"Its a magnificent ballet -- and its a very slow-moving ballet," said NASA astronaut Jim Halsell, who docked shuttle Atlantis at the outpost in May.

"I think people sometimes think that rendezvous is a maneuver where you zoom spacecraft right up next to each other and you stop and you dock. And its not," he said.

"You approach very, very slowly to cover for any malfunctions that might happen. In this particular instance, they will fly very gracefully all the way around the station, and it gives you the opportunity to really absorb the beauty of the whole thing."

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Thundering beginning

Discovery and its crew -- which includes six American astronauts and a Japanese mission specialist -- set sail for the station at 7:17 p.m. EDT (23:17 GMT) Wednesday as the outpost flew high above the Indian Ocean due south of the Bay of Bengal.

The 100th Space Shuttle launch thunders from pad 39A at the Kennedy Space Center as Discovery blasts off Wednesday on STS-92, a mission to the International Space Station.

Since then, the astronauts have been conducting periodic firings of the shuttles on-board thrusters in what amounts to a two-day game of orbital catch-up.

Trailing the station by some 6,325 statute miles (10,120 kilometers) early today, the astronauts are closing in on the station at a rate of about 667 miles (1,067 kilometers) with every spin around the globe.

The last leg of the rendezvous will kick off about 10:09 a.m. EDT (14:09 GMT) Friday as shuttle skipper Brian Duffy starts guiding Discovery toward the station from a point about 8 miles (13 kilometers) behind and below the station.

A former military test pilot, Duffy then will fly a giant loop around to the top of the station as the two orbiting spacecraft are flying in formation high above Russian ground stations in an effort to maintain constant air-to-ground communications.

"The timing is very important," Duffy said in an interview before Discoverys launch. "We want to be docking with the station while were over a Russian ground site. So being in the right place at the right time with everything ready to go will be a bit of a challenge."

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Construction continues

The linkup with the station will set the stage for a six-day flurry of construction work at the outpost.

The Discovery crew plans to mount a new shuttle docking port and the first piece of the stations girder-like metal backbone to the growing complex, which now is made up of three permanent sections.

A quartet of daunting spacewalks also are planned to wire up the new station additions.

The six-man, one-woman crew, meanwhile, already is preparing for the onslaught of construction work. The astronauts early today set out to check out a trio of $12 million spacesuits and the shuttles 50-foot (15-meter) robot arm.

Japanese astronaut Koichi Wakata will use the Canadian-built construction crane to pluck the new station parts from shuttle cargo bay cradles and then mount them atop the outpost.

The crew also will spend a day inside the station, finishing electrical hookups to the truss and delivering supplies for the outposts first full-time tenants, who are due to take up residence at the station in early November.

And if all goes well, Discovery will depart the station October 20 and then head for a 2:10 p.m. EDT (18:10 GMT) October 22 landing at KSC.