Single dual mode (continuous and cast) instrumentation package for inherent optical property measurements: Characterization of the bucket for backscattering observation

This work describes a continuous sampling system that has been designed, implemented, and tested for the acquisition of Inherent Optical Properties (IOPs) during field campaigns. The major challenge of the work was to design and build a flow-through housing accounting for the complex sensing geometry of the ECO-VSF3, a backscattering meter, i.e., three sensor heads each of which measures the VSF at three angles. A detailed characterization of the ECO-VSF3 housing in terms of impact of the boundaries and overall system inertia is reported. A key feature of the system design is the possibility to easily detach the IOP package from the flow-through hydraulic circuit and use it in cast mode at fixed stations. This, to the best of authors' knowledge, is the first time the ECO-VSF3 is used in an underway system. Results from the comparison of continuous (Co) and cast (Ca) b measurements show excellent agreement, with differences not exceeding 7%, thus proving the system to be reliable and highlighting the feasibility for increasing the spatio-temporal sampling of surface observations.