Technical
Ephemeris
A table or function giving a spacecraft's predicted position and velocity over time, used for tracking, communications scheduling, and collision avoidance.
An ephemeris provides the position (and usually velocity) of a space object as a function of time, either as a series of state vectors or as parameters from which they can be computed.
Operators share ephemerides to support conjunction assessment and space traffic coordination, and ground stations use them to point antennas and schedule passes. The quality of an ephemeris — its accuracy and freshness — directly affects the reliability of collision predictions.