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| Explorer 3 launch cover from "H. Flick," postmarked at Patrick Air Force Base on March 26, 1958. |
Explorer 3, a U.S. satellite launched on March 26, 1958, was the second successful mission in the Explorer program, nearly identical to Explorer 1 in both design and objectives. Launched by the U.S. Army (Ordnance) as part of the International Geophysical Year (IGY), the satellite entered an eccentric orbit. Its mission was to continue experiments initiated by Explorer 1, carrying instruments including a cosmic ray counter (Geiger-Müller tube) and a micrometeorite detector (wire grid array and acoustic detector). The Explorer missions' discovery of the Van Allen radiation belt was one of the most significant achievements of the IGY.
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| Photo: An illustration depicting the orbital trajectory of Explorer 3 as it circled the Earth. |
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| Explorer 3 "Goldcraft" launch cover, postmarked at Patrick Air Force Base on March 26, 1958. |
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| Photo: An illustration depicting the stages of the Explorer 3 launch. |
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| Explorer 3 "Sarzin" launch cover, postmarked at Port Canaveral on March 26, 1958. |
(Reference from
Explorer 3)
