+publisher:"University of Colorado" +contributor:("Daniel Scheeres")

University of Colorado

1. Balducci, Marc. Orbit Uncertainty Propagation with Separated Representations.

Degree: PhD, 2018, University of Colorado

URL: https://scholar.colorado.edu/asen_gradetds/236

► In light of recent collisions and an increasing population of objects in Earth orbit, the space situational awareness community has significant motivation to develop novel… (more)

▼ In light of recent collisions and an increasing population of objects in Earth orbit, the space situational awareness community has significant motivation to develop novel and effective methods of predicting the behavior of object states under the presence of uncertainty. Unfortunately, approaches to uncertainty quantification often make simplifying assumptions in order to reduce computation cost. This thesis proposes the method of separated representations (SR) as an efficient and accurate approach to uncertainty quantification. The properties of an orthogonal polynomial basis and a uni-directional least squares regression approach allow for the theoretical computation cost of SR to remain low when compared to Monte Carlo or other surrogate methods. Specifically, SR does not suffer from the curse of dimensionality, where computation cost increases exponentially with respect to input dimension. Benefits of this low computation cost are shown in a series of low Earth orbit test cases, where SR is used to accurately approximate non-Gaussian posterior distribution functions. Here, the dimension of the problem is increased from 6 to 20 without incurring significantly more computation time. Taking advantage of a large input dimension, this research presents a global sensitivity analysis computed via SR, which affords a more nuanced analysis of a previously examined case in the literature. By considering design variables, SR is formulated to perform optimization under uncertainty. A novel method that utilizes a Brent optimizer to create training data at unique times of closest approach is devised and implemented in order to detect low probability collision events. This methodology is leveraged to design an optimal avoidance maneuver, which would be intractable when using traditional Monte Carlo. Lastly, a multi-element algorithm is formulated and presented to estimate solutions that are challenging for unmodified SR. This multi-element SR leads to orders of magnitude in accuracy improvement when considering the ability of unmodified SR to approximate discontinuous, multimodal, or diffuse solutions. Advisors/Committee Members: Brandon A. Jones, Alireza Doostan, Gregory Beylkin, Daniel Scheeres.

Subjects/Keywords: separated representations; uncertainty quantification; earth orbit; avoidance maneuver; multi-element algorithm; Aerospace Engineering; Mathematics

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APA (6^th Edition):

Balducci, M. (2018). Orbit Uncertainty Propagation with Separated Representations. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/236

Chicago Manual of Style (16^th Edition):

Balducci, Marc. “Orbit Uncertainty Propagation with Separated Representations.” 2018. Doctoral Dissertation, University of Colorado. Accessed February 28, 2021. https://scholar.colorado.edu/asen_gradetds/236.

MLA Handbook (7^th Edition):

Balducci, Marc. “Orbit Uncertainty Propagation with Separated Representations.” 2018. Web. 28 Feb 2021.

Vancouver:

Balducci M. Orbit Uncertainty Propagation with Separated Representations. [Internet] [Doctoral dissertation]. University of Colorado; 2018. [cited 2021 Feb 28]. Available from: https://scholar.colorado.edu/asen_gradetds/236.

Council of Science Editors:

Balducci M. Orbit Uncertainty Propagation with Separated Representations. [Doctoral Dissertation]. University of Colorado; 2018. Available from: https://scholar.colorado.edu/asen_gradetds/236

University of Colorado

2. Shupe, Nathan C. Orbit Options for an Orion-Class Spacecraft Mission to a Near-Earth Object.

Degree: MS, Aerospace Engineering Sciences, 2010, University of Colorado

URL: https://scholar.colorado.edu/asen_gradetds/7

► Based on the recommendations of the Augustine Commission, President Obama has proposed a vision for U.S. human spaceflight in the post-Shuttle era which includes… (more)

▼ Based on the recommendations of the Augustine Commission, President Obama has proposed a vision for U.S. human spaceflight in the post-Shuttle era which includes a manned mission to a Near-Earth Object (NEO). A 2006-2007 study commissioned by the Constellation Program Advanced Projects Office investigated the feasibility of sending a crewed Orion spacecraft to a NEO using different combinations of elements from the latest launch system architecture at that time. The study found a number of suitable mission targets in the database of known NEOs, and predicted that the number of candidate NEOs will continue to increase as more advanced observatories come online and execute more detailed surveys of the NEO population. The objective of this thesis is to pick up where the previous Constellation study left off by considering what orbit options are available for an Orion-class spacecraft upon arrival at a NEO. A model including multiple perturbations (solar radiation pressure, solar gravity, non-spherical mass distribution of the central body) to two-body dynamics is constructed to numerically integrate the motion of a satellite in close proximity to a small body in an elliptical orbit about the Sun. Analytical limits derived elsewhere in the literature for the thresholds on the size of the satellite orbit required to maintain stability in the presence of these perturbing forces are verified by the numerical model. Simulations about NEOs possessing various physical parameters (size, shape, rotation period) are then used to empirically develop general guidelines for establishing orbits of an Orion-class spacecraft about a NEO. It is found that an Orion-class spacecraft can orbit NEOs at any distance greater than the NEO surface height and less than the maximum semi-major axis allowed by the solar radiation pressure perturbation, provided that the ellipticity perturbation is suffciently weak (this condition is met if the NEO is relatively round and/or has a long rotation period) for orbits falling below the minimum threshold for guarding against its effects. NEOs as small as ≈ 20 m in diameter can be orbited by an Orion-class spacecraft, provided the rotation period is not too long (< 30 hours) if the ellipticity perturbation is strong. There are cases of small, very slowly rotating NEOs that cannot be orbited by an Orion-class spacecraft at any distance, but generally these NEOs are required to have severely elongated shapes in order to maintain the strength of the ellipticity perturbation in spite of their longer rotation periods. Finally, terminator frozen orbits are found to be the best orbit option for a manned mission to a NEO, since their stability in the face of multiple perturbations provides an ideal platform for conducting scientific observations of the NEO and launching astronaut excursions to the NEO surface. Advisors/Committee Members: Daniel Scheeres, George Born, Hanspeter Schaub.

Subjects/Keywords: Human Exploration; Near Earth Object; Orbits; Orion; Aerospace Engineering; Navigation, Guidance, Control and Dynamics

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APA (6^th Edition):

Shupe, N. C. (2010). Orbit Options for an Orion-Class Spacecraft Mission to a Near-Earth Object. (Masters Thesis). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/7

Chicago Manual of Style (16^th Edition):

Shupe, Nathan C. “Orbit Options for an Orion-Class Spacecraft Mission to a Near-Earth Object.” 2010. Masters Thesis, University of Colorado. Accessed February 28, 2021. https://scholar.colorado.edu/asen_gradetds/7.

MLA Handbook (7^th Edition):

Shupe, Nathan C. “Orbit Options for an Orion-Class Spacecraft Mission to a Near-Earth Object.” 2010. Web. 28 Feb 2021.

Vancouver:

Shupe NC. Orbit Options for an Orion-Class Spacecraft Mission to a Near-Earth Object. [Internet] [Masters thesis]. University of Colorado; 2010. [cited 2021 Feb 28]. Available from: https://scholar.colorado.edu/asen_gradetds/7.

Council of Science Editors:

Shupe NC. Orbit Options for an Orion-Class Spacecraft Mission to a Near-Earth Object. [Masters Thesis]. University of Colorado; 2010. Available from: https://scholar.colorado.edu/asen_gradetds/7

University of Colorado

3. Panosian, Stephen. Stiffness Analysis of the Tethered Coulomb Structure Concept and Application.

Degree: MS, Aerospace Engineering Sciences, 2011, University of Colorado

URL: https://scholar.colorado.edu/asen_gradetds/16

► This thesis investigates the Tethered Coulomb Structure (TCS) concept and its operating regime for creating large space structures and for providing satellite situational awareness.… (more)

Subjects/Keywords: Coulomb; Electrostatics; Formation; Spacecraft; Tether; Aerospace Engineering; Structures and Materials

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APA (6^th Edition):

Panosian, S. (2011). Stiffness Analysis of the Tethered Coulomb Structure Concept and Application. (Masters Thesis). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/16

Chicago Manual of Style (16^th Edition):

Panosian, Stephen. “Stiffness Analysis of the Tethered Coulomb Structure Concept and Application.” 2011. Masters Thesis, University of Colorado. Accessed February 28, 2021. https://scholar.colorado.edu/asen_gradetds/16.

MLA Handbook (7^th Edition):

Panosian, Stephen. “Stiffness Analysis of the Tethered Coulomb Structure Concept and Application.” 2011. Web. 28 Feb 2021.

Vancouver:

Panosian S. Stiffness Analysis of the Tethered Coulomb Structure Concept and Application. [Internet] [Masters thesis]. University of Colorado; 2011. [cited 2021 Feb 28]. Available from: https://scholar.colorado.edu/asen_gradetds/16.

Council of Science Editors:

Panosian S. Stiffness Analysis of the Tethered Coulomb Structure Concept and Application. [Masters Thesis]. University of Colorado; 2011. Available from: https://scholar.colorado.edu/asen_gradetds/16

University of Colorado

4. 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 (6^th 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 (16^th Edition):

Hartzell, Christine M. “The Dynamics of Near-Surface Dust on Airless Bodies.” 2012. Doctoral Dissertation, University of Colorado. Accessed February 28, 2021. https://scholar.colorado.edu/asen_gradetds/48.

MLA Handbook (7^th Edition):

Hartzell, Christine M. “The Dynamics of Near-Surface Dust on Airless Bodies.” 2012. Web. 28 Feb 2021.

Vancouver:

Hartzell CM. The Dynamics of Near-Surface Dust on Airless Bodies. [Internet] [Doctoral dissertation]. University of Colorado; 2012. [cited 2021 Feb 28]. 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

5. Jasper, Lee E.Z. Open-Loop Thrust Profile Development for Tethered Towing of Large Space Objects.

Degree: PhD, Aerospace Engineering Sciences, 2014, University of Colorado

URL: https://scholar.colorado.edu/asen_gradetds/82

► Towing objects in space has become an increasingly researched mission concept. Active debris removal, satellite servicing, and asteroid retrieval concepts in many cases rely… (more)

▼ Towing objects in space has become an increasingly researched mission concept. Active debris removal, satellite servicing, and asteroid retrieval concepts in many cases rely on a thrusting vehicle to redirect and steer a passive object. Focus is often placed on the method of attachment, considering techniques such as grappling or netting the passive object. However, the actual process of towing, once capture has occurred, has not yet received much attention. This research considers the process of towing in space with the tug and passive object attached by a tether. Tethers are not only an effective way of transmitting forces, but they are utilized on many of the towing concepts considered, especially in orbital debris removal. Because the two end bodies are tethered, there is a potential for collision after any maneuver. To avoid collisions, the maneuver, and therefore thrust profile, must be designed in such a way as to limit separation distance reduction between the end bodies. Open-loop input shaping techniques are developed and employed in order to control the flexible system in both deep space and on-orbit environments. To study the behavior, an active debris removal system is proposed as a case study. This system, called the tethered-tug, considers using the reserve fuel from a recently launched upper stage rocket to rendezvous with, capture, and tow a near-by debris object. The system’s performance is considered for five distinct open-loop thrust control profiles including on-off/step, frequency notched, discretized notch, Posicast, and bang-off-bang. Tether property variations are also considered along with off-axis towing, slack tethers, and debris with initial rotation rates. Input shaping is not only necessary but, it can be robust to unknown system properties while nearly zeroing relative motion between the end bodies. When considering on-orbit behavior specifically, the system settles into a tumbling or gravity gradient oscillation formation. This is highly advantageous because the orbital dynamics keep the end bodies separated. While the study focuses on the debris problem, conclusions from this dissertation are applicable to general tethered towing mission concepts. Advisors/Committee Members: Hanspeter Schaub, John K. Bennett, Brandon Jones, Jeffrey Parker, Daniel Scheeres.

Subjects/Keywords: active debris removal; input shaping; orbital debris; space tether; tethered towing; Aerospace Engineering

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APA (6^th Edition):

Jasper, L. E. Z. (2014). Open-Loop Thrust Profile Development for Tethered Towing of Large Space Objects. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/82

Chicago Manual of Style (16^th Edition):

Jasper, Lee E Z. “Open-Loop Thrust Profile Development for Tethered Towing of Large Space Objects.” 2014. Doctoral Dissertation, University of Colorado. Accessed February 28, 2021. https://scholar.colorado.edu/asen_gradetds/82.

MLA Handbook (7^th Edition):

Jasper, Lee E Z. “Open-Loop Thrust Profile Development for Tethered Towing of Large Space Objects.” 2014. Web. 28 Feb 2021.

Vancouver:

Jasper LEZ. Open-Loop Thrust Profile Development for Tethered Towing of Large Space Objects. [Internet] [Doctoral dissertation]. University of Colorado; 2014. [cited 2021 Feb 28]. Available from: https://scholar.colorado.edu/asen_gradetds/82.

Council of Science Editors:

Jasper LEZ. Open-Loop Thrust Profile Development for Tethered Towing of Large Space Objects. [Doctoral Dissertation]. University of Colorado; 2014. Available from: https://scholar.colorado.edu/asen_gradetds/82

University of Colorado

6. Feldhacker, Juliana D. Incorporating Uncertainty into Spacecraft Mission and Trajectory Design.

Degree: PhD, Aerospace Engineering Sciences, 2016, University of Colorado

URL: https://scholar.colorado.edu/asen_gradetds/135

► The complex nature of many astrodynamic systems often leads to high computational costs or degraded accuracy in the analysis and design of spacecraft missions,… (more)

▼ The complex nature of many astrodynamic systems often leads to high computational costs or degraded accuracy in the analysis and design of spacecraft missions, and the incorporation of uncertainty into the trajectory optimization process often becomes intractable. This research applies mathematical modeling techniques to reduce computational cost and improve tractability for design, optimization, uncertainty quantification (UQ) and sensitivity analysis (SA) in astrodynamic systems and develops a method for trajectory optimization under uncertainty (OUU). This thesis demonstrates the use of surrogate regression models and polynomial chaos expansions for the purpose of design and UQ in the complex three-body system. Results are presented for the application of the models to the design of mid-field rendezvous maneuvers for spacecraft in three-body orbits. The models are shown to provide high accuracy with no a priori knowledge on the sample size required for convergence. Additionally, a method is developed for the direct incorporation of system uncertainties into the design process for the purpose of OUU and robust design; these methods are also applied to the rendezvous problem. It is shown that the models can be used for constrained optimization with orders of magnitude fewer samples than is required for a Monte Carlo approach to the same problem. Finally, this research considers an application for which regression models are not well-suited, namely UQ for the kinetic deflection of potentially hazardous asteroids under the assumptions of real asteroid shape models and uncertainties in the impact trajectory and the surface material properties of the asteroid, which produce a non-smooth system response. An alternate set of models is presented that enables analytic computation of the uncertainties in the imparted momentum from impact. Use of these models for a survey of asteroids allows conclusions to be drawn on the effects of an asteroid's shape on the ability to successfully divert the asteroid via kinetic impactor. Advisors/Committee Members: Brandon A. Jones, Alireza Doostan, Daniel Scheeres, Jeffrey Parker, Gregory Beylkin.

Subjects/Keywords: mission design; optimization under uncertainty; robust design; trajectory optimization; uncertainty quantification; Aerospace Engineering

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Feldhacker, J. D. (2016). Incorporating Uncertainty into Spacecraft Mission and Trajectory Design. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/135

Chicago Manual of Style (16^th Edition):

Feldhacker, Juliana D. “Incorporating Uncertainty into Spacecraft Mission and Trajectory Design.” 2016. Doctoral Dissertation, University of Colorado. Accessed February 28, 2021. https://scholar.colorado.edu/asen_gradetds/135.

MLA Handbook (7^th Edition):

Feldhacker, Juliana D. “Incorporating Uncertainty into Spacecraft Mission and Trajectory Design.” 2016. Web. 28 Feb 2021.

Vancouver:

Feldhacker JD. Incorporating Uncertainty into Spacecraft Mission and Trajectory Design. [Internet] [Doctoral dissertation]. University of Colorado; 2016. [cited 2021 Feb 28]. Available from: https://scholar.colorado.edu/asen_gradetds/135.

Council of Science Editors:

Feldhacker JD. Incorporating Uncertainty into Spacecraft Mission and Trajectory Design. [Doctoral Dissertation]. University of Colorado; 2016. Available from: https://scholar.colorado.edu/asen_gradetds/135

University of Colorado

7. Bezrouk, Collin J. Ballistic Capture into Lunar and Martian Distant Retrograde Orbits.

Degree: PhD, Aerospace Engineering Sciences, 2016, University of Colorado

URL: https://scholar.colorado.edu/asen_gradetds/147

► Distant retrograde orbits (DROs) are a neutrally stable class of three-body orbits. Because of their stability, DROs cannot be targeted with a low-energy transfer… (more)

▼ Distant retrograde orbits (DROs) are a neutrally stable class of three-body orbits. Because of their stability, DROs cannot be targeted with a low-energy transfer along a stable manifold like unstable three-body orbits in the circular restricted three-body problem (CR3BP). However, in more complicated dynamical models, the effects of small perturbing forces can be exploited to build ballistic capture trajectories (BCTs) into DROs. We develop a method for building sets of BCTs for a particular reference DRO with recommendations for minimizing computational effort. Sets of BCTs are generated in the Earth-Moon system and the Mars-Phobos system due to their applicability to near-term missions and large difference in mass parameters. These BCT sets are stochastically analyzed to determine the range of conditions necessary for using a BCT, such as energy, solar system geometry, and origin. The nature of the DRO after the spacecraft is captured is studied, including minor body flyby altitudes and variations in the size and shape over time. After a spacecraft has used a BCT, it can decrease its sensitivity to perturbations and extend its mission duration with a series of stabilizing maneuvers. Quasi-periodic orbits are constructed in the Earth-Moon CR3BP that lie on the boundary of stability, and closely resemble the DROs that result from using a BCT. Minimum cost transfers are then constructed between these quasi-periodic orbits and a target periodic DRO using a variety of methods for searching and optimizing. It is discovered that BCTs that target planar quasi-periodic DROs can be stabilized for about 15% of the cost of stabilizing a BCT with large out-of-plane motion. Once a spacecraft is in a stable DRO, the long duration evolution of that orbit is of interest. Using a high fidelity dynamical model and numerical precision techniques, the evolution of several DROs in the Earth-Moon system is studied over a period of 30,000 years. The perturbing forces that cause a DRO to transition into an unstable orbit are identified and analyzed. DROs larger than 60,000~km grow in amplitude due to solar gravity until they depart the Moon after several centuries. DROs smaller than 45,000~km remain stable for 25,000 years or more, but decay in size due to the Moon's solid tide bulge, which eventually causes the DRO to depart the Moon. The DROs evolve chaotically and occasionally experience periods of relatively fast amplitude growth when the period of the DRO is in resonance with the frequency of particular perturbing forces. Advisors/Committee Members: Jeffrey S. Parker, Daniel Scheeres, Daniel Kubitschek, Elizabeth Bradley, Daven Henze.

Subjects/Keywords: ballistic capture; distant retrograde orbit; low-energy; mission design; Phobos; weak stability boundary; Aerospace Engineering

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Bezrouk, C. J. (2016). Ballistic Capture into Lunar and Martian Distant Retrograde Orbits. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/147

Chicago Manual of Style (16^th Edition):

Bezrouk, Collin J. “Ballistic Capture into Lunar and Martian Distant Retrograde Orbits.” 2016. Doctoral Dissertation, University of Colorado. Accessed February 28, 2021. https://scholar.colorado.edu/asen_gradetds/147.

MLA Handbook (7^th Edition):

Bezrouk, Collin J. “Ballistic Capture into Lunar and Martian Distant Retrograde Orbits.” 2016. Web. 28 Feb 2021.

Vancouver:

Bezrouk CJ. Ballistic Capture into Lunar and Martian Distant Retrograde Orbits. [Internet] [Doctoral dissertation]. University of Colorado; 2016. [cited 2021 Feb 28]. Available from: https://scholar.colorado.edu/asen_gradetds/147.

Council of Science Editors:

Bezrouk CJ. Ballistic Capture into Lunar and Martian Distant Retrograde Orbits. [Doctoral Dissertation]. University of Colorado; 2016. Available from: https://scholar.colorado.edu/asen_gradetds/147

University of Colorado

8. Parsay, Khashayar. Invariant Solar Sail Formations in Elliptical Sun-Synchronous Orbits.

Degree: PhD, Aerospace Engineering Sciences, 2016, University of Colorado

URL: https://scholar.colorado.edu/asen_gradetds/155

► Current and past missions that study the Earth's geomagnetic tail require multiple spacecraft to fly in formation about a highly eccentric Keplerian reference orbit… (more)

▼ Current and past missions that study the Earth's geomagnetic tail require multiple spacecraft to fly in formation about a highly eccentric Keplerian reference orbit that has its apogee inside a predefined science region of interest. Because the geomagnetic tail is directed along the Sun-Earth line and therefore rotates annually, inertially fixed Keplerian orbits are only aligned with the geomagnetic tail once per year. This limitation reduces the duration of the science phase to less than a few months annually. Solar sails are capable of creating non-Keplerian, Sun-synchronous orbits that rotate with the geomagnetic tail. A solar sail flying in a Sun-synchronous orbit will have a continuous presence in the geomagnetic tail throughout the entire year, which significantly improves the in situ observations of the magnetosphere. To achieve a Sun-synchronous orbit, a solar sail is required to maintain a Sun-pointing attitude, which leads to the artificial precession of the orbit apse line in a Sun-synchronous manner, leaving the orbit apogee inside the science region of interest throughout entire the year. To study the spatial and temporal variations of plasma in the highly dynamic environment of the magnetosphere, multiple spacecraft must fly in a formation. The objective for this dissertation is to investigate the feasibility of solar sail formation flying in the Earth-centered, Sun-synchronous orbit regime. The focus of this effort is to enable formation flying for a group of solar sails that maintain a nominally fixed Sun-pointing attitude during formation flight, solely for the purpose of precessing their orbit apse lines Sun-synchronously. A fixed-attitude solar sail formation is motivated by the difficulties in the simultaneous control of orbit and attitude in flying solar sails. First, the secular rates of the orbital elements resulting from the effects of solar radiation pressure (SRP) are determined using averaging theory for a Sun-pointing attitude sail. These averaged rates are used to analytically derive the necessary conditions for a drift-free solar sail formation in Sun-synchronous orbits, assuming a fixed Sun-pointing orientation for each sail in formation. Next, the problem of formation design is solved using nonlinear programming for optimal two-craft, three-craft, and four-craft solar sail formations, in terms of formation quality and stability. Finally, the problem of formation establishment is addressed using optimal control theory, assuming that the sails are capable of making small changes to their orientations with respect to the Sun. These studies demonstrate the feasibility of solar sail formation flying for exploring the geomagnetic tail and improve upon previous work, which only considered unnatural relative motions that require continuous use of active control to remain in formation. Advisors/Committee Members: Hanspeter Schaub, Daniel Scheeres, Trevor Williams, Dale Lawrence, Webster Cash.

Subjects/Keywords: formation flying; magnetosphere; solar sail; sun-synchronous; Aerospace Engineering; Space Vehicles

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Parsay, K. (2016). Invariant Solar Sail Formations in Elliptical Sun-Synchronous Orbits. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/asen_gradetds/155

Chicago Manual of Style (16^th Edition):

Parsay, Khashayar. “Invariant Solar Sail Formations in Elliptical Sun-Synchronous Orbits.” 2016. Doctoral Dissertation, University of Colorado. Accessed February 28, 2021. https://scholar.colorado.edu/asen_gradetds/155.

MLA Handbook (7^th Edition):

Parsay, Khashayar. “Invariant Solar Sail Formations in Elliptical Sun-Synchronous Orbits.” 2016. Web. 28 Feb 2021.

Vancouver:

Parsay K. Invariant Solar Sail Formations in Elliptical Sun-Synchronous Orbits. [Internet] [Doctoral dissertation]. University of Colorado; 2016. [cited 2021 Feb 28]. Available from: https://scholar.colorado.edu/asen_gradetds/155.

Council of Science Editors:

Parsay K. Invariant Solar Sail Formations in Elliptical Sun-Synchronous Orbits. [Doctoral Dissertation]. University of Colorado; 2016. Available from: https://scholar.colorado.edu/asen_gradetds/155

University of Colorado

9. 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 · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th 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 (16^th Edition):

Geeraert, Jeroen L. “Multi-Satellite Orbit Determination Using Interferometric Observables with RF Localization Applications.” 2017. Doctoral Dissertation, University of Colorado. Accessed February 28, 2021. https://scholar.colorado.edu/asen_gradetds/192.

MLA Handbook (7^th Edition):

Geeraert, Jeroen L. “Multi-Satellite Orbit Determination Using Interferometric Observables with RF Localization Applications.” 2017. Web. 28 Feb 2021.

Vancouver:

Geeraert JL. Multi-Satellite Orbit Determination Using Interferometric Observables with RF Localization Applications. [Internet] [Doctoral dissertation]. University of Colorado; 2017. [cited 2021 Feb 28]. 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

10. Komendera, Erik. Precise Assembly of Truss Structures by Distributed Robots.

Degree: PhD, Computer Science, 2014, University of Colorado

URL: https://scholar.colorado.edu/csci_gradetds/91

► Assembly robots have been in operation in industry for decades, predictably repeating the same precise motions in closed workspaces to assemble products cheaply and… (more)

▼ Assembly robots have been in operation in industry for decades, predictably repeating the same precise motions in closed workspaces to assemble products cheaply and in mass quantities. However, in the field, robotic assembly has seen only spurts of progress, and no short-term feasible applications. NASA and the space industry desire robotic construction methods to remove the upper limit on size. Space telescopes are highly desired, but require structural precision on the order of microns. Previous approaches were ruled out because the precisely machined components were expensive, heavy, and prone to failure. The recent advent of cheap robotic swarms has revived interest in academia, but most research requires self-correcting, interlocking components, instead of commodity materials. In this thesis, I describe the Intelligent Precision Jigging paradigm, a solution to the problem of practical robotic assembly, with application to precision truss assembly. Intelligent Precision Jigging Robots (IPJRs) are robots that work in groups of three to incrementally assemble a structure. They set and hold distances with high precision, enabling coarse external manipulators to weld the commodity parts together and perform other tasks. To maximize the utility of the IPJR paradigm to the fullest extent, I present algorithms for finding near-optimal assembly sequences and for implementing Simultaneous Localization and Mapping (SLAM) to maintain an estimate of the assembly process through the accumulation of local strut length measurements. I define a model of truss assembly probability and a minimizing metric based on the covariance trace. I show that structure error grows cubically with node count. I present a three-step approach for generating near-optimal assembly sequences; commencing assembly on a central location of the structure, greedily assembling to minimize the covariance trace, and performing a local search on the space of sequences to swap steps until a local minimum is found. I show that this method consistently generates more precise sequences than any process alone. I then simulate the SLAM method with four different estimators commonly used in for SLAM; a least linear squares approach, the Extended Kalman Filter, the Unscented Kalman Filter, and the Maximum Likelihood Estimator. I show that when nonlinearity in the assembly process is dominant, the Maximum Likelihood Estimator is better than the other estimators, but for space telescopes with precision requirements, all four are functionally equivalent. I also show that when SLAM is used, the difference in covariance trace between sequences is reduced, reducing the need for finding globally optimal sequences. SLAM also mitigates the growth of structure error. Finally, I present the results of physical assembly trials on a telescope truss made of aluminum tubes, assembled by three IPJRs using two methods: an open loop approach, and an MLE-SLAM approach. I show that the MLE-SLAM assembly algorithm works even when the physical… Advisors/Committee Members: Nikolaus Correll, Sriram Sankaranarayanan, Tom Yeh, Eric Frew, Daniel Scheeres.

Subjects/Keywords: distributed robots; optimization; robotic assembly; simultaneous localization and mapping; space telescopes; truss structures; Artificial Intelligence and Robotics; Industrial Engineering; Robotics

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Komendera, E. (2014). Precise Assembly of Truss Structures by Distributed Robots. (Doctoral Dissertation). University of Colorado. Retrieved from https://scholar.colorado.edu/csci_gradetds/91

Chicago Manual of Style (16^th Edition):

Komendera, Erik. “Precise Assembly of Truss Structures by Distributed Robots.” 2014. Doctoral Dissertation, University of Colorado. Accessed February 28, 2021. https://scholar.colorado.edu/csci_gradetds/91.

MLA Handbook (7^th Edition):

Komendera, Erik. “Precise Assembly of Truss Structures by Distributed Robots.” 2014. Web. 28 Feb 2021.

Vancouver:

Komendera E. Precise Assembly of Truss Structures by Distributed Robots. [Internet] [Doctoral dissertation]. University of Colorado; 2014. [cited 2021 Feb 28]. Available from: https://scholar.colorado.edu/csci_gradetds/91.

Council of Science Editors:

Komendera E. Precise Assembly of Truss Structures by Distributed Robots. [Doctoral Dissertation]. University of Colorado; 2014. Available from: https://scholar.colorado.edu/csci_gradetds/91

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