An attitude determination and control system of the ALSAT-1 first Algerian microsatellite

ALSAT-1 is a low-cost Algerian microsatellite build by Surrey Satellite Technology Ltd. (SSTL), it is designed to be part of a five microsatellites constellation for daily disaster monitoring. The microsatellite uses a Y momentum and Z reaction wheels, 3-axis magnetorquer rods and a single butane gas thruster for orbital maintenance. The magnetorquer rods do momentum maintenance and nutation damping f or Y/Z wheels and, libration damping and yaw phase control. The attitude sensor used, is a 3-axis fluxgate magnetometer and a sun sensor. Precise orbital knowledge will be obtained using an antenna GPS receiver supported by an on-board orbit estimator. This paper describes the various attitude control modes required to support: (1) initial attitude acquisition phase, (2) imager nadir pointing attitude controller. The specific attitude controllers and estimators used during theses modes are explained. Simulation and in-orbit commissioning results are presented to evaluate the performance and design objectives.

I. Introduction

ALSAT - 1 is the first satellite for the National Center of Spatial Techniques (CNTS)-Arzew-Algeria designed, built, assembled and tested, at the Surrey Satellite Technology Ltd. (SSTL) at the University of Surrey, by the Algerian know how transfer team under SSTL engineers assistance. The project will cover all aspects of satellite engineering within a technology transfer program between SSTL and the CNTS.