Understanding Artificial Satellites

Definition and purpose of artificial satellites

An artificial (human-made) satellite is an object—typically a spacecraft—placed into orbit around a celestial body. For Earth, satellites are launched from the surface into space and then placed into an appropriate orbit where they can operate for their mission. They are used for many purposes, including communication relay, weather forecasting, navigation (e.g., GPS), broadcasting, scientific research, and Earth observation. Some satellites also support military roles such as reconnaissance, early warning, signals intelligence, and potentially weapon delivery. Even non-mission payloads can be considered satellites, such as spent rocket stages or defunct satellites. Satellites are designed to survive the space environment and to function reliably. Most active satellites include onboard power generation (commonly solar panels, or sometimes radioisotope thermoelectric generators), and they use communication systems (often transponders) to exchange data with ground stations. Many satellites rely on standardized “bus” designs to reduce cost and speed development, and groups of similar satellites can operate together as constellations. Their orbits and orientations must be controlled so they can communicate and perform their tasks, and they may use propulsion (chemical or ion thrusters) to adjust or maintain orbit. Overall, the purpose of artificial satellites is to provide services and gather information from vantage points in space that are difficult or impossible to achieve from the ground.

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Satellite components: power and communication

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