Planet_plane uses eccen & omega rather than esinw and ecosw, interfering with autodifferentiation #6
Description
I've started a private branch to allow for autodifferentiation. Unfortunately, ForwardDiff can't perform autodifferentiation on atan2. If Planet_plane used esinw and ecosw, then I think I could get it to work.
@ericagol, Since changing this type would change the interface to compute_ttv!, I wanted to ask before implementing the changes. We could adjust test_ttv, so that the instructions in the current README still work.
An alternative to changing the existing Planet_plane would be to create a new type Planet_plane_hk and creating a new compute_ttv to go with it. Unfortunately, that would result in (at least) two versions of compute_ttv, creating more code maintance tasks, so I consider this the less desirable option