ESA GNC Conference Papers Repository

This paper presents current developments of the attitude determination algorithm for Del¯-n3Xt, TUDelft next nano-satellite. Several novel quaternion ¯lters using rate gyro outputs and vector observations are presented. The covariance propagation can cope rigorously with the multiplicative process noises. The quaternion measurement matrix associated with single line-of-sight measurements is shown to be rank de¯cient. This property is exploited in order to design reduced order update stages in the ¯lters. The reduction is designed such as to preserve the statistical information. The paper also describes the de- velopment of a four-quadrant Sun sensor. A simple algorithm allows Sun vector determination at sensor level while alleviating the need to know uncertain physical parameters. The design takes into account geometrical imperfections linked to manufacturing limitations. A thorough error analysis of the pho- todiodes measurement chain is provided. Sun vector determination at spacecraft level is designed and illustrated, in the absence of Earth albedo e®ect, via Monte-carlo simulations and experimental valida- tion. In addition, extensive Monte-Carlo simulations illustrate the good performances of the quaternion ¯lters using Sun vector and Earth magnetic ¯eld measurements. The novel reduced ¯lter shows good performances in a challenging tumbling dynamics environment, where a standard additive Kalman ¯lter fails to converge.