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8.2.2 Bottom Feeder - a Benthic Data Provider


Summary: NOAA’s diverse responsibilities include exploration, scientific studies for biogeochemical sensing, mapping, and other activities of the coastal and oceanic benthos. Two ongoing endeavors related to the benthos are optical measurements of the bottom albedo and ecosystems mapping within the euphotic zone, in particular coral reef mapping, with coincident spectral and coral health measurements. Technology exists for determination of optical properties of the ocean bottom, albeit in a time consuming, labor intensive method. Additionally technology exists in vehicle design, mapping and non-destructive, determination of coral health. These topics are also performed by separate manual, expensive, labor-intensive methods. These two endeavors can be further developed and integrated as multiple subsystems into a utilitarian, efficient, cost effective, innovative commercial system capable of many mission applications in addition to optical measurements and coral reef mapping with health assessments. These two related efforts are in line with NOAA’s Strategic Research Guidance Memorandum, “…development of novel sensing elements and platforms, with the end goal being to increase efficiency and reliability, improve data return, and reduce costs.” This concept of a multipurpose vehicle that feeds benthic data to the surface for further dissemination and analysis is referred to as NOAA’s Bottom Feeder.


Project Goals: Overall the Bottom Feeder is conceptualized as an AUV with alternate tethered capability for feeding bottom data to the surface. The submerged vehicle will be multifunctional, with initial primary functions of 1) provide optical data and 2) map coral reef ecosystems for depth range of zooxanthallate corals to mesophotic depths. The bottom feeder vehicle will need to maintain course and speed, provide position information, maintain a set distance from the bottom, horizontal and vertical operation, have a robust collision avoidance system, be capable of data transmission to the surface (via cable and wireless) and be freely autonomous or when conditions warrant, tethered operations. A dual power source is preferred, one for the vehicle, the other for the payloads. The power sources can be linked for ascending, either for retrieval or emergency situations. Provisions for ascending should be carefully considered, such as buoyancy shifted to the bow for collision avoidance system and controlled rate, with pinger and beacon activated. Rationale for the optical sensor(s) comes from a need of the remote sensing community. NOAA/NESDIS(National Environmental Satellite, Data, and Information Service)/STAR (Center for Satellite applications and Research)/Coral Reef Watch is currently working with operational optical (ocean color) satellite sensor, Visible Infrared Imaging Radiometer Suite (VIIRS) as well as other optical satellite sensors providing products in coastal waters, including over shallow water coral reefs. Bottom albedos (radiances) are issues that need to be corrected per bottom type. Thus one of our two primary systems on the autonomous vehicle is a device capable of measuring the visible portion of the electromagnetic spectrum (approx. 300-800 nm wavelengths) for current and anticipated future optical satellite mounted sensors. To collect useful optics from the benthos, a sensor(s) is required that measures irradiance (upward looking), measures a standard optical calibration plate, and measures the bottom radiances (downward looking) and transmit those data to the surface. Optical concerns need to be considered such as the sensor(s) subsystem may be configured such as on an extension from 59 the aft of the vehicle to avoid vessel shadow, but streamlined sufficiently to avoid entanglement or striking obstructions. Rationale for the mapping originates from NOAA and several other agencies responsible for the monitoring the extent and health of U.S. coral reef holdings worldwide. The mapping and health assessment of coral reefs requires long-term investment of human resources and expensive survey systems with support subsystems. Recent technology exists in vehicle design, mapping and non-destructive, fast determination of coral health. These technologies can be further developed and integrated into multiple subsystems for a utilitarian, efficient, cost effective, novel commercial multi-purpose vehicle. There are systems available for mapping coral reefs, including stereo color camera systems producing three dimensional and accurate geo-located mosaics. Many of these systems are diver controlled, following preset transects, which can be automated. Additionally high quality spectral imagery provides information that can be used in numerous applications, such as automated classification of the benthos. Imaging spectrometers have been providing data for terrestrial and aquatic applications and have been miniaturized. Mosaics of coral reefs of concern are possible with dual camera systems, providing stereo (3-D) and sharp imagery. In addition to dual cameras for a stereo and mosaic generation, the bottom feeder should have two additional sensor components, an imaging spectrometer and a non-destructive, fast response coral health monitor. The imaging spectrometer provides a spectral image, which can be co-located with the camera images for sharpening as well as augmenting the stereo image information for classifications. The coral health sensor will provide point data, in contrast to an image, intermittently along the transect for coral health and possible stressor exposure within the mapped mosaic. A video camera would provide useful supplemental information, especially during the system development. These two initial functions of the Bottom Feeder will directly provide data to NESDIS, NOS (National Ocean Service), NMFS (National Marine Fisheries Service) and Office of Oceanic and Atmospheric Research (OAR) as well as other State and Federal agencies, non-governmental organization (NGO), academic and commercial communities. Rationale for having modular or compartmentalized and power / attachment (compartment) interfaces are to provide for additional sensors both for NOAA as well as to increase the commercialization of the Bottom Feeder. The third function of the bottom feeder is to map deep-water benthic habitats with design for an exchangeable set of sensors, such as sonar systems, etc. Additional examples of sensors are only to be incorporated into a design interface or “hooks” for future applications for the bottom feeder. In addition to sensors, a sampler subsystem for water / sediment/ small materials needs to be designed into the bottom feeder. An example of future additional sensor plans include such aspects as efficient lights for deep ocean optical surveys with mounting or compartmental design. Whereas plans for modular or compartmental replacement of lights with e.g. sonar systems when non-optical surveys are conducted. The bottom feeder, being multi-functional and can operate within a wide range of depths in an autonomous mode or in a tethered mode having two applications (optical determination of the bottom and coral reef 3-D mosaic, spectral and health mapping) with built in capabilities for other future applications will provide NOAA, other agencies, academia, NGOs, and companies 60 a cost effective way to meet mission responsibilities and provide a highly competitive commercial system.

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