Vanguard I celebrated
its 50th birthday this year as both the first solar-powered satellite and the
oldest artificial satellite still orbiting Earth.
The
satellite has traveled 196,990 revolutions of the Earth or 5.7 billion nautical
miles in the past 50 years, equivalent to the distance from the Earth to beyond
the planet Pluto and halfway back.
The United States launched Vanguard I on March 17, 1958, from Cape Canaveral, Florida, as part of the opening salvoes in the Space Race. The
Soviets had earlier launched Sputniks I and II, while the U.S. had managed to get Explorer I into orbit.
The
3-pound, 6-inch-diameter Vanguard I is small compared with the 200-pound
Sputnik I launched by the Soviets, and earned the nickname "the
grapefruit satellite" from then-Soviet Premier Nikita Krushchev. However,
the satellite has outlasted all its Soviet and U.S. predecessors.
The U.S.
Army, U.S. Air Force and U.S. Navy collaborated to track, build and launch
Vanguard. Official responsibility for the satellite fell to the Naval Research
Laboratory (NRL), which based the design on German V-2 and Viking rockets used
to probe Earth's upper atmosphere.
Vanguard's solar
technology paved the way for other U.S. satellites that have launched since — the
early satellite's solar cells operated for about seven years, while
conventional batteries powering another onboard transmitter lasted just 20
days.
The
satellite fell silent in 1964 after its last solar cells died, but continues to
allow scientists to discover the effects of the sun, moon and atmosphere on
satellite orbits. NRL researchers used many of the lessons learned from the
original Vanguard tracking system to build a Space Surveillance System that can
detect unannounced, radio-silent satellites passing over the U.S.
Scientists
originally estimated that Vanguard would have a life expectancy of about 200
years. Now the estimate stands at 2,000 years, meaning that Vanguard should see
many more anniversaries to come.
advertisement
