Mean ecliptic for the date

The mean ecliptic for the date is the perpendicular plane at the mean momentum of the Earth-Moon barycentre in its heliocentric motion. The ecliptic is said to be inertial when the velocity is calculated in a non-rotating reference system and rotational when the velocity is calculated in a rotating reference system. The mean momentum is obtained by removing the terms dependent on mean longitudes of the planets and the arguments of Moon from the true momentum obtained by a theory of secular variations.

Source: www.imcce.fr