The perturbed motion of 24-hour satellites due to equatorial ellipticity

The perturbed motion of satellites in 24-hour orbits having small eccentricities and inclination angles was analyzed by Blitzer et al. [1962]. Four positions of equilibrium were shown to exist, symmetrically situated on the extensions of the principal axes of the equatorial ellipse. The longitudes of the minor axis were found to be stable equilibrum points; those of the major axis, unstable, or more precisely, saddle points. Analytical results, valid for motion in the neighborhood of the stable points, showed the presence of diurnal and long-period (2 to 3 years) oscillations in radius and longitude.