The International Space Station's 15th expedition team has assumed responsibility for the vessel as the crew that includes billionaire space tourist Charles Simonyi prepares to return to Earth a day later than scheduled.

The U.S. National Aeronautics and Space Administration said Wednesday the Russian Soyuz spacecraft that is to carry Simonyi, commander Michael Lopez-Alegria and flight engineer Mikhail Tyurin is now slated to return to Earth Saturday.

The landing in Kazakhstan was delayed by a day after the Russian federal space agency, Roscosmos, changed the landing site to one that is farther south to avoid "wet conditions" at the original planned location. They were concerned recovery operations to be conducted by helicopter might be hampered.

The Soyuz capsule is scheduled to begin its descent from orbit at 7:42 a.m. ET Saturday. Video coverage of the return preparations and landing is scheduled to begin at 1:30 a.m. Saturday on NASA Television, which is available on the space agency's website.

Cosmonaut commander Fyodor Yurchikhin is now in charge of the International Space Station. He assumed command during a brief ceremony aboard the vessel at 4:40 p.m. ET Tuesday.Flight engineers Oleg Kotov and Sunita Williams round out the 15th expedition team.

Simonyi, 58, is the fifth paying private space traveller. His 13-day trip is costing him a reported $25 million US. The price tag included physical training and Russian language instruction over the past six months.

Simonyi, who leads his own software company, made his fortune at Microsoft Corp., where he developed and managed some of its most profitable productivity tools, such as Word and Excel.