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Hyperspectral imaging sensors come into their own for aerospace and defense applications

Hyperspectral imaging sensors for aerospace and defense applications may be somewhat of a novelty today, but the technology's practitioners say hyperspectral components of electro-optical sensor suites are headed for the mainstream-perhaps sooner than we might think.

"We see hyperspectral imaging increasing very significantly in the military space," says David Bannon, CEO of hyperspectral specialist Headwall Photonics Inc. in Fitchburg, Mass. Among the reasons is a recent increase in Headwall's commercial hyperspectral sensors business, which usually lags behind military use.

"Hyperspectral has a technological limitation now that we will overcome in the future," says Beau Legeer, vice president of product marketing at hyperspectral sensor designer ITT Exelis Visual Information Solutions in Boulder, Colo.

So what is this hyperspectral imaging technology, anyway? In short, hyperspectral imaging sensors look at many spectra of light in closely spaced bandwidths. It differs from infrared thermal imaging, which only looks at one light spectrum, and from multispectral sensors, which look at several different light spectra spaced widely apart.

The big advantage of hyperspectral imaging is in the detail it can provide. An infrared sensor or multispectral sensor, for example, might indicate the presence of a target of interest. A hyperspectral sensor, however, might indicate not only the presence of a target, but also the kind of metal it's made from, the color and type of paint it has, or the amount of moisture it contains.

"You take a picture of, say, a tank," explains Legeer. "An analyst making an interpretation would say, 'that's a tank,' but a hyperspectral sensor can tell that analyst that it's a tank, but also say if it is metal or plastic; if it's a dummy, decoy, or a real tank; and what color paint is on that tank."

Headwall's Bannon describes hyperspectral imaging sensors as a way of "doing things very efficiently. From a flight perspective, you don't need to scan territory you don't want to be over very often in a military environment," such as dangerous areas of Afghanistan.

Sometimes the sheer amount of electro-optical (EO) information a hyperspectral sensor can provide represents a double-edge sword: not only does it provide data that was unavailable previously from a single sensor, but it also poses major digital signal processing (DSP) challenges.

In fact, many of today's hyperspectral sensor systems are design- ed to match detected target signatures against libraries of known hyperspectral signatures. In the future, however, experts say DSP technology most likely will improve to meet the demands of real-time hyperspectral imaging systems, and the resolution of today's hyperspectral sensors will improve, as well.

Hyperspectral sensors, Legeer says, "collect more information in the EO spectrum, and the product you get can be matched against libraries of known materials: soil and leaf types, paint types and colors, types of metals, and types of materials that can be taken by an analyst to determine what that material is."

Intelligence analysts might consider a hyperspectral image as a second step in processing imagery. A visible-light or infrared sensor image might detect and locate targets, while the hyperspectral sensor might provide additional detail about the target.

"Hyperspectral is important when you want to identify materials in a defense application that are not easily identified, like a landing strip, or disturbed earth," Legeer says. Hyperspectral sensors also might be able to detect streams or ponds underneath a heavy forest canopy.

Hyperspectral imaging sensors typically have been airborne detection devices, mounted to manned aircraft or orbiting satellites. Unmanned aerial vehicles (UAVs), however, are expected to be hyperspectral platforms in the near future, and companies like Headwall are bringing hyperspectral imaging into use on the ground.

"You've got some very powerful sensors, like the Raytheon ACES-Hy, which is a five- or six-million-dollar sensor," Headwall's Bannon says. "When they are at that cost, you are limited in how many you can deploy." ACES-Hy stands for Airborne Cueing and Exploitation System-Hyperspectral.

"Our strategy is to provide hyperspectral sensors at a fraction of the cost, weight, and power consumption, and to put them on ground vehicles for use in a tactical deployment," Bannon says.

Headwall has built a compact, high-performance hyperspectral sensor that scans a wide field of view, uses a removable SDRAM memory card, and features a point-and-click user interface. The sensor can resolve a target six-by-six inches at a mile away, which could identify a sniper's face in a tree line, Bannon says.

Although hyperspectral sensors have many advantages, Bannon says they are not a panacea for all reconnaissance and surveillance applications. "We view hyperspectral as a critical element in any EO/IR sensor suite; it's just as important as the other sensors in a package or a gimbal ball," Bannon explains.


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Greenlawn, N.Y. 631-261-7000

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Wellesley Hills, Mass. 617-795-1968

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Castle Hill, Australia +61 (2) 8850 0262

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Boulder, Colo. 303-786-9900

ITT Exelis Space Computer Corp.
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Aurora, Colo. 303-751-0741

Norsk Elektro Optikk AS
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Spectra Vista Corp.
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Surface Optics Corp.
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