ephemeris

Ephemeris is previously calculated position data of astronomical celestial bodies and satellites.

Insatellite navigation, not only the current position data of the satellites and the satellite orbits are transmitted, but also prediction data about the future satellite positions. This position prediction data about the exact satellite position at a certain time is called ephemeris. They are used, among other things, as control signals for the precise control of large satellite antennas. Also in the GPS system and in MEO and LEO satellites with relatively fast orbits.