Virtual Roll Gyro for Spin-Stabilized Projectiles

A method is described for determining roll rate for a spin-stabilized projectile. A yaw signal and a pitch signal are measured for the projectile, wherein: (i) for a trajectory path being travelled by the projectile over the Earth's surface, projectile stability is created by spinning of the projectile about a longitudinal spin axis oriented tangent to the projectile trajectory, (ii) the yaw signal represents yaw motion of the projectile about a yaw axis oriented along a line through the Earth's center and orthogonal to the spin axis, and (iii) the pitch signal represents pitch motion of the projectile about a pitch axis orthogonal to the spin axis and the yaw axis, and wherein the yaw signal and the pitch signal are modulated by spin rate of the projectile spinning about the spin axis. A roll rate signal is extracted from one of the yaw signal and the pitch signal.