Ground sensors play key role in battlefield snooping

New efforts seek to fuse systems for faster force reaction, greater situational awareness

U.S. and coalition forces continue to operate in regions where the enemy is intimately familiar with the topography and is effectively disappearing into the night — despite satellites and unmanned aerial vehicles — after planting improvised explosive devices (IEDs) and staging ambushes. 

And just as the Air Force did in Vietnam, the Defense Department is looking to unattended ground sensor (UGS) systems for surveillance solutions in Afghanistan and elsewhere.


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The primary goal is to fuse broad systems links and a common mission-command network in a way that yields a comprehensive tactical picture.

The overarching idea is simple: for greater situational awareness and more threat reaction time, use radio frequency sensors — seismic, magnetic or acoustic — with digital gateways to detect, classify and track people and vehicles.

UGS systems connect to users via radio network or satellite, with applications that range from small outside-the-wire operations to larger and more capable versions that enable force protection, base and perimeter security and monitoring urban areas. Operational ranges for UGS systems overall reportedly are about 50 meters to 500 meters.

Most small tactical variants are single units that can link to others of their type, but lack data fusion qualities.

Expendable UGS

For Army LTC Matt Russell, a promising system for deployed combat troops' situational awareness may be the expendable, seismic "throw-abouts" that soldiers sprinkle through fields or other areas before moving on. They fall within Russell's Forward Looking InfraRed office, a branch of the Army Program Executive Office for Intelligence, Electronic Warfare and Sensors.

Russell said soldiers are highly enthusiastic about the small, expendable UGS, and are requesting more on an urgent basis.

UGS systems are generally used by platoons, companies and brigade combat teams. Basically, units holding battle space need to place these in dead-space areas that lack surveillance, Russell said.

Troops disbursing the small UGS use a base station and receiver to receive ping alerts, which notify them of movement in a particular area.

“The UGS that soldiers are excited about are a complete expendable kit, part of a closed network,” Russell said. The kit is comprised of multiple sensors, a base station and radio receiver. One movement-alert ping means vehicle wheels; another, means a footstep. UGS systems track these primarily through measurement and signature intelligence, Russell said.

Pings also can be delivered to units who've previously registered a UGS with their collection manager as long as they were in line-of-sight and specific sensor ranges, Russell said.

UGS data can easily reside on small Toughbooks carried in soldiers' backpacks, and in the future possibly in Androids and other commercial solutions.

The expendables are barely the thickness of two stacked hockey pucks, with a four-inch antenna sticking out.

Russell confirmed that UGS signals do not discriminate friend from foe, which is good; expendables are useful because of their simplicity.

They "limit the amount of sense you get out of them, the more [capabilities you add], the more processing and sensors you need, the harder it is to emplace them,” Russell said.

Russell said efforts are underway in IEW&S to link these UGS to aerostat sensor balloons, and given a requirement that UGS data could get onto the ground platform-based Force XXI Battle Command Brigade and Below/Blue Force Tracker system, a proven situational awareness tool.

Current Army communications or intelligence systems could also intake UGS-derived data. But for the moment due to the urgency of this requirement, "We have our own COTS (commercial off-the-shelf) radio system,” Russell said.

With "extremely positive" feedback from the field and positive assessments from the recent Network Integration Evaluation, "I think the future's bright for this program," Russell said.

Integration Strategies

Meanwhile, Textron Defense Systems' two small MicroObservers are getting raves from units in Afghanistan, especially from Special Operations units.

MicroObservers’ sensors, which are seismic as opposed to magnetic or acoustic, can be integrated with other systems such as radars or cameras for detection and tracking, and for basic threat classification. “We can give intruders’ speed and direction of travel,” said Patti Shaffner Jordan, Textron’s business development director. 

Those sensors are battery-powered like others in the small tactical class, and disposable or recoverable, as the customer prefers. The shorter-lived, one-month “field node” is for soldier-disbursal operations. The other, functionally the same but more capable, lasts more than two years and typically covers forward bases and borders. They also boast multiple gateway interfaces and backhaul options.

Both types can function co-terminus in the same network and communicate back to the same gateway. The motion tracker is in the gateway operations base or in the sensor field, depending on the application.

Soldiers equipped with ToughBooks and operator terminal monitors can see people-or-vehicle-alert tracking icons on a viewscreen, and follow them. Pings alert when a track starts forming. The sensor field can be up to two miles wide, or perhaps five to 10 times that if the gateway is at high altitude. For personnel detection, MicroObservers go up to about 100 meters; for vehicles, about 250 meters for cars, vans or all-terrain vehicles. However, friend-or-foe identification isn’t possible.

MicroObservers have intelligence, surveillance and reconnaissance applicability to manned and unmanned systems, and vehicles, aerial and ground. They have been integrated in tests and demonstrations with unmanned ground and aerial vehicles, and used to cue them along with electro-optic and infrared cameras.

MicroObservers can be buried under an inch of dirt, sand or snow out of view “and still give good detection and comms range back to the gateway,” Jordan said. One model has an external antenna that provides additional operating range from sensor to field of about 10 miles, without repeater relay, where covertness isn’t a factor.

MicroObservers’ databases use gait, weight and crawling recognition. False alarms are a problem, but if, say, an animal triggers the MicroObserver, that "signature” will — like people and vehicles — be archived, the system modified and entire sensor fields updated.

Palm-sized UGS

An especially compact UGS is Lockheed Martin’s new Self-Powered Ad-hoc Network (SPAN.) Jack Bright, who directs SPAN for the company and launched it late in 2011, said it can “revolutionize” persistent surveillance.

SPAN is a self-powered wireless mesh network of self-organizing, self-healing “field-and-forget” ground sensors, he said. It is covert and in camouflage colors, it can be employed on the battleground and borders, and for area surveillance among other tasks.

SPAN can be used tactically and as a long-term, electric tripwire for fixed installations and border monitoring. Its use is predicated on each node within the network incorporating an energy-harvesting subsystem that recharges itself by using simple energy sources in its surrounding environment. 

SPAN’s low power consumption and low cost mandate that nodes transmit only “a sensor reading of concern,” Bright said. But it’s inconspicuous sensors mean longer life and less chance of discovery and tampering. This “negates batteries’ typical [short] life and all but eliminates the need for battery replacement and servicing,” he said. 

For alerts, the system generates “fused encrypted event reports and system status data” to a local user device or remote command and control center via tailorable communication modes. The network’s multiple communication options use tactical radio (line-of-site) or satellite communications and incorporate an optional imaging capability, autotriggered during an alert event.

Bright said Lockheed Martin is in discussions with “several defense and security customers” for SPAN, which can be employed as a standalone system or as a ground sensor capability in a larger suite of surveillance systems.

About the Author

David Walsh is a special contributor to Defense Systems.

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