The sub-bottom profiler of the Marion Dufresne is a Kongsberg Maritime SBP120. The TX transmitter (3 x 32 transducers) and RX receiver (64 transducers) arrays are more than 7 m long. The receiver array is shared with the multibeam echo sounder EM122.

Beam width and transmission level can be modulated according to the chosen number of transducers:

• 3° x 3° for full TX & RX arrays; 230 dB ref. 1 µPa at 1 m
• 6° x 6° for half TX & RX arrays; 224 dB ref. 1 µPa at 1 m
• 12° x 12° for quarter TX & RX arrays; 218 dB ref. 1 µPa at 1 m

The large number of transducers produces a high transmission level and a penetration of approximately 100 m in loose sediment. The transmitted signals are linear modulations at frequencies of between 2.5 and 7 kHz for a maximum duration of 100 ms.

The vertical resolution, approximately 30 cm, is comparable to that of the sub-bottom profilers of the vessels Pourquoi pas ?, L’Atalante and Thalassa.