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HighProximity
RussiaCOSMOS 2144NORAD 21300 · launched May 1991Military payload
3.66kmPredicted miss distance
RussiaSL-8 DEBNORAD 1591 · launched Sep 1965Debris
Final forecastFinal forecast, made 14 min before the pass.
After the passBest estimate, from the orbit data published nearest its time: 3.46 km at 9 Nov 06:46 UTC.
Closest approach9 Nov 202606:46 UTC
Relative speed11.44 km/sat the closest approach
Altitude1,407 kmlow Earth orbit
Last confirmed9 Nov06:32 UTC · final forecast
Track COSMOS 2144Track SL-8 DEBAll approaches
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RU COSMOS 2144 and RU SL-8 DEB were predicted to reach a closest approach of 3.66 km at 2026-11-09 06:46 UTC, at a relative speed of 11.44 km/s. Final forecast, made 14 min before the pass. Best estimate after the pass, from the orbit data published nearest its time: 3.46 km at 9 Nov 06:46 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 mattersOne side of this pass cannot maneuver, so any avoidance decision rests with the other operator. Screening continues as new element sets arrive.

The Two Objects

Dossiers from the satellite directory
COSMOS 2144Payload
NORAD 21300
CountryCIS
Launched1991-05-16
OrbitLEO · 1,409 × 1,417 km
COSPAR1991-033B
Maneuver capableUnknown
Profile →Globe →
SL-8 DEBDebris
NORAD 1591
CountryCIS
Launched1965-09-18
OrbitLEO · 1,372 × 1,615 km
COSPAR1965-073H
Maneuver capableNo
Uncontrolled debris fragment tracked by the public catalogue. About space debris →
Profile →Globe →

Where This Happens

Altitude context
DEBRIS BELT 700–1000 KM2006001,0001,5002,000 kmTHIS PASS · 1407 KMISS 420Starlink 550

At 1407 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 2144 ⟷ SL-8 DEB
2026-11-09 06:463.66 km Final forecast · after: 3.46 km11.44 km/s1,407 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
14 Nov 02:02 UTC3.46 km Best estimate9 Nov 06:46 UTC9 Nov 06:30 UTCBest estimate
8 Nov 12:32 UTC3.66 km Forecast9 Nov 06:46 UTC8 Nov 05:46 UTCRe-check
8 Nov 10:37 UTC3.65 km Forecast9 Nov 06:46 UTC7 Nov 22:10 UTCRe-check
8 Nov 10:28 UTC6.20 km Forecast9 Nov 06:46 UTC7 Nov 22:10 UTCScreen

These Objects Elsewhere

Other screened approaches · 7 days
2.27 km11-15 00:52 UTC
COSMOS 2144COSMOS 2356
3.41 km11-08 08:38 UTC
COSMOS 2144OPS 6630 DEB
3.59 km11-12 19:36 UTC
COSMOS 2144GONETS D1 1

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 →