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
Operationally Responsive Space Office Station in Florida. A Orbital ATK Minotaur IV rocket lifted SensorSat into low Earth orbit. A second Orion (rocket stage) was used to push SensorSat into equatorial orbit. Its mission is situational awareness, to scan the geosynchronous belt for any new geosynchronous satellites, as well as for space junk that may threaten existing geosynchronous satellites. Operationally Responsive Space Office The Operationally Responsive Space Office (ORS Office) is a joint initiative of several agencies within the United States Department of Defense (DoD). The "stand up" of the office took place 21 May 2007 at Kirtland Air Force Base. The first director