By
Graham Davis
A device which can detect and track potential incoming terrorist
divers was demonstrated to the Navy at Garden Island recently.
It is the Sea Guardian automatic allweather Diver Detection Sonar
(DDS).
A Thales Underwater Systems Australian team brought the demonstration
unit to Sydney.
The device, while not being actively considered by the RAN at
this stage, is seen as an important tool for protecting bases
and moored warships from attacks by terrorists, demonstrators
or nuisance intruders.
There are a number of companies around the world that have developed
a similar type of sonar which are also capable of detecting divers
and swimmers.
These sonars, including the Sea Guardian, are being trialed or
employed by various countries as part of a force protection system
for key maritime assets.
The Sea Guardian uses a unique acoustic “mirror” sonar system
allowing high performance in high noise environments such as Sydney
Harbour.
The newspaper was invited to watch and photograph the demonstration.
The unit demonstrated from the Sullage Wharf at Garden Island
was of the fixed type.
A second type can be lowered from the stern and bow of a large
warship while she is in port to provide protection from attack.
The Sea Guardian sends out regular sound pulses from its transceiver.
These sound waves bounce off objects in the water.
If the objects are still, such as a stone on the seabed, or is
very small, such as a fish, the DDS software ignores them.
However, if it detects a diver and, or his underwater propulsion
device it will track them.
Sea Guardian has the capacity to track the diver’s air cyclinder,
his bubble trail and the 4.5 litres of air he draws in and out
of his lungs. A diver wearing a re-breather can also be detected.
“Normally an approaching diver will come in at one knot or less,”
Thales spokesperson Paul Coe said.
“Should he be riding an underwater device he will be detected
at a greater distance because of the size of the device and rider.
“Sea Guardian will track them and should they enter a restricted
zone the device will automatically trigger.”
