Apollo spacecraft in orbit. Computer illustration of a view across the surface of the Moon towards an Apollo Command/Service Module (CSM) and the Earth on the horizon. Each Apollo mission was crewed by three astronauts, sitting in the Command Module (CM, conical section of the CSM). The Service Module (SM) section contained fuel and batteries. Once at the Moon, two astronauts used the Lunar Module (not shown) 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 the Earth's atmosphere, with the other sections being jettisoned.