MAD
Magnetic Anomaly Detector
Magnetic Anomaly Detector is an airborne sensor that detects subtle distortions in the Earth's magnetic field caused by the large metal hull of a submerged submarine.
A Magnetic Anomaly Detector (MAD) is a passive sensor mounted on maritime patrol aircraft and helicopters that detects the slight perturbation in Earth's magnetic field caused by the ferromagnetic mass of a submarine's steel hull. Because the sensor must be very close to the target to detect these subtle anomalies, typically within a few hundred meters, MAD is used for final localization of a submarine whose approximate position has already been determined by sonar or other means.
MAD sensors are typically mounted on a boom or towed body extending from the rear of the aircraft to isolate them from the aircraft's own magnetic signature. The P-3 Orion and its successor, the P-8 Poseidon, both carry MAD equipment, as do many allied maritime patrol aircraft. The sensor is purely passive, meaning the submarine has no warning that it is being detected by MAD.
Modern submarines are increasingly built with non-magnetic materials and degaussing systems that reduce their magnetic signature, making MAD detection more challenging. However, no submarine can completely eliminate its magnetic signature, and MAD remains a valuable tool in the anti-submarine warfare sensor suite, particularly for confirming the presence and exact position of a submarine before weapons release.
Related Terms
Sonobuoy
A small expendable sensor dropped from aircraft into the water that listens for submarine sounds and transmits the acoustic data back to the aircraft via radio.
SOSUS(Sound Surveillance System)
Sound Surveillance System is a network of underwater listening arrays on the ocean floor, originally designed to detect Soviet submarines by their acoustic signatures during the Cold War.
Towed Array Sonar
A long cable containing hydrophones towed behind a submarine or surface ship, providing passive acoustic detection of other submarines and ships at ranges far exceeding hull-mounted sonar.
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