|M.Sc Student||Evgeney Koretsky|
|Subject||Cluster-keeping with Differential Solar Radiation Pressure|
and Differential Drag for Highly Elliptical Orbits
|Department||Department of Aerospace Engineering||Supervisor||Full Professor Gurfil Pinchas|
Solar radiation pressure (SRP) is caused by photons
transferring their momentum to
the satellite. The magnitudes of atmospheric drag and SRP are similar for spacecraft
in circular orbits at altitudes of 700 to 900 km, depending on their ballistic coefficients. SRP tends to oscillate the eccentricity of the orbit, while atmospheric drag tends to only decrease it. In the present research, feedback control laws aimed at keeping a cluster of satellites within bounded distances are derived. Differential accelerations are obtained based on cross section area manipulation with respect to the drag and SRP directions. By the derivation of a semi-analytical solution for the orbital dynamics that includes SRP and drag, we present several improvements to existing cluster keeping control laws. Among these improvements is a threshold function, which reduces the number of attitude maneuvers required for changing the cross-sectional area, thus reducing the number of dedicated maneuvers needed for cluster keeping. The feedback is based on differential mean semi-major axis and differential mean argument of latitude, which are obtained from the Brouwer transformation, designed as an algebraic transformation from mean to osculating elements. Simulations show that the combination of differential drag and differential SRP can maintain a cluster of satellites within bounded distances on highly elliptic orbits, such as geostationary transfer orbits, and on circular Earth orbits.