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University of Colorado
1.
Blum, Lauren Weber.
Relativistic Electrons in Earth’s Outer Radiation Belt: Wave-Particle Interactions and Precipitation Loss.
Degree: PhD, Aerospace Engineering Sciences, 2014, University of Colorado
URL: https://scholar.colorado.edu/asen_gradetds/3 
► Earth's outer radiation belt is a highly dynamic region of the magnetosphere composed of relativistic electrons with often unpredictable variations in energy and spatial…
(more)
▼ Earth's outer radiation belt is a highly dynamic region of the magnetosphere composed of relativistic electrons with often unpredictable variations in energy and spatial extent. Understanding this variable radiation environment is critical for protecting both spacecraft and humans in space. A number of competing acceleration and loss processes combine to produce net enhancements or depletions of the outer radiation belt. Electron precipitation into the atmosphere is a critical part of this loss, and quantified understanding of this mechanism is needed in order to understand and ultimately predict radiation belt dynamics. In the following work, we investigate the contribution of electron precipitation to radiation belt losses, looking at what times precipitation is important and at how much loss it contributes. Through a combination of long-term existing data sets as well as new CubeSat measurements we perform both statistical and detailed event studies to better understand the nature and extent of MeV electron loss to the atmosphere. We analyze measurements of precipitating electrons directly as well as electromagnetic waves that may be causing this precipitation. Our studies provide a more cohesive picture of outer radiation belt dynamics and the relationship between precipitating energetic electrons and global magnetospheric conditions.
Advisors/Committee Members: Xinlin Li, Dan Baker, Zoltan Sternovsky.
Subjects/Keywords: magnetosphere; precipitation; radiation belts; wave-particle interactions; Aerospace Engineering; Plasma and Beam Physics
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APA (6th Edition):
Blum, L. W. (2014). Relativistic Electrons in Earth’s Outer Radiation Belt: Wave-Particle Interactions and Precipitation Loss. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/3
Chicago Manual of Style (16th Edition):
Blum, Lauren Weber. “Relativistic Electrons in Earth’s Outer Radiation Belt: Wave-Particle Interactions and Precipitation Loss.” 2014. Doctoral Dissertation, University of Colorado. Accessed February 25, 2021.
https://scholar.colorado.edu/asen_gradetds/3.
MLA Handbook (7th Edition):
Blum, Lauren Weber. “Relativistic Electrons in Earth’s Outer Radiation Belt: Wave-Particle Interactions and Precipitation Loss.” 2014. Web. 25 Feb 2021.
Vancouver:
Blum LW. Relativistic Electrons in Earth’s Outer Radiation Belt: Wave-Particle Interactions and Precipitation Loss. [Internet] [Doctoral dissertation]. University of Colorado; 2014. [cited 2021 Feb 25].
Available from: https://scholar.colorado.edu/asen_gradetds/3.
Council of Science Editors:
Blum LW. Relativistic Electrons in Earth’s Outer Radiation Belt: Wave-Particle Interactions and Precipitation Loss. [Doctoral Dissertation]. University of Colorado; 2014. Available from: https://scholar.colorado.edu/asen_gradetds/3
University of Colorado
2.
Truesdale, Nicholas Andrew.
Modular and Reusable Power System Design for the BRRISON Balloon Telescope.
Degree: MSAeroE, Aerospace Engineering Sciences, 2013, University of Colorado
URL: https://scholar.colorado.edu/asen_gradetds/75
► High altitude balloons are emerging as low-cost alternatives to orbital satellites in the field of telescopic observation. The near-space environment of balloons allows optics…
(more)
▼ High altitude balloons are emerging as low-cost alternatives to orbital satellites in the field of telescopic observation. The near-space environment of balloons allows optics to perform near their diffraction limit. In practice, this implies that a telescope similar to the Hubble Space Telescope could be fl own for a cost of tens of millions as opposed to billions.
While highly feasible, the design of a balloon telescope to rival Hubble is limited by funding. Until a prototype is proven and more support for balloon science is gained, projects remain limited in both hardware costs and man hours. Thus, to effectively create and support balloon payloads, engineering designs must be effcient, modular, and if possible reusable. This thesis focuses specifically on a modular power system design for the BRRISON comet-observing balloon telescope. Time- and cost-saving techniques are developed that can be used for future missions.
In this thesis, a modular design process is achieved through the development of individual circuit elements that span a wide range of capabilities. Circuits for power conversion, switching and sensing are designed to be combined in any configuration. These include DC-DC regulators, MOSFET drivers for switching, isolated switches, current sensors and voltage sensing ADCs. Emphasis is also placed on commercially available hardware. Pre-fabricated DC-DC converters and an Arduino microcontroller simplify the design process and offer proven, cost-effective performance.
The design of the BRRISON power system is developed from these low-level circuits. A board for main power distribution supports the majority of flight electronics, and is extensible to additional hardware in future applications. An ATX computer power supply is developed, allowing the use of a commercial ATX motherboard as the fl ight computer. The addition of new capabilities is explored in the form of a heater control board. Finally, the power system as a whole is described, and its overall performance analyzed. The success of the BRRISON power system during testing and fl ight proves its utility, both for BRRISON and for future balloon telescopes.
Advisors/Committee Members: Scott Palo, Eliot F. Young, Zoltan Sternovsky.
Subjects/Keywords: Balloon; BRRISON; ISON; NASA; Power; UVVIS; high altitude; telescopic observation; Aeronautical Vehicles; Electrical and Electronics; Systems Engineering and Multidisciplinary Design Optimization
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APA (6th Edition):
Truesdale, N. A. (2013). Modular and Reusable Power System Design for the BRRISON Balloon Telescope. (Masters Thesis). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/75
Chicago Manual of Style (16th Edition):
Truesdale, Nicholas Andrew. “Modular and Reusable Power System Design for the BRRISON Balloon Telescope.” 2013. Masters Thesis, University of Colorado. Accessed February 25, 2021.
https://scholar.colorado.edu/asen_gradetds/75.
MLA Handbook (7th Edition):
Truesdale, Nicholas Andrew. “Modular and Reusable Power System Design for the BRRISON Balloon Telescope.” 2013. Web. 25 Feb 2021.
Vancouver:
Truesdale NA. Modular and Reusable Power System Design for the BRRISON Balloon Telescope. [Internet] [Masters thesis]. University of Colorado; 2013. [cited 2021 Feb 25].
Available from: https://scholar.colorado.edu/asen_gradetds/75.
Council of Science Editors:
Truesdale NA. Modular and Reusable Power System Design for the BRRISON Balloon Telescope. [Masters Thesis]. University of Colorado; 2013. Available from: https://scholar.colorado.edu/asen_gradetds/75
University of Colorado
3.
Barry, Ian Forest.
Application of the Na-DEMOF Atomic Filter to 3-Frequency Na Doppler Lidar Observations of Wind and Temperature in the Lower Atmosphere.
Degree: MA, Aerospace Engineering Sciences, 2015, University of Colorado
URL: https://scholar.colorado.edu/asen_gradetds/126
► Lidar systems comprise one of several indispensable tools for derivation of wind, density, and temperature profiles in the atmosphere. 3-frequency resonance-fluorescence lidars are particularly…
(more)
▼ Lidar systems comprise one of several indispensable tools for derivation of wind, density, and temperature profiles in the atmosphere. 3-frequency resonance-fluorescence lidars are particularly useful for high-resolution profiles of all three quantities derived simultaneously. However, these lidars depend on atomic species restricted to the metal layers in the middle and upper atmosphere as frequency discriminators, and are not optimized for derivation of these quantities in the lower atmosphere. Rayleigh Doppler lidars typically applied to this region face other restrictions, such as dependence on high-power transmitted lasers, lack of absolute frequency references, and inabilities to derive multiple atmospheric quantities simultaneously without expensive additional transmitter and receiver channels.
A proposed solution to these difficulties is the sodium double-edge magneto-optic filter, (Na-DEMOF), which provides a frequency discriminator for the Rayleigh signal returned by the lower atmosphere and allows 3-frequency Na Doppler lidars to derive atmospheric quantity profiles within the lower atmosphere as well as within the mesospheric and lower thermospheric (MLT) metal layers.
This thesis describes the design, benefits, and restrictions of Na-DEMOFs, and uses the application methods and most recent results of the Na-DEMOFs constructed and tested by the Chu lidar group to demonstrate their successful application to simultaneous derivation of meridional and zonal winds along with temperature.
Advisors/Committee Members: Xinzhao Chu, Wentao Huang, Zoltan Sternovsky.
Subjects/Keywords: atmospheric Doppler lidars; atomic filter; magneto-optic filter; meridional winds; temperature; zonal winds; Atmospheric Sciences; Remote Sensing; Systems Engineering and Multidisciplinary Design Optimization
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APA (6th Edition):
Barry, I. F. (2015). Application of the Na-DEMOF Atomic Filter to 3-Frequency Na Doppler Lidar Observations of Wind and Temperature in the Lower Atmosphere. (Masters Thesis). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/126
Chicago Manual of Style (16th Edition):
Barry, Ian Forest. “Application of the Na-DEMOF Atomic Filter to 3-Frequency Na Doppler Lidar Observations of Wind and Temperature in the Lower Atmosphere.” 2015. Masters Thesis, University of Colorado. Accessed February 25, 2021.
https://scholar.colorado.edu/asen_gradetds/126.
MLA Handbook (7th Edition):
Barry, Ian Forest. “Application of the Na-DEMOF Atomic Filter to 3-Frequency Na Doppler Lidar Observations of Wind and Temperature in the Lower Atmosphere.” 2015. Web. 25 Feb 2021.
Vancouver:
Barry IF. Application of the Na-DEMOF Atomic Filter to 3-Frequency Na Doppler Lidar Observations of Wind and Temperature in the Lower Atmosphere. [Internet] [Masters thesis]. University of Colorado; 2015. [cited 2021 Feb 25].
Available from: https://scholar.colorado.edu/asen_gradetds/126.
Council of Science Editors:
Barry IF. Application of the Na-DEMOF Atomic Filter to 3-Frequency Na Doppler Lidar Observations of Wind and Temperature in the Lower Atmosphere. [Masters Thesis]. University of Colorado; 2015. Available from: https://scholar.colorado.edu/asen_gradetds/126
University of Colorado
4.
O'Brien, Leela Elise.
The Nano Dust Analyzer for the Detection and Analysis of Nanometer-Sized Particles from the Inner Heliosphere.
Degree: PhD, 2017, University of Colorado
URL: https://scholar.colorado.edu/asen_gradetds/225
► The Nano-Dust Analyzer (NDA) instrument is developed for the detection and compositional analysis of nanometer-sized dust particles originating near the Sun, and delivered near…
(more)
▼ The Nano-Dust Analyzer (NDA) instrument is developed for the detection and compositional analysis of nanometer-sized dust particles originating near the Sun, and delivered near Earth’s orbit by radiation pressure and electromagnetic forces. These particles report on processes occurring close to the Sun. This thesis investigates the basic dynamical processes and the results of the numerical calculations are then used to design and optimize the NDA, a linear time-of-flight mass analyzer. The challenge of needing high sensitivity of detection while pointed close to Sun’s direction is solved by optimizing the instrument’s field-of-view, pointing requirements, and designing an internal baffle system to suppress the effects of solar-ultraviolet radiation. Little is known about the origin, distribution and fate of dust particles in the inner Solar System. The interplanetary dust complex is fed mostly by comets and asteroids. The interplanetary dust particles are transported towards the Sun (on timescales of ~ thousands of years) where they undergo multiple processes: most are destroyed by the heat of the Sun or sputtering by solar wind particles, while a small fraction is expelled out of the Solar System. Grinding from mutual collisions alters their size distribution, which intensifies closer to the Sun, where their density increases. These particles influence the solar wind plasma, being one of the sources of inner source pickup ions, or mass loading the expanding solar wind. The importance of these effects is yet to be fully understood. The population of particles expelled from the Solar System include submicron-sized dust particles known as <i>β</i>-meteoroids, which are accelerated by solar radiation pressure. Nanometer-sized particles also belong to this population and are picked up and accelerated to high velocities by the solar wind. There is likely a wealth of information in their mass distribution, composition and dynamical properties, including their temporal and spatial flux variations, which is influenced by their interaction with the solar wind. Past missions have identified and partially-characterized particles originating from the inner Solar System. This thesis lays the foundations for providing measurements to resolve outstanding science questions by presenting a concept for their detection and a basic design for a capable instrument.
Advisors/Committee Members: Zoltan Sternovsky, Mihaly Horanyi, Delores Knipp, Xinlin Li, David Malaspina.
Subjects/Keywords: the nano-dust analyzer; solar system; dust particles; nanometer-sized; solar wind; Aerospace Engineering; Remote Sensing
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APA (6th Edition):
O'Brien, L. E. (2017). The Nano Dust Analyzer for the Detection and Analysis of Nanometer-Sized Particles from the Inner Heliosphere. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/225
Chicago Manual of Style (16th Edition):
O'Brien, Leela Elise. “The Nano Dust Analyzer for the Detection and Analysis of Nanometer-Sized Particles from the Inner Heliosphere.” 2017. Doctoral Dissertation, University of Colorado. Accessed February 25, 2021.
https://scholar.colorado.edu/asen_gradetds/225.
MLA Handbook (7th Edition):
O'Brien, Leela Elise. “The Nano Dust Analyzer for the Detection and Analysis of Nanometer-Sized Particles from the Inner Heliosphere.” 2017. Web. 25 Feb 2021.
Vancouver:
O'Brien LE. The Nano Dust Analyzer for the Detection and Analysis of Nanometer-Sized Particles from the Inner Heliosphere. [Internet] [Doctoral dissertation]. University of Colorado; 2017. [cited 2021 Feb 25].
Available from: https://scholar.colorado.edu/asen_gradetds/225.
Council of Science Editors:
O'Brien LE. The Nano Dust Analyzer for the Detection and Analysis of Nanometer-Sized Particles from the Inner Heliosphere. [Doctoral Dissertation]. University of Colorado; 2017. Available from: https://scholar.colorado.edu/asen_gradetds/225
University of Colorado
5.
Bennett, Trevor John.
On-Orbit 3-Dimensional Electrostatic Detumble for Generic Spacecraft Geometries.
Degree: PhD, 2017, University of Colorado
URL: https://scholar.colorado.edu/asen_gradetds/226
► In recent years, there is a growing interest in active debris removal and on-orbit servicing of Earth orbiting assets. The growing need for such…
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▼ In recent years, there is a growing interest in active debris removal and on-orbit servicing of Earth orbiting assets. The growing need for such approaches is often exemplified by the Iridium-Kosmos collision in 2009 that generated thousands of debris fragments. There exists a variety of active debris removal and on-orbit servicing technologies in development. Conventional docking mechanisms and mechanical capture by actuated manipulators, exemplified by NASA's Restore-L mission, require slow target tumble rates or more aggressive circumnavigation rate matching. The tumble rate limitations can be overcome with flexible capture systems such nets, harpoons, or tethers yet these systems require complex deployment, towing, and/or interfacing strategies to avoid servicer and target damage. Alternatively, touchless methods overcome the tumble rate limitations by provide detumble control prior to a mechanical interface. This thesis explores electrostatic detumble technology to touchlessly reduce large target rotation rates of Geostationary satellites and debris. The technical challenges preceding flight implementation largely reside in the long-duration formation flying guidance, navigation, and control of a servicer spacecraft equipped with electrostatic charge transfer capability. Leveraging prior research into the electrostatic charging of spacecraft, electrostatic detumble control formulations are developed for both axisymmetric and generic target geometries. A novel relative position vector and associated relative orbit control approach is created to manage the long-duration proximity operations. Through detailed numerical simulations, the proposed detumble and relative motion control formulations demonstrate detumble of several thousand kilogram spacecraft tumbling at several degrees per second in only several days. The availability, either through modeling or sensing, of the relative attitude, relative position, and electrostatic potential are among key concerns with implementation of electrostatic detumble control on-orbit. Leveraging an extended Kalman filter scheme, the relative position information is readily obtained. In order to touchlessly acquire the target electrostatic potential, a nested two-time scale Kalman filter is employed to provide real-time estimates of both relative position and electrostatic potential while on-orbit. The culmination of the presented control formulations for generic spacecraft geometries, the proximity and formation flying control capability, and the availability of necessary state information provide significant contributions towards the viability of electrostatic detumble mission concepts.
Advisors/Committee Members: Hanspeter Schaub, Jay McMahon, Jeffrey Parker, Elizabeth Bradley, Zoltan Sternovsky.
Subjects/Keywords: contactless/touchless; electrostatic actuation; formation flying; orbital debris; relative navigation; Aerospace Engineering; Physics
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APA (6th Edition):
Bennett, T. J. (2017). On-Orbit 3-Dimensional Electrostatic Detumble for Generic Spacecraft Geometries. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/226
Chicago Manual of Style (16th Edition):
Bennett, Trevor John. “On-Orbit 3-Dimensional Electrostatic Detumble for Generic Spacecraft Geometries.” 2017. Doctoral Dissertation, University of Colorado. Accessed February 25, 2021.
https://scholar.colorado.edu/asen_gradetds/226.
MLA Handbook (7th Edition):
Bennett, Trevor John. “On-Orbit 3-Dimensional Electrostatic Detumble for Generic Spacecraft Geometries.” 2017. Web. 25 Feb 2021.
Vancouver:
Bennett TJ. On-Orbit 3-Dimensional Electrostatic Detumble for Generic Spacecraft Geometries. [Internet] [Doctoral dissertation]. University of Colorado; 2017. [cited 2021 Feb 25].
Available from: https://scholar.colorado.edu/asen_gradetds/226.
Council of Science Editors:
Bennett TJ. On-Orbit 3-Dimensional Electrostatic Detumble for Generic Spacecraft Geometries. [Doctoral Dissertation]. University of Colorado; 2017. Available from: https://scholar.colorado.edu/asen_gradetds/226
University of Colorado
6.
Barrie, Alexander C.
An Analysis of Scientific Data Quality for the Fast Plasma Investigation of the MMS Mission.
Degree: PhD, 2018, University of Colorado
URL: https://scholar.colorado.edu/asen_gradetds/238
► This work describes technical innovations to improve the data quality and volume for the Fast Plasma Investigation (FPI) on board the Magnetospheric Multiscale mission (MMS).…
(more)
▼ This work describes technical innovations to improve the data quality and volume for the Fast Plasma Investigation (FPI) on board the Magnetospheric Multiscale mission (MMS). A parametric study of wavelet compression has shown that plasma count data can be compressed to high compression ratios with a minimal effect on the integrated plasma moments. Different regions of the magnetosphere are analyzed for both electron and ion count data. The FPI trigger data, intended as a data ranking metric, has been adapted and corrected to a point where scientifically accurate pseudo moments can be generated and released to the research community, drastically increasing the availability of high time resolution data. This is possible due to a scaling system that tunes the dynamic range of the system per region, and the method of using a neural network to correct for exterior contamination effects, such as spacecraft potential. Finally, a map of detection angle bias has been generated that can be used to correct raw count for errors in look direction of incoming particles. This map was generated by statistically sampling particle flight paths through a charged spacecraft environment, validating against flight data. All three of these efforts lead toward the overarching goal of improving data quality and volume for the FPI suite, and future missions to come.
Advisors/Committee Members: Zoltan Sternovsky, Robert Marshall, Xinlin Li, Scot Elkington, Craig Pollock.
Subjects/Keywords: compression; mms; plasma; spacecraft charging; data; Aerospace Engineering; Physics; Remote Sensing
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APA (6th Edition):
Barrie, A. C. (2018). An Analysis of Scientific Data Quality for the Fast Plasma Investigation of the MMS Mission. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/238
Chicago Manual of Style (16th Edition):
Barrie, Alexander C. “An Analysis of Scientific Data Quality for the Fast Plasma Investigation of the MMS Mission.” 2018. Doctoral Dissertation, University of Colorado. Accessed February 25, 2021.
https://scholar.colorado.edu/asen_gradetds/238.
MLA Handbook (7th Edition):
Barrie, Alexander C. “An Analysis of Scientific Data Quality for the Fast Plasma Investigation of the MMS Mission.” 2018. Web. 25 Feb 2021.
Vancouver:
Barrie AC. An Analysis of Scientific Data Quality for the Fast Plasma Investigation of the MMS Mission. [Internet] [Doctoral dissertation]. University of Colorado; 2018. [cited 2021 Feb 25].
Available from: https://scholar.colorado.edu/asen_gradetds/238.
Council of Science Editors:
Barrie AC. An Analysis of Scientific Data Quality for the Fast Plasma Investigation of the MMS Mission. [Doctoral Dissertation]. University of Colorado; 2018. Available from: https://scholar.colorado.edu/asen_gradetds/238
University of Colorado
7.
Hughes, Joseph A.
Dynamics of Complex Spacecraft Subject to Forced and Environmental Charging.
Degree: PhD, 2018, University of Colorado
URL: https://scholar.colorado.edu/asen_gradetds/239
► Due to the space plasma environment and the sun, spacecraft can charge to very high negative voltages. These high charge levels can cause arcing…
(more)
▼ Due to the space plasma environment and the sun, spacecraft can charge to very high negative voltages. These high charge levels can cause arcing which can seriously damage spacecraft electronics and even cause mission ending damage. Spacecraft charging can also cause significant perturbations for lightweight High Area to Mass Ratio (HAMR) objects. If correctly harnessed and directed, charging can be used to exert forces and torques on large debris objects without making physical contact through the Coulomb force. This concept is called the Electrostatic Tractor (ET) and can tug debris out of Geosynchronous Earth orbit (GEO) in a matter of months. To understand both the orbits of uncontrolled charged debris and the performance of the ET, accurate models for how spacecraft charge must be developed, the forces and torques that result from this charging must be estimated, and the effects of these forces and torques must be studied. Spacecraft charging is studied by finding both equilibrium and time-varying solutions for the voltage. A major change with prior work is to use empirical models for the electron and ion flux rather than Maxwellian models. This, coupled with a more realistic Secondary Electron Emission (SEE) model, predicts that it is harder than previously thought for spacecraft to charge negative. The charging equations are also solved for time varying solutions. Electrostatic force and torque prediction is advanced using both analytic and numeric tools. Analytic expressions for the force and torque on a geometrically complex object are presented, which give novel analytical insight. Numeric studies include using the Method of Moments (MoM) to create better-performing Multi-sphere Method (MSM) models. The MSM is also extended to model conductors and dielectrics with good accuracy. The orbital effects of charging are studied for both environmentally charged debris and the ET. For charged debris, it is the electrostatic <i>torque</i> that matters since it can change the attitude and influence Solar Radiation Pressure (SRP). This perturbing force is comparable to an initial attitude uncertainty. For the ET, the new charging model predicts that a few milliAmps of current are needed rather than the few hundred microAmps of current predicted from prior work. Collectively, these studies advance the frontier of knowledge in spacecraft charging, electrostatics, and astrodynamics.
Advisors/Committee Members: Hanspeter Schaub, Jay McMahon, Zoltan Sternovsky, Delores Knipp, Bruce Jakosky.
Subjects/Keywords: electrostatic force and torque; orbital perturbations; spacecraft charging; the orbital effects; electrostatic tractor; Aerospace Engineering; Astrodynamics
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APA ·
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APA (6th Edition):
Hughes, J. A. (2018). Dynamics of Complex Spacecraft Subject to Forced and Environmental Charging. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/239
Chicago Manual of Style (16th Edition):
Hughes, Joseph A. “Dynamics of Complex Spacecraft Subject to Forced and Environmental Charging.” 2018. Doctoral Dissertation, University of Colorado. Accessed February 25, 2021.
https://scholar.colorado.edu/asen_gradetds/239.
MLA Handbook (7th Edition):
Hughes, Joseph A. “Dynamics of Complex Spacecraft Subject to Forced and Environmental Charging.” 2018. Web. 25 Feb 2021.
Vancouver:
Hughes JA. Dynamics of Complex Spacecraft Subject to Forced and Environmental Charging. [Internet] [Doctoral dissertation]. University of Colorado; 2018. [cited 2021 Feb 25].
Available from: https://scholar.colorado.edu/asen_gradetds/239.
Council of Science Editors:
Hughes JA. Dynamics of Complex Spacecraft Subject to Forced and Environmental Charging. [Doctoral Dissertation]. University of Colorado; 2018. Available from: https://scholar.colorado.edu/asen_gradetds/239
University of Colorado
8.
Hartzell, Christine M.
The Dynamics of Near-Surface Dust on Airless Bodies.
Degree: PhD, Aerospace Engineering Sciences, 2012, University of Colorado
URL: https://scholar.colorado.edu/asen_gradetds/48
► The behavior of dust particles under the influence of electrostatic forces has been investigated near the surface of asteroids and the Moon. Dust particle…
(more)
▼ The behavior of dust particles under the influence of electrostatic forces has been investigated near the surface of asteroids and the Moon. Dust particle motion on airless bodies has important implications for our understanding of the evolution of these bodies as well as the design of future exploration vehicles. Electrostatically-dominated dust motion has been hypothesized to cause the observed Lunar Horizon Glow and dust ponds on the asteroid Eros.
The first major contribution of this thesis is the identification of the electric field strength required in order to electrostatically loft dust particles off the surface of the Moon and asteroids Eros and Itokawa, taking into account the gravity of the body (assumed to be spherical) and the cohesion between dust grains (assumed to have the material properties of lunar regolith). In order to solve for the electric field strength required as a function of dust particle size (assumed to be spherical), we assumed that the charge on the dust particle was given by Gauss' law. It can be seen that it is easiest to launch intermediate-sized particles, rather than the submicron-micron sized particles that have been previously considered due to the dominance of cohesion for small particle sizes. Additionally, the electric field strength required to loft particles is orders of magnitude larger than is likely to be present
in situ, unless grain charging is amplified beyond the levels predicted by Gauss' law.
The dynamics of dust particles moving in the plasma sheath, independent of the launching mechanism, is of interest since dust particle levitation could significantly change our understanding of the evolution of asteroids as well as pose a hazard to future exploration vehicles. By studying the levitation behavior in a 1D system for a range of particle sizes, a range of central body masses and three different plasma sheath models, we have gained a more detailed understanding of the drivers of the dynamics of the particles. The equilibria about which dust particles are expected to levitate are identified. The equilibria can be generalized to non-spherical grains (as actual lunar and asteroidal grains are highly angular) by presenting the results as a function of the particle's charge-to-weight ratio. Notably, we see that the behavior of levitating dust is driven by the particle size rather than the mass of the central body. Additionally, we can begin to constrain the range of initial launching conditions that result in levitation.
Finally, we expand our 1D analysis of dust levitation to a 3D system. Due to the rotation of the central body (particularly with fast rotating asteroids), the plasma environment will be changing radically through a particle's trajectory. Additionally, asteroids have highly non-spherical shapes, thus variations in the body's gravity may significantly influence the trajectory of a given particle. For the case of a spherical asteroid, it can be seen that the time variation of the plasma environment will not cause the…
Advisors/Committee Members: Daniel Scheeres, Joshua Colwell, Mihaly Horanyi, Hanspeter Schaub, Zoltan Sternovsky.
Subjects/Keywords: asteroids; cohesion; dust; electrostatic; Moon; Aerospace Engineering; Plasma and Beam Physics
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APA (6th Edition):
Hartzell, C. M. (2012). The Dynamics of Near-Surface Dust on Airless Bodies. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/48
Chicago Manual of Style (16th Edition):
Hartzell, Christine M. “The Dynamics of Near-Surface Dust on Airless Bodies.” 2012. Doctoral Dissertation, University of Colorado. Accessed February 25, 2021.
https://scholar.colorado.edu/asen_gradetds/48.
MLA Handbook (7th Edition):
Hartzell, Christine M. “The Dynamics of Near-Surface Dust on Airless Bodies.” 2012. Web. 25 Feb 2021.
Vancouver:
Hartzell CM. The Dynamics of Near-Surface Dust on Airless Bodies. [Internet] [Doctoral dissertation]. University of Colorado; 2012. [cited 2021 Feb 25].
Available from: https://scholar.colorado.edu/asen_gradetds/48.
Council of Science Editors:
Hartzell CM. The Dynamics of Near-Surface Dust on Airless Bodies. [Doctoral Dissertation]. University of Colorado; 2012. Available from: https://scholar.colorado.edu/asen_gradetds/48
University of Colorado
9.
Xie, Jianfeng.
Trajectory Measurement of Cosmic Dust.
Degree: PhD, Physics, 2012, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/79
► Cosmic dust is abundant in space and, depending on the source, can represent the primordial building blocks of planetary formation. Over the past decades,…
(more)
▼ Cosmic dust is abundant in space and, depending on the source, can represent the primordial building blocks of planetary formation. Over the past decades, dust research has contributed significantly to the understanding of our Solar System and a number of ongoing dynamical and geological processes. The in-situ measurement of dust particle trajectories in space allows the determination of their origin and interaction with space and planetary environments. The Dust Trajectory Sensor (DTS) instrument has been developed for the accurate measurement of the velocity vector and charge of individual cosmic dust particles with sizes down to the submicron range. The DTS works by detecting the induced charges on an array of wire electrodes created from charged dust particles passing by, and reconstructing trajectory from the induced charge signals. This work presents the method of analyzing DTS data and results from a parametric study performed to evaluate the accuracy of the measurements. A laboratory version of the DTS instrument has been constructed and tested with particles in the velocity range of 2-5 km/s using the dust accelerator facility in Heidelberg, Germany. Both the numerical study and the experimental data show that the accuracy of the DTS instrument is better than 1% in speed and 1 degree in trajectory direction. The Electrostatic Lunar Dust Analyzer (ELDA) instrument is a specific application of the DTS concept and designed for the measurement of slow-moving (1-100 m/s) charged dust particles mobilized near the lunar surface. In this case, the mass of each charged dust particle is calculated from the deflection of the trajectory using strong electrostatic fields within the instrument. The full prototype of ELDA has also been constructed and tested in the laboratory. The instrument is tested using particles with a narrow size distribution. The experimental results and the error analyses show that ELDA can measure the mass of individual particles within a factor of two even for very low signal to noise ratios.
Advisors/Committee Members: Mihály Horányi, Zoltan Sternovsky, Sascha Kempf, Tobin Munsat, David Brain.
Subjects/Keywords: Data; Dust; Instrument; Measurement; Trajectory; Aerospace Engineering; Physics
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APA (6th Edition):
Xie, J. (2012). Trajectory Measurement of Cosmic Dust. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/79
Chicago Manual of Style (16th Edition):
Xie, Jianfeng. “Trajectory Measurement of Cosmic Dust.” 2012. Doctoral Dissertation, University of Colorado. Accessed February 25, 2021.
https://scholar.colorado.edu/phys_gradetds/79.
MLA Handbook (7th Edition):
Xie, Jianfeng. “Trajectory Measurement of Cosmic Dust.” 2012. Web. 25 Feb 2021.
Vancouver:
Xie J. Trajectory Measurement of Cosmic Dust. [Internet] [Doctoral dissertation]. University of Colorado; 2012. [cited 2021 Feb 25].
Available from: https://scholar.colorado.edu/phys_gradetds/79.
Council of Science Editors:
Xie J. Trajectory Measurement of Cosmic Dust. [Doctoral Dissertation]. University of Colorado; 2012. Available from: https://scholar.colorado.edu/phys_gradetds/79
University of Colorado
10.
Califf, Sam Tindal.
Investigation of Quasi-Static Electric Fields and Coupled Plasma Populations in the Inner Magnetosphere.
Degree: PhD, Aerospace Engineering Sciences, 2016, University of Colorado
URL: https://scholar.colorado.edu/asen_gradetds/153
► Electric fields are a critical component to understanding the dynamics of plasma in the Earth’s magnetosphere – large-scale electric fields control the shape of the…
(more)
▼ Electric fields are a critical component to understanding the dynamics of plasma in the Earth’s magnetosphere – large-scale electric fields control the shape of the low-energy (~1 eV) plasmasphere, they are responsible for transporting plasma sheet particles (~keV) into the inner magnetosphere, forming much of the trapped energetic particle population, and they affect the high-energy radiation belts (100s keV to MeV) both directly and through coupled interactions with the lower-energy populations. This dissertation focuses on in situ electric field measurements and particle dynamics in the inner magnetosphere with an emphasis on the most inner region below ~4 R
E in the equatorial plane, where extensive particle and fields observations have only recently been available through the Time History of Events and Macroscale Interactions during Substorms (THEMIS) and the Van Allen Probes missions. We address the measurement of electric fields using double-probe instruments onboard spacecraft, including some of the unique challenges for making accurate measurements in the inner magnetosphere. Next, we explore the average structure of the quasi-static electric field in the inner magnetosphere using many years of in situ measurements near the equatorial plane from THEMIS. These results reveal a spatially structured electric field with stronger electric fields in the dusk sector, which we connect to a magnetopshere-iononsphere coupling mechanism through a detailed event study. Finally, we relate electric field measurements deep within the inner magnetosphere to 100s keV electron enhancements in the slot region.
Advisors/Committee Members: Xinlin Li, Robert Ergun, Howard Singer, David Malaspina, Zoltan Sternovsky.
Subjects/Keywords: convection; electric field; magnetosphere; magnetosphere-ionosphere coupling; radiation belts; slot region; Aerospace Engineering; Electromagnetics and Photonics
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APA (6th Edition):
Califf, S. T. (2016). Investigation of Quasi-Static Electric Fields and Coupled Plasma Populations in the Inner Magnetosphere. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/153
Chicago Manual of Style (16th Edition):
Califf, Sam Tindal. “Investigation of Quasi-Static Electric Fields and Coupled Plasma Populations in the Inner Magnetosphere.” 2016. Doctoral Dissertation, University of Colorado. Accessed February 25, 2021.
https://scholar.colorado.edu/asen_gradetds/153.
MLA Handbook (7th Edition):
Califf, Sam Tindal. “Investigation of Quasi-Static Electric Fields and Coupled Plasma Populations in the Inner Magnetosphere.” 2016. Web. 25 Feb 2021.
Vancouver:
Califf ST. Investigation of Quasi-Static Electric Fields and Coupled Plasma Populations in the Inner Magnetosphere. [Internet] [Doctoral dissertation]. University of Colorado; 2016. [cited 2021 Feb 25].
Available from: https://scholar.colorado.edu/asen_gradetds/153.
Council of Science Editors:
Califf ST. Investigation of Quasi-Static Electric Fields and Coupled Plasma Populations in the Inner Magnetosphere. [Doctoral Dissertation]. University of Colorado; 2016. Available from: https://scholar.colorado.edu/asen_gradetds/153
University of Colorado
11.
Cheng, Anqi.
Lattice Studies of SU(3) Gauge System with Many Fermion Flavors.
Degree: PhD, Physics, 2014, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/126
► The discovery of the 125GeV Higgs resonance at the Large Hadron Collider in 2012 completed the electroweak sector of the Standard Model. As exciting…
(more)
▼ The discovery of the 125GeV Higgs resonance at the Large Hadron Collider in 2012 completed the electroweak sector of the Standard Model. As exciting as this discovery is, we still do not understand the underlying mechanism of electroweak symmetry breaking. Strongly interacting gauge-fermion systems are of interests as they can provide missing ultraviolet completion of the Standard Model. At present the most reliable way to investigate these strongly coupled systems is with lattice simulations.
In this dissertation I describe lattice studies of SU(3) gauge theories with many fermion flavors, in search of a viable candidate of composite Higgs models. We discovered a novel phase in the twelve and eight flavor systems which we believe to be a lattice artifact. Later we developed a universal method to extract the mass anomalous dimension from the eigenmode of the massless Dirac operator. Our method is validated on the four flavor QCD-like system, supported by the sixteen flavor infrared conformal system, and predicts the twelve flavor system is infrared conformal with mass anomalous dimension 0.235(27) at the infrared fixed point. A similar investigation of the eight flavor system shows walking behaviors. This method is universal and can be applied to any lattice model of interests.
Advisors/Committee Members: Anna Hasenfratz, Thomas DeGrand, Ethan Neil, Oliver DeWolfe, Zoltan Sternovsky.
Subjects/Keywords: Dirac eigenmode; Lattice; Mass anomalous dimension; SU(3); Elementary Particles and Fields and String Theory
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APA (6th Edition):
Cheng, A. (2014). Lattice Studies of SU(3) Gauge System with Many Fermion Flavors. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/126
Chicago Manual of Style (16th Edition):
Cheng, Anqi. “Lattice Studies of SU(3) Gauge System with Many Fermion Flavors.” 2014. Doctoral Dissertation, University of Colorado. Accessed February 25, 2021.
https://scholar.colorado.edu/phys_gradetds/126.
MLA Handbook (7th Edition):
Cheng, Anqi. “Lattice Studies of SU(3) Gauge System with Many Fermion Flavors.” 2014. Web. 25 Feb 2021.
Vancouver:
Cheng A. Lattice Studies of SU(3) Gauge System with Many Fermion Flavors. [Internet] [Doctoral dissertation]. University of Colorado; 2014. [cited 2021 Feb 25].
Available from: https://scholar.colorado.edu/phys_gradetds/126.
Council of Science Editors:
Cheng A. Lattice Studies of SU(3) Gauge System with Many Fermion Flavors. [Doctoral Dissertation]. University of Colorado; 2014. Available from: https://scholar.colorado.edu/phys_gradetds/126
University of Colorado
12.
Stiles, Laura Ann.
Electrostatic In ation of Membrane Space Structures.
Degree: PhD, Aerospace Engineering Sciences, 2013, University of Colorado
URL: https://scholar.colorado.edu/asen_gradetds/92
► Membrane space structures provide a lightweight and cost effective alternative to traditional mechanical systems. The low-mass and high deployed-to-stored volume ratios allow for larger…
(more)
▼ Membrane space structures provide a lightweight and cost effective alternative to traditional mechanical systems. The low-mass and high deployed-to-stored volume ratios allow for larger structures to be launched, expanding on-orbit science and technology capabilities. This research explores a novel method for deployment of membrane space structures using electrostatic pressure as the inflation mechanism. Applying electric charge to a layered gossamer structure provides an inflationary pressure due to the repulsive electrostatic forces between the charged layers. The electrostatic inflation of membrane structures (EIMS) concept is particularly applicable to non-precision structures such as sunshields or drag de-orbiting devices. This research addresses three fundamental topics: necessary conditions for EIMS in a vacuum, necessary conditions for EIMS in a plasma, and charging methods. Vacuum demonstrations show that less than 10 kiloVolts are required for electrostatic inflation of membrane structures in 1-g. On-orbit perturbation forces can be much smaller, suggesting feasible voltage requirements. Numerical simulation enables a relationship between required inflation pressure (to offset disturbances) and voltage. 100's of Volts are required for inflation in geosynchronous orbits (GEO) and a few kiloVolts in low Earth orbit (LEO). While GEO plasma has a small impact on the EIMS performance, Debye shielding at LEO reduces the electrostatic pressure. The classic Debye shielding prediction is far worse than actual shielding, raising the `effective' Debye length to the meter scale in LEO, suggesting feasibility for EIMS in LEO. Charged particle emission and remote charging methods are explored as inflation mechanisms. Secondary electron emission characteristics of EIMS materials were determined experimentally. Nonlinear fits to the Sternglass curve determined a maximum yield of 1.83 at 433 eV for Aluminized Kapton and a maximum yield of 1.78 at 511 eV for Aluminized Mylar. Remote charging was demonstrated to -500 V with a 5 keV electron beam. Charge emission power levels are below 1 Watt in GEO and from 10's of Watt to a kiloWatt in LEO.
Advisors/Committee Members: Hanspeter Schaub, Zoltan Sternovsky, Kurt Maute, Dejan Filipovic, Daniel Moorer.
Subjects/Keywords: Deployable Spacecraft; Inflatable Structures; Plasma Physics; Spacecraft Charging; Aerospace Engineering
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APA ·
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APA (6th Edition):
Stiles, L. A. (2013). Electrostatic In ation of Membrane Space Structures. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/92
Chicago Manual of Style (16th Edition):
Stiles, Laura Ann. “Electrostatic In ation of Membrane Space Structures.” 2013. Doctoral Dissertation, University of Colorado. Accessed February 25, 2021.
https://scholar.colorado.edu/asen_gradetds/92.
MLA Handbook (7th Edition):
Stiles, Laura Ann. “Electrostatic In ation of Membrane Space Structures.” 2013. Web. 25 Feb 2021.
Vancouver:
Stiles LA. Electrostatic In ation of Membrane Space Structures. [Internet] [Doctoral dissertation]. University of Colorado; 2013. [cited 2021 Feb 25].
Available from: https://scholar.colorado.edu/asen_gradetds/92.
Council of Science Editors:
Stiles LA. Electrostatic In ation of Membrane Space Structures. [Doctoral Dissertation]. University of Colorado; 2013. Available from: https://scholar.colorado.edu/asen_gradetds/92
University of Colorado
13.
Stevenson, Daan.
Remote Spacecraft Attitude Control by Coulomb Charging.
Degree: PhD, Aerospace Engineering Sciences, 2015, University of Colorado
URL: https://scholar.colorado.edu/asen_gradetds/94
► The possibility of inter-spacecraft collisions is a serious concern at Geosynchronous altitudes, where many high-value assets operate in proximity to countless debris objects whose…
(more)
▼ The possibility of inter-spacecraft collisions is a serious concern at Geosynchronous altitudes, where many high-value assets operate in proximity to countless debris objects whose orbits experience no natural means of decay. The ability to rendezvous with these derelict satellites would enable active debris removal by servicing or repositioning missions, but docking procedures are generally inhibited by the large rotational momenta of uncontrolled satellites. Therefore, a contactless means of reducing the rotation rate of objects in the space environment is desired. This dissertation investigates the viability of Coulomb charging to achieve such remote spacecraft attitude control. If a servicing craft imposes absolute electric potentials on a nearby nonspherical debris object, it will impart electrostatic torques that can be used to gradually arrest the object's rotation.
In order to simulate the relative motion of charged spacecraft with complex geometries, accurate but rapid knowledge of the Coulomb interactions is required. To this end, a new electrostatic force model called the Multi-Sphere Method (MSM) is developed. All aspects of the Coulomb de-spin concept are extensively analyzed and simulated using a system with simplified geometries and one dimensional rotation. First, appropriate control algorithms are developed to ensure that the nonlinear Coulomb torques arrest the rotation with guaranteed stability. Moreover, the complex interaction of the spacecraft with the plasma environment and charge control beams is modeled to determine what hardware requirements are necessary to achieve the desired electric potential levels. Lastly, the attitude dynamics and feedback control development is validated experimentally using a scaled down terrestrial testbed. High voltage power supplies control the potential on two nearby conductors, a stationary sphere and a freely rotating cylinder. The nonlinear feedback control algorithms developed above are implemented to achieve rotation rate and absolute attitude control. Collectively, these studies decisively validate the feasibility of Coulomb charging for remote spacecraft attitude control.
Advisors/Committee Members: Hanspeter Schaub, Webster Cash, Brandon Jones, Daniel Moorer, Zoltan Sternovsky.
Subjects/Keywords: electrostatic modeling; high voltage experimentation; spacecraft attitude control; spacecraft charging; Multi-Vehicle Systems and Air Traffic Control; Navigation, Guidance, Control and Dynamics; Space Vehicles
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APA (6th Edition):
Stevenson, D. (2015). Remote Spacecraft Attitude Control by Coulomb Charging. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/94
Chicago Manual of Style (16th Edition):
Stevenson, Daan. “Remote Spacecraft Attitude Control by Coulomb Charging.” 2015. Doctoral Dissertation, University of Colorado. Accessed February 25, 2021.
https://scholar.colorado.edu/asen_gradetds/94.
MLA Handbook (7th Edition):
Stevenson, Daan. “Remote Spacecraft Attitude Control by Coulomb Charging.” 2015. Web. 25 Feb 2021.
Vancouver:
Stevenson D. Remote Spacecraft Attitude Control by Coulomb Charging. [Internet] [Doctoral dissertation]. University of Colorado; 2015. [cited 2021 Feb 25].
Available from: https://scholar.colorado.edu/asen_gradetds/94.
Council of Science Editors:
Stevenson D. Remote Spacecraft Attitude Control by Coulomb Charging. [Doctoral Dissertation]. University of Colorado; 2015. Available from: https://scholar.colorado.edu/asen_gradetds/94
University of Colorado
14.
Shu, Anthony John.
Microcratering in Polyvinylidene Fluoride.
Degree: PhD, Physics, 2015, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/138
► Dust is defined as macroparticles as small as a few molecules up to several micrometers in diameter. In the context of space exploration, it…
(more)
▼ Dust is defined as macroparticles as small as a few molecules up to several micrometers in diameter. In the context of space exploration, it was originally seen only as a technical obstacle to applications; dust can damage instrument surfaces, coat mating surfaces preventing proper seals, and impair or obstruct measurements. Because of the ubiquity of dust in the solar system and its role in the origin of planets and other bodies, the study of dust and related phenomena has evolved to a scientific subdiscipline which can provide us insight into the origins and evolution of our solar system.
In order to facilitate this, a hypervelocity dust accelerator has been built at the
University of
Colorado at Boulder and is being used to probe impact phenomena, dust mitigation techniques, dust detection techniques, and more. One such dust detector is a Polyvinylidene Fluoride (PVDF) dust detector. The PVDF dust detector is very lightweight and consumes little power. Due to these properties, PVDF detectors can potentially be used on any spacecraft to gain information on the local dust environment. It is not fully understood how this PVDF dust detector signal is generated, so at present can only be used as a dust counter.
In this thesis I discuss the importance of the study of dust phenomena, describe the accelerator experiment, and describe a study conducted to determine the underlying physical principles of PVDF dust detectors. This included measuring crater size scaling laws, measuring the detailed shape of craters, and applying this data to simulations of the signals being generated by PVDF detectors.
Advisors/Committee Members: Tobin Munsat, Mihaly Horanyi, Sascha Kempf, Zoltan Sternovsky, Robert Ergun.
Subjects/Keywords: cosmic dust; cratering; hypervelocity; impact; PVDF; Physics; Polymer and Organic Materials
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APA (6th Edition):
Shu, A. J. (2015). Microcratering in Polyvinylidene Fluoride. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/138
Chicago Manual of Style (16th Edition):
Shu, Anthony John. “Microcratering in Polyvinylidene Fluoride.” 2015. Doctoral Dissertation, University of Colorado. Accessed February 25, 2021.
https://scholar.colorado.edu/phys_gradetds/138.
MLA Handbook (7th Edition):
Shu, Anthony John. “Microcratering in Polyvinylidene Fluoride.” 2015. Web. 25 Feb 2021.
Vancouver:
Shu AJ. Microcratering in Polyvinylidene Fluoride. [Internet] [Doctoral dissertation]. University of Colorado; 2015. [cited 2021 Feb 25].
Available from: https://scholar.colorado.edu/phys_gradetds/138.
Council of Science Editors:
Shu AJ. Microcratering in Polyvinylidene Fluoride. [Doctoral Dissertation]. University of Colorado; 2015. Available from: https://scholar.colorado.edu/phys_gradetds/138
University of Colorado
15.
Zhao, Hong.
Unveiled Characteristics of Energetic Electrons and Ions: the Inner Radiation Belt, Slot Region, and Ring Current.
Degree: PhD, Aerospace Engineering Sciences, 2015, University of Colorado
URL: https://scholar.colorado.edu/asen_gradetds/117
► Earth’s inner magnetosphere is a highly dynamic region consisting of various charged particle populations and current systems. Composed of relativistic electrons and protons, the…
(more)
▼ Earth’s inner magnetosphere is a highly dynamic region consisting of various charged particle populations and current systems. Composed of relativistic electrons and protons, the radiation belt is a hazardous environment for both spacecraft and humans in space; while the variations of ring current, an electric current flowing around Earth consisting of energetic ions and electrons, can cause severe disruption of electrical systems on the ground. In the following, we focus on the dynamics of relativistic electrons (>~100 keV) in the inner radiation belt and slot region and energetic ions and electrons (>~keV) in the ring current, which are subject to influence from many different physical processes and commonly exhibit great changes on various spatial and temporal scales. Using data from SAMPEX and DEMETER satellites, we find that in the inner belt and slot region, though MeV electrons only exhibit flux enhancements during severe solar wind conditions, 100s of keV electron flux variations occur much more often. Using a radial diffusion model, a penetration event of 100s of keV electrons into the inner belt and slot region is modeled, and the results indicate that the penetration can be well explained by inward radial transport, but the radial diffusion coefficient is different from those of previous studies. Also, using data from the Van Allen Probes, we perform detailed analysis of 100s of keV electron pitch angle distributions (PADs) in the inner belt and slot region. A new type of PADs with minima at 90° persistent near the magnetic equator is unveiled, which is contradictory to the theoretical predictions from known physical processes and shows the complexity in the inner belt dynamics. Finally, the evolution of ring current ions and electrons are investigated during geomagnetic storms using data from the Van Allen Probes. The contribution of electrons and ions to the ring current energy is calculated and intriguing results are found. Our studies on the energetic electrons and ions in the inner belt, slot region and ring current contribute to a more comprehensive picture of inner magnetosphere dynamics.
Advisors/Committee Members: Xinlin Li, Dan Baker, Howard Singer, Scot Elkington, Zoltan Sternovsky.
Subjects/Keywords: Deep Penetration; Energetic Particles; Wave-particle Interaction; Aerospace Engineering; Geophysics and Seismology; Plasma and Beam Physics
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APA ·
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Export
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APA (6th Edition):
Zhao, H. (2015). Unveiled Characteristics of Energetic Electrons and Ions: the Inner Radiation Belt, Slot Region, and Ring Current. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/117
Chicago Manual of Style (16th Edition):
Zhao, Hong. “Unveiled Characteristics of Energetic Electrons and Ions: the Inner Radiation Belt, Slot Region, and Ring Current.” 2015. Doctoral Dissertation, University of Colorado. Accessed February 25, 2021.
https://scholar.colorado.edu/asen_gradetds/117.
MLA Handbook (7th Edition):
Zhao, Hong. “Unveiled Characteristics of Energetic Electrons and Ions: the Inner Radiation Belt, Slot Region, and Ring Current.” 2015. Web. 25 Feb 2021.
Vancouver:
Zhao H. Unveiled Characteristics of Energetic Electrons and Ions: the Inner Radiation Belt, Slot Region, and Ring Current. [Internet] [Doctoral dissertation]. University of Colorado; 2015. [cited 2021 Feb 25].
Available from: https://scholar.colorado.edu/asen_gradetds/117.
Council of Science Editors:
Zhao H. Unveiled Characteristics of Energetic Electrons and Ions: the Inner Radiation Belt, Slot Region, and Ring Current. [Doctoral Dissertation]. University of Colorado; 2015. Available from: https://scholar.colorado.edu/asen_gradetds/117
University of Colorado
16.
Szalay, Jamey Robert.
The Lunar Dust Environment.
Degree: PhD, Physics, 2015, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/151
► Planetary bodies throughout the solar system are continually bombarded by dust particles, largely originating from cometary activities and asteroidal collisions. Surfaces of bodies with…
(more)
▼ Planetary bodies throughout the solar system are continually bombarded by dust particles, largely originating from cometary activities and asteroidal collisions. Surfaces of bodies with thick atmospheres, such as Venus, Earth, Mars and Titan are mostly protected from incoming dust impacts as these particles ablate in their atmospheres as `shooting stars'. However, the majority of bodies in the solar system have no appreciable atmosphere and their surfaces are directly exposed to the flux of high speed dust grains. Impacts onto solid surfaces in space generate charged and neutral gas clouds, as well as solid secondary ejecta dust particles. Gravitationally bound ejecta clouds forming dust exospheres were recognized by in situ dust instruments around the icy moons of Jupiter and Saturn, and had not yet been observed near bodies with refractory regolith surfaces before NASA's Lunar Dust and Environment Explorer (LADEE) mission.
In this thesis, we first present the measurements taken by the Lunar Dust Explorer (LDEX), aboard LADEE, which discovered a permanently present, asymmetric dust cloud surrounding the Moon. The global characteristics of the lunar dust cloud are discussed as a function of a variety of variables such as altitude, solar longitude, local time, and lunar phase. These results are compared with models for lunar dust cloud generation. Second, we present an analysis of the groupings of impacts measured by LDEX, which represent detections of dense ejecta plumes above the lunar surface. These measurements are put in the context of understanding the response of the lunar surface to meteoroid bombardment and how to use other airless bodies in the solar system as detectors for their local meteoroid environment. Third, we present the first in-situ dust measurements taken over the lunar sunrise terminator. Having found no excess of small grains in this region, we discuss its implications for the putative population of electrostatically lofted dust.
Advisors/Committee Members: Mihaly Horanyi, Sascha Kempf, Fran Bagenal, Zoltan Sternovsky, Hsiang-Wen Hsu.
Subjects/Keywords: meteor showers; plume; electrostatic lofting; Astrophysics and Astronomy; Physical Processes; Physics
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APA ·
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MLA ·
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APA (6th Edition):
Szalay, J. R. (2015). The Lunar Dust Environment. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/151
Chicago Manual of Style (16th Edition):
Szalay, Jamey Robert. “The Lunar Dust Environment.” 2015. Doctoral Dissertation, University of Colorado. Accessed February 25, 2021.
https://scholar.colorado.edu/phys_gradetds/151.
MLA Handbook (7th Edition):
Szalay, Jamey Robert. “The Lunar Dust Environment.” 2015. Web. 25 Feb 2021.
Vancouver:
Szalay JR. The Lunar Dust Environment. [Internet] [Doctoral dissertation]. University of Colorado; 2015. [cited 2021 Feb 25].
Available from: https://scholar.colorado.edu/phys_gradetds/151.
Council of Science Editors:
Szalay JR. The Lunar Dust Environment. [Doctoral Dissertation]. University of Colorado; 2015. Available from: https://scholar.colorado.edu/phys_gradetds/151
. 
Open Access Theses and Dissertations