M. Woolsey

Enhancing NIUST's SeaBED class AUV, Mola Mola

Mola is a seafloor mapping AUV owned and operated by the National Institute for Undersea Science and Technology (NIUST). Since its initial sea trials in May of 2009, effort has been applied to enhancing the navigation and imaging systems for high-resolution surveys of specific targets in depths up to 2000 meters. These surveys require accurate positioning during the initial dive to the seafloor, and smooth navigation once the survey begins. To work toward this goal, an inertial navigation system with position and velocity aiding has been integrated with the vehicle software, and it is currently being field tested. The imaging system has also been modified by adding LED arrays to provide more consistent lighting and by merging navigation data with the images for georeferencing. The above system enhancements have forced changes in the vehicles layout, and operational experiences have led to improvements in the vehicles mechanical systems.

NIUST - Deepwater horizon oil spill response cruise

In May 2010, the National Institute for Undersea Science and Technology (NIUST) had a 17-day research cruise aboard the UNOLS vessel R/V Pelican scheduled. NIUST is a partnership of the University of Mississippi, the University of Southern Mississippi and NOAA. Before sailing, the Deepwater Horizon oil platform burned and sank, resulting in an uncontrolled oil spill at a depth of 5000 ft at Mississippi Canyon Block 252. Subsequently, the decision was made to abort the planned hydrate and ship wreck research in favor of an oil spill response. The primary goals of the redefined cruise were to acquire baseline and early impact data for seafloor sediments and subsurface distribution of oil and gas hydrates as close as possible in time and space to the origin of the oil spill. Investigating an oil spill nearly a mile deep in the ocean presents special benthic sampling and subsurface oil detection challenges. NIUSTs AUVs were unloaded from the ship and a larger main winch installed to allow operation of a large box corer for collecting sediment samples in water depths up to 2000 m. During the first five-day leg of the cruise, a total of 28 box cores were collected. The Pelican returned to port (Cocodrie, LA) to drop off sediment and water samples for immediate analyses, and to take on more sampling gear and supplies for the second leg of the cruise, including an Acrobat, a CDOM fluorometer, a Video Ray ROV, and a C02 sensor in addition to the already installed CTD Rosette with 02 sensor and light transmissometer. During Leg 2, box core samples were collected until weather prohibited safe operations. CTD stations were plotted to cover the area surrounding the wreck site and at various depths to cover the water column in order to map the subsurface water column structure and chemistry as baseline values for future investigations and especially to look for submerged oil and/or gas hydrates. Early in the water column sampling, a subsurface feature was discovered at 1200 to 1400 m depth. This layer was detected by three independent sensors, CDOM (colored dissolved organic matter) fluorometer, light transmissometer, and oxygen sensor. All three instruments responded in unison with greater fluorescence and beam attenuation and decreased 02 concentration. These signals were first observed at a station 5 miles from the accident site. Second and third station measurements, exactly half the distance to the spill site from the previous one, at 2.5 miles, and at 1.25 miles, showed the same signal but with significantly greater magnitude. Following this discovery, the sampling plan for the remaining days of the cruise was changed to map the newly discovered feature. This paper will discuss methods, pursuit of leads, gear and instrumentation utilized, resulting in the initial discovery of deep hydrocarbon plume features resulting from the uniquely deep oil spill.

Expanding the capabilities of the NIUST AUVs

The seafloor mapping AUVs Eagle Ray and Mola Mola have vastly different capabilities and operational requirements, yet they perform complementary tasks. These AUVs are operated by the National Institute for Undersea Science and Technology (NIUST), which is a NOAA sponsored partnership between the University of Mississippi and the University of Southern Mississippi. Eagle Ray collects Multibeam sonar bathymetry and CTD data, as well as data from guest payloads. Mola Mola collects color images of the seafloor along with multibeam bathymetry. In back-to-back dives, Mola Mola can conduct focused studies over targets determined from broad surveys carried out by Eagle Ray, but the two vehicles have also had successful cruises independently.

NIUST AUVs - Expanding possibilities

The National Institute of Undersea Science and Technology (NIUST)s Underwater Vehicle Technology Center (UVTC) expanded their operational capabilities by acquiring a SeaBED class AUV in early 2009. This vehicle dubbed, Mola Mola after the Ocean Sunfish, is a superb addition to the UVTC, as it adds photographic capabilities at very slow moving speeds to the centers repertoire. The vehicle is designed to fly at speeds of 0.2 ms-1 about 3m above the seafloor, snapping high resolution digital images of the seafloor at preset intervals of 4 to 5 seconds. Normal mission behavior, programmed prior to launch of the vehicle, is to cover a certain area on the seafloor in a lawn mowing track, with parallel lines covering the entire area. At the end of the mission, geo-referenced photo mosaic maps of the target of interest on the sea floor are computed. The vehicle was deployed for several missions on the NASA vessel Liberty Star in the Bahamas. High resolution imagery of the bottom fauna and flora from depths too deep for deep divers to reach, provided insight into the distribution of Lion Fish in the coral reefs of the Bahamas. At the end of the field season engineering efforts were started to reorganize and replace certain hardware components to allow for improved navigation and data handling within the vehicles software architecture. They vehicle itself has since been modified from its original design, adding guided inertial navigation and improvements in its image acquisition process. Changes further include obstacle avoidance, GPS positioning and addition of a VHF radio beacon. In October 2009 combined efforts of both AUVs, the Mola Mola and the Explorer class Eagle Ray were needed in the Gulf of Mexico aboard the NOAA ship Nancy Foster, to locate and retrieve information about sunken ships of historic interest, some of which may have disappeared below the water surface of the northern Gulf of Mexico, almost 200 years ago. In a collaboration between NIUST, MMS and NOAA Office of Ocean Exploration and Research, targets identified in side scan sonar images, were selected and investigated by the AUVs. Eagle Ray, due to its large size and design features, performed initial multibeam surveys of the target areas, producing high-resolution maps of the seafloor. These maps were used to determine safe working areas for the Mola Mola, which was subsequently launched to take a continuous series of photographs in close proximity to the seafloor, producing a photo-mosaic map of the target area. Eagle Ray served as a platform for a mass spectrometer mapping of the Mississippi Canyon Block 118 Hydrate Mount as a part of the Gas Hydrate Observatory efforts. Results o this dive produced a high resolution spatial map of methane gas distribution 6m above the seafloor, discovering three new methane seeps in the area Continued mapping efforts in the Hudson Canyon together with the National Marine Fisheries Service and Rutgers University. High resolution multibeam data from the canyon revealed interesting never before seen detail and bottom features in this area. Enough data to spark new and diverse interest about sub bottom composition and marine live within the canyon.

NIUST AUV's study shipwrecks in the northern Gulf of Mexico

In October 2009 two autonomous underwater vehicles (AUVs), the explorer class Eagle Ray and the seabed class Mola Mola, were launched from the NOAA ship Nancy Foster to locate and retrieve information about sunken ships of historic interest, some of which had disappeared below the water surface of the northern Gulf of Mexico, almost 200 years ago. In a collaboration between the National Institute for Undersea Science and Technology (NIUST,) the US Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE) and the US NOAA Office of Ocean Exploration and Research (OER), targets identified in side scan sonar images, were selected and investigated by the AUVs. Eagle Ray, due to its large size and design features, performed initial multibeam surveys of the target areas, producing high-resolution maps of the seafloor. These maps were used to determine safe working areas for the Mola Mola, which was subsequently launched to take a continuous series of photographs in close proximity to the seafloor, producing a photo-mosaic map of the target area. Operational procedures and results from these dives will be presented, showing the complementing features of these two very different AUVs in operation.

New developments for the NIUST AUVs

The National Institute for Undersea Science and Technology operates two AUVs, Eagle Ray and Mola Mola that are primarily tasked with performing seafloor surveys. Upcoming missions will require surveys at 1200 to 1600 meters depth, so the vehicles are being prepared with new and updated systems and software. Recently, Eagle Ray was equipped with new batteries and a subbottom profiler. A descent weight system was added to Mola Mola, along with a revised power system and new mission capabilities.

Design, implementation, and refinement of a hardware-in-the-loop simulator for a hovering AUV

A simulator was designed for troubleshooting the hovering AUV Mola Mola, operated by the National Institute for Undersea Science and Technology. The SeaBED class Mola Mola had suffered several failures in its last 2010 cruise and two 2011 cruises. Through simulator testing, these failures were found to be a single power system issue that manifested itself in three very different ways as it worsened during the differing conditions of the cruises. The simulator supplies navigation parameters to the vehicle control system while monitoring the AUVs thruster RPM. Running the simulator with the vehicle in air can reveal general mission behaviors. By mounting the thrusters in a water tank and monitoring the opened housing electronics, power issues can be examined during the course of simulated missions.

Using MB-System and Matlab to generate geographical mosaics from seafloor images

A method of generating photomosaics from AUV-derived seafloor images was produced using principally the software packages MB-System and Matlab. Images are placed based on their geographical positions as logged by the vehicle, however, the raw navigation is refined using acquired bathymetry, reference bathymetry, and the images themselves. During these refinements, care is taken to maintain a physically realizable navigation model. The initial phase of this development was to generate supplementary files to support image placement into world space by GIS utilities. Subsequently, programs were developed in Matlab to assemble image data in a more effective manner than was available from standard utilities, and also to produce an updated navigation model based on visual control points common between crossing and overlapping images. Resulting mosaics have been used for groundtruth points in broader surveys, sensor placement and localization, and general mission planning.

AUV-derived geographical photomosaics - using multibeam bathymetry to correct image placement

A photomosaicking technique was improved by incorporating data from multibeam bathymetry acquired simultaneously with the seafloor images. AUV navigation logs are used to geographically place the images, as has been previously documented. This revision accounts for navigation offset and drift by using multibeam processing tools to refine image placement. The processed bathymetric grid combined with vehicle logs allow for the scaling of image size and illumination to produce more accurate photomosaics.

Mola Mola, NIUST's low-altitude photo and multibeam AUV

Mola Mola is a seafloor mapping AUV owned and operated by the National Institute for Undersea Science and Technology (NIUST). Its primary sensor is a downward-facing camera producing color-corrected seafloor imagery which, with proper navigation and post processing, can be converted to a photo mosaic. It also uses a multibeam sonar to gather bathymetry encompassing the photo coverage. Since its delivery in May of 2009 Mola Mola has been modified in the areas of its imaging and navigation systems as well as several mechanical systems.