We know that orbital velocity of a satellite, revolving near the earth surface, is nearly 8 km s-1. If an object is projected from the top of a tower of height nearly 300 km, with velocity less than v0 in a horizontal direction, then it falls under gravity and adopting a parabolic path it reaches any point on the earth, but if it is projected with velocity equal to v0 in horizontal direction, then it never strikes the earth. Therefore, we can say that the object tries to strike the ground falling freely under gravity but remains fail to do so. As a result, the object will start moving in a circular path and it becomes an artificial satellite. This is the principle of establishing an artificial satellite.
To establish an artificial satellite in orbit, it is projected vertically upward by multistage rocket so that it may cross the dense atmosphere of the earth in minimum time. There is automatic arrangement in rocket due to which the rocket takes turn in horizontal direction just after crossing the earth’s atmosphere and the satellite is left in horizontal direction with the help of a spring and the rocket gets established in its orbit. Thus the rocket starts revolving around the earth. It is important to remember that the rocket should remain out of the earth’s atmosphere otherwise due to high friction in atmosphere the rocket will get destroyed due to heat.
Uses of Artificial Satellites:
- These satellites are used for investigation of other countries and to know the location of enemy during war.
- These are used to study the radiations coming from the Sun and cosome.
- These are used to know about the weather.
- Information regarding the size of planets is obtained with the help of these satellites.
- Pilots get guidance of direction with the help of these satellites.
- Study of various layers of atmosphere is done by these satellites.
