Let me explain to you, how the propeller structure is formed and why the waves are behind and in front of the moonlet:

When something orbits around a planet (or a star), one orbit takes the longer, the farther away the object is from that central body. Our moon orbits the earth around one time per month and the international space station, which is significantly closer, orbits our planet several times a day.

Same thing in Saturn’s rings because the ring particles follow the same fundamental equations. The ring particles that are closer to Saturn orbit the planet in a shorter amount of time than particles farther outside.

This has interesting consequences: Imagine three ring particles at three different distances from Saturn. The particle closest to the planet will orbit the planet more quickly than the middle one and the middle one more quickly than the outer one.

Let us look at an analogy: Imagine you are driving on the highway in the middle lane, you are the middle ring particle. Saturn is somewhere at the horizon to your left. Since particles (or in this case cars) that are closer to Saturn orbit the planet more quickly, the cars on the left constantly overtake you. You, however, are closer to the planet than the cars on the right lane, your angular velocity is thus higher, and you overtake them.

Now imagine you are the massive moonlet and because of its larger mass you are driving a big truck in the middle lane of the highway — maybe you should not do this in real life ;).

Ring particles or cars are overtaking you on the left and you are overtaking them on the right.

Because of your large mass, you are a small moon, after all, you are disturbing the ring particles’ motion when they are nearby, similar to how the ship disturbs the water when it passes through it. This is called gravitational scattering. However, before the cars overtake you on the left or a short while after they overtook you, they do not feel your gravitational influence (same on the right). You only exert a force onto them when they are close by. The region in which a moon (or a planet orbiting a star) dominates the motion of smaller particles is called Hill sphere.

In our analogy, you could imagine that it is a rainy day and cars that come too close to you — enter your Hill sphere — get sprayed with mud from the road. This stands for the ring particles being disturbed when they come to close to the moonlet.

Well, where would you find the cars that have been disturbed by you? On the left, the cars would be sprayed with mud after they overtook you, on the right after you overtook them.

This is the reason why the wake pattern in the rings leads the embedded moonlet on the inside (closer to the planet) and trails it on the outside.