S2MF

The S2MF project intends to overcome a scientific and technological barrier in the field of underwater acoustical imaging. The project aims at improving the tools used for imaging the seafloor, and measuring backscattered indexes. The leading idea is to combine the concept of saturated multi-frequency transmission with innovative wideband receiving sensors. At transmit, the harmonic components are created by taking advantage of the nonlinear propagation in water: the transmitter is driven at a single fundamental frequency, and delivers a large acoustic power; the initial sine wave distorts along propagation into a saw tooth shape. Hence, a unique source generates harmonics beams that are perfectly correlated. It enables in turn to produce – at several frequencies – sets of images that are perfectly correlated, both in time and in space. Systems based on such a multi-frequency concept are foreseen to be an asset in many applications (e.g., characterization of the seafloor, of fish schools…). For example because of the frequency dependence of the beam penetration, it is likely that an imaging system could detect artifacts such as oil slicks, or buried objects. The S2MF project focuses on the technological locks implied by the required wide-band receiving sensors. As a proof of concept, two prototypes of multifrequency systems will be conceived and operated: a sounder and a side-scan sonar. Partners of this project are the Institut d’Alembert (UPMC), ENSTA Bretagne and Ifremer.