Why are geostationary satellites not useful for studies of polar regions ?

Explanation

(i) Satellites revolving around the earth with the time period same as that of rotation of earth are called geostationary satellites.
(ii) These satellites revolve in orbits parallel to the equator of the earth at height of around 35780 km from the surface of the earth .
(iii) As, the orbits of such satellites are not useful for studies of polar region.