Aircraft Based Imaging Probe for the Study of Icing Environments

Icing environments are of great concern in commercial and military aviation. An aircraft-based, imaging probe is being proposed for the reliable and accurate measurement of liquid water content (LWC) and droplet size distributions in environments variously referred to as freezing rain, freezing drizzle, supercooled drizzle drops, and supercooled large drops (SLD). The innovative aspect of the proposed probe is the use of multiple laser beams (of differing wavelengths) to create high quality shadows of individual particles (droplets and ice crystals) on a 2-d CCD array. Conventional aircraft-based probes such as the OAP suffer from measurement uncertainties arising from the detection of droplets that are out-of-focus. The use of multiple intersecting laser beams will also minimize the background noise created by other particles that may be present along the laser beam path but outside of the measurement volume. Finally, the incorporation of a means for differentiating between ice-crystals and droplets, while counting and measuring both, allows computation of water content in both liquid and solid phases. These innovations, and the other features of the probe to be discussed later, directly address the need for aircraft-based icing monitoring systems that NASA has identified in topic A1.02 of the 2003 SBIR solicitation. The Phase I study has clearly demonstrated the feasibility of the probe. A prototype system will be developed in Phase II.