MOSCOW - Focused intently on their computer screens, experts at Russia's Mission Control on Tuesday slowly guided the international space station toward a linkup with its control module, the Russian-made Zvezda.
Once the long-delayed station docks with Zvezda, it will be finally ready for its first crew, set to arrive in October. But the space laboratory, a massive 16-nation project headed by the United States, will not be complete for another five years, after more than 40 space flights.
Officials said everything was in working order and that the automatic docking would take place early Wednesday morning, Moscow time. Firing Zvezda's jets several times over the weekend, space controllers brought the 24-ton cylindrical module into a stationary orbit and aligned the rest of the station - currently made up of two components - for a smooth approach.
Shortly after docking, Zvezda's solar arrays will begin tracking the sun, and within a few days, its computers will take full control of maintaining the station's orbit. The piece is crucial for the station's immediate future, providing living quarters and steering controls and distributing electricity.
Although the docking should be a routine procedure, Russia is taking extra precautions with Zvezda, which means ''star'' in Russian. If anything goes awry, two Russian cosmonauts will go into space to do the job manually.
But that scenario is one Russia desperately wants to avoid. The manual docking system the cosmonauts would use is the same one used in a 1997 test aboard the Mir space station, when a cargo ship went astray and collided with the orbiter, puncturing the hull.
Zvezda's flawless launch on July 12 was a relief for both Russian and American space officials, who called it a major success for American-Russian space partnership. Since the launch, Zvezda's systems have been tested several times and ground controllers performed a simulated docking.
After two years of delays and some $3 billion in cost overruns because of problems on the Russian side, questions had arisen about Moscow's reliability as a partner, particularly since Zvezda was the first module to be built solely by the Russians.
Some members of the U.S. Congress are questioning whether to fund NASA's spending projections on the $60 billion project, particularly after the failed launches of two Mars missions last year. But they expressed cautious optimism about the Zvezda launch.
A failed docking would be a major setback for the new station and could delay work on it for at least two more years, if not call the entire mission into doubt.
The station is now made up of the Zarya module, built by Russia with U.S. funds and launched in November 1998, and the NASA-built Unity connecting chamber, launched in December 1998. The next major piece to be added is the U.S.-built Destiny science module, the center of the station's research activity, due to be launched in January.
As the station expands, many of Zvezda's functions will be taken over by other components, but it will remain the heart of the Russian segments. Once the space station is complete, it will weigh about one million pounds and have six laboratories.
Russia has also been criticized for keeping the Mir station in orbit, though Russian space officials maintain the 14-year-old station is still useful. The Netherlands-based MirCorp, which runs Mir, announced earlier this month that the station would be permanently manned beginning early next year, including visits by ''space tourists.''