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Project Vanguard

Project Vanguard was a program managed by the United States Naval Research Laboratory (NRL), which intended to launch the first artificial satellite into Earth orbit using a Vanguard rocket as the launch vehicle from Cape Canaveral Missile Annex, Florida.
In response to the surprise launch of Sputnik 1 on October 4, 1957, the U.S. restarted the Explorer program, which had been proposed earlier by the Army Ballistic Missile Agency (ABMA). Privately, however, the CIA and President Dwight D. Eisenhower were aware of progress being made by the Soviets on Sputnik from secret spy plane imagery. Together with the Jet Propulsion Laboratory (JPL), ABMA built Explorer 1 and launched it on January 31, 1958. Before work was completed, however, the Soviet Union launched a second satellite, Sputnik 2, on November 3, 1957. Meanwhile, the spectacular televised failure of Vanguard TV3 on December 6, 1957 deepened American dismay over the country's position in the Space Race.
Proposals to do this were presented by the United States Air Force (USAF), the United States Army, and the United States Navy. The Army Ballistic Missile Agency (ABMA) under Dr. Wernher von Braun had suggested using a modified Redstone rocket (see: Juno I) while the Air Force had proposed using the Atlas rocket, which did not yet exist. The Navy proposed designing a rocket system based on the Viking and Aerobee rocket systems.
Designated Project Vanguard, the program was placed under Navy management and DoD monitorship. The Naval Research Laboratory (NRL) in Washington was given overall responsibility, while initial funding came from the National Science Foundation. The director was John P. Hagen (1908–1990), an astronomer who in 1958 would become the assistant director of space flight development with the formation of NASA. After a delay due to the NRL changing the shape of the satellite from a conical shape, the initial 1.4 kg spherical Vanguard satellites were built at the NRL, and contained as their payload seven mercury cell batteries in a hermetically sealed container, two tracking radio transmitters, a temperature sensitive crystal, and six clusters of solar cells on the surface of the sphere. The first satellite was called Vanguard TV3.
After the Soviet Union launched Sputnik 2, on November 3, 1957, then Secretary of Defense Neil H. McElroy directed the U.S. Army to use the Juno I and launch a satellite. On January 31, 1958, the U.S. Army launched the Explorer 1 satellite. With the launch of Sputnik 1 and 2 the previous concern, the right of satellite overflight, had become moot: those satellites were launched by an early version of the Soviet R-7 rocket, the basis of the USSR's early ICBMs, and definitely military, as well as roughly 40 times larger than the Vanguard launcher.
Despite being overshadowed by Sputnik, and having to overcome the widespread humiliation of its unsuccessful early attempts, the Vanguard Project eventually met its scientific objectives, providing a wealth of information on the size and shape of the Earth, air density, temperature ranges, and micrometeorite impact. The Vanguard 1 radio continued to transmit until 1964, and tracking data obtained with this satellite revealed that Earth is not quite a perfect sphere: it is slightly pear-shaped, elevated at the North Pole and flattened at the South Pole. It corrected ideas about the atmosphere's density at high altitudes and improved the accuracy of world maps. The Vanguard program was transferred to NASA when that agency was created in mid-1958.
Although Vanguard's solar-powered "voice" became silent in 1964, it continues to serve the scientific community. Ground-based optical tracking of the now-inert Vanguards continues to provide information about the effects of the Sun, Moon and atmosphere on satellite orbits. Vanguard I marked its 50th year in space on March 17, 2008. In the years following its launch, the small satellite has made more than 196,990 revolutions of the earth and traveled 5.7 billion nautical miles, the distance from Earth to beyond the dwarf planet Pluto and halfway back. Original estimates had the orbit lasting for 2000 years, but it was discovered that solar radiation pressure and atmospheric drag during high levels of solar activity produced significant perturbations in the perigee height of the satellite, which caused a significant decrease in its expected lifetime to only about 240 years.