Possibility of using geostationary satellites to study the earth's gravitational field

The motion of geostationary satellites in the earth's gravitational field is discussed, and it is noted that the behavior of the geostationary satellite can be considered as motion in the orbital resonance 1/1. Equatorial earth flattening, characterized by the sectorial harmonic coefficients C22 and S22, is shown to play the determining role in periodic variations of the 24-hour satellite orbit. Results of the determination of low-degree geopotential harmonics are examined, and a comparison is made with existing earth models (SE III and GRIM 2).