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U.S. billionaire Charles Simonyi, top, and Russian cosmonaut Oleg Kotov wave just before the launch of the Soyuz TMA-10 from the Baikonur cosmodrome in Kazakhstan in April. Simonyi is planning a return trip to the International Space Station. ((Sergey Ponomarev/AP))

Software billionaire Charles Simonyi, the fifth private traveller or "space tourist" to visit the International Space Station, is poised to become the first to make a return trip.

Vienna, Va.-based Space Adventures, the company that brokers the trips with Russia's space agency, announced Wednesday the 60-year-old Simonyi intends to train with a Russian crew preparing for a spring mission to the orbiting station.

Simonyi flew aboard a Russian Soyuz spacecraft to the ISS on a 13-day mission in April 2007.

"Having a repeat orbital client demonstrates to the world that participating in a space mission is truly a magnificent and awe-inspiring experience," said Eric Anderson, president and CEO of Space Adventures in a statement.

Simonyi, who who now runs his own company, made his fortune while working at Microsoft, where he developed some of its most profitable programs, such as Word and Excel.

He reportedly paid Space Adventures $25 million US to make the first trip. Space Adventures did not say how much the second trip would cost.

The next civilian scheduled to make a trip aboard a Russian rocket to the space station is video game pioneer Richard Garriott, the son of NASA astronaut Owen Garriott. He is due to fly to the space station on Oct. 12.