Project Vanguard was a program managed by the United States Navy Naval Research Laboratory (NRL), which intended to launch the first artificial satellite into low Earth orbit using a Vanguard rocket. as the launch vehicle from Cape Canaveral Missile Annex, Florida.
In response to the launch of Sputnik 1 on 4 October 1957, the U.S. restarted the Explorer program, which had been proposed earlier by the Army Ballistic Missile Agency (ABMA). Privately, however, the Central Intelligence Agency (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 1 February 1958 (UTC). Before work was completed, however, the Soviet Union launched a second satellite, Sputnik 2, on 3 November 1957. Meanwhile, the spectacular televised failure of Vanguard TV3 on 6 December 1957, deepened American dismay over the country's position in the Space Race.
On 17 March 1958, Vanguard 1 became the second artificial satellite successfully placed in a low Earth orbit by the United States. It was the first solar-powered satellite. Just 15.2 cm (6.0 in) in diameter and weighing 1.4 kg (3.1 lb), Vanguard 1 was described by then-Soviet Premier Nikita Khrushchev as, "The grapefruit satellite". Vanguard 1, and the upper stage of its launch vehicle, are the oldest artificial satellites still in space, as Vanguard's predecessors, Sputnik 1, Sputnik 2, and Explorer 1, have decayed from orbit.
In the early 1950s, the American Rocket Society set up an ad hoc Committee on Space Flight, of which Milton W. Rosen, NRL project manager for the Viking rocket, became chair. Encouraged by conversations between Richard W. Porter of General Electric and Alan T. Waterman, Director of the National Science Foundation (NSF), Rosen on 27 November 1954, completed a report describing the potential value of launching an Earth satellite. The report was submitted to the NSF early in 1955. As part of planning for the International Geophysical Year (1957–1958), the U.S. publicly undertook to place an artificial satellite with a scientific experiment into orbit around the Earth.
Proposals to do this were presented by the United States Air Force (USAF), the United States Army (USA), and the United States Navy (USN). 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 launch vehicle, which did not yet exist. The Navy proposed designing a rocket system based on the Viking and Aerobee rocket systems.
The Air Force proposal was not seriously considered, as Atlas development was years behind the other vehicles. Among other limitations, the Army submission focused on the launch vehicle, while a payload was assumed to become available from the Jet Propulsion Laboratory (JPL), and the network of ground tracking stations was assumed to be a Navy project. The Navy proposal detailed all three aspects of the mission.
Despite being overshadowed by Sputnik 1, 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, density of air, 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.
The Vanguard "Satellite Launch Vehicle", a term invented for the operational SLV rockets as opposed to the Test Vehicle TV versions, was a much smaller and lighter launcher than the Redstone-based Jupiter-C/Juno 1 rocket which launched the Explorer satellites, or the immense R-7 that the Soviets used to launch the early Sputniks.
The Vanguard 1 program introduced much of the technology that has since been applied in later U.S. satellite programs, from rocket launching to satellite tracking. For example, it validated in flight that solar cells could be used for several years to power radio transmitters. Vanguard's solar cells operated for about seven years, while conventional batteries used to power another on-board transmitter lasted only 20 days.
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 of Earth on satellite orbits. Vanguard 1 marked its 50th year in space on 17 March 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 (10.6 billion kilometres), the distance from Earth to beyond the dwarf planet Pluto and halfway back. Original estimates had the orbit lasting for 2,000 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 about 240 years.
The first Vanguard flight, a successful suborbital test of the Vanguard TV0 single-stage vehicle, was launched on 8 December 1956. On 1 May 1957, the two-stage test vehicle TV1 was successfully launched. Vanguard TV2, another successful suborbital test, was launched 23 October 1957.
The Vanguard rocket launched three satellites out of eleven launch attempts: