What is a Satellite: Meaning, Types, Functions and Role in Science

A satellite is a celestial body that revolves around a bigger celestial body such as a planet or a star. For example, the moon is a natural satellite that orbits earth. It doesn't have its own light and reflects the light from other stars. There are many other objects that are also revolving around our planet and gathering information about it to predict natural disasters or calamities like hurricanes to prevent the loss of life and other threats. These objects are man-made satellites called artificial satellites. Earth’s artificial satellites capture images to help in predicting various meteorological events as well as other purposes. Let’s learn in detail about what a satellite is and how different types of satellites work and their roles in our environment.

Table of Contents

• What is a Satellite
• Types of Satellite
• How does an Artificial Satellite Work

What is a Satellite

A satellite is an object that travels around other larger objects in space. It has its own orbit and can be classified into two different categories: Natural satellites that can orbit without any human intervention and man-made satellites are machines that are launched by humans to monitor various celestial bodies and collect different types of information for navigation, weather, broadcasting, research, etc. An example of natural satellites is the moon revolving around earth. Saturn is the planet which has the highest number of natural satellites revolving around it. Man-made or artificial satellites are the objects that humans send to space to collect information in space. They are launched for different purposes and play an important role in improving our life on earth. 

Types of Satellite

There are two types of satellites: 

• Artificial Satellites
• Natural Satellites. 

Natural Satellite: Our solar system has many natural satellites. Most of the planets including earth have natural satellites revolving around them. Jupiter has 95 of them out of which Ganymede is the largest which is bigger than mercury. The moon is orbiting earth and is at a distance of 384,400 kilometres. The Moon takes around 27.3 days to complete one orbit of earth.

Artificial Satellite: These are man-made machines launched into space by humans. The purpose of these satellites is to gather information about various celestial events and work as a high-tech laboratory to aid researchers. These satellites are able to see a vast part of Earth at once and can help in sending information to various places. GPS (global positional system) is a satellite based navigation system providing precise timing and path information through satellites to navigation systems on earth. 

The first artificial satellite named Sputnik 1, was sent to space on October 4, 1957 by the Soviet Union. This small, metallic satellite was spherical in shape and had a diameter of about 58 centimetres. Today there are around 12,952 satellites orbiting earth and they help in communication, navigation and environmental monitoring on earth. There are navigational, weather, communication, astronomical and military satellites that play a key role in different fields to gather information and provide solutions.

How does an Artificial Satellite Work

A satellite is launched into space by giving it enough velocity to enter orbit. The balance between the satellite's forward movement and earth's gravitational pull keeps it revolving around a body at exactly the right speed and altitude. These satellites are revolving at a very high speed of approximately 7.8 kilometers per second and can complete on orbit in 90 minutes. These satellites orbit in three different levels.

Lower Earth Orbit: These satellites revolve at the least distance from the earth which is between 300 to 2,000 kilometres above the surface of the earth. It is perfect for launching satellites that need less signal power for transmission, for example communication satellites. 

Medium Earth Orbit: The orbit located between low earth and geostationary orbits is called medium earth orbit. It is about 5,000 to 20,000 Km away from earth’s surface. Navigational service such as GPS is a Medium Earth Orbit satellite used by millions of people worldwide for commuting.

Geostationary Earth Orbit: This type of satellite rotates above the equator of earth and matches the earth’s rotation from west to east. It completes on full orbit in around 23 hours 56 minutes and 4 seconds. Examples of GEO satellites are weather monitoring satellites that capture and predict weather events.