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 protected 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 V₀∫g R and escape velocity Vₑ = ∫2gR
Where R= Radious of earth i.e. Vₑ =∫2 V₀ i.e. escape velocity is
∫2 times the orbital velocity.
Therefore if the orbital velocity of a satellite is
increased to ∫2 times (increased by 41 % the satellites will leave the orbit
and escape.
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