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Geostationary and Polar Satellites

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  • Geo-Stationary Satellites

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Geostationary Satellite:-

  • Geo means earth and stationary means at rest. This means something which is stationary.

  • Satellites orbiting around the Earth in an equatorial plane with time period equal to 24 hours.

  • Appear to be stationary with respect to earth. They also rotate around the earth with a time period of 24 hours.

  • These satellites can receive telecommunication signals and broadcast them back to a wide area on earth.

  • Example: INSAT group of satellites.

Problem:- Calculate the height of a geostationary satellite from the surface of the earth?

Answer: For any geostationary satellite time period 

T = 24hours = `24xx60xx60s`

= 86400 sec

orbital velocity `"v"=(2pi"R")/"T"`

Where R= distance of satellite from the earth. it is given as `"R" = "R"_E + "h"`

`"F"_c = "mv"^2/"R"`

`"F"_G = ("GM"_e"m")/"R"^2`

`"F"_c = "F"_G`

`"mv"^2/"R"=("GM"_e"m")/"R"^2`

By simplifying,

`"v"^2 = "GM"_e/"R"`

`=(4pi^2"R"^2)/"T"^2="GM"_e/"R"`

`"R"^3="GM"("T"^2/(4pi^2))`

Acceleration due to gravity `"g"= "GM"/"R"_E^2`

`"GM"="gR"_E^2` 

`"R"^3=("gR"_"E"^2"T"^2)/(4pi^2)`

`therefore "R"= [("gR"_E^2"T"^2)/(4pi^2)]^(1/3)`

by putting the values and calculating

R = 42147km

`"R"="R"_E + "h"`

`"h"="R" -"R"_E`

=`(42147 - 6.37 xx 10^3)`

h = 35777km

The height of the geostationary satellite from the surface of the earth is 35777km.

Polar Satellites

  • These are low altitude satellites. This means they orbit around the earth at lower heights.

  • They orbit around the earth in North-South direction. Whereas the earth is moving from East to West.

  • A camera is fixed above this type of satellite so they can view small strips of earth.

  • As earth also moves, so at each instance different types of stripes of earth can be viewed.

  • Adjacent stripes of the earth are viewed in subsequent orbits.

  • They are useful in remote sensing, meteorology and environmental studies of the earth.


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Shaalaa.com | Geo-Stationary Satellites

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