Re: [Orekit Users] Mimic TLEPropagator with Numerical?

["Ward, Evan" <Evan.Ward@nrl.navy.mil>]

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