# 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. If you would like to contribute notes or other learning material, please submit them using the button below.

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Geo-Stationary Satellites [00:34:03]
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