The gravitational potential energy of a satellite at a distance $r$ from the centre of earth is, \[P.E.=-\frac{GMm}{r}\]

In circular orbit, the radius $r$ is constant. Hence, P.E. remains constant.

Also, the speed of the satellite does not change. So, K.E. $\left(\frac{1}{2}mv^2\right)$ also remains same.