More information about the software they use https://en.wikipedia.org/wiki/Naval_Observatory_Vector_Astro...
Manual: https://aa.usno.navy.mil/downloads/novas/NOVAS_F3.1_Guide.pd...
Manual: https://aa.usno.navy.mil/downloads/novas/NOVAS_F3.1_Guide.pd...
I imagine the Python versions wraps one of the other two. But are the C and Fortran versions separate, or does one wrap the other? If not, how are they related? Parallel implementations kept in sync by hand? Used to check each other? Machine translated? Code-generated from an upstream definition?