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The first artificial satellite in orbit. Marked the start of the Space Race and the US didn't see it coming. Started a time of competition.
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The coordination of space exploration and other advances. Marked the US commitment exceed the Soviets in space exploration.
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Returned from suborbital flight- faulty flight beforehand. Allowed humans in space afterhand.
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Yuri Gagarin and a Soviet hero. Demonstrated Soviet superiority.
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Mariner 4. Caused a sense of urgency in the US.
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Neil Armstrong and Buzz Aldrin. Apollo 11. Massive US victory.
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Salyut 1. Expanded Soviet achievements.
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Apollo-Soyuz Mission. Symbolized detente and cooperation.