Simonyi joined Microsoft in 1981, and led the development of Multiplan, Word and Excel. Multiplan was so successful that Bill Gates once said it brought in enough revenue to keep Microsoft running.

Like others that joined Microsoft in the early days, stock options made Simonyi rich, and he used some of his fortune to become the world's fifth 'space tourist' in early 2007.

Space Adventures, the company that arranges for privately-funded individuals to join Russian space missions, has announced that Simonyi now intends to train with the Soyuz TMA-14 crew.

TMA-14 is scheduled to launch on March 25, 2009. The other two members of the Soyuz crew heading for the International Space Station will be Gennady Padalka and Michael Barratt.

The ISS Expedition 19 crew will also comprise Timothy Kopra, Nicole Stott, Yuri Lonchakov, Frank De Winne and Robert Thirsk, who will fly to the station on subsequent Space Shuttle and Soyuz missions.

It seems likely that Simonyi would return to Earth aboard the STS-128 shuttle mission.

There may not be many more chances for space tourism in the next five or six years unless private spacecraft come into service in that timeframe. Find out why on page two.

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When Simonyi first visited the ISS in 2007, he took a special Cosmonauts' Day dinner comprising a menu selected by his close friend Martha Stewart, who also watched from mission control outside Moscow as the Soyuz capsule docked with the ISS.

It's unlikely Stewart will take such a close interest in Simonyi's next trip, as he is now engaged to Lisa Persdotter with a wedding scheduled for November 22.

The first trip reportedly cost Simonyi $US25 million. Even if he spends even more on his second ride into space, the total is still likely to be less than Simonyi has spent supporting the arts, sciences and education.

"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.

"It is also an excellent example that the marketplace is even larger than previously anticipated because of the potential occurrence of clients who fly on multiple occasions."

However, there may not be too many more opportunities in the near future to travel into space as part of a government-backed mission. Once the Space Shuttles are retired in 2010, all the seats on subsequent Soyuz missions will be needed for official crewmembers.

NASA's four-seat Orion spacecraft is not scheduled to fly to the ISS until 2014, ahead of a Moon mission in 2020.

Space Adventures' sixth client - Richard Garriott - is scheduled to leave Earth for the ISS on October 12.