Washington, March 14 : The Vanguard I satellite, that was launched on March 17, 1958 from Cape Canaveral, Florida, has completed its 50 years in space.
Famous for being the first solar-powered satellite, Vanguard I has the distinction of being the oldest artificial satellite orbiting the earth.
The Vanguard I was launched as part of the United States' participation in the International Geophysical Year - July 1957 to December 1958.
As part of the scientific program for the International Geophysical Year, the Naval Research Laboratory (NRL) was officially delegated the responsibility of placing an artificial satellite with a scientific experiment into orbit around the earth.
NRL developed the launch vehicles; developed and installed the satellite tracking system; and designed, constructed and tested the satellites in a program headed by Dr. John Hagen.
NRL's proposal to conduct Project Vanguard was based on experience gained from extensive use of German V-2 and Viking rockets to probe the earth's upper atmosphere.
Vanguard I is 6 inches in diameter and weighs about 3 pounds. Its small size, compared to the Soviet's 200-pound Sputnik I, caused then-Soviet Premier Nikita Khrushchev to dub it "the grapefruit satellite."
In the 50 years following Vanguard's launch, the 3-pound satellite made more than 196,990 revolutions of the earth and travelled 5.7 billion nautical miles, the distance from earth to beyond the planet Pluto and halfway back.
In that time, it has provided a wealth of information on the size and shape of the earth, and set a number of space records as well.
The successes of Vanguard I set the pattern for a multitude of other space ventures. It also served as a springboard for NRL scientists to launch several series of space probes to study various aspects of radiation phenomena.
Also, Vanguard I introduced much of the technology that has been applied in other U.S. satellite programs.
For example, it proved 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 onboard transmitter lasted only 20 days.
Its other achievements were: it was the first orbiting package to be powered by solar energy, it returned a wealth of information on air density, temperature ranges and micrometeorite impact, it maintained an orbit so stable that cartographers were able to more accurately redrawn maps of islands in the Pacific Ocean, and, it revealed that the earth is slightly pear-shaped rather than round.