A satellite S is moving in an elliptical orbit around the earth. The mass of the satellite is very small compared to the mass of the earth :
The acceleration of S always directed towards the centre of the earth
Force on satellite is always towards earth, therefore, acceleratio of satellite S is always directed towards, centre of the earth. Net torque of this gravitational force F about centre of earth is zero. therefore, angular
momentum (both in magnitude and direction) of S about centre of earth is constant throughout. Since, the force F is conservative in nature, therefore mechanical energy of satellite remains constant. speed of S is
maximum when it is nearest to earth and minimum when it is farthest.