MODTRAN© is a powerful program capable of describing atmospheric absorption, scattering, and emission paths, but it has a complicated computer-card input structure; a custom user interface, PcModWin®, was introduced to minimize setup and error-mitigation issues. The instruction manuals for these programs provide over 80 test cases, which are instructive for intermediate to advanced users but do not provide detailed explanations. This book is intended to help beginners learn how to perform analysis using MODTRAN/PcModWin by exploiting these test cases. Specifically, many of the cases are used to illustrate how to navigate the PcModWin menus to solve the given problems. The book also provides the underlying mathematics and atmospheric physics incorporated into MODTRAN.