Optical Phytoplankton Discriminator (OPD, a.k.a. BreveBuster) determines colored dissolved organic material (CDOM)
absorption spectra and particulate light absorbance spectra. The CDOM absorption spectra and correlation coefficients
(referred to as 'similarity indexes') between the particulate absorbance spectra and known phytoplankton classes are
available in real-time. Post-deployment processing calculates the best fit of multiple absorbance spectra from known
phytoplankton taxonomic classes. Through this process the OPD provides an estimate of the phytoplankton community
chlorophyll distribution among the classes included in the fit process. The major components of the OPD include: a
liquid-waveguide capillary cell (LWCC), a fiber-optic spectrometer, a tungsten-deuterium fiber-optic light and a 0.2
micrometer pore cross-flow filter. In-water operation of the OPD began in May 2003. Since that date 25 of these
instruments have been deployed on a variety of autonomous underwater vehicles, buoys, piers, channel markers and
boats and ships. It has been utilized in CDOM studies off the New Jersey coast, in HAB monitoring efforts in the Gulf
of Mexico and the Great Lakes, and in phytoplankton community structure studies in the Galapagos Islands and the
Mediterranean Sea. Most recently, it has been deployed to Veracruz, Mexico for HAB monitoring. Presently, several
OPD's operating on Slocum gliders and coastal buoys make up a local HAB observatory south of Tampa Bay, Florida,
partially supported by the NOAA/IOOS through GCOOS. This presentation will detail the OPD's capabilities and report
results from several of the deployments listed above. The ongoing effort to effectively visualize 4-D phytoplankton
community structure will be discussed.
Optical properties derived from ocean color imagery represent vertically-integrated values from roughly the first
attenuation length in the water column, thereby providing no information on the vertical structure. Robotic, in situ
gliders, on the other hand, are not as synoptic, but provide the vertical structure. By linking measurements from these
two platforms we can obtain a more complete environmental picture. We merged optical measurements derived from
gliders with ocean color satellite imagery to reconstruct vertical structure of particle size spectra (PSD) in Antarctic shelf
waters during January 2007. Satellite-derived PSD was estimated from reflectance ratios using the spectral slope of
particulate backscattering (γbbp). Average surface values (0-20 m depth) of γbbp were spatially coherent (1 to 50 km
resolution) between space and in-water remote sensing estimates. This agreement was confirmed with shipboard vertical
profiles of spectral backscattering (HydroScat-6). It is suggested the complimentary use of glider-satellite optical
relationships, ancillary data (e.g., wind speed) and ecological interpretation of spatial changes on particle dynamics (e.g.,
phytoplankton growth) to model underwater light fields based on cloud-free ocean color imagery.
Buoyancy driven Slocum gliders were a vision of Douglas Webb, which Henry Stommel championed
in a vision published in 1989. Slocum gliders have transitioned from a concept to a technology serving research
and environmental stewardship. The long duration and low costs of gliders allow them to anchor spatial time
series. Large distances, over 600 km, can be covered using a set of alkaline batteries. Lithium batteries can
anchor missions that are thousands of kilometers in length. Since the initial tests, a wide range of physical and
optical sensors have been integrated into the glider allowing measurements of temperature, salinity, depth
averaged currents, surface currents, fluorescence, apparent/inherent optical properties active and passive
acoustics. A command/control center, entitled Dockserver, has been developed that allows users to fly fleets of
gliders simultaneously in multiple places around the world via the Internet. Since October 2003, Rutgers gliders
have conducted 157 missions, traversed >55,000 kilometers, logged >2600 days at sea, and logged ~350,000
vertical profiles. The capabilities of the glider make them an indispensable tool for the growing global effort to
build integrated ocean observatories. For example, gliders are now a central tool within the National Science
Foundation Ocean Observatory Initiative (OOI) and the National Oceanic and Atmospheric Administration's
Integrated Ocean Observing System (IOOS). Gliders provide a new magnet in which to attract young people
into the ocean science and engineering. For example Rutgers undergraduates now anchor long duration flights
of gliders world-wide beginning their freshmen year. This is critical to training the next generation.
The effectiveness of sensors that use optical measurements for the laser detection and identification of subsurface
mines is directly related to water clarity. The primary objective of the work presented here was to use the optical data
collected by UUV (Slocum Glider) surveys of an operational areas to estimate the performance of an electro-optical
identification (EOID) Laser Line Scan (LLS) system during RIMPAC 06, an international naval exercise off the coast
of Hawaii. Measurements of optical backscattering and beam attenuation were made with a Wet Labs, Inc. Scattering
Absorption Meter (SAM), mounted on a Rutgers University/Webb Research Slocum glider. The optical data
universally indicated extremely clear water in the operational area, except very close to shore. The beam-c values from
the SAM sensor were integrated to three attenuation lengths to provide an estimate of how well the LLS would
perform in detecting and identifying mines in the operational areas. Additionally, the processed in situ optical data
served as near-real-time input to the Electro-Optic Detection Simulator, ver. 3 (EODES-3; Metron, Inc.) model for
EOID performance prediction. Both methods of predicting LLS performance suggested a high probability of detection
and probability of identification. These predictions were validated by the actual performance of the LLS as the EOID
system yielded imagery from which reliable mine identification could be made. Future plans include repeating this
work in more optically challenging water types to demonstrate the utility of pre-mission UUV surveys of operational
areas as a tactical decision aid for planning EOID missions.
An appropriate determination of water clarity is required by defense and security operations assessing subsurface threats compromising harbor and coastal security. For search and inspection operations involving divers, underwater imaging, and electro-optical identification (EOID) systems such as laser line-scanners, the key environmental parameter needed is the optical attenuation coefficient (directly related to diver visibility). To address this need, a scattering-attenuation meter (SAM) measuring attenuation and diver visibility was developed for integration on new compact surveying platforms such as ROVs and the REMUS and glider AUVs. The sensor is compact (18X8X6 cm3), low power, robust, and hydrodynamic with a flat sensing face. The SAM measures attenuation using a novel dual-scattering approach that solves the paradox of making high-resolution attenuation measurements over the long pathlengths required for natural waters with a compact sensor. Attenuation and visibility data is presented from San Diego harbor in coordination with video images of bottom topography collected with a REMUS vehicle, from around New York harbor with a SAM mounted in an autonomous Slocum glider, and from Narragansett Bay. Results show that 1) visibility and/or attenuation in harbor and coastal regions can change rapidly over small scales (meters), especially near the bottom, 2) turbid bottom nepheloid layers are common, 3) typical visibility and/or attenuation levels fall in a range where knowledge of visibility and/or attenuation can be essential in the decision making process for security operations, and 4) attenuation is a significantly more accurate proxy for diver visibility than backscattering.
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