# How are geostationary satellites used for communication?

They are placed so that the orbitals speed will be same with Earth.

#### Explanation:

So they remain above same place on earth 3 Such satellites can cover the whole earth for communication..THey can be used as relay station for TV, and other communications covering whole world..
Picture credit slideshare.net.

Aug 15, 2016

Relative to the Earth, geostationary satellites remain stationary ( at rest ), vertically above a point on the Earth's surface.

#### Explanation:

Geostationary satellites have period of rotation about Earth's center

as 1 day. They are placed at an altitude of about 35800 km, The

orbit direction relative to the Earth synchronizes with that of the

Earth's day/night spin. They remain stationary ( at rest, relative to

the Earth, ) vertically above a point on the Earth's surface.

They can receive and transmit signals from a part of the the Earth's

surface in the form of a spherical cap that is symmetrical about their

verticals.

For the altitude 35800 km, the spherical cap subtends a conical

angle

${\cos}^{- 1} \left(\frac{6378}{6378 + 35800}\right) = {81.30}^{o}$ at the center of the

Earth.

Conical angle $2 \pi = {720}^{o}$ covers the entire spherical surface.

So, the proportion of the Earth's surface covered by one such

satellite

=81.30/720 X 100%=11.29%.

Tesselation (dividing the surface into caps without gaps) is not

possible.

To cover the entire globe, overlapping cannot be avoided. .