### minimum orbit intersection distance

**(MOID)**
(smallest distance between paths of two orbiting bodies)

The **minimum orbit intersection distance** (**MOID**) is the minimum
distance between the paths of two bodies that are orbiting the same
body. It is simplified by ignoring perturbations, both
between the two bodies and from other bodies close enough to affect
them, i.e., treating their orbits as simple orbits around the central
body (termed **osculating orbits**). As such, a small MOID suggests
a chance of a future impact, and qualitatively, the smaller,
the greater chance, and its simplification makes it a
relatively-straightforward factor to calculate. It is of interest
in evaluating possible future impacts between Earth and near-Earth object,
but is also of more theoretical interest regarding the evaluation
of possible histories of orbits: too much chance of an impact
suggests an orbit could not have been the same in the distant past.

(*orbits,near-Earth objects*)
**Further reading:**

http://en.wikipedia.org/wiki/Minimum_orbit_intersection_distance

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