NCD2539
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NCD2539 is a location of space that the Fleet know that Cylon ships use as a supply route.
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.
Sabotage to the prisoner's air supply kills them before Galactica encounters the Cylon fleet, aborting the attempt (A Measure of Salvation).