Variable Angular Rate Measurement for a Spacecraft Based on the Rolling Shutter Mode of a Star Tracker

Angular rate is a piece of useful information for the attitude control of a spacecraft. The star tracker as a space optical sensor can be used to measure the angular rate of a spacecraft. In this paper, a novel approach is proposed to improve the measurement accuracy of the angular rate during spacecraft rotation. The electronic rolling shutter (RS) imaging mode of the complementary metal-oxide semiconductor (CMOS) image sensor in a star tracker is applied to obtain much higher sampling frequency for reducing the change of the angular rate between the sampling interval. The optic flow vector on the imaging plane is approximated within the second order using three successive star images to reflect the nonlinear effect from the variable angular rate. The experiment is performed to demonstrate the advantage of the new approach for variable angular rate measurement.