Apollo spacecraft. Illustration of the Apollo Command/Service Module (CSM) in lunar orbit. Each Apollo mission was crewed by three astronauts, sitting in the Command Module (CM, conical gold section at the front of the CSM). The cylindrical Service Module section contained scientific instruments, propulsion systems, fuel cells and life support systems. Once at the Moon, two astronauts used the Lunar Module to descend to the Moon and return to the CSM, which was piloted by the third astronaut. The CM was then used to re-enter Earth's atmosphere, with the other sections being jettisoned.