Pathlength, Altitude and Angle of Incidence Dependence of Remote Water Raman Scattering

A small remote Raman sensor was used to measure the Raman scattering signal from clear, still water as a function of water depth (12 cm and 396 cm depth), sensor distance above the water surface (20-300 cm), and angle of incidence (0-80°) to the normal of the water surface. Under thick- and thin-sample conditions, the signal depends on either the inverse, or the inverse square, of sensor distance from the water surface, respectively. A model is derived that fits data for different sensor distances, water depths, and angles of incidence. Fits to the measured data are consistent with the known intensity of water Raman scattering and the specifications of the detection system. This manuscript provides a mathematical model that can be used to predict and evaluate the performance of remote sensors and can be expanded to account for differing experimental conditions.