Any of a series of Earth-orbiting spacecraft whose launching by the Soviet Union inaugurated the space age. Sputnik 1, the world’s first artificial satellite (October 1957), remained in orbit until early 1958, when it reentered Earth’s atmosphere and burned up. Sputnik 2 carried a dog, Laika, the first living creature to orbit Earth; since Sputnik 2 was not designed to sustain life, Laika did not survive the flight. Eight more missions with similar satellites carried out experiments on various animals to test life-support systems and reentry procedures and to furnish data on space temperatures, pressures, particles, radiation, and magnetic fields.
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