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MediumProximity
RussiaCOSMOS 2100NORAD 20804 · launched Sep 1990Military payload
5.45kmPredicted miss distance
RussiaCOSMOS 1577NORAD 15077 · launched Jun 1984Military payload
Final forecastFinal forecast, made 9 min before the pass.
After the passBest estimate, from the orbit data published nearest its time: 5.69 km at 6 Nov 15:59 UTC.
Closest approach6 Nov 202615:59 UTC
Relative speed4.83 km/sat the closest approach
Altitude970 kmlow Earth orbit
Last confirmed6 Nov15:50 UTC · final forecast
Track COSMOS 2100Track COSMOS 1577All approaches
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RU COSMOS 2100 and RU COSMOS 1577 were predicted to reach a closest approach of 5.45 km at 2026-11-06 15:59 UTC, at a relative speed of 4.83 km/s. Final forecast, made 9 min before the pass. Best estimate after the pass, from the orbit data published nearest its time: 5.69 km at 6 Nov 15:59 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 2100Payload
NORAD 20804
CountryCIS
Launched1990-09-14
OrbitLEO · 957 × 1,010 km
COSPAR1990-083A
Maneuver capableUnknown
Profile →Globe →
COSMOS 1577Payload
NORAD 15077
CountryCIS
Launched1984-06-27
OrbitLEO · 954 × 1,005 km
COSPAR1984-067A
Maneuver capableUnknown
Profile →Globe →

Where This Happens

Altitude context
DEBRIS BELT 700–1000 KM2006001,0001,5002,000 kmTHIS PASS · 970 KMISS 420Starlink 550

At 970 km this pass sits inside the most congested band in low Earth orbit, home to the debris left by the 2007 ASAT test and the 2009 collision. 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 2100 ⟷ COSMOS 1577
2026-11-06 15:595.45 km Final forecast · after: 5.69 km4.83 km/s970 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
10 Nov 13:13 UTC5.69 km Best estimate6 Nov 15:59 UTC6 Nov 14:43 UTCBest estimate
6 Nov 08:55 UTC5.45 km Forecast6 Nov 15:59 UTC5 Nov 21:59 UTCRe-check
5 Nov 16:07 UTC5.67 km Forecast6 Nov 15:59 UTC4 Nov 21:32 UTCScreen

These Objects Elsewhere

Other screened approaches · 7 days
2.19 km11-12 23:50 UTC
COSMOS 1577SDA_1667
2.40 km11-08 12:50 UTC
COSMOS 2100COSMOS 1579
2.66 km11-12 07:22 UTC
COSMOS 2061COSMOS 2100

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 →