the station swing shut a few hours before Discovery's scheduled departure on Saturday.

The hatch closure will mark the end of a four-and-a-half-month station "shakedown cruise" for Shepherd and his two cosmonaut colleagues. The trio will taxi back to Earth aboard Discovery on March 20, capping a 140-day stay in space.