State-of-the-Art Optical Data Collection using the Compact-Propulsion Option for Profiling Systems (C-PrOPS)

Stanford B Hooker, NASA Goddard Space Flight Center, Greenbelt, MD, United States, Alexandra L Olivier, Biospherical Instruments Inc., San Diego, CA, United States, Koji Suzuki, Hokkaido University, Sapporo, Japan and John H Morrow, Biospherical Instruments Inc, San Diego, CA, United States
The challenges of collecting optical data in shallow waters establish state-of-the-art requirements for high temporal, spatial, and spectral resolution measurements of in situ spectral irradiance and radiance, as well as for data processing and analytical systems. Legacy profiling systems developed for the open ocean often do not properly resolve the optical complexity of shallow, near-shore waters because of their size, rate of descent, or deployment mechanics. The Compact-Propulsion Option for Profiling Systems (C-PrOPS) is an instrument system designed to obtain optical measurements in shallow waters with the documented uncertainties required for current and next generation satellite sensors, such as PACE and ACE. C-PrOPS consists of separate multichannel downward irradiance and upwelling radiance instruments mounted on a so-called hydrobaric backplane equipped with a pair of digital thrusters and a conductivity sensor. The combination of adjustable buoyancy and operator-controlled thrusters affords unprecedented maneuverability of the instruments in the water column. With a 15 Hz sampling rate, C-PrOPS can achieve 1–10 mm vertical resolution in near-surface waters. Near-surface loitering, adjustable descent rates as slow as 5 cm/s, and vertical tilts to within 2.5° during shallow (<1 m) and deep (>100 m) profiles are regularly achieved. DACPRO data acquisition software combined with PROSIT data processing provides all spectral data products (313–875 nm) within 1 m of the surface. This unprecedented spectral range allows C-PrOPS to develop and confirm the bio-optical relationships for vicarious calibration, algorithm validation, and basic research. The capability of the profiler to be maneuvered is advantageous for fragile systems that are easily damaged (coral reefs, marshes, and seagrass beds), heterogeneous systems (algal blooms), or when drought conditions result in lakes and reservoirs with impaired access. Results are presented from recent field campaigns where C-PrOPS was successfully deployed in the open ocean, coastal bays, in-shore lagoons, lakes, reservoirs, and rivers. Sampling conditions varied from highly turbid to clear, freshwater to hypersaline, oligotrophic to harmful algal bloom, and very shallow to deep—depending on the location of the aquatic system.