Pasadena, CA —Imagine a network
of monitoring instruments that can adjust their operation and deployment based on the type and level of information they are receiving. That's the idea behind the Sensor Web concept, a data-gathering architecture developed at NASA's Jet Propulsion Laboratory.
A Sensor Web consists of wireless-linked, sensor "pods," or units, that monitor and explore environments, says Kevin Delin, a member of the technical staff. But don't confuse them with distributed sensors or sensor networks. "The Sensor Web pods matter to each other," notes Delin, "with the unique feature that information gathered by one pod is shared and used by other pods," allowing the network to react and modify its behavior based on the data collected. Key attributes are an open, scalable architecture, local decision making and analysis, networked intelligence, and economy of scale.
The pods come in two basic types: The first are mainly comprised of the sensors that interact with the environment and an omni-directional transmitter for data. The second, less numerous, type serve as the telecom-node uplink "mother" points and computational centers of the network, running the protocol schemes and providing local data analysis.
Data hopping from one pod to another, until received at a mother pod, cuts individual pod power needs. Power for the data transmission need only be enough to reach at least one other pod for retransmission to other pods, and eventually the mother, rather than direct transmission over a long distance. And data hopping allows new pods seeded into the network, or those recovering from a "sleep" mode, to integrate themselves into the web.
"The web itself is the instrument," says Delin, "not the individual pods which make it up. Just like interconnected dendrites in the brain, the wireless-connected pods allow a macro-intelligence to emerge." If a pod goes offline for an instrument or power problem, the remainder of the web compensates by increasing data acquisition rates, for example, giving interpolation with greater time resolution making up for the loss in spatial resolution. If the pods have mobility, some could move into the area where data was lost. Sensors could also self-deploy to areas of increasing interest, such as when a certain chemical or seismic shock is detected—giving greater data gathering where needed.