Michael Klonowski, University of Colorado at Boulder; Casey Heidrich, University of Colorado at Boulder; Naomi Owens-Fahrner, BAE Systems, Inc.; Marcus Holzinger, University of Colorado at Boulder
Keywords: Space Domain Awareness, Cislunar Space, Mission Planning
Abstract:
With a volume of space three orders of magnitude greater than that in the near-Earth regime out to GEO, conducting space situational awareness (SSA) activities in Cislunar space will be exceedingly difficult. As shown throughout much of the work in Cislunar SSA research, multiple observers distributed throughout Cislunar space are needed to provide coverage to the vast regime. However, the character of this coverage can vary quite significantly depending on the layout and capabilities of observers in an architecture. Even more so, with electro-optical sensors, the distribution of detectable regions within Cislunar space are highly time dependent due to the need to capture reflected light from the sun. These complex time dependencies combine to create a rarely periodic, highly asymmetric, and dynamical environment for SSA.
In previous work, a multi-objective optimization algorithm was used to find Pareto-optimal placement of observers within Cislunar space that maximized coverage of a single trans-Lunar injection, as well as varying volumes of the region, while minimizing the total non-linear cost of the architecture [1]. Further work in this vein expanded the objective space to include the total control effort a cooperative agent would need to expend to reach L1 or an insertion point into an L2 Lyapunov orbit while maximizing its visibility to an architecture [2]. Work such as [3] explore metrics for analyzing how well various observers in Cislunar space contribute to numerical observability, within the context of orbit determination and tracking. Results from these works display the breadth of the multi-objective trade space in the architecture design problem, and reinforce the numerous complexities that must be considered throughout all steps of Cislunar SSA.
While a significant amount of work has been focused on exploring the design space of the architecture design problem and the analysis of various Cislunar SSA metrics, little is discussed from the perspective of methodologies for SSA prioritized mission design. Future missions such as human space flight within Cislunar space may require near persistent detection of assets from a distributed SSA architecture in the region. Inevitably, a Cislunar SSA architecture will have a direct impact on how mission designers and operators behave in space. With such significant possible variations in architecture performance and coverage across years, months, and even days, there is a necessity for tools that can be applied to any such architecture to aid in mission planning through Cislunar space.
In this work, we use insights from [2] to develop a robust methodology for analyzing the dynamics of varying detectable regions of Cislunar space given any arbitrary architecture. Within the volume-oriented architecture design simulation environment from [1], we obtain a 3-dimensional grid of volume points within Cislunar space. At each time step within the simulation, each volume point is marked as either detectable by an architecture or not detectable. By connecting nearby detectable points across time in this 4-dimensional space, we can find approximate corridors of persistent detection by an architecture through Cislunar space. This space is easily and intuitively represented as a directed graph, with nodes representing detectable points sampled within Cislunar space in at specific times. Nodes are then connected to other nearby nodes at different times with edges. A graph-theoretic path finding algorithm is employed within this large graph to reveal unique routes between predefined initial and final conditions. With many such paths likely to be infeasible within the CR3BP dynamics, further refinement of these paths is conducted by enforcing transcription constraints between nodes, similar to those implemented in [4]. The resultant paths represent persistent detection corridors (PDCs), defined at specific epochs for a particular Cislunar SSA architecture. The existence of PDCs may also be crucial for the analysis of potential lines of commerce within Cislunar space. Ideally, a spacecraft traveling along a PDC will experience persistent, unbroken coverage from the architecture; in reality this may not be exactly the case. Further exploration of these methodologies will include studying minimum detectability thresholds along PDCs in the context of numerical observability as well as studying the inherent time dependencies governing the existence of PDCs.
References
[1] Klonowski,M.,Holzinger,M.J.,andFahrner,N.O.,“OptimalCislunarArchitectureDesignUsingMonteCarloTreeSearch Methods,” The Journal of the Astronautical Sciences, Vol. 70, No. 3, 2023, p. 17.
[2] Klonowski,M.,Fahrner,N.,Heidrich,C.,andHolzinger,M.,“RobustCislunarArchitectureDesignOptimizationforCooperative Agents,” Proceedings of the Advanced Maui Optical and Space Surveillance (AMOS) Technologies Conference, 2023, p. 15.
[3] Fowler, E. E., and Paley, D. A., “Observability metrics for space-based cislunar domain awareness,” The Journal of the Astronautical Sciences, Vol. 70, No. 2, 2023, p. 10.
[4] Heidrich,C.,andHolzinger,M.,“UniversalAngles-OnlyCislunarOrbitDeterminationUsingSparseCollocation,”Proceedings of the Advanced Maui Optical and Space Surveillance (AMOS) Technologies Conference, 2023, p. 17.
Date of Conference: September 17-20, 2024
Track: Cislunar SDA