An Etymological Dictionary of Astronomy and Astrophysics
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An asteroid moving around the Sun having the same mean motion and mean → longitude as a planet, but a different → eccentricity. The asteroid remains near the planet much like a satellite even when its distance is large enough so that it is well outside the planet's → Hill sphere. The quasi-satellite motion is one class of possible → co-orbital motions of small bodies in 1:1 mean-motion → resonance with a planet. If the quasi-satellite orbit is coplanar with the planet, then the motion is stable in the → secular approximation. When the orbits are inclined enough, an asteroid can be trapped into such a motion for a finite period of time. Earth has several quasi-satellites (mainly 3753 Cruithne, 2002 AA₂₉, 2003 YN₁₀₇), also does Venus (the only one so far discovered, 2002 VE₆₈). The possibility of such orbits was first suggested by J. Jackson (1913, MNRAS 74, 62).

The term quasi-satellite was first used by S. Mikkola & K. Innanen 1997, The Dynamical Behaviour of our Planetary System; Proceedings, p. 345); → quasi-; → satellite.