Confronting Maritime Terrorism

For most of the Cold War it was a deep, dark secret. Although completely declassified in 1991, even today, few really understand what SOSUS was (and is) and what it could (and can) really do.

SOSUS is an acronym for SOund SUrveillance System. In 1949 Congress first authorized money for what eventually became a world-spanning ocean surveillance system. That system, mothballed after the end of the Cold War, is coming back to life as a major weapon to fight the terrorist threat on the high seas.

Here is how the system works:

Sound generated by an object in waters deeper than 100 fathoms radiates in all directions. Sound near the surface is absorbed and scattered quickly by surface wave action. Sound that radiates downward, however, eventually is bent back toward the surface by the increasing pressure of the water column. Typically, this sound reaches the surface about 30 nautical miles from the source, forming a ring of sound about 3 nautical miles wide centered on the source. This sound reflects again, and eventually arrives back at the surface 30 nautical miles further out in a 6-mile-wide ring, and again at 90 nautical miles in a 12-mile-wide ring, and at 120 nautical miles in a 24-mile-wide ring. After that, the entire surface of the ocean contains sound from this original source.

Obviously, the level of this sound is a tiny fraction of the ambient noise level, way below the background noise generated by the ocean and everything it contains. Nevertheless, in principle any sound-producing object, whether ship, submarine or marine animal, projects its sound over the entire world ocean.

What SOSUS did was nothing less than enable the U.S. Navy to identify and track all of these sounds. From a practical engineering point of view, two problems must be solved in order to do this. First, you must find a way to filter out and identify the sounds produced by one ship, sounds that are orders of magnitude below the ambient sound level. Remember, this task was accomplished way before the advent of digital technology. It was done so well that, when I was a young Navy Sonar Technician in the early 1960s, I could take a chart produced by a SOSUS array and identify a specific vessel by name and hull number, often thousands of miles distant from the receiving array.

The second task is to locate the source of that sound, to pinpoint it in the vastness of the world’s oceans. This is why we placed arrays consisting of over 1,000 hydrophones and more than 30,000 miles of interconnecting cable in different locations around the world. Incoming sound was not only analyzed for its acoustic content in order to identify the source, but it was also analyzed over short time intervals, using the huge arrays as vectoring antennae that could generate circles of position. Crossing three of these circles resolved the location of the sound source.

The bottom line is that we actually knew the precise location of every single vessel of interest above and below the surface, essentially all the time, throughout most of the Cold War. Furthermore, the other guys knew that we knew. They did everything possible to thwart our ability. They mapped shadow zones unseen by SOSUS, where they hid their submarines. They dragged the bottom with special anchors designed to pull up and destroy specific hydrophone arrays when they could find them. (This resulted in some interesting surreptitious placements of arrays in a poker game of subterfuge and bluff that proved unequivocally that while the Soviets may have been master Chess players, Stud Poker was our game.)

After the fall of the Soviet Union, we no longer needed to know the exact locations of the world’s shipping, since most commercial vessels were tracked by one or more international tracking systems similar to air traffic control, and there no longer were submarines out there capable of threatening our existence. SOSUS was expensive to operate, so eventually we shut it down, keeping it in a standby mode in the event we would ever need it in the future.

At some point scientists within the National Oceanic and Atmospheric Administration (NOAA) determined that the old SOSUS network could help them identify and locate deep ocean vents and volcanoes. And so the old Cold War sword and chariot was beaten into plowshares for science where even today it serves the scientific community in ways never envisioned by its creators a half-century ago.

After 9/11, we found ourselves at war once again – this time with an unseen enemy who kills women and children and innocent civilians with a glee normally reserved for great victories on the battlefield. We have dramatically changed our society to accommodate this enemy. In fact, we have made it so tough for him in our own country that he has turned to blowing up innocents in places where the watchers are less observant and the system is less secure.

We still have a major gap in our homeland protection, however. Our great shipping ports still bring in huge amounts of goods and materials, some in bulk like oil and minerals, but much of it in 20-foot containers called TEUs (for twenty-foot equivalent) units. The west coast ports of Los Angeles, Oakland, Portland and Seattle currently bring in more than 10 million TEUs every year, a number that will double within the decade. Only a small fraction of these are inspected. In a previous article, (“A Solution for the Shipping Container Threat,” DefenseWatch, Feb. 12, 2003 ), I discussed the details of the kind of threat these shipping containers pose, and suggest how we can deal with this threat. The United States is addressing this inspection problem, but we are also examining the larger picture. The U.S. Pacific Command has launched the Regional Maritime Security Initiative. As reported by The Washington Times, according to Adm. Thomas Fargo, who heads the Pacific Command from its headquarters in Hawaii, the Initiative’s goal is to forge a partnership of nations willing to identify and intercept “transnational maritime threats under existing international and domestic laws.”

There are some 90,000 ships plying the oceans of this planet. The vast majority of these vessels sail under flags of convenience, registered in Tonga, Panama, Liberia, Cyprus or the Bahamas, which means that they are not subject to control by any international authority. They check out of the local maritime traffic control system upon leaving port, and eventually show up somewhere else, often without advance notice, and with essentially no information on where they have been in the interim. As Adm. Fargo told Congress in March, “We need to gain an awareness of the maritime domain to match the picture we have of our international airspace.”

In other words, we need to know where these guys are all of the time.

This is where the old Cold War SOSUS network comes into play. Newly updated, and outfitted to pinpoint the locations of ships that are not controlled by any international or national authority, SOSUS once again is available to protect our shores and those of other peace-loving nations from international maritime threats.

Knowing where the ships are located is ninety percent of the battle. It matters little that terrorists know we can do this, because there is absolutely no way for them to avoid being detected – except to stay within the 100-fathom curve, which puts them squarely under Coast Guard surveillance or that of the Guard’s foreign equivalent.

Constantly knowing the location of all the world’s rogue ships leaves little opportunity for them to meet with or be controlled by terrorists. Knowing where they are, and what they are doing, whom they are meeting, and where they are headed leaves little to chance, and goes a long way towards securing our shores from the horror of a ship borne nuclear, biological, or chemical attack.

In the words of the Commander-in-Chief: “Bring ‘em on!”

Robert G. Williscroft is DefenseWatch Navy Editor