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. Last Updated: 07/27/2016

Wireless Sensor Web to Monitor Life

SAN MARINO, California -- The shiny green hummingbirds and huge bumblebees at the Huntington Botanical Gardens probably won't even notice the silent invaders imported from the Jet Propulsion Laboratory a few kilometers away.

Twelve plastic pods hidden among exotic greenhouse plants are part of a field test of a new technology called a wireless sensor web. The pods constitute an infrastructure that researchers hope will be useful in looking for life on other planets or studying life in hard-to-reach places on Earth.

The idea may fulfill part of NASA's goal to set up a "virtual presence" throughout the solar system. The scientists imagine that one day, groups of pods can be deployed or dropped from rovers or landing spacecraft (or from planes in remote corners of Earth).

These webs of pods could monitor biological activity f in the form of released respiratory gases f on a planet's surface with a resolution and sensitivity not attainable by satellites.

Each pod consists of a solar-powered rechargeable battery, a communication board and a microprocessor with several sensor wires extending from it. All of this is housed in a small plastic box like those that you might use to hold leftovers.

Through the sensors, the pods at the Huntington collect data on the various microclimates in the greenhouses. The sensors can detect humidity, soil and air temperatures, soil moisture, light levels and oxygen and hydrogen sulfide gases.

Every five minutes, each pod records this information and then transmits it back to a "mother node." This is a specialized pod connected by a serial port to a field computer. The mother node synchronizes the pods with one another.

Kevin Delin, project leader, and Shannon Jackson, project engineer, developed the technology at JPL in Pasadena.

Jackson and Delin started out with scaled-down versions of the pods housed in toy containers from gum ball machines. When four of those tiny pods and a mother node worked in the lab, Delin knew they could proceed with building the prototypes.

Jackson had to think of a way to keep the sensitive hardware dry and still expose the device's solar panels to sunlight.

"I thought, 'We have to put this in something,' so I went to hardware stores. And then, as I was walking down the grocery store aisle, I thought, 'This is perfect f clear and waterproof,'" Jackson said.

He attached solar panels to the bottom of a plastic box (which would become the top of the pod). He then painted the rest of the box white to keep the inside from heating up.

All of the hardware for the pods can be bought off the shelf, which makes mass production highly feasible, he said. The pods "talk" to each other like walkie-talkies over a radio frequency with a range of about a quarter-mile. Because wireless technology is progressing rapidly, producing pods with greater range can only get easier, Delin said.

JPL chose Huntington Gardens in San Marino, about 10 miles northeast of downtown Los Angeles, as the field test-site because the microclimates there range from desert to semitropical to cool. One pod is in what's called the "carnivorous bog," a box filled with insect-trapping pitcher plants and Venus' flytraps.

The experiment has been running continuously since May 18, with excellent results. "We're actually taking good data, and this is just a field test," Delin said.

Theresa Trunnelle, nursery manager at the Huntington, said the pod data are as accurate as temperatures recorded by her standard equipment, a sensor hanging in the middle of the greenhouse. And, she added, the pods have the advantage of being portable, so they can take measurements in different areas of the structure.

"We like to think [this will give] us a greater understanding of the world around us," said Jim Folsom, director of the Huntington Gardens. Folsom said he believes the wireless sensor web has "remarkable potential" in the areas of agriculture, horticulture and the study of local environmental changes. In one possible use, he envisions a web of pods tracking heat changes in a city.

Folsom is not the only one who sees possibilities for the new technology. "We're most interested in the potential for sensors on other planets. We have every hope that it will allow us to detect life,'' said Pamela Conrad, an astrobiologist at JPL.