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Cabled Observatory Vent Imaging Sonar System (COVIS)


Introducing COVIS - a sonar for imaging hot spring output on underwater volcanoes
COVIS, or Cabled Observatory Vent Imaging Sonar, was designed to quantitatively image both focused and diffuse hydrothermal outflow.  COVIS consists of a sonar sitting 4m above the seafloor on a tripod based frame (see photo below). Mechanical rotators adjust the leveling of the sonar and the direction sideways and up/down that it points.  Computers on board both the sonar itself and the frame control the rotation, drive the pinging, and record the incoming sound signal.
Current Deployment - Axial Volcano
COVIS was deployed at ASHES vent field on Axial Volcano on July 29, 2018 and connect to the NSF funded OOI Cabled Array.  Information on the summer 2018 OOI cruises can be found on the VISIONS '18 website.
COVIS actively pings the seafloor and water column collecting acoustic data to describe the distribution of hot water discharge, the rising of plumes above Inferno vent, and estimate the overall heatout. Several series of data have been or are being collected. Below are some preliminary data images.

This rendering of a 3D scene shows COVIS estimated bathymetry (green) with the detected plumes (isosurfaces of decreasing strength of backscatter from red to purple to blue) rising above Inferno vent. 

This map shows areas with high decorrelation (yellow to red) of the sonar backscatter signal which we interpret as areas of highly turbulent or hot flow (so either diffuse or focused discharge is likely).
Previous Deployment - Grotto vent, Main Endeavor Field
From September 2010 to October 2015, COVIS was deployed at Grotto vent in the Main Endeavour Field on the Juan de Fuca Ridge.  Check out Oceans Network Canada to learn more about the NEPTUNE underwater cabled observatory at Endeavour. While at Endeavour, COVIS collected an unprecedented time series of hydrothermal flow from and around Grotto vent. See our publications page for our collection of scientific papers using COVIS data and related outreach articles. 
This photo shows COVIS being deployed off of the R/V Thompson in September 2010.
Highlights of this study include the observation of steady heat output from Grotto's north tower (Xu and others, 2014), the recognition of the importance of scattering of rapid turbulent temperature variations (Xu and others, 2017), and the discovery of rapidly changing distributions of diffuse discharge.
Location map and image of COVIS on the seafloor (image coutesy of Ocean Networks, Canada).
A very happy team celebrated the installation in September 2010.  Preliminary results were published in AGU's EOS and presented at the 2011 Fall Meeting (see publication page).
Platform Development
Acoustic Instrumentation for Imaging and Quantifying Hydrothermal Flow in NEPTUNE Canada Regional Cabled Observatory at Main Endeavour Field, JdFR. Russ Light (PI), Vern Miller and Darrell Jackson, Applied Physics Lab, University of Washington; Peter Rona (PI) and Karen Bemis, Rutgers University (NSF Award ID 0825088; 01 November 2008 to 31 October 2010) Collaborative Research.
This is an engineering proposal to develop and connect sonar instrumentation to monitor hydrothermal flow at the NEPTUNE Canada Regional Cabled Observatory (RCO) in the Main Endeavour Field (MEF) on the Juan de Fuca Ridge (JdFR) offshore British Columbia as part of the Ocean Observatories Initiative (OOI). 

Image courtesy NEPTUNE Canada.

Map from Delaney et al., 1992.
The backbone cable for this RCO was installed in 2007 and the nodes and junction boxes are scheduled for installation in 2008. Our instrumentation will acoustically image time series of the changing 3D geometry, flow rate and volume flux of buoyant plumes discharging from vents and areal distribution of diffuse flow from the surrounding seafloor. Connection to NEPTUNE Canada will provide the power and bandwidth to extend our present technically proven capability of imaging from days/weeks (ROV or battery power) to months/years. This temporal extension will enable monitoring of fluxes of hydrothermal flow and detecting linkages with external forcing processes from tidal cycles to geologic events (earthquakes, volcanic activity). 

The Sonar position realtive to the Hydrothermal Plume.
The proposed new instrumentation, the Cabled Observatory Vent Imaging sonar System(COVIS), is designed as an ideal instrument for the power and data bandwidth afforded by the cabled observatory and will adapt to NEPTUNE Canada Stage I mechanical, electrical, and software functional requirements (NEPTUNE Canada letter appended). A state-of-the-art commercial off-the-shelf sonar (400 kHz) will be acquired and integrated onto a custom benthic tripod lander with a central tower (5 m high) and angular translation system (3 degrees of freedom). All necessary electrical and mechanical systems will be implemented to allow placement of the COVIS by ROV and direct connection to a NEPTUNE instrumentation node. The 3-axis angular translation system will allow operators to precisely position the multi-beam sonar head into observing positions for both plume and diffuse flow measurements, will be adaptable to changes of the flow orientations, will be capable of autonomous response to significant geophysical events detected by other NEPTUNE Canada instrumentation via shore based control software, and will have scope to be moved within the vent field. The sonar instrumentation package is designed to adapt to a seafloor site at a vent cluster in the MEF within range of the node/junction box to be emplaced by NEPTUNE Canada (water depth ~2200m), and our acoustic imaging will be coordinated with in situ measurements at the vents(temperature, chemistry, biology) by other investigators to maximize the scientific return.
We will provide a near real-time user-friendly data product for the community (3D images of buoyant plumes), will develop automated signal processing for the large data acquisition rates anticipated, and will apply our proven methods to measure 3D geometry, flow rate and volume flux of buoyant plumes and area of diffuse flow. 
Broader Impacts.
The proposed engineering and connection to the NEPTUNE Canada RCO is transformational:
(1) Extension of the capability to monitor hydrothermal flow way beyond present time limits(weeks) enables the measurement of long term changes in fluxes and elucidates linkages between flow and external forcing by oceanic and geologic processes(years). 
(2) Our innovativesonar platform and triaxial translation system has broad application to other types of instrumentation for cabled observatories 
(3) Opening a real-time window to seafloor hydrothermal flow and its interaction with oceanic and geologic process will contribute to K-12, undergraduate, and graduate research projects, and public outreach through established programs. 
(4) Our work has the potential to score an early success for the NSF Ocean Observatories Initiative (OOI) using the established NEPTUNE Canada Regional Cabled Observatory (RCO) years in advance of the U.S. Regional Scale Nodes. 

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