Proceedings Article | 17 May 2013
Proc. SPIE. 8732, Atmospheric Propagation X
KEYWORDS: Atmospheric modeling, Speckle, Turbulence, Fiber optic illuminators, Signal to noise ratio, Speckle pattern, Data modeling, 3D modeling, Sensors, Unmanned aerial vehicles
Aimpoint acquisition and maintenance is critical to high energy laser (HEL) system performance. This study
demonstrates the development by the AFIT/CDE of a physics-based modeling package, PITBUL, for tracking airborne
targets for HEL applications, including atmospheric and sensor effects and active illumination, which is a focus of this
work. High-resolution simulated imagery of the 3D airborne target in-flight as seen from the laser position is generated
using the HELSEEM model, and includes solar illumination, laser illumination, and thermal emission. Both CW and
pulsed laser illumination are modeled, including the effects of illuminator scintillation, atmospheric backscatter, and
speckle, which are treated at a first-principles level. Realistic vertical profiles of molecular and aerosol absorption and
scattering, as well as optical turbulence, are generated using AFIT/CDE’s Laser Environmental Effects Definition and
Reference (LEEDR) model. The spatially and temporally varying effects of turbulence are calculated and applied via a
fast-running wave optical method known as light tunneling. Sensor effects, for example blur, sampling, read-out noise,
and random photon arrival, are applied to the imagery. Track algorithms, including centroid and Fitts correlation, as a
part of a closed loop tracker are applied to the degraded imagery and scored, to provide an estimate of overall system
performance. To gauge performance of a laser system against a UAV target, tracking results are presented as a function
of signal to noise ratio. Additionally, validation efforts to date involving comparisons between simulated and
experimental tracking of UAVs are presented.
