An artificial satellite in general can be thought of travelling in a circular orbit, for simplicity sake, around Earth. Then its velocity is constant in magnitude and it varies continuously in direction.
In a circular orbit, if you mean the magnitude of velocity -- it is a constant.
In reality the artificial satellites revolve in an elliptical orbit, then the speed as well as the direction change continuously. The speed is largest when the satellite is nearest and lowest when the satellite is farthest.