Hi Bryan,

I’ve downloaded the version you mentioned and everything seems to work just fine for the partial derivatives. Nevertheless I still get an error when it comes to propagate the state.

I feel like it is due to the fact that I’m using a `NumericalPropagator`

which I define as follow, with `orbitType = OrbitType.CARTESIAN`

and `angleType = PositionAngle.TRUE`

:

```
public NumericalPropagator setUpRK4Propagator(OrbitType orbitType, PositionAngle angleType, double stepSize, ForceModel ... models) throws OrekitException {
final double step = stepSize;
NumericalPropagator p = new NumericalPropagator(new ClassicalRungeKuttaIntegrator(step));
p.setOrbitType(orbitType);
p.setPositionAngleType(angleType);
for (ForceModel model : models) {
p.addForceModel(model);
}
return p;
}
```

And then I’m initializing the propagator with `AbsolutePVCoordinates`

:

```
AbsolutePVCoordinates pvc = new AbsolutePVCoordinates(iniState.getFrame(), pvCoordinates);
propagator.setInitialState(new SpacecraftState(pvc));
```

But I get the following error once I try propagating:

```
Exception in thread "main" org.orekit.errors.OrekitIllegalStateException: orbit not defined, state rather contains an absolute position-velocity-acceleration
at org.orekit.propagation.SpacecraftState.getOrbit(SpacecraftState.java:577)
at org.orekit.propagation.numerical.NumericalPropagator$OsculatingMapper.mapStateToArray(NumericalPropagator.java:458)
at org.orekit.propagation.integration.AbstractIntegratedPropagator.createInitialState(AbstractIntegratedPropagator.java:514)
at org.orekit.propagation.integration.AbstractIntegratedPropagator.propagate(AbstractIntegratedPropagator.java:457)
at org.orekit.propagation.integration.AbstractIntegratedPropagator.propagate(AbstractIntegratedPropagator.java:414)
at org.orekit.propagation.integration.AbstractIntegratedPropagator.propagate(AbstractIntegratedPropagator.java:397)
```

Should I be using another class of Propagator? My goal is to handle trajectories around Lagrangian points where orbits cannot be defined with keplerian or equinoctial parameters.

Would you know where my error is coming from?

Thank you very much!

Kind regards,

B.