U.S. space exploration history on U.S. stamps also the only space station NASA launched alone. The 100-ton space station was in Earth's orbit from 1973 to 1979 and it was visited by crews three times in 1973 and 1974. Circling 50 degrees north and south of the equator at an altitude of , Skylab had an orbital period of 93 minutes. There were a plethora of UV astronomy experiments done during the Skylab lifetime, as well as detailed X-ray studies of the Sun. The station was active until July 11, 1979, when it fell out of orbit. The 10-cent Skylab commemorative stamp first day of release took
Space Station Freedom of the Space Station "Freedom". Following the presidential announcement, NASA began a set of studies to determine the potential uses for the space station, both in research and in industry, in the U.S. or overseas. This led to the creation of a database of thousands of possible missions and payloads; studies were also carried out with a view to supporting potential planetary missions, as well as those in low Earth orbit. Several Space Shuttle missions in the 1980s and early 1990s included spacewalks to demonstrate and test space station construction techniques. After the establishment of the initial baseline design, the