Airborne measurements of cloud particle size, shape, and optical properties such as extinction cross-section are critical for validating satellite remote sensing measurements and weather and climate models. To address the current and future needs of the scientific community making and using these measurements, we propose a multispectral single-particle holographic imaging system which offers several advantages over current techniques. Our approach exploits a novel property of holographic imaging to directly calculate extinction cross-section at multiple wavelengths. Single-particle holographic measurements avoid the computationally expensive processing required by other holographic instruments. The overall project objective is the development of a new instrument capable of imaging cloud droplets and ice crystals and performing spectrally resolved cloud extinction measurements. Here in Phase I, to de-risk the overall project, we propose the development and testing of a simplified breadboard optical system focusing on holographic measurements at a single wavelength with flowing particles to verify the performance of the instrument using several particle standards of known shapes, including those mimicking cloud particles in a laboratory setting.
This project would be highly beneficial to NASA ESD to enhance the characterization of cloud microphysical properties. The instrument would be suitable for deployment on platforms including the DC-8, P-3, B-200, WB-57 and Global Hawk. The instrument is also well suited to validate remote sensing observations and model results, employing identical wavelengths for its imaging and extinction measurements as are used on CALIOP and other LIDAR systems, including those deployed on NASA's airborne science fleet.
The proposed instrument would be invaluable to other entities performing airborne cloud measurements including DOE, NCAR, NOAA, and NSF domestically and NRC (CA), FAAM (UK), SAFIRE (FR) DLR (DE), and others internationally. Future conversion of this technique to a ground-based instrument for characterizing coarse mode aerosol would have broad applications beyond atmospheric science.