An Evaluation of Vertical Orbits for a Cislunar Space Situational Awareness Constellation
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chen-jeremy02-sm-aeroastro-2026-thesis.pdf
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Author(s)
Chen, Jeremy N.
Advisor(s)
Evans, Eric D.
Date Issued
May 2026
Publisher
Massachusetts Institute of Technology
Abstract
As interest in missions to and from the Moon increases, there exists a unique opportunity to build surveillance systems in cislunar space able to detect and track spacecraft at a rate commensurate with the rate of growth in activity. Many missions plan to exploit the orbital dynamics of the Earth-Moon system in specific regimes, creating areas of high traffic for future operations. This thesis looks at a theoretical space situational awareness constellation that uses vertical orbits, which see very little discussion in terms of future operations. By occupying these low-traffic orbital regimes, an effective cislunar space situational awareness constellation could be created to monitor traffic near, to, and from the Moon.
This research uses simulations in MATLAB based off the Circular Restricted Three-Body Problem to model the orbits and lighting conditions of a set of defined target spacecraft meant to be representative of future missions. A Monte Carlo analysis across 7,500 configurations evaluated observer constellations of 2, 4, and 8 spacecraft distributed across one L1 and one L2 vertical orbit over a 28-day period. Performance was assessed using mean custody
fraction and target availability metrics based on line-of-sight geometry, sensor washout due to solar/lunar exclusion, and optical detectability.
An 8-observer constellation achieved 99.38% mean custody and 99.31% target availability - in other words, 99.38% of the targets were detectable 99.31% of the time. Key findings show L1 and L2 observers exhibit complementary performance, as performance degradation at opposite times mean that gaps in one observer are covered by the other. Optimal configurations allow for one orbit to cover a majority of targets and the other to capture edge cases. Results demonstrate vertical orbits are operationally viable for cislunar space situational awareness and identify design principles for future constellation development.
MIT Department
Massachusetts Institute of Technology. Department of Aeronautics and Astronautics
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