This book introduces engineering students and practitioners to the tools and insights for pursuing first-order system design in the areas of imaging, lidar, LADAR, and communications. Today's gig employment philosophy requires the hired engineer to contribute immediately; there is no time for a long learning curve. This book provides validated analytical models, including the supporting data in some cases, so that an engineer can quickly succeed in system development for several selected application areas. Much of the information presented can be leveraged for other FSEO applications that are not covered. Various aspects of normally encountered channel effects and how to model them with equations validated by field experiments are described. Signal-plus-noise and target-or-clutter (replacement model) detection theories are also discussed and analyzed. Finally, problems are included to help solidify the material covered, and selected sets of data comparisons are provided to give engineers a feel for the numbers and the magnitude of the various degradations.