Those periodic bursts of electrical current at times have caused the motor drive to stall, giving rise to concerns that it could completely seize up.

In that case, the huge solar wings -- which stretch 240 feet (73 meters) from tip to tip -- would stick in place, rendering them incapable of tracking the sun.

Consequently, their ability to generate peak electricity would be thwarted, potentially forcing a station crew to shut down critical systems to conserve energy.

What's worse, a motor freeze-up could take place while the giant solar wings were edge-on to the sun, making them all but useless when it comes to generating electricity to power the station.

That, in turn, would seriously hamper the ability to respond to failures in a myriad of outpost systems, increasing odds that a crew might have to abandon ship in certain emergencies.

"If the motor continues to stall... it could eventually stall in the wrong position," said NASA flight director Sally Davis. "And that, in a nutshell, is the concern -- that the solar arrays will be in some position where we cannot generate electricity using them."

A problem since shortly after a $600 million U.S. electric power tower was delivered to the station in December 2000, the elevated motor drive currents have been the subject of an extensive, almost year-long analysis.

NASA and contractor engineers initially thought the bulky motor drive -- a canister-like device that is about the size of a large beer keg -- might have to be swap out in what would amount to a complex spacewalking replacement job.

Station systems would have had to be powered down in a highly choreographed manner, and then there always would be a chance that those same systems for some reason could not be electrically charged up again.

But after months of review, engineers now think the cause of the problem might be extreme temperatures swings the motor drive is exposed to as the station passes between the dark and sunlit sides of the planet.

So plans to replace the motor drive were scrapped for what NASA hopes will be an easier fix -- fastening two custom-fitted thermal blankets and an insulated cap to the barrel-like device.

Once done, engineers will monitor the motor drive for several months, and if the electrical spikes continue, a more difficult spacewalk will be carried out to swap out the part.

"If the performance does not improve," Davis said, "then we will plan a change out on a future mission."

That repair job likely would be done when shuttle astronauts launch on the next station crew rotation mission in May. But Tani and Godwin hope to obviate the need for any additional fix.

Decked out in $12 million U.S. spacesuits, the two spacewalkers will float into Endeavour's cargo bay and then tether themselves to the ship's 50-foot (15-meter) Canadian-built robot arm.

Hanging on to the crane-like device, the pair will be hoisted up toward their work site by shuttle pilot Mark Kelly, who will double as a robot arm operator for the task.

The two astronauts will ride the arm up to the station's so-called Z-1 truss, a piece of metal framework that the U.S. electric power tower, and its giant gold solar arrays, are mounted atop.

Dangling from the end of the arm, Godwin plans to take in the view as Kelly lifts the two spacewalkers as far as the crane will take them.

"We won't have anything to do but ride and look around," she said.

One of NASA's few veteran female spacewalkers, Godwin said she expects the experience to be much different than a previous sortie that kept her within the semi-enclosed confines of a shuttle cargo bay.

"That'll be a real different sensation for me, because I've never been out of the payload bay environment," she said. "I'm kind of anticipating that getting that far out of the bay and up on the (U.S. power tower) is going to feel very different."

Hopping off the shuttle arm and onto the station truss, the astronauts then will climb another 50 feet (15 meters) to their lofty work site, which is located at the base of the U.S. solar arrays. The thermal blankets then will be attached to the motor drive before the spacewalkers carry out a few odd jobs in advance of the planned delivery of a new station truss segment next March.

Among those tasks: Removing a thermal blanket on a communications antenna and securing a solar array support that failed to lock firmly in place when the panels were initially deployed.

Tani, meanwhile, can hardly believe that he was lucky enough to get a spacewalking assignment on his first flight.

It's "quite an honor, and you know, it's one of the most thrilling parts of this mission for me, if you can name one part that's more thrilling than another," he said.

Only the second Japanese-American to fly in space, Tani said he's so attuned to the job at hand that he's afraid he'll miss the chance to take in the view from above.

"I'm a little worried that I'm going to be so concentrated on the task... that I'll sort of miss the opportunity to go out there and take a break and look at around and appreciate the incredible opportunity to be basically my own little satellite out there on the tip of the space station," he said.

But, he added, "I will not mess this up."

His main goal is "to do the job correctly, on time and safely," he said. "But I'm hoping to keep in the back of my head... what a rare and privileged opportunity I will have being there."