The practical beginnings of the total American space program had its roots in military space requirements. The first American military service to investigate the potential of satellites was the Navy in 1946. When the Air Force learned of the Navy activities, it asserted its rights to this new area as a logical extension of its air mission. During the late 1940s and 50s, the USAF directed the RAND Corporation to study the feasibility of satellite systems and associated launch vehicles. These studies identified the military missions of weather, communications and reconnaissance. Between 1953 and 1956, the Air Force initiated a "Satellite Component Study" giving it an official designation of Weapons System 117L or WS-117L, issued a system requirement and established a general operational requirement, and finally approved a development plan in 1956. The Air Force was on its way into space. WS-117L was envisioned to be a family of subsystems designed for different missions, including photo reconnaissance and missile warning. By the end of 1959, 117L had become three distinct programs - the Discoverer Program, SAMOS or Satellite and Missile Observation System, and finally MIDAS or Missile Detection Alarm System. The Discoverer Program and SAMOS were to be photo reconnaissance satellites, and MIDAS was for missile warning. In 1958, the Weapons System designation was dropped due to President Eisenhower's stated space policy of "freedom of the skies" and "the peaceful uses of space." Using WS nomenclature might be misinterpreted by the Soviets as a non-peaceful use of space. However, in the end, these three pioneering systems and associated launch/booster systems gave the American military space program its beginnings.
The Discoverer Program officially had 38 launches, but in reality had many more. This program was a cover for the covert, intelligence-gathering reconnaissance satellite called CORONA, which was declassified in 1995. Its aim was to develop a film-return photo reconnaissance satellite using the Thor-Agena launch vehicle combination. There were a total of 134 launches between 1959 and 1972. Of these 134 launches, 102 were considered successful. In the 1970s, there were 8 CORONA missions, also known as KH-4Bs. These CORONA KH-4Bs each had two re-entry vehicles or RVs carrying photographic film, had an average mission life of 19 days, and carried out stereo photography of denied areas. In 1997, the Smithsonian's National Air and Space Museum opened up a display called the "Space Race" which showed a full scale CORONA KH-4B to the general public for the first time. However, the distinction of having the first ever public showing of an NRO system goes to the Schriever Exhibit at the Air Force Space and Missile Museum, Cape Canaveral, Florida in 1996.
At the beginning of the American space program, NASA was given the overall responsibility of developing and operating a weather satellite system that could meet both civilian and military needs. NASA launched these first weather satellites, TIROS 1 and 2 in 1960. However, the NRO believed the TIROS system could not meet the strategic meteorological needs of the CORONA system. The first Director of the NRO (DNRO), Joseph Charyk, pushed for a separate weather satellite, and set up the Defense Meteorological Satellite Program or DMSP. The first DMSP satellite was launched in 1962, and by 1964, four weather satellites were operational, still awaiting the full capability of the NASA system. In 1962, DMSP provided the National Command Authority (NCA) with critical cloud cover information on the Soviet Union and the Caribbean during the Cuban Missile Crisis. In 1965, the NRO gave total management responsibility of the DMSP program over to the Air Force, making the system an official military asset. The USAF has overseen the development of DSMP ever since. These satellites provided critical support to our troops during the Vietnam War, especially during air strike planning phases, saving lives and money. Most initial military satellites systems were designed for strategic use, but the DMSP system was the first spacecraft that both the Air Force and the Navy made tactical use of its weather data, primarily in strike aircraft mission planning. The Navy even put receivers on carriers to receive cloud cover information for its attacks in North and South Vietnam. These receivers have become standard equipment for the Navy since that time. The DMSP system was officially declassified in 1973. These satellites are polar orbiting, sun-synchronous spacecraft, with at least two in orbit at all times.
The DMSP system has gone through nine different design changes or upgrades through its operational lifetime, Blocks 1, 2, 3, 4, 5a, 5b, 5c, 5d-1 and 5d-2 - four during the 1970s. In fact, the last Block 4 satellite, Flight 23, was donated to the Museum of Science and Industry in Chicago, and is on display there. There were a total of 15 DSMP launches from 1970 to 1979, with 14 being successful. The launch vehicle for DSMP in the 70s was the Thor-Burner II and Burner IIA. In the beginning, these military weather satellites were designed to provide day and night visual cloud coverage. Now, other instrumentation now include finer resolution cloud cover sensors, temperature/moisture sounders, aurora detectors, and an infrared sounder. By the 1970s, the Air Force had two readout stations for the DMSP system in the Continental United States in the state of Washington and Maine, which feed this information to the Global Weather Central facility at Offutt Air Force Base in Omaha, Nebraska.