I guess I don't get why it would be an S shape even if it's a perfect-circle orbit or an ellipse flattened out (side view). Yeah I'll have to read up on that.

edit: not sure if this is related, I remember doing this thing when I was a kid, you'd spin a globe and trace a pencil straight down (a lonitude line) and it spiral out (the drawn line). To simulate Coriolis effect

edit: Oh I see depends on what it's aligned to, (equator) to create the sinusoidal look... reminds me in calc or engineering creating diagrams/charts (maybe beams and moment/force diagrams) ahhh... sucks when you don't use something and you forget. In calc you did something with max/mins and this determined the concave/convex of a curve on a graph. Ahhh rambling sorry.