Computational Exploration of the Cislunar Region and Implications for Debris Mitigation

Abstract

For the investigation of the Earth's magnetosphere and the interplanetary space outside of it, satellites with orbits of large semi-major axis and large eccentricity are often used. While end-of-life (EOL) disposal options are well established for missions in low-Earth orbits (atmospheric decay) and the geosynchronous belt (near circular graveyard orbits), existing mitigation guidelines do not fully regulate the whole, useable circumterrestrial orbital space, such as these highly eccentric orbits (HEO) science missions; e.g., NASA's Eccentric Geophysical Observatory (EGO) and ESA's INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL). The collision risks posed by these LEO-GEO transiting spacecrafts has motivated both theoretical study and practical implementation of disposal options. The solution to the space debris problem, from LEO to GEO, can only be found by coupling a deep understanding of the circumterrestrial phase space with satellite mission analysis and design. For future missions, the EOL options have to be clearly identified in the early stages of mission design, taking into account orbital interactions and environmental evolution. This more holistic approach parallels that of ESA's Clean Space initiative, fostering innovative techniques and tools in orbital dynamics to novel spacecraft design to reduce both the space industry's environmental impact and mission costs. We emphasize here the new paradigm of the self-removal of satellites through dynamical instabilities caused by natural perturbation resonances (passive disposal) in the Earth-Moon-Sun system and discuss how lifetime estimates can be incorporated into launch window constraints to ensure the timely demise of satellites. Understanding the long-term dynamics of the satellite during the mission design phase will ensure that the missions develop predictably over both nominal and possibly extended timespans (without the need to make future significant orbital adjustments). Such dynamical assessments could have a profound and tangible influence on mission design, perhaps attacking the debris problem at its source. For the analysis of already orbiting satellites in this region, accurate orbit predictions are crucial to understanding the long-term dynamics of the satellite. Considering the chronic and significant lack of publicly available ``actionable'' observation data, researchers are generally forced to work with Two-Line-Elements (TLEs) as ``pseudo'' observations for orbit modeling and prediction. There have been many interesting approaches to the TLE-based-prediction problem over the past decade. Propagation based on these TLE-orbit-estimation methods have been carried out over month timespans at best; however, reasonably accurate orbit predictions based on TLEs over decadal timespans is unprecedented, especially for objects that are highly sensitive to initial conditions. To this end, we apply a new dynamically-inclined route to orbit prediction based on TLEs to obtain a statistically accurate initial conditions for orbit propagation of resonant orbits on decadal timespans.