The Laser In-Situ Scattering and Transmissometry (LISST-100X) instrument uses the technique of laser diffraction to obtain particle size distribution (PSD), also called volume distribution. A collimated laser beam enters water, light is scattered by particles and sensed by a multi-ring detector behind a receiving lens. This measurement is known to optical scientists as the volume scattering function (VSF). At these small forward angles, light scattering is dominated almost entirely by diffracted light, which is strongly influenced by particle size. In addition to the forward scattering measurement, a photodiode placed behind a centered hole measures optical transmission. The principal measurement, the angular scattering distribution, is obtained over 32 ring-detectors. The rings cover an angular range from 0.0017 to 0.34 radians (0.097-19.48^o; Type-B). This angular range corresponds to a detectable particle size range of 1.2 to 250 microns. The data products obtained from the LISST-100X are the particle size distribution (~1 to 250 microns) and the beam attenuation coefficient at 670 nm.

This study is a collaborative effort between the College of Oceanic and Atmospheric Sciences of Oregon State University and the Laboratory for Microbial Oceanography of the University of Hawai'i at Manoa.