and the first Canadian to operate the robotic Canadarm 2. Selected as an astronaut by the Canadian Space Agency in 1983, he flew with the space shuttle Columbia in October 1992, in charge of Canadian experiments. In 1993 he became a science adviser for the International Space Station, and in 1994 he was named as acting director-general of the Canadian Astronaut Programme. His 2004 flight was postponed following the Columbia tragedy the previous year. In September 2006, MacLean served as a mission specialist on the space shuttle Atlantis and performed a 7-hour EVA—the second Canadian to do so, after Chris Hadfield.

In 1996 MacLean was selected to train as a NASA mission specialist for a future shuttle flight, and was subsequently transferred to the Robotics Branch of NASA's Astronaut Office. In 2008 he was appointed president of the Canadian Space Agency. He resigned from that post in 2013 to pursue a career in the private sector.