Enhanced IR point target detection by atmospheric effects

Next generation IR Search and Track Sensors (IRSTs) will use IR Focal Plane Arrays (IRFPAs) because of their benefit concerning increased sensitivity, higher update rate and inhernet capability of enhanced processing. Moreover the full stare RIST concept allows a more flexible set-up on the platform to be protected such as ships, airplanes or air defence sites. The increased sensitivity is primarily a consequence of the large amount of detector elements in use, leading to longer integration times in comparison with present generation IRSTs. If increased sensitivity is not required, a trade-off can be made on dimensions of the optics, the most vulnurable part of the system. It was found during a series of experiments at various locations, that in many occasions optical phenomena in the marine boundary layer, such as sub-refraction and scintillation, provide additional sensitivity, when appropriate signal handling is used. Of course this enhanced sensitivity is partly reduced by the greater extinction in this boundary layer due to higher relative humidity and aerosol concentration. These phenomena have been investigated in great detail and new models tend to predict their magnitude when adequate input parameters are used. This paper describes the basics of next generation IRSTs and the results of the investigations on enhanced IR point target detection performance by proper use of the atmospheric 'multiplier' effects.