The keplerian orbital elements and position of GEO satellite extracted from given the satellite's TLE orbital elements from a source like Celestrak using the most recent version of SGP.
Keplerian elements describe these non-inertial trajectories. An orbit has two sets of Keplerian elements depending on which body is used as the point of reference. The reference body is called the primary, the other body is called the secondary. The primary does not necessarily possess more mass than the secondary, and even when the bodies are of equal mass, the orbital elements depend on the choice of the primary.
The main two elements that define the shape and size of the ellipse:
- Eccentricity - shape of the ellipse, describing how much it is elongated compared to a circle.
- Semimajor axis - the sum of the periapsis and apoapsis distances divided by two. For circular orbits, the semimajor axis is the distance between the centers of the bodies, not the distance of the bodies from the center of mass.
Two elements define the orientation of the orbital plane in which the ellipse is embedded:
- Inclination - vertical tilt of the ellipse with respect to the reference plane, measured at the ascending node (where the orbit passes upward through the reference plane).
- Longitude of the ascending node - horizontally orients the ascending node of the ellipse (where the orbit passes upward through the reference plane) with respect to the reference frame's vernal point.
- Argument of periapsis defines the orientation of the ellipse in the orbital plane, as an angle measured from the ascending node to the periapsis (the closest point the second body comes to the first during an orbit).
- Mean anomaly at epoch defines the position of the orbiting body along the ellipse at a specific time (the "epoch").