A Satellite revolves around a planet in different orbits under the gravitational force of the planet. Here first we will
For a stable circular motion around planet, a satellite requires necessary centripetal force which is provided by the gravity of the planet. At a specific altitude when a satellite revolves, then in the given orbital radius of the satellite, which is equal to sum of planet radius and altitude, a specific speed in satellite can deploy it in a stable orbit, at which gravitational force on satellite due to planet’s gravity will exactly provide the centripetal force required for its circular motion.
The same can also be explained in the frame of the satellite by using centrifugal force which balances the gravitational force by the planet. Watch the video below for the explanation of concept and calculation of orbital speed of satellite: