Achieving a systems-level understanding of science associated with climate change is a key topic within the DOE mission. Light absorbing particles are an important atmospheric constituent and have a direct impact on climate. They also impact air quality and health and human activities play a major role in their abundance and distribution. There is a critical need for improved observational capacities to improve the treatment of light absorbing particles, including black carbon, in models that predict climate change and are used to design control strategies. This project develops a new, lightweight, low- cost sensor to measure the abundance of black carbon in the air. The sensor is designed for environments and measurement platforms that are unsuitable for currently available commercial instruments. The Phase I work specifically includes work to improve the sensitivity of the detector through development of its electronics. Phase I also evaluates the sensitivity and accuracy of the device against reference instruments under a variety of challenging environmental conditions and sample types to ensure it will be suitable for atmospheric measurements. Follow on work in Phase II and later portions of the project will add multi-wavelength capabilities to the device and integrate it into a commercial measurement payload including pump and data and communication systems that will be deployed on unmanned atmospheric platforms, including unmanned aerial systems and balloons. This will allow for the routine operation of the measurement system to collect data in a variety of environments, including the upper atmosphere and regions previously inaccessible to other tools currently available, such as smoke plumes. Unmanned platforms offer an exciting opportunity to measure atmospheric composition in an unprecedented level of detail and regularity and sensors such as the one developed in this project are a key step towards making their use a reality. Future commercial applications include routine upper air measurements through regular operation of a network of balloon-based measurements, high-density mapping of an important component in urban particulate matter through an intelligent network of both fixed and mobile sensors, potential combination with other devices measuring atmospheric composition to gain greater insight into spatial variability of components contribute to particulate matter loadings in urban environments, identification of point sources contributing to air quality problems, non-intrusive routine monitoring of emissions from regulated sources, and personal exposure monitoring applications. We are developing a new, lightweight and low-cost sensor for use on unmanned aerial systems (UAS) and similar platforms that will help Americans understand and adapt to climate change and aid efforts to improve air quality.