Home›Maneuver Tracker›Close Approaches›COSMOS 2129 ⟷ COSMOS 336
HighProximity
RussiaCOSMOS 2129NORAD 21104 · launched Feb 1991Military payload
3.85kmPredicted miss distance
RussiaCOSMOS 336NORAD 4383 · launched Apr 1970Military payload
Final forecastFinal forecast, made 15 min before the pass.
After the passBest estimate, from the orbit data published nearest its time: 3.90 km at 3 Nov 15:41 UTC.
Closest approach3 Nov 202615:41 UTC
Relative speed13.41 km/sat the closest approach
Altitude1,475 kmlow Earth orbit
Last confirmed3 Nov15:27 UTC · final forecast
Track COSMOS 2129Track COSMOS 336All approaches
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RU COSMOS 2129 and RU COSMOS 336 were predicted to reach a closest approach of 3.85 km at 2026-11-03 15:41 UTC, at a relative speed of 13.41 km/s. Final forecast, made 15 min before the pass. Best estimate after the pass, from the orbit data published nearest its time: 3.90 km at 3 Nov 15:41 UTC. Miss distance and time of closest approach are computed by propagating the latest published orbital elements for both objects, and each pass is re-checked every 20 minutes as new element sets are published. See the Satellite Maneuver Tracker for the live picture and space situational awareness for context.

Why it mattersBoth objects are catalogued as payloads. Screening continues as new element sets arrive; operators act on their own conjunction data.

The Two Objects

Dossiers from the satellite directory
COSMOS 2129Payload
NORAD 21104
CountryCIS
Launched1991-02-12
OrbitLEO · 1,430 × 1,468 km
COSPAR1991-009E
Maneuver capableUnknown
Profile →Globe →
COSMOS 336Payload
NORAD 4383
CountryCIS
Launched1970-04-25
OrbitLEO · 1,462 × 1,486 km
COSPAR1970-036A
Maneuver capableUnknown
Profile →Globe →

Where This Happens

Altitude context
DEBRIS BELT 700–1000 KM2006001,0001,5002,000 kmTHIS PASS · 1475 KMISS 420Starlink 550

At 1475 km this pass sits in low Earth orbit. Objects here stay up for decades: there is too little atmospheric drag to clean the band naturally. Why crowded bands matter →

History Between This Pair

1 predicted pass under 10 km
Pair history · COSMOS 2129 ⟷ COSMOS 336
2026-11-03 15:413.85 km Final forecast13.41 km/s1,475 kmShown above

Repeat encounters are common for objects in near-intersecting orbital planes. Each pass is re-screened as fresh element sets arrive; "Final forecast" means the screening still predicted it within 45 minutes of its time, "Not re-confirmed" means later screening stopped finding it.

Forecast Record

Every figure published for the pass shown above, newest first. Nothing is overwritten: a withdrawn forecast keeps its figure, with the newer check beside it, and the best estimate after the pass is a row of its own.
Computed · figure · predicted time · orbit data · by
7 Nov 01:54 UTC3.90 km Best estimate3 Nov 15:41 UTC3 Nov 14:51 UTCBest estimate
3 Nov 09:13 UTC3.85 km Forecast3 Nov 15:41 UTC2 Nov 21:16 UTCRe-check
2 Nov 21:35 UTC3.84 km Forecast3 Nov 15:41 UTC2 Nov 11:13 UTCRe-check
2 Nov 16:35 UTC3.83 km Forecast3 Nov 15:41 UTC2 Nov 03:38 UTCRe-check
2 Nov 16:15 UTC5.69 km Forecast3 Nov 15:41 UTC2 Nov 03:38 UTCScreen

These Objects Elsewhere

Other screened approaches · 7 days
2.58 km11-04 05:42 UTC
COSMOS 2129SL-14 R/B
3.49 km11-03 11:28 UTC
COSMOS 2468COSMOS 336
4.04 km11-08 17:48 UTC
COSMOS 2129COSMOS 1723

How These Numbers Are Computed

Miss distance and TCA come from propagating the latest published orbital elements for both objects and searching for the minimum separation over the screening window. Element sets carry kilometre-scale uncertainty, so figures here describe a close pass, not a collision prediction; a change in either object's published elements re-computes the pass automatically. What is a conjunction? → How conjunction assessment works →