Silent sensors lie in wait for bin Laden
Hi-tech sensors scattered over the mountains and valleys of Afghanistan will
be playing a key part in tracking down Osama Bin Laden.
The devices lie silent, watching for movement, heat, vibrations and other
signals of activity and then report to airplanes or satellites above. This
allows good surveillance of large areas and, crucially, a rapid response.
"Sensors are becoming increasingly important in intelligence gathering
operations and it is safe to assume that they will be deployed in
Afghanistan," says John Pike, director of GlobalSecurity.Org, a military think
tank based in Alexandria, Virginia. "However, these devices will often be used
by special forces personnel, so details will be classified."
Importantly, he says: "Measurement sensors are hard to hide from. As winter
moves in, infra-red detection becomes easier - warm air from ventilation
shafts in bunkers show up real well. And how do you fool seismic sensors that
can detect and distinguish vibrations from the movement of jeeps, people or
Caves and tunnels
US forces are searching for bin Laden and members of the al-Qaida network,
which the US holds responsible for the terrorist atrocities of 11 September.
Reports of their whereabouts are contradictory, but they are thought to be
hiding in the caves and tunnels that riddle parts of Afghanistan.
A reward of $25 million has been offered and the US hopes the wanted men can
be located using intelligence from anti-Taliban forces or mercenaries,
combined with data from their own special forces and sensors, aircraft and
"If he moves, we spot him," a Pentagon official told Time. "If he doesn't
move, we close in on him, cave by cave."
The US has made clear that its personnel will not enter heavily defended caves
to capture or kill bin Laden. Why risk casualties, another Pentagon official
said, "when we've got 50,000 opposition fighters on the ground who are willing
to do it?" Other options are to use "bunker buster" bombs to penetrate
strongholds, or fuel-air explosion devices to attack those inside.
Sensor to shooter
A key purpose of small Unattended Ground Sensors (UGSs) is to reduce what the
military call "sensor to shooter time", i.e. the time delay between gathering
intelligence and acting on it. This is particularly crucial when targets are
small or highly mobile. A number of reports suggest bin Laden and Taliban
leaders have narrowly escaped US attacks that followed intelligence reports.
The UGSs can be buried by ground forces or camouflaged and dropped from the
air. They lie in wait for the enemy and report any activity using a
combination of seismic, acoustic, infra-red, optical and magnetic
technologies. It is this real time data that speeds up the decision making
The newest generation of sensor arrays benefit from advances in computer
processor speed and software design. This means these distributed systems can
be networked together by secure radio link to provide real-time information,
often by via satellite. The data may then be relayed to a nearby soldier's
laptop, or via several repeater units to a command post some distance away.
Networks of several arrays of UGSs usefully permit the monitoring of the
direction and speed of movement. For example, sudden, unexplained changes in
activity along routes could suggest the location of unknown bases.
UGSs also have a psychological edge. Even if some are discovered, the enemy
will not know if they have found them all or to what extent their activities
have been compromised.
Pike does sound a note of caution, though: "Although sensors can help, no one
should imagine that tracking down small groups of individuals hiding in
difficult terrain is easy. It's a tough job, but it can be done."
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