European Facility For Airborne Research

Optical array probe. Cloud particle enters field of view passing through a laser beam. Particle shadow falls on a collecting optical array (normally a photodiode array). This is sampled at a rate such that the pixel resolution in time is the same as that in the across-array dimension. This forms a digitized shadow image of the particle.
From this size and shape are determined, and bulk parameters such as concentration and size spectra derived. Empirical relationships are used to calculate the mass of irregular particles (and hence the ice water content).