A satellite is an object that orbits around a larger object. There are two types of satellites: natural and artificial. Natural satellites are celestial bodies, such as the moon orbiting the Earth, while artificial satellites are man-made machines launched into space that move around Earth or another body in space. Satellites have a variety of uses, including communication relay, weather forecasting, navigation, broadcasting, scientific research, and Earth observation. Additional military uses are reconnaissance, early warning, signals intelligence, and potentially weapon delivery. Some satellites take pictures of the planet that help meteorologists predict weather and track hurricanes, while others take pictures of other planets, the sun, black holes, dark matter, or faraway galaxies, which help scientists better understand the solar system and universe. Satellites are also used for communications, such as beaming TV signals and phone calls around the world, and for navigation, such as the Global Positioning System (GPS) .
Artificial satellites have a communications system that receives signals from Earth and retransmits those signals back with the use of a transponder, which is an integrated receiver and transmitter of radio signals. Satellites must be able to withstand the shock of being accelerated during launch up to the orbital velocity of 28,100 km an hour and a hostile space environment where it can be subject to radiation and extreme temperatures for its projected operational life, which can last up to 20 years. To meet these challenges, satellites must be small and made of lightweight and durable materials. They must operate at a very high reliability of more than 99.9 percent in the vacuum of space with no prospect of maintenance or repair.
In summary, a satellite is an object that orbits around a larger object, and it can be either natural or artificial. Satellites have a variety of uses, including communication relay, weather forecasting, navigation, broadcasting, scientific research, and Earth observation. Artificial satellites are machines made by people that are launched into space and orbit Earth or another body in space. They have a communications system that receives signals from Earth and retransmits those signals back with the use of a transponder. Satellites must be able to withstand the shock of being accelerated during launch and a hostile space environment for their projected operational life, which can last up to 20 years.
