1. Introduction

This book attempts to present the tracking, telemetry, and command (TT&C) of flight vehicles such as air vehicles (less than 20 km in altitude), near-space vehicles (20–100 km in altitude), and spacecrafts (greater than 100 km in altitude). Those flying at an altitude of more than 2 × 10⁶ km are also known as deep-space vehicles. Specifically, the flight vehicles include missiles, satellites, spaceships, space stations, deep-space probes, near-space vehicles, UAVs, airships, or balloons, all of which are subject to TT&C. For TT&C and communication (C&T) systems, there are radio, optical, infrared, and other types. Among them, the radio continuous-wave C&T system is the most widely used one, which is mainly described in this book.