Air friction increases the velocity of the satellite. Explain.

Explanation

If a satellite of mass `m` is revolving in a circular orbit of radius `r`, with speed `upsilon` around the Earth of mass `M`, the centripetal force is provided by the gravitational pull, i.e.,
`(m upsilon^(2))/(r ) = (GM m)/(r^(2))` or `m upsilon^(2) r = GM m`
or `(m upsilon r) upsilon = GM m = a` constant
or `L upsilon = a` constant
Where, `m upsilon r = L` is the angular momentum of the satellite. As the air friction causes the retarding torque, it will decrease the angular momentum `L` of the satellite `upsilon` increase in order to keep `L upsilon = a` constant.