Orbital frame is used when the orbit of a body around another body is assumed to be circular. The origin is fixed to the orbiting body. The x axis points in the direction of velocity of velocity of orbiting body, z axis is directed from the orbiting body to the center of the body around which it orbits, and the y axis completes the right handed co-ordinate system (thus forming normal vector to the orbital plane). It is a rotating frame hence a non-inertial frame.

It is fixed to the body which is being analyzed. The axis can be oriented arbitrarily, but are generally chosen to be the principal axes of inertia. The body (to which the body frame is fixed) as observed with respect to the body frame is stationary. It may be an inertial or non inertial frame depending on the motion of the body. <br \> === References ===For illustrations, visit http://www.dept.aoe.vt.edu/~cdhall/courses/aoe4140/refframes.pdf.