Master of Science (MS), Ohio University, 2021, Electrical Engineering (Engineering and Technology)

Over the coming decades, as the volume of space missions continues to grow and iversify, so too does the demand for methods to achieve improved position, navigation, and timing service performance in geostationary orbit and beyond. For high-altitude spacecraft to utilize GNSS navigation techniques, it is required that they must utilize signals from GNSS space vehicles from across the limb of the Earth, which severely limits the quality and quantity of measurements that can be made. The performance potential for such a spacecraft can be improved, however, by having the ability to utilize any combination of satellites visible at a given time, across all GNSS constellations. Interoperability of this kind depends primarily on the ability to resolve the differences in each system's specific time scale. This thesis proposes and develops methods to provide high-accuracy GNSS measurements from a GNSS receiver in low Earth orbit to facilitate the estimation of GNSS inter-constellation timing offsets. The Bobcat-1 CubeSat was developed to support the collection of this data, and this thesis describes the capabilities and measurement accuracy achieved by the CubeSat as well as the post-processing performed to produce precise inter- constellation timing offsets. Furthermore, a study was conducted using a simulation that was developed to evaluate the performance impacts that GNSS system time offsets impose on a user in geostationary orbit. This study produces quality of service benchmarks that are used to provide performance targets for the accuracy of the inter-constellation time offset estimates enabled by data from Bobcat-1. This thesis compares the inter-constellation timing offset estimates achieved by these methods against the Galileo-to-GPS time offset that is produced by the Galileo Control Segment and included within the navigation messages of Galileo space vehicles.

Committee: Sabrina Ugazio (Advisor); Frank Van Graas (Committee Member); Chad Mourning (Committee Member); Nathaniel Szewczyk (Committee Member) Subjects: Aerospace Engineering; Electrical Engineering

Bachelor of Arts, Wittenberg University, 2009, Philosophy

In 1962 Thomas Kuhn argued that scientific revolutions occur through paradigm change.That is, the model for the way we understand the world is completely replaced by a new incompatible model. He also claimed that these revolutions are non-cumulative, and thus there is actual incommensurability between the paradigms. However, by stating the process of revolution in such an exaggerated manner in order to highlight the non-cumulative nature of paradigm change, Kuhn precludes the possibility of revolution through debate. I argue that a close examination of the works of Francis Bacon as well as a scrutiny of Galileo and Priestley reveal genuine areas of rationally adjudicable, commensurable agreement. Furthermore, I posit a process, based on the ideas of Willard Von Orman Quine, whereby we might actually affect revolution, in whole or in part, through the process of debate.

Committee: Nancy McHugh PhD (Advisor); Don Reed PhD (Committee Member); Ty Buckman PhD (Committee Member) Subjects: Philosophy

Master of Science (MS), Ohio University, 2008, Electrical Engineering (Engineering and Technology)

This thesis investigates several design approaches that can be employed in a Multi-frequency GNSS Receiver RF front-end for various applications. With the prospect of Galileo and GPS interoperability in the near future, many new avenues for research into the development of multi-frequency receivers have been opened. This thesis concentrates on the design of the front-end of the receiver with the assumption that the signal processing will be done in software (i.e. for a software defined radio approach). Various methods of sampling data are discussed. The software design tool Ansoft Designer® has been used to implement four design approaches that were investigated for RF front-end implementation. Each of the design approaches work with a subset of all the GPS/Galileo signals thus making that particular design approach suitable for particular applications. The various design approaches have been analyzed using Ansoft Designer® and the results are presented for the four design approaches.

Committee: Chris G. Bartone Ph.D (Advisor); David Matolak Ph.D (Committee Member); Trent Skidmore Ph.D (Committee Member); William Kaufman Ph.D (Committee Member); Sanjeev Gunawardena Ph.D (Other) Subjects: Engineering

BA, Oberlin College, 2008, English

My Honors thesis, An Infinity of Questions, explores the performance of science on stage using two plays: The Life of Galileo, challenging the status quo, by Bertolt Brecht and Copenhagen, examining the origins of intention, by Michael Frayn. I focus on these two plays because not only because they impress me personally, but both spring from historical events and are thematically concerned with physics and the atomic bomb. They also make an interesting juxtaposition since Galileo has a decidedly political agenda, while Copenhagen is a philosophic inquiry. I argue that these dramas are exceptional science plays because of how they literally enact the ideas that they examine and bring science to life on stage by means of modeling ideas.

Committee: Carol Tufts (Advisor); Phyllis Gorfain (Committee Member); Matthew Wright (Committee Member) Subjects: Astronomy; Atoms and Subatomic Particles; English literature; History; Nuclear Physics; Personal Relationships; Philosophy; Physics; Science History; Theater