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| Explorer 3 launch cover with H.Flick cachet. |
Explorer 3 was a US satellite launched on March 26, 1958. It was the second successful launch in the Explorer program, and was nearly identical to the US Explorer 1 in its design and mission. Explorer 3 was launched in conjunction with the International Geophysical Year (IGY) by the US Army (Ordnance) into an eccentric orbit. The objective of this spacecraft was a continuation of experiments started with Explorer 1. The payload consisted of a cosmic ray counter (a Geiger-Müller tube) and a micrometeorite detector (a wire grid array and acoustic detector). The discovery of the Van Allen radiation belt by the Explorer satellites was considered to be one of the outstanding discoveries of the International Geophysical Year.
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| Photo: Explorer 3 orbital path around the Earth. |
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| Explorer 3 launch cover with Goldcraft cachet. |
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| Photo: Stages in Explorer 3 launch. |
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| Explorer 3 launch cover with Sarzin cachet. |
(Reference from
Explorer 3)
