Stationkeeping of geostationary satellites with simultaneous eccentricity and longitude control

Abstract

Because of increasingly stringent deadband requirements (±0.05°) in conjunction with larger solar radiation perturbations caused by higher area-to-mass ratios on current and future satellites, east/west Stationkeeping has become significantly more complicated. An algorithm that simultaneously controls the mean eccentricity and longitudinal motion of a geostationary satellite placed at any station longitude is developed. Eccentricity control is achieved based upon an expanded version of the sun pointing perigee method to include the long-period luni-solar effects in the eccentricity vector targeting scheme. Simultaneous control of the longitudinal motion is achieved by apportioning the required AV for eccentricity control amongst N maneuvers to maintain longitude within a ±0.05° deadband. Upon completing the Mh maneuver, the satellite begins a period of free drift with starting conditions coinciding with the optimal free-drift cycle initial conditions. Modeling of the sun, Earth, and moon effects on the satellite's motion allows for an arbitrary station longitude (and in particular for longitudes at or near an equilibrium point). A detailed simulation of the spacecraft's operating environment incorporating the maneuver strategy was used to verify the feasibility of the algorithm and to illustrate its robustness in the presence of measurement and execution errors.