Re: [Orekit Users] Using EGM96 with DSSTPropagator

[Evan Ward <evan.ward@nrl.navy.mil>]

Hi Joseph,

My guess is that you need to add the EGM96 spherical harmonics
coefficients to your Orekit data path. The orekit-data.zip that I think
you're using now comes with the Eigen model, which is why you always see
those coefficients. So extract the orkit-data.zip to a directory, and
replace the eigen-6s.gfc file with egm96 file you can download from [1].
Then in your application set the orekit data path to the directory you
extracted. For more on configuring and data loading see [2]. Hope this
helps.

Best Regards,
Evan

[1] ftp://cddis.gsfc.nasa.gov/pub/egm96/general_info/egm96_to360.ascii
[2] https://orekit.org/static/configuration.html

On 03/12/2016 04:02 PM, joseph.huwaldt@dynetics.com wrote:
> I've been evaluating Orekit for use at my company.  I am very impressed.  It
> appears to be very high quality software. I do have a few questions.  Here is
> the first.
>
> I want to use the EGM96 gravity model (with the WGS84 ellipsoid) in
> combination with the DSSTPropagator.  But, I can't seem to get there.  It is
> trivial to use the EGM96 coefficients with the EcksteinHechlerPropagator, but
> I'm not seeing how to get there with the DSSTPropagator (or the
> NumericalPropagator for that matter).
>
> I see that I can use DSSTPropagator.addForceModel() to add a DSSTCentralBody
> using a UnnormalizedSphericalHarmonicsProvider to supply the gravity model.
> In the examples, that in turn is created using
> GravityFieldFactory.getUnnormalizedProvider(degree,order).  However, that
> seems to return a EIGEN-6S model.  How do I get an EGM96 model?
>
> Any help would be appreciated.  Thanks!
>
> Ad astra,
>
> Joseph Huwaldt
> Dynetics, Inc.
> Huntsville, AL