Joshua Wysack, BAE Systems
Keywords: cislunar, SDA, STM, lunar, Moon, end-of-life, disposal
Abstract:
The lack of a binding Earth-orbit end-of-life (EOL) policy in the early stages of spaceflight resulted in many objects that will remain in Earth orbit for centuries or perpetually. These objects pose a collision threat that may result in a debris cloud that could be crippling to active missions and the services that rely on those missions. In 2001 the Orbital Debris Mitigation Standard Practices (ODMSP) were established to address spacecraft EOL disposal for Earth-orbiting missions. A robust policy is lacking for missions in cislunar space. This could lead to future risk to lunar human spaceflight missions and the growing number of missions going to the Moon and other cislunar orbits.
Despite the vastness of cislunar space, several areas are certain to become more congested with spaceflight traffic as countries and private enterprise continue the push to the Moon and surrounding space. These include regions near the Moon and the five Lagrange points, particularly L1 and L2. Past lunar missions have taken various approaches. LCROSS, LADEE, and Beresheet were purposely crashed into the Moon at the end of mission. Peregrine had the forethought to use a planned Earth flyby to safely deorbit their spacecraft after a failure prevented the successful completion of the mission to land on the Moon. These few and far between examples may not be part of a standard EOL strategy or policy, but we will examine their execution and success as part of this work.
In this paper, we examine several EOL options for cislunar missions – both good and bad strategies. This involves evaluation of the risk to cislunar spaceflight as well as potential harm to future lunar surface infrastructure. Candidate EOL strategies include,
• Leave Earth-Moon system permanently (might be a heliocentric orbit)
• Transition to a ‘safe’ orbit that ensures no collision for a specified number of years (similar to the GEO graveyard)
• Controlled re-entry into Earth’s atmosphere
• Crash into the lunar surface, both controlled and uncontrolled
Many factors contribute to the selection of an EOL strategy. The choice is influenced by the present orbit and its stability, the maneuver capability of the spacecraft, and the long-term collision risk. These and other pertinent factors will be evaluated in the paper.
Monte Carlo simulations will be used to assess requirements on position knowledge and maneuver accuracy in the execution of an EOL strategy. These may become important in maneuvering to orbits that are deemed to be safe for long-term disposal. High-fidelity propagation will be used in order to represent realistic dynamics as well as possible.
Finally, we will discuss implications for future lunar and cislunar missions and how our work may guide future space policy. This will start with a survey of current policy and guidelines. An example is The Policy on Planetary Protection from the Committee on Space Research (COSPAR), which provides guidelines on lunar impacts.
The safety of future space missions, lunar infrastructure, and lunar natural resources will be dependent upon the mission design choices that are made in the coming decades. Without clear guidance and strategies on EOL disposal it will be up to each individual operator to make smart choices for the greater good of the cislunar space environment. A thorough examination of the various strategies and the best choices will aid policy makers in putting forth clear guidance.
Date of Conference: September 17-20, 2024
Track: Space Debris