← Back to Event List

PhD Defense: Brent McBride


Physics : 401

Date & Time

November 18, 2022, 1:00 pm4:00 pm


ADVISORS: Dr. J. Vanderlei Martins

TITLE: The Hyper-Angular Rainbow Polarimeter: Pre-Launch Calibration, Validation, and Advancements in Cloud Science

ABSTRACT: Modern satellite instruments with spectral, angular, spatial, and polarization capabilities are strongly considered for long-term characterization and classification of Earth signals from space and aircraft. The Hyper-Angular Rainbow Polarimeter (HARP) is a new development in this direction. The HARP is a wide field-of-view, multi-angle, polarized imager that is capable of 120 distinct views on a single ground target across four spectral channels, three linear polarization states, and at narrow nadir spatial resolution (~400 m from 400 km altitude). All of this capability fits inside a 10x10x30 cm housing and was developed at relatively low cost (<$5M USD). This work focuses on AirHARP, the aircraft demonstration of HARP technology. This work develops an adaptable pre-launch calibration for AirHARP that achieves a 0.5% degree of linear polarization measurement accuracy in the lab. AirHARP measurements are validated in total reflectance and polarization, across its FOV and in three spectral bands, within 1% of co-located NASA ACEPOL field data from the Research Scanning Polarimeter (RSP). Calibrated HARP polarization data allows for advancements in cloud science. Using a broad marine stratocumulus cloud observation from the NASA LMOS campaign in 2017, co-located droplet size distribution (DSD) properties are retrieved over a wide spatial field, at 200 m and 600 m pixel resolutions. This is a first for any Earth observing polarimeter. Cloud “cores” and “periphery” areas are identified by correlating DSD properties at sub-km scales. To address the lack of validation opportunities in LMOS, the AirHARP instrument sampling was simulated over DYCOMS-II large-eddy-simulated (LES) cloud fields. Similar retrieval results are found when comparing LMOS field and LES-simulated retrievals at 200 m and 600 m scales. This work concludes that the HARP concept (1) meets community accuracy requirements for modern climate science, (2) provides an unprecedented look at the microphysics of cloud fields, and (3) is a compelling example of high science quality and potential at a low taxpayer cost.