1. 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.