Augmented gyro-stellar model in the presence of measurements delay

In recent years, the tendency to decrease satellites’ size and costs has turned into more stringent requirements for lesser-performing sensors. The study of attitude estimation for micro-sat under measurements’ date errors in a gyro-stellar configuration is here presented. An augmented model is studied in which both the star tracker's and gyro's data are used as update measurements for the feed of the multiplicative extended Kalman filter. The analyzed configuration presents high-levels of gyro's noises. The augmented model successfully reduced the angular rate's estimation error compared to the well-established "Replacement mode" model of Farrenkopf’s equations. The filter is then modified to compensate the date error between the rate and attitude measurements by means of different algorithms, which capabilities are analyzed in a parametric study of the performances under variation of sampling time and measurements' delay. The compensation algorithms proved to be successful, but the performances are strictly dependent on the gyro's capabilities. The results are then exploited for the design of a filter that combines the two aspects and is applied with a star tracker and a rate-gyro readily available in the market