<h2>AAS 97-124</h2>
<h2>REDUCING THE GEOPOTENTIAL TESSERAL HARMONIC EFFECTS ON  AUTONOMOUS LONGITUDE DRIFT CONTROL OF SUN-SYNCHCRONOUS  SATELLITES                       </h2>
<h4> V. Orlando and H. K. Kuga, INPE-Instituto Nacional de Pesquisas Espaciais, Brazil                                                                                        </h4>
<h2> Abstract </h2>
 Within a cooperation between INPE and CNES (France), a study of a method of  autonomous longitude phase drift control was simulated and applied to phased  orbits.  The paper deals with the reduction of oscillations imposed by tesseral  harmonics on the observations of longitude phase drift rate, in order to improve  autonomous orbit control procedures.  We started from a revised issue of the  Ustinov's theory for near circular orbits.  The full equations for the tesseral  harmonics perturbations on the semi-major axis and inclination have given an  approximation for low altitude, near zero eccentricity and near polar phased orbits.