Potential collisions are flagged for monitoring if there’s simply a high probability of conjunction. Typically, the probability goes down after a couple of additional days of tracking, but in rare cases this doesn’t happen (and, in a few, the probability went up with further monitoring). When the probability doesn’t go down, the software can calculate a maneuver that will reduce the probability of collision to an acceptable level. The solution will take into account other potential hazards as well as mission requirements—some Earth-monitoring satellites can’t orbit above a certain altitude and still perform their jobs.

via Saving Fermi: NASA’s system for avoiding collisions with space junk | Ars Technica.