Cloud Droplet Measurement System

Mesa Photonics’ Cloud Droplet Measurement System (CDMS) implements a compact optical imaging technology for in situ measurement of cloud droplet size distribution function and droplet number density in the size range of 10–1000 µm. The method is based on analysis of scattered light images of individual droplets from an image frame containing images of multiple droplets illuminated by a sheet-shaped light source. The instrument is equipped with a wireless telecommunication system that broadcasts the data to the ground station. The data can also be stored on a local hard drive. The preferred deployment platform is tethered balloon system (TBS).

The CDMS implements a compact optical imaging technology for in situ measurement of cloud droplet size distribution function and droplet number concentration.

The method is based on analysis of scattered light images acquired at 90-degree scattering angle from multiple individual droplets illuminated by a sheet-shaped, pulsed, spectrally broadband (“white”) light source. White light illumination mitigates the ambiguity of the inverse Mie scattering problem of obtaining the particle size from the scattered light intensity. The droplet/drizzle diameter measurement range is 10-1000 micrometers; the droplet number density is up to several hundred per cubic centimeter. The CDMS has dimensions of 12 in. ´ 12 in. ´ 4 in.; it weighs less than 7 pounds (including battery) and draws less than 30 W of electrical power. The instrument is equipped with a wireless telecommunication system that broadcasts the data to the ground station. The data can also be stored on a local hard drive. The main application is in situ characterization of droplets in atmospheric clouds. The preferred deployment platform is tethered balloon system (TBS).

Technical Specifications (preliminary)

  • Droplet diameter measurement range: 10–1000 µm
  • Droplet number density measurement range: up to several hundred per cm3 (preliminary)
  • Effective measurement rate: 4 Hz
  • Sample volume: 0.32 cm3
  • Effective sampling rate: 1.28 cm3/s
  • Remote station (payload) dimensions, weight and power draw: 12″ × 12″ × 4″, < 7 lbs, and < 30 W, respectively
  • Remote station to ground station telecommunication: 5 GHz duplex wireless telecommunication system
  • Field calibration: one-point calibration using Mesa Photonics’ portable monodisperse droplet generator

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