Walz most recently served as director of the National Aeronautics and Space Administration's Advanced Capabilities Division.

"NASA owes a great debt to Carl Walz for his service as an astronaut and the expertise and perspective he has shared with us in the Advanced Capabilities Division," said Doug Cooke, associate administrator for the Exploration Systems Mission Directorate. "The legacy of his leadership will be strongly felt in the next generation of manned space missions."

Walz, a veteran of four space shuttle missions and one International Space Station expedition, spent a total of 231 days in space. He and fellow astronaut Dan Bursch held the U.S. spaceflight endurance record of 196 days in space until April 2007.

His last space mission, ISS Expedition 4, launched aboard space shuttle Endeavour in December 2001.

A retired U.S. Air Force colonel, Walz joined NASA in January 1990 and flew on STS-51 in September 1993, STS-65 in July 1994 and STS-79 in September 1996.

In addition to his space flights, he served in a variety of NASA technical and management positions.