- Canadian scientists have developed a 'stealth buoy' that
could be used to track drug boats or monitor the migration of animals such
as whales and dolphins.
-
- The buoy sits on the sea-bed until triggered by the sound
of a passing ship or animal. This sends the buoy to the surface, where
it beams information to a coastguard via satellite. The buoy then sinks
back to the ocean floor, waiting for the next ship to come along.
-
- A series of buoys could work like a tripwire across a
river estuary and stand guard on remote smuggling routes, says Cary Risley
from Defence Research and Development Canada, Dartmouth, who developed
the buoy with Seimac, a Canadian company.
-
- Most propellers have a signature sound, he says, so the
buoys will be able to tell the difference between large boats and smaller
ones, and may even be able to pinpoint specific kinds of craft. "We
are looking at adding smart software to the buoy to differentiate between
types of ships," says Risley.
-
- The buoys can also be used for research. Sensors can
be added to the buoy to measure temperature and water salinity, for example.
They can even be designed to pop up in the wake of the ship and collect
water samples to track pollution. Its sonar sensors could listen for whale
whistles or dolphin clicks, says Risley.
-
- About a buoy
-
- The buoy is shaped like a torpedo. It is 1.5 metres long
and 15 centimetres wide, and can be dropped over the side of a boat or
literally torpedoed from a military aircraft to place it in remote areas.
-
- It rises from the seafloor when a flexible balloon near
one end of the buoy is pumped full of oil. The weight of the unit stays
the same, but the increased volume of the balloon means that the density
of the unit decreases enough to propel it to the surface.
-
- The device was tested in ocean waters last November,
and responded to a surface noise from a depth of 55 metres. The researchers
say the buoys are designed to work down to 300 metres. They presented their
results at the Oceanology International 2004 meeting in London last week.
-
- They are expected to cost about US$5,000 without sensors.
The team will present their results at a coastguard conference this May
in search of customers. "By June we hope to be submerged with orders,"
says Risley.
-
- © Nature News Service / Macmillan Magazines Ltd
2004 http://www.nature.com/nsu/040322/040322-10.html
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