Isoletta, Giorgio (2023) Advanced astrodynamics models and approaches for Space Surveillance and Exploration. [Tesi di dottorato]

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The main objective of this PhD activity is the development of innovative astrodynamics techniques to enable advanced functionalities for a wide range of applications in the space domain. In this respect, two different research areas have been addressed, one related to the development of algorithms to support Space Surveillance and Tracking (SST) services, the other related to the space exploration domain, and, in particular to investigating the potential of aerocapture maneuvering for future Mars missions. As different as these applications could seem, the activity has the general purpose to provide tools and algorithms to deal with astrodynamics problems. In the SST context, operations involving detection and monitoring of space objects as well as avoidance of possible collision between them require the accurate knowledge of the objects’ position over time, achievable only by means of numerical propagators when frequent enough measurements from ground-/space-based sensors are not available. Indeed, a fully configurable numerical orbit propagation tool is presented here, which includes the main Earth orbital perturbation and exploits an high-order Runge-Kutta scheme to solve the perturbed equations of motion. The developed propagator is conceived to be easily coupled to other algorithms to support various SST tasks. In this perspective, the main contribution of this thesis is the development and performance assessment of an innovative approach to evaluate the medium-term collision frequency for space objects in LEO, taking the propagation uncertainties into account. At the same time, a novel algorithm is also proposed to estimate the position errors coming from environmental and object-related uncertainties, based on relative motion equations. Furthermore, the modularity of the proposed orbital propagation environment makes it a useful tool to support other SST applications. To demonstrate this point, the propagator is integrated within algorithmic architectures to perform calibration of ground-based sensors and to carry out coverage analysis of satellites over areas of interest to support sensor tasking and Recognized Space Picture activities respectively. As regards the Space Exploration context, the research activity focused on the investigation of the feasibility of Mars aerocapture for small satellites exploiting the adaptable aperture of a particular deployable drag device. The study, which has been carried out first for a simplified 2D scenario and then for a complete 3D Mars mission, aims at understanding the conditions leading to successful aerocapture and at assessing the impact of the main uncertainties on its success.

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