A scientific overview of current and future satellite systems for mobile and broadband communications. In part I, the fundamentals of geostationary and non-geostationary satellite constellations and the related questions of communications technology are treated. Part II deals with satellite systems for mobile communications and treats several network features as well as their technology, regulation and financing. Part III is devoted to future satellite systems for broadband communications and explains the specialities of satellite communications, particularly on the basis of ATM and TCP/IP. An extensive survey on operating and planned satellite systems completes the book.