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Conjunction Events

A conjunction event represents a time where two objects fall within our screening volume at their time of closest approach (TCA).

When the conjunction screening system generates a CDM whose time of closest approach is within 20 minutes of an existing conjunction event, that CDM is associated with that conjunction event. Otherwise, a new conjunction event is created.

Note that close approaches with very low relative velocities (rare in Low-earth orbit) may see their TCA change by > 20 minutes. In this case, multiple conjunction events may be created for the same close approach.

More CDMs may be associated with a conjunction event as operators continue to submit trajectories associated with the objects.

Conjunction Details

Conjunction events may contain multiple "active" CDMs, which contain different estimates for the conjunction geometry and conjunction risk based on different state sources for the trajectories (i.e., operator_ephemeris trajectories submitted by operators vs. spacex_optical trajectories produced by Stargaze). Read more about this in the CDMs docs.

Active CDMs

Relative States Plots​

The conjunction details page in the UI displays the consistency of the predictions for each object reported in successive CDMs. It takes the latest CDM from the conjunction event as the "truth" state, and calculates the objects' states in prior CDMs relative to this "truth" state. Due to changes in each trajectory, the exact TCA reported in each CDM may vary throughout an event. For these plots, the states from all prior CDMs are linearly TCA corrected (propagated along the velocity vector) to the TCA of the "truth" state. These plots help operators understand how the prediction for each object's state at TCA evolves over time.

Hypothetical Trajectories​

Hypothetical trajectory submissions do not generate conjunction events, only CDMs. This prevents confusion by preventing conjunction events from grouping "real" CDMs (generated by definitive trajectories) with CDMs that were only generated for planning/analysis purposes.