CNES tools and methods for de-orbit and re-entry trajectories evaluation
Creators: name:  J. GOESTER 
name:   A. BELLUCCI 
name:   C. FREMEAUX 
Publisher: name: Proceedings of  the 9th European Conference for Aerospace Sciences. Lille, France, 27 June - 1 July, 2022
Year: 2022
Subjects: SPACE DEBRIS MODELING
REENTRY

description: As French National Space Agency and in the frame of the French Space Operations Act, CNES needs efficient state-of-the-art tools for evaluating risks related to space operations. But as CNES is also responsible of its own satellites operations, it has to determine which de-orbit and re-entry strategies will be used to respect the French law. The first set of tools corresponds to the ones used to foresee short, medium or long-term orbit evolutions that could lead to re-entry on the Earth. Depending of this time horizon and of the available inputs, three different software are available. The first one is PSIMU for numerical propagations so mainly used for short ones (typically some days). It may take into account many orbital perturbations as well as maneuvers and attitude motion and thus get a relative precise prediction of the trajectory. The second one, OPERA is used for some months propagations processing filtering on a set of initial TLE (Two Line Elements). This tool is currently used in CNES operational procedures to predict potentially risked upcoming re-entries. At last, STELA is the CNES reference tool for long-term semi analytical propagations. It allows determining if the mission complies with a 25 years duration for LEO orbits or 100 years for geostationary cemetery orbits. Note that these three tools are freely available, downloading them via a dedicated CNES web site. The second set of tools is devoted to de-orbit sequences of maneuvers computation. The oldest one, DOORS, deals with classical de-orbit strategies leading to an atmospheric re-entry and impacts on a safe zone as the SPOUA (South Pacific Ocean Uninhabited Area). We will see an overview of the current functionalities of this tool which will be used for the next SWOT mission but was previously used during the five ATV missions and for other de-orbit strategies as for the ASTRA-1K de-orbit twenty years ago! A more recent tool, SIRENA, is in charge of strategies that are more complex related to Assisted Natural Reentries. These strategies consist in executing maneuvers during several weeks or months to target specific reentry ground tracks in order to minimize the risk for ground populations. It has been recently deployed in an operational context during an end-of-life experiment. Unfortunately, due to their criticality, these tools cannot be shared outside CNES. At last, DEBRISK and ELECTRA are both tools to evaluate more precisely the ground population risk. The new DEBRISK methodology associated to dynamics and aerothermal equations considering ablation allows determining how many debris will still be alive and what will be their characteristics when touching the ground. Then, ELECTRA takes in consideration this list of debris as well as many other dispersed parameters to compute, via Monte Carlo simulations, numerous trajectories. It evaluates a final risk considering failures during the last re-entry manoeuver but also risk in case of natural re-entry if a failure occurs before the last-burn (during the mission or during the first re-entry manoeuvers).Both of them being are weighted by their probability of occurrence. Note that ELECTRA is also operationally used for computation of the risk in case of a failure during each launch from the Kourou launch site (CSG). Both tools are available for CNES external users but their use is strictly limited in the frame of the FSOA.