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 aerial research platforms including balloons, blimps and small UAVs. The Phase I study demonstrated the feasibility of the proposed method, identified the engineering challenges to be addressed in Phase II and outlined the strategy for further development of the technology. In Phase II a flight-ready compact, lightweight and low-power prototype system will be designed, constructed and field-tested. The Phase II development will provide a solid basis for further commercialization of the proposed technology.