An optical sensor and method for detecting a projectile velocity vector includes optically detecting the arrival of a projectile. The sensor includes a sandwich of a transparent layer within two reflective layers, which in turn are within two opaque layers. An optical sensor structure includes a set of sensors positioned in respective planes, wherein at least two non-parallel optical sensors are used for each trajectory dimension of interest that differs from the primary direction of motion of the projectile and one additional optical sensor may be used for independent measurement of velocity attenuation. An optical sensor structure includes a set of sensors positioned in respective planes, wherein at least two of the optical sensors are oriented in respective planes that are parallel and potentially offset from each other. A tiling of the optical sensors or optical structures is also possible.