DESCRIPTION

EdgeTech manufactures a line of deep water Hydrographic Survey Systems. A system consists of a side scan sonar, sub-bottom profiler, digital link, surface interface, and a surface data display processor. A number of additional options may be integrated on to the system as needed. The Series 2400-DSS can be deployed on a tow vehicle, AUV, or ROV.

The Side Scan Sonar

EdgeTech’s Deep Water Full Spectrum "chirp" side scan sonar is a calibrated wide band digital FM sonar that provides quantitative and qualitative, high resolution, low-noise side scan imagery. It simultaneously transmits linearly swept FM pulses centered at 2 discrete frequencies. A number of center frequency options are available. The transmission of a longer duration, wide bandwidth pulse result in higher resolution sonar images and, because more energy is projected into the water, greater SNR resulting in extended range.

An important feature of Full Spectrum side scan sonar is the reduction of side lobes in the effective transducer aperture. The wide band and linearity of the FM sweep smears the side lobes of the transducer and thus achieves a beam pattern with virtually no side lobes. Three frequency set options are offered: 75 and 410 kHz, 120 and 410 kHz, or 75 and 120 kHz dual simultaneous.

The Sub-Bottom Profiler

EdgeTech’s Full Spectrum "chirp" sub-bottom profiler has a number of advantages over conventional profilers. This includes increased penetration and higher resolution. The tapered waveform spectrum, results in images that have virtually constant resolution with depth. Another advantage is the reduction of side lobes in the effective transducer aperture. The wide bandwidth of the sweep frequency has an effect of smearing the side lobes of the transducer. The result is a beam pattern with almost no side lobes. This allows the system to be very near the bottom, minimizing destructive signal scattering caused by the sediment.

The frequency range of operation is determined by the acoustic characteristics of the transmitter and receiver sensor arrays that have been selected from the three options. Each sensor array can transmit acoustic pulses with different center frequencies and bandwidths. The selection of the pulse is made on-line by the operator while profiling to achieve the best imagery. The sensor array is selected based on the sub-bottom conditions at the survey site and the type of sub-bottom features that need to be imaged. Three frequency range options are offered: 1-6 kHz, 2-16 kHz, and 4-24 kHz.

TOWED

High-frequency high-resolution operation of conventional analog systems is restricted to shallow water depths due to cable length restrictions. EdgeTech’s deep tow sonar uses digital-communication technologies to provide high-resolution images at depths that surpass those of analog systems. As an added benefit, only a single coaxial tow cable is required.

The tow vehicle contains the side scan sonar and sub-bottom profiler sensor arrays, optional sensors, and all of the Full Spectrum chirp electronics required to generate and then transmit and receive and process the Full Spectrum “chirp” sonar signals. Sonar and other data are transmitted to the surface via StarMux where a PC based data acquisition, storage, and printing processor running EdgeTech’s DISCOVER software is the user interface to the underwater portion of the system.

Typical System Configuration

• Model TV-D or DT-1 towfish with room for optional sensors.
• One of three simultaneous dual frequency side scan sonar options.
• One of 3 sub-bottom profiler arrays.
• Model FS-DW underwater Full Spectrum processor.
• StarMux digital link and power for use on a coax tow cable.
• Model 2400 topside sonar display processor hardware.
• DISCOVER software for display storage and printing of sonar data.
• Optional integration (mechanical/power/data) of sensors such as motion, heading, depth, altitude, navigation, multi-beam echo sounder, magnetometer etc.

ROV

EdgeTech's deep-water combined sonar can be installed on a variety of ROVs. A modular system is provided as a complete package including sensors and pressure vessel. Alternatively, it can be integrated into the ROV systems. For example, the ROV can provide power and a 2-way digital link to the surface. It can also provide a pressure housing for the underwater electronics.

Typical System Configuration

• One of 3 sub-bottom profiler array options.
• One of three simultaneous dual frequency side scan sonar options.
• Model FS-DW underwater Full Spectrum Chirp processor.
• Optional StarMux digital link and power.
• Model 2400 topside sonar display processor.
• DISCOVER Software for display storage and printing of sonar data.
• Optional integration (mechanical/power/data) of sensors such as motion, heading, depth, altitude, navigation, multi-beam echo sounder, magnetometer etc.

AUV

The deep-water combined sonar has been especially designed for installation on an Autonomous Underwater Vehicle (AUV) or on an Un-tethered Underwater Vehicle (UUV). Low power electronics and techniques such as turning off the amplifier and turning the power down, if not needed, are used to reduce the power consumption. The ability to accurately set and monitor the real time clock keeps the sonar data synchronized with navigation and other sensor data on the AUV.

A modular system is provided as a complete package including sensors and pressure vessel. Alternatively, it can be integrated into the AUV pressure housing. The system can operate independent of the AUV by setting parameters before deployment, or an AUV payload controller can command, control and store the sonar data. A second decimated simultaneous data stream can be fed into an acoustic link so that real time sub-bottom profiler and side scan sonar data can be displayed on the surface.

Post mission sonar data can be offloaded to the Model 2000 Topside Display Processor running EdgeTech’s DISCOVER software. Here the sonar data can be replayed on the video monitor and printed.

Typical System Configuration

• One of 3 sub-bottom profiler array options.
• One of three simultaneous dual frequency side scan sonar options.
• Model FS-AU Full Spectrum "chirp" processor.
• Model 2400 Topside sonar display processor
• DISCOVER Software for display storage and printing of sonar data.