keplerian converter

I'm sorry, I just open this issue again, there are 3 different ways that I have found, in Swift by Hal Levison, in mercury6 by Chambers, and Vallado. I think your algorithm is similar with Vallado (fundamentals of astrodynamics and applications)  https://gist.github.com/ridlo/c5e81c4be32f4e97ad54

In here I used the algorithm from mercury6

before and after in the case of parabolic motion (http://www.youtube.com/watch?v=T_NlGPfF7zk)