TCS Daily

Tales of the Hyperspectral

By Kenneth Silber - July 23, 2002 12:00 AM

A technology that has roots in the civilian space program is turning out to be highly relevant to national security and the war on terrorism. This technology is hyperspectral imaging. As the name implies, it is well-suited for perceiving things not readily seen - such as camouflaged tanks, clouds of poison gas, and terrorists who attack and then hide.

The human eye, of course, perceives only the small, visible-light portion of the electromagnetic spectrum. Detecting phenomena via other portions of the spectrum, such as infrared or ultraviolet light, requires specialized cameras or equipment. Multispectral sensors gather data simultaneously in several portions of the spectrum. Hyperspectral devices operate across numerous slices of the spectrum, and typically are programmed to recognize chemical signatures and other subtle patterns in the objects under study.

(The boundary between multispectral and hyperspectral is not very well-defined. In general, multispectral instruments make detections in fewer than a dozen distinct segments of the electromagnetic spectrum, and often these segments are far removed from each other. Hyperspectral instruments can have hundreds of "channels," and usually these are contiguous on the spectrum.)

NASA has played a key role in pioneering and developing multispectral and hyperspectral imaging. Astronauts on the 1968 Apollo 9 mission used a four-camera array to perform the first multispectral photography from space. More multispectral images of Earth were taken in the 1970s using the Skylab space station and the Landsat-1 satellite. The space shuttle's second flight, in 1981, included experiments with a multispectral infrared radiometer.

In 1982, NASA began airborne experiments with what's regarded as the first hyperspectral instrument, called the Airborne Imaging Spectrometer. This device, flown over a mining area in Nevada, demonstrated a capability of identifying various clay minerals from the air. In late 2000 NASA placed a hyperspectral sensor into orbit aboard its EO-1 satellite. By then, airborne or satellite-based hyperspectral technology had shown potential for various civilian uses, including mineral mapping, measurement of agricultural yields, and forest management. (In 1999, private groups used airborne hyperspectral imaging to monitor the habitat of Rwanda's endangered gorillas.)

Military Applications

The U.S. military, too, has taken a growing interest in hyperspectral technology. The Air Force contracted for use of a hyperspectral sensor on a commercial satellite called OrbView-4. However, the rocket carrying the satellite failed to reach orbit, and the payload was destroyed over the Indian Ocean. This failure came on September 21, 2001, 10 days after the attack on America and amid a pressing need for satellite data about Afghanistan.

Consequently, the Pentagon turned to NASA, drawing upon hyperspectral data from the EO-1 satellite to support combat operations in Afghanistan. This was part of a broader trend, emerging during the Afghanistan war, of stepped-up military use of NASA assets and information. (It's a trend that has generated some resistance in Congress, notably from Sen. Barbara Mikulski, the Maryland Democrat who chairs the subcommittee that funds NASA. Early this year, Mikulski warned NASA to maintain a "firewall" between military and civil space activities. Such fastidiousness would be easier to understand during peacetime.)

The precise contribution that hyperspectral technology made during the Afghanistan war is not publicly known. But it is evident that enthusiasm for the technology within the Pentagon has reached a new high. A variety of defense-related hyperspectral projects are under way or taking shape, with aims as varied as seeing through camouflage, detecting hidden mines, tracking chemical and biological weapons, and even identifying specific individuals at a distance. (A project funded by the Defense Advanced Research Projects Agency, or DARPA, aims to use a hyperspectral camera to distinguish facial and skin features of human subjects amid variations in lighting and atmospheric conditions.)

Among the major initiatives are the Air Force's MARS (Multispectral Agile Reconnaissance System), which is a hyperspectral sensor for the U-2 spyplane, and the Navy's LASH (Littoral Airborne Sensor/Hyperspectral), which is focused on detecting submarines and underwater mines. A Montana company, HyPerspectives, recently won an Air Force contract to develop techniques for identifying camouflaged ground objects from altitudes of 10,000 or more feet.

Meanwhile, hyperspectral technology is playing an expanding role in the civilian space program that was crucial to its origins. NASA's 2005 Mars Reconnaissance Orbiter will carry, among other scientific instruments, a hyperspectral imager that will locate mineralogical signs of water and hydrothermal activity on the surface of Mars. Such indicators will be important in choosing the landing targets for future Mars missions.

It's just possible, in other words, that a technology that is helping humanity explore the solar system will also help bring Saddam Hussein to a sudden and much-deserved death. Mention that if someone asks whether the space program has provided useful spin-offs.



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