What are orbital elements?
Orbital elements describe a conic (most commonly an ellipse) in inertial space. They also describe an object’s state (equivalent to its Cartesian position and velocity) at a specific epoch. Typically orbital elements are used to express an object’s osculating orbit (an orbit tangent to and approximating the actual orbit) at the specified epoch. On this site, we use both Keplerian elements and so-called comet elements. Keplerian elements are eccentricity, semimajor axis, mean anomaly, inclination, longitude of the ascending node, and argument of perihelion. In some cases, longitude of perihelion is used instead of the argument of perihelion. Comet elements are eccentricity, perihelion distance, time of perihelion passage, inclination, longitude of the ascending node, and argument of perihelion.
