Atmospheric clouds have strong impact on the global radiative budget. Cloud's radiative properties are strongly affected by droplet size distribution and number concentration. This SBIR project will develop an innovative, compact and inexpensive droplet measurement system (DMS), which will provide in situ measurement of droplet size distribution function and droplet number concentration in clouds. The DMS will be designed to meet the demanding requirements for deployment on small unmanned aircraft systems (UAS). Phase I will demonstrate the feasibility of the proposed method and yield benchtop technology ready for transition to a UAS-compatible prototype in Phase II.