If all goes well, the 10-day flight coupled with the mid-July launch of the stations long-delayed, Russian-made living quarters will jump-start a construction project thats been at a standstill now for nearly a year.
"Its time that we get on with building the International Space Station," said Tommy Holloway, the NASA manager in charge of the $60 billion construction project, which some civil engineers compare to building the Great Pyramids of Egypt.
"I think people ought to stop doubting and start believing, because were launching," added Robert Cabana, a NASA astronaut now serving as manager of international operations for the station project.
"Were going to build this space station. Its going to happen. By about this time next year, well have a real space station up there with a laboratory and electrical power and a crew on board, and well be ready to do science while we continue to build it."
Coming on the heels of three late-April launch delays, Atlantis which is fresh off a
will set up a Russian construction boom outside the station.A faulty radio antenna will be replaced, but perhaps most importantly, the spacewalkers will secure a smaller American crane that has been wobbling within its mount since its installation during a shuttle mission last May.
Engineers fear the crane could fall out of its mount when the stations Russian living quarters also known as the Zvezda service module arrives at the outpost after its planned July 12 launch.
"Theres a definite concern that this object could come loose, specifically during the docking of the service module, jeopardizing that operation," said Williams, a shuttle rookie serving as the lead spacewalker on the Atlantis flight. "So that has become our highest priority to go and reseat or secure this crane."
What follows next will be three days of repair work inside the 70,000-pound (31,750 kilogram) station, which now consists of a Russian space tug dubbed Zarya, or "sunrise," and an American docking module named Unity.
Launched in November 1998, the 22-ton Russian tug is outfitted with two 35-foot (10-meter) solar arrays and six nickel-cadmium batteries that provide electricity to run outpost systems. A 496-day warranty on the electrical system, however, expired at the end of March, prompting NASA to send the Atlantis crew up to perform maintenance work on it.
Specifically, the orbital troubleshooters will replace four failed batteries, each of which weigh 180 pounds (81 kilograms) and provide power when the station is on the dark side of Earth.
Four new cooling fans, three fire extinguishers, 10 smoke detectors and an on-board computer also will be set up by the astronauts, and a suspect power distribution box that is part of the stations radio communications system will be replaced.
Last but not least, the astronauts will convert Atlantis into an orbital loading dock, hauling more than 1 ton of supplies and equipment into the station from a shuttle cargo bay storage module.
The gear which includes everything from clothing to computer and medical equipment will be stored aboard the station for its first full-time crew, which now is scheduled to launch to the outpost in late October or November.
While all the mule work is being carried out, Halsell and Horowitz will be gently easing the station up to a higher orbit by periodically firing some of the shuttles 44 nose-and-tail steering jets.
High solar activity and a resulting increase in atmospheric drag currently are causing the station to drop about 1.5 statute miles (2.4 kilometers) every week. Fuel supplies aboard the Zarya space tug, meanwhile, are limited, so the Atlantis crew will use excess shuttle fuel to boost the outpost about 26 statute miles (41.6 kilometers).
"We intend to reboost the station as much as we can with that propellant," said NASA shuttle program manager Ron Dittemore.
"That makes us very happy," Holloway added. "These activities with the shuttle reboost will save us propellant in the [Zarya] that could be very important to us."
Once all their work is done, the crew which also includes U.S. astronauts Mary Ellen Weber, Susan Helms and Russian colleague Yuri Usachev will close hatches between the shuttle and the outpost and pull away from the station.
Then, armed with still and video cameras, the crew will fly a giant loop or two around the station photographing the outpost from all angles before heading off on a two-day trip back to Earth. Their multimillion-mile voyage is to be capped with a 2:19 a.m. EDT (06:19 GMT) May 29 landing back at KSCs shuttle runway.
Still to come: Another 39 U.S. shuttle and eight Russian rocket missions and dozens of Russian refueling and resupply flights that will be needed to raise the station, which eventually will span an area in space almost as large as two American football fields.
As it stands now, the construction job considered the most complicated ever to be undertaken in space will take another four to five years to complete.
But Holloway and others say the finished product will be well worth the wait.
The 480-ton station "will provide world-class research capability, opportunities for discovery and progress in human spaceflight that our minds have not imagined," Holloway said.
"The International Space Station will also provide the bridge to a future that will enable human exploration of our solar system and perhaps even beyond."
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