Since the 5th edition of the book “SATELLITE COMMUNICATIONS SYSTEMS” was published in December 2009, there have been great advances related to satellite communications systems, technologies, network architectures and new requirements of services and applications. This welcome 6th edition of the book covers the state of the art satellite communication systems and technologies. It examines the relevant topics concerning communication and network technologies, concepts, techniques, algorithms and architectures which are important for students to learn the subject, engineers to design and develop satellite communication systems and networks, and operators providing services, as well as users to better utilise the valuable resources. This new edition covers the topics from fundamentals to advanced levels. Though it would be advantageous to have some background on digital communication systems and broadband networks, sufficient detail will be provided to allow high level UG and PG MSc students, PhD researchers and professional engineers to follow the book for learning and for reference.