Apollo spacecraft in lunar orbit. Computer illustration of an Apollo Command/Service Module (CSM) with the Moon in the background. 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.