The Flight Follower System type 630 uses a computer-controlled rotating mirror to allow projectiles of varying calibres and velocities to be filmed by a high-speed video camera. A projectile can be accurately tracked over distances up to several hundred metres.

START and STOP skyscreens are placed some metres in front of the muzzle. Pulses from the skyscreens are passed to a control unit which then calculates the projectile's speed once the STOP screen has triggered. The calculated speed is then used to generate the controlling waveform for the servo-controlled mirror. The mirror tracks the flight of the projectile over a scanning angle range of -45° to +45°, although the starting position of the mirror is at -50° (the HOME position).

Once the projectile's speed is known, the control unit calculates the delay time for the projectile to reach the HOME position. At this point, the mirror sweep is initiated. The first five degrees are required for the mirror to accelerate to the required scanning speed. The mirror tracks the projectile across its line-of-flight from -45° to +45°, this requires a constantly varying angular velocity. The distance from the mirror axis to the line-of-flight is known as the 'stand-off distance'. The rate at which the mirror tracks the projectile is termed the 'scan rate'. The most important reference point is the -45° point, as this is the position at which the projectile will begin to be accurately tracked.

Recent developments have taken account of drag to give high-precision tracking.

The mirror is mounted on a spindle and is directly driven by a galvanometric scanner mechanism. The mechanism is mounted inside a metal cylindrical housing. The mirror provides an image of the projectile to the camera through a window in the housing. The housing is secured to a turntable which rotates about the axis of the mirror and is used to align the mirror during initial setting-up. The turntable rotates on a base which may be levelled by adjustable feet and can be secured to a separate platform which is used for mounting the camera.

The Flight Follower product, includes the mirror assembly, a control unit, a minimum of two trigger units and a suitable high-speed video camera.

Photo courtesy of DRS Data and Imaging Ltd - The flight follower system utilises technology licensed from Dr B.D McCarthy of Heathfield Technology Ltd