CAPTAS-4
The CAPTAS-4 is a towed array sonar developed by Thales Underwater Systems to equip first-rank surface combatants. Manufactured in Brest, France, it represents the high-end and most powerful system of the company's CAPTAS line of products and equips several first-rank warships of the French Navy as well as those of various export customers. A British variant, known as Sonar 2087, equips anti-submarine warfare frigates of the Royal Navy.
Description
The CAPTAS-4 system comprises a UMS-4249 ultra-low-frequency active sonar with four ceramic rings, integrated into a towed variable-immersion body. Capable of diving up to, it covers a very large volume of water over an extremely long range. In addition to the UMS-4249 variable depth sonar, a towed multi-functional linear antenna equipped with hydrophones is used to capture radiated noise and reflected signals: it picks up the feedback of Very Low Frequency emissions from the UMS-4249 to locate, classify and track a target, while at the same time providing passive detection that only listens when active sonars are not being used. It is also designed to detect the specific noise of torpedoes, providing an early warning to deploy countermeasures in the event of a submarine attack on the vessel.The great attribute of the CAPTAS-4, which separates the transmitting and receiving instruments, is its ability to detect submarines at long range — allowing the formation of a "safety bubble" around a carrier battle group for example— and instantly determine where the noise is coming from, which is an advantage on the high seas, but also in coastal areas, where the number of signals is very high. Thanks to variable immersion, the sonar can be positioned at the best spot to avoid the non-detection troughs that form in the sea as a function of temperature, salinity and water pressure; troughs where submarines can hide.
The CAPTAS-4 equips the French, Italian, Egyptian and Moroccan FREMM frigates, Spanish F110 frigates, and was ultimately selected by the US Navy to equip the s after initially favoring a rival system — the DART — whose development had been entrusted by Raytheon but whose performance failed to live up to expectations.