Field measurements and comparisons to simulations of High Energy Laser propagation and off-axis scatter

The AFIT Center for Directed Energy's High Energy Laser End-to-End Operational Simulation (HELEEOS) model allows for the calculation of the irradiance from within a high energy laser beam that is scattered by molecules and particulates in the atmosphere to an off-axis observation point, while incorporating the spreading effects of the turbulence and thermal blooming. Field experiments conducted at Wright-Patterson AFB, Ohio in summer 2009 allowed for validation measurements for the HELEEOS off-axis algorithm to be collected. Turbulence strength measurements were made at a wavelength of 1.55 μm using a state of the art bistatic turbulence profiler for both horizontal and vertical paths. Pressure, wind speed, wind direction, relative humidity and aerosol loading data were collected simultaneously with the C_n ² measurements. As part of the experiment, the profiler's beams were imaged offaxis with a calibrated camera array and the received irradiance of the off-axis scattering was quantified. Characterization of the aerosol distribution along the laser path and the path to the observer is accomplished by determining the visibility and climatological aerosols for southwestern Ohio. Comparisons between predicted and measured off-axis irradiance are made.