Orbital state vectors

In astrodynamics and celestial dynamics, the orbital state vectors (sometimes state vectors) of an orbit are cartesian vectors of position (${\displaystyle \mathbf {r} }$) and velocity (${\displaystyle \mathbf {v} }$) that together with their time (epoch) (${\displaystyle t\,}$) uniquely determine the trajectory of the orbiting body in space.

State vectors are defined with respect to some frame of reference, usually but not always an inertial reference frame. One of the more popular reference frames for the state vectors of bodies moving near Earth is the Earth-centered equatorial system defined as follows:

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