The present invention relates to devices and systems for detecting a signal of interest, to make it possible to locate an underwater source of this signal.

An Underwater Locator Beacon (ULB) is a pinger fixed to a flight recorder (also known as a “black box”) or to the fuselage of an aircraft. The beacons are activated in the event of immersion and designed to emit an ultrasonic pulse at a given frequency, generally 37.5 kHz. They could also emit on other frequencies, for example between 8 kHz and 10 kHz. The pulses are emitted at one-second intervals for at least thirty days (the life of the energy sources) so that they can be traced. Typically this is carried out using a hydrophone, i.e. an electroacoustic transducer that transforms acoustic waves in a liquid into electrical signals, towed by a vessel.

FIG. 1shows a conventional system1for searching for and locating pingers. The system1comprises a vessel2and a towed hydrophone3(Towed Pinger Locator) in order to detect and locate a beacon4lying on a sea bed5. The hydrophone3makes it possible, for example, to detect an acoustic signal up to a distance D of approximately 20,000 feet.

Generally, the vessel2covers a zone that is predetermined by laying out a grid with slow towing of the hydrophone3(typically between 1 and 5 nautical miles per hour).

If the accident site of an aircraft the beacon of which is being searched for is uncertain, several vessels must be used in order to detect the beacon4while it is emitting a signal, at significant financial and human cost. In addition, the search is limited by the meteorological conditions and physical constraints (reprovisioning, etc.). It cannot therefore be ruled out that the beacon4will stop emitting a signal before it is found.

In some cases, autonomous means (i.e. that are not towed) can be used to supplement and/or replace a conventional system. It is thus possible to use, for example, military submarines, Autonomous Underwater Vehicles (AUV) or Remotely Operated Vehicles (ROV). This can be linked, for example, to difficult meteorological conditions. However, the use of such means presents other drawbacks such as, for example, considerable repositioning time, limited battery life and significant recharging time, the availability of experienced operators, or the unavailability of these means due to other demands.

It thus appears that the current means are based on systematic sweeping of a search zone and are unsuitable for detecting and locating an underwater locator beacon in a wide search zone, within a limited period of a few weeks and in uncertain conditions.

The invention makes it possible to overcome at least one of the drawbacks set out above.

Embodiments of the invention relate to a device for detecting a signal of interest allowing an underwater source of the signal to be located, the device comprising:a receiver configured to detect the signal of interest,an actuator configured to allow at least one part of the detection device to move to a zone for signalling a result of detection of the signal of interest in response to a prompt from the receiver, andan emitter configured for signalling the result of detection of the signal of interest.

The device can be distributed, in large numbers, quickly and easily, in a wide search zone so that a signal of interest, for example from an underwater locator beacon, can be detected by the receiver, which controls the actuator, which then makes at least the emitter ascend to signal the detection result. These devices operate independently of each other to detect the source of the signal.

In an embodiment, the receiver is a hydrophone and the signal of interest is an acoustic signal with a predetermined frequency.

The device is then configured to detect a predetermined signal and not just any signal.

In an embodiment, the device also comprises ballast configured to make the detection device descend to the sea bed and the actuator therein is a means for detaching the ballast in order to allow said at least a part of the detection device to ascend to the surface.

The detection device then comprises low-cost “passive” means of descent and ascent.

In an embodiment, the emitter is protected by the ballast.

In an embodiment, the emitter is a radio emitter configured to emit a radio signal.

The radio signal can be detected remotely by a satellite for example, or an antenna mounted on a vessel.

In an embodiment, the emitter is configured to emit the detection result according to at least one of the following conditions:after the detection of the signal of interest,after the actuation of the actuator,when said at least one part of the detection device is in the signalling zone,after a predetermined period, andwhen said at least one part of the detection device is close to the surface of the water.

The emitter can then be configured according to the needs and constraints of the search.

In an embodiment, the shape of said at least one part of the detection device is designed to allow the ascent of said at least one part of the detection device due to the buoyancy effect.

In an embodiment, the actuator is configured to activate a propulsion means.

The device can then ascend and/or descend by means of the propulsion means.

Embodiments of the invention also relate to a method for detecting a signal of interest originating from an underwater source and signalling the detection result, allowing the source to be located, the method being implemented by a device according to an embodiment.

In an embodiment, the method comprises the steps of:receiving a result of detection of the signal from the receiver,controlling the actuator to allow said at least one part of the detection device to move to a zone for signalling the result of detection of the signal of interest, andsignalling, by means of the emitter, the result of detection of the signal of interest.

In an embodiment, the method also comprises a step of detaching a ballast from said at least one part of the detection device, allowing at least the emitter to move to the signalling zone.

In an embodiment, the movement of said at least one part of the detection device is carried out in response to the detection of the signal of interest.

In this case, only positive detection results are signalled, in order to avoid an information overload and allow faster location of the source of the signal.

Embodiments of the invention also relate to a system for distributing several detection devices according to an embodiment. The system comprises a distribution vehicle and a distributor of detection devices, comprising a plurality of detection devices.

Such a system allows rapid distribution of the detection devices in a wide search zone.

In an embodiment, the distributor is configured to distribute the detection devices according to a predetermined topology.

In an embodiment, the system also comprises a means for detecting a detection result originating from a detection device.

Embodiments of the invention also relate to a method for distributing several detection devices according to an embodiment and for detecting a detection result originating from a detection device making it possible to locate the source of the signal of interest. The distribution and detection method comprises the implementation of a system according to an embodiment and comprises the steps of:distributing the detection devices in a search zone according to a predetermined topology, anddetecting at least one positive result of detection of the signal.

In an embodiment, the method also comprises a step of determining the predetermined distribution topology of the detection devices, and the distributor is configured to distribute the detection devices according to the predetermined topology.

