You may be wondering why we chose a photo of NASA’s Mars Rover for the cover. We actually chose it for several reasons. Obviously, it is very exciting; in fact, space represents the most exciting frontier for the entire world! In addition, much of the Rover itself consists of all kinds of circuits. Circuits that must work without needing maintenance! Once you are on Mars, it is hard to ﬁnd a technician! The Rover must have a power system that can supply all the power necessary to move it, help it collect samples and analyze them, broadcast the results back to Earth, and receive instructions from Earth. One of the important issues that make the problem of working with the rover is that it takes about 20 minutes for communications to go from the Earth to Mars. So the Rover does not make changes required by NASA quickly.