A new crew will soon be on its way to the International Space Station in a Russian Soyuz spaceship. A Russian cosmonaut and U.S. astronaut will take off Saturday from Baikonur, Kazakhstan, and are to arrive at the outpost Monday for a six-month stay. Riding with them will be an American space tourist, the third private citizen in space. The mission will support the basic operations of the orbiting research laboratory until U.S. space shuttles fly again.

US astronaut William McArthur, center, Russian cosmonaut Valery Tokarev, right, and US space tourist Gregory Olsen, left, wave after news conference at Baikonur Cosmodrome

U.S. astronaut William McArthur and Russian cosmonaut Valery Tokarev are the space station's newest crew. They will take over from cosmonaut Sergei Krikalev and astronaut John Phillips, who are set to return to Earth on a Soyuz a week after their replacements arrive.

The new team is the twelfth for the station since occupation began in 2000, and the seventh two-man crew. Crew size dropped from three to two after the U.S. space shuttle Columbia disintegrated in 2003. The two-and-a-half year grounding of the shuttle fleet that resulted left no cargo craft big enough to haul the amount of supplies necessary to support three people and the equipment required to continue station construction.

With the recent flight of the shuttle Discovery, the U.S. space agency NASA had hoped to resume regular visits to the outpost and expand the crew size to three later this year. But it grounded the fleet again until sometime next year because Discovery's external fuel tank shed dangerous debris during launch, the same problem that caused Columbia's demise.

Commander McArthur says that means he and cosmonaut Tokarev will be busy just keeping the station running, with little time for experiments.

"Most of our training has assumed we would be a two-person crew," he said. "So we think we're prepared to continue ops [operations] with just the two of us. Just maintaining and operating the station does occupy a significant amount of crew time."

They will have a third crewmember for a brief period. Joining them on the way up to the station is U.S. scientist and entrepreneur Gregory Olsen, the owner of a New Jersey company that makes electronic optical equipment. He paid the Russian space agency $20 million for the opportunity. Mr. Olsen told reporters recently that he will conduct some experiments for the European Space Agency until he returns to Earth with the outgoing station crew.

"My company, Sensors Unlimited, has a sensor on board the ISS that was used in the laser camera," he said. "So I feel like I'm part of it already. I'm just looking forward to getting up into space and enjoying the time I'm up there and coming back and sharing it with a lot of young people in school groups."

The maintenance work that crewmembers McArthur and Tokarev will do in the next six-months will include at least two spacewalks. They might be joined by German astronaut Thomas Reiter late in their sojourn if a shuttle can bring him up during a planned March mission. Mr. McArthur says they all trained together in the United States and Russia and hopes Mr. Reiter can make the journey.

"He is just a tremendous gentleman. Valery and I will be very disappointed if he doesn't join us," he said. "It will be, I think, more like having a family reunion when we get together in space."

But that reunion might not occur. In an internal NASA memorandum that became public, a top shuttle official wrote that recent hurricane damage to NASA facilities and the effort to prevent launch debris from endangering shuttles might delay Thomas Reiter's visit to the station until late in 2006.

An extended shuttle grounding would also mean that the United States would continue relying on Russian Soyuz spacecraft to carry its astronauts to and from the station. But time is running out for NASA to get this service at no cost. A bilateral agreement will run out in April and Russia wants money for the transportation after that. Complicating matters is a five-year-old U.S. law prohibiting such payments unless President Bush confirms that Moscow has not provided Iran with missile or weapons technology. However, relief from the payment ban appears to be on the way. The U.S. Senate recently approved legislation overturning it, but the measure must still be approved by the House of Representatives before it can become law.