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
Center for the Advancement of Science in Space to support research that is directed towards improving the lives of the American public. The ISS is a platform for a portfolio of research projects that exploit the microgravity environment, harsh external conditions of Low Earth Orbit (LEO) and radiation exposure. CASIS, through its activities on the ISSNL currently contributes to a space-based economy, serving the academic and industrial research communities by providing access to the International Space Station (ISS). The ISSNL has conducted business in space for the past six years. During that time, it has built intellectual capital and a network of researchers that utilize existing resources on