who holds the Canadian record for total number of space walks. He was a member of the crew on the 16-day Spacelab flight aboard the space shuttle Columbia in April 1998. The mission investigated the effects of microgravity on the brain and nervous system. He was selected as an astronaut by the Canadian Space Agency in 1992. In 1995 he was assigned for training at NASA's Johnson Space Center, and from 1998 to 2002 was director of its Space and Life Sciences Directorate. In August 2007 he flew aboard space shuttle Endeavour to the International Space Station, where he performed three space walks.