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| A Vanguard 1 launch cover from "Goldcraft", postmarked at Patrick Air Force Base with a machine cancel on March 17, 1958. |
Vanguard 1 is a U.S. satellite that became the fourth artificial Earth-orbiting satellite when it was launched on March 17, 1958, after Sputnik 1, Sputnik 2, and Explorer 1. As the first solar-powered satellite, Vanguard 1 was intended to test the launch capabilities of a three-stage launch vehicle as part of Project Vanguard, as well as to study the effects of the space environment on a satellite and its systems in Earth orbit.
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| A Vanguard 1 launch cover from "H.Flick", postmarked at Patrick Air Force Base with a machine cancel on March 17, 1958. |
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| A Vanguard 1 launch cover from "Sarzin", postmarked at Port Canaveral with a hand cancel on March 17, 1958. |
(Reference from
Vanguard 1)
