Singh Hanumant

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Singh
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Hanumant
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  • Preprint
    Toward extraplanetary under-ice exploration : robotic steps in the Arctic
    ( 2009-01-12) Kunz, Clayton G. ; Murphy, Christopher A. ; Singh, Hanumant ; Pontbriand, Claire W. ; Sohn, Robert A. ; Singh, Sandipa ; Sato, Taichi ; Roman, Christopher N. ; Nakamura, Ko-ichi ; Jakuba, Michael V. ; Eustice, Ryan M. ; Camilli, Richard ; Bailey, John
    This paper describes the design and use of two new autonomous underwater vehicles, Jaguar and Puma, which were deployed in the summer of 2007 at sites at 85°N latitude in the ice-covered Arctic Ocean to search for hydrothermal vents. These robots are the first to be deployed and recovered through ice to the deep ocean (> 3500m) for scientific research. We examine the mechanical design, software architecture, navigation considerations, sensor suite and issues with deployment and recovery in the ice based on the missions they carried out. Successful recoveries of vehicles deployed under the ice requires two-way acoustic communication, flexible navigation strategies, redundant localization hardware, and software that can cope with several different kinds of failure. The ability to direct an AUV via the low bandwidth and intermittently functional acoustic channel, is of particular importance. Based on our experiences, we also discuss the applicability of the technology and operational approaches of this expedition to the exploration of Jupiter's ice-covered moon Europa.
  • Preprint
    Map building fusing acoustic and visual information using autonomous underwater vehicles
    ( 2012-10) Kunz, Clayton G. ; Singh, Hanumant
    We present a system for automatically building 3-D maps of underwater terrain fusing visual data from a single camera with range data from multibeam sonar. The six-degree of freedom location of the camera relative to the navigation frame is derived as part of the mapping process, as are the attitude offsets of the multibeam head and the on-board velocity sensor. The system uses pose graph optimization and the square root information smoothing and mapping framework to simultaneously solve for the robot’s trajectory, the map, and the camera location in the robot’s frame. Matched visual features are treated within the pose graph as images of 3-D landmarks, while multibeam bathymetry submap matches are used to impose relative pose constraints linking robot poses from distinct tracklines of the dive trajectory. The navigation and mapping system presented works under a variety of deployment scenarios, on robots with diverse sensor suites. Results of using the system to map the structure and appearance of a section of coral reef are presented using data acquired by the Seabed autonomous underwater vehicle.
  • Preprint
    Characterizing the deep insular shelf coral reef habitat of the Hind Bank marine conservation district (US Virgin Islands) using the Seabed autonomous underwater vehicle
    ( 2005-10-26) Armstrong, Roy A. ; Singh, Hanumant ; Torres, Juan ; Nemeth, Richard S. ; Can, Ali ; Roman, Christopher N. ; Eustice, Ryan M. ; Riggs, Lauren ; Garcia-Moliner, Graciela
    The benthic communities of the deep insular shelf at the Hind Bank Marine Conservation District (MCD), an important spawning grouper aggregation site, were studied with the Seabed autonomous underwater vehicle (AUV) at depths between 32 to 54 m. Four digital phototransects provided data on benthic species composition and abundance of the insular shelf off St. Thomas, U.S. Virgin Islands. Within the western side of the MCD, well developed coral reefs with 43% mean living coral cover were found. The Montastrea annularis complex was dominant at all four sites between 33 to 47 m, the depth range where reefs were present. Maximum coral cover found was 70% at depths of 38 to 40 m. Quantitative determinations of sessile-benthic populations, as well as the presence of motile-megabenthic invertebrates and algae were obtained. The Seabed AUV provided new quantitative and descriptive information of a unique coral reef habitat found within this deeper insular shelf area.
  • Preprint
    Explosive volcanism on the ultraslow-spreading Gakkel ridge, Arctic Ocean
    ( 2007-11-26) Sohn, Robert A. ; Willis, Claire ; Humphris, Susan E. ; Shank, Timothy M. ; Singh, Hanumant ; Edmonds, Henrietta N. ; Kunz, Clayton G. ; Hedman, Ulf ; Helmke, Elisabeth ; Jakuba, Michael V. ; Liljebladh, Bengt ; Linder, Julia ; Murphy, Christopher A. ; Nakamura, Ko-ichi ; Sato, Taichi ; Schlindwein, Vera ; Stranne, Christian ; Tausenfreund, Upchurch ; Winsor, Peter ; Jakobsson, Martin ; Soule, Samuel A.
    Roughly 60% of the Earth’s outer surface is comprised of oceanic crust formed by volcanic processes at mid-ocean ridges (MORs). Although only a small fraction of this vast volcanic terrain has been visually surveyed and/or sampled, the available evidence suggests that explosive eruptions are rare on MORs, particularly at depths below the critical point for steam (3000 m). A pyroclastic deposit has never been observed on the seafloor below 3000 m, presumably because the volatile content of mid-ocean ridge basalts is generally too low to produce the gas fractions required to fragment a magma at such high hydrostatic pressure. We employed new deep submergence technologies during an International Polar Year expedition to the Gakkel Ridge in the Arctic Basin at 85°E, to acquire the first-ever photographic images of ‘zero-age’ volcanic terrain on this remote, ice-covered MOR. Our imagery reveals that the axial valley at 4000 m water depth is blanketed with unconsolidated pyroclastic deposits, including bubble wall fragments (limu o Pele), covering a large area greater than 10 km2. At least 13.5 wt% CO2 is required to fragment magma at these depths, which is ~10x greater than the highest values measured to-date in a MOR basalt. These observations raise important questions regarding the accumulation and discharge of magmatic volatiles at ultra-slow spreading rates on the Gakkel Ridge (6- 14 mm yr-1, full-rate), and demonstrate that large-scale pyroclastic activity is possible along even the deepest portions of the global MOR volcanic system.
  • Preprint
    Long-baseline acoustic navigation for under-ice autonomous underwater vehicle operations
    ( 2008-05-19) Jakuba, Michael V. ; Roman, Christopher N. ; Singh, Hanumant ; Murphy, Christopher A. ; Kunz, Clayton G. ; Willis, Claire ; Sato, Taichi ; Sohn, Robert A.
    The recent Arctic GAkkel Vents Expedition (AGAVE) to the Arctic Ocean’s Gakkel Ridge (July/August 2007) aboard the Swedish ice-breaker I/B Oden employed autonomous underwater vehicles (AUVs) for water-column and ocean bottom surveys. These surveys were unique among AUV operations to date in requiring georeferenced navigation in proximity to the seafloor beneath permanent and moving ice cover. We report results for long-baseline (LBL) acoustic navigation during autonomous under-ice surveys near the seafloor and adaptation of the LBL concept for several typical operational situations including navigation in proximity to the ship during vehicle recoveries. Fixed seafloor transponders were free-fall deployed from the ship for deep positioning. The ship’s helicopter collected acoustic travel times from several locations to geo-reference the transponders’ locations, subject to the availability of openings in the ice. Two shallow beacons suspended from the ship provided near-surface spherical navigation in ship-relative coordinates. During routine recoveries, we used this system to navigate the vehicles into open water near the ship before commanding them to surface. In cases where a vehicle was impaired, its position was still determined acoustically through some combination of its acoustic modem, the fixed seafloor transponders, the ship-deployed transponders, and an on-board backup relay transponder. The techniques employed included ranging adapted for a moving origin and hyperbolic navigation.
  • Preprint
    Active methane venting observed at giant pockmarks along the U.S. mid-Atlantic shelf break
    ( 2007-11) Newman, Kori R. ; Cormier, Marie-Helene ; Weissel, Jeffrey K. ; Driscoll, Neal W. ; Kastner, Miriam ; Solomon, Evan A. ; Robertson, Gretchen ; Hill, Jenna C. ; Singh, Hanumant ; Camilli, Richard ; Eustice, Ryan M.
    Detailed near-bottom investigation of a series of giant, kilometer scale, elongate pockmarks along the edge of the mid-Atlantic continental shelf confirms that methane is actively venting at the site. Dissolved methane concentrations, which were measured with a commercially available methane sensor (METS) designed by Franatech GmbH mounted on an autonomous underwater vehicle (AUV), are as high as 100 nM. These values are well above expected background levels (1-4 nM) for the open ocean. Sediment pore water geochemistry gives further evidence of methane advection through the seafloor. Isotopically light carbon in the dissolved methane samples indicates a primarily biogenic source. The spatial distribution of the near-bottom methane anomalies (concentrations above open ocean background), combined with water column salinity and temperature vertical profiles, indicate that methane-rich water is not present across the entire width of the pockmarks, but is laterally restricted to their edges. We suggest that venting is primarily along the top of the pockmark walls with some advection and dispersion due to local currents. The highest methane concentrations observed with the METS sensor occur at a small, circular pockmark at the southern end of the study area. This observation is compatible with a scenario where the larger, elongate pockmarks evolve through coalescing smaller pockmarks.
  • Preprint
    A dual sensor device to estimate fluid flow velocity at diffuse hydrothermal vents
    ( 2009-06-12) Sarrazin, Jozée ; Rodier, P. ; Tivey, Margaret K. ; Singh, Hanumant ; Schultz, A. ; Sarradin, Pierre-Marie
    Numerous attempts have been made over the last thirty years to estimate fluid flow rates at hydrothermal vents, either at the exit of black smoker chimneys or within diffuse flow areas. In this study, we combine two methods to accurately estimate fluid flow velocities at diffuse flow areas. While the first method uses a hot film anemometer that performs high frequency measurements, the second allows a relatively rapid assessment of fluid flow velocity through video imagery and provides in situ data to calibrate the sensor. Measurements of flow velocities on hydrothermal diffuse flow areas were obtained on the Mid-Atlantic Ridge (MAR). They range from 1.1 to 4.9 mm/sec., at the substratum level, in low temperature (4.5 to 16.4°C) diffuse flow areas from the Tour Eiffel sulfide edifice. A strong correlation was observed between fluid flow velocities and temperature, supporting the possible use of temperature as a proxy to estimate flow rates in diffuse flow areas where such a simple linear flow/temperature relation is shown to dominate.