Transfers between moons with escape and capture patterns via Lyapunov exponent maps

This contribution focuses on the design of low-energy transfers between planetary moons and presents an efficient technique to compute trajectories characterized by desirable behaviors in the vicinities of the departure and destination bodies. The method utilizes finite-time Lyapunov exponent maps in combination with the Moon-to-Moon Analytical Transfer (MMAT) method previously proposed by the authors. The integration of these two components facilitates the design of direct transfers between moons within the context of the circular restricted three-body problem, and allows the inclusion of a variety of trajectory patterns, such as captures, landings, transits and takeoffs, at the two ends of a transfer. The foundations and properties of the technique are illustrated through an application based on impulsive direct transfers between Ganymede and Europa. However, the methodology can be employed to assist in the design of more complex mission scenarios, such as moon tours

A review on hot-spot areas within the Cislunar region and upon the Moon surface, and methods to gather passive information from these regions

The Cislunar region is becoming a focal point of expansion over upcoming decades. Long-term Lunar infrastructure supporting Cislunar expansion must be located in key regions on the Moon\u27s surface and in space. The purpose of this research is to identify key regions of interest on and around the Moon by investigating the location of valuable resources and the destination of future missions. Once key regions are established, low-lunar orbit trajectories are analyzed to enable methods of passive information gain in identified key regions of interest. It has been found that the South Pole and Earth-sided craters are key regions on the Lunar surface in the near future. Furthermore, an analysis of low lunar orbit trajectories is completed and demonstrates a possible framework to service the South Pole region

Understanding context dependency in the response of forest understorey plant communities to nitrogen deposition

© 2018 Elsevier Ltd Understorey communities can dominate forest plant diversity and strongly affect forest ecosystem structure and function. Understoreys often respond sensitively but inconsistently to drivers of ecological change, including nitrogen (N) deposition. Nitrogen deposition effects, reflected in the concept of critical loads, vary greatly not only among species and guilds, but also among forest types. Here, we characterize such context dependency as driven by differences in the amounts and forms of deposited N, cumulative deposition, the filtering of N by overstoreys, and available plant species pools. Nitrogen effects on understorey trajectories can also vary due to differences in surrounding landscape conditions; ambient browsing pressure; soils and geology; other environmental factors controlling plant growth; and, historical and current disturbance/management regimes. The number of these factors and their potentially complex interactions complicate our efforts to make simple predictions about how N deposition affects forest understoreys. We review the literature to examine evidence for context dependency in N deposition effects on forest understoreys. We also use data from 1814 European temperate forest plots to test the ability of multi-level models to characterize context-dependent understorey responses across sites that differ in levels of N deposition, community composition, local conditions and management history. This analysis demonstrated that historical management, and plot location on light and pH-fertility gradients, significantly affect how understorey communities respond to N deposition. We conclude that species\u27 and communities\u27 responses to N deposition, and thus the determination of critical loads, vary greatly depending on environmental contexts. This complicates our efforts to predict how N deposition will affect forest understoreys and thus how best to conserve and restore understorey biodiversity. To reduce uncertainty and incorporate context dependency in critical load setting, we should assemble data on underlying environmental conditions, conduct globally distributed field experiments, and analyse a wider range of habitat types. We find that nitrogen deposition effects on temperate forest understoreys are highly context dependent, with implications for assignment of critical loads, and for conservation and restoration of plant biodiversity