REORIENTING SPACECRAFT USING INITIAL SINGLE AXIS ATTITUDE

摘要

A method for aligning a spacecraft (1) along an axis, comprising the steps of using quaternion feedback control (20) to reorient the spacecraft (1), and during the step of reorienting, using rate integrating gyroscopes in a pulse rebalance loop. The method operates to orient the spacecraft along an inertial direction of interest by the steps of operating a sensor to provide an initial fix on the inertial direction of interest (B1); repetitively determining a difference between a common quaternion and a quaternion estimated based on a sensed angular rates; and selectively applying torques to the spacecraft so as to drive the difference towards zero such that a spacecraft vector is aligned with the inertia direction of interest, thereby orienting the spacecraft. One mode of operation maintains the spacecraft fixed in orientation, while another mode of operation rotates the spacecraft about the direction of interest by using a bias-rate (14) blind quaternion propagation technique.