Evan, > Try setting fp = [] here. Yes an empty list worked. > I'm not very familiar with the python >interface to the library, but the convert function is expecting an >array or a List, not a String. Actually there are types of ways how you can pass a value for free parameters. Either to pass directly as a list of strings or a single string representing free parameter name as the method will automatically generate a list of strings based on that. The issue kind of names the free parameter can have. When I just gave random name I got an error like this: org.orekit.errors.OrekitException: unsupported parameter name “some_string”, supported names: central attraction coefficient Lastly, I assume for free parameters the value should be an empty list or a list of string names or a single string saying something like -> “central attraction coefficient”. I am curious what other free parameters we can give. Thanks to everyone who helped me out here. I managed to do the conversion. Regards, From: Ward, Evan Justin,On Thu, 2017-03-30 at 11:43 -0400, justin4leb@gmail.com wrote: > > odeIntegratorBuilder = DormandPrince853IntegratorBuilder(0.001, > 1000.0, 1.e-2) > builder = NumericalPropagatorBuilder(initialOrbitA, > odeIntegratorBuilder, PositionAngle.TRUE, 1.e-2) > fitter = JacobianPropagatorConverter(builder, 1.e-6, 5000) > fp = "central attraction coefficient" Try setting fp = [] here. I'm not very familiar with the python interface to the library, but the convert function is expecting an array or a List, not a String. > numpropA = fitter.convert(tleStates, False, fp) > Best Regards, Evan |