I want to extract the Chebyshev coefficients in order to be able to calculate the time-varying transformation from the ICRF / J2000 Inertial frame to the Moon ME (moon mean earth) frame. I know I can use spiceypy and the associated PCK & FK files to get the rotation matrices at any time but I want a general expression for the transformation in our code since we can't implement the entire SPICE code in our software.
Is there a way to find the coefficients within the SPICE binary PCK? If not, can I possibly get rotation matrices at particular times and then interpolate that to get the Chebyshev? I'm not an expert here and any assistance or other suggestions would be appreciated.
This is what I have been reading: https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/Tutorials/pdf/individual_docs/23_lunar-earth_pck-fk.pdf