Laser hygrometer UAS payload for profiling the thermodynamic state of the Arctic lower atmosphere

Description

It is well recognized that the rate of climate change in the Arctic is larger than elsewhere on Earth. Our degree of understanding of this acceleration remains incomplete in some part because the Arctic has unique and complex couplings and feedbacks between the surface and the atmosphere that in turn modify the radiative balance there differently than elsewhere. One example is the retreat of the summer ice edge, which may be driven by an increase in the downwelling long wave radiative flux in the spring. In turn, this increase is thought to be linked to an increase in atmospheric water vapor and low-level clouds. Mixed-phase clouds also affect the radiative balance. Downwelling long-wave radiation depends on specific humidity, cloud height, and extent. Improved understanding of the formation and stability of mixed-phase clouds is a research priority and requires measurement of the supersaturation conditions within them. There is a need for a miniature airborne sensor payload for profiling the thermodynamic state of the atmosphere that measures water vapor, temperature, and pressure with sufficient precision to derive supersaturation. Physical Sciences Inc. and Princeton University are developing a compact laser hygrometer for high-precision measurements of water vapor, temperature, and pressure that is compatible with the payload resources of small Unmanned Aircraft Systems (UASs) (e.g., InSitu’s ScanEagle or NASC’s ArcticShark) and tethered balloons. We are creating a payload design tailored for operation in the unique Arctic environment, both in and out of clouds either from tethered balloons, which can penetrate clouds safely under icing conditions, or from small fixed-wing UASs. The design fuses newly emerging lasers and electronics fabrication techniques to develop a new class of airborne sensor at a scale of miniaturization not previously achieved. The poster will review the UAS laser hygrometer payload design and its supporting modeling and laboratory measurements as well as our plans to collaborate with InSitu to flight-demonstrate an engineering prototype of the UAS laser hygrometer on a ScanEagle UAS.