SPEC has developed a Fast Cloud Droplet Probe (FCDP) with state-of-the-art electro-optics and electronics that utilizes forward scattering to determine cloud droplet distributions and concentrations in the range of 1.5 to 50 microns.  Though designed for cloud droplet measurements, the probe has also shown reliable measurements in ice clouds.  The new electronics include a temperature controlled fiber-coupled laser, FSSP-300 optics with pinhole limiting depth of field (Lance et al. 2010), a field programmable gate array (FPGA), 40 MHz analog-to-digital-converter (ADC) sampling, custom amplifiers, a very small and low power Linux based 400 MHz processor and a 16-Gigabyte flash drive that stores data at the probe.

The CPI records high-resolution (2.3 micron pixel size) digital images of particles that pass through the sample volume at speeds up to 200 m/s. In older models, CCD camera flashes up to 75 frames per second (fps), potentially imaging more than 25 particles per frame. More recent camera upgrades capable of bringing frame rate to nearly 500 fps. Real time image processing crops particle images from the full frame, eliminating blank space and compressing data by >1000:1. CPI is designed for ummanned use, with AI parameters to optimize performance without supervision.

The 2D-S Stereo Probe is an optical imaging instrument that obtains stereo cloud particle images and concentrations using linear array shadowing. Two diode laser beams cross at right angles and illuminate two linear 128-photodiode arrays. The lasers are single-mode, temperature-stabilized, fiber-coupled diode lasers operating at 45 mW. The optical paths are arbitrarily labeled the “vertical” and “horizontal” probe channels, but the verticality of each channel actually depends on how the probe is oriented on an aircraft. The imaging optical system is based on a Keplerian telescope design having a (theoretical) primary system magnification of 5X, which results in a theoretical effective size of (42.5 µm + 15 µm)/5 = 11.5 µm. However, actual lenses and arrays have tolerances, so it is preferable to measure the actual effective pixel size by dropping several thousands of glass beads with known diameters through the object plane of the optics system.