Evan, I tried similar method using the reference you gave. But unfortunately, TLEPropagator is causing some error. Here is the code I used: 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) numpropA = fitter.convert(propagator_tleA, 2*T_objA, 251, "central attraction coefficient") and the error it says is: JavaError: org.orekit.errors.OrekitException: reset state not allowed Java stacktrace: org.orekit.errors.OrekitException: reset state not allowed at org.orekit.propagation.analytical.tle.TLEPropagator.resetInitialState(TLEPropagator.java:473) at org.orekit.propagation.conversion.AbstractPropagatorConverter.createSample(AbstractPropagatorConverter.java:265) at org.orekit.propagation.conversion.AbstractPropagatorConverter.convert(AbstractPropagatorConverter.java:149) Can you comment on this? Thank you. Regards, From: Ward, Evan On Wed, 2017-03-29 at 09:41 -0400, Justin Leblanc wrote: > Hello Evan, > > Thank you for your time. I never tried PropagatorConverter yet, but I > cam across it earlier. I would give a try now. But it would be more > helpful if I have an example or more likely a > "PropagatorConverterTest" to avoid programming errors also I could > get a rough idea about timeSpan and nbpoints. Is it possible that you > can provide me a sample code? Try taking a look at [1]. It is part of the examples that come with the library source. This particular example is converting from a NumericalPropagator to a KeplerianPropagator, but the principle is the same. Best Regards, Evan [1] https://www.orekit.org/forge/projects/orekit/repository/revisions/m aster/entry/src/tutorials/java/fr/cs/examples/conversion/PropagatorConv ersion.java > > Thank you again for your help. > > Regards, > Justin > > On Tue, Mar 28, 2017 at 4:12 PM, Ward, Evan <Evan.Ward@nrl.navy.mil> > wrote: > > Hi Justin, > > > > Welcome to Orekit.On Tue, 2017-03-28 at 21:01 +0200, justin4leb@gma > > il.com wrote: > > > Hello All, > > > > > > I am new in using OREKIT. I was wondering if its possible to > > mimic > > > TLEPropagator by incorporating similar force models into a > > Numerical > > > propagator. Basically, I am trying to replicate the results of > > the > > > "Satellite > > > Orbital Conjunction Reports Assessing Threatening Encounters in > > > Space" (SOCRATES) that are given in the celestrak > > > website :http://celestrak.com/cgi-bin/searchSOCRATES.pl?IDENT=NAM > > E&NA > > > ME_TEXT1=&NAME_TEXT2=&ORDER=MINRANGE&MAX=10 > > > > > > I am able to get exact (very closer : +/-0.1 seconds) closest > > > approach > > > results, but not with a Numerical Propagator (with J2 > > perturbations). > > > I am > > > aware TLEprop is based on SGP4/SDP4 model but I wonder if it is > > > possible to > > > bring that model into Numerical. Because I would like to > > experiment > > > by > > > applying small delta-Vs to the state to increase the closest > > approach > > > distance > > > which cannot be done within a TLEPropagator. > > > > Try taking a look at the propagation.conversion package, > > specifically > > the PropagatorConverter and PropagatorBuilder. While you won't be > > able > > to recover the exact initial condition used to create the TLE > > (TLE's > > are a form of lossy compression) it should match to the accuracy of > > the > > TLE theory. You'll probably need to experiment with the timeSpan > > and > > nbPoints parameters to fit your use case. > > > > Best Regards, > > > > Evan |