__NOTOC__ The proper orbital elements or proper elements of an orbit are constants of motion of an object in space that remain practically unchanged over an astronomically long timescale. The term is usually used to describe the three quantities:
*proper semimajor axis (a_p),
*proper eccentricity (e_p), and
*proper inclination (i_p).

The proper elements can be contrasted with the osculating Keplerian orbital elements