Intrusion-Detecting Sensors Protect Borders, Troops
Lockheed Martin and Textron each offer active wireless mesh-network systems to the military and private sector, to monitor movements or hazardous conditions.
Nov 17, 2011—Aerospace and defense company Lockheed Martin has launched a new wireless-sensor mesh-network system designed for detecting intrusion, monitoring secured areas or tracking structure stress, using small devices that contain active RFID tags and can incorporate energy-harvesting technology. For the detection of movement at a border crossing, Self-Powered Ad-hoc Network (SPAN) nodes may be equipped with ground-vibration or acoustic sensors, while for structural-integrity applications, stress sensors would be employed. According to Lockheed Martin, several undisclosed agencies within the U.S. government are currently testing the ability of unattended ground sensors to protect personnel stationed in war environments, and to assist with border surveillance. In addition, Lockheed Martin has signed a contract with a private firm to use the solution as a means of determining the amount of strain placed on a bridge or other structure, and thus its overall integrity and health.
Lockheed Martin is the not only company providing wireless-sensor mesh networks for government use for military purposes or border protection. Since 2008, aircraft and defense company Textron has been providing its battery-powered MicroObserver Unattended Ground Sensors, with built-in vibration sensors, to track the presence of intruders on foot, or in vehicles. More than 1,000 such sensors are presently in operation.
SPAN nodes contain built-in energy-harvesting technology specific to a particular application, says Jack Bright, Lockheed Martin's program director for SPAN, as well as multiple sensors that also vary according to application, in order to detect the presence of a hazardous condition or an intruder. The SPAN node, he says, is designed to be small enough to fit into the palm of a person's hand. "One of the challenges unattended surveillance sensors have had in the past is size," Bright explains, because anything too large would be easy for interlopers to locate. Other end-user concerns addressed by the SPAN system, according to Macy W. Summers, Lockheed Martin's VP of advanced development, include ease of use and deployment, as well as how the sensor nodes are powered. Since batteries have a limited operational life, they would require that users locate the nodes and replace the batteries periodically. Instead, Lockheed Martin developed a solution that would not require battery replacement.
To enable this ability, Summers says, the SPAN nodes operate with extremely low power, thereby making it possible to power them via energy-harvesting technology, such as solar panels. The type of energy-harvesting system used depends on the particular application for which the nodes are deployed. The low power consumption is achievable, in part, because the nodes do not transmit unless there is a sensor reading of concern.
Each node, once placed on or in the ground in a mesh arrangement, transmits relevant data, via signals in unlicensed RF bands, to the next node, and so on, until the information is ultimately forwarded to a handheld device or a gateway that sends data directly to a back-end system via a satellite, GPRS or Wi-Fi communications link.
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