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Issue 8, Volume 2, August 2007
Print ISSN: 1991-8747
E-ISSN: 2224-3429







Title of the Paper: Analytic Solution of Nadir Attitude Pointing for LEO Microsatellite


Authors: A.M. SI Mohammed, M. Benyettou, A. Boudjemai H. Benzeniar, Y. Hashida, M.N. Sweeting

Abstract: An Analytic solution of Nadir attitude pointing equation of gravity gradient satellite stabilised is presented. The attitude equation is Euler linearised equation for near Nadir pointing axially symmetric satellite including only gravity gradient torque and assuming other torques such as magnetic torque, aerodynamic torque, solar radiation pressure torque and controller are constants. The obtained analytical solution was compared to numerical solution of satellite attitude equation.

Keywords: LEO, Microsatellite, Alsat-1, Analytic, Nadir, Attitude, Simulation.

Title of the Paper: Yaw Phase Mode Attitude Control Using Z Wheel for LEO Microsatellite


Authors: A.M. Si Mohammed, M. Benyettou, A. Boudjemai, Y. Hashida, M.N. Sweeting

Abstract: A control system is proposed for a low Earth orbit gravity gradient stabilised microsatellite using Z wheel. The microsatellite is 3-axis stabilized using a yaw reaction wheel, with dual redundant 3-axis magnetorquers. Two vector magnetometers and four dual sun sensors are carried in order to determine the full attitude. The attitude was estimated using an Euler angles (small libration version) on based extended Kalman filter (EKF). After the satellite has been detumbled and deploy the gravity gradient boom, in order to have the accurate Nadir pointing we will use the Z zero-bias mode controller. The Z momentum wheel will be damped by the magnetorquers. This paper describes the attitude determination and control system design of LEO microsatellite using Z reaction wheel for yaw phase mode control.

Keywords: Modelling, Simulation, Microsatellite, LEO, Attitude, Yaw, Control, Z Wheel, Magnetorquer.

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