The primary job at hand: Connecting power cables that will route electricity to the station from the giant solar wings, which now stretch 240 feet (73 meters) from tip to tip, covering a half-acre in low Earth orbit.

Broadcast on NASA TV, the planned six-hour spacewalk is being carried live on SPACE.com. Both spacewalkers are equipped with lipstick-like helmet-cams, providing viewers with an up-close look at the ongoing electrical work.

The off-the-shelf helmet-cams are near identical to the miniature cameras worn by National Football League referees and mounted in NASCAR racers.

The heart of NASA's new Wireless Video System, the helmet-cams are designed to give crew mates inside Endeavour and NASA ground controllers an eye on work sites that cannot been seen with shuttle cargo bay or robot arm cameras.

"It really is a fantastic situational awareness tool for us now because we can literally see what Joe and Carlos are doing with their hands, and it keeps us informed of their progress," Endeavour astronaut Marc Garneau said Monday.

"The downside of the helmet-cam, though, is that you can't get away with anything," Tanner joked. "I'm not sure I like millions of people looking over my shoulder while I'm working."

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The orbital wiring work is critical to routing electricity from the new solar wings into the station, where it will augment existing but meager power supplies generated by smaller arrays attached to Russian segments of the station.

Electrical supplies now are so sparse that one of three prime modules that make up the station is off limits to its first full-time tenants, who took up residence at the outpost in early November.

Mission Endeavour

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That segment - the $300 million U.S. Unity module - cannot be heated or permanently opened up until the wiring work is completed.

The extra power from the new American-made wings - which are capable of generating enough electricity to run 30 homes - also is a must before NASA and its 15 international partners can expand the growing station.

In fact, the planned mid-January launch of the U.S. Destiny lab - which will be the scientific heart of the station - hinges on the successful completion of the wiring work.

Also on tap during the spacewalk: the repositioning of a key radio communications antenna that was delivered to the station by a visiting shuttle construction crew in October.

Now stowed on the side of a girder-like station truss, the antenna is to be put in place atop the station's new electric power tower, a five-story structure that forms the base for the American solar wings.

A pair of power-tower radiators will be prepared for deployment, and the spacewalkers will inspect loose cables that prevented blankets on one of the new solar wings from stretching completely taut during its deployment Sunday.

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Mission managers still are trying to decide whether the astronauts should try to tighten the slack blanket. The pair might be asked to use a luggage-like strap to pull the cables taut during a spacewalk scheduled to start at 11:51 a.m. EST (16:51 GMT) Thursday.

Expedition One

Look here for the latest news about the first crew to live and work aboard the International Space Station.

The daunting job likely would require Noriega, his arms outstretched like an Olympic gymnast, to hold Tanner up by the feet so the latter could reach a tension bar connected to the limp cables.

"We essentially [would] become a stack of two people to get me high enough to get a tether around the tension bar and pull it down," Tanner said. "It should be exciting of we try it."

As it stands, the station and shuttle crews plan to join together for a welcoming ceremony aboard the international outpost about 9:30 a.m. EST (14:30 GMT) Friday.

Christmas presents, fresh fruit and a small load of station supplies will be delivered to the station crew, which includes U.S. astronaut William Shepherd and his two cosmonaut colleagues, Yuri Gidzenko and Sergei Krikalev.

The two crews will bid adieu Saturday as the shuttle pulls away from the station and heads off on a two-day trip back to Earth. Endeavour and its astronauts remain scheduled to land at Kennedy Space Center at 6:19 p.m. EST (23:19 GMT) Dec. 11.