Aero-optical and plume effects in airborne laser countermeasure applications

In airborne laser countermeasure applications (DIRCM) several sources of perturbations, which affect the performance of the system, need to be considered. The main task of a DIRCM system is to optimise the laser irradiance at the target (missile) for a certain time until break-lock can be verified. Perturbations such as: platform-induced jitter, aero-optical effects, jet engine exhaust plumes and strong turbulence may severely degrade the performance. In this report strong perturbations relevant for DIRCM applications have been reviewed. The most important aero-optical effects include turbulent boundary and shear layers, inviscid flow and shocks. Contributions from these effects to the laser beam quality have been estimated using simple models and experimental data. Experimental data and models available on plume effects, relevant for fast jet installations, have been reviewed. Calculations aiming to estimate the tracking performance and beam optimisation in different turbulence situations are presented.