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Abstract: In this paper, the control system of the first Algerian microsatellite in orbit Alsat-1 is presented. Alsat-1 is a 3-axis stabilised microsatellite, using a pitch momentum wheel and yaw reaction wheel, with dual redundant 3-axis magnetorquers. A gravity gradient boom is employed to provide a high degree of platform stability. Two vector magnetometers and four dual sun sensors are carried in order to determine the attitude. This paper examines the low Earth orbit (LEO) control system requirements and design in the context of a real system, the Surrey Satellite Technology Limited (SSTL) advanced microsatellite platform and puts forward designs for the control system to match the advanced capability of the enhanced microsatellite platform. Numerical results show the effectiveness of the implementation. Comparison with in orbit results is presented to evaluate the performance of the control system during accurate Nadir pointing control. [Copyright &y& Elsevier]

Abstract: This paper describes the various steps of the design and the implementation of the new reduced model of the extended Kalman filter (EKF) for small Euler angles on the Algerian microsatellite (Alsat-1). A specific implementation of the EKF is proposed to extract attitude and body rate in a circular low earth orbit (LEO) with a boom deployed for passive pitch and roll stabilisation and active Y-momentum wheel plus Z-reaction wheel and magnetorquer control. Numerical results show the effectiveness of the implementation. The simulation results have been validated using Monte–Carlo method. In-orbit test results are presented to evaluate the performance of the new reduced model of the EKF for small Euler angles during accurate Nadir-pointing control. [Copyright &y& Elsevier]