[Physics Class Notes] on Earths Satellites Pdf for Exam

A satellite is something that orbits or goes around the planet or a star, and there are varieties of satellites existing in the sky. A natural thing present in the sky is the Moon. 

There are many satellites, which are man-made and are launched into space for accomplishing a purpose like ISRO’s Mangalyaan satellite was launched into space for accomplishing the Mars Orbiter Mission, ICESat satellite was designed by NASA for getting an answer to questions related to earth’s climate system, global climate change and variations in sea levels, etc.

In this article, we are going to learn about earth’s satellites and the types of satellites.

Types of Satellite

The types of satellites are as follows:

Let’s discuss these one-by-one:

Natural Satellite

A satellite that is existing naturally in the sky and orbits around the celestial body is called the natural satellite. 

A natural satellite is an object that revolves around a body bigger than its size and humans have no role in their development or launching. These objects are often referred to as moons. 

Moon is an astronomical body also called the natural satellite because it revolves around the earth.

The Fun Fact

There are 240 recognized moons within the solar system, involving 163 revolving around the planet, four orbiting around dwarf planets, and dozens of others revolving around the tiny solar bodies. 

Artificial or Man-Made Satellite 

Artificial is something related to the role of humans, and when satellite word gets added to it, it becomes a man-made satellite. One of the most widely known examples is the earth’s satellite.

They are around 1,100 artificial satellites orbiting the earth. An artificial satellite is a sort of spaceship that revolves around the earth. It is made of a computer, along with two solar panels to obtain power from the Sun. 

They do have cameras or other scientific tools to help scientists gather information.  

History of a Man-Made Satellite

If we look back to the time in 1687, a great Physicist and Mathematician, Sir Isaac Newton was the first person to suggest the idea of an artificial satellite in his book named Philosophiae Naturalis Principia Mathematica.

Nearly three years after Newton discovered his theory on artificial satellites, the Soviet Union launched its first-ever Earth’s satellite named Sputnik 1 on October 4, 1957. 

Sputnik 1 was about the size of a beach ball and it was able to circle the earth every 96 minutes and its radio signals were heard by scientists & radio operators worldwide.

Following the Soviet Union, three months later, on January 31, 1958, the US launched its first satellite named Explorer 1. This satellite was smaller than Sputnik 1. 

This satellite was designed to detect radiation and it helped discover the core of the two Van Allen Radiation Belts.

Van Allen Radiation belts are a zone of the electrically charged particles that borders the Earth.

From these two examples, we understood what satellites are used for.

What are Satellites Used for?

One of the unimaginable things is, there are around 2000 satellites revolving around the earth simultaneously, all these satellites do a unique job. 

For example, by gathering data or pictures of the earth’s surface, the scientists can learn about the temperature of the oceans, and observe what’s happening in the earth’s glaciers and discover the different types of ice in the universe. 

Satellites help meteorologists study the weather and also about big storms like hurricanes, cyclones, etc.

So, not only scientists use satellites, we as a person, with the help of our cell phones, also use the satellite for detecting our location’s week-wise weather and Maps for tracking the location. 

The Fun Fact

The biggest planet rotating around the earth is NASA’s International Space Station, it is as huge as a soccer/football field.

                          

Usually, six astronauts reside in this station for about six months to perform cool science experiments, which isn’t possible on the earth. 

The interesting thing is, you can view this satellite in the dark nights as a point of light continuously (with no blinking) moving steadily as a straight line all around the sky. 

Projectile Nature of a Satellite

The projectile nature of a satellite is because of the force of gravity. It’s because when a satellite is launched in space, the only governing force for the satellite’s motion is the force of gravity.

To keep the satellite in space, it is required to maintain a balance between gravity and velocity because the earth’s gravitation is pulling it down and at the same time it is speeding forward just like a cannonball firing.   

                          

To keep this satellite at the desired altitude, we must learn about the orbital velocity. So, when the satellite is close to the earth, it must travel faster to escape the earth, otherwise, it will fall into the earth (when the launching speed = 8000 m/s).

When a satellite is launched at a speed equal to 8000 m/s, it orbits the earth in a circular path. 

                             

Further, increasing the speed, the satellite makes an elliptical path around the earth.