Home›Maneuver Tracker›Close Approaches›USA 81 ⟷ OPS 8364 (DMSP 4)
MediumProximity
Final forecastFinal forecast, made 7 min before the pass.
Closest approach6 Nov 202615:57 UTC
Relative speed14.91 km/sat the closest approach
Altitude774 kmlow Earth orbit
Last confirmed6 Nov15:50 UTC · final forecast

US USA 81 and US OPS 8364 (DMSP 4) were predicted to reach a closest approach of 9.65 km at 2026-11-06 15:57 UTC, at a relative speed of 14.91 km/s. Final forecast, made 7 min before the pass. 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
USA 81Payload
NORAD 21949
CountryUS
Launched1992-04-25
COSPAR1992-023A
Maneuver capableUnknown
NORAD 6787
CountryUS
Launched1973-08-17
COSPAR1973-054A
Maneuver capableUnknown

Where This Happens

Altitude context
DEBRIS BELT 700–1000 KM2006001,0001,5002,000 kmTHIS PASS · 774 KMISS 420Starlink 550

At 774 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

4 predicted passes under 10 km
Pair history · USA 81 ⟷ OPS 8364 (DMSP 4)
2026-11-06 15:579.65 km Final forecast14.91 km/s774 kmShown above
2026-11-06 15:075.04 km Final forecast14.88 km/s791 kmView →
2026-11-06 14:167.68 km Final forecast14.91 km/s774 kmView →
2026-11-06 13:261.58 km Final forecast14.88 km/s791 kmView →

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 Nothing is overwritten: a withdrawn forecast keeps its figure, with the newer check beside it, and the best estimate after the pass is a row of its own.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
6 Nov 08:55 UTC9.65 km Forecast6 Nov 15:57 UTC5 Nov 14:13 UTCRe-check
5 Nov 16:07 UTC9.65 km Forecast6 Nov 15:57 UTC4 Nov 19:46 UTCScreen

These Objects Elsewhere

Other screened approaches · 7 days
2.39 km11-03 03:09 UTC
USA 81OPS 3367 B
2.51 km11-02 17:51 UTC
USA 81NOAA 16 DEB
2.87 km11-05 18:45 UTC
USA 81FENGYUN 1C DEB

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 →