Explorer 1

Re-entered 31 Mar 1970

Explorer 1 (NORAD 4, COSPAR 1958 ALP) was a US satellite that re-entered Earth's atmosphere on 31 Mar 1970, launched on 1 Feb 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 8 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

1970

re-entered

years on orbit

kg mass

Lifecycle

Launched1 Feb 1958

Operational1 Apr 1958 · entered service

Retired1 Apr 1958 · end of operational service

Re-entered31 Mar 1970 · atmospheric re-entry — object destroyed

Specifications

NORAD ID4

COSPAR1958 ALP

TypeSatellite

OperatorABMA / JPLA

Country / StateUS

ManufacturerJPLA

BusExplorer

Mass8 kg

ProgrammeExplorer ABMA

CategorySCI

OrbitLEO (LEO/I)

Altitude359 × 2,542 km

Inclination33.2°

Frequently asked questions

What happened to Explorer 1?

Explorer 1 re-entered Earth's atmosphere on 31 Mar 1970, 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 1 re-enter the atmosphere?

Explorer 1 re-entered on 31 Mar 1970, according to Orbital Radar's historical catalogue records.

Who operated and built Explorer 1?

Explorer 1 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.

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