Donald Pettit, Ph.D., a member of the Expedition Six
backup crew, will replace Donald Thomas, Ph.D., on the future
mission to the International Space Station.

Pettit has been training as backup flight engineer for this
expedition and will join Expedition Commander Kenneth
Bowersox (Capt., USN) and Russian cosmonaut Nikolai Budarin.
The reassignment results from a medical issue that affects
Thomas’ long-duration space flight qualification.

“The demanding nature of long-term space flight requires a
conservative approach to crew health issues, especially this
early in the program,” said Astronaut Office Chief, Charlie
Precourt. “We have had to make such adjustments before; this
again demonstrates the value of training backup space station
crewmembers in parallel with the prime crews.”

NASA selected Pettit in April 1996. He’s a chemical engineer
and served as a staff scientist at Los Alamos National
Laboratory in New Mexico before joining the astronaut corps.

Selected by NASA in January 1990, Thomas became an astronaut
in July 1991. He’s a veteran of four space shuttle flights
and has logged more than 1,040 hours in space.

For additional information about Pettit and Thomas, visit the
astronaut biography Web site at: