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
Commercial use of space launched by Telesat Canada, allowed the Canadian Broadcasting Corporation to reach northern Canada for the first time. Beginning in 1997, Iridium Communications began launching a series of satellites known as the Iridium satellite constellation, which provided the first satellites for direct satellite telephone service. The commercial space transportation industry derives the bulk of its revenue from the launching of satellites into the Earth’s orbit. Commercial launch providers typically place private and government satellites into low Earth orbit (LEO) and geosynchronous Earth orbit (GEO). In 2002, commercial space transportation generated 6.6 billion dollars, which made up 6% of the total gross