The ground sensor nodes are easily disguised as rocks which makes detection extremely difficult. (Photo courtesy of Lockheed Martin.)
As unmanned aerial vehicles (UAVs) advance, the wireless sensor networks that they use also are evolving. An example is a new wireless ground sensor system. It promises to provide unmanned vehicles with ubiquitous coverage and constant surveillance of designated areas.
The Self-Powered Ad-hoc Network (SPAN) from Lockheed Martin is a multi-purpose wireless platform that utilizes a network of sensor nodes. Each node, placed on or in the ground or in a mesh arrangement, transmits relevant data to the next node until the information is ultimately forwarded to a wide-area communications link. Each of these lightweight, “palm-sized” sensor nodes can be easily fitted into a rock camouflage enclosure to make detection difficult. In addition, the low-power mesh networking reduces the electromagnetic (EM) signature. On-board data processing minimizes the occurrence of false alarms. SPAN only transmits to the UAV if there is a sensor reading of concern. During a mission, the network automatically prompts the UAV’s high-precision sensors to further characterize an alert. This eliminates the need for a remote analyst while allowing UAV operators to focus on identified threats instead of waiting for potential ones. The system, which supports multiple backhaul communications including satellite communications, uses commercial off-the-shelf (COTS) components.
For its power source, SPAN relies on thin-film energy cells that harvest energy from the surrounding environment. There are two power configuration options: perpetual and expendable. Perpetual power includes sensing nodes and a gateway utilizing energy harvesting and a thin-film battery. Expendable power includes sensing nodes and a gateway with a replaceable battery. Both configurations include a ruggedized handheld computer for local monitoring and sensor emplacement.