A Terminal Guidance Model for Smart Projectiles Employing a Semi-Active Laser Seeker

Report No. ARL-TR-5654
Authors: Luke S. Strohm
Date/Pages: August 2011; 82 pages
Abstract: This report describes the development of a semi-active laser terminal guidance model. The C++ class implementation of the model, sSalSeeker, can be executed stand-alone or be embedded into a larger guided projectile model. It was validated using the NVLaserD model written by the Night Vision and Electronic Sensors Directorate of the Communications-Electronics Research, Development, and Engineering Center.

The first objective of the model is to determine the laser power distribution at the seeker, accomplished by calculating the laser beam's transmission path and power loss. The beam is modeled stochastically through a set of rays forming a solid cone of the given divergence. Each ray's transmission path and power loss is calculated and its power is summed with the other rays' contributions at the seeker. Ray tracing is used to determine the ray-transmission paths from designator to target and target to seeker. The Beer-Lambert Law is used to compute power loss due to atmospheric attenuation. Lambert's Cosine Law and designator-seeker-target geometry are used to determine the portion of power that the seeker receives after it reflects off of the target. The second objective is to convert the seeker power distribution into projectile guidance signals. Guidance signals are calculated by dividing the power received in the pitching and yawing directions by the total power received by the seeker. The guidance signals are not considered reliable unless the seeker power is above a signal-to-noise threshold.
Distribution: Approved for public release
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Last Update / Reviewed: August 1, 2011