Spacecraft information: COSMOS 991
| Launched | 27 February 1978 |
| Flight ended | – |
| Status | Unknown |
| Launch site | Plesetsk Missile and Space Complex, Russia |
| Owner | Commonwealth of Independent States (former USSR) |
| NORAD ID | 10692 |
| COSPAR ID | 1978-022A |
| Observing |
Current orbital elements
| Inclination | 82.986° |
| Eccentricity | 0.00355 |
| RA ascending node | 15.247 hr |
| Argument perigee | 218.551° |
| Mean anomaly | 252.479° |
| Orbital period | 104.608 min |
| Epoch of osculation | 11 Jul 2026, 12:40 |
Derived Quantities
| Min Altitude | 957.1 km |
| Mean Altitude | 983.2 km |
| Peak Altitude | 1009.3 km |
Launched alongside
SL-8 R/BOrbital History
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