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Re: [Orekit Users] Problem when doing propagation from different point of views
Le 20/03/2014 09:53, Quentin Nénon a écrit :
> Hi,
>
> I would like to complete my answer of yesterday. What I called
> "differential accelerations" is just taking into the relative
> acceleration of the two frames.
>
> You will find enclosed a new main class, step handler and a "MyChart"
> class for the plots. I modified a little the step handler and the main
> and you now have the plots of the difference of position and speed
> between the two propagators over the time.
Hi Quentin,
I will only be able to look at this in a few days, I am very busy with
some urgent matters right now.
Sorry for the delay
Luc
>
> I am using the jfreechart-1.0.17 and jcommon-1.0.21 libraries for the
> plots. You will find enclosed the jar files that should be linked to the
> project to have the plots.
>
> Hope this can help.
>
> Thanks again,
>
> Quentin
>
>
> 2014-03-19 16:10 GMT+01:00 Quentin Nénon <q.nenon@gmail.com
> <mailto:q.nenon@gmail.com>>:
>
> Thanks again for the fast answer.
>
> You will find enclosed a MyStepHandler class and a new main class
> that is using this step handler to keep the positions with an output
> step of 1000 secondes (you can modify it in the main class if you
> want). I then write the results in a txt file that I am then used to
> visualize using Excel. I can create charts if you want.
>
> I already tried to verify that the problem was not due to the fact
> the the Earth EME2000 Frame is not inertial. It seems to already be
> taken into account by using differential accelerations for the
> ThirdBodyAttraction rather than the actual acceleration created by
> the perturbative body. It means that the acceleration due to the Sun
> perturbation in the Earth Frame is equal to the acceleration of the
> satellite due to the Sun in the Sun frame MINUS the acceleration of
> the Earth due to the Sun in the Sun Frame. If the Earth Frame was
> inertial, the acceleration of the Earth in the Sun Frame due to the
> Sun would be 0. and the acceleration of the satellite would be the
> same in the Earth and Sun Frame.
>
> Moreover, if the Earth motion around the Sun was not taken into
> account, much bigger errors would be expected and all the
> propagations in the EME2000 would be (I think very) wrong.
>
> Thank you,
>
> Quentin
>
>
> 2014-03-19 15:35 GMT+01:00 MAISONOBE Luc <luc.maisonobe@c-s.fr
> <mailto:luc.maisonobe@c-s.fr>>:
>
> Hi Quentin,
>
> Quentin Nénon <q.nenon@gmail.com <mailto:q.nenon@gmail.com>> a
> écrit :
>
>
> Hi Orekit users,
>
> First, let me thank Luc very much for the very fast and
> effective answer he
> gave to my last topic. It is very nice and enjoyable to have
> support and
> suggestions from the Orekit developer team and users.
>
>
> Thanks a lot.
>
>
>
> I have another issue I would like to submit to the Orekit
> users. I am
> trying to use Orekit to propagate an interplanetary
> trajectory and in
> order to have the best possible precision, I am creating a
> manager of
> sphere of influence. The goal is therefore to be able to
> propagate the
> motion of the spacecraft in different frames (first, in
> inertial frames).
>
> You will find enclosed a main class that is doing the
> propagation of the
> same motion but from two different point of views :
>
> -The first one is to consider that the spacecraft is turning
> around the
> Earth central body and has newtonian perturbations coming
> from the Sun and
> from the Moon
> -The second one is to consider that the spacecraft is
> turning around the
> Sun central body and has newtonian perturbations coming from
> the Earth and
> from the Moon.
>
> I am using the Orekit physical data available on the Orekit
> website. I have
> Orekit 6.1 and commons math 3.2 as dependances.
>
> At the end of the two propagations, I have a difference in
> the position of
> about 2800 kilometers, that is not very good ... I verified
> with my own
> patch that it is not a problem due to the distances between
> the celestial
> bodies (see the EarthMoonBarycenter topic).
>
> Does anyone has an idea of why I have this result ? Am I
> doing a mistake
> when I am adding the force models to the propagators ?
>
>
> I just skimmed over the code and did not see any obvious error.
> Could you store not only the final position but a few hundreds
> intermediate points at fixed date (you can use an
> OrekitFixedStepHandler for that) and create a plot showing the
> error evolution throughout the propagation?
>
> I wonder if the problem could not be related to the fact Earth
> frame is not really inertial (due to motion around Sun) and in
> this case it shows up.
>
> best regards,
> Luc
>
>
> Thanks again,
>
> Quentin
>
>
>
>
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