# Is it possible to determine the classical orbital elements for an Elliptic Repeating SSO?

As in the title, it is possible to have a repeatable Sun-synchronous orbit but with an elliptic eccentricity?

If yes, which equations I have to consider to determine its classical orbital elements?

• You used the term "classical orbital elements". Do you mean "Keplerian orbital elements" or "osculating orbital elements"? There is no such thing as a Sun-synchronous orbit in classical/Keplerian/osculating orbital elements because the right ascension of ascending node is fixed (as are all of other classical orbital elements except for mean anomaly). You'll need to use some non-classical orbital element set, or an orbital element set in which right ascension of ascending node, argument of periapsis, inclination, semi-major axis length, and eccentricity can change. Commented Jun 28, 2022 at 20:49
• Thank you for your answer, I mean Keplerian Orbital Elements which in commercial softwares (such as STK) are called classical orbital elements. In fact I want a set of equations that allows me to calculate the sma, ecc, inc, RAAN, Aop and TA. I already have ones for the case of a circular repeating SSO, with which I computed a set of elements and defined an orbit which works well in simulations with simple approximation of only J2 Perturbation. However the ground track is not regular when I try to do the same with an elliptic orbit. And that's the reason behind the question. Commented Jun 29, 2022 at 7:23
• PS I disagree about the fact that the keplerian elements remain constant for a SSO cause for definition a SSO has a mean RAAN rate (due to J2 perturbation) which is equal to the one of the Sun. Maybe I didn't understand what you mean for fixed orbital elements. Commented Jun 29, 2022 at 7:30