Risk modeling and analysis methodologies for reentry and conjunction of space objects

Abstract

The recent growth of the space industry and the resulting increase in the number of space objects in the Earth orbit are leading to a direct increase in space risk, including reentry and conjunction. The risk posed by space objects directly or indirectly damages the public as well as satellite operators but is still an unfamiliar concept compared to other disasters. In order to expand awareness and effective communication, a study on risk evaluation methodology that considers the systemic risk characteristics of space object risk in needed. This thesis proposes a systematic analysis procedure and risk assessment methodology for analyzing the risk of reentry and conjunction of space objects. The proposed procedure for reentry assessment comprises three phases encompassing the whole reentry stages of space objects. Mathematical models for assessing the impact risk of reentering space objects by utilizing the information available during different risk management phases and the recommended risk analysis results for effective communication are presented. The concept of the conditional casualty expectation is proposed as the metric representing the reentry risk, and the method to compute its profile is introduced. A case study on the risk management procedure with the dataset on an actual reentry event is conducted to demonstrate the efficacy of the proposed procedure. A single index for collision risk that comprehensively considers the geometry between objects, the uncertainty of information and the sustainability of the outer space environment is proposed. The methodologies for modeling and evaluating the contamination of the orbital environment by debris from the collision were analyzed, and case studies on the low Earth orbit objects were conducted.