SBIR-STTR Award

The oceans may remove much of the greenhouse gas carbon dioxide (CO2) that is released to the atmosphere by the burning of fossil fuels. Dissolved C02 is converted at the ocean's surface by biological activity to particles that can sink into deep ocean water, where they are effectively sequestered. Quantifying this vertical flux of particulate carbon is therefore essential for predicting the consequences of continued C02 emissions. However, traditional methods based on sediment traps are prone to error because of hydrodynamic effects on collector efficiency and compromise of collected samples by biological activity. The aim of this project is to develop fiber optic sparse-pixel multi-aperture sensors (MAS) capable of detecting settling particles in a remote and noninvasive manner. MAS, based on the design of the insect eye, are far less data intensive than conventional imaging systems such as video cameras. MAS, which were originally conceived for weapons systems, are highly redundant and can tolerate the loss of sensing elements, biofouling of optical surfaces, and other environmental stresses associated with ocean deployment. The fiber optic components are small, easily configured so as not disturb the sensed volume of water, and inexpensive. In Phase I of this project, a laboratory prototype MAS is being developed. In Phase II, a completely autonomous system capable of deployment on instrumented buoys or free floating drifters is to be built and tested at sea.Anticipated Results/Potential Commercial Applications as described by the awardee:MAS offers advantages over traditional imaging systems, which make them ideal for process control. The nonfocussing optics do not require careful alignment and the reduced data stream can be analyzed in real time. Low cost fiber components are advantageous for installation at numerous points in the process. MAS may also be used for studying aerosols, atmospheric dry deposition, or the swimming behavior of plankton.

Much of the anthropogenic carbon dioxide (CO2) released to the atmosphere may be transported in the form of particles from the ocean surface to deep water where it is effectively sequestered. Quantifying the vertical flux of particulate carbon in the oceans is therefore essential for predicting the consequences of continued CO2 emissions. Existing methods for measuring particle fluxes are prone to errors due to hydrodynamic effects on collector efficiency and compromise of collected samples by biological activity. This project will develop an optical sensor based on the insect eye which is capable of detecting particles in a remote and noninvasive manner. The multi-aperture sensor (MAS) is highly redundant and can tolerate the loss of sensing elements, biofouling of optical surfaces, and the rigors of oceanographic deployment. Phase I demonstrated the ability of the MAS sensor to detect and track marine snow aggregates, forams, and other particles larger than 100 microns. Variance signals from the elements were correlated with size and speed of the particles, suggesting that mass flux might be sensed directly. In Phase II, advanced dataprocessing software will be developed including triangulation, variance and covariance, and neural net training. An autonomous MAS system will be deployed at sea on a neutrally buoyant platform.Anticipated Results/Potential Commercial Applications as described by the awardee:MAS sensors expand the range of particle sizes that can be analyzed with optical techniques, and will enhance the process control capabilities of fiber optic spectrometers. The sensors may also find use in packaging monitoring, the study of aerosols, zooplankton behavior, or any application where particle motion is of interest.