* Astronomy

Dafydd Rhys "Dave" Williams (born May 16, 1954) is a Canadian physician and a retired CSA astronaut. He had two spaceflights, both of which were Space Shuttle missions. His first spaceflight, STS-90 in 1998, was a 16-day mission aboard Space Shuttle Columbia dedicated to neuroscience research. His second flight, STS-118 in August 2007, was flown by Space Shuttle Endeavour to the International Space Station. 
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