This technology has a variety of non-NASA commercial power and energy applications such as assessment of sulfur content in fossil fuels, which is important for fuel cell based electric power generation fueled with natural gas, gasified coal, or liquid hydrocarbons. Also, sulfur dioxide is one of the six "criteria pollutants" listed in the Clean Air Act; therefore, the technology will also be of interest to the atmospheric science and environmental monitoring communities. The proposed technology meets the needs of the "In Situ Airborne, Surface, and Submersible Instruments for Earth Science" subtopic of the NASA SBIR Science Program. The technology developed under this research program will provide a new tool for in situ measurement of SO2 in volcanic plumes. These measurements performed both prior to and during eruptions are very important for improving the accuracy of volcanic hazard assessment and eruption forewarnings. The envisioned target instrument will be compact, low weight and inexpensive to meet the strict requirements to qualify for use on a variety of ground based and airborne platforms in harsh environment.