I'm trying to take into account the Earth geopotential effect on the orbit. The only term I could consider, is
- Are the terms (J2, etc.) change with time?
I found other terms coefficients here. How to add them also to differential equation?
The shown equation gives 1 km error in comparison with GMAT, where degree 2 and order 0 is chosen for JGM-3 model. Is it due to the change of the term with time, which I didn't consider?