@uhoh Yes! The comments are bringing very interesting information about the behavior of ISS during orbit. I wonder if more information can be extracted now with a periodogram of the error over a longer period, need to check! I actually had one of the questions about Ceres bookmarked already for getting back to it :)

Did you manage to get the gravity potential reconstructed? For Earth I'm currently using Legendre polynomials and associated functions together with the matrixes of Cnm and Snm coefficients to get the gradient of potential (and then calculate acceleration from there).

I guess maybe the same code could be directly applied to reconstruct the potential gradient for any other celestial body, just changing the Cnm and Snm matrixes (and also changing the maximum degree and order depending on available coefficients)?

solarsystemstuff.com

Still very much working on it, but... It's something at least for now.

Would be interested in any feedback.

@Rafa No I didn't. I'll look at it today and see if I can remember how far I got and where I got stuck. The problem is that there is more than one way to define the normalization of those polynomials, so unless one knows the normalization the coefficients don't mean anything.

@RoryAlsop Is the FSF (Freue Software Foundation) on thus list?