Roll measurement system for flight vehicle

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.

What is claimed is: 
     
       1. In a flight vehicle subject to roll about its axis, a system for the determination of the direction and degree of roll, the roll determination system including an electrical power source and a pulsable laser means connected to said power source to propagate a pulsed laser beam;   focusing means to direct said beam from said laser means into a narrow beam adapted to be directed toward the earth when the vehicle is in flight;   a laser beam receiver means to detect and receive the reflections from the earth of said propagated laser beam and produce electrical signals in accordance therewith; and   computation means connected to said receiver means to derive the roll angle from the said electrical signals.   
     
     
       2. A roll determination system as in claim 1 wherein said flight vehicle is a tank-launched guided projectile. 
     
     
       3. A roll determination system as in claim 1 wherein said flight vehicle is a guided missile. 
     
     
       4. A roll determination system as in claim 1 wherein said pulsable laser means includes a laser diode transmitter and laser receiver. 
     
     
       5. A roll determination system as in claim 1 wherein said focusing means focuses said beam in a radial pattern and in a beam width in the range of 1/2 to 2 degrees. 
     
     
       6. A roll determination system as in claim 1 wherein said laser receiver means has a field-of-view in the range of 2 to 8 degrees. 
     
     
       7. A roll determination system as in claim 1 and further including noise reduction means connected between said receiver means and computation means to reduce noise by amplification of the transducers dark noise and without detection of the reflected beams, and rectifying and filtering said amplified dark noise. 
     
     
       8. A roll determination system as in claim 1 wherein said computation means includes an analog to digital converter, digital memory storage means, and digital comparison means to determine the greatest in amplitude of a series of pulses and to derive the center of said pulse series. 
     
     
       9. In a tank-launched guided flight vehicle subject to roll about its axis, a system for the determination of the direction and degree of roll, the roll determination system including: an electrical power source and a pulsable laser means including a laser diode connected to said power source to propagate a pulsed laser beam;   a focusing means to direct said beam from said laser means into a narrow beam in the range of 1/2 to 2 degrees adapted to be directed toward the earth when the vehicle is in flight;   detection means to detect and receive the reflections from the earth of said propagated laser beam from a field-of-view in the range of 2 to 8 degrees and produce electrical signals in accordance therewith;   computation means connected to said detection means to derive the roll angle from the said electrical signals.   
     
     
       10. A roll determination system as in claim 9 wherein said computation means includes an analog-to-digital converter, digital memory storage means, and digital comparison means to determine the greatest in amplitude of a series of pulses and to derive the center of said pulse series.