His two space shuttle flights include the first Spacelab mission on board Columbia in November 1983. Parker was selected as a scientist-astronaut in 1967, and held several posts with NASA before being appointed director of the NASA Management Office at the Jet Propulsion Laboratory in 1997. He served as director of the NASA Management Office at the Jet Propulsion Laboratory, Pasadena, California, from August 1997 to August 2005, when he retired.