The Defense Meteorological Satellite Program (DMSP) monitors meteorological, oceanographic, and solar-terrestrial physics for the United States Department of Defense. The program is managed by the Air Force Space Command with on-orbit operations provided by the National Oceanic and Atmospheric Administration. The (originally classified) mission of the satellites was revealed in March 1973. They provide cloud cover imagery from polar orbits that are sun-synchronous at nominal altitude of 450 nautical miles (830 km).