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


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.



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

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


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 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



 ... 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,
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,
c20, c30, c40, c50, c60);

Is there a better way to convert osculating parameters to mean

Lara Hué

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