[Orekit Developers] Feature #34 (Getting the acceleration computed by a ForceModel)

[Tanguy Yannick <Yannick.Tanguy@cnes.fr>]

Hello,

This email follows the discussion about feature #34.

Thanks Luc for your advice. 
In fact, the modifications we made are very closed to what you say (there was a mistake in my previous message on the bug tracker) : 
- the ForceModel interface is modified to provide a new method ("Vector3D computeAcceleration(SpacecraftState s) throws OrekitException;"). All the force models must implement this method, and the "addContribution(...)" method will often use it for its own purpose.
- some force models (newtonian attraction, droziner & cunningham, third bodies attraction) provide another method ("computeAcceleration(final PVCoordinates pv, final Frame frame, final AbsoluteDate date)") : this allow easier validation.
- for the other force models (dissipative force models : sun radiation pressure and atmospheric drag), the problem is different because we need to fix some vehicule characteristics (shape, mass). So the modification we made is only used for validation purpose and should stay in a derived class.

Best regards,

Yannick