CERTIFICATE OF RE-ENTRYOrbital Register™ · by Orbital Radar™
Entry no.
1981-0636
HCMM
HCMM (NORAD 10818) re-entered Earth’s atmosphere on 22 December 1981, after 3 years, 7 months in orbit.
Official date
NORAD number
10818
International designator
1978-041A
Object type
Spacecraft
Country
United States
Launched
26 Apr 1978Vandenberg
Re-entered (UTC)
22 Dec 1981UTC calendar day
Time in orbit
3 years, 7 months1,336 days
How it ended
Re-entered (natural decay)
Latitude range
82.4°N to 82.4°SFinal inclination 97.6°
Mass
135 kg
Operator
GSFC
Built by
Boeing/Kent
Bus
AEM
Programme
Explorer AEM
Where it came down
Latitude band its orbit allowedExact position not recorded
No position was recorded for this re-entry. Its final orbit, inclined at 97.6°, allowed a re-entry anywhere between 82.4°N and 82.4°S.
Life in orbit
3 years, 7 monthsHCMM’s lowest and highest points above Earth, week by week, from its tracking history.
Also ended on 22 Dec 1981
1 entryFrom the same launch
1978-041
Entered in the Orbital Register™, founding volume, September 2026.
Record version 1 · No corrections · orbitalradar.com/register/1981-0636
© 2026 Orbital Radar. Cite this entry by its number; the register itself may not be copied.
Record version 1 · No corrections · orbitalradar.com/register/1981-0636
© 2026 Orbital Radar. Cite this entry by its number; the register itself may not be copied.