Autonomous Navigation Using LiAISON in the Earth-Moon System

ECF16 - "Developing Principles for Effective Human Collaboration with Free-Flying Robots", impact on Astrobee work.

This research aimed to advance the understanding of LiAISON navigation and its application for increased spacecraft autonomy for crewed missions in the Earth-Moon system while evaluating its costs (e.g., dedicated navigation satellite, additional hardware, etc.) and benefits (e.g. improved navigation accuracy, fewer DSN tracks, etc.) ultimately providing information for future mission planners to determine its applicability. A baseline navigation capability utilizing ARTEMIS tracking data was conducted for use in subsequent simulations in the research. A large trade space was explored analyzing the navigation capabilities of LiAISON supplemented tracking data for crewed mission in Earth-Moon halo orbits, low lunar orbit, and trans-lunar cruise. An analysis of raw tracking data for the ARTEMIS mission was conducted to establish a baseline for navigation performance capabilities with current ground station configurations. Since ARTEMIS was the first mission to fly an Earth-Moon libration point orbit, it's navigation capabilities and operations experiences provide an invaluable measure of what is to be expected. The work performed in this thesis systematically investigated techniques not used in operations to obtain the best navigation performance capabilities attainable. Significant findings include the necessity of a more complex solar radiation pressure shape model of the spacecraft, sequential estimation as opposed to batch processing, estimation of maneuvers and extended tracking data arc lengths. By properly editing tracking data residuals and extending the data arc length, it was shown that overlap precisions on the order of 150 m or less in position was possible. The most important aspect of longer data arcs is the reduction of uncertainty or increased precision in the velocity estimates of the spacecraft. With a longer data arc it is possible to achieve velocity uncertainties less than 1 mm/sec, whereas a shorter data arc as used in operations only provides uncertainties on the order of 5 mm/sec. Initial observability work discussing the capabilities of LiAISON data types was limited in scope however it did explore some features relating to the environment that allows LiAISON to use relative radiometric data to obtain absolute state estimates. An extension to this work is covered in this dissertation in which an exploration of the information content of range and Doppler using simplified first-order models was conducted. The Earth-Moon system was mapped out using partial derivatives of the relative acceleration between a spacecraft and the libration points to define regions where LiAISON Doppler data provides limited ranging information necessary to obtain full estimates of the spacecraft’s state. An extension of the local stability characteristics of halo orbits and how they related to the uncertainty propagation was examined. It was shown that the stability is directly related to the stretching and alignment of the uncertainty propagated along a halo orbit. A crewed vehicle disturbance and environment model (FLAK) was derived using data describing the expected crew ECLSS system. An introduction to a Poisson counting process for use with FLAK uncertainty propagation was derived using linearized assumptions. A Monte Carlo analysis of a trajectory undergoing FLAK showed that a linearized assumption of the uncertainty propagation was valid over the timeframe of concern between the end of a tracking data arc and the next performed maneuver. The inclusion of a Poisson noise model intuitively makes sense for modeling FLAK and requires minimal modifications to current navigation software to implement. Surveys of the trade space concerning LiAISON supplemented navigation for Earth-Moon halo orbiters, low lunar orbiters, and trans-lunar cruise trajectories was conducted. For lunar halo orbiters, TDRSS/GEO type LiAISON measurements can significantly improve the navigation capabilities of both the TDRSS/GEO satellite and a spacecraft in orbit about one of the Earth-Moon Lagrange points. There exists regions where the observability and information content of the data is reduced to due repetitious sampling of the same regions, specifically with a periodicity of 22 hours. An extension to LiAISON navigation of two spacecraft in lunar halo orbits, where one is a crewed vehicle, was conducted. It was shown that LiAISON alone is not sufficient to accurately determine the trajectories of both the navigation satellite and crewed vehicle. However, the addition of a dedicated LiAISON navigation satellite supplementing existing ground tracking networks significantly improves the navigation performance of a crewed vehicle. LiAISON supplementing the DSN produces similar navigation uncertainties as the proposed six station IDAC4B configuration. Similar results were seen for both a crewed vehicle in low lunar orbit and a crewed vehicle on a trans-lunar cruise trajectory. DSN and LiAISON performs on par with the IDAC4B configuration, while LiAISON supplementing the IDAC4B configuration produces the best navigation performance typically invariant of the level of FLAK experienced by the crewed vehicle.