NCD2539
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NCD2539 is a location of space that the Fleet know that Cylon ships use as a supply route. The complete designation is "The Region of NCD2539 Above/North."
Battlestar Galactica intentionally visits this area to lure Cylon forces, including a Resurrection Ship, into the area. The Colonials intended to kill their Cylon agent prisoners, whose consciousnesses would download and infect the Cylon populace with a human virus with a bioelectric pathogen that would effectively annihilate the Cylon race.
Captain Karl Agathon's sabotage to the prisoners' air supply kills them before Galactica encounters the Cylon fleet, aborting the attempt (A Measure of Salvation).