Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
Browse
8 results
Search Results
Item Coherent imaging via temporal heterodyne and spatial shearing methods(Montana State University - Bozeman, College of Letters & Science, 2018) Galloway, Ryan Moore; Chairperson, Graduate Committee: Wm. Randall BabbittAtmospheric turbulence rapidly decreases image quality at long ranges. Here multiple coherent imaging methods are discussed that lead to a new type of active imaging system, which may help mitigate the effects of atmospheric turbulence. This is accomplished via a self-referencing, linear frequency modulated laser signal, where the signal is both offset in transmitter location (spatial shearing), and is demultiplexed in the temporal frequency domain using unique time delays for each transmitter (temporal heterodyne). Spatial shearing allows one to capture a spatial derivative of the object's spatial frequency content, which if properly 'integrated' can be used to reconstruct an atmospheric phase-aberration-corrected image of the object. The system is illustrated from the starting point of temporal digital holography methods, and builds up to the self-referencing scheme. Various coherent imaging methods and situational parameters are compared.Item 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. RepaskyAccording 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.Item Semiconductor laser transmitter for water vapor lidar on Mars(Montana State University - Bozeman, College of Letters & Science, 1998) Switzer, Greggory W.Item Development of a differential absorption LIDAR for identification of carbon sequestration site leakage(Montana State University - Bozeman, College of Letters & Science, 2013) Johnson, William Eric; Chairperson, Graduate Committee: John L. CarlstenThis thesis describes the development and deployment of a near-infrared scanning micropulse differential absorption lidar (DIAL) system for monitoring carbon dioxide sequestration site integrity. The DIAL utilizes a custom-built lidar (light detection and ranging) transmitter system based on two commercial tunable diode lasers operating at 1.571 micron, an acousto-optic modulator, fiber optic switches, and an Erbium-doped fiber amplifier to generate 65 mJ 200 ns pulses at a 15 kHz repetition rate. Backscattered laser transmitter light is collected with an 11 inch Schmidt-Cassegrain telescope where it is optically filtered to reduce background noise. A fiber-coupled photomultiplier tube operating in the photon counting mode is then used to monitor the collected return signal. Averaging over periods typically of one hour permit range-resolved measurements of carbon dioxide from 1 to 2.5 km with a typical error of 40 ppm. For monitoring a field site, the system scans over a field area by pointing the transmitter and receiver with a computer controlled motorized commercial telescope base. The system has made autonomous field measurements in an agricultural field adjacent to Montana State University and at the Kevin Dome carbon sequestration site in rural northern Montana. Comparisons have been made with an in situ sensor showing agreement between the two measurements to within the 40 error of the DIAL. In addition to the work on the 1.57 micron DIAL, this thesis also presents work done at NASA Langley Research Center on the development and deployment of a 2 micron integrated path differential absorption (IPDA) lidar. The 2 micron system utilizes a low repetition rate 140 mJ double pulsed Ho:Tm:YLF laser developed at NASA Langley.Item Synthetic aperture LADAR techniques(Montana State University - Bozeman, College of Letters & Science, 2012) Crouch, Stephen Capdepon; Chairperson, Graduate Committee: Wm. Randall BabbittSynthetic Aperture Ladar (SAL) system performance is generally limited by the chirp ranging sub-system. Use of a high bandwidth linearized chirp laser centered at 1.55 microns enables high resolution ranging. Application of Phase Gradient Autofocus (PGA) to high resolution, stripmap mode SAL images and the first demonstration of Interferometric SAL (IFSAL) for topography mapping are shown in a laboratory setup with cross range resolution commensurate with the high range resolution. Projective SAL imaging is demonstrated as a proof of concept. Finally spotlight mode SAL in monostatic and bistatic configurations is explored.Item Water vapor profiling using a widely tunable amplified diode laser differential absorption lidar (DIAL)(Montana State University - Bozeman, College of Letters & Science, 2007) Obland, Michael Drew; Chairperson, Graduate Committee: Joseph A. ShawWater vapor is one of he most significant constituents of the atmosphere because of its role in cloud formation, precipitation, and interactions with electromagnetic radiation, especially its absorption of longwave infrared radiation. Some details of the role of water and related feedback mechanisms in the Earth system need to be characterized better if local weather, global climate, and the water cycle are to be understood. Water vapor profiles are currently obtained with several remote sensing techniques, such as microwave radiometers, passive instruments like the Atmospheric Emitted Radiance Interferometer (AERI), and Raman lidar. Each of these instruments has some disadvantage, such as only producing column integrated water vapor amounts or being large, overly customized, and costly, making them difficult to use for deployment in networks or onboard satellites to measure water vapor profiles. This thesis work involved the design, construction, and testing of a highly-tunable Differential Absorption Lidar (DIAL) instrument utilizing an all-semiconductor transmitter.Item Use of a two color LIDAR system to study atmospheric aerosols(Montana State University - Bozeman, College of Letters & Science, 2010) Todt, Benjamin David; Chairperson, Graduate Committee: Kevin S. RepaskyThis thesis demonstrates the use of a two color lidar (light detection and ranging) instrument for the purpose of studying atmospheric aerosols. The instrument and the analysis techniques are explained and discussed to provide the necessary back-ground. The calibration is discussed and demonstrated followed by an example of the data analysis. The lidar's combination with a digital camera used to image cloud formations is then discussed and preliminary results are displayed.Item A micro-pulsed LIDAR for the study of the lower troposphere and atmospheric boundary layer(Montana State University - Bozeman, College of Letters & Science, 2012) Casey, Erin Michelle; Chairperson, Graduate Committee: John L. CarlstenThe current largest unknown variable in global climate models is the effect of aerosols directly and indirectly on radiative forcing. This thesis continues the work of characterizing this effect through the study of aerosols by the use of lidar. A micro-pulsed lidar was designed, fabricated and incorporated into a set of instruments for atmospheric studies at Montana State University. The data collected up to this point shows the usefulness of employing such a system in conjunction with other remote sensing instruments as well as in-situ instruments. This is shown by the retrieval of aerosol backscatter and extinction coefficients as well as lapse rates and atmospheric boundary layer heights.