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; John H. Morrow, Biospherical Instruments Inc.; Alexandra Olivier*, Biospherical Instruments Inc.; and Koji Suzuki, Hokkaido University. *Presenting Author

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. 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 and

precise control of the position 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.

Legacy oceanographic profiling systems often do not properly resolve the optical

complexity of shallow, near-shore waters because their size, rate of descent, or

deployment mechanics were developed for the open ocean. 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. C-PrOPS is specifically designed to be

deployed by hand, either from a small or large vessel, or from docks and piers, and

thereby supports a wide variety of multidisciplinary research goals.

The capability of the profiler to be maneuvered is a significant advantage for

fragile ecosystems that are easily damaged (coral reefs), heterogeneous systems (algal

blooms), shallow waters subjected to bottom resuspension from boat maneuvers (seagrass

beds), geographically constrained areas where piloting a larger platform is difficult

(marshes), or lakes and reservoirs impacted by drought conditions with reduced water

levels and impaired access. Results are presented from recent field campaigns where C-

PrOPS was deployed successfully in a wide variety of environments, including the open

ocean, coastal bays, in-shore lagoons, lakes and reservoirs, and rivers. Sampling

conditions varied from highly turbid to clear,, freshwater to hypersaline, oligotrophic to

harmful algal blooms, and very shallow to deep—depending on the location of the

aquatic system.