Preliminary Design Considerations for Access and Operations in Earth-Moon L1/L2 Orbits

Within the context of manned spaceflight activities, Earth-Moon libration point orbits could support lunar surface operations and serve as staging areas for future missions to near-Earth asteroids and Mars. This investigation examines preliminary design considerations including Earth-Moon L1/L2 libration point orbit selection, transfers, and stationkeeping costs associated with maintaining a spacecraft in the vicinity of L1 or L2 for a specified duration. Existing tools in multi-body trajectory design, dynamical systems theory, and orbit maintenance are leveraged in this analysis to explore end-to-end concepts for manned missions to Earth-Moon libration points

Mission design applications in the Earth-Moon system: Transfer trajectories and stationkeeping

A renewed interest in the Moon over the last decade has created a need for robust mission design algorithms in the Earth-Moon system. Strategies for computing orbits within the context of the circular restricted three-body problem as well as higher-fidelity ephemeris models are adapted to fulfill a variety of mission objectives. To support future scientific and communications objectives, periodic and quasi-periodic orbits in the vicinity the collinear L1 and L2 libration points in the Earth-Moon system are discussed. Differential corrections algorithms are presented to compute the orbits and to transition them to the higher-fidelity ephemeris models. A control-point stationkeeping strategy is modified to maintain several L2 libration point orbits and preliminary stationkeeping costs are computed. As a result of the discovery of water ice at the lunar poles, these regions have emerged as a focus of future manned mission design efforts. The use of the circular restricted three-body problem as a preliminary design tool for this problem is explored. Families of planar and out-of-plane free return trajectories are computed in the three-body model and are included as part of a four-phase bi-elliptic transfer to the lunar poles. A differential corrections scheme to compute multi-burn Earth-Moon transfers in a higher-fidelity ephemeris model is developed as well. This algorithm offers flexibility in the mission design process and is used (i) to reduce total maneuver costs in a baseline trajectory, and (ii) to explore innovative solutions. A long-term goal in this analysis is an improved understanding of the dynamical environment in this region of space

Trajectory design and orbit maintenance strategies in multi-body dynamical regimes

Regions of space in which multiple, simultaneous gravitational influences are present often give rise to dynamically complex behavior. Thus, design and maintenance of trajectories in these complicated environments is generally nontrivial. To address these challenges, the focus of this research effort is the development and application of innovative strategies to enhance trajectory design and orbit maintenance capabilities in multi-body dynamical regimes. A simplified approach for generating unstable quasi-periodic orbits identified on Poincaré maps is introduced, one that leverages existing differential corrections procedures and well-understood unstable periodic solutions in the restricted three-body problem. This approach enables the comparison of numerous unstable quasi-periodic solutions since they are viewed and analyzed simultaneously. Such a capability offers valuable insight during the post-mission analysis of the ARTEMIS Earth-Moon libration point orbits; the strategy is also useful as a means of quickly exploring the design space and completing a trade analysis as demonstrated on quasi-periodic Sun-Earth L1 trajectories applicable to future missions such as DSCOVR. Multi-burn Earth-L1/L 2 transfer trajectories relevant to potential human operations in the vicinity of Earth-Moon libration points are also explored. These transfers incorporate a close lunar passage in an effort to decrease the time-of-flight and Δ-V cost for transfers associated with delivering spacecraft to various members of the Earth-Moon L1 and L2 halo orbit families. Orbit maintenance in multi-body dynamical environments is addressed through the development of a flexible and robust long-term stationkeeping strategy designed to both maintain sensitive orbits for an arbitrary duration and to meet a set of precise end-of-mission constraints. The strategy is very general and is applied to approximate operational stationkeeping costs for a variety of Earth-Moon libration point orbits of interest for future scientific and/or human exploration activities. A related deterministic maneuver planning approach is introduced to mitigate an undesirable out-of-plane amplitude evolution in quasi-periodic libration point orbits as part of a robust global search procedure

Quantifying Mapping Orbit Performance in the Vicinity of Primitive Bodies

Predicting and quantifying the capability of mapping orbits in the vicinity of primitive bodies is challenging given the complex orbit geometries that exist and the irregular shape of the bodies themselves. This paper employs various quantitative metrics to characterize the performance and relative effectiveness of various types of mapping orbits including terminator, quasi-terminator, hovering, pingpong, and conic-like trajectories. Metrics of interest include surface area coverage, lighting conditions, and the variety of viewing angles achieved. The metrics discussed in this investigation are intended to enable mission designers and project stakeholders to better characterize candidate mapping orbits during preliminary mission formulation activities.The goal of this investigation is to understand the trade space associated with carrying out remotesensing campaigns at small primitive bodies in the context of a robotic space mission. Specifically,this study seeks to understand the surface viewing geometries, ranges, etc. that are available fromseveral commonly proposed mapping orbits architectures

Maneuver Design for the Juno Mission: Inner Cruise

The Juno spacecraft launched in August 2011 and, following a successful Earth flyby in October 2013, is on course for a nominal orbit insertion at Jupiter in July 2016. This paper examines the design and execution of deterministic and statistical trajectory correction maneuvers during the first approximately 27 months of post-launch operations that defined the "Inner Cruise" phase of the Juno mission. Topics of emphasis include the two deep space maneuvers, Earth flyby altitude biasing strategy, and the sequence of trajectory correction maneuvers executed in the weeks prior to the successful Earth gravity assist