What is a satellite conjunction?

A conjunction is a predicted close approach between two objects in orbit: two satellites, or a satellite and a piece of debris. Tracking networks propagate every catalogued object forward, and when two paths come within a screening volume (typically a few kilometres) a Conjunction Data Message (CDM) is issued describing the time of closest approach, the predicted miss distance and, where covariance allows, a collision probability.

What miss distance actually matters?

Miss distance alone is a poor guide because position uncertainty can be hundreds of metres to kilometres. Operators act on collision probability (Pc), which combines miss distance with the uncertainty of both objects. The widely used decision line is Pc of 1 in 10,000 (1e-4): above it most operators plan an avoidance maneuver; between 1e-5 and 1e-4 they watch and refine tracking. A 100 m miss with tight covariance can be safer than a 1 km miss with poor tracking.

Who maneuvers, and who decides?

Whichever object is active and maneuverable is expected to move: debris cannot. When both are active satellites, operators coordinate directly or through the 18th/19th Space Defense Squadron and commercial services; large constellations such as Starlink maneuver automatically when Pc exceeds their internal threshold. There is no binding right-of-way rule in orbit, which is why conjunction data being public matters.

Where do these rows come from?

The live table reads the public CDM class on Space-Track.org, the US Space Force catalogue service. SpaceNexus fetches CDMs created in the last seven days with a future time of closest approach every six hours. Space-Track requires a free account; if the fetch credentials are not configured the live table is empty and the page says so rather than showing stand-in data as real.

Satellite Conjunctions

How satellite close approaches are screened and read: what a conjunction data message says, how close is too close, and how likely a collision actually is. For live screening, go to the sources linked below.

Public CDMs on file

not republished (see below)

Red · Orange

–

Pc ≥ 1e-4 · ≥ 1e-5

Next TCA

–

earliest upcoming

Closest miss

–

in the stored feed

Close approaches: Space-Track public CDMs

Space-Track.org cdm_publicOFF

We do not republish Space-Track conjunction data

Space-Track's user agreement allows conjunction data messages to be shared only with an approved Orbital Data Request, which SpaceNexus does not hold. So this table stays empty rather than copying them.

For live screening: Space-Track.org serves CDMs free to registered users, and CelesTrak SOCRATES screens active satellites three times a day for the week ahead.

Try instead:

CelesTrak SOCRATES Space-Track.org Satellite tracker

What this means

A CDM is a warning, not a verdict. Most close approaches resolve as tracking improves and the predicted miss grows; only a small fraction ever cross the maneuver line. The level column here is SpaceNexus's reading of each row: Red collision probability at or above 1e-4 (the common maneuver-decision threshold), Orange at or above 1e-5 (watch and refine), Yellow a predicted miss under 1,000 m with a lower or unreported Pc, and Green everything else.

Debris cannot move, so a satellite-versus-debris conjunction is entirely on the satellite operator. Two active satellites must coordinate; large constellations maneuver automatically at their own internal threshold, which is why so many CDMs involving them never become news.

Reading a conjunction

What is a satellite conjunction?: A conjunction is a predicted close approach between two objects in orbit: two satellites, or a satellite and a piece of debris. Tracking networks propagate every catalogued object forward, and when two paths come within a screening volume (typically a few kilometres) a Conjunction Data Message (CDM) is issued describing the time of closest approach, the predicted miss distance and, where covariance allows, a collision probability.
What miss distance actually matters?: Miss distance alone is a poor guide because position uncertainty can be hundreds of metres to kilometres. Operators act on collision probability (Pc), which combines miss distance with the uncertainty of both objects. The widely used decision line is Pc of 1 in 10,000 (1e-4): above it most operators plan an avoidance maneuver; between 1e-5 and 1e-4 they watch and refine tracking. A 100 m miss with tight covariance can be safer than a 1 km miss with poor tracking.
Who maneuvers, and who decides?: Whichever object is active and maneuverable is expected to move: debris cannot. When both are active satellites, operators coordinate directly or through the 18th/19th Space Defense Squadron and commercial services; large constellations such as Starlink maneuver automatically when Pc exceeds their internal threshold. There is no binding right-of-way rule in orbit, which is why conjunction data being public matters.
Where do these rows come from?: The live table reads the public CDM class on Space-Track.org, the US Space Force catalogue service. SpaceNexus fetches CDMs created in the last seven days with a future time of closest approach every six hours. Space-Track requires a free account; if the fetch credentials are not configured the live table is empty and the page says so rather than showing stand-in data as real.

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SpaceNexus Satellite Conjunctions. https://spacenexus.us/conjunctions (retrieved 2026-10-17).

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We do not republish Space-Track conjunction data