This book will introduce Aeronautical CNS principles and techniques and at the same time will pave the way for thorough analysis and further investigations on concepts and applications of Air Traffic Management (ATM) techniques. The aim of the proposed book is to provide a complete description of modern techniques used in Aeronautical Communications, Navigation and Surveillance (CNS), and will serve as a quick reference guide to a vast body of technical information about these three important applications involving space-based satellites. The author will approach satellite systems theory, applications and methodology aimed at aeronautical traffic management during every phase of navigation: taking off, en-route and landing. The book surveys the currently existing techniques for CNS, from the basic theoretical principles of communications, space technology, antenna technology, to the more systemic and macroscopic subjects of the use of these principles in actual ATC/ ATM systems, aeronautical communications systems, and safety systems.