NASA Project is a collective term for the various projects undertaken by the National Aeronautics and Space Administration (NASA). The most famous of these projects are APOLLO, PROBE, and Skylab. APOLLO was a human spaceflight program that sent the first humans to the Moon in 1969. PROBE was a series of robotic spacecraft launched by NASA to explore the Solar System. Skylab was the first American space station, which orbited Earth from 1973 to 1979.