first U.S. (United States) space station, launched into Earth orbit on May 14, 1973. Three successive crews of visiting astronauts carried out investigations of the human body's adaptation to the space environment, studied the Sun in unprecedented detail, and undertook pioneering Earth-resources observations.

Skylab was an outcome of the Apollo Applications Program set up by the National Aeronautics and Space Administration (NASA) in 1965 to adapt spacecraft and systems developed for the U.S. Moon-landing program to a variety of scientific missions. As a first step toward establishing a long-term manned platform in space, Skylab made use of a Saturn V Moon rocket, whose third stage was outfitted as a habitat and ready-to-use orbital workshop, and the Command and Service modules of Apollo (Apollo program) spacecraft, which ferried the station's crews and small amounts of supplies. Although limited by its consumable resources in the same way as the Soviet Union's first-generation Salyut stations, Skylab was much roomier and capable of more research. Its main scientific instrument, the Apollo Telescope Mount, incorporated a number of component telescopes and other devices for observing the Sun over a broad range of the electromagnetic spectrum, from visible light through X rays.