Abstract: A sensor for measuring disturbances to an electrostatic field caused by the intrusion of a charged body or a charge producing body. The sensor employs at least two probes displaced from each other which have attached beads of radioactive material to provide free ions in the vicinity of the probe. The free ions enhance the signal created by each probe when it is affected by a disturbance in the electrostatic field in which it resides. The signals thus created are conditioned for transmission to a differential amplifier which combines them and produces an output signal which represents the detection of an intruding charged body, its distance, and its characteristics. The sensor can be configured with more than two probes seeded or placed in an array and a computer for real-time selection of the two yielding optimum signals for charged body location, velocity, direction of travel, and electrostatic signature.