Editing Orbit (section)

===Radial, prograde and transverse perturbations===
A small radial impulse given to a body in orbit changes the [[Eccentricity (mathematics)|eccentricity]], but not the [[orbital period]] (to first order). A [[Direct motion|prograde]] or [[Retrograde motion|retrograde]] impulse (i.e. an impulse applied along the orbital motion) changes both the eccentricity and the [[orbital period]]. Notably, a prograde impulse at [[periapsis]] raises the altitude at [[apoapsis]], and vice versa and a retrograde impulse does the opposite. A transverse impulse (out of the orbital plane) causes rotation of the [[Orbital plane (astronomy)|orbital plane]] without changing the [[Orbit (dynamics)|period]] or eccentricity. In all instances, a closed orbit will still intersect the perturbation point.