A satellite is an object in space that orbits or circles around a bigger object. There are two kinds of satellites: natural (such as the moon orbiting the Earth) or artificial (such as the International Space Station orbiting the Earth).
There are dozens upon dozens of natural satellites in the solar system, with almost every planet having at least one moon. Saturn, for example, has at least 53 natural satellites, and between 2004 and 2017, it also had an artificial one — the Cassini spacecraft, which explored the ringed planet and its moons.
Artificial satellites, however, did not become a reality until the mid-20th century. The first artificial satellite was Sputnik, a Russian beach-ball-size space probe that lifted off on Oct. 4, 1957. That act shocked much of the western world, as it was believed the Soviets did not have the capability to send satellites into space.
Source Space.com
Satellites play an essential role in our everyday lives. In fact, they contribute to our well-being and make it possible for us to meet many important needs and challenges on Earth. They are useful in many fields, such as Earth observation, communications, navigation, and science.
Satellite data helps:
Source Canadian Space Agency
Satellites are able to orbit around the planet because they are locked into speeds that are fast enough to defeat the downward pull of gravity. Satellites are sent into space by a rocket launched from the ground with enough energy (at least 25,039 mph!) to get outside our atmosphere. Once the rocket reaches its determined location it drops the satellite into its orbit. The initial speed of the satellite maintained as it detaches from the launch vehicle is enough to keep a satellite on orbit for hundreds of years.
A satellite maintains its orbit by balancing two factors: its velocity (the speed it takes to travel in a straight line) and the gravitational pull that Earth has on it. A satellite orbiting closer to the Earth requires more velocity to resist the stronger gravitational pull.
Satellites do carry their own fuel supply, but unlike how a car uses gas, it is not needed to maintain speed for orbit. It is reserved for changing orbit or avoiding collision with debris.
Source NOAA
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