Airborne holographic probe for small ice detection

Contrails formed by aircraft emissions are the major component of the radiative impact of aviation, contributing more to forcing than emitted carbon dioxide and nitrogen oxides combined. Efforts to reduce the negative impacts of aviation on climate must therefore account for contrail formation and require better understanding of contrail formation and ageing. The research community, including NASA scientists, currently lack an appropriate in situ measurement system capable of characterizing the small ice crystals and droplets relevant to contrail formation and aging processes. We propose development of a new cloud probe designed for operation on research aircraft and other platforms capable of measuring the properties of ice crystals, droplets, and aerosols in the size ranges relevant for contrail formation and potentially distinguishing between them. The proposed instrument would use a digital holographic approach that has been previously demonstrated for cloud measurements, but heavily modified to better measure smaller particles than is currently possible with existing approaches. Our system will be capable of delivering the measurements required to better understand contrail formation and related aviation impacts on climate, as well as be applicable to a wide range of commercial applications, such as the detection and classification of airborne allergens, pathogens, and other large particles that have impacts on the atmosphere, plant, animal and human health, and visibility, among others.
Benefits: NASA would benefit from the proposed research by obtaining a prototype instrument at the end of an eventual Phase II project that would be capable of operation during missions focusing on assessing contrail impacts on radiation and climate. Previous relevant missions include the recent joint flight research campaign, ND-MAX, earlier ACCESS missions in the early 2010s, and work with Boeing and other partners involving the ecoDemonstrator. These missions examined the impacts of sustainable aviation fuel on emissions and contrail properties, which are relevant to NASA’s work related to the U.S. goal of net-zero greenhouse gas emission from aviation by 2050. Other relevant NASA applications include work needed to characterize icing as part of the agency’s Aerosciences Evaluation and Test Capabilities (AETC) Portfolio, including the Icing Research Tunnel (IRT) based at NASA Glenn Research Center. The ability to characterize small airborne particles using digital holography, a key component of the proposed instrument, would also benefit work related to assessing potential impacts of lunar dust and other airborne material on astronaut health being performed by the Human Research Program at the Johnson Space Center. Non-NASA applications include meeting a broader need within the atmospheric research community to better characterize small ice crystals and cloud processes related to the formation and propagation of ice in clouds, including mixed phase clouds. This research area is of major interest and importance to several US research organizations, including the Department of Energy, National Science Foundation, and National Oceanographic and Atmospheric Administration, as well as multiple international research groups. The proposed instrument would also benefit efforts related to weather modification, which involve the deliberate formation of ice in clouds to initiate precipitation. These efforts include both publicly funded research, mainly overseas, as well as commercial activities. The core technology underlying our instrument, digital holography, also has much broader non-NASA applications in the fields of aerosol research, dust research, human health research, agricultural research and potential commercial applications related to pathogen monitoring, and exposure research and applications, including exposure to allergens and/or other large particles known to be harmful.