Cloud optical particle counters (OPCs) count and size particles transiting a sensitive laser region (the sample area) to provide information required to better understand cloud processes and validate models and satellite retrievals. Cloud OPC sizing uncertainty varies from instrument-to-instrument and depends on the transit location with the sample area. Sample area dimensions must be known for calculations of higher-order products and are unique for each probe due to manufacturing tolerances. Cloud OPC sizing performance is commonly evaluated by passing precision glass beads through an instrument’s sample area. The number and transit location of glass beads is unknown, so the method cannot be used to provide position-dependent sizing uncertainty assessments or provide measurements of sample area dimensions. Researchers have developed beam mapping systems that test OPCs by passing a known number of water droplets through the sample area at known locations. Beam mapping systems can provide detailed assessments of sizing uncertainty and precise measurements of sample area dimensions. Seven groups (including Droplet Measurement Technologies) operate beam mapping systems that are immobile and too complex to easily relocate. These systems cannot be feasibly deployed during field campaigns, where detailed assessments of OPC sizing performance and sample area dimensions are highly desirable. This proposal seeks funding for the development of a miniaturized field-deployable beam mapping system which would evolve into a commercially-available product. The work has the potential to greatly increase the availability of state of the art OPC calibration systems that are small/simple enough to be operated during field deployments. The proposed work will also develop a novel method for performing detailed sizing calibrations using information provided by the prototype system. The work addresses the S1.08 subject within Focus Area 9 by improving confidence in cloud measurements.
The proposed innovation has potential applications within the NASA Langley and Glenn research centers. The innovation would enable NASA researchers to produce instrument specific assessments of cloud optical particle counter performance and perform detailed sizing calibrations in both the laboratory and during field campaigns. The innovation is a major improvement over commonly-used glass bead tests that only give general assessments of sizing performance (not calibrations).
The proposed innovation would give groups operating cloud optical particle counters a means to improve confidence in their measurements. A variety of organizations including those focusing on atmospheric research, operational weather modification, and aircraft icing certification could benefit from the proposed deliverables.