The Beginnings of Side Scan Sonar
From Sonar to Side Scan Sonar
Side scan sonar is a specialized use of sonar (sound, navigation and ranging). The fascinating story of sonar development is closely connected to iceberg detection, safe navigation at sea, and the increased use of submarines in World War I. The huge impact of submarine warfare in World War II caused enormous growth in global acoustics research leading to new uses of sonar for mapping the seafloor, and locating ocean bottom targets such as mines.
Why Use Sound Under Water?
Many marine creatures use sound as a key sensing and communication tool. Science still has much to learn about these amazing capabilities. Unlike radio waves and light, sound waves travel very effectively in water. Since ancient times, people have understood that sound travels efficiently in the sea. However, the science of underwater sound did not expand until submarines were widely employed as military systems.
How Side Scan Sonar Works
The principle of side scan sonar is fairly simple. Focused sound waves are produced from an underwater source (a sonar towfish) towed near the sea bottom. Just as in radar, sound waves are reflected off structures in the path of the waves and return to the source. These echoed sound waves are received by transducers at the sound source, translated into electrical signals and sent up the towing cable to the signal processing/display system in the towing vessel. The towing track record or sonargraph depicts profiles and “shadows” of the structures that acoustic signals reflected back from, and provides accurate mapping of the bottom topography.
Murky Beginnings of Side Scan Sonar
The story of American development of side scan sonar is full of intrigue because of the high national security value placed on this technology. A German-born scientist, Dr. Julius Hagemann, was brought to the USA following World War II to work in the U.S. Navy’s Mine Defense Lab (USNMDL) in Panama City, Florida. In 1954 Hagemann, while employed by the USNMDL, filed for a patent for the first American side scan sonar system. His patent was not made public until 1980. Hagemann’s side scan sonar was developed by the USNMDL and later manufactured in the early 1960s by Westinghouse. It was called the Shadow Graph—a top secret U.S. Navy undersea search and survey tool for over 25 years.
The U.S. Navy and Oceanographic Research
The U.S. Navy has been a major patron of oceanographic research from World War II to the present day. Ocean science and engineering research institutions such as MIT and Woods Hole Oceanographic Institution (WHOI) have long received funding from the U.S. Navy to conduct basic research that contributes to naval operational requirements. This Navy research funding has spawned countless civilian technologies vital to ocean science and the ocean industries.
MIT and Commercial Side Scan Sonar
Professor Harold E. (Doc) Edgerton and Sonar Research
The famous MIT electrical engineer Doc Edgerton first collaborated with WHOI in underwater photography in the late 1930s. He began to experiment with sonar in 1953 while assisting Jacques Cousteau in taking the first deep ocean pictures in the Mediterranean. In order to focus the camera accurately, they needed to know the exact distance between camera and sea bottom. This was accomplished with precision-timed sonar sources called “pingers”. Doc observed from the camera sonar signal that sound echoes could record layers of sediment just below the bottom and stated, “They showed me more than I needed to see”. This started Doc on developing his “mud penetrator”, a high-resolution acoustic sub-bottom profiler.
Martin Klein - MIT Class of 1962
In 1961, Martin Klein approached Doc about finding an interesting topic for his senior thesis in electrical engineering. Doc proposed that Klein improve the signal processing of his mud penetrator. After much hard work, Klein improved the signal, had his thesis topic and an ongoing connection to Doc. Following graduation, Klein worked briefly in Doc’s MIT lab and assisted with experiments in using the mud penetrator in a horizontal direction to detect bottom topography.
Klein Leads EG&G Side Scan Sonar Development
From late 1962 to 1967 Klein worked for Edgerton’s company, EG&G International Inc. in the Boston area as program manager for sonar systems. In 1963-64, Klein designed and installed an EG&G side scan (and vertical) sonar systems on the deep submersible Trieste (and the refitted Trieste II) for search and survey of the lost U.S. Navy nuclear submarine Thresher. This first deep water search/survey operation was a major turning point in U.S. investment in undersea technology. During his EG&G years, Klein also led the development of EG&G’s Mark I side scan sonar—the first successful commercial dual channel system available worldwide. This EG&G Sonar Systems division, headed by Klein, was spun off in 1995 as EdgeTech, a consistent leader in developing side scan sonar and underwater technologies.
Key Historic Discoveries
During these developmental years, Doc and Klein participated in many dramatic demonstrations of the search abilities of side scan sonar. In 1967, Klein assisted pioneer underwater archaeologist George F. Bass in the discovery of a 2,000-year-old Roman shipwreck off southwest Turkey—the first ancient shipwreck found using remote sensing. Later in 1967, Doc helped locate the 16th century HMS Mary Rose—now a major archaeological exhibit in Portsmouth, England. Both of these discoveries were the first significant finds of historical vessels made with side scan sonar.
The Klein Side Scan Sonar Story
The Formation of Klein Associates Inc.
In 1967, Klein departed EG&G to set his own course in the new commercial field of side scan sonar. This was a bold move because all the other companies with a stake in side scan sonar were multi-million dollar organizations. Klein started out in the basement of his apartment in Lexington and later converted a lumberyard in Salem, New Hampshire into Klein Associates, Inc.
Developing a Leading Product and a Commercial Market
Klein understood from the beginning that he needed to create a leading-edge product, offer top quality service and develop the market for side scan sonar. In the late 1960s, the market for new tools that could accurately map the seafloor (as well as river and lake bottoms), and locate lost objects, was relatively small outside of military work. The offshore energy sector was just beginning to get into deeper waters and commercial remotely operated vehicles (ROVs) did not exist. The expansion of manned submersibles seemed a likely market, but more focus was placed on vehicle control than on developing “eyes and ears.”
Promoting the Value of Side Scan Sonar
Klein decided that participating in high profile search and survey missions with Klein systems was good for business and would assist in developing the technology. In 1973, Doc helped attract headlines when he participated in the discovery of the USS Monitor using EG&G’s side scan sonar. In 1975, a Klein side scan sonar was used to locate the Hamilton and Scourge in Lake Ontario—the two most well preserved War of 1812 ships ever found. A year later, Klein and colleagues found the only existing British Wellington World War II bomber in Loch Ness, Scotland. The most famous shipwreck to date located with Klein side scan sonar has been the Titanic, found in 1985. These and many other discoveries have proven the versatility of side scan sonar and helped elect Martin Klein into the National Academy of Engineering.
A Vitally Important Tool in Ocean Exploration
The value of side scan sonar is all around us, but not obvious unless you look deeper. Worldwide offshore energy production is a major customer of this technology. All ocean drilling and energy production requires detailed ocean bottom survey work. The vast global network of undersea telecommunications continues to expand, all of which requires precise surveys. Klein side scan sonar systems have been used many times by our government as an essential tool in accident investigation—one well known example was locating the space shuttle Challenger. Ocean science is yet another global application of this technology. Only a very small percentage of the vast ocean basins have been mapped with the same accuracy as on land. New ocean exploration vehicles such as robotic submarines (AUVs) are now routinely equipped with side scan sonar. Of course, the navies of the world remain the largest users of side scan sonar. As in the beginning, naval requirements continue to push the technology forward for countless non-military purposes.