Date of Award

9-2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Department of Aeronautics and Astronautics

First Advisor

Robert A. Bettinger, PhD

Abstract

The growing interest in the cislunar domain, which encompasses geosynchronous Earth orbit (GEO), the Moon, and the region where Earth-Moon gravitational effects are the primary influence, necessitates the development of tools to ensure safe and successful exploration. Space situational awareness (SSA) involves monitoring an environment to detect, track, identify, and catalog space objects. While most SSA experience comes from near-Earth operations, expanding into the cislunar domain presents significant challenges due to its vast expanse—greater than 10 times the radius of GEO—and the unique dynamics governed by the Circular Restricted Three-Body Problem (CR3BP) influenced by both Earth and Moon gravitational forces.
Despite limited missions and infrastructure dedicated to cislunar SSA, some studies have attempted to develop optimal satellite architectures for this purpose. However, existing research utilizing heuristic search methods lacks scalability and extensiveness. Specifically, they do not incorporate a comprehensive set of cislunar environment facets, such as a large periodic orbit catalog and sensor characteristics of observing satellites, nor do they apply to diverse scenarios including these scalability factors.
This study addresses these gaps by developing a new form for the chromosome in a hidden-genes Non-dominated Sorting Genetic Algorithm (NSGA-II), structured to accommodate categorical variables for orbit family and provide flexibility in incorporating diverse design criteria, including aperture diameter sensor characteristics. This scalable heuristic algorithm is evaluated in an extensive environment, utilizing a large periodic orbit catalog for sensor placement, various regions of interest for SSA, multiple sensor detection thresholds, and multiple metrics to evaluate performance, cost, and a proxy for station-keeping ability. Additionally, a pseudo-arclength continuation scheme was developed to expand the periodic orbit database, ensuring consistent path direction and allowing for smaller step sizes between orbits. This resulted in a more comprehensive collection of periodic orbits with finer resolution within each family containing over 1,000,000 orbits from 58 diverse families, allowing for a larger and more comprehensive set of locations for observer satellite placement in the heuristic.
The research demonstrates that the developed heuristic algorithm can serve as a comprehensive tool for developing near-optimal cislunar SSA architectures. It can be expanded to include additional design variables, performance metrics, possible observer satellite locations, and can test wide-ranging scenarios under varying detection thresholds while examining trade-offs on a Pareto front. Initial insights into beneficial traits of cislunar SSA architectures were gained from analyzing near-optimal solutions in the Pareto Front during the full-scale analysis. This newly developed form of the NSGA-II provides effective benefits for developing cislunar SSA architectures in a diverse problem set, enabling the creation of large design-space near-optimal solutions.

AFIT Designator

AFIT-ENY-DS-24-S-124

Comments

An embargo was observed for posting this dissertation on AFIT Scholar.

Approved for public release, PA Clearance Case AFRL-2025-5378, 03 Dec 2025.

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