EXTREMA builds on three Pillars. On top of the three pillars lies the EXTREMA Simulation Hub, where the outcome of the pillars is merged to perform integrated simulations.
In Pillar 1 (Autonomous Navigation), we developed and completed an end-to-end autonomous vision-based navigation pipeline for deep-space missions, spanning image processing, attitude determination, and full state estimation. The navigation chain was implemented and executed on representative space-grade processors. To support validation activities, a high-fidelity space rendering engine was developed for both software-in-the-loop and hardware-in-the-loop simulations, enabling accurate modeling of the camera and imaging chain in SIL and the stimulation of real sensors in HIL with geometric and radiometric consistency representative of on-orbit conditions.
In Pillar 2 (Autonomous Guidance), an autonomous closed-loop guidance approach is developed to achieve the mission target by repeatedly recalculating the optimal trajectory to compensate for thrust execution errors, navigation errors, and model approximations. In particular, the core of the guidance algorithm is based on successive convex programming. This algorithm has been developed by paying particular attention to the computational burden, in order to make it not only deployable but also executable aboard. It is integrated into the simulation framework in a plug-and-play fashion, enabling easy testing of alternative approaches, such as the indirect algorithm.
In Pillar 3 (Ballistic Capture), we characterized ballistic capture corridors, studying their peculiarities and understanding their potential exploitation as pathways guaranteeing temporary capture at major planets for autonomous, deep-space CubeSats. We devised an autonomous ballistic capture algorithm for the inexpensive synthesis of ballistic capture corridors. The algorithm was made compatible with limited-capability, autonomous, interplanetary CubeSats. Pre-computed ballistic capture sets at Mars at different epochs are publicly available on Zenodo.
For what concerns the ESH, we have developed the building blocks, namely SPESI, STASIS, and the flatsat OBC. SPESI is the Space Environment Simulator, which takes care of the spacecraft-environment simulation and represents the simulation authority. STASIS is the SpacecrafT Attitude Simulation System, which is used to simulate the spacecraft attitude dynamics and control. The platform’s attitude control is provided by a bespoke suite of actuators, consisting of four reaction wheels in a pyramidal configuration. Each unit integrates a BLDC motor with a custom-designed PCB for motor driving and logic control, paired with a prototyped flywheel engineered for specific torque profiles. The system is managed by a dedicated ADCU, which fuses optical and inertial data via a Kalman Filter to execute the control laws and synchronize the actuator response with the satellite state machine. The flatsat On-Board Computer (OBC) was developed in terms of both software and hardware; it controls the pillars experiments and represents the spacecraft authority.
