DATASONICS SIS-1500, System Manual

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SIS-1500 Seafloor Imaging System 1-9
SECTION 1 SIS-1500 Overview TTV-195 Tow Vehicle
Post-Processing of Data
Chirpscan
3
enables both a record mode for data acquisition and real-time
image processing, and a playback mode for image processing and data
analysis after the sidescan sonar records have been collected and
processed. All the real-time image processing tools available with operation
in record mode are also available in playback mode.
Chirplink II Digital Multiplexer
The Chirplink II Digital Multiplexer is the communications interface between
the workstation and the tow vehicle. It provides full duplex communications
with the tow vehicle, allowing the workstation to send commands to the tow
vehicle while simultaneously receiving sonar data, tow vehicle status
information, and sensor data from the tow vehicle. In addition, the digital
multiplexer supplies power to the tow vehicle. Using a combination of
frequency division and time division multiplexing, the digital multiplexer
allows both the data and the power to be carried on a single coaxial cable,
which connects the digital multiplexer to the tow vehicle. Frequency division
multiplexing is used for transmitting all the downlink commands and uplink
vehicle status information and sensor data at a frequency of 9600 baud.
T1 telecommunications technology, an industry standard, is used for
transmitting all the sonar data at a data communications rate of
1.544 Mbits/sec. The digital multiplexer also contains the system’s main
power switch, and includes a front panel voltmeter and ammeter for
monitoring the power transmitted to the tow vehicle.
TTV-195 Tow Vehicle
The TTV-195 Tow Vehicle contains the sidescan sonar transducer arrays,
the sonar electronics and the standard pitch, roll and heading sensors.
Available optional sensors include temperature and pressure sensors, a
cesium magnetometer and a responder. The tow vehicle, which is 4.5 inches
in diameter and 70 inches long, is constructed of 316 stainless steel and is
specifically designed to operate at depths up to 1000 meters. The nose of the
tow vehicle contains the optional temperature sensor and the optional
responder transducer, where both are encapsulated in a single urethane
mold. The temperature sensor is in direct contact with the water at all times,
providing a fast thermal time constant and a means of correlating any
observed anomalies in the sonar data with changes in sound velocity that are
due to temperature gradients. The responder transducer is positioned to