Pioneer 3
Pioneer 3 — a tiny Army/JPL cone probe (6 December 1958) meant to fly past the Moon. A premature engine cutoff left it short of escape; it reached 102,000 km and fell back after 38 hours. But on the way its Geiger counters revealed a SECOND Van Allen radiation belt — its lasting discovery. (Its arc is shown representatively.)
Key facts
Mission & specifications
Mission
- Operator
- NASA / JPL
- Launched
- December 6, 1958
- Status
- Completed
Trajectory
- Distance from the Sun
- 1.01 AU
- Distance from Earth
- 18,738 km
- Distance from Venus
- 0.601 AU
Mission
Pioneer 3 was a cone barely larger than a household bucket, built by the Army's rocket team and JPL and weighing under six kilograms, yet it made a discovery that outlived its failure. Launched on 6 December 1958 to fly past the Moon, it was let down by its rocket: the first stage shut down a fraction early, leaving it short of escape velocity. It climbed to about 102,000 kilometres, missed the Moon entirely, and fell back to burn up over Africa after thirty-eight hours. But its two Geiger counters were working the whole way up and down, and in their data scientists found something new — a second belt of trapped radiation beyond the one Explorer 1 had found earlier that year. The discovery of this outer Van Allen belt was Pioneer 3's real legacy, a genuine scientific first wrung from a failed lunar shot.
- 1958Aimed past the MoonLaunch
A tiny Army/JPL cone probe launches toward a lunar flyby.
- 1958A second radiation beltMilestone
Its Geiger counters reveal a second Van Allen belt — a real discovery from a failed lunar shot.
- 1958Re-entry over AfricaMission end
Short of escape velocity, it reaches ~102,000 km and falls back after 38 hours.
Images
Images from open archives · credit shown per image