Patent ID: 9073648
Filing Date: 2015-07-07
Classification: B64G,G01C,G01P

Abstract:
1. A method of estimating a three-axis attitude and rate of a spacecraft in a spacecraft body frame of reference, comprising: (a) measuring star vectors at a plurality of instants of time using a star tracker attached to a spacecraft; (b) calculating a respective spacecraft body frame-to-ECI frame quaternion for each instant of time based on information derived from said measured star vectors; (c) calculating spacecraft body rates based on the quaternions calculated in step (b); (d) forward Kalman filtering the calculated spacecraft body rates; (e) backward Kalman filtering the calculated spacecraft body rates; (f) averaging the results of steps (d) and (e) to produce average rate estimates; (g) selecting one of the average rate estimates, or calculating a rate estimate that is a function of two or more of the average rate estimates; and (h) calculating a three-axis attitude of the spacecraft based on the rate estimate selected or calculated in step (g).