The Project will lead to development of a new technology of in situ characterization of particulate matter including measurement of the particle concentration and size distribution function. The instrumentation based on the proposed approach can also be used for monitoring atmospheric aerosols, drop sizing in clouds, and characterization of industrial and agricultural sprays. The proposed technology meets the needs of the "In Situ Airborne, Surface, and Submersible Instruments for Earth Science" subtopic of the NASA SBIR Program. The technology developed under this research program will provide a new tool for in situ characterization of particulate matter in volcanic plumes. The envisioned target instrument will be compact, low weight and very inexpensive to meet the strict requirements to qualify for use on ground based and airborne platforms including remotely operated aircraft and surface craft, and even disposable devices, such as dropsondes. Other NASA applications include measurement of atmospheric aerosols, and drop sizing in clouds.