The U.S. Air Force launched the world's first space photo reconnaissance satellites using a rocket like the Thor Agena A on display. These satellites, secretly code-named Corona, took pictures of the Soviet Union's bomber and missile bases during the Cold War. The USAF and the Central Intelligence Agency jointly managed Corona, which was known to the public as the Discoverer research satellite program.
The Thor Agena A launch vehicle combined a Thor ballistic missile (similar to the nuclear-armed version on display in the museum's Missile & Space Gallery, but designated SLV-2 or Space Launch Vehicle-2) with an Agena upper stage. At first, the Agena vehicle was meant to be launched by Atlas boosters, but the 1957 Soviet launch of Sputnik -- the first satellite -- sped up the U.S. Discoverer program. Thor was the first vehicle available to carry Agenas.
Originally, Thor was designed as an intermediate-range nuclear ballistic missile (IRBM) in 1956. It borrowed engine and guidance technology from the developing Atlas program, and Thor IRBMs were operational in Great Britain from 1959 to 1963. Though Thor was created quickly as an interim nuclear deterrent, it later became a very successful satellite launch vehicle. The long-lived Delta rocket series, based on refinements of the original Thor design, operated through the end of the Cold War and beyond.
Thor and Agena vehicles worked together to put satellites into orbit. The Thor first stage launched the Agena and its satellite payload into a low orbit, then the Agena boosted the satellite into its final, higher orbit. The Thor-Agena combination was able to put Corona satellites into elliptical orbits that ranged as far as 1,049 miles and as close as 61 miles to the earth. Like Thor, Agena underwent several changes over its lifetime, and it proved to be one of the most successful U.S. satellite launch vehicles of the Cold War era.
The Discoverer satellites' secret identity as Corona intelligence imaging platforms was closely guarded. As boosters like Thor Agena became operational, satellites gave the United States a new capability to see from space what the USSR and other communist nations were doing. Unlike reconnaissance aircraft, an orbiting satellite placed no crew members in harm's way and was immune to enemy air defenses.
Developing dependable satellite imaging systems, though, was difficult. Not only did the boosters have to place satellites in precise orbits, the satellites' cameras had to function perfectly and the film had to be recovered after the satellites successfully re-entered the atmosphere. On Aug. 19, 1960, following several earlier attempts, Discoverer XIV was the first U.S. reconnaissance satellite to finally return intelligence imagery after successful recovery from orbit. The aircraft that recovered the payload, C-119J (S/N 51-8037) is on display at the museum.
Stage 1 (Thor):
Engine: Rocketdyne* LR-79-7 of 150,000 lbs. thrust
Weight: 109,000 lbs. loaded (102,000 lbs. propellant)
Stage 2 (Agena):
Engine: Bell XLR81-BA-5 of 15,500 lbs. thrust
Weight: 8,400 lbs. (6,400 lbs. propellant)
* In 2005 Rocketdyne became Pratt & Whitney Rocketdyne.
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