IMHO, the most important before doing any refactoring, is to clearly explain the motivation.
Having a clean organisation, easy to understand is a good motivation. But it is just a convention, quite subjective and could be discussed over and over.
Finding a technical motivation could be a good allied.
For example, classes in the same package can see each-other more easily (no import, dedicated visibility of class-members). An other idea is that Orekit is currently a monolithic component. Using packages in a given way can let prepare a modularization (for example, why should I bring Earth related classes when I’m creating a deep-space software?).
So, depict a rule, draw a line and let’s go!