### How Long Does the Transfer Take?

When you use a Hohmann transfer orbit, the transfer orbit is an ellipse. How much of the
elliptical orbit is swept out in traveling from the starting point to the destination?

Using Kepler's Third Law, you can compute the period of an elliptical orbit whose semimajor axis "a" you know. You can determine the semi-major axis "a" in terms of the radius of the shuttle orbit and the radius of the GPS orbit.