The Back-Scatter Cloud Probe (BCP) measures cloud droplet size distributions from 5μm to 75μm, which are then used to derive the total number concentrations, liquid water content (LWC), median volume diameter (MVD), and effective diameter (ED). The BCP’s non-intrusive optical housing allows use in a range of ground-based or airborne applications with no contamination from ice crystal shattering and no airflow distortion.