Re: [Orekit Developers] From osculating parameters to mean parameters for LEO orbits

[paulcefo <paulcefo@buffalo.edu>]

All,

I have started on a comment on the osculating to mean conversion. I will 
finish it later today but I wanted to send the current draft now.

regards,

Paul

--
Dr. Paul J. Cefola
Consultant in Aerospace Systems, Spaceflight Mechanics, & Astrodynamics
Adjunct Faculty, Dept. of Mechanical and Aerospace Engineering, 
University at Buffalo (SUNY)

4 Moonstone Way
Vineyard Haven, MA 02568
USA

508-696-1884 (phone on Martha's Vineyard)
978-201-1393 (cell)

paulcefo@buffalo.edu
paul.cefola@gmail.com

On 04/15/2016 7:52 am, HUE, Lara wrote:
> Hi to all,
>
> Thanks for the use of the great Orekit tool !
> My question is about the computation of mean parameters from a LEO
> osculating orbit.
> In order to get some operational parameters, I need to compute the
> mean parameters at each steps of the global propagation.
> One way is to use the OsculatingToMeanElementsConverter with a
> specific propagator.
> I tried with a classical EcksteinHechlerPropagator, however the
> following exception has been raised :
>
> Exception in thread "main" org.orekit.errors.PropagationException:
> impossible de calculer les paramètres moyens au sens de
> Eckstein-Hechler après 101 itérations
>  at
> org.orekit.propagation.analytical.EcksteinHechlerPropagator.<init>(EcksteinHechlerPropagator.java:318)
>
>  at
> org.orekit.propagation.analytical.EcksteinHechlerPropagator.<init>(EcksteinHechlerPropagator.java:200)
>
>  at main.Init.main(Init.java:91)
> Caused by: org.orekit.errors.PropagationException: impossible de
> calculer les paramètres moyens au sens de Eckstein-Hechler après 101
> itérations
>  at
> org.orekit.propagation.analytical.EcksteinHechlerPropagator.computeMeanParameters(EcksteinHechlerPropagator.java:394)
>
>  at
> org.orekit.propagation.analytical.EcksteinHechlerPropagator.resetInitialState(EcksteinHechlerPropagator.java:327)
>
>  at
> org.orekit.propagation.analytical.EcksteinHechlerPropagator.<init>(EcksteinHechlerPropagator.java:311)
>
>  ... 2 more
>
> Indeed, when calling the EcksteinHechlerPropagator constructor, it
> takes more than 100 iterations to compute mean parameters at the
> initial state, and therefore the exception is raised.
> Here is a specific orbit among others, retrieved from the simulation,
> for which the computation in mean elements is not possible :
>
> AbsoluteDate t = NEW AbsoluteDate(2016, 07, 22, 9, 35, 42.562,
> TimeScalesFactory._getUTC_());
> Frame frame = FramesFactory._getEME2000_();
> Orbit orbit = NEW EquinoctialOrbit(7075842.806163763,
> 0.0012957331188810572, -4.760791390305797E-4, 0.14011350699555794,
> -1.1457596828634813, 79339.41232985309, PositionAngle._TRUE_, frame,
> t, Constants._WGS84_EARTH_MU_);
> Double mass = 436.5;
> DOUBLE c20 = Constants._EIGEN5C_EARTH_C20_;
> DOUBLE c30 = Constants._EIGEN5C_EARTH_C30_;
> DOUBLE c40 = Constants._EIGEN5C_EARTH_C40_;
> DOUBLE c50 = Constants._EIGEN5C_EARTH_C50_;
> DOUBLE c60 = Constants._EIGEN5C_EARTH_C60_;
> EcksteinHechlerPropagator analyticalPropagatorWrong = NEW
> EcksteinHechlerPropagator(orbit, mass,
> Constants._WGS84_EARTH_EQUATORIAL_RADIUS_, Constants._WGS84_EARTH_MU_,
> c20, c30, c40, c50, c60);
>
> Is there a better way to convert osculating parameters to mean
> parameters?
> Best,
>
> Lara Hué
>
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