The EXTREMA Simulation Hub: Advancements in the Development of an Integrated Hardware-In-the-loop Facility for Autonomous Cubesats GNC Technologies

The EXTREMA (Engineering Extremely Rare Events in Astrodynamics for Deep- Space Missions in Autonomy) is an ERC-funded project with the goal of enabling CubeSats with autonomous GNC capabilities. The project has received a Consolidator Grant from the European Research Council, a prestigious acknowledgment that funds cutting-edge and disruptive innovation research in Europe. EXTREMA aims to reach its goal by building on three pillars: Autonomous Navigation, Autonomous Guidance, and Autonomous Ballistic capture. Each pillar is associated with a hardware-supported experiment, and the research outcomes are channeled into the EXTREMA Simulation Hub (ESH), a facility in which autonomous algorithms and techniques are to be tested within an integrated hardware-in-the-loop simulation involving both on-board systems and testing support facilities. This work aims to present the advancements in the development of the ESH. In the first part, the progress in the development of the hardware facilities RETINA, an optical facility; ETHILE, a thrust test bench; and STASIS, a spacecraft attitude simulator are illustrated, focusing on the challenges and the adopted solutions. Then, the EXTREMA orbital propagator, SPESI, is presented. SPESI is a high-fidelity, stochastic numerical integrator whose task is to collect all the quantities of interest from the surrounding simulation environment and propagate the state of the simulated spacecraft, along with the associated uncertainties. To do so, SPESI is equipped with a real-time stochastic orbital propagator that guarantees the computation of the spacecraft state in a hard-real-time fashion, keeping the hardware-in-the-loop experiment synchronized. One of the major advancements in realizing the ESH environment is the development of the EXTREMA FlatSat. It consists of a hardware-software stack emulating a typical deep-space probe on-board computer. The software architecture of the EXTREMA FlatSat is described, focusing on the implementation of the flight software, developed with a modular approach in mind that enables quick integration of goal-specific applications and algorithms (such as the guidance optimization and the optical navigation ones) and fast deployment on multiple hardware architectures under a CI/CD framework. Furthermore, the workflow of the EXTREMA Dry Runs is presented. These represent periodic integration tests in which all the advancements carried on in parallel by different teams are integrated and tested on randomly generated mission scenarios. In this context, the EXTREMA Monitoring and Control Application (MoniCA) is also presented, together with the adopted inter-device communication framework. This unified and lightweight solution enables telemetry and status monitoring of all the devices involved in the simulation, enabling at the same time the streamlined development of a user-friendly web-based frontend for the comprehensive monitoring and control of the entire simulation. Eventually, the outcomes of the dry runs are analyzed for a set of significant interplanetary transfers, concluding with a discussion on the potential impacts of the proposed approach and with an outline of the future improvements and roadmap.