OPTIMAL THRUSTER CONFIGURATION FOR A GEOSTATIONARY SATELLITE

Since the lifetime of a satellite is generally limited by the amount of fuel, reducing its fuel consumption is especially important. To reduce geostationary satellite fuel consumption, it is necessary to select a thruster con- guration, which, in addition to satisfying all attitude control system (ACS) requirements (such as producing torques in all directions, and modifying the orbital inclination and radius osets), minimizes fuel consumption during the liquid apogee motor (LAM) maneuver. In this paper, after dynamic modeling, simulation of the satellite control is undertaken in three control laws: the direction cosine matrix, Euler angles and quaternion. All simulations were performed using MATLAB. By comparing these three control schemes, the best control law is selected for use in simulation of the studied congurations. On the other hand, control with thrusters has some complexity because of their inherent characteristics, such as minimum pulse width, valve opening and closing delays, the ability to generate force only in one direction and the uncertainty in the nominal thrust. We have included the thruster specications in the actuator model in our control simulations. Finally, after introduction of requirements for an acceptable conguration, by conducting several simulations, parameters such as fuel consumption and attitude control accuracy for a number of dierent congurations, consisting of eight or six thrusters parallel to the main axes of the satellite, have been computed and compared. In conclusion, congurations with minimum steady state error, with minimum fuel consumption and congurations that minimize fuel consumption and steady state error, together, have been introduced.The results of this paper can be used for determination of the optimum conguration of thrusters in design of the ACS system of geostationary satellites.