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Active Towed Array Sonar ATAS

Calculations show that a hull mounted sonar is not able to detect a submarine near the bottom of the sea over the entire year, due to the influence of the surface channel.

To guarantee the operational readiness of detecting a submarine over the whole year and under harsh environmental conditions, an ATAS (Active Towed Array Sonar) was selected. The operational depth for the ATAS results from the sound velocity profile. The tow speed should not exceed 10 kn to guarantee acceptable detection ranges. The ATAS is equipped as back up with a passive sonar system.

                                   Array depth at 5m and 80m

System liftime is guaranteed up to 15 years

The system is delivered with the main spare parts to ensure the system's readiness while keeping the MTBF low. This ATAS-system is designed for the operation on small ships for shallow waters. Towing depth range 10 m to 250 m.

The system itself consists of 2 transmitting antennas in an active ROV and a horizontal receiving array for the active and passive mode of operation.

The frequency of the active sonar is 3.5 kHz. The detection range against small submarines is 20 km even under unfavourable backscattering conditions.

The system consists of

• A double operating winch system on deck of the tow ship (the winch handles, the tow cable and the Arrays & VIM).
• The tow cable with fairings (inside the tow cable are the power cables to charge the batteries in the ROV and the optical fibres).
• The horizontal transmitting arrays.
• One operator console with two flat panel displays (20'/each) with two Xeon processors aboard the tow ship.

The receiving arrays:

• A digital active array (length = 14 m) and a digital passive array, length = 100 m and two VIMs, each 35 m long.
• The active ROV (carries the batteries and the receiving/transmitting electronics + the two transmitting arrays.
• The ROV is operated from the tow ship and is able to be steered in the vertical and horizontal (away from the propeller of the tow ship)

Digital hydrophone Arrays:

The active and passive arrays are equipped with broadband hydrophones (10 Hz to 30 kHz).

The hydrophone sensitivity is -192 dB(re 1V/µPa)

The digital active array is equipped with 64 hydrophone (clusters length is 14 m)

The digital passive array is equipped with 32 hydrophones (clusters length is 100 m .

The 3.5 kHz digital hydrophone array has an opening angle of 1.6 deg.

Array steering angle = +/- 32 beams (beamformer) + focusing.

The digital passive array has 32 hydrophone-clusters with an opening angle of 3.3 deg. ( beamformer)+ focusing.

Signal processing:

The transmitter transmits CW, step FM signals with a big time x bandwidth product (up to several seconds; bandwidth > 1kHz) and coded signals.

The received active signal will be processed coherently.

Passive signal processing will be activated alternatively.