https://en.wikipedia.org/wiki/Cassini–Huygens
Orbital parameters
Reference system
Kronocentric
It's from Wikipedia.
And what do you think about Cassini–Huygens probes, did you knew instrumentation for Huygens probe that landed on Titan moon of Saturn was created by scientists from Polish Academy of Science
https://poland.pl/science/achievements-science/polish-technology-outer-space/