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Sputnik 1, the first artificial Earth satellite, was launched by the
Soviet Union into low Earth orbit on this day in the International
Geophysical Year, 1957. Sputnik transmitted radio signals for three
weeks before its batteries died, and continued orbiting for another two
more months before re-entering the Earth's atmosphere and burning up.
The satellite was a 58 cm diameter polished metal sphere, with four
external radio antennas to broadcast radio pulses. Its radio signals
at 20 and 40 MHz were easily detectable even by radio amateurs, and
observations of Sputnik 1 provided scientists with valuable
information. The density of the upper atmosphere could be deduced from
its drag on the orbit, and the propagation of its radio signals gave
data about the ionosphere. Sputnik's success triggered the Space
Race, and the beginning of a new era of scientific and tecnological
(and political) developments.
The image above shows a model of the Sputnik satellite on display
at the Astro Space Centre in Moscow.
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