Program 35

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).

During the 1960s, one of the most important projects that the United States civil space program was involved in dealt with meteorology and weather forecasting. Unbeknownst to many, the U.S. military services were also starting up a weather satellite program. This program, the DMSP, would relay important weather and climate data to the military for more effective operations. From the onset of the DMSP program, knowledge of its existence was limited to "need-to-know" personnel. The United States Congress had assigned a substantial budget towards the civil weather satellite program; if knowledge of a second military program came out, it would have been hard for the military to justify it.

Initial operations of early DMSP systems provided radio return of cloud-cover imagery for planning of U.S. high-resolution photographic reconnaissance and surveillance missions, which utilized film-return systems. DMSP satellites operated in a sun-synchronous orbit; passing over the north and south poles, the satellite would see different strips of the Earth at the same local time each day. The DMSP satellites had periods of roughly 101 minutes, so they would orbit the Earth 14.3 times in 24 hours. This period combined with the sun-synchronous orbit would have the satellite pass over the whole surface of the planet twice a day.

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