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 Laser-Based Sensor Will Sniff Out Chemicals on the Move  

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 Grace Jean

 

Scientists at the Army's Edgewood Chemical Biological Center in Aberdeen, Md., are working on a next-generation, laser-based chemical detector capable of operating in reconnaissance vehicles while traveling at high speeds.

The $47.5 million project, which began last January, is an Advanced Concept Technology Demonstration, or ACTD, a process that aims to expedite research and development with a quick turnaround period of two to four years.

The ACTD has two components: the creation of a joint contaminated surface detector and the integration of available detectors onto an unmanned ground vehicle, said Peter Annunziato, technical manager.

The joint contaminated surface detector uses an ultraviolet laser, mounted underneath a vehicle about 2 feet from the ground. It fires 25 times a second. When the laser hits the chemicals, it excites the electrons in those chemicals, causing a scattering of light, known as a Raman shift. A camera and telescope detect the shift of electrons back to their original orbits, which produces a spectrum that is unique to each chemical compound, explained Annunziato.

The JCSD takes about 40 milliseconds to make a detection, he said. But factoring in processing time and the vehicle's traveling speed, the system will take about two seconds to sound an alarm.

Using a laboratory model, scientists have been able to make detections while traveling up to 45 kilometers per hour.

The need for a new system was illustrated during Operation Iraqi Freedom. Maneuver commanders, on orders to reach objectives as quickly as possible, would not wait for the Fox reconnaissance armored vehicles to make a chemical detection, which often required a lot of time and heavy maintenance, said Annunziato.

"They just decided, 'chemicals are chemicals, we'll have to deal with it,' and they charged ahead," he said. "That's not the idea. The idea is, this is supposed to find it first and warn them."

The chemical detector used by soldiers in Iraq relies on a double-wheel sampling system. Two silicon wheels, hanging from the back of the Fox vehicle, roll along the ground one at a time, picking up liquid samples. The samples are transferred to a heated probe that vaporizes the liquid and then analyzed using the MM-1 Mobile Mass Spectrometer.

"That takes a lot of time, plus the vehicle has to go slow, because those wheels, they're bouncing around or they're criss-crossing. Sometimes they fall off," and a soldier has to physically reach out and replace it, said Annunziato.

Another problem is that the system can only detect chemicals in liquid form, he said.

Because it's not dependent on surface contact, the JCSD will be able to identify chemicals in liquid and solid states.

In tests, the detector has detected droplets as small as .5 millimeters, said Annunziato.

Edgewood scientists have programmed the JCSD to detect and identify 20 chemical agents, 30 toxic industrial chemicals, nine interferents and six surfaces using its on-board library. Annunziato said the system also has the capability to detect unknown chemicals.

"If it sees something that looks suspicious, the JCSD can note the spectra of it," and notify the operator to collect a sample for further analysis, he said. After the sample is identified, the operator can reprogram the system to give an alarm.

The initial JCSD laboratory model stood five to six feet tall. Scientists have compacted it to 2-feet by 2-feet by 2.5-feet dimensions to fit into the Humvee variant of a new joint service light nuclear, biological and chemical (NBC) reconnaissance system, currently in low-rate production.

The downsized JCSD is being tested, said Annunziato.

"We're shooting for a high probability of 92 percent" of detecting contamination that may be present, he said. "We think we've got it, but of course, we need to do more extensive testing to get statistical sample sizes."

In addition to JCSD, the team is working simultaneously on integrating a suite of government and commercial detectors onto an unmanned ground vehicle.

The team looked at both the Talon and the Packbot, small robots in use in the Middle East for explosive ordnance disposal missions. The Packbot, a 65-pound tracked robot manufactured by iRobot, was selected as the vehicle because it "was more convenient for building a module package," said Annunziato. The team, however, plans to build a package that will be compatible with both robots.

The module consists of an LCD 3.2E chemical warfare agent detector, a MultiRAE Plus gas monitor, an AN/UDR-14 Radiac gamma detector, a temperature and humidity sensor and sorbent tubes for collecting samples-instruments that a dismounted soldier might carry when exploring potentially hazardous areas that cannot be reached by a reconnaissance vehicle.

"We're not trying to put Fox capabilities onto the robot. That would be several generations away," said Annunziato.

The robot eliminates the need for soldiers to be placed in harm's way, for example, when probing buildings in Iraq or caves in Afghanistan.

"It can be the first to look around corners, see if someone's there, and then sniff around to determine if there's anything there that can hurt people as they follow along," said Annunziato.

The unmanned system is designed to be controlled by a dismounted soldier using a portable operational control unit. The Packbot, equipped with a video camera, runs on batteries, and can transmit data and maneuver wirelessly within 1,000 meters, in the line-of-sight. In tests at the Edgewood facility, the team was able to operate it through two doors, said Annunziato. However, if communications are lost, the robot carries a 200-meter fiber optic line that can be tethered to the control unit.

Next year, the operational control unit will be integrated into the reconnaissance vehicle so that soldiers can manipulate the robot without setting foot outside. "This will save the soldier from dismounting and getting in harm's way, either from hostile fire or chemical contamination," said Annunziato.

If the technology demonstration is successful, Annunziato said the JCSD would transition into a program of record and either move into production or additional development and into soldiers' hands. It eventually would be incorporated into light armored vehicles, both the Marine Corps' LAV and the Army's Stryker.

Field trials for the ACTD will take place at Dugway Proving Ground in Utah between April and May.

Completing its tour in Iraq, the 95th Chemical Company, based in Fort Richardson, Alaska, will conduct operational testing of the JCSD and robotic systems on post in July. The fully integrated system will be tested in 2007.

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