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
International Space Station launched in November 2019, and other Russian modules which are planned to be attached to Nauka afterwards. Those modules would be within their useful lives in 2020 or 2024. The report presents a statement from an unnamed Russian engineer that, based on the experience from "Mir", a 30-year life should be possible, except for micrometeorite damage, because the Russian modules have been built with on-orbit refurbishment in mind. According to the Outer Space Treaty, the United States and Russia are legally responsible for all modules they have launched. In ISS planning, NASA examined options including returning the station to Earth