Proposal to Extend JPLEphemeridesLoader to Support Libration Data

The org.orekit.bodies.JPLEphemeridesLoader provides methods to load ephemerides of major planets and is available in the default data context, offering a convenient option for Orekit users. However, JPLEphemeridesLoader currently ignores the libration data records in the JPL DE ephemeris series. Given that the loader already supports reading, retrieving, and interpolating planetary ephemerides, extending it to also support libration data should be feasible.

A discussion on this issue is linked here.

There is also a previous Issue 778 concerned the out-dated data in PredefinedIAUPoles.java. While loading libration from a JPL ephemeris is a recommended practice in GCCRE 2015, it could be more complicated by a fully refurbished PredefinedIAUPoles.