1,720,962 research outputs found
The European Asteroid Impact Mission: Phase a Design and Mission Analysis
No full textAIM is part of a joint collaboration with NASA in the AIDA (Asteroid Impact & Deflection Assessment) mission. The primary goal of AIDA is to assess the feasibility of deflecting the heliocentric path of a Near Earth Asteroid (NEA) binary system, by impacting on the surface of the smaller secondary asteroid of the couple. The work here presented is part of the phase A study, currently performed by OHB System AG, Politecnico di Milano and Spin. Works under the European Space Agency study for phase A/B1. The paper focuses on the mission analysis of AIM spacecraft during the main phases of the mission: interplanetary transfer, rendezvous with the asteroid and close proximity operations
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Close-Proximity Operations Concept of the Asteroid Impact Mission
No full textThe Asteroid Impact Deflection Assessment (AIDA) mission is an international collaboration of ESA and NASA, with the primary goals to test the ability to perform a spacecraft impact on a near-Earth asteroid and to measure and characterize the deflection caused by the impact. The ESA led Asteroid Impact Mission (AIM) is to be designed on a low-cost approach and to be launched in 2020. Its primary objective is to characterize the asteroid 65803 Didymos (1996 GT) and then to assess the consequences of an impact from a NASA provided spacecraft named DART (Double Asteroid Redirection Test) on the secondary asteroid in the binary asteroid system. Prior to the arrival of DART, AIM is planned to rendezvous with the asteroid system in mid-2022. On arrival, AIM would conduct observations that can be used to complement and prepare for the DART impact and perform technology demonstration. In addition, it is planned to release a number of CubeSat opportunity-payload and place the MASCOT-2 lander on the surface of the secondary asteroid. Further, a demonstration of deep space optical communications is planned. AIM is currently studied in the scope of a Phase B1 under ESA contract by two consortia, one of those being led by OHB System. This paper presents OHB's current mission and asteroid operations strategy, addressing mission design and operational challenges. The tight schedule (launch in 2020) and the low cost approach for spacecraft design and operations are challenging, especially in context of the high complexity and performance requirements connected to deep space mission operations and navigation. Special focus is therefore placed on asteroid local operations, the planned payload operations, the deployment of MASCOT-2 to the surface of the secondary asteroid in the binary system, the navigation strategy of AIM, and how OHB plans to overcome the challenges posed by this unique mission scenario
The Asteroid Impact Mission: Consolidated Mission Analysis and Scientific Payload Operations at Binary Asteroid Didymos
No full textThe Asteroid Impact Mission is an ESA mission, part of a joint collaboration with NASA in the AIDA (Asteroid Impact & Deflection Assessment) mission. The primary goal of AIDA is to assess the feasibility of deflecting the heliocentric path of a Near Earth Asteroid binary system, by impacting on the surface of the smaller asteroid of the couple. To this purpose, AIDA includes a kinetic impactor, DART by NASA and an observer, AIM by ESA. The consolidated mission analysis of AIM spacecraft is presented with a breakdown into the main mission phases. AIM is planned to be launched in late 2020 and to arrive at Didymos system in middle 2022. Suitable transfer solutions and launch window are presented; the approaching strategy to rendezvous with the binary system is discussed and close proximity operations at the asteroid are finally described. The results and analyses presented in the paper are currently performed by OHB System AG, Politecnico di Milano and Spin.Works under the European Space Agency study for phase A/B1 design of the AIM spacecraft. The project is currently ongoing and the mission analysis will be further iterated and refined through the design phase
ESA’s Asteroid Impact Mission: Mission Analysis and Payload Operations State of the Art
No full textThe Asteroid Impact Mission (AIM) is an ESA mission whose goal is the exploration and study of binary asteroid 65803 Didymos. AIM is planned to be the first spacecraft to rendezvous with a binary asteroid: its mission objectives include the highly relevant scientific return of the exploration as well as innovative technological demonstrations. The paper presents some updates on the ongoing design of the mission. Each phase of the operative life of AIM spacecraft is detailed with information and results on the solutions adopted for Mission Analysis design and on the strategies to suitably operate payloads. The work presented in this paper has been performed by the authors under ESA contract within the phase A design of AIM mission
Variations on the Author
Full text link“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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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