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4th of October 2019
Sputnik launch anniversary
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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