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Satellites of the Earth: Her Eye in the Sky

Omkar Phatak
What are the different types of satellites? How many of them are in orbit? Read to find all the answers.
One of the prime factors which boosted telecommunication technology, was the launch of artificial satellites in orbit around the Earth. These silent sentinels keep orbiting the Earth, aiding the transmission of signals and performing hundreds of other tasks like remote sensing and provision of meteorological data.
A network of satellites is the backbone of modern GPS navigation systems, that enable the usage of tracking devices.

How Do Satellites Work?

Any object in a steady orbit around the Earth is a satellite. Man-made ones, placed in orbit around the Earth, through the use of special launch rockets, are called artificial satellites, as opposed to the Moon, which is a natural one.
Using precise calculations made by scientists, a satellite is launched to a certain altitude by a rocket and then put in the orbit. Sputnik, launched in 1957, was the first ever man-made satellite to successfully orbit the Earth.
The calculations of altitude and the velocity imparted to the satellite are such, that it never falls down and continues to revolve around the Earth like the Moon. They are equipped with solar panels (for power) and transponders, as well as a mini-computers, that manage all their functions.

Their Total Number

It has been more than 50 years since the launch of the first satellite and by now, more than 50 countries have launched their own. The current number of those in orbit around the Earth is so high, that in coming years, a traffic jam of sorts may occur in space.
The United Nations Office for Outer Space Affairs (UNOOSA) reports that there are 4857 satellites currently orbitting the Earth. They serve various purposes and move in orbits of varying shapes and altitudes.

Different Types

There are various ways in which satellites may be classified. One way is to classify them according to the kind of orbit they are in (like those in geosynchronous orbit, which have a low altitude and revolution rate, matching with that of the Earth) or the function that they serve.
We choose the latter type of classification. Here are the prime types:
  • Weather: They provide us with detailed photographs of the Earth's surface, which enable weather prediction. They can track all the weather changes on Earth.
  • Astronomical: These are orbiting telescopes like Hubble, that observer distant astronomical objects.
  • Communications: These enable communication between different points on Earth, providing TV, GPS, and satellite phone technology. They are generally placed in low-earth or geosynchronous orbits.
  • Earth observation: These satellites are designed for a unique purpose like study of oceans, minerals, or for pure scientific research.
  • Space Stations: These are designed to be stations in space where astronauts can actually live and future missions can be launched. The one and the only example just now is the International Space Station (ISS).
  • Anti-Missile/Spy: These satellites are launched for defense purposes and can intercept missile attacks and activate protection for the same, by launching missile shields. Some are used for spying on enemy activity across borders.
It is due to these different types, that rapid sharing of information at the speed of light is made possible.
Everything from cable TV, your car GPS, meteorological forecasts, defense-related monitoring, and even the Google Earth data you see on your screen is made available by satellites, which are incessantly orbiting the Earth. Thanks to our eyes in the sky, reaching out to any corner of the world, is easily possible.