Have You Seen the Light?

By Captain T. Q. Donaldson, U.S. Navy

But this is the environment where "Forward…from the Sea" will take the Navy and Marine Corps in the next century. We will need a wide range of capabilities to engage and defeat future long-range torpedoes, unmanned undersea vehicles, and modern submarines. We should examine every potential method and process that might expand our battlespace awareness into the oceans. One subject, involving low-light-level technology and biological oceanography, warrants further scrutiny: it involves the ability to image marine bioluminescence at night.

Imaging the Oceans

Bioluminescence is the chemically based emission of light by living organisms. The common firefly is the most well-known example, but the phenomenon is more prevalent throughout the marine ecosystems. It is a nighttime phenomenon usually seen best in the darkest of conditions, and in earlier literature it often was referred to as phosphorescence. We do not know the extent of marine bioluminescence, but it has been measured to some degree in significant areas of every ocean. Marine bioluminescence displays are caused by movement-waves breaking at the sea surface as well as ships agitating the water will cause the emission of blue-green light from many species of marine plankton.

Whether a bioluminescent display can be "seen" is a function of its intensity and duration, light transmission losses (from the depth of the display to the sea surface), and the sensitivity/signal processing of an overhead sensor. Because we are in the realm of visual detection, the image must be detectable and discernible at the ocean's surface while in a sensor's field of view. The applicable sensor technology is referred to as low-light-level (LLL), and through signal enhancement, it is able to detect extremely low levels of light in the blue-green spectrum.

The application of LLL technology to imaging the ocean at night is evolutionary in military application and revolutionary in concept. LLL devices, such as night-vision goggles, have been available for many years, and filtering or narrowing a sensor's view to a particular bandwidth certainly is not new. Placing a state-of-the-art LLL sensor on an unmanned aerial vehicle would be evolutionary; integrating the unmanned aerial vehicle to expand maritime battlespace awareness would be revolutionary, because a belief has been ingrained that darkness brings uncertainty and less capability. Specifically, we still believe that when things submerge beneath the sea surface at night they become virtually undetectable.

New Visions for Old Mind-Sets

The following mind-sets and conceptual frameworks must be revisited when addressing this subject:

#1: You gotta believe. Many people are unaware of the abundance of marine bioluminescence throughout the world's oceans. In fact, 90% of the living organisms in the ocean are plankton. During World War II, Captain Reinhard Hargegen (U-boat 123) warned other commanders: "The most dangerous feature of American water is marine phosphorescence at night . . . be aware that if you travel at periscope depth, vortices off your screws and cannon will show up as phosphorescence and betray your position." 2 Similarly, Rear Admiral Eugene Fluckey recounts, during the Barb's (SS-220) eighth war patrol in the Sea of Okhotsk, instances of limiting speed because of phosphorescence in the wake, and enemy frigates chasing down luminous torpedo tracks. 3 The challenges lie in determining the predictability of favorable oceanographic and optical conditions, as well as defining the contributions (and limitations) of LLL technology to reliably enhance maritime battlespace awareness at night.

#2: Believe in Mother Nature. Technology is not the issue; we can build an extremely capable LLL sensor. The determining factors are environmental and oceanographic. There must be a sufficient number of bioluminescent organisms at depths that allow light transmission to reach the surface with an intensity that can be detected and recognized. A sensor must be flown at altitudes that provide sufficient tactical search rates and must be able to view the ocean surface. As an illustration of favorable environmental conditions, during a 1988 winter Mediterranean deployment, 87% of the nighttime underway period was characterized by: sea state less than 5, cloud layer higher than 3,000 feet, horizontal visibility greater than five nautical miles, no precipitation, and measurable bioluminescence (water samples were taken twice a night from the inlet sea chest to the main condenser). 4

#3: Forget about all-weather, 24-hour-capable sensors. LLL sensors have inherent limitations, including a limited field of vision, weather limitations (rain, fog, and lightning), reliance on marine organisms, and the fact that they must be flown beneath the clouds. The major tactical advantages are that bioluminescence is optimized at night, LLL sensors are passive; imaging is covert; display brightness is speed related-the faster the threat transits, the brighter the display; and LLL technology is relatively inexpensive.

#4: Invest in area-specific capabilities. In shallow-water environments, each area is unique in its acoustic characteristics because of the differences in the composition and layering of the underlying bedrock. Acoustic modeling must be tailored to each separate location. Marine bioluminescence is not worldwide, but it is prevalent in many key areas of the world. From a national security/Navy point of view, two locations come quickly to mind. China already has made claims to the South China Sea, and Indian diplomats are quick to point out that "it is called the Indian Ocean." Both bodies of water, including the Straits of Malacca in between, are known to be bioluminescent and most likely would support LLL sensors year-round. The tactical advantages might be such to warrant that one or two sensors be available for deploying task force commanders in case a battlespace encompasses bioluminescent water.

#5: Overcoming the challenges of peacetime innovation. There has been great institutional reluctance to invest in a sensor that is reliant on the presence of living plants and animals in the ocean. Many lack the vision to comprehend what is possible: a new tactical optical sensor program that will enhance nighttime dominance over the oceans. At a minimum, we should press forward if only to improve our nighttime search-and-rescue capabilities.

Back to the Future

The maritime battlespaces of the future may very well resemble those of World War II, when a majority of all enemy tonnage was sunk in shallow water and littoral environments. As technological advances make air and surface combatants more vulnerable, our opponents increasingly will go "underground," into the oceans. The future underwater threat will include quiet, capable submarines and other shallow-submerged weapons and platforms.

LLL technology offers a unique, maritime contribution toward the attainment of full-spectrum dominance; specifically, the ability to extend our nighttime awareness into the oceans, depth and locations to be determined. It has the potential to provide passive surveillance, on a tactical scale, of the upper portions of the water column while being reliant on an abundant, natural phenomenon that is most visible at night.

Now is the time to apply our strengths in science and technology to determine fully the extent to which lowlight-level technology can expand our maritime battlespace awareness. The world's oceans will never be totally transparent; however, we should expand our capabilities whenever and wherever Mother Nature allows it.

1 Gen. John A. Shalikashvili, USA, "Joint Vision 2010: America's Military-Preparing for Tomorrow," p. 39.

2 M. Gannon, Operation Drumbeat (New York: Harper & Row, 1990), p. 43.

3 Eugene B. Fluckey, Thunder Below! (Urbana: University of Illinois Press, 1992), pp. 25, 27.

4 Thomas Q. Donaldson, "USS John F. Kennedy (CV-67) MED 3-88 Post-deployment Report."

Captain Donaldson is the commanding officer of the Naval Atlantic Meteorology and Oceanography Center at Norfolk, Virginia, and is a frequent contributor to Proceedings.



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