Laser-modulated aerosol infrared decoy

Abstract

A system for protecting ships from attack by an infrared-seeking missile is provided which comprises decoying the missile by deploying an aerosol. In one embodiment, the aerosol merely scatters a modulated light beam. Another embodiment deploys particles that can undergo an exothermic photochemical reaction when initiated by an ultraviolet laser. The laser projects an image of the ship onto the aerosol and at the same time causes the particles to generate sufficient heat to attract the infrared-seeking missile away from the ship. This system presents an infrared-decoy target with a suitable infrared image of appropriate spatial scale to mislead a missile with imaging capability. The spectral content of the decoy's image resembles that of a blackbody 20°-50 ° C. above ambient, and has a brightness and spatial extent equal to the largest ships, approximately 10 kw/steradian, in the 3-5 and 8-12 micrometer bands. The present invention is simple to use, rapidly deployed, and capable of presenting a decoy target that can last at least a minute or more.

What is claimed is: 
     
       1. A method of decoying infrared sensors, said method comprising the steps of: a) deploying an aerosol of particles capable of undergoing an exothermic reaction responsive to illumination by an appropriate wavelength of light;   b) modulating a beam of light at said wavelength with a preselected image; and   c) illuminating said aerosol with said beam of light.   
     
     
       2. The method of decoying infrared sensors of claim 1, wherein said deploying is accomplished by an exploding canister. 
     
     
       3. The method of decoying infrared sensors of claim 1, wherein said exothermic reaction is photochemical. 
     
     
       4. The method of decoying infrared sensors of claim 3, wherein said particles are comprised of benzaldehyde. 
     
     
       5. The method of decoying infrared sensors of claim 1, wherein said exothermic reaction is oxidation. 
     
     
       6. The method of decoying infrared sensors of claim 5, wherein said particles are comprised of a metal. 
     
     
       7. The method of decoying infrared sensors of claim 6, wherein said metal is coated with a compound whose permeability to oxygen increases on exposure to said wavelength of light. 
     
     
       8. The method of decoying infrared sensors of claim 1, wherein said beam of light is projected by a laser. 
     
     
       9. The method of decoying infrared sensors of claim 1, wherein said wavelength of light is an ultra-violet light. 
     
     
       10. A method of decoying infrared sensors, said method comprising the steps of: a) deploying an aerosol capable of scattering infrared light;   b) modulating a light beam composed of multiple wavelengths of light with a preselected image; and   c) illuminating said aerosol with said light beam.   
     
     
       11. An apparatus for decoying infrared sensors, said apparatus comprising: a) means for deploying an aerosol capable of undergoing an exothermic reaction responsive to illumination by an appropriate wavelength of light;   b) means for modulating a beam of light at said wavelength with a preselected image; and   c) means for illuminating said aerosol with said beam of light.   
     
     
       12. The apparatus for decoying infrared sensors of claim 11, wherein the means for illuminating comprises a laser.