Los Gatos Research, Inc. (LGR) proposes to develop a flight ready instrument, capable of deployment on unmanned aerial vehicles (UAVs) to simultaneously measure in situ aerosol extinction and scattering coefficients. The instrument will be lightweight, compact, robust, integrate into UAV platforms, and be capable of simultaneously measuring aerosol extinction and scattering coefficients to 0.1 Mm-1 with a 1 second sampling rate. This highly innovative instrument, based on cavity-enhanced laser spectroscopy, will operate autonomously, and continuously stream data for storage or downlink. By significantly increasing the speed, sensitivity, and accuracy of in situ aerosol optical property measurements this instrument will enhance NASA flight studies of atmospheric aerosols and their effects on the radiative balance of Earths atmosphere. These studies seek to identify how aerosol optical properties vary through the lower troposphere, and further determine under what conditions surface-based measurements of these properties be used to calculate the direct aerosol radiative forcing from a measured aerosol optical depth. These studies are also of great use in determining how in situ measurements compare to remote sensing measurements. The ability to gather in situ aerosol optical property data from UAV-based instrumentation will both complement and greatly enhance existing ground based and flight instrumentation.