Every day, orbit-determination centers screen hundreds of thousands of close approaches between active satellites and tracked debris, condensing each one into a single number: the probability of collision, Pc. This simulator walks through that pipeline end to end. Two objects — a tracked satellite and a debris fragment — orbit a 3D Earth on slightly different, crossing paths while a B-plane inset renders the actual conjunction-assessment geometry: the predicted miss distance, the combined position-uncertainty disk (grown by however far out the time-of-closest-approach horizon sits), and the hard-body threat circle. Dial in the miss distance and tracking uncertainty an orbit-determination solution might report, watch Pc spike as the encounter sharpens, then apply a small radial avoidance burn and see the same physics that lets operators nudge a real conjunction below the standard 10⁻⁴ maneuver threshold with only millimeters per second of delta-v.