Capricorn One (1977)

Charles Brubaker is the astronaut leading NASA's first manned mission to Mars. Seconds before the launch, the entire team is pulled from the capsule and the rocket leaves earth unmanned much to Brubaker's anger. The head of the programme explains that the life support system was faulty and that NASA can't afford the publicity of a scratched mission. The plan is to fake the Mars landing and keep the astronauts at a remote base until the mission is over, but then investigative journalist Robert Caulfield starts to suspect something.