As shown in figure when statelite S revolves, it covers a complete circular belt on earth's surface for communication. If the colatitude of the farthest point on surface upto which singals can be received (point P) is then we have
During revolution satellite leaves two spherical patches 1 and 2 on earth surface at north and south poles where no signals can be transmitted due to curvature. The areas of these patches can be obtained by solid angles
The solid angle subtended by a patch on earth's centre is
Thus total area on earth's surface to which communication can be made is
