Satellites orbit around the earth. Depending on the application, these orbits can be circular or elliptical. Satellites in circular orbits always keep the same distance to the earth’s surface following a simple law:
The attractive force Fg of the earth due to gravity equals mg (R/r) 2  .
The centrifugal force Fc trying to pull the satellite away equals mrω2 .The variables have the following meaning: m is the mass of the satellite; R is the radius of earth with R = 6,370 km; r is the distance of the satellite to the centre of the earth; g is the acceleration of gravity with g = 9.81 m/s2; ω is the angular velocity = 2πf, f is the frequency of the rotation. To keep the satellite in a stable circular orbit, the following equation must hold: Fg = Fc, i.e., both forces must be equal. Solving the equation for the distance r of the satellite to the centre of the earth results in the following equation:
The distance r = (gR2/(2πf)2)1/3  .From the above equation it can be concluded that the distance of a satellite to the earth’s surface depends on its rotation frequency. e