# Satellite

## Satellite

Satellite are natural or artificial bodies of revolution around a planet under its gravitational attraction. Moon is a natural satellite while INSAT-IB is a artificial satellite of earth.

## Orbital speed of a satellite

1.   Orbital speed of a satellite is independent of its mass. Hence satellite of different masses revolving in the orbit of same radius have same orbital speed.
2.   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.
2.   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.i.e. period of revolution = circumference of orbit / orbital speed
1.   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.
2.   Period of revolution of a satellite is independent of its mass.
3.   The period of revolution of satellite revolving near the surface of earth is 1 hour 24 minute (84 minute)

## 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

Escape velocity is that minimum velocity with which a body should be projected from the surface of earth so it is goes out gravitational field of earth and never returns to the earth.
1.   Escape velocity is independent of the mass, shape and size of the body and its direction of projection.
2.   Escape velocity is also called second comic velocity.
3.   For earth, escape velocity = 11.2 Km/s
4.   For moon, escape velocity = 2.4 km/s