Detecting hidden threats.

The worldwide ban on the use of anti-personnel landmines (APL) should in theory reduce the demands made upon army de-mining units, but the reality is quite the reverse. In many parts of the world, mobile and foot soldiers must continue to fight on the assumption that APLs and anti-tank mines have been laid, whether by a disciplined enemy or by irregular forces.

The Ottawa Convention requires all APLs to be eliminated before 2010 and many countries have destroyed their stocks with great ceremony, retaining only sufficient numbers for use in training. Nevertheless, by no means have all countries signed up to the Convention, some arguing that APLs are an effective means of border security.

Meanwhile, bomblets, cargo shells or other submunitions in current use can and do scatter small devices that are similar to APLs in that their delivery is random and some fail to explode. Either way it is often civilian populations that are most vulnerable to such weapons long forgotten by those who laid or scattered them but nevertheless may remain a threat to life and limb.

Certainly, the main focus of landmine detection today is driven by humanitarian motives, and often the companies that produce appropriate equipment do so as much for defence users as the non-governmental organisations (NGO) established to clear mines from civilian areas. While a great deal of research is dedicated to finding better means of detecting mines, it must be said that the line dividing mine detection from actual mine clearance has become blurred.

That's because it is sometimes necessary to employ a flail or other mechanical means to clear vegetation from an area known to be contaminated with mines. Only then can the laborious task of checking every square metre begin. But often some of the solutions resulting from this research are impractical, if not downright bizarre.

Nevertheless, stimulated by the need to reduce casualties among demining units, or to reduce the cost of clearing minefields, the development of new sensor technologies continues. The systems proposed or in use include ground-penetrating radars; radio frequency enhanced infrared, air platform radars and laser techniques. To which should be added the widely used handheld metal detectors.

The Advanced Robotics Laboratory of the University of Brescia, Italy has been investigating the possible use of swarms of simple robots. This has the aim of reducing risks to human operators while speeding up the clearance process. However, difficult terrain such as thick vegetation would oblige surface preparation using flails, although this would also eliminate trip wires.

Once cleared, the robots would be unleashed to carry odour detectors that would find vapours given off by explosives. However, high winds can result in false readings and it seems unlikely that such swarms of robots will be tackling minefield anytime soon. The National Center for Physical Acoustics at the University of Mississippi is another institute that has devoted research to the mine detection problem.

It sees a laser-Doppler based acoustic-to-seismic method as a promising way to detect buried mines, which would use a non-contact excitation and response measurement technique. By employing a loudspeaker to transmit sound in a 50 to 200 Hz frequency band, slow-speed vibrational waves are excited in porous soil. If a landmine is present below the insonified patch, the transmitted slow wave is backscattered toward the surface, the anomalous ground vibrational velocities indicating the size and shape of the target.

The induced surface vibrations are measured with a laser-Doppler vibrometer. This system seems a promising way to protect operators but it remains to be seen how it performs over difficult terrain. In 2002, the university was awarded a $15.7 million US Army research contract to fuse its seismic/acoustic technology with high-resolution ground penetrating radar sensors.

Handheld devices

Mobile systems have the advantage of being able to help clear tracks and roadways quickly, but the far more demanding task of clearing fields by hand so that they can be returned to agricultural use places operators in greater danger. Both military and NGO-supported teams make use of handheld plastic APL detectors, but those without even these devices, must learn how to probe the soil with a stick to detect mines. Although highly dangerous, well-trained operators can become skilled in this very basic method.

Most mine detectors in this class consist of a head containing coils and electrodes, the former creating a magnetic field; which induces an earth current that causes electric polarisation. This in turn creates an electric field, which is detected by the electrodes and can indicate the presence of a mine. The Institut Dr Forster and Schiebel companies are among the world leaders in the development and marketing of such handheld landmine detectors and up to seven operators of the former's Minex devices may search in groups, as there is no interference between two or more detectors.

Italy's CEIA is also well represented in world markets with its MIL-D1 digital metal detector, which meets the requirement to detect magnetic and non-magnetic metals Research conducted by Adams Electronics in Britain has led to the development of the AX 777 mine detector, which red its electromagnetic emissions to minimum levels thus minimising the risk of triggering a booby-trap that responds to emissions from the detector.

The induced current consumption of the AX 777 also means that the detector can operate for months without the need to replace or recharge the unit. Like Adams, Guartel is a British company specialising in handheld detectors, the latest of which, the MD8, achieved great success in humanitarian mine clearance operations in the former Yugoslavia. But a new handheld detector developed in America by CyTerra is claimed to be a major advance in mine detection technology because of its ability to detect all types of mines with unprecedented speed and accuracy.

The detection capabilities of CyTerra's device include the non-metallic, plastic-cased mines found in Afghanistan during Operation Enduring Freedom. Consequently, the company was recently awarded a $5.1 million contract to supply the US Army with 200 units.

The CyTerra system not only locates mines but also distinguishes them from shrapnel and other metallic clutter that can slow mine-clearing operations. It fuses together ground penetrating radar and a state-of-the-art metal detector, developed by CyTerra and Minelab respectively. The system's miniature processor makes a "mine/no mine" decision, resulting in a detection rate claimed to be near 100 per cent.

Mobile Systems

Ideally, vehicle-mounted systems should be adaptable to different platforms and make use of ground penetrating radar using a wide antenna array. They should also include a means of data fusion with other sensors such as RF enhanced infrared imaging, laser vibrometry and ultra high-resolution radar. However, some prototype systems that incorporate several sensors appear to be bulky and unsuitable for use over anything but flat terrain. The Roxane experimental mine detection system exhibited at Eurosatory by Thomson-CSF (now Thales) in 1996 is one such example.

Displayed mounted on a light 4 x 4 vehicle, the Roxane demonstrator carried optical sensors on the roof, a Schiebel metal detector and microwave sensor, as well as fast- and thermal-neutron interrogation analysis systems. Reduced in size and ruggedised for carriage on a more robust vehicle, the system could become viable. For its part, the vehicle array mine detection system (Vamids) developed by Schiebel was indeed fitted to a South African Casspir armoured vehicle intended to help in the clearance of roads and supply routes.

Faced with extensive minefields in Angola/Southwest Africa (SWA), the South African armed forces developed a considerable skill in dealing with the problem, backed by innovative solutions produced by its industry. Since the formation of Namibia and the end of the apartheid era, South Africa has become a major source both of demining hardware and the expertise to use it. Indeed, in addition to South Africa, a number of other countries including Canada, Australia and Britain have contributed much to humanitarian demining efforts in several parts of the world.

But just as its war against Angolan-backed forces in SWA obliged South Africa to hone its demining skills, so too the war which led to the establishment of Zimbabwe encouraged the development of mobile mine detection systems. Like its southern neighbour, the then Southern Rhodesia concluded that specialist vehicles should provide armoured protection for the operator but would otherwise be designed to lose a wheel or two to an antitank mine.

Dubbed the 'Pookie' because of its resemblance to a small wide-eyed African bush baby, the locally designed and produced vehicle has saved many lives by travelling ahead of civilian and military convoys to detect landmines. The armoured V-shaped cab deflected blast away from the single operator, while the wheels were positioned some distance from the cab. Although the Pookie was light enough not to detonate anti-tank mines, should it do so the seat of the explosion would not be directly beneath the cab.

A development of the Pookie was displaced at Idex in Abu Dhabi earlier this year, having been transformed by MineTech International into a marketable mobile demining system. Of course, technology has moved on since the original vehicle was used in the early 1980s and the much-upgraded vehicle now incorporates a ground-penetrating radar developed in Germany by Tricon. Trials in Mozambique showed that the new Pookie could identify changes in the soil surface a depth of 0.5 metres.

But improvements to the original vehicle included replacement of the VW Beetle engine by a Hatz 40 hp hydraulic motor, after which further trials in Eritrea funded by the German government were conducted. As a result, the Pookie is now mature enough to be offered as a fast, cost-effective and accurate system for identifying mines on unsurfaced roads.

A very different vehicle has recently been developed by Ruag, but the MineWolf is designed to clear landmines with a flail system, rather than to identify them for subsequent attention. The Swiss company had previously designed a mine clearance system for the Swiss Army, using the M113 or Leopard 2 as the platform, but the MineWolf is unusual in that it can function as an agricultural vehicle when not required to clear mines.

Detection from the Air

To avoid putting personnel at risk of death or injury during demining operations, a number of attempts have been made to devise stand off detection methods that can be operated from the air. One of the best known systems is the Camcopter rotary-winged unmanned aerial vehicle (UAV) developed in Austria by Schiebel and funded by the US Army's communications electronics command (Cecom), night vision and electronic sensors directorate, countermine division.

The Camcopter can be pre-programmed to fly along selected routes or operated manually by a joystick-controlled pilot station. The UAV has been designed to carry a variety of sensors and has been extensively tested. However, it is not the only UAV to be proposed for such a role, Thales has also conducted trials with a mini helicopter capable of carrying multi-sensor systems, including passive millimetre-wave technology and active mmW or dual-mode IR/mmW technologies. However, Thales concluded that UAV R&D was soaking up too much funding with little prospect of rewarding orders, so the company has wound down this activity.

American Electronics (Amelex) has developed a synthetic aperture radar waveform and system that is compact and light enough to be mounted on a small UAV. During trials the system, utilising an ultra-wide band radar operating between one and three GHz, demonstrated excellent resolution down to some 152 mm. While showing promise the Amelex system is not yet ready for deployment.

Use of an airship as a platform to carry a Mineseeker radar system has been the subject of investigation by Britain's Dera (now Qinetiq). This project also used an ultra-wide band Sar, early trials conducted in the summer of 2000 encouraging field trials in Kosovo a year later, which revealed exceptionally high resolution. But more funding is needed to bring the Mineseeker into service.

The obvious next step in this arena would be to include a mine destruction system onboard an aerial platform. One possibility is the Model ADL3.0 lightweight laser from Continental Laser Energy of the United States. The ADL 3.0 operates continuously without an external electrical supply but has two gas supply lines--one being regular air and the second a hydro carbonic fuel supplied from a bottle. Effective to one kilometre range, the ADL 3.0 destroys mines through penetrating the mine's wall by melting the casing and the explosive material, thereby neutralising the mine's chemical ability to produce an explosion. The system currently weighs in at 38 kg, but a lighter version for airborne use could follow.

Conclusions

United Nations estimates suggest that there are at least 60 to 70 million landmines left scattered in the world, with more than 250 million stored in the arsenals of some 100 countries. While research indicates that innovative ideas could speed the process of clearing unrecorded mines, most call for funding that is slow in forthcoming. However, South Africa's Mechem explosive and drug detection system (Medds) and the "Fido" detection system developed in America by Nomadics, both make use of trace chemical detection technology.

Medds interfaces the chemical concentration of the vapour from explosives with the nasal sensitivity of specially trained dogs, while the Fido system is based on such vapour interacting with an amplifying fluorescent polymer. Trials with the Nomadics system have shown that landmine chemical signatures can be dispersed in the environment near the mine, making it difficult to pinpoint the exact location.

Funded by Qinetiq, Sensatech is also working on a project to detect and if possible identify landmines without contacting or transmitting any pressure to the soil and without causing any type of landmine to be detonated. Sensatech approaches the task using arrays of capacitive sensors and non-contact 3D tomography techniques.

But if dogs trained to operate the Mechem system can be discouraged from showing more interest in vapours other than those given off by mines, then the South African method looks to be best placed to get on with the job. However, that should not discourage the pursuit of alternative technologies that could accelerate completion of a massive task that will occupy courageous operators for years to come.