Rewinding to few years before, Stars would help us know the directions. Today, as we are progressing we have a map in our hand before we start for the journey. Thanks to the Satellites that has made our lives so easy! Satellite is an orbiting object in the space revolving around bigger objects. As the satellites are placed intentionally in an orbit they are known as artificial satellites. Moon is our only natural and permanent satellite. Multiple other natural satellites are present in the solar system.
For other artificial satellites, there is a launch vehicle places it into orbit. Satellite is lifted off from a launch pad on land, at sea from a submarine, a mobile maritime platform, or aboard a plane. Artificial satellites came into existence in the mid-20th century when the first artificial satellite Sputnik, a Russian space probe was lifted off on Oct. 4, 1957. The International Space Station is the largest man made satellite in orbit.
These are basically computer-controlled systems with four main parts to it:
- Power System
- Altitude Control
- Antenna for transmitting and receiving information
- Payload for information gathering
A Satellite’s orbit can be an ellipse or a circle that moves around two points known as foci. The planet is located at one of the foci. As a result, the net force applied to the satellite is not uniform around the orbit thus affecting its speed. It moves fastest when it’s closest to the planet and slowest when it’s farthest from the planet. The point closest to the planet is known as perigee while that when farthest from the planet is apogee.
Satellite subsystems attend many tasks, such as power generation, thermal control, telemetry, attitude control and orbit control. Besides the GPS, satellites are used for many purposes. Several other applications are that they can be used for military observations, communication, for mapping stars and planetary surfaces, to determine the weather. They also take pictures of their respective planets. Satellite can be classified in a number of ways depending on their purpose. Some of them are low Earth orbit, polar orbit, and geostationary orbit, drone satellite, ground satellite, etc.
There have been several Satellites in the space by now. From 2018 estimate, some 4,900 have remained in orbit, out of which about 1,900 were operating. Remaining has become debris.