High Speed Imaging Flight Probe

The HSI-FPDR, an innovative imaging-based instrument, has been developed specifically for aircraft-based icing cloud studies that require precise measurement of liquid droplets and ice crystals in mixed-phase environments. The HSI can differentiate between spherical and non-spherical particles and compute their respective size and velocity distributions, particle number density, liquid water content (LWC), and ice water content (IWC).

The HSI is a high-speed imaging system that takes advantage of the latest advances in CMOS sensing technology and combines it with an innovative particle illumination method to deliver precise measurements of particulate size and shape. The flight probe incorporates multiple diode lasers that are used to simultaneously illuminate the particulate field from multiple directions. A dedicated laser and photodetector is used to detect the presence of particles in the measurement probe volume. This information is used to pulse the multiple illumination beams. The laser beams are combined by a receiver lens which creates a frozen shadow (or bright-field image) of the particles on the image sensor. The use of multi-angle illumination significantly reduces measurement errors due to depth-of-field variations that are a problem for legacy imaging instruments. The optics and electronics are packaged in a rugged canister design that is proven to be air-worthy. The probe heads are well-heated to prevent ice accretion while flying in extreme icing environments. The pulsed diode lasers used in the probe provides stability, compactness, ruggedness, and high reliability.