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University of Colorado
1.
Inampudi, Ravi Kishore.
Two-Craft Coulomb Formation Study about Circular Orbits and Libration Points.
Degree: PhD, Aerospace Engineering Sciences, 2010, University of Colorado
URL: https://scholar.colorado.edu/asen_gradetds/12 
► This dissertation investigates the dynamics and control of a two-craft Coulomb formation in circular orbits and at libration points; it addresses relative equilibria, stability…
(more)
▼ This dissertation investigates the dynamics and control of a two-craft Coulomb formation in circular orbits and at libration points; it addresses relative equilibria, stability and optimal reconfigurations of such formations. The relative equilibria of a two-craft tether formation connected by line-of-sight elastic forces moving in circular orbits and at libration points are investigated. In circular Earth orbits and Earth-Moon libration points, the radial, along-track, and orbit normal great circle equilibria conditions are found. An example of modeling the tether force using Coulomb force is discussed. Furthermore, the non-great-circle equilibria conditions for a two-spacecraft tether structure in circular Earth orbit and at collinear libration points are developed. Then the linearized dynamics and stability analysis of a 2-craft Coulomb formation at Earth- Moon libration points are studied. For orbit-radial equilibrium, Coulomb forces control the relative distance between the two satellites. The gravity gradient torques on the formation due to the two planets help stabilize the formation. Similar analysis is performed for alongtrack and orbit-normal relative equilibrium configurations. Where necessary, the craft use a hybrid thrusting-electrostatic actuation system. The two-craft dynamics at the libration points provide a general framework with circular Earth orbit dynamics forming a special case. In the presence of differential solar drag perturbations, a Lyapunov feedback controller is designed to stabilize a radial equilibrium, two-craft Coulomb formation at collinear libration points. The second part of the thesis investigates optimal reconfigurations of two-craft Coulomb formations in circular Earth orbits by applying nonlinear optimal control techniques. The objective of these reconfigurations is to maneuver the two-craft formation between two charged equilibria configurations. The reconfiguration of spacecraft is posed as an optimization problem using the calculus of variations approach. The optimality criteria are minimum time, minimum acceleration of the separation distance, minimum Coulomb and electric propulsion fuel usage, and minimum electrical power consumption. The continuous time problem is discretized using a pseudospectral method, and the resulting finite dimensional problem is solved using a sequential quadratic programming algorithm. The software package, DIDO, implements this approach. This second part illustrates how pseudospectral methods significantly simplify the solution-finding process.
Advisors/Committee Members: Hanspeter Schaub, Penina Axelrad, George Born.
Subjects/Keywords: Circular Orbits and Libration Points; Dynamics and Optimal Control; Formation Flying; Optimal Reconfigurations; Relative Equilibria and Stability; Two-Craft Coulomb Tether; Aerospace Engineering
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APA (6th Edition):
Inampudi, R. K. (2010). Two-Craft Coulomb Formation Study about Circular Orbits and Libration Points. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/12
Chicago Manual of Style (16th Edition):
Inampudi, Ravi Kishore. “Two-Craft Coulomb Formation Study about Circular Orbits and Libration Points.” 2010. Doctoral Dissertation, University of Colorado. Accessed March 07, 2021.
https://scholar.colorado.edu/asen_gradetds/12.
MLA Handbook (7th Edition):
Inampudi, Ravi Kishore. “Two-Craft Coulomb Formation Study about Circular Orbits and Libration Points.” 2010. Web. 07 Mar 2021.
Vancouver:
Inampudi RK. Two-Craft Coulomb Formation Study about Circular Orbits and Libration Points. [Internet] [Doctoral dissertation]. University of Colorado; 2010. [cited 2021 Mar 07].
Available from: https://scholar.colorado.edu/asen_gradetds/12.
Council of Science Editors:
Inampudi RK. Two-Craft Coulomb Formation Study about Circular Orbits and Libration Points. [Doctoral Dissertation]. University of Colorado; 2010. Available from: https://scholar.colorado.edu/asen_gradetds/12
University of Colorado
2.
Blenden, Robin M.
Regenerative Power Optimal Reaction Wheel Attitude Control.
Degree: MS, Aerospace Engineering Sciences, 2011, University of Colorado
URL: https://scholar.colorado.edu/asen_gradetds/21
► The thesis work develops an instantaneous power optimal attitude control for a spacecraft utilizing an integrated reaction wheel - flywheel system allowing for energy…
(more)
▼ The thesis work develops an instantaneous power optimal attitude control for a spacecraft utilizing an integrated reaction wheel - flywheel system allowing for energy storage and return. The control is generally formulated to utilize an arbitrarily large number of reaction wheels, and is applicable to any system with redundant wheels spanning three-dimensional space. This is accomplished by manipulation of the wheel torque null motion such that the resulting attitude dynamics are not affected. By application of physical constraints on the wheel motor performance, the solution method to find the null torques is reduced to a hyperdimensional vector geometry problem, and the proper control torques are uniquely determined. The resulting power optimal control guarantees that the instantaneous maximum power is returned from the reaction wheels at all times. This control is then applied to a variety of control laws, demonstrating its behavior for a variety of control applications and initial spacecraft states. These include a velocity regulator control and attitude a velocity tracking control. Comparison to other relevant reaction wheel controls demonstrates the analytically developed instantaneous power optimal and minimum energy state seeking behavior. Finally, future developments are suggested, including the incorporation of wheel power return inefficiency and application of the developed methodology for integrated energy storage and power tracking.
Advisors/Committee Members: Hanspeter Schaub, Penina Axelrad, Eric Frew.
Subjects/Keywords: Attitude Control; Power Optimal; Reaction Wheel; Aerospace Engineering; Space Vehicles
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APA (6th Edition):
Blenden, R. M. (2011). Regenerative Power Optimal Reaction Wheel Attitude Control. (Masters Thesis). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/21
Chicago Manual of Style (16th Edition):
Blenden, Robin M. “Regenerative Power Optimal Reaction Wheel Attitude Control.” 2011. Masters Thesis, University of Colorado. Accessed March 07, 2021.
https://scholar.colorado.edu/asen_gradetds/21.
MLA Handbook (7th Edition):
Blenden, Robin M. “Regenerative Power Optimal Reaction Wheel Attitude Control.” 2011. Web. 07 Mar 2021.
Vancouver:
Blenden RM. Regenerative Power Optimal Reaction Wheel Attitude Control. [Internet] [Masters thesis]. University of Colorado; 2011. [cited 2021 Mar 07].
Available from: https://scholar.colorado.edu/asen_gradetds/21.
Council of Science Editors:
Blenden RM. Regenerative Power Optimal Reaction Wheel Attitude Control. [Masters Thesis]. University of Colorado; 2011. Available from: https://scholar.colorado.edu/asen_gradetds/21
University of Colorado
3.
Saunders, Marc.
Adaptive Formation Flying Maneuvers for Multiple Relative Orbits.
Degree: MS, Aerospace Engineering Sciences, 2011, University of Colorado
URL: https://scholar.colorado.edu/asen_gradetds/23
► In order to extend and preserve the mission of an earth orbiting satellite it is imperative that the on board maneuvers do not waste…
(more)
▼ In order to extend and preserve the mission of an earth orbiting satellite it is imperative that the on board maneuvers do not waste propulsion but maneuver the spacecraft optimally. The challenge for ground stations is to plan maneuvers for spacecraft that will achieve a desired orbit while minimizing fuel costs. Increasing this challenge is the addition of specific keep-out zones (constraints on the spacecraft). For example, a low-earth orbiter (LEO) may need to maintain a specific orbit plane for a sun-synchronous imaging mission but it now has to contend with opposing debris. Computing a maneuver to avoid the debris could have consequences to the mission constraints and cause undesired affects to the desired orbit. The purpose of this research is to develop some techniques that can aid in finding some optimal maneuvers (or maneuvers that use the least amount of energy) and will maintain mission requirements while preserving constraints.
Two different models will be developed that can minimize energy used in the maneuvers. The first model is a linear set of impulsive maneuvers derived from the
Clohessy-Wilshire Equations. This model can be used as a targeting equation for targeting a specific relative orbit that also minimizes the total energy among a series of maneuvers. The second method is a nonlinear model using a
Lyapunov Function in a feedback control loop; where the position of a spacecraft relative to a target orbit is minimized and the reference motion can be used to create keep-out zones.
Advisors/Committee Members: Hanspeter Schaub, George Born, Penina Axelrad.
Subjects/Keywords: formation flying; multiple vehicle management; nonlinear control; optimal feedback control; relative orbits; Aerospace Engineering
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APA (6th Edition):
Saunders, M. (2011). Adaptive Formation Flying Maneuvers for Multiple Relative Orbits. (Masters Thesis). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/23
Chicago Manual of Style (16th Edition):
Saunders, Marc. “Adaptive Formation Flying Maneuvers for Multiple Relative Orbits.” 2011. Masters Thesis, University of Colorado. Accessed March 07, 2021.
https://scholar.colorado.edu/asen_gradetds/23.
MLA Handbook (7th Edition):
Saunders, Marc. “Adaptive Formation Flying Maneuvers for Multiple Relative Orbits.” 2011. Web. 07 Mar 2021.
Vancouver:
Saunders M. Adaptive Formation Flying Maneuvers for Multiple Relative Orbits. [Internet] [Masters thesis]. University of Colorado; 2011. [cited 2021 Mar 07].
Available from: https://scholar.colorado.edu/asen_gradetds/23.
Council of Science Editors:
Saunders M. Adaptive Formation Flying Maneuvers for Multiple Relative Orbits. [Masters Thesis]. University of Colorado; 2011. Available from: https://scholar.colorado.edu/asen_gradetds/23
University of Colorado
4.
Krening, Samantha C.
Visual Spacecraft Relative Motion Control using Higher Order Geometric Moments.
Degree: MS, Aerospace Engineering Sciences, 2011, University of Colorado
URL: https://scholar.colorado.edu/asen_gradetds/24
► This thesis studies passive visual relative control for satellites. The three main problems studied are how to keep the camera pointing at the center…
(more)
▼ This thesis studies passive visual relative control for satellites. The three main problems studied are how to keep the camera pointing at the center of the target, how to move the satellite so the camera can look at the target from a perpendicular orientation or maintain a fixed orientation, and how to maintain a nominal distance from the target. Visual target tracking within the image uses a statistical pressure snake algorithm, which tracks the outer contour of a target and allows geometric moments to be calculated. The attitude control is based off of tracking the center of the visual target, which is the first moment. The attitude control can treat the inertial target angular velocities as disturbances in the control for slow, smooth reference motions and still be stable. The skewness coefficient g3, which is a non-dimensional form of the third moment, can be used as a measure of perpendicularity when certain information is known about the target. A 640x480 pixel resolution camera is used to obtain better skewness and perpendicularity information than the human eye. A distance control does not need to assume the absolute distance, but can maintain a nominal distance by using the image inertia, or second moment information.
Advisors/Committee Members: Hanspeter Schaub, Jeffrey Luftig, Penina Axelrad.
Subjects/Keywords: Attitude control; Geometric moments; Monocular computer vision; Passive visual relative control; Skewness; Statistical pressure snake; Aerospace Engineering
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APA (6th Edition):
Krening, S. C. (2011). Visual Spacecraft Relative Motion Control using Higher Order Geometric Moments. (Masters Thesis). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/24
Chicago Manual of Style (16th Edition):
Krening, Samantha C. “Visual Spacecraft Relative Motion Control using Higher Order Geometric Moments.” 2011. Masters Thesis, University of Colorado. Accessed March 07, 2021.
https://scholar.colorado.edu/asen_gradetds/24.
MLA Handbook (7th Edition):
Krening, Samantha C. “Visual Spacecraft Relative Motion Control using Higher Order Geometric Moments.” 2011. Web. 07 Mar 2021.
Vancouver:
Krening SC. Visual Spacecraft Relative Motion Control using Higher Order Geometric Moments. [Internet] [Masters thesis]. University of Colorado; 2011. [cited 2021 Mar 07].
Available from: https://scholar.colorado.edu/asen_gradetds/24.
Council of Science Editors:
Krening SC. Visual Spacecraft Relative Motion Control using Higher Order Geometric Moments. [Masters Thesis]. University of Colorado; 2011. Available from: https://scholar.colorado.edu/asen_gradetds/24
University of Colorado
5.
Tombasco, Jill.
Orbit Estimation of Geosynchronous Objects Via Ground-Based and Space-Based Optical Tracking.
Degree: PhD, Aerospace Engineering Sciences, 2011, University of Colorado
URL: https://scholar.colorado.edu/asen_gradetds/31
► Angles-only orbit estimation of geosynchronous objects is a unique challenge due to the dense population of clustered geosynchronous objects, the singularities of and perturbations…
(more)
▼ Angles-only orbit estimation of geosynchronous objects is a unique challenge due to the dense population of clustered geosynchronous objects, the singularities of and perturbations to geosynchronous motion, and the error inherent to experimental observations of geosynchronous objects. Passive optical tracking of geosynchronous space objects has traditionally been performed by ground-based sensors, and the capability has advanced significantly through the introduction of space-based angles-only tracking. This research addresses three key facets of geosynchronous orbit estimation accuracy: improvement to the accuracy via appropriate coordinate modeling, empirical characterization of achievable ground-based angles-only estimation accuracy, and analytic modeling of the space-based angles-only estimated uncertainty. This research develops and analyzes improvements to geosynchronous orbit estimation based on high-fidelity dynamic modeling with a specialized set of coordinates designed specifically to address the geosynchronous orbit conditions. The use of an appropriate representation, the GEO elements, enhances the orbit estimation accuracy compared to the more traditional inertial Cartesian state space representation of geosynchronous motion. Simulation and experimental studies demonstrate that GEO element estimation better recovers the in-track motion than inertial position and velocity state estimation. The short-term estimation accuracy given ground-based tracking is characterized empirically using the Wide Area Augmentation System satellite reference ephemerides. The results show that 10 meter accuracy is possible given short sampling intervals (10 to 30 seconds) and long nightly track lengths (3 or more hours). Several tracking scenarios are found to meet accuracy requirements on the order of 100 meters. The observability of relative states using space-based angles-only tracking of geosynchronous objects by a geosynchronous sensor is analyzed, and first-order analytic expressions for the predicted uncertainty of the along-track separation and intersatellite range are developed assuming space-based passive tracking. The uncertainty models are validated via Monte Carlo analysis. The results demonstrate that 1 hour of continuous space-based passive tracking can estimate the range to the order of tens of meters, and 12 hours produces range uncertainty on the order of meters. The outcome of this research is a set of methods to improve the performance of geosynchronous orbit estimation, and an enhanced understanding of the accuracy possibilities of angles-only ground-based and space-based geosynchronous orbit estimation.
Advisors/Committee Members: Penina Axelrad, George Born, Hanspeter Schaub.
Subjects/Keywords: angles-only; geosynchronous; orbit dynamics; orbit estimation; space-based optical tracking; Aerospace Engineering
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APA (6th Edition):
Tombasco, J. (2011). Orbit Estimation of Geosynchronous Objects Via Ground-Based and Space-Based Optical Tracking. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/31
Chicago Manual of Style (16th Edition):
Tombasco, Jill. “Orbit Estimation of Geosynchronous Objects Via Ground-Based and Space-Based Optical Tracking.” 2011. Doctoral Dissertation, University of Colorado. Accessed March 07, 2021.
https://scholar.colorado.edu/asen_gradetds/31.
MLA Handbook (7th Edition):
Tombasco, Jill. “Orbit Estimation of Geosynchronous Objects Via Ground-Based and Space-Based Optical Tracking.” 2011. Web. 07 Mar 2021.
Vancouver:
Tombasco J. Orbit Estimation of Geosynchronous Objects Via Ground-Based and Space-Based Optical Tracking. [Internet] [Doctoral dissertation]. University of Colorado; 2011. [cited 2021 Mar 07].
Available from: https://scholar.colorado.edu/asen_gradetds/31.
Council of Science Editors:
Tombasco J. Orbit Estimation of Geosynchronous Objects Via Ground-Based and Space-Based Optical Tracking. [Doctoral Dissertation]. University of Colorado; 2011. Available from: https://scholar.colorado.edu/asen_gradetds/31
University of Colorado
6.
Seubert, Carl.
One-Dimensional Spacecraft Formation Flight Testbed for Terrestrial Charged Relative Motion Experiments.
Degree: PhD, Aerospace Engineering Sciences, 2011, University of Colorado
URL: https://scholar.colorado.edu/asen_gradetds/38
► Spacecraft operating in a desired formation offers an abundance of attractive mission capabilities. One proposed method of controlling a close formation of spacecraft is…
(more)
▼ Spacecraft operating in a desired formation offers an abundance of attractive mission capabilities. One proposed method of controlling a close formation of spacecraft is with Coulomb (electrostatic) forces. The Coulomb formation flight idea utilizes charge emission to drive the spacecraft to kilovolt-level potentials and generate adjustable, micronewton- to millinewton-level Coulomb forces for relative position control. In order to advance the prospects of the Coulomb formation flight concept, this dissertation presents the design and implementation of a unique one-dimensional testbed. The disturbances of the testbed are identified and reduced below 1 mN. This noise level offers a near-frictionless platform that is used to perform relative motion actuation with electrostatics in a terrestrial atmospheric environment. Potentials up to 30 kV are used to actuate a cart over a translational range of motion of 40 cm. A challenge to both theoretical and hardware implemented electrostatic actuation developments is correctly modeling the forces between finite charged bodies, outside a vacuum. To remedy this, studies of Earth orbit plasmas and Coulomb force theory is used to derive and propose a model of the Coulomb force between finite spheres in close proximity, in a plasma. This plasma force model is then used as a basis for a candidate terrestrial force model. The plasma-like parameters of this terrestrial model are estimated using charged motion data from fixed-potential, single-direction experiments on the testbed. The testbed is advanced to the level of autonomous feedback position control using solely Coulomb force actuation. This allows relative motion repositioning on a flat and level track as well as an inclined track that mimics the dynamics of two charged spacecraft that are aligned with the principal orbit axis. This controlled motion is accurately predicted with simulations using the terrestrial force model. This demonstrates similarities between the partial charge shielding of space-based plasmas to the electrostatic screening in the laboratory atmosphere.
Advisors/Committee Members: Hanspeter Schaub, Penina Axelrad, Daniel Moorer.
Subjects/Keywords: Coulomb; formation; modeling; plasma; spacecraft; testbed; Aerospace Engineering
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APA (6th Edition):
Seubert, C. (2011). One-Dimensional Spacecraft Formation Flight Testbed for Terrestrial Charged Relative Motion Experiments. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/38
Chicago Manual of Style (16th Edition):
Seubert, Carl. “One-Dimensional Spacecraft Formation Flight Testbed for Terrestrial Charged Relative Motion Experiments.” 2011. Doctoral Dissertation, University of Colorado. Accessed March 07, 2021.
https://scholar.colorado.edu/asen_gradetds/38.
MLA Handbook (7th Edition):
Seubert, Carl. “One-Dimensional Spacecraft Formation Flight Testbed for Terrestrial Charged Relative Motion Experiments.” 2011. Web. 07 Mar 2021.
Vancouver:
Seubert C. One-Dimensional Spacecraft Formation Flight Testbed for Terrestrial Charged Relative Motion Experiments. [Internet] [Doctoral dissertation]. University of Colorado; 2011. [cited 2021 Mar 07].
Available from: https://scholar.colorado.edu/asen_gradetds/38.
Council of Science Editors:
Seubert C. One-Dimensional Spacecraft Formation Flight Testbed for Terrestrial Charged Relative Motion Experiments. [Doctoral Dissertation]. University of Colorado; 2011. Available from: https://scholar.colorado.edu/asen_gradetds/38
University of Colorado
7.
Jones, Stephanie Leigh.
Negating the Yearly Eccentricity Magnitude Variation of Super-synchronous Disposal Orbits due to Solar Radiation Pressure.
Degree: MS, Aerospace Engineering Sciences, 2013, University of Colorado
URL: https://scholar.colorado.edu/asen_gradetds/60
► Solar radiation pressure alters satellites' eccentricity by accelerating and decelerating them during each orbit. The accumulated perturbation cancels yearly for geostationary satellites, but meanwhile…
(more)
▼ Solar radiation pressure alters satellites' eccentricity by accelerating and decelerating them during each orbit. The accumulated perturbation cancels yearly for geostationary satellites, but meanwhile the perigee radius changes. Disposed satellites must be reorbited higher to compensate, using more fuel. The examined disposal orbit points toward the Sun and uses the satellite's natural eccentricity. This causes the eccentricity vector to only change direction, keeping the perigee radius constant. This thesis verifies this behavior over one year with an analytical derivation and MATLAB simulation, gaining useful insights into its cause. The traditional and proposed disposal orbits are then modeled using NASA's GMAT for more realistic simulations. The proposed orbit's sensitivity to satellite and initialization errors is also examined. Relationships are developed to show these errors' effect on the perigee radius. In conclusion, while this orbit can be used in the short term, margins are necessary to guarantee protection of the geostationary belt.
Advisors/Committee Members: Hanspeter Schaub, Penina Axelrad, Jeffrey Parker.
Subjects/Keywords: disposal orbit; eccentricity; geostationary; orbit perturbation; satellite; solar radiation pressure; Aerospace Engineering; Engineering
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APA (6th Edition):
Jones, S. L. (2013). Negating the Yearly Eccentricity Magnitude Variation of Super-synchronous Disposal Orbits due to Solar Radiation Pressure. (Masters Thesis). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/60
Chicago Manual of Style (16th Edition):
Jones, Stephanie Leigh. “Negating the Yearly Eccentricity Magnitude Variation of Super-synchronous Disposal Orbits due to Solar Radiation Pressure.” 2013. Masters Thesis, University of Colorado. Accessed March 07, 2021.
https://scholar.colorado.edu/asen_gradetds/60.
MLA Handbook (7th Edition):
Jones, Stephanie Leigh. “Negating the Yearly Eccentricity Magnitude Variation of Super-synchronous Disposal Orbits due to Solar Radiation Pressure.” 2013. Web. 07 Mar 2021.
Vancouver:
Jones SL. Negating the Yearly Eccentricity Magnitude Variation of Super-synchronous Disposal Orbits due to Solar Radiation Pressure. [Internet] [Masters thesis]. University of Colorado; 2013. [cited 2021 Mar 07].
Available from: https://scholar.colorado.edu/asen_gradetds/60.
Council of Science Editors:
Jones SL. Negating the Yearly Eccentricity Magnitude Variation of Super-synchronous Disposal Orbits due to Solar Radiation Pressure. [Masters Thesis]. University of Colorado; 2013. Available from: https://scholar.colorado.edu/asen_gradetds/60
University of Colorado
8.
Mashburn, Jake Robert.
Analysis of Gnss-R Observations for Altimetry and Characterization of Earth Surfaces.
Degree: PhD, Aerospace Engineering Sciences, 2019, University of Colorado
URL: https://scholar.colorado.edu/asen_gradetds/252
► Global Navigation Satellite Systems (GNSS) provide abundant, opportunistic signals that can be used to probe the Earth’s environment and surface. Utilizing reflected GNSS signals…
(more)
▼ Global Navigation Satellite Systems (GNSS) provide abundant, opportunistic signals that can be used to probe the Earth’s environment and surface. Utilizing reflected GNSS signals for remote sensing is called GNSS Reflectometry (GNSS-R). Sensing of the ocean, land, and ice, with potentially dense measurement coverage and rapid revisit times, is possible due to the distributed geometry of GNSS constellations. GNSS-R can provide some advantages over other Earth observation systems, like traditional radar altimeters or microwave radiometers. GNSS signals are well characterized and encoded with precise ranging and timing information. There are multiple transmitters in view at any time, and GNSS signals occupy a protected frequency band (L-band) that penetrates Earth’s atmosphere in all weather conditions. This dissertation focuses on the development of methods and analysis techniques to observe sea surface height and sea ice extent with reflected GNSS signals. A tool-kit is developed to take advantage of experimental data sets from aircraft and spacecraft, and to produce state-of-the-art altimetric retrievals. Algorithms for the re-tracking of altimetric delays are demonstrated. Techniques to characterize and models to correct GNSS-R path delay errors are built through analysis of TechDemoSat-1 (TDS-1) and NASA’s Cyclone Global Navigation Satellite System (CYGNSS) flight data. Neither TDS-1 nor CYGNSS were designed to make precise altimetry observations. Thus, this work evaluates practical performance limitations of these GNSS-R observations, and establishes requirements for future missions. Altimetry results with height retrieval standard deviation of σH = 11 m with 1 sec and σH = 3.8 m with 10 sec observations, are shown. This work creates a foundation of techniques that can support future GNSS-R missions dedicated to ocean surface altimetry by producing results with sufficient accuracy and precision to the ocean science community. These tools are built to inform future mission designs and aid scientific interpretation of GNSS-R measurements.
Advisors/Committee Members: Penina Axelrad, Kristine M. Larson, Dennis Akos, Cinzia Zuffada, Dallas Masters.
Subjects/Keywords: altimetry; gnss-r; gps; ocean; sea ice; Global Navigation Satellite Systems; Global Positioning Systems; Aerospace Engineering; Remote Sensing
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APA (6th Edition):
Mashburn, J. R. (2019). Analysis of Gnss-R Observations for Altimetry and Characterization of Earth Surfaces. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/252
Chicago Manual of Style (16th Edition):
Mashburn, Jake Robert. “Analysis of Gnss-R Observations for Altimetry and Characterization of Earth Surfaces.” 2019. Doctoral Dissertation, University of Colorado. Accessed March 07, 2021.
https://scholar.colorado.edu/asen_gradetds/252.
MLA Handbook (7th Edition):
Mashburn, Jake Robert. “Analysis of Gnss-R Observations for Altimetry and Characterization of Earth Surfaces.” 2019. Web. 07 Mar 2021.
Vancouver:
Mashburn JR. Analysis of Gnss-R Observations for Altimetry and Characterization of Earth Surfaces. [Internet] [Doctoral dissertation]. University of Colorado; 2019. [cited 2021 Mar 07].
Available from: https://scholar.colorado.edu/asen_gradetds/252.
Council of Science Editors:
Mashburn JR. Analysis of Gnss-R Observations for Altimetry and Characterization of Earth Surfaces. [Doctoral Dissertation]. University of Colorado; 2019. Available from: https://scholar.colorado.edu/asen_gradetds/252
University of Colorado
9.
Gehly, Steven.
Estimation of Geosynchronous Space Objects Using Finite Set Statistics Filtering Methods.
Degree: PhD, Aerospace Engineering Sciences, 2016, University of Colorado
URL: https://scholar.colorado.edu/asen_gradetds/148
► The use of near Earth space has increased dramatically in the past few decades, and operational satellites are an integral part of modern society. The…
(more)
▼ The use of near Earth space has increased dramatically in the past few decades, and operational satellites are an integral part of modern society. The increased presence in space has led to an increase in the amount of orbital debris, which poses a growing threat to current and future space missions. Characterization of the debris environment is crucial to our continued use of high value orbit regimes such as the geosynchronous (GEO) belt. Objects in GEO pose unique challenges, by virtue of being densely spaced and tracked by a limited number of sensors in short observation windows. This research examines the use of a new class of multitarget filters to approach the problem of orbit determination for the large number of objects present. The filters make use of a recently developed mathematical toolbox derived from point process theory known as Finite Set Statistics (FISST). Details of implementing FISST-derived filters are discussed, and a qualitative and quantitative comparison between FISST and traditional multitarget estimators demonstrates the suitability of the new methods for space object estimation. Specific challenges in the areas of sensor allocation and initial orbit determination are addressed in the framework. The sensor allocation scheme makes use of information gain functionals as formulated for FISST to efficiently collect measurements on the full multitarget system. Results from a simulated network of three ground stations tracking a large catalog of geosynchronous objects demonstrate improved performance as compared to simpler, non-information theoretic tasking schemes. Further studies incorporate an initial orbit determination technique to initiate new tracks in the multitarget filter. Together with a sensor allocation scheme designed to search for new targets and maintain knowledge of the existing catalog, the method comprises a solution to the search-detect-track problem. Simulation results for a single sensor case show that the problem can be solved for multiple objects with no a priori information, even in the presence of missed detections and false measurements. Collectively, this research seeks to advance the capabilities of FISST-derived filters for use in the estimation of geosynchronous space objects; additional directions for future research are presented in the conclusion.
Advisors/Committee Members: Penina Axelrad, Brandon Jones, Jay McMahon, Nisar Ahmed, Gregory Beylkin.
Subjects/Keywords: Geosynchronous Orbit; Information Gain; Initial Orbit Determination; Multitarget Filtering; Random Finite Sets; Sensor Allocation; Aerospace Engineering
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APA (6th Edition):
Gehly, S. (2016). Estimation of Geosynchronous Space Objects Using Finite Set Statistics Filtering Methods. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/148
Chicago Manual of Style (16th Edition):
Gehly, Steven. “Estimation of Geosynchronous Space Objects Using Finite Set Statistics Filtering Methods.” 2016. Doctoral Dissertation, University of Colorado. Accessed March 07, 2021.
https://scholar.colorado.edu/asen_gradetds/148.
MLA Handbook (7th Edition):
Gehly, Steven. “Estimation of Geosynchronous Space Objects Using Finite Set Statistics Filtering Methods.” 2016. Web. 07 Mar 2021.
Vancouver:
Gehly S. Estimation of Geosynchronous Space Objects Using Finite Set Statistics Filtering Methods. [Internet] [Doctoral dissertation]. University of Colorado; 2016. [cited 2021 Mar 07].
Available from: https://scholar.colorado.edu/asen_gradetds/148.
Council of Science Editors:
Gehly S. Estimation of Geosynchronous Space Objects Using Finite Set Statistics Filtering Methods. [Doctoral Dissertation]. University of Colorado; 2016. Available from: https://scholar.colorado.edu/asen_gradetds/148
University of Colorado
10.
Geeraert, Jeroen L.
Multi-Satellite Orbit Determination Using Interferometric Observables with RF Localization Applications.
Degree: PhD, 2017, University of Colorado
URL: https://scholar.colorado.edu/asen_gradetds/192
► Very long baseline interferometry (VLBI) specifically same-beam interferometry (SBI), and dual-satellite geolocation are two fields of research not previously connected. This is due to…
(more)
▼ Very long baseline interferometry (VLBI) specifically same-beam interferometry (SBI), and dual-satellite geolocation are two fields of research not previously connected. This is due to the different application of each field, SBI is used for relative interplanetary navigation of two satellites while dual-satellite geolocation is used to locate the source of a radio frequency (RF) signal. In this dissertation however, we leverage both fields to create a novel method for multi-satellite orbit determination (OD) using time difference of arrival (TDOA) and frequency difference of arrival (FDOA) measurements. The measurements are double differenced between the satellites and the stations, in so doing, many of the common errors are canceled which can significantly improve measurement precision.
Provided with this novel OD technique, the observability is first analyzed to determine the benefits and limitations of this method. In all but a few scenarios the measurements successfully reduce the covariance when examining the Cramér-Rao Lower Bound (CRLB). Reduced observability is encountered with geostationary satellites as their motion with respect to the stations is limited, especially when only one baseline is used. However, when using satellite pairs with greater relative motion with respect to the stations, even satellites that are close to, but not exactly in a geostationary orbit can be estimated accurately. We find that in a strong majority of cases the OD technique provides lower uncertainties and solutions far more accurate than using conventional OD observables such as range and range-rate while also not being affected by common errors and biases. We specifically examine GEO-GEO, GEO-MEO, and GEO-LEO dual-satellite estimation cases. The work is further extended by developing a relative navigation scenario where the chief satellite is assumed to have perfect knowledge, or some small amount of uncertainty considered but not estimated, while estimating the deputy satellite state with respect to the chief. Once again the results demonstrate that the TDOA and FDOA OD results are favorable with faster dynamics over classical measurements.
This dissertation not only explores the OD side, but also gaps in geolocation research. First the mapping of ephemeris uncertainty to the geolocation covariance to provide a more realistic covariance was implemented. Furthermore, the geolocation solution was improved by appending a probabilistic altitude constraint to the posterior covariance, significantly reducing the projected geolocation uncertainty ellipse. The feasibility of using the geolocation setup to passively locate a LEO satellite was also considered. Finally the simulated results were verified using a long-arc of real data. The use of FDOA for small-body navigation and gravity recovery was also examined as an extended application.
Advisors/Committee Members: Jay W. McMahon, Penina Axelrad, Brandon Jones, Daniel Scheeres, Behrouz Touri.
Subjects/Keywords: astrodynamics; geolocation; interferometry; orbit determination; Aerospace Engineering
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APA (6th Edition):
Geeraert, J. L. (2017). Multi-Satellite Orbit Determination Using Interferometric Observables with RF Localization Applications. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/192
Chicago Manual of Style (16th Edition):
Geeraert, Jeroen L. “Multi-Satellite Orbit Determination Using Interferometric Observables with RF Localization Applications.” 2017. Doctoral Dissertation, University of Colorado. Accessed March 07, 2021.
https://scholar.colorado.edu/asen_gradetds/192.
MLA Handbook (7th Edition):
Geeraert, Jeroen L. “Multi-Satellite Orbit Determination Using Interferometric Observables with RF Localization Applications.” 2017. Web. 07 Mar 2021.
Vancouver:
Geeraert JL. Multi-Satellite Orbit Determination Using Interferometric Observables with RF Localization Applications. [Internet] [Doctoral dissertation]. University of Colorado; 2017. [cited 2021 Mar 07].
Available from: https://scholar.colorado.edu/asen_gradetds/192.
Council of Science Editors:
Geeraert JL. Multi-Satellite Orbit Determination Using Interferometric Observables with RF Localization Applications. [Doctoral Dissertation]. University of Colorado; 2017. Available from: https://scholar.colorado.edu/asen_gradetds/192
University of Colorado
11.
Bryant, Daniel S.
Spawn Model Derivations for Multi-object Orbit Determination within a Random Finite Set Framework.
Degree: PhD, 2017, University of Colorado
URL: https://scholar.colorado.edu/asen_gradetds/194
► Fragmentation events and large scale small-sat deployments are a significant threat; because of the sudden creation of many new objects posing potential risks to existing…
(more)
▼ Fragmentation events and large scale small-sat deployments are a significant threat; because of the sudden creation of many new objects posing potential risks to existing satellites, and the fact that current surveillance systems require laborious human intervention to identify and catalog these new objects. In the tracking community, the spontaneous appearance of new objects is referred to as birth, whereas spawning refers to the appearance of new objects generated by previously existing ones, such as a fragmentation event or small-sat deployment. In this dissertation, two-well known random finite set (RFS) filters are extended via mathematical derivation, aimed at performing initial orbit determination (IOD) of objects generated by spawning events. A Zero-Inflated Poisson (ZIP) spawn model is presented and a predicted cardinality expression for general spawn model configuration, capable of implementation via Partial Bell Polynomials, is derived for the Cardinalized Probability Hypothesis Density (CPHD) filter using a measure-theoretic approach. Generalized Labeled Multi-Bernoulli (GLMB) filter developments achieve a closed-form solution to the multi-object Bayes recursion capable of jointly estimating a spawned object's state and ancestry. Linear simulations demonstrate fundamental filter developments; the ZIP spawn model is shown to outperform other conventional models with the CPHD filter and multiple generations of spawn object ancestry are accurately estimated with the GLMB filter. Finally, non-linear simulations specific to Space Situational Awareness (SSA) IOD demonstrate the filters' efficacy, which include: fragmentation event and small-sat deployment scenarios, homogeneous and heterogeneous radar network observations, and spawning events that occur in and out of sensor field of view. This research shows that on-line multi-object IOD in the presence of spawning is possible within the RFS paradigm, and establishes a foundation upon which further SSA improvements can be investigated.
Advisors/Committee Members: Brandon A. Jones, Penina Axelrad, Jay McMahon, Nisar Ahmed, Vanja Dukic.
Subjects/Keywords: Bayesian estimation; generalized labeled multi-Bernoulli filter; multi-object filtering; multi-target tracking; object spawning; random finite sets; Aerospace Engineering
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APA (6th Edition):
Bryant, D. S. (2017). Spawn Model Derivations for Multi-object Orbit Determination within a Random Finite Set Framework. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/194
Chicago Manual of Style (16th Edition):
Bryant, Daniel S. “Spawn Model Derivations for Multi-object Orbit Determination within a Random Finite Set Framework.” 2017. Doctoral Dissertation, University of Colorado. Accessed March 07, 2021.
https://scholar.colorado.edu/asen_gradetds/194.
MLA Handbook (7th Edition):
Bryant, Daniel S. “Spawn Model Derivations for Multi-object Orbit Determination within a Random Finite Set Framework.” 2017. Web. 07 Mar 2021.
Vancouver:
Bryant DS. Spawn Model Derivations for Multi-object Orbit Determination within a Random Finite Set Framework. [Internet] [Doctoral dissertation]. University of Colorado; 2017. [cited 2021 Mar 07].
Available from: https://scholar.colorado.edu/asen_gradetds/194.
Council of Science Editors:
Bryant DS. Spawn Model Derivations for Multi-object Orbit Determination within a Random Finite Set Framework. [Doctoral Dissertation]. University of Colorado; 2017. Available from: https://scholar.colorado.edu/asen_gradetds/194
University of Colorado
12.
O'Keefe, Stephen Andrew.
Autonomous Sun-Direction Estimation Using Partially Underdetermined Coarse Sun Sensor Configurations.
Degree: PhD, Aerospace Engineering Sciences, 2015, University of Colorado
URL: https://scholar.colorado.edu/asen_gradetds/95
► In recent years there has been a significant increase in interest in smaller satellites as lower cost alternatives to traditional satellites, particularly with the…
(more)
▼ In recent years there has been a significant increase in interest in smaller satellites as lower cost alternatives to traditional satellites, particularly with the rise in popularity of the CubeSat. Due to stringent mass, size, and often budget constraints, these small satellites rely on making the most of inexpensive hardware components and sensors, such as coarse sun sensors (CSS) and magnetometers. More expensive high-accuracy sun sensors often combine multiple measurements, and use specialized electronics, to deterministically solve for the direction of the Sun. Alternatively, cosine-type CSS output a voltage relative to the input light and are attractive due to their very low cost, simplicity to manufacture, small size, and minimal power consumption. This research investigates using coarse sun sensors for performing robust attitude estimation in order to point a spacecraft at the Sun after deployment from a launch vehicle, or following a system fault.
As an alternative to using a large number of sensors, this thesis explores sun-direction estimation techniques with low computational costs that function well with underdetermined sets of CSS. Single-point estimators are coupled with simultaneous nonlinear control to achieve sun-pointing within a small percentage of a single orbit despite the partially underdetermined nature of the sensor suite. Leveraging an extensive analysis of the sensor models involved, sequential filtering techniques are shown to be capable of estimating the sun-direction to within a few degrees, with no a priori attitude information and using only CSS, despite the significant noise and biases present in the system. Detailed numerical simulations are used to compare and contrast the performance of the five different estimation techniques, with and without rate gyro measurements, their sensitivity to rate gyro accuracy, and their computation time.
One of the key concerns with reducing the number of CSS is sensor degradation and failure. In this thesis, a Modified Rodrigues Parameter based CSS calibration filter suitable for autonomous on-board operation is developed. The sensitivity of this method's accuracy to the available Earth albedo data is evaluated and compared to the required computational effort. The calibration filter is expanded to perform sensor fault detection, and promising results are shown for reduced resolution albedo models. All of the methods discussed provide alternative attitude, determination, and control system algorithms for small satellite missions looking to use inexpensive, small sensors due to size, power, or budget limitations.
Advisors/Committee Members: Hanspeter Schaub, Penina Axelrad, Nikolaus Correll, Brandon Jones, Jay McMahon.
Subjects/Keywords: Coarse Sun Sensors; Sun-Direction Estimation; Underdetermined; CubeSat; small satellite; mission limitation; Multi-Vehicle Systems and Air Traffic Control; Systems Engineering and Multidisciplinary Design Optimization; The Sun and the Solar System
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APA (6th Edition):
O'Keefe, S. A. (2015). Autonomous Sun-Direction Estimation Using Partially Underdetermined Coarse Sun Sensor Configurations. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/95
Chicago Manual of Style (16th Edition):
O'Keefe, Stephen Andrew. “Autonomous Sun-Direction Estimation Using Partially Underdetermined Coarse Sun Sensor Configurations.” 2015. Doctoral Dissertation, University of Colorado. Accessed March 07, 2021.
https://scholar.colorado.edu/asen_gradetds/95.
MLA Handbook (7th Edition):
O'Keefe, Stephen Andrew. “Autonomous Sun-Direction Estimation Using Partially Underdetermined Coarse Sun Sensor Configurations.” 2015. Web. 07 Mar 2021.
Vancouver:
O'Keefe SA. Autonomous Sun-Direction Estimation Using Partially Underdetermined Coarse Sun Sensor Configurations. [Internet] [Doctoral dissertation]. University of Colorado; 2015. [cited 2021 Mar 07].
Available from: https://scholar.colorado.edu/asen_gradetds/95.
Council of Science Editors:
O'Keefe SA. Autonomous Sun-Direction Estimation Using Partially Underdetermined Coarse Sun Sensor Configurations. [Doctoral Dissertation]. University of Colorado; 2015. Available from: https://scholar.colorado.edu/asen_gradetds/95
University of Colorado
13.
Pratt, John A.
New Time and Multipath Augmentations for the Global Positioning System.
Degree: PhD, Aerospace Engineering Sciences, 2015, University of Colorado
URL: https://scholar.colorado.edu/asen_gradetds/115
► Although developed with a narrow focus in mind, use of GPS has expanded into dozens of fields in industry, science, and military applications. The…
(more)
▼ Although developed with a narrow focus in mind, use of GPS has expanded into dozens of fields in industry, science, and military applications. The purpose of the research detailed in this dissertation is an increase in the utility of GPS by improving primary applications of the constellation and expand the practicality of some secondary applications. The first portion of this dissertation focuses on the development of clock estimation algorithms for a GPS aiding system called iGPS which has been designed to improve the performance of the system in challenging environments. Central to the functioning of iGPS are the Iridium communication satellites. This dissertation describes a Kalman filter for estimating Iridium satellite clock biases from GPS-like measurements at an interval of 10 s. Typical results show the current filter to be accurate to within 200 ns while always meeting the initial system specification of half a microsecond. The following chapter examines the expediency of increasing the number of terms used to represent the clock bias in the broadcast message and it is shown that the current broadcast message is sufficient. The second half of the dissertation deals with the use of GPS multipath as an environmental measurement. It is shown that reflections of GPS signals from the ground can be used to estimate several important phenological indicators relative to the vegetation surrounding the GPS antenna. Methods are developed for refining the reflected signal and preparing it for use as a vegetation index. Finally, the effect of temperature and multipath suppression algorithms on the GPS multipath data is examined relative to its viability for use as previously described. It is shown that these effects are minor in the majority of the GPS sites used in this study and that the data can be adjusted to avoid temperature difficulties.
Advisors/Committee Members: Kristine Larson, Penina Axelrad, Dennis Akos, Judah Levine, Eric Small.
Subjects/Keywords: GPS interferometric reflectometry; Time transfer; Aerospace Engineering
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APA (6th Edition):
Pratt, J. A. (2015). New Time and Multipath Augmentations for the Global Positioning System. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/115
Chicago Manual of Style (16th Edition):
Pratt, John A. “New Time and Multipath Augmentations for the Global Positioning System.” 2015. Doctoral Dissertation, University of Colorado. Accessed March 07, 2021.
https://scholar.colorado.edu/asen_gradetds/115.
MLA Handbook (7th Edition):
Pratt, John A. “New Time and Multipath Augmentations for the Global Positioning System.” 2015. Web. 07 Mar 2021.
Vancouver:
Pratt JA. New Time and Multipath Augmentations for the Global Positioning System. [Internet] [Doctoral dissertation]. University of Colorado; 2015. [cited 2021 Mar 07].
Available from: https://scholar.colorado.edu/asen_gradetds/115.
Council of Science Editors:
Pratt JA. New Time and Multipath Augmentations for the Global Positioning System. [Doctoral Dissertation]. University of Colorado; 2015. Available from: https://scholar.colorado.edu/asen_gradetds/115
University of Colorado
14.
Fujimoto, Kohei.
New Methods in Optical Track Association and Uncertainty Mapping of Earth-Orbiting Objects.
Degree: PhD, Aerospace Engineering Sciences, 2013, University of Colorado
URL: https://scholar.colorado.edu/asen_gradetds/57
► As more and more sensing capabilities for space surveillance are introduced, we expect that both correlated and uncorrelated tracks of resident space objects will…
(more)
▼ As more and more sensing capabilities for space surveillance are introduced, we expect that both correlated and uncorrelated tracks of resident space objects will drastically increase. Existing observation association techniques rely on simplified dynamics, ad hoc association criteria, and linear propagation of Gaussian uncertainty. To maintain an accurate catalog of resident space objects now and into the future, however, a more consistent description of the uncertainty associated with said objects is desired. Two characteristics of the space situational awareness problem are applicable to this goal: that the type of observation significantly influences the geometry of the observational uncertainty, and that the dynamical system is amenable to analytic or semi-analytic solution techniques. In this dissertation, each of these characteristics are examined and ultimately applied to the problem of optical track association, often referred to as the too-short arc problem. First, an analytical method of non-linear uncertainty propagation is discussed. A special solution to the Fokker-Planck equations for deterministic systems and the state transition tensor concept are combined so that, given an analytical expression of both the initial probability distribution and the dynamics, the probability distribution may be expressed analytically for all time. Next, an observation association technique is proposed which involves admissible regions: probability density functions representing not only the measurement errors but also the limited knowledge in the unobserved variables. Bayes' rule is directly applied to associate multiple observations and subsequently obtain an orbit estimate. A quantitative argument on the effects of measurement errors on the admissible region, and consequently direct Bayesian track association, are also given. Finally, the proposed approach to short-arc association and initial orbit determination are applied to optical observations taken at the Astronomical Institute of the
University of Bern. In addition to matching over half of the objects detected by conventional techniques, the proposed method finds two additional objects at or near geostationary altitude, all without a priori information.
Advisors/Committee Members: Daniel J. Scheeres, George H. Born, Penina Axelrad, Elizabeth Bradley, David Vallado.
Subjects/Keywords: admissible region; astrodynamics; optical observations; propagation of uncertainty; space situational awareness; too-short arc; Aerospace Engineering
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APA (6th Edition):
Fujimoto, K. (2013). New Methods in Optical Track Association and Uncertainty Mapping of Earth-Orbiting Objects. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/57
Chicago Manual of Style (16th Edition):
Fujimoto, Kohei. “New Methods in Optical Track Association and Uncertainty Mapping of Earth-Orbiting Objects.” 2013. Doctoral Dissertation, University of Colorado. Accessed March 07, 2021.
https://scholar.colorado.edu/asen_gradetds/57.
MLA Handbook (7th Edition):
Fujimoto, Kohei. “New Methods in Optical Track Association and Uncertainty Mapping of Earth-Orbiting Objects.” 2013. Web. 07 Mar 2021.
Vancouver:
Fujimoto K. New Methods in Optical Track Association and Uncertainty Mapping of Earth-Orbiting Objects. [Internet] [Doctoral dissertation]. University of Colorado; 2013. [cited 2021 Mar 07].
Available from: https://scholar.colorado.edu/asen_gradetds/57.
Council of Science Editors:
Fujimoto K. New Methods in Optical Track Association and Uncertainty Mapping of Earth-Orbiting Objects. [Doctoral Dissertation]. University of Colorado; 2013. Available from: https://scholar.colorado.edu/asen_gradetds/57
University of Colorado
15.
Bradley, Ben K.
Numerical Algorithms for Precise and Efficient Orbit Propagation and Positioning.
Degree: PhD, Aerospace Engineering Sciences, 2015, University of Colorado
URL: https://scholar.colorado.edu/asen_gradetds/125
► Motivated by the growing space catalog and the demands for precise orbit determination with shorter latency for science and reconnaissance missions, this research improves…
(more)
▼ Motivated by the growing space catalog and the demands for precise orbit determination with shorter latency for science and reconnaissance missions, this research improves the computational performance of orbit propagation through more efficient and precise numerical integration and frame transformation implementations. Propagation of satellite orbits is required for astrodynamics applications including mission design, orbit determination in support of operations and payload data analysis, and conjunction assessment. Each of these applications has somewhat different requirements in terms of accuracy, precision, latency, and computational load. This dissertation develops procedures to achieve various levels of accuracy while minimizing computational cost for diverse orbit determination applications. This is done by addressing two aspects of orbit determination: (1) numerical integration used for orbit propagation and (2) precise frame transformations necessary for force model evaluation and station coordinate rotations.
This dissertation describes a recently developed method for numerical integration, dubbed Bandlimited Collocation Implicit Runge-Kutta (BLC-IRK), and compare its efficiency in propagating orbits to existing techniques commonly used in astrodynamics. The BLC-IRK scheme uses generalized Gaussian quadratures for bandlimited functions. It requires significantly fewer force function evaluations than explicit Runge-Kutta schemes and approaches the efficiency of the 8th-order Gauss-Jackson multistep method.
Converting between the Geocentric Celestial Reference System (GCRS) and International Terrestrial Reference System (ITRS) is necessary for many applications in astrodynamics, such as orbit propagation, orbit determination, and analyzing geoscience data from satellite missions. This dissertation provides simplifications to the Celestial Intermediate Origin (CIO) transformation scheme and Earth orientation parameter (EOP) storage for use in positioning and orbit propagation, yielding savings in computation time and memory. Orbit propagation and position transformation simulations are analyzed to generate a complete set of recommendations for performing the ITRS/GCRS transformation for a wide range of needs, encompassing real-time on-board satellite operations and precise post-processing applications. In addition, a complete derivation of the ITRS/GCRS frame transformation time-derivative is detailed for use in velocity transformations between the GCRS and ITRS and is applied to orbit propagation in the rotating ITRS.
EOP interpolation methods and ocean tide corrections are shown to impact the ITRS/GCRS transformation accuracy at the level of 5 cm and 20 cm on the surface of the Earth and at the Global Positioning System (GPS) altitude, respectively. The precession-nutation and EOP simplifications yield maximum propagation errors of approximately 2 cm and 1 m after 15 minutes and 6 hours in low-Earth orbit (LEO), respectively, while reducing computation time and memory usage. Finally,…
Advisors/Committee Members: Penina Axelrad, George H. Born, Brandon A. Jones, Webster Cash, Daniel J. Scheeres.
Subjects/Keywords: Earth orientation parameters; International Terrestrial Reference System; Orbit propagation; Precise frame transformations; Navigation, Guidance, Control and Dynamics
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APA (6th Edition):
Bradley, B. K. (2015). Numerical Algorithms for Precise and Efficient Orbit Propagation and Positioning. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/125
Chicago Manual of Style (16th Edition):
Bradley, Ben K. “Numerical Algorithms for Precise and Efficient Orbit Propagation and Positioning.” 2015. Doctoral Dissertation, University of Colorado. Accessed March 07, 2021.
https://scholar.colorado.edu/asen_gradetds/125.
MLA Handbook (7th Edition):
Bradley, Ben K. “Numerical Algorithms for Precise and Efficient Orbit Propagation and Positioning.” 2015. Web. 07 Mar 2021.
Vancouver:
Bradley BK. Numerical Algorithms for Precise and Efficient Orbit Propagation and Positioning. [Internet] [Doctoral dissertation]. University of Colorado; 2015. [cited 2021 Mar 07].
Available from: https://scholar.colorado.edu/asen_gradetds/125.
Council of Science Editors:
Bradley BK. Numerical Algorithms for Precise and Efficient Orbit Propagation and Positioning. [Doctoral Dissertation]. University of Colorado; 2015. Available from: https://scholar.colorado.edu/asen_gradetds/125
University of Colorado
16.
Chen, Cao.
Exploration of the Mystery of Polar Wave Dynamics with Lidar/Radar Observations and General Circulation Models & Development of New Wave Analysis Methods.
Degree: PhD, Aerospace Engineering Sciences, 2016, University of Colorado
URL: https://scholar.colorado.edu/asen_gradetds/146
► The Space-atmosphere interaction region (SAIR) between ~50 and 200 km is one of the key factors enabling our Earth to harbor life. Its fundamental…
(more)
▼ The Space-atmosphere interaction region (SAIR) between ~50 and 200 km is one of the key factors enabling our Earth to harbor life. Its fundamental processes are believed to be universal and applicable to the atmospheres of Earth-like planets throughout our galaxy. However, the SAIR remains one of the least observed and understood regions. This thesis aims to advance the observations and characterizations of atmospheric waves that are fundamental to shaping the SAIR, especially exploring the mystery of persistent inertia-gravity waves, discovered by our Fe Boltzmann lidar measurements of temperatures at McMurdo (77.8°S, 166.7°E), Antarctica.
This thesis discovers a new wave phenomenon in the Antarctic middle and upper atmosphere, namely the persistent inertia-gravity waves with periods of 3–10 h. This group of large-amplitude waves dominates the temperature perturbations from the stratosphere to the lower thermosphere (about 30–115 km). They occur so frequently as to appear endless and uninterrupted, impacting the composition, chemistry and thermodynamics of the SAIR. This thesis reports the first simultaneous lidar/radar observations of inertia-gravity waves in Antarctica. Utilizing the lidar data in June from 2011 to 2015, this thesis characterizes the persistent gravity wave properties for the first time. These waves exhibit a uniform dominant vertical wavelength of 20–30 km across periods of 3.5–10 h and vertical phase speeds of 0.8–2 m/s. They possess more than half of the spectral energy for ~93% of the time. An analysis of the 65-h lidar data on 28–30 June 2014 demonstrates multiple wave packets spanning as long as 60 h. Further analysis of May and July data confirms the persistency and dominancy of these waves but reveal a month-to-month variability.
This thesis develops a system of wave analysis methods, including extracting gravity waves from ~30–155 km in the neutral atmosphere for the first time. Our methodologies also include the temporal hodograph methods for simultaneous lidar/radar data; improved 1-D Morlet wavelet transform methods; rigorous pre-whitening and post-coloring spectral analysis techniques; and automated 2-D Morlet wavelet analysis and synthesis methods. Successful application of these methodologies provides new insights into gravity waves, their sources and impacts on the whole atmosphere and space.
Advisors/Committee Members: Xinzhao Chu, Jeffrey M. Forbes, Adrian J. McDonald, Sharon Vadas, Penina Axelrad.
Subjects/Keywords: 2-D Wavelet; Antarctic Middle and Upper Atmosphere; Intertia-Gravity Wave; Lidar; Persistent 3-10 h Wave; Radar; Aerospace Engineering
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APA ·
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APA (6th Edition):
Chen, C. (2016). Exploration of the Mystery of Polar Wave Dynamics with Lidar/Radar Observations and General Circulation Models & Development of New Wave Analysis Methods. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/146
Chicago Manual of Style (16th Edition):
Chen, Cao. “Exploration of the Mystery of Polar Wave Dynamics with Lidar/Radar Observations and General Circulation Models & Development of New Wave Analysis Methods.” 2016. Doctoral Dissertation, University of Colorado. Accessed March 07, 2021.
https://scholar.colorado.edu/asen_gradetds/146.
MLA Handbook (7th Edition):
Chen, Cao. “Exploration of the Mystery of Polar Wave Dynamics with Lidar/Radar Observations and General Circulation Models & Development of New Wave Analysis Methods.” 2016. Web. 07 Mar 2021.
Vancouver:
Chen C. Exploration of the Mystery of Polar Wave Dynamics with Lidar/Radar Observations and General Circulation Models & Development of New Wave Analysis Methods. [Internet] [Doctoral dissertation]. University of Colorado; 2016. [cited 2021 Mar 07].
Available from: https://scholar.colorado.edu/asen_gradetds/146.
Council of Science Editors:
Chen C. Exploration of the Mystery of Polar Wave Dynamics with Lidar/Radar Observations and General Circulation Models & Development of New Wave Analysis Methods. [Doctoral Dissertation]. University of Colorado; 2016. Available from: https://scholar.colorado.edu/asen_gradetds/146
University of Colorado
17.
Yao, Jian.
Continuous GPS Carrier-Phase Time Transfer.
Degree: PhD, Physics, 2014, University of Colorado
URL: https://scholar.colorado.edu/phys_gradetds/122
► Time transfer (TT) is the process of transmitting a timing signal from one place to another place. It has applications to the formation and…
(more)
▼ Time transfer (TT) is the process of transmitting a timing signal from one place to another place. It has applications to the formation and realization of Coordinated Universal Time (UTC), telecommunications, electrical power grids, and even stock exchanges. TT is the actual bottleneck of the UTC formation and realization since the technology of atomic clocks is almost always ahead of that of TT. GPS carrier-phase time transfer (GPSCPTT), as a mainstream TT technique accepted by most national timing laboratories, has suffered from the day-boundary-discontinuity (day-BD) problem for many years. This makes us difficult to observe a remote Cesium fountain clock behavior even after a few days. We find that day-BD comes from the GPS code noise. The day-BD can be lowered by ~40% if more satellite-clock information is provided and if a few GPS receivers at the same station are averaged. To completely eliminate day-BD, the RINEX-Shift (RS) and revised RS (RRS) algorithms have been designed. The RS/RRS result matches the two-way satellite time/frequency transfer (TWSTFT) result much better than the conventional GPSCPTT result. With the RS/RRS algorithm, we are able to observe a remote Cesium fountain after half a day. We also study the BD due to GPS data anomalies (anomaly-BD). A simple curve-fitting strategy can eliminate the anomaly-BD. Thus, we achieve continuous GPSCPTT after eliminating both day-BD and anomaly-BD.
Advisors/Committee Members: Judah Levine, Neil Ashby, Peter L. Bender, Penina Axelrad, Dennis M. Akos.
Subjects/Keywords: Boundary Discontinuity; Carrier Phase; GPS; Precise Point Positioning; RINEX-Shift Algorithm; Time Transfer; Geographic Information Sciences; Navigation, Guidance, Control and Dynamics; Physics; Systems Engineering and Multidisciplinary Design Optimization
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APA (6th Edition):
Yao, J. (2014). Continuous GPS Carrier-Phase Time Transfer. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/phys_gradetds/122
Chicago Manual of Style (16th Edition):
Yao, Jian. “Continuous GPS Carrier-Phase Time Transfer.” 2014. Doctoral Dissertation, University of Colorado. Accessed March 07, 2021.
https://scholar.colorado.edu/phys_gradetds/122.
MLA Handbook (7th Edition):
Yao, Jian. “Continuous GPS Carrier-Phase Time Transfer.” 2014. Web. 07 Mar 2021.
Vancouver:
Yao J. Continuous GPS Carrier-Phase Time Transfer. [Internet] [Doctoral dissertation]. University of Colorado; 2014. [cited 2021 Mar 07].
Available from: https://scholar.colorado.edu/phys_gradetds/122.
Council of Science Editors:
Yao J. Continuous GPS Carrier-Phase Time Transfer. [Doctoral Dissertation]. University of Colorado; 2014. Available from: https://scholar.colorado.edu/phys_gradetds/122
University of Colorado
18.
Griggs, Erin Rose.
Analyses for a Modernized GNSS Radio Occultation Receiver.
Degree: PhD, Aerospace Engineering Sciences, 2015, University of Colorado
URL: https://scholar.colorado.edu/asen_gradetds/93
► Global Navigation Satellite System (GNSS) radio occultation (RO) is a remote sensing technique that exploits existing navigation signals to make global, real-time observations of…
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▼ Global Navigation Satellite System (GNSS) radio occultation (RO) is a remote sensing technique that exploits existing navigation signals to make global, real-time observations of the Earth's atmosphere. A specialized RO receiver makes measurements of signals originating from a transmitter onboard a GNSS spacecraft near the Earth's horizon. The radio wave is altered during passage through the Earth's atmosphere. The changes in the received signals are translated to the refractivity characteristics of the intervening medium, which enable the calculation of atmospheric pressure, temperature, and humidity.
Current satellite missions employing GNSS RO have provided invaluable and timely information for weather and climate applications. Existing constellations of occultation satellites, however, are aging and producing fewer quality measurements. Replacement fleets of RO satellites are imperative to sustain and improve the global coverage and operational impact achieved by the current generation of RO satellites. This dissertation describes studies that facilitate the development of next generation RO receivers and satellite constellations. Multiple research efforts were conducted that aim to improve the quantity and quality of measurements made by a future satellite-based RO collection system.
These studies range in magnitude and impact, and begin with a receiver development study using ground-based occultation data. Future RO constellations and collection opportunities were simulated and autonomous occultation prediction and scheduling capabilities were implemented. Finally, a comprehensive study was conducted to characterize the stability of the GNSS atomic frequency standards. Oscillator stability for a subset of satellites in the GNSS was found to be of insufficient quality at timescales relevant to RO collections and would degrade the atmospheric profiling capabilities of an RO system utilizing these signals. Recommendations for a high-rate clock correction network are proposed, which provides significant improvement to the fractional errors in the derived refractivity, pressure, and temperature values caused by the oscillator instabilities.
Advisors/Committee Members: Dennis M. Akos, Penina Axelrad, George H. Born, Emil R. Kursinski, Judah Levine.
Subjects/Keywords: Allan deviation; GNSS; oscillator stability; radio occultation; software receiver; Aerospace Engineering; Atmospheric Sciences; Remote Sensing; Systems and Communications; Systems Engineering and Multidisciplinary Design Optimization
Record Details
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Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Griggs, E. R. (2015). Analyses for a Modernized GNSS Radio Occultation Receiver. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/93
Chicago Manual of Style (16th Edition):
Griggs, Erin Rose. “Analyses for a Modernized GNSS Radio Occultation Receiver.” 2015. Doctoral Dissertation, University of Colorado. Accessed March 07, 2021.
https://scholar.colorado.edu/asen_gradetds/93.
MLA Handbook (7th Edition):
Griggs, Erin Rose. “Analyses for a Modernized GNSS Radio Occultation Receiver.” 2015. Web. 07 Mar 2021.
Vancouver:
Griggs ER. Analyses for a Modernized GNSS Radio Occultation Receiver. [Internet] [Doctoral dissertation]. University of Colorado; 2015. [cited 2021 Mar 07].
Available from: https://scholar.colorado.edu/asen_gradetds/93.
Council of Science Editors:
Griggs ER. Analyses for a Modernized GNSS Radio Occultation Receiver. [Doctoral Dissertation]. University of Colorado; 2015. Available from: https://scholar.colorado.edu/asen_gradetds/93
. 
Open Access Theses and Dissertations