HOUSTON--As the crew of NASA's space shuttle Discovery celebrates their safe return to Earth, two astronauts are gearing up for their own launch toward the International Space Station (ISS).

NASA astronaut Bill McArthur and Russian cosmonaut Valery Tokarev are set to ride a Soyuz spacecraft to the station in October on the twelfth expedition to the ISS. McArthur will command ISS Expedition 12, with Tokarev serving as flight engineer. Physicist Gregory Olsen, a paying spaceflight participant whose trip was brokered by the Arlington, Virginia-based space tourism firm Space Adventures, will fly to the ISS along with the Expedition 12 crew.

"We're getting maybe a revitalized space station," McArthur said, adding that Discovery's STS-114 crew hauled tons of unneeded material from the ISS back to Earth when it landed Aug. 9. "I'm thrilled to death with the opportunity to do the things that we hope to do on orbit."

A veteran of three shuttle flights, McArthur said that he and Tokarev hoped to conduct two spacewalks during their mission in addition to their science regime. But the tools and equipment they plan to use are slated to launch aboard the space shuttle Atlantis in September along with European Space Agency astronaut Thomas Reiter.

Reiter's arrival would bring the space station's crew complement back to its full, three-person capacity. But shuttle officials said that Atlantis's STS-121 mission--NASA's second test flight to verify fixes made in response to the 2003 Columbia accident, will not launch until they solve an external tank foam shedding problem seen during Discovery's launch.

"We're very hopeful that Thomas will make it will while we're up there, because we just see that being a tremendous enhancement to the quality of the work we can do on orbit," McArthur said. "And we just think it'll be a lot more fun."

While Tokarev, who flew aboard Discovery during its STS-96 mission in 1999, is slated to spend about six months aboard the ISS, McArthur hopes to stay aboard for about 213 days and return on a future shuttle flight, the NASA astronaut told SPACE.com.

"We've trained together for several years," Tokarev said of himself and McArthur, adding that they trained as backup for several ISS expeditions. "We've got a real friendship and we know each other good enough, not only for [our] flight."

Founder and head of the Princeton, New Jersey-based Sensors Unlimited, Inc., Olsen will be the third paying crewmember to ride a Soyuz into orbit, following the successful flights of Dennis Tito in 2001 and Mark Shuttleworth in 2002 - both brokered by Space Adventures.

Space Adventures and Olsen announced plans for his ISS flight last year, and he had already begun cosmonaut training when an undisclosed medical condition prevented him from continuing. That condition has since been remedied, Olsen said.

"I'm looking forward to getting up there and being weightless," Olsen said, adding that he hopes to perform some science while aboard the ISS. "I'm ready to go and I'm very excited."