Abstract: A roll measurement system for a flight vehicle, such as a tank-launched ged projectile or guided missile, includes a power source and a pulsed laser, such as a laser diode, which propagates a laser beam which is focused into a narrow conical beam and directed toward the earth. The laser beam's reflections from the earth are detected, for example, by a photo-diode, and converted into an analog electrical signal. The signal is converted to digital form and analyzed to determine its nadir (the shortest path-length to the earth). A microcomputer compares the immediate nadir determination with stored nadir determinations to compute the angle and rate of roll of the flight vehicle.