A system for the measurement of an angle of roll of a projectile is disclosed. The projectile has a casing with a rear end, a front end, and a side wall extending therebetween. The system includes a radar configured to transmit a polarized electromagnetic signal toward the projectile and a groove disposed on the side wall of the casing. The groove has a width, a depth, and a length, the width extending along a longitudinal axis of the projectile, the depth extending inwardly from an outer surface of the casing toward the longitudinal axis, and the length extending along the outside of the casing. The radar is further configured to receive a return signal from the projectile, wherein the return signal from the groove is modulated as a function of the angle of roll of the projectile. Amplitude or phase modulation of the return signal from the groove can be used to uniquely determine the roll angle of the projectile.