Sensors to listen out for terrorists

Wireless sensors being developed at UCLA could give the US military the kind of surveillance necessary to root out terrorists hiding in the caves of Afghanistan.

Tiny, wireless sensors being developed by researchers at the UCLA School of Engineering could give the military the kind of surveillance necessary to root out terrorists hiding in the caves of Afghanistan or underground bunkers elsewhere.

No larger than an ordinary housefly, these micro electro-mechanical systems (MEMS) magnetometers can reportedly detect the presence of military equipment such as tanks, trucks or even a soldier with a rifle, to depths of 100 feet below ground. The sensors are being developed by researchers led by Professor Jack Judy in the electrical engineering department of UCLA’s Henry Samueli School of Engineering and Applied Science.

‘You really can’t carry out military operations without equipment, weaponry and vehicles – all of which are made of metal,’ Judy said. ‘When metal moves, it disturbs the earth’s magnetic field. And we know how to detect changes in the earth’s magnetic field.’

Larger magnetometers, requiring considerably more power, are already available but their size and power-consumption make using the larger devices in the battlefield less practical.

Coupled with existing wireless-sensor technology, the MEMS magnetometers could be scattered by airdrop, inserted by artillery or individually positioned to provide tactical information.

Essentially single-chip computers, Wireless Integrated Network Sensors (WINS) were developed by Bill Kaiser and Greg Pottie, both from UCLA’s electrical engineering department. The sensors have already been tested in field exercises with both the Marine Corps and Navy.

Funded by the Defence Advanced Research Projects Agency, the research is aimed at putting technologically advanced equipment to work in the battlefield. It is part of the push to modernise the US military. The research is now in the third of its three-year grant, and Judy is ready to begin testing the devices.

Although the tiny magnetometers require no power themselves, a small amount of power is needed for the circuits that interrogate the tiny metal detectors and operate the wireless network the WINS devices will establish once they’re on the ground. To eliminate the naturally occurring background noise generated by the ionosphere and by natural metallic deposits in the ground, the network listens for an ‘anomalistic response,’ in which only a few of the sensors signal a change in the magnetic field below them.

Although individual sensors are said to lack the sensitivity of more elaborate and cumbersome devices, a large array of networked sensors can provide a frequently updated picture of disturbances in the magnetic field. And that means the data the network provides will allow troops in the field to detect metallic objects any time they move.

‘If all the magnetometers detect the same change in magnetic field,’ Judy said, ‘it is an atmospheric disturbance. But if only a few sensors detect a change in magnetic field, it must be due to something nearby or below ground disturbing the magnetic field.’

Employing the same principle that drives a compass needle to point to magnetic north, Judy said, the actual sensors require no power. ‘They move of their own accord,’ he said.

Judy also noted that reducing the dimensions of the device produced none of the surprises MEMS researchers frequently encounter. ‘When the sensors are reduced to micro-scale dimensions, the angle of deflection produced by a given magnetic field remains the same,’ he said.

Source: David Brown, UCLA.

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