Hi!
I am looking for some deep analysis of the Ekcstein - Hechler propagation such as for example the perturbations involved and how they have been implemented in the propagator. Does anyone know where to find this information?
Thanks in advance!
Welcome to the Orekit forum! 
Eckstein-Hechler models the zonal harmonics from J2 to J6 (with J2-squared second order term) as well as the tesseral harmonics. It doesn’t take into account point-masses perturbations like luni-solar attraction or non-conservative perturbations like atmospheric drag or the solar radiation pressure.
The Orekit’s implementation of the Eckstein-Hechler propagator only models the zonal harmonics, not the tesseral ones.
The main drawback of the Eckstein-Hechler model is its domain of applicability. This model is suited for near circular orbits (ecc < 0.1) and and inclination neither equatorial nor critical.
Please note that Orekit has another analytical orbit propagator: the Brouwer-Lyddane. This model takes into account the zonal harmonics from J2 to J5 (with J2-squared second order term). The main advantage compared to the Eckstein-Hechler model is that it is not limited in terms of orbital elements. In other words, it can works for eccentricity greater than 0.1 and all inclination values.
An important information, if you want to use the Brouwer-Lyddane model, please use Orekit version >= 11.3.1.
In conclusion, Brouwer-Lyddane and Eckstein-Hechler model are not very differents in Orekit implementations. The first one has the zonal harmonics from J2 to J5 while the other one from J2 to J6. Brouwer-Lyddane works for any orbit type while Eckstein-Hechler is limited in terms of orbital elements.
Best regards,
Bryan
1 Like