Hi Romain,
The method getPVCoordinates(FieldAbsoluteDate, Frame) is not in the PVCoordinatesProvider interface but in FieldPVCoordinatesProvider (or in ExtendedPVCoordinatesProvider). That’s why you have the error.
However, JPLCelestialBody doesn’t implements the FieldPVCoordinatesProvider interface.
Therefore, could you .cast_() to ExtendedPVCoordinatesProvider? I tried and it works.
from org.orekit.utils import ExtendedPVCoordinatesProvider
...
solar_system_barycenter = ExtendedPVCoordinatesProvider.cast_(CelestialBodyFactory.getSolarSystemBarycenter())
...
Best regards,
Bryan