The National Aeronautics and Space Administration (NASA) was inaugurated on 1 October 1958 with the intent of conducting a manned space program. NASA took over the rocketry and propulsion work previously performed by the United States Air Force, Navy, and National Advisory Committee for Aeronautics. Unmanned launches began during the International Geophysical Year (1957-58) under Air Force auspices and have continued to the present with a wide variety of payloads, including space science, weather, communications, and earth observation satellites. The manned program progressed through Projects Mercury (1959-63; launches 1961-63), Gemini (1962-67; launches 1965-66), Apollo (1960-72; launches 1968-72), and Skylab (1969-74; launches 1973-74). After a hiatus following the Skylab program, the manned program focused on the Space Shuttle, a reusable spacecraft. The manned program was supported by a number of unmanned exploration vehicles in the Ranger, Lunar Orbiter, and Surveyor series throughout the 1960s, as well as research into a number of related areas.