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Systematic Analysis of Cislunar Escape Opportunities for Explorationand Planetary Defence Missions
Get PDFCislunar Escape Trajectories Through Patched Sun-Earth/Earth-Moon Three-Body Problem
Get PDFIn the next decade, the exploitation of the Cislunar environment for both manned and unmanned missions will open the space frontier for human exploration of the Moon, Mars and asteroids. The Lunar Gateway (LOP-G) has been proposed as a potential hub for excursions to Mars and activities in support of exploration and planetary defence. Within this context, in this paper, the problem to design a transfer from the Earth-Moon Libration Points to a destination object outside the Cislunar environment is analysed. In general, the dynamical environment within the Earth-Moon system is rather complex, and the trajectory design is non-trivial. In this study, a further degree of complexity is introduced by the need to patch the escape trajectory with a heliocentric leg, preserving its epoch-dependence. That introduces a phasing problem within the design of the trajectory, which is considered multi-impulsive. Therefore, the problem is split in two steps. First, families of trajectories escaping the Cislunar environment are characterized, to build-up the understanding of the escape mechanisms. Then, a methodology to select the subset of escape trajectories that best match the departure conditions, depending on the epoch and the DV available, is applied; relevant applicative cases are discussed in the paper to better highligthen the approach flexibility
Refined Mission Analysis for Heracles - a Robotic Lunar Surface Sample Return Mission Utilizing Human Infrastructure
Get PDFDesign and Validation of Ultra Low Thrust Transfers to the Sun-Earth Saddle Point with Application to LISA PathFinder Mission Extension
No full textIn this paper we present methods and concepts to design and validate highly nonlinear orbits characterized by ultra low control. These features are met when flying through the Saddle Points, which are location in the Solar System when gravitational accelerations balance. Trajectory optimization is embedded into high-fidelity environments, where accurate description of the spacecraft natural and controlled motion is achieved. Orbit determination and navigation analysis rely on high-fidelity models for both the space and ground segments assets as well. Tools have been developed and applied to the case of the possible mission extension of Lisa Pathfinder
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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