Comparison of small satellite attitude determination methods

Abstract

Satellite attitude determination methods usually fall in one of two classes: point-by-point and recursive estimation algorithms. Point-by-point attitude determination is based on the measurements of two or more sensors in a single point in time, while recursive estimation uses information from successive time points, as well as knowledge about the spacecraft dynamics and/or kinematics models. In small satellites, a single attitude sensor is often available, due to cost and space constraints, thus leading to the exploration of recursive estimation based solutions, such as the Kalman filter. In this paper, the results of using a point-by-point Singular Value Decomposition (SVD) algorithm are compared to those obtained by an Extended Kalman Filter (EKF), when applied to a simulation of the small satellite PoSAT1, which includes on board magnetometers and a Sun sensor. Questions of both theoretical and practical nature are discussed and analysed.