The satellite ephemeris provides the position of that satellite, at a given time, in the spherical polar coordinate system of right ascension and declination. This data is updated every three hours.
A single ephemeris is applicable to all signals and frequencies of a specific satellite. With this data the user can compute the Earth-Centered, Earth-Fixed (ECEF) coordinates of the Space Vehicle’s (SV) antenna phase centre position at GST time.
The ephemeris for each Galileo satellite is composed of 16 parameters, which are:
- 6 keplerian parameters
- 6 harmonic coefficients
- 1 orbit inclination rate correction parameter
- 1 LAN rate correction parameter
- 1 mean motion correction parameter
- 1 reference time parameter t0e for the ephemeris data set