DATASONICS SIS-1500, System Manual

Page: 24 / 110

1-10 DATASONICS
Volume I System Manual June 1998
provide the optimum beam pattern for tracking the tow vehicle with an
acoustic positioning system. The optional pressure sensor is contained within
the end cap and is exposed to ambient pressure through a port on the rim of
the end cap.
The nose is attached to the forward end of a pressure housing, the
electronics housing, which contains the sonar electronics. An end cap both
seals the opposite end of the housing and attaches to another housing, the
sonar transducer housing, which is free flooding and contains the sonar
transducers. The nose and end cap are secured to the electronics housing
with a closure bolt in the nose. The electronics housing also contains the
vehicle’s tow point, and the sonar transducer housing contains the vehicle’s
tail fin.
The tow vehicle’s towing arm, which is designed for rapid attachment and
detachment, contains a shear pin release mechanism, which is designed to
cause the towing arm to break away from the tow point should a collision
occur or should the tow vehicle become snagged. However, one end of a
recovery cable is attached to the towing arm. The cable runs back along the
top of the vehicle to its stern. Should an obstruction cause the tension on the
towing arm to exceed 200 lbs, the towing arm will break away and the tow
vehicle will cartwheel one-half of a revolution, with the nose moving
downward and then backward, clearing the tow vehicle from the obstruction.
This is shown in Figure 1-3. As the recovery cable remains attached, the tow
vehicle can be safely recovered. The tail fin will also break away should it
collide with an obstruction—and it is easily replaced.
Sidescan Sonar Transducer Arrays
The sidescan sonar, which operates in the 190 to 210 kHz band, utilizes two
transducer line arrays that are installed in the free flooding transducer
housing. The arrays are aligned end to end, with one along each side of the
tow vehicle. This arrangement provides a one-way horizontal beam width of
1
°
and a vertical beam width of 50
°
. In addition, the down-look angle of each
transducer array is adjustable from 0
°
to 20
°
in 10
°
increments.