When light passes into another material like glass or water, refraction causes it to bend. However, all the colors of light do not bend the same amount. At one end of the spectrum, red light bends the least, while at the other end, blue and violet light bend the most.
Twenty-four of Saturn's moons are regular satellites; they have prograde orbits not greatly inclined to Saturn's equatorial plane.
GPS stands for Global Positioning System. The system is made up of at least 24 satellites orbiting the Earth. The satellites communicate with specialized receivers on the ground, providing the exact position of the receivers. As of this writing, there are 31 operational satellites in the GPS constellation. Put in place by the US military starting in 1989, the GPS satellite constellation transmits a signal for its own use and a separate signal that anyone with the technological wherewithal is free to access.