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NARCISO: a microsatellite that takes pictures of itself
No full textIn the early nineties the Group of Astrodynamics of the University of Roma “La Sapienza” (GAUSS), established the UNISAT program at the School of Aerospace Engineering of Roma with the aim to design, manufacture and operate in orbit small educational satellites involving students, researchers and professors in a real space project. In the framework of this program four satellites have been launched in 2000, 2002, 2004 and 2006 from Baykonour Cosmodrome using DNEPR launch vehicle. Next satellite of UNISAT series, UNISAT-5, will have attitude stabilization system based on the well known gravity gradient effect by exploiting a new kind of deployable boom. The design of this deployable boom, based on harmonic steel tape coil spring, is inspired to the booms developed for the SIRDARIA deorbiting system boarded on UNISAT-4. The same concept has been adapted to the attitude control of UNISAT-5, by increasing the boom length up to three meters. The boom deployment is going to be tested on board REXUS rocket. This is a small ballistic rocket, launched from ESRANGE base on the framework of ESA REXUS/BEXUS program, used to perform small experiments under microgravity conditions. The design, realization and tests of the boom are depicted in the first part of the paper. The second part of this paper deals with design and realization of the tip-mass. It is a one kilogram, ten by ten centimeters, autonomous payload, capable to perform simple experiments such as taking pictures of the mother satellite, which will be transmitted to the mother satellite itself using a wireless connection and then downloaded to the ground station. The tip-mass, named NARCISO, is realized by rapid prototyping technique, in ABS plastic material. Exploiting this technique, a complete structure capable of hosting all subsystems required by a small satellite, from electronic board to antennas and solar cells, can be manufactured in a short time (about 23 hours) with reduced costs. Moreover, almost any shape and mechanical detail within 0.3 mm accuracy (the height of the single layer) can be obtained. The UNISAT-5 satellite and the NARCISO tip-mass will take pictures of each other. In this way, the UNISAT solar cells degradation can be photographed and the ABS degradation can be also monitored by remote visual inspection
Automatic image analysis for space debris measurement
No full textThe space debris represents a danger for operative satellites and human missions. A large amount of debris is located in Low Earth Orbit and in Geostationary Orbit. The worldwide surveillance networks, mainly NORAD and RosKosmos, started monitoring debris since a long a time and testify the continuous growing
tendency in the number of objects. Since a few years Aerospace Systems Laboratory of University of Rome started optical space debris observation campaigns by dedicated observatories. The observation activity includes not only planning and taking images of selected portions of the sky, but also analysis of raw picture data to extract the relevant astrometry and/or light-curve information. During the optical campaigns a large amount of images is typically taken and one of the most time consuming activities in optical space objects observation is the data analysis, requiring dedicated and specialized man power. This is the reason why the development of automatic images processing algorithms and procedures to identify the presence of debris, to identify its nature and perform the astrometry computations would highly desirable. This paper deals with the development of automatic procedures and algorithms to detect objects with
relative motion with respect to stars in both sidereal tracking mode or terrestrial fixed one. In particular, the developed software is able to recognize the debris inside the picture, solve the star field within the picture and use both these information to achieve the angular measurements of the debris. Relevant efforts have been devoted to software development, such that human interaction is not required. The astrometry computations
algorithm works without predefined information about the image. In particular the knowledge of the pointing angles are not required, even if starting from a condition close to the actual one improved the convergence speed, and the picture can be solved starting from a “lost in space" condition. The main algorithm drivers and the tradeoffs in the software implementation are depicted and preliminary results and software performance in actual observation campaigns are discussed in the paper
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
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
Hands-on education for innovative research fields: A cubesat manufactured with rapid protyping technique
No full textThe structure of Cubesat that will be presented in the following paper was realized within the activities of Space Robotics Laboratory (SRL) and the V-Lab of the II Faculty of Engineering of Bologna University in collaboration with the Space System group of University of Rome "LA SAPIENZA". The work team that is persecuting the project proposed is composed by PHD, master and bachelor students. Several projects aimed at hands-on education are developed by the SRL including: an observatory for observation and monitoring of space debris and the creation of payloads for sounding rockets and stratospheric balloons, that are part of the ESA education program; together with the realization of the Cubesat depicted in the paper. Cubesat is a cube-shaped nano-satellite with the side of 100 mm. Despite its small size, it has a system for attitude control, a telecommunication system, a camera and a power system. Considering the size and requirements of the various systems, the organization of interior spaces was one of the major issues in the design of the structure for which it was necessary to identify innovative solutions. The Cubesat structure was realized by polymer (ABS - Acrylonitrile - Butadiene - Styrene) with the technique of "rapid prototyping" thanks to equipment provided by the V-Lab of the II Faculty of Engineering of University of Bologna. The Rapid Prototyping technique has several advantages including the quick implementation and low cost. Moreover, for the construction of a small satellite it is very useful the ability to succeed in details, sometimes difficult to achieve with the use of tools machine except with a significant increase in costs. Another important advantage is the ability to use a material with a lower density than the commonly used aluminum alloy. The structure must be able to resist at the stresses due to the launch vibrational and static loads. For this several simulations using a FEM code have been performed during the design phase, moreover a Test-Pod system in aluminum alloy was built and used to perform vibration tests for the qualification to launch with Indian PLSV launcher of the Cubesat prototype. The paper shows the detailed design of the Cubesat with the analysis of solutions to the critical points, the results of numerical simulations and the results of vibration tests carried out for the launch qualify on the Cubesat prototype. Copyright ©2010 by the International Astronautical Federation. All rights reserved
Testing An Innovative Boom For Microsatellite Attitude Stabilization: An Educational Experiment On Sounding Rocket Rexus-7
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