Samuel Wishnek, Ball Aerospace; Joshua Wysack, Ball Aerospace; Jeremy Correa, Ball Aerospace
Keywords: Cislunar SDA, Cislunar STM, orbit maintenance, maneuver planning
Abstract:
With the increase of planned activity in the cislunar and lunar space environments, there is a need for mature mission designs that include realistic orbit maintenance budgets. The Earth-Moon Lagrange point L1 is an advantageous location for many mission areas, including Space Domain Awareness (SDA), Space Traffic Management (STM), communication, Position, Navigation, & Timing (PNT), etc. Orbits near L1 provide an excellent vantage point to view objects on Earth-Moon return/depart missions and in lunar orbit, which is particularly favorable for SDA and STM.
Many orbits at L1 have long eclipse durations due to both the Earth and the Moon. Earth eclipses can last up to 6 hours, while Moon eclipses can last up to 15 hours. For thermal and power reasons, these eclipse durations are not acceptable for many missions. In this paper, we explore optimal maneuver strategies to mitigate these lengthy shadow times. Strategies include placement of maneuvers in position and time that use minimal fuel while trying to reduce the perturbation to the orbit.
Orbit selection plays an important role as families of orbits experience different eclipse durations as a result of satellite-Earth-Moon-Sun geometry as well as orbit size and energy. Orbits in the L1 regime do not remain stable under high-fidelity propagation, so a robust stationkeeping strategy is required. This paper presents realistic stationkeeping and eclipse mitigation strategies for various orbits around L1.
Families of periodic Lagrange point orbits exist that can be classified by their distinct orbital characteristics. A major distinguishing characteristic is the orbits motion orthogonal to the Earth-Moon plane. We examine several families that have been explored in literature for various missions. These include Lyapunov, Halo, Vertical, and Axial. For these orbit families we:
Perform a parametric study of eclipse durations for orbits within each family. The orbits are classified by orbital period and energy using the Jacobi constant. Orbits with opportunities for eclipse-free trajectories are examined further. At this point in the analysis, the trajectories are modeled within the Circular Restricted Three-Body Problem (CRTBP) to eliminate the need for stationkeeping maneuvers to achieve periodic orbits.
Explore the geometry within the Earth-Moon system to determine how phasing (orbit injection position or time) effects the eclipse durations and frequency.
Introduce high-fidelity propagation into the analysis. Since many orbits remain stable for little more than an orbital period, we present a robust method for stationkeeping. The method minimizes fuel usage using impulsive maneuver modeling.
Join the maneuver strategies to provide a comprehensive plan for a long-duration stable orbit with minimal mission disruption due to eclipses.
Date of Conference: September 27-20, 2022
Track: Cislunar SSA