Re: [Orekit Users] Using Orekit to obtain gravitational acceleration at specified point (with python wrapper)

[MAISONOBE Luc <luc.maisonobe@c-s.fr>]

Dominik Roszkowski <dominik003@gmail.com> a écrit :

> Hello everyone!

Hi Dominik,

> I do a little project related to gravity field modelling. At the moment I
> achieved to write a script in Matlab calculating gravitational acceleration
> by Cunnigham's method based on an arbitrary gravity field model file from
> ICGEM. I would like to compare results with Orekit library's package
> 'org.orekit.forces.gravity'.
> The only thing I need is to have from Orekit is the value of acceleration
> for specified point in Cartesian coordinate system calculated with all
> three models available in Orekit. Could you help me and guide me how to
> obtain these? I would appreciate any hints.

You can look in the junit tests part of the library. In the Jacobianizer.java
file, there is an internal class AccelerationRetriever which implements
TimeDerivativesEquations. You can just copy this internal class into
your project. Then create an instance and pass it to the addContribution
method of the force model (Holmes-Featherstone, Cunningham, Droziner,  
whatever),
together with a SpacecraftState that correspond to the position where your
spacecraft is and where you want to check the acceleration. The  
AccelerationRetriever
instance will pick up the acceleration, and you can get it afterwards. This
class is used specifically for validation purposes.

best regards,
Luc


> I use Python 2.7 wrapper for Orekit through Anaconda on 64bit Windows 10.
> Regards,
> Dominik