HOLODET

Further Development of the HOLODEC 2 (Holographic Detector for Clouds 2) Instrument

1 October 2010 - 29 February 2012

Lead Scientist: Raymond Shaw

Observatory: AAF, OSC

The HOLODEC 2 instrument measures ice and cloud particle shape (two-dimensional shadowgraph), size, and three-dimensional (3-D) position, via digital in-line holography. It has the advantage of a sample volume that is not particle-size dependent, nor air-speed dependent. It also is able to detect probable crystal-shattering events utilizing 3-D positions of cloud particles. Furthermore, the sample volume is sufficiently large that size distributions for cloud droplets and small ice particles can be obtained from single holograms, thereby sampling a microphysically relevant volume. With this instrument we achieved a significant improvement in cloud and small-ice particle size distributions by taking spatially-localized microphysical samples, by minimizing particle shattering effects, and by accurately constraining sample volume. The HOLODEC 2 instrument was hardened to prepare it for regular use in field campaigns through three major activities: 1) design, configure, and test a new data system for HOLODEC 2 capable of reliably recording and storing data recorded in a typical full field campaign, 2) further develop the hologram processing code by developing tools to allow the user to more easily select parameters for hologram processing and ascertain the quality of the results (this includes further characterization of the instrument resolution and reconstruction quality), and 3) refine or reengineer the subsystems of the instrument as required from the initial test flights results to make it fit for regular field campaign work.