Real-time onboard orbit propagator for planetary missions

Developing autonomous navigation systems for orbital platforms represents a frontier challenge in solar system exploration. A crucial element of such systems is the orbital propagator, which must accurately predict the spacecraft trajectory. Over short time scales, accurate state propagation is essential for processing data from onboard sensors within a sequential filter, ensuring consistent state updates and preventing filter divergence. Over extended time spans, the capability to accurately propagate the spacecraft trajectory could enhance onboard autonomy, enabling tasks like planning orbit correction maneuvers or supporting on-orbit servicing. This paper presents an orbital propagation scheme tailored for planetary and close-proximity scenarios, achieving high accuracy through comprehensive modeling of gravitational and non-conservative forces. While high-sensitivity scientific payloads, such as accelerometers, can measure small non-conservative perturbations, their high costs and the need for offline calibration to mitigate noise and spurious signals limit their real-time applicability. Instead, the proposed propagator integrates these perturbations through mathematical modeling, ensuring robust and cost-effective trajectory predictions for extended durations. A software-in-the-loop testing and validation campaign, focused on mission scenarios around the Moon and Mars, demonstrates the propagator's compliance with accuracy and performance requirements for autonomous orbit determination and control. These results validate the scheme's applicability for future exploration missions requiring minimal ground-based support.