Interplanetary space represents the ultimate frontier of human exploration, with many scientific and commercial missions planned to launch in the near future. The increasing number of missions aiming to go beyond Earth reflects a growing interest of the industry towards cislunar space, libration point orbits and other regions of the Solar System.
Nonetheless, deep space represents a challenging environment, where chaotic dynamics, longer distances and larger time scales make trajectories more unpredictable, compared to near-Earth applications. The chaotic nature of interplanetary trajectories introduces the risk of objects returning to Earth at super orbital speeds, posing a threat for collisions with active Earth-orbiting satellites and surface impacts. The modeling and characterization of such events is challenging, due to the lack of regulations and commonly agreed-upon tools for debris mitigation and re-entry assessment of interplanetary return trajectories.
This work focuses on the design and implementation of an integrated tool for debris mitigation compliance assessments associated with interplanetary return trajectories. To compensate for the chaotic nature of the trajectories studied, the work employs a statistical approach, based on a Monte Carlo analysis, to reliably assess the risk associated with the mission.
The integrated tool aims at tackling all aspects associated with collision and re-entry risk assessment, including trajectory propagation, collision risk assessment, re-entry fragmentation modelling and casualty risk assessment. Additionally, to evaluate its performance in real-use applications scenarios, the tool has the capability to simulate a cataloguing system, reliant on measurements simulations and orbit determination analysis.
The Monte Carlo approach relies on the generation of a large number of samples from a set of initial conditions and uncertainty parameters. To propagate all these samples efficiently, the work employs a combination of state-of-the-art pre-existing ESA-developed tools: GODOT and CUDAjectory. Visibility events and observations from user-defined sensor networks can be simulated and used in an orbit determination process. This allows to retrieve ephemeris with covariance information, thus completing a full catalogue chain process for objects beyond Earth orbit. These results can then be evaluated to assess the cataloguing capabilities.
To assess the compliance with mitigation guidelines, the collision risk in the protected regions has been studied. As common collision tools were not designed with the aim to analyze hyperbolic orbits and fly-bys, the developed tool uses a flux-based approach by discretizing the protected regions into a spherical grid to calculate the probability of one or more collisions for each cell passage. Although following the general methodology of ESA’s MASTER tool, the module only makes use of the future object population to avoid the limitations of hyperbolic trajectories.
Finally, to evaluate on-ground casualty risk, the tool employs ESA’s DRAMA/SARA tool, to model re-entry and fragmentation in the atmosphere, and to evaluate the impact risk associated with the surviving fragments.
This paper presents the results obtained from the application of the integrated tool to three different mission scenarios: a heliocentric orbit, a libration point orbit and a cislunar mission, represented by the JUICE upper stage, the GAIA spacecraft and a Gateway service module (Orion) respectively.