(Figure 1) This target found in Area 1 may be a barge but its identification has not been verified. The images were generated by an REMUS 100 SW AUV with a duel frequency side-scan sonar. The image on the left shows the entire target captured by the 900-kHz sonar. Detailed images to the right were generated by the 1800-kHz sonar and show hatches, cable and other objects. Click image for larger view and image credit.
(Figure 2) An MMP Remus 100 discovered this lost torpedo on the NUWC test range. Investigators will examine this and other possible torpedoes in the future. Click image for larger view and image credit.
Mission Summary
May 23, 2008
Frank Cantelas
Maritime Archaeology Program Officer
NOAA’s Office of Ocean Exploration and Research
After a year of planning and two weeks of operations it was apparent that AUVfest 2008 was a great success. NOAA’s collaboration with ONR to sponsor the demonstration grew into many partnerships, highlighting the theme, “Partnership Runs Deep.” Over the two week run of AUVfest many partnerships developed among the participants; between maritime archaeologists and AUV technologists, and between the organizations involved. NOAA’s primary mission for AUVfest was to provide an avenue for public outreach and education. This included the participation of archaeologists in field operations, a workshop for archaeologists and AUV technologists held at the University of Rhode Island, extensive coverage on the Ocean Explorer website you are looking at right now, developing education products for the website, and supporting a film documentary. All these things were accomplished.
Out of the twelve AUVs participating eight were used on archaeological sites. Weather and technical problems impacted some of the surveys but given the nature of using advanced technology under water this was expected. Our work focused on four shipwrecks and the unexplored NUWC test range. AUV systems were generally delegated to sites where they could collect useful data given the types of sensors they carried. Although we completed missions on all of the sites there never seems to be enough time to accomplish everything. Some sites received more attention than others based on our goals and logistics. Below is a discussion of what we found along with images of some of the data.
Site 1: NUWC North Test Range
In the years following the Civil War the Navy built a Torpedo Station on Goat Island, adjacent to the NUWC shore facility, to develop the torpedo as a weapon for undersea warfare. The NUWC test range stretches north from Goat Island and is still used to test undersea vehicles. Little is known about what lies on the bottom of the range but it likely contains torpedoes and related equipment that are significant to the history of undersea warfare. Several important discoveries were made on the test range by the REMUS 100 SW AUVs using duel frequency side-scan sonar. These include one torpedo, possibly several others, and a vessel that appears to be a metal barge (Figure 1 and Figure 2). All of these sites were unknown prior to AUVfest.
Sites 2 and 3: Prudence Island Wreck and Wooden Barge
These two wrecks lie just a few hundred meters apart off Prudence Island. Site 2, the Prudence Island Wreck, is a 20th Century vessel constructed of steel and measures roughly 120 feet long. It was discovered by the NOAA ship RUDE in 2004 and little is known about it. Site 3 is a wooden barge measuring roughly 120 feet long and probably dates to the first half of the 20th Century. Both sites rise high above the bottom in approximately 60 feet of water.
(Figure 3) iPUMA is a wide swath forward looking sonar used to identify possible targets. This image shows the two wrecks off Prudence islands and features on the surrounding seafloor. For scale, the wooden barge is 120 feet long. Click image for larger view and image credit.
(Figure 5) The SAS12 image shows a number of features on the Prudence Island Shipwreck and great detail on the surrounding bottom. Note the anchor just below the ship’s stern and the chain for the marker buoy on the left. Click image for larger view and image credit.
(Figure 4) Data collected by iPUMA can be processed into bathymetric charts. This chart shows the bottom bathymetry of the area around the wrecks off Prudence Island. Click image for larger view and image credit.
(Figure 6) A SAS12 close-up view of the Prudence Island Shipwreck reveals several details on the vessel’s deck and a lobster trap on the left side. The most prominent features are the drag marks for the chain holding a marker buoy. Individual links on the chain appear as dots leading to the surface buoy which is the light hazy area to the left. Click image for larger view and image credit.
(Figure 7) SAS12 captured this image of the wooden barge near Prudence Island. Divers have confirmed the presence of rock, machinery and other debris inside. Click image for larger view and image credit.
Several AUVs surveyed the two wrecks using different types of sensors. The iPUMA is a wide swath forward-looking sonar which has great potential for the scientific community because it can cover such a broad area. While the iPUMA does not provide high resolution images it quickly distinguishes targets, even small targets, over a wide area. Data from iPUMA was able to depict the geographical context of the Prudence Island sites and surrounding bottom features (Figure 3). This data can also be displayed as 3D bathymetry to show the wrecks and submerged landscape (Figure 4). Synthetic aperture sonar on the SAS12 provided phenomenal clarity on both wrecks. This system has a fairly wide swath coverage and provided extremely high resolution. If you look closely at the image of the Prudence Island Wreck there is an anchor for a marker buoy at the bottom of the picture (Figure 5). Drag marks from the anchor chain mark the bottom and by zooming-in you can see individual links on the anchor chain (Figure 6). Similar detail can be seen in the image of the wooden barge (Figure 7).
Site 4: H.M.S. Cerberus
Four British Frigates (Cerberus, Juno, Lark, and Orpheus) were trapped in Narragansett Bay in August 1778, when a French naval squadron came to assist American forces during the Revolutionary War. The British decided to destroy their vessels rather than turn them over to the French. H.M.S. Cerberus was run aground and burned to avoid capture. Built in 1758, Cerberus measured 118 feet on deck and carried 28 guns. Today, the site is partially buried.
Many of us were interested to see what the AUVs could discover on this site. It has been the subject of much research but little is known about what lies beneath the sediment. The best vehicle for investigating the Cerberus is the BOSS which combines a camera, gradiometer (to locate ferrous metal), and a bottom object scanning sonar (BOSS) that can image buried objects. For analysis, all this data can be fused together and graphically overlaid to see correlations between the sensors – a perfect tool for any archaeologist investigating an old shipwreck. Should BOSS ever make it to the commercial market archaeologists could use it to literally “see” below the bottom. They could undertake fewer excavations, which are very expensive, and really target areas that should be excavated.
(Figure 8) On the H.M.S. Cerberus site 4, a Bluefin 12 BOSS AUV used three sensors (an electro-optical camera, gradiometer, and bottom object scanning sonar) to detect a partially buried cannon. These images show how data from the three sensors is combined to corroborate a target location. Click image for larger view and image credit.
(Figure 9) On another part of the Cerberus site the Bluefin 12 BOSS AUV detected two more buried objects similar to the other cannon found on the shipwreck. Click image for larger view and image credit.
BOSS collected data from known areas of the site and may have found previously undiscovered portions of the wreck. In one image a partially buried cannon can be seen in a photograph which is also located by the magnetic gradiometer and imaged by the BOSS (Figure 8). In another image we can see two cannon-like objects that are similar in size and magnetic signature to the known cannon (Figure 9). Three-dimensional models of these objects also appear very cannon-like but we will have to wait until archaeologists can verify their identity before we know for sure (Figure 10).
(Figure 10) BOSS data from one of the cannon-like objects, processed into a voxel or three dimensional model, suggest the target has a long cylindrical shape. The size is similar to other known cannon from the Cerberus. Click image for larger view and image credit.
(Figure 11) Transphibian used forward looking sonar to image portions of the Cerberus site. This comparative illustration shows reinforcing bands on a cannon currently on the site with one previously recovered. Click image for larger view and image credit.
Transphibian also spend time on the Cerberus with its forward looking sonar. This unique vehicle is propelled by flippers and can be operated autonomously or by an operator. Transphibian provided an excellent image of a cannon (Figure 11).
Site 8: H.M.S. Lark
As French ships approached, the commander of the H.M.S. Lark ordered his frigate set afire to avoid capture. The frigate suffered a violent explosion scattering material over a wide area. Today, the remains of the Lark are almost completely buried under sediment.
The Lark is located several miles north of the main survey areas and did not receive as much attention as the other sites. The MMP REMUS vehicles completed side scan sonar runs and found the area to be a flat silty bottom with only a few rocks sticking up. iPUMA made a pass over the site and did not find any significant targets. Given that the Lark is buried, BOSS and LSG buried mine hunting systems would have been effective but they did not have the opportunity to collect data. We’ll just have to wait for another chance to visit this site.
Finally
In many ways AUVfest 2008 was an experiment with numerous objectives. Among them to see if the AUVs could work successfully on archaeological missions, to incorporate archaeologists on AUV technology teams, and to see if NOAA, ONR and NUWC could work together in a technology demonstration with a wide range of goals. Overall it seems that we accomplished our various missions. In particular, AUVfest 2008 created an excellent opportunity for maritime archaeologists to collaborate with AUV technologists. Putting the archaeologists in the technology teams during field operations and hosting a workshop to discuss the results created a valuable dialog between the two groups. The maritime archaeologists now have a knowledge base on which to plan the use of AUVs in their own research and connections within the AUV community to help them accomplish their work.
The success of AUVfest demonstrates that there is great value in leveraging these systems for duel use. It increases the value of the public’s investment and greatly expands the scope of scientific research for the benefit of all. This demonstration focused on maritime archaeology but duel use applications are obvious for many ocean sciences. The AUVs and their sensors are cutting edge technology. Making them available to other scientists will likely lead to significant discoveries and scientific advancement.
