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
Transit Research and Attitude Control or destroyed by the Starfish Prime high-altitude nuclear test on July 9, 1962 and subsequent radiation belt.) It is expected to orbit for 800 years at an altitude of about . The first poem to be launched into orbit about the Earth was inscribed on the instrument panel of TRAAC. Entitled "Space Prober" and written by Prof. Thomas G. Bergin of Yale University, it reads in part: Transit Research and Attitude Control The Transit Research and Attitude Control (TRAAC) satellite was launched by the U. S. Navy from Cape Canaveral along with Transit 4B on November 15, 1961. The 109