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Explorer 1

Explorer 1 was the first satellite successfully launched by the United States. Built by the Jet Propulsion Laboratory with a cosmic-ray experiment led by James Van Allen, the compact spacecraft measured energetic particles, temperatures, and micrometeorite effects during the International Geophysical Year.

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Identity

Aliases
Explorer ISatellite 1958 Alpha1958-001A
Name
Explorer 1
Slug
explorer-1
Status
completed

Details

Astronauts
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Description
Explorer 1 was the first satellite successfully launched by the United States. Built by the Jet Propulsion Laboratory with a cosmic-ray experiment led by James Van Allen, the compact spacecraft measured energetic particles, temperatures, and micrometeorite effects during the International Geophysical Year.
End Date
1958-05-23
Launch Site
Outcome
Explorer 1 entered Earth orbit and transmitted through May 23, 1958. Periods of unexpectedly low detector counts helped reveal that the instrument was saturating in intense trapped radiation; Explorer 3 data confirmed the belts around Earth that became known as the Van Allen belts.
Program
Explorer
Start Date
1958-01-31
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Creation Time
July 18, 2026 at 18:38:04 UTC
Updated Time
July 18, 2026 at 18:38:04 UTC

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