Maybe I'm being really really dim but I still have absolutely no idea why spacecraft orbit like sine waves. All I'm seeing is that they go up and down just because they do.
Edit: thanks for everyone's responses! Turns out I am just dim, haha.
Kerbal Space Program really helps one understand orbital mechanics and space travel in general.
Some unsolicited feedback which you hopefully find constructive:
The equator is missing. This would give a firm anchor point for the eye during the transition to a projection and show the sinusoidal nature of the orbital track even better once that transition is completed. It's not super clear when the animation starts if the line near the center is equatorial or not, which leads to a bit of confusion. I feel like it's important enough that I would highlight it by width or alpha vs. the other latitude lines to give the viewer something to focus on.
The globe rotation in the beginning feels a little fast to me, and the unfurling to a flat map a little slow. The rotation really only has to be enough to show whether the rotation of the orbit is tied to the earth's axis, so the excess speed is a little jarring. I'd say that rotation could be 50% slower. As for the unfurling, I feel that we as animators often get too enamored with the neat thing we finally figured out how to do and linger on it a bit too long. The unfurling is very cool, but it could also be a third or half as long and still convey the same message, especially given a better anchor point as discussed above.
That extra time from the transition can go into a longer hold at the end. It's important to give viewers 5 or 6 seconds to absorb or ponder over what they've just watched, and this is more like a second or two before the ending wipe.
Speaking of the wipe, I'd ditch it. It's easier to do that with a mask and render as necessary for the project than to have it in the actual animation.
If this were in a 16:9 ratio, there would be a little less white space at the end, which is especially important now that so much media is viewed on smaller screens. However, the current aspect ratio is probably more suitable for embedding in a presentation or web page, so this one could probably go either way. Once again, I would render the animation in a larger size and crop as necessary to fit format.
You could also add a moving dot to the orbital track, but that may or may not clutter stuff up too much; I'd have to AB it to say for sure.
Anyway, I hope those suggestions help. Take or leave them as you like.
We need reverse gif for this, then it might be more easy . . .
When you realize sin is just a function of a straight constant line on a round object
OOHHHH!! Man, I never understood that until now! Thank you!
Also, relevant username!