March 5 and 6, 2011. Île Longue, Brest.
Nuclear submarine (SSBN) nuclear missile launcher Le Terrible.
The submarine departs on its first mission of deterrence.

Maneuver by hand of the towed linear antenna (ALR : Antenne Linéaire Remorquée)
which is used for passive listening (ETBF : Ecoute Très Basse Fréquence.)

The very long antenna (1 000 meters / about 3300 feet) will remain deployed at the rear of the submarine throughout navigation to allow it to capture with great precision all the sounds and frequencies emitted under water.
The antenna itself does not transmit a single frequency or sound that would bounce off the ocean floor or other obstacles before echoing back toward the boat as would other active antennas as a sonar, more familiar to the general public.
This antenna only listens passively with incredible precision and according to the technical criteria specific to each nation, which is thus highly protected.