Project Gemini (IPA: /ˈdʒɛmɪni/) was the second United States human spaceflight program to fly. Conducted after the first, Project Mercury, and while the Apollo program was still in development, Gemini was conceived in 1961 and concluded in 1966. The Gemini spacecraft carried a two-astronaut crew. Ten Gemini crews and 16 individual astronauts flew low Earth orbit (LEO) missions during 1965 and 1966.