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🛰️ SATELLITE · HISTORICAL RECORD

Explorer 4

Re-entered 23 Oct 1959

Explorer 4 (NORAD 9, COSPAR 1958 EPS) was a US satellite that re-entered Earth's atmosphere on 23 Oct 1959, launched on 26 Jul 1958. It was operated by ABMA / JPLA as part of the Explorer ABMA programme. The spacecraft was built by JPLA on the Explorer bus, with a mass of 12 kg. Like most satellites in low orbits, it was gradually slowed by atmospheric drag until re-entry. Historical record from Orbital Radar's satellite archive, cross-referenced with the live satellite catalogue.

1958
launched
1959
re-entered
1
year on orbit
12
kg mass

Lifecycle

Launched26 Jul 1958
Operational19 Sep 1958 · entered service
Retired19 Sep 1958 · end of operational service
Re-entered23 Oct 1959 · atmospheric re-entry — object destroyed

Specifications

NORAD ID9
COSPAR1958 EPS
TypeSatellite
OperatorABMA / JPLA
Country / StateUS
ManufacturerJPLA
BusExplorer
Mass12 kg
ProgrammeExplorer ABMA
CategorySCI
OrbitLEO (LEO/I)
Altitude258 × 2,233 km
Inclination50.4°

Frequently asked questions

What happened to Explorer 4?

Explorer 4 re-entered Earth's atmosphere on 23 Oct 1959, ending a mission that began with its launch in 1958. Objects in low orbits are gradually slowed by atmospheric drag until they fall back and burn up on re-entry.

When did Explorer 4 re-enter the atmosphere?

Explorer 4 re-entered on 23 Oct 1959, according to Orbital Radar's historical catalogue records.

Who operated and built Explorer 4?

Explorer 4 was operated by ABMA / JPLA and built by JPLA (US).

Historical record from the Orbital Radar satellite archive. Sources & methodology: data sources. Accessed 2026-09-06.