Hello reader!! I will be discussing Orbits in this article. If you are new to space science, I would like to recommend you to go through the previous article for a better understanding.

In the last article we got a new term, ‘Orbit’. What is an orbit?... How does it look like?... You may arise many more questions. So, let’s find out.

What is an Orbit?

An orbit is a path that is repeatedly followed by an object to move around another object in space. As you know, the earth rotates around the sun and the moon rotates around the earth. Each of them follows a particular path. These paths are called orbits.

How does an Orbit look like?

An orbit is a path to be followed. So, it can be considered as an imaginary line. Now, what is the shape of this path??.... It is elliptical (flattened circle) in shape. In some cases, it is nearly a circle, and sometimes it is highly eccentric. Comets have highly eccentric orbits.

  The object that follows the orbit is called a Satellite. It may be natural (Moon) or Artificial.

How does an object stay in Orbit?

If an object is in motion in an orbit it remains in the same orbit unless it is pushed or its motion is disturbed.

Now we are in a good position to discuss earth’s orbit.

You know about the Universal Gravitational Law, proposed by Sir Isaac Newton. Yes… I am talking about that theory which started with that Apple Incident. According to that theory, every object attracts another object with a certain amount of force. This force is termed as Gravitational Force.

What happens if you push a ball in Direction 1???.... It tends to move in the same direction...

But, what happens if you push the ball in both directions 1 and 2 at the same time??...... Yes, the ball tends to move in another direction between directions 1 and 2 as shown in the picture. This Motion is called Resultant Motion as it is the combined result of these two acting forces.

Now, when an object is in motion, it tends to move in the straight path. But Earth attracts the object with some force which tends the object to move towards the earth. So, the resultant motion will be in a direction between these two motions. This resultant motion makes the object to stay in the same orbit. Without any push, it will always remain in the same orbit.

Types of earth's orbit:

Any path that can be followed to move around the earth, is Earth's Orbit. They can be classified depending upon their orientation & distance from the center of the earth.

The angle between the orbit & the earth's equator is termed as Orbital Inclination

 The plane on which the orbit lies is termed as Orbital Plane.

If the orbital inclination is nearly 90 degrees, the orbit passes almost above both the poles of the earth. This orbit is termed as Polar Orbit.

If the orbital inclination is 0 degree, the orbit lies on the equatorial plane of earth. This orbit is termed as Equatorial Orbit.

Now, we know, the earth rotates on its own axis and it takes 24 hours to complete one rotation, which is termed as Solar Day.

But the actual time period is a little lesser, to be precise it is 23 hours 53 minutes 4.091s. This time period is termed as Sidereal Day.

Now imagine, if you can place an object in an orbit whose orbital period is exactly the same as sidereal day, it will be stationary with respect to a particular longitude on earth. As the rotation of the object in this orbit is synchronized with the earth's rotation, this orbit is known as Geosynchronous Orbit.

If the Geosynchronous Orbit lies on the equatorial plane, it is known as Geostationary Orbit. The height of the Geostationary Orbit is approximately 35,786 km from the earth's surface.

To move an object from an orbit to a larger orbit in the same plane, the object needs to be pushed by some means. The intermediate orbit is termed as Transfer Orbit.

Do you know about the GSLV and PSLV??

Those are Launch Vehicles operated by the Indian Space Research Organisation. GSLV stands for Geosynchronous Sattelite Launch Vehicle and PSLV stands for Polar Satellite Launch Vehicle.

Now you have some idea about the significance of the words Geosynchronous and Polar.

That's enough for this article.

If you ever witnessed any Launch, you have heard of these phases :-

"First Stage Separation Complete"

"Second Stage Ignited"

"Second Stage Separation Complete"

Ever thought about their meanings??