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OSO I

Re-entered 9 Jul 1986

OSO I (NORAD 7970, COSPAR 1975-057A) was a US satellite that re-entered Earth's atmosphere on 9 Jul 1986, launched on 21 Jun 1975 on the OSO I mission. It was operated by GSFC as part of the OSO programme. The spacecraft was built by HSES on the HS-331 bus, with a mass of 1,064 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.

1975
launched
1986
re-entered
11
years on orbit
1,064
kg mass

Lifecycle

Launched21 Jun 1975 · on the OSO I mission
Operational30 Sep 1978 · entered service
Retired30 Sep 1978 · end of operational service
Re-entered9 Jul 1986 · atmospheric re-entry — object destroyed

Specifications

NORAD ID7970
COSPAR1975-057A
TypeSatellite
OperatorGSFC
Country / StateUS
ManufacturerHSES
BusHS-331
Mass1,064 kg
ProgrammeOSO
CategoryAST
OrbitLEO (LLEO/I)
Altitude540 × 556 km
Inclination33.0°

Frequently asked questions

What happened to OSO I?

OSO I re-entered Earth's atmosphere on 9 Jul 1986, ending a mission that began with its launch in 1975. Objects in low orbits are gradually slowed by atmospheric drag until they fall back and burn up on re-entry.

When did OSO I re-enter the atmosphere?

OSO I re-entered on 9 Jul 1986, according to Orbital Radar's historical catalogue records.

Who operated and built OSO I?

OSO I was operated by GSFC and built by HSES (US).

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