Selected by NASA as an astronaut candidate in June 1998, he reported for training in August 1998. Johnson was the class leader for the seventeenth group of astronauts, with 31 U.S. and international members. Johnson was initially assigned as an Astronaut Support Personnel (ASP) responsible for configuring the Orbiter switches prior to launch and strapping astronauts in their seats for launch. More recently he served as the Astronaut Office representative for all technical aspects of orbiter landing and roll out issues. From June 2004 to November 2005, Johnson served as Manager, Launch Integration, for the Space Shuttle program at Kennedy Space Center, Florida. He also served as the Astronaut Office Deputy, Shuttle Branch and Return to Flight Representative.