[GS] [Geography] Satellite, Orbital speed, Period of revolution, Geo-Stationary satellite & Escape velocity

[GS] [Geography] Satellite, Orbital speed, Period of revolution, Geo-Stationary satellite & Escape velocity

• Satellite: Satellites are natural or artificial bodies revolving around a planet under its gravitational attraction. Moon is a natural satellite while INSAT-IB is an artificial satellite of earth.

• Orbital speed of a satellite:

• Orbital speed of a satellite is independent of its mass. Hence satellites of different masses revolving in the orbit of same radius have same orbital speed.

• Orbital speed of a satellite depends upon the radius of orbit (height of satellite from the surface of earth). Greater the radius of orbit, lesser will be the orbital speed.

• The orbital speed of a satellite revolving near the surface of earth is 7.9 km/sec.

• Period of revolution of a satellite: Time taken by a satellite to complete one revolution in its orbit is called its period of revolution.

• Period of revolution = Circumference of orbit / orbital speed.

• Period of revolution of a satellite depends upon the height of satellite from the surface of earth. Greater the height, more will be the period of revolution.

• Period of revolution of a satellite is independent of its mass.

• The period of revolution of satellite revolving near the surface of earth is 1 hour 24 minutes.

• Geo-Stationary satellite: If a satellite revolves in equatorial plane in the direction of earth’s rotation i.e from west to east with a period of revolution equal to time period of rotation of earth on its own axis i.e 24 hours then the satellite will appear stationary relative to earth. Such a satellite is called Geo-stationary satellite. Such a satellite revolves around the earth at a height of 36000 km. The orbit of Geo-stationary satellite is called parking orbit. Arthur C. Clarck was first to predict that a communication satellite can be stationed in the geosynchronous orbit.

• Escape velocity: It is that minimum velocity with which a body should be projected from the surface of earth so as it goes out of gravitational field of earth and never return to earth.

• Escape velocity is independent of the mass, shape and size of the body and its direction of projection.

• Escape velocity is also called second cosmic velocity.

• For earth, escape velocity = 11.2 km/s.

• For moon, escape velocity = 2.4 km/s.

• Orbital velocity of a satellite V_O = √(gR) and escape velocity Ve = √(2gR)

• So we can say that escape velocity is √2 times the orbital velocity.

• Therefore if the orbital velocity of a satellite is increased to √2 times (41%),the satellite will leave the orbit and escape.