“…The OEs of an orbit are the following:
is the semimajor axis,
is the eccentricity,
is the inclination,
is the right ascension of the ascending node,
argument of the periapsis,
is the true anomaly (see Reference
39(section 5.3) for their formal definition). The spacecraft traveling on the orbit is subject to external forces, which typically include the thruster force and different types of perturbations.…”