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Item Diode-laser-based high spectral resolution LIDAR(Montana State University - Bozeman, College of Engineering, 2021) Colberg, Luke Stewart; Chairperson, Graduate Committee: Kevin S. RepaskyThis 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.Item 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. RepaskyThermodynamic 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.Item 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.Item 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. ShawPolarization 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.Item 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 LaMeresAs 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.Item Two channel receiver design and implementation for a ground based micro-pulse differential absorption LIDAR (DIAL) instrument(Montana State University - Bozeman, College of Engineering, 2016) Moen, Drew Roland; Chairperson, Graduate Committee: Kevin S. RepaskyCurrent standard water vapor measurement techniques lack the required temporal and spatial resolution needed to further our understanding of the role of water vapor in the Earth's atmosphere. This thesis reports on the continued efforts to bring a cost-effective, autonomous, eye-safe, ground based, micro-pulse differential absorption lidar for the continuous measurement of water vapor into fruition. More specifically, the receiver for this instrument needs a dynamic range of measurement spanning from as close to the Earth's surface as possible, up through the troposphere. Previous reports on this system provide accurate backscatter measurement down to 2 km above the surface. A newly designed receiver has been modeled with the help of Zemax optical design software. It implements a 10% pickoff of the total received light into a second detection channel with a wider field of view. This channel utilizes a free space avalanche photodiode (APD) and has a full angle field of view of ~1 mrad. This channel (the near field) provides accurate backscatter measurement between 600 meters and 5 km in theory. The 90% channel utilizes a fiber coupled APD with a full angle field of view of ~200 microradians. This channel (the far field) has been shown to provide accurate backscatter measurements between 2 km and 12 km. While the near field channel has shown improvement to the overall system, the measured results appear to be accurate down to ~1 km. The results show continuous and autonomous operation with water vapor measurements in close agreement from both detection channels. Further comparisons with radio-sondes provide validation of the water vapor DIAL data product.Item The visible-to-short-wave-infrafred spectrum of skylight polarization(Montana State University - Bozeman, College of Engineering, 2015) Dahl, Laura Marie; Chairperson, Graduate Committee: Joseph A. ShawSkylight becomes partially polarized when sunlight is scattered in the atmosphere. The resulting degree of linear polarization (DoLP) depends on the optical wavelength, atmospheric properties (especially aerosol content), and surface reflectance. The degree of linear polarization for a clear sky was calculated previously for the visible-to-near-infrared (VNIR) spectral range using a successive-orders-of-scattering radiative transfer model and the calculations were validated through comparison with measurements from an all-sky polarization imager. Results from that study showed that VNIR skylight polarization in the visible to the near-infrared spectrum could trend upward, downward, or even have unusual spectral discontinuities that arose because of sharp features in the optical properties of underlying surface and atmospheric aerosols. However, the results were limited to wavelengths below 1 microns from a lack of data at longer wavelengths. This report describes skylight polarization calculations from 0.35 microns to 2.5 microns (visible to SWIR). Inputs to the model included spectral extrapolations of aerosol properties retrieved from a ground-based solar radiometer and measurements of spectral surface reflectance from a hand-held spectrometer. The simulations were run for different environments: a Rayleigh-scattering environment (no aerosol optical depth and no surface reflectance), varied aerosols over a constant-reflectance surface, spectrally constant aerosols over varied surfaces, and a set of more realistic environments that coupled different measured surface reflectance spectra with actual aerosol conditions. Results showed skylight polarization dependence on aerosols and surface reflectance when one element was added, changed, or taken out of an environment. The results were also compared against skylight polarization measurements taken with a SWIR-MWIR polarimeter. Polarization results in the SWIR were highly dependent on the aerosol size distribution and the resulting relationship between the aerosol and Rayleigh optical depths. Once the aerosol optical depth became greater than the Rayleigh optical depth, the predicted polarization deviated significantly from Rayleigh scattering theory. As aerosol optical depths increased, the degree of linear polarization spectrum generally decreased with wavelength at a rate dependent on the aerosol size distribution. Unique polarization features in the modeled results were attributed to the surface reflectance and the skylight DoLP generally decreased as surface reflectance increased.Item All-sky polarization imager deployment at Mauna Loa Observatory, Hawaii(Montana State University - Bozeman, College of Engineering, 2010) Dahlberg, Andrew Richard; Chairperson, Graduate Committee: Joseph A. ShawAn all-sky imaging polarimeter was deployed in summer 2008 to the Mauna Loa Observatory in Hawaii to study clear-sky atmospheric skylight polarization. The imager, designed at Montana State University, operates in five distinct wavebands in the visible region of the spectrum and is capable of imaging the overhead skylight hemisphere with a fisheye lens. This thesis describes the Mauna Loa deployment and presents an initial comparison of these data to those observed by Coulson with a zenith-slice polarimeter in the late 1970s and early 1980s. We show how the all-sky imaging technique yields additional insight to the nature of skylight polarization beyond what is observed in a single zenith scan. It was found that the skylight polarization data collected compared well to that collected by Coulson. Furthermore, the polarization signatures obtained over the two week deployment were found to depend inherently on the underlying cloud cover at altitudes beneath the observatory. The different cloud topologies provided variable upwelling unpolarized light which entered the field of view of the instrument. As a result, the anticipated polarization signatures were reduced by variable amounts from this increased unpolarized radiation countering the strong skylight polarization band observed at 90° from the sun. Finally, to quantify the nature of the upwelling scattered radiation from the clouds to the variation in the degree of polarization, the maximum degree of polarization was fit to a decreasing exponential trend versus upwelling radiance as obtained from overhead satellites. Statistical correlation for these quantities was found to be favorable and this result can potentially yield useful prediction ability for skylight polarization signatures in clear-sky conditions.Item Full sky imaging polarimetry for initial polarized modtran validation(Montana State University - Bozeman, College of Engineering, 2007) Pust, Nathaniel Joel; Chairperson, Graduate Committee: Joseph A. ShawAlthough military studies of the last ten years have shown that visible polarimetry supplies supplemental surveillance information, the polarimetric signatures of ground-based objects greatly depend on the illuminating skylight polarization. The polarization of a pure molecular atmosphere is easily modeled, but aerosols and clouds modify clear-sky polarization substantially. The Air Force has developed a polarimetric atmospheric radiative transfer model (MODTRAN-P) to simulate atmospheric effects. To assist MODTRAN-P code validation, a full-sky visible polarimeter has been developed using liquid crystal variable retarders (LCVRs). Unique calibration issues of LCVR instruments are addressed. A fisheye lens can be exchanged for a telephoto lens to provide system flexibility. This allows comparison between changing sky and changing target signatures.Item Two wavelength Lidar instrument for atmospheric aerosol study(Montana State University - Bozeman, College of Engineering, 2008) Hoffman, David Swick; Chairperson, Graduate Committee: Kevin S. RepaskyA two-color lidar instrument and inversion algorithms have been developed for the study of atmospheric aerosols. The two-color lidar laser transmitter is based on the collinear fundamental 1064 nm and second harmonic 532 nm output of a Nd:YAG laser. Scattered light is collected by the two-color lidar receiver using a Schmidt-Cassegrain telescope with the 532 nm channel monitored using a gated photomultiplier tube (PMT) and the 1064 nm channel monitored using an avalanche photodiode (APD). Data is collected from the PMT and APD using a 14 bit 200 MHz data acquisition card. The lidar inversion algorithm developed to analyze the data collected by the two-color lidar is based on a constant lidar ratio assumption at both the 1064 nm and 532 nm wavelengths with the constrained ratio aerosol model (CRAM) providing the initial lidar ratios at the two wavelengths to complete the lidar inversion. Data from the CALIOP lidar on board the CALIPSO satellite are presented to verify software algorithm performance. Data from the two-color lidar are then presented demonstrating the two-color lidar instrument's capabilities. The analysis of these data identifies smoke and industrial aerosols in the atmosphere above Bozeman. Finally an error analysis of the lidar instrument and accompanying analysis software is presented. The findings of this analysis are that error introduced by the APD and PMT is dominant; the error introduced by the optical detectors is much larger than the error from other sources examined such as quantization error, and the error associated the use of numerical integration in the data analysis algorithm.