Theses and Dissertations at Montana State University (MSU)

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Temperature dependent second harmonic generation studies of materials used in energy conversion applications
(Montana State University - Bozeman, College of Engineering, 2022) McNally, Marshall Traver; Chairperson, Graduate Committee: Robert Walker; This is a manuscript style paper that includes co-authored chapters.
Materials in energy conversion devices often undergo a variety of degradation mechanisms. Solid oxide fuel cell cathodes materials, for example, are subject to surface compositional changes due to material segregation. The extreme operating conditions in these energy conversion devices requires the development of an operando technique that is surface and material specific to accurately probe these degradation mechanisms. Second harmonic generation (SHG) is a surface specific technique that probes the electronic structure of a material using the 2nd order polarizability. Using well characterized materials like Au, Si and NiO, we began investigating how high temperatures (260 °C) and atmospheric composition affected the surface electronic structures. To do this, a custom sample chamber dubbed TROPICS was designed and built to achieve temperature, atmospheric compositional and eventually, electrochemical control. We found that gold's SH intensity was enhanced (3.5 times) when O 2 was present in the atmosphere but this enhancement disappeared at high temperatures. Using data from titrating O 2 into a N 2 atmosphere, we concluded that a monolayer of O 2 was forming on the gold surface, providing backbonding opportunities for gold's free electrons into the partially filled O 2 pi* orbitals. Similar behavior was seen in N-type Si which also showed SH enhancement at room temperature. However, P-type and undoped Si showed no such atmospheric dependent behavior. SHG experiments done with NiO showed decoupled behavior in the electronic structure recovery between the bulk and surface. After heating to 260 °C, the SH signal did not return to pre-heating intensities but required ~60 and ~90 minutes in N 2 and air respectively. The difference in recovery time between N 2 and air could be attributed to interactions between the still paramagnetic NiO electrons and the partially filled O 2 pi* orbitals.
Diode-laser-based high spectral resolution LIDAR
(Montana State University - Bozeman, College of Engineering, 2021) Colberg, Luke Stewart; Chairperson, Graduate Committee: Kevin S. Repasky
This thesis describes the design, construction, and testing of a high spectral resolution lidar (HSRL) as a part of a combined HSRL and differential absorption lidar (DIAL) system. The combined HSRL and DIAL instrument is constructed using the MicroPulse DIAL (MPD) architecture and uses distributed Bragg reflector lasers. The MPD architecture is unique because it is eye-safe and cost-effective; therefore, it is ideal for creating a network of ground-based lidars. This instrument is designed for thermodynamic profiling of the lower troposphere. A network of these instruments would be helpful for wide-scale atmospheric monitoring for weather forecasting and climate science. The purpose of the HSRL is to retrieve the optical properties of aerosols in the lower troposphere. The HSRL uses the DIAL offline laser, which has a wavelength of 770.1085 nm, and a potassium vapor cell as the spectral filter. The data retrieved from the HSRL provides the aerosol backscatter coefficient and the backscatter ratio up to an altitude of 7 km during nighttime operation and 5 km during daytime operation. The time resolution for these measurements is 5 minutes, and the range resolution is 150 m. These aerosol optical properties are valuable for aerosol studies and climate modeling; aerosols introduce the most significant degree of uncertainty in modeling the heat flux of the atmosphere. Additionally, these aerosol optical properties can be used to find the planetary boundary layer height (PBLH). The planetary boundary layer controls the exchange of heat, water vapor, aerosols, and momentum between the surface and the atmosphere. It has been demonstrated that the PBLH strongly affects turbulent mixing, convective transport, and cloud entrainment, which makes the PBLH an important parameter for weather forecasting and climate modeling. Despite its significance in atmospheric science, there is no standard method for defining the PBLH. A retrieval method for finding the daytime PBLH using HSRL data is proposed, and data comparisons to radiosonde PBLH retrievals are provided. The algorithm shows a good agreement with the radiosonde retrievals for conditions with a well-behaved boundary layer.
Extracting abstract spatio-temporal features of weather phenomena for autoencoder transfer learning
(Montana State University - Bozeman, College of Engineering, 2020) McAllister, Richard Arthur; Chairperson, Graduate Committee: John Sheppard
In this dissertation we develop ways to discover encodings within autoencoders that can be used to exchange information among neural network models. We begin by verifying that autoencoders can be used to make predictions in the meteorological domain, specifically for wind vector determination. We use unsupervised pre-training of stacked autoencoders to construct multilayer perceptrons to accomplish this task. We then discuss the role of our approach as an important step in positioning Empirical Weather Prediction as a viable alternative to Numerical Weather Prediction. We continue by exploring the spatial extensibility of the previously developed models, observing that different areas in the atmosphere may be influenced unique forces. We use stacked autoencoders to generalize across an area of the atmosphere, expanding the application of networks trained in one area to the surrounding areas. As a prelude to exploring transfer learning, we demonstrate that a stacked autoencoder is capable of capturing knowledge universal to these dataspaces. Following this we observe that in extremely large dataspaces, a single neural network covering that space may not be effective, and generating large numbers of deep neural networks is not feasible. Using functional data analysis and spatial statistics we analyze deep networks trained from stacked autoencoders in a spatiotemporal application area to determine the extent to which knowledge can be transferred to similar regions. Our results indicate high likelihood that spatial correlation can be exploited if it can be identified prior to training. We then observe that artificial neural networks, being essentially black-box processes, would benefit by having effective methods for preserving knowledge for successive generations of training. We develop an approach to preserving knowledge encoded in the hidden layers of several ANN's and collect this knowledge in networks that more effectively make predictions over subdivisions of the entire dataspace. We show that this method has an accuracy advantage over the single-network approach. We extend the previously developed methodology, adding a non-parametric method for determining transferrable encoded knowledge. We also analyze new datasets, focusing on the ability for models trained in this fashion to be transferred to operating on other storms.
Results of a micro pulse differential absorption LIDAR for temperature profiling and analysis code
(Montana State University - Bozeman, College of Engineering, 2021) Cruikshank, Owen Daniel; Chairperson, Graduate Committee: Kevin S. Repasky
Thermodynamic profiling of the lower troposphere is necessary for the study of weather and climate. The micropulse DIAL (differential absorption lidar), or MPD, presented here is designed to fill the need. The MPD is eye-safe and can run autonomously for continuous measurements compared to technologies with similar measurement capabilities like Raman lidar. Using a temperature-sensitive absorption line of O 2, the MPD system can measure the absorption of O 2 in the lower troposphere as a function of range and convert that measurement to temperature as a function of range. This process relies on a perturbative correction to the absorption retrieval to account for the fact that the O 2 absorption spectral linewidth is similar to the molecular Rayleigh scattering linewidth. An ancillary measurement of the ratio of aerosol backscatter to molecular backscatter is required for the correction. The integrated high spectral resolution lidar (HSRL) uses a heated potassium vapor notch filter to make the aerosol-to-molecular ratio measurement. An analysis program in MATLAB was written to take in raw lidar data and produce a temperature product of range and time. Results presented from a campaign at the Atmospheric Radiation Measurements program Southern Great Plains site in Oklahoma in spring 2019 show temperature comparisons with radiosonde measurements with a mean difference between radiosonde and MPD measurements of -1.1K and a standard deviation of 2.7 K. Further results from an instrument on the Montana State University campus in Bozeman and at the National Center for Atmospheric Research in Boulder, Colorado have shown that the MPD instrument can produce measurements autonomously for periods of weeks to months.
Stigmatic spectroscopy of the solar atmosphere in the vacuum-ultraviolet
(Montana State University - Bozeman, College of Letters & Science, 2020) Courrier, Hans Thomas; Chairperson, Graduate Committee: Charles C. Kankelborg; Charles C. Kankelborg was a co-author of the article, 'Using local correlation tracking to recover solar spectral information from a slitless spectrograph' in the journal 'Journal of astronomical telescopes and imaging systems, SPIE' which is contained within this dissertation.; Charles C. Kankelborg, Bart De Pontieu and Jean-Pierre Wulser were co-authors of the article, 'An on orbit determination of point spread functions for the interface region imaging spectrograph' in the journal 'Solar physics' which is contained within this dissertation.; Charles C. Kankelborg, Amy R. Winebarger, Ken Kobayashi, Brent Beabout, Dyana Beabout, Ben Carroll, Jonathan W. Cirtain, James A. Duffy, Carlos Gomez, Eric M. Gullikson, Micah Johnson, Jacob D.Parker, Laurel A. Rachmeler, Roy T. Smart, Larry Springer and David L. Windt were co-authors of the article, 'The EUV snapshot imaging spectrograph (ESIS)' which is contained within this dissertation.
The solar atmosphere presents a complicated observing target since tremendous variability exists in solar features over a wide range of spatial, spectral, and temporal scales. Stigmatic spectrographs are indispensable tools that provide simultaneous access to spatial context and spectroscopy, enabling the diagnosis of solar events that cannot be accomplished by imaging or spectroscopy alone. In this dissertation I develop and apply a novel technique for on orbit spectrograph calibration, recover co-temporal Doppler shifts of widely spaced solar features, and describe a new design for a slitless solar spectrograph. The Interface Region Imaging Spectrograph, (IRIS) is currently the highest spatial and spectral resolution, space based, solar spectrograph. Ongoing calibration is important to maintaining the quality of IRIS data. Using a Mercury transit against the backdrop of the dynamic solar atmosphere, I characterize the spatial point spread functions of the spectrograph with a unique, iterative, blind, deconvolution algorithm. An associated deconvolution routine improves the ability of IRIS to resolve spatially compact solar features. This technique is made freely available to the community for use with past and future IRIS observations. The Multi-Order Extreme Ultraviolet Spectrograph (MOSES) is a slitless spectrograph that collects co-temporal, but overlapping spatial and spectral images of solar spectral lines. Untangling these images presents an ill-posed inversion problem. I develop a fast, automated method that returns Doppler shifts of compact solar objects over the entire MOSES field of view with a minimum of effort and interpretation bias. The Extreme ultraviolet Snapshot Imaging Spectrograph (ESIS) is a slitless spectrograph that extends the MOSES concept. I describe this new instrument, which is far more complex and distinct as compared to MOSES, and the contributions I made in the form of optical design and optimization. ESIS will improve the quality of spatial and spectral information obtained from compact and extended solar features, and represents the next step in solar slitless spectroscopy. Taken together, these contributions advance the field by supporting existing instrumentation and by developing new instrumentation and techniques for future observations of the solar atmosphere.
Combining spectral and polarimetric methods to classify cloud thermodynamic phase
(Montana State University - Bozeman, College of Engineering, 2019) Tauc, Martin Jan; Chairperson, Graduate Committee: Joseph A. Shaw; David W. Riesland, Laura M. Eshelman, Wataru Nakagawa and Joseph A. Shaw were co-authors of the article, 'Radiance ratios for CTP discrimination' submitted to the journal 'Journal of applied remote sensing' which is contained within this thesis.; Wataru Nakagawa and Joseph A. Shaw were co-authors of the article, 'The SWIR three-channel polarimeter for cloud thermodynamic phase detection' in the journal 'Optical engineering' which is contained within this thesis.
Cloud thermodynamic phase--whether a cloud is composed of spherical water droplets or polyhedral ice crystals--is an important parameter for optical communication with space-based instruments, remote sensing of the atmosphere, and, perhaps most importantly, understanding weather and climate. Although some methods exist to detect the phase of clouds, there is still a need for passive remote sensing of cloud thermodynamic phase due to its low-cost, scalability, and ease of use. Two methods for cloud thermodynamic phase classification employ spectral radiance ratios in the short-wave infrared, and the S 1 Stokes parameter, a polarimetric quantity. In this dissertation, the combination of the two methods is realized in an instrument called the short-wave infrared three-channel polarimeter. The coalescence of radiance ratios in the short-wave infrared and polarization channels oriented parallel and perpendicular to the scattering plane provides better classification of cloud phase than either method independently. Despite the improvement, the low-cost system suffered from hardware and software limitations, which caused an increase in noise and polarimetric artifacts. These errors are analyzed and a subset of low-noise data shows even better classification ability. All together, the results attained from the deployment of the polarimeter in early 2019 showed promise that the combination of the two methods is an improvement over past techniques.
Measuring methane emissions from American bison (Bison bison L.) using eddy covariance
(Montana State University - Bozeman, College of Agriculture, 2019) Cook, Adam Anderson; Chairperson, Graduate Committee: Paul C. Stoy
American bison (Bison bison L.) have recovered from the brink of extinction over the past century. Bison offer potential environmental benefits as they re-occupy their native range, but many specific impacts of bison reintroduction are not well understood. Methane emissions are known to be a major climate impact of ruminants, but few measurements for bison exist due to challenges caused by their mobile grazing habits and safety issues associated with direct measurements. Here, we measure the methane and carbon dioxide fluxes from a bison herd on winter range using the eddy covariance technique. Methane emissions were negligible (mean = 0.0024 micromole m -2 s -1, SD = 0.0102 micromole m -2 s -1) before and after bison grazed in the area sampled by the eddy covariance flux footprint with the exception of a single spike possibly attributable to thawing soil or the presence of white-tailed deer (Odocoileus virginianus Z.). Methane fluxes when bison were present in the study area averaged 0.041 micromole m -2 s -1 (SD = 0.046 micromole m -2 s -1), similar to previous measurements over sheep and cattle pastures, but with little diurnal pattern due to a lack of consistent bison movement habits over the course of each day. An eddy covariance flux footprint analysis coupled to bison location estimates from automated camera images calculated methane flux with a median of 56.5 micromole s -1 per animal and a mean of 91.6 micromole s-1 per animal, approximately 50 and 75% of established emission rates for range cattle, respectively. Eddy covariance measurements are a promising way to measure methane and carbon dioxide flux from large ruminants on native range and we recommend comparisons amongst alternate grazing systems to help identify management strategies that are cognizant of climate.
A study of atmospheric polarization in unique scattering conditions at twilight, during a solar eclipse, and for cloud phase retrievals using all-sky polarization imaging
(Montana State University - Bozeman, College of Engineering, 2018) Eschelman, Laura Marie; Chairperson, Graduate Committee: Joseph A. Shaw
Polarization is a fundamental property of light that can be detected with polarization-sensitive instruments for many remote sensing applications. To quantitatively interpret the remote sensing data, an understanding how naturally occurring polarization depends on wavelength and environmental parameters is needed. The most obvious source of naturally occurring polarization is atmospheric scattering. For a clear-sky environment, Rayleigh scattering dominates, resulting from scattering by atmospheric gas molecules that are much smaller than the optical wavelength, and a distinct all-sky polarization pattern exists. A band of maximum degree of linear polarization can be observed 90? from the sun with polarization vectors orientated perpendicular to the scattering plane (i.e. the plane containing the incident and scattered light). However, aerosols, clouds, and underlying surface reflectance can alter the observed sky polarization. Military, environmental, and navigational applications exploit the sky polarization pattern to detect objects, retrieve aerosol and cloud properties, and to find compass headings based on the sky polarization pattern. Sky polarization is also being used to calibrate the polarization response of large telescopes. It is important to understand how partially polarized skylight can vary with environmental factors, as well as with wavelength and solar position, so that polarization measurements can be interpreted correctly. The direction of polarization when aligned to a specific reference frame can provide additional information beyond the basic polarization pattern. This dissertation expands the current knowledge of skylight polarization by validating radiative transfer simulations in the shortwave infrared, by reporting the first-ever retrievals of cloud thermodynamic phase from all-sky polarization images using the Stokes S1 parameter referenced in the scattering plane, and by quantifying how partially polarized skylight varied under unique scattering conditions during the 2017 solar eclipse. In order to accurately predict cloud thermodynamic phase and to analyze the temporal distribution of skylight during a total solar eclipse, a physics-based understanding of the Stokes parameters and angle of polarization (AoP) with respect to the instrument, scattering, and solar principal planes was also developed. Through each experiment, two underlying threads were observed. First, in order to accurately interpret results, environmental parameters needed to be characterized. Second, when rotated into a specific reference frame, the Stokes parameters and AoP can be utilized differently and provide unique insights when analyzing all-sky polarization data.
Design, fabrication, and implementation of an embedded flight computer in support of the ionospheric-thermospheric scanning photometer for ion-neutral studies CubeSat mission
(Montana State University - Bozeman, College of Engineering, 2017) Handley, Matthew Lee; Chairperson, Graduate Committee: Brock LaMeres
As society increasingly relies on space-based assets for everything from GPS-based directions and global communications to human-driven research on the ISS, our understanding of space weather becomes vital. Timely predictions of a solar storm's impact on the ionosphere are imperative to safing these assets before damaging storms hit, while minimizing downtime during lighter storms. The topside transition region (TTR) is a global boundary where the concentration of O+ significantly decreases due to charge exchange with H+ and He+ from the thermosphere, as well as protons and neutral atomic oxygen from the plasmasphere. When high-energy electrons in the ionosphere intercept O+ ions, they combine and release photons at 135.6-nm. The Ionospheric-Thermospheric Scanning Photometer for Ion-Neutral Studies (IT-SPINS) mission will provide 135.6-nm nightglow measurements from a 3U CubeSat equipped with a high-sensitivity UV photometer. The CubeSat will spin about orbit normal, sweeping its photometer field of view through the ionosphere. Ground-based post processing will yield 2D altitude/in-track images of O+ density, providing weighting parameters for models of the TTR. This low-earth orbit (LEO) small satellite mission is a collaboration between the John Hopkins University Applied Physics Laboratory, SRI International, and Montana State University (MSU). This research describes the design, fabrication, and implementation of the space flight computer (SFC) hardware and software responsible for handling all commands, telemetry, and scientific data required by this National Science Foundation (NSF) funded mission. The SFC design balances requirements derived from the mission objectives while leveraging heritage hardware and software from MSU's many successful CubeSat missions (HRBE, FIREBIRD, FIREBIRD-II) and payloads (EPISEM) [1-3]. This low-power (100 mW) embedded computer features dual 16- bit PIC microcontrollers running at 16 MHz with only 96 kB of RAM and runs the microC/OS-II real-time operating system (RTOS). The SFC also includes a TCXO-driven mission elapsed time clock with plus or minus 2 ppm temperatures stability, a 1 GB NAND flash for data storage, and interfaces to all other subsystems in the satellite. The SFC has passed all standalone testing. It is currently being integrated and tested with the entire IT-SPINS spacecraft and is planned to fly in late 2018.
Development of a micro pulsed LIDAR and a singly-resonant optical parametric oscillator for CO 2 DIAL for use in atmospheric studies
(Montana State University - Bozeman, College of Letters & Science, 2017) Chantjaroen, Chat; Chairperson, Graduate Committee: Kevin S. Repasky
According to the Fifth Assessment Report (AR5) from the Intergovernmental Panel on Climate Change (IPCC), aerosols and CO 2 are the largest contributors to anthropogenic radiative forcing--net negative for aerosols and positive for CO 2. This relates to the amount of impact that aerosols and CO 2 can have on our atmosphere and climate system. CO 2 is the predominant greenhouse gas in the atmosphere and causes great impacts on our climate system. Recent studies show that a less well known atmospheric component--aerosols, which are solid particles or liquid droplets suspended in air, can cause great impact on our climate system too. They can affect our climate directly by absorbing and scattering sunlight to warm or cool our climate. They can also affect our climate indirectly by affecting cloud microphysical properties. Typically sulfate aerosols or sea salts act as condensation nuclei for clouds to form. Clouds are estimated to shade about 60% of the earth at any given time. They are preventing much of the sunlight from reaching the earth's surface and are helping with the flow of the global water cycle. These are what permit lifeforms on earth. In the IPCC report, both aerosols and CO 2 also have the largest uncertainties and aerosols remains at a low level of scientific understanding. These indicate the need of more accurate measurements and that new technologies and instruments needs to be developed. This dissertation focuses on the development of two instruments--a scannable Micro Pulsed Lidar (MPL) for atmospheric aerosol measurements and an Optical Parametric Oscillator (OPO) for use as a transmitter in a Differential Absorption Lidar (DIAL) for atmospheric CO2 measurements. The MPL demonstrates successful measurements of aerosols. It provides the total aerosol optical depth (AOD) and aerosol lidar ratio (S a) that agree well with an instrument used by the Aerosol Robotic Network (AERONET). It also successfully provides range-resolved information about aerosols that AERONET instrument is incapable of. The range-resolved information is important in the study of the sources and sinks of aerosols. The OPO results show good promise for its use as a DIAL transmitter.

Theses and Dissertations at Montana State University (MSU)

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