A new system is being developed for measurement of visibility and scattering characteristics in the visible and NIR wavelengths over extended paths. This is being developed to better understand transmission properties over long horizontal near-surface propagation paths over the ocean. The instrument, a Multispectral Scattering Imager, is designed to acquire calibrated radiance images in several wavelengths over extended paths. From measurements of the radiance near the horizon and the radiance of dark targets, combined with measurements of the inherent properties of the dark targets, visibility and effective scattering coefficient over the integrated path can be determined. The technique uses the Koschmeider equations for radiative transfer, and it allows for correction of sensor characteristics such as non-linearity and of non-zero target reflectance. The technique is based in part on the Horizon Scanning Imager, a visibility system developed in the 1990's by the Marine Physical Lab. However, it utilizes better imaging systems than were available at that time, as well as improvements to the visibility and scattering algorithms. Initial experiments are designed to test the strengths and weaknesses of the system, and to provide multispectral visible band results. These results will be used for modeling and statistical studies with respect to simultaneous measurements by a suite of other instruments. This talk will present an overview of the system and algorithms, as well as initial experimental results.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.