Technical
Nodal Precession
The gradual rotation of an orbit's ascending node around the Earth's axis, driven mainly by the J2 perturbation.
Nodal precession is the steady change in the right ascension of the ascending node (RAAN) over time, caused predominantly by the Earth's oblateness (J2). Its rate depends on altitude and inclination.
Sun-synchronous orbits are designed so that the nodal precession exactly matches the Earth's mean motion around the Sun (about one degree per day), keeping the orbital plane at a constant angle to the Sun and a consistent local time at the equator crossing.