Increasing Access and Capabilities of CubeSats for Investigation of Earth Trojan Asteroids

Thesis (Ph.D.)--University of Washington, 2020This thesis develops the requirements of a low-cost spacecraft mission to the Sun-Earth Lagrange point L4 and L5 to search for Earth Trojan asteroids, and develops and demonstrates a specialized communication system needed to facilitate such a mission. Asteroids serve as time capsules into the historical past of our solar system, and have been critical components to our understanding of the formation and evolution of our solar system. A subset of Earth co-orbital asteroids, Earth Trojans, being close to our home can help us understand things like the conditions present during Earth’s initial formation or the Moon-Earth formation impact theory. Considering there is only one identified Earth Trojan asteroid, 2010 TK7, and the fact that numerical analysis and additional searches support a population of at least one hundred Trojans, a dedicated mission is well warranted. With the Earth Trojan asteroid regions particularly difficult to view when using Earth-based telescopes, an alternative approach is described herein: send a small low-cost spacecraft, called a CubeSat, directly to these regions for in-situ imaging. CubeSats present a paradigm shift in spacecraft development and are beginning to offer a new low-cost and highly accessible regime to Earth and space science. CubeSats are small, typically 1-10L and 1-10kg, and leverage the recent miniaturization of smartphones and their related technologies. The result is that in the past 10 years CubeSats have proven themselves to be invaluable for carrying out Earth-based science missions at a fraction of the cost using traditional methods. And more recently CubeSats have begun to leave Earth orbit, such as providing an auxiliary communication relay role on the latest NASA Mars mission. With ever increasing fiscal pressures limiting the development of planetary probes, developments herein lay the groundwork for an Earth Trojan prospecting mission costing less than $500,000. This mission is facilitated by the developments of a compact communication system described in this thesis that includes: (1) low-cost application of high-gain reflectarray antenna technology to the CubeSat form factor, and (2) low-cost and low-risk design technique development of radio frequency circuitry needed to interface with the antenna. Furthermore, development of a CubeSat demonstrator mission was undertaken, called the HuskySat-1, providing proof of concept implementations of these technologies as well as additional technological innovations required to support a deep space mission to the Earth Trojans. The HuskySat-1 successfully deployed into a low-Earth orbit on January 31, 2020 with operational success