Attitude Determination and Control System for Cube Satellite

Abstract

ISRASAT1 is a nano-satellite designed, built and integrated at the Institute of Space Research and Aerospace (ISRA). It aims to provide an educational and testing tool technology platform, and to increase the interest and expertise in the field of space technology. It is also intended for the investigation of the possibility of using a low-cost cube satellite in the field of remote sensing and Earth observation. The mission of ISRASAT1 is to take images of Khartoum state and transmit those images to ISRA ground station that tracks the satellite. In order to take images with high quality and to achieve better communication, the satellite needs an attitude determination and control subsystem (ADCS). This thesis was motivated by the need to develop an ADCS for the project of ISRASAT1. In this thesis, the design of attitude determination and control subsystem of ISRASAT1 nano-satellite is presented. A nonlinear mathematical model of nano-satellite as a rigid body is derived. A linearized model and linear state variable are used to design a pointing controller. Different types of ADCS hardware and their advantages and disadvantages with a brief description of the principle of their operation have been discussed. In the design of the ADCS, a three-axis magnetometer, six Sun sensors, and a GPS receiver are used as the sensors for attitude determination. The attitude controller is designed to achieve the desired attitude, which is nadir pointing using three orthogonal reaction wheels and three orthogonal magnetic coils. Two attitude control modes have been considered, de-tumbling mode and pointing mode. The B-Dot control algorithm is used in de-tumbling mode, while quaternion feedback algorithm is used in pointing mode. The designed controller is implemented and analyzed using MATLAB environment.