As we discussed in the previous chapter, satellites can provide numerous services to support life on Earth. The satellite itself needs to be designed, implemented, and tested carefully to provide the services it is intended to provide—and its mechanical structure must be robust enough to endure the stress caused by the launch into the space. In this chapter we will describe how satellites are launched into their operational orbits and the phases of a satellite lifetime. We will learn how the satellite motion in orbit is mathematically modeled. The most important orbits used by satellite communications satellites are described and basic mathematical equations to describe satellite movement, propagation delays, and basic geometry are given. Since the modern trend is to implement large constellations of satellites consisting of hundreds or even thousands of satellites, we will also cover the main methods to design such a constellation.