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Academic literature on the topic 'Constellations'

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Published: 4 June 2021
Last updated: 1 August 2024

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Journal articles on the topic "Constellations"

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Deccia, Carlos M. A., David N. Wiese, and Robert S. Nerem. "Using a Multiobjective Genetic Algorithm to Design Satellite Constellations for Recovering Earth System Mass Change." Remote Sensing 14, no. 14 (July 11, 2022): 3340. http://dx.doi.org/10.3390/rs14143340.

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The Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GRACE-FO) provided twenty years of data on Earth’s time-varying gravity field. Due to their design, GRACE and GRACE-FO are inherently limited in their spatiotemporal coverage, limiting their resolution to a few hundred kilometers and temporally to roughly monthly solutions. To increase the global spatiotemporal resolution and allow for the determination of submonthly time-varying gravity field signals, a constellation of GRACE-type satellite pairs is a possible path forward. Advances in small form factor instrumentation for small satellites have become progressively inexpensive, reliable, and of higher quality. This leads us to consider that a constellation of GRACE-type small satellites could be part of future gravimetric satellite missions. In this work, we investigate the viability and limitations of a genetic-algorithm-based optimization and its objective function to generate satellite constellations to recover daily Earth system mass changes. The developed approach is used to create satellite constellations that are optimally designed to recover gravity variations of sufficient resolution at a range of temporal frequencies (i.e., daily to monthly). We analyze a constellation’s performance using a combination of observability in space, accounting for directionality, and homogeneity in time. This allows us to navigate through a vast search space in a relatively short period of time and estimate the relative performance of constellations to each other. Using evolutionary theory, we converge towards a set of optimally selected orbits. The characteristics of the designed constellations have been validated using high-fidelity numerical simulations. We summarize these results and discuss their implications for possible future constellations of small GRACE-like satellite pairs. The resulting constellations have an inherently improved spatiotemporal performance, which reduces temporal aliasing errors and allows the characterization of daily mass-change effects.
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Teng, Yunlong, and Jinling Wang. "New Characteristics of Geometric Dilution of Precision (GDOP) for Multi-GNSS Constellations." Journal of Navigation 67, no. 6 (July 15, 2014): 1018–28. http://dx.doi.org/10.1017/s037346331400040x.

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For multi-Global Navigation Satellite System (GNSS) constellations, the Geometric Dilution of Precision (GDOP) is an important parameter utilised for the selection of satellites. This paper has derived new formulae to describe the change of GDOP. The result shows that, for GNSS single point positioning solutions, if one more satellite belonging to the existing tracked multi-GNSS constellation used in the single point positioning solution is added, the GDOP always decreases with the number of the added satellites. On the other hand, when the constellation of the added satellite is not from the tracked existing constellations, the different numbers of the added satellites have different influences on the change of GDOP. Generally, adding one satellite from another constellation into the existing multi-GNSS constellations will increase the GDOP, but adding two satellites will decrease the GDOP compared with adding one from another constellation. Additionally, the GDOP also increases in the cases of adding two satellites from two different constellations into the tracked existing constellations.
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Zhao, Shuailong, Qinyu Zhu, Xuefeng Tao, and Yasheng Zhang. "Deployment of Constellation with Different Inclinations Using the Nodal Precession and Thrust." Sensors 24, no. 2 (January 19, 2024): 631. http://dx.doi.org/10.3390/s24020631.

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Strategy selection is critical for constellation deployment missions, both in terms of energy consumption and time cost. The different effects of impulse thrust and continuous thrust on orbit elements lead to a different choice of strategy. With impulse thrust, constellation types are differentiated according to high and medium-low inclinations. Constellations with high inclination are deployed using a strategy that controls the inclination. Constellations with medium-low inclination are deployed using a strategy that controls the semi-long axis. With continuous thrust, constellations are classified according to high, medium, and low inclination. High inclination constellations are deployed with a strategy of controlling inclination. Medium inclination constellations are deployed with a strategy that controls the semi-long axis. Low inclination constellations are deployed with a strategy of directly applying continuous thrust.
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Somov, Yevgeny, Sergey Butyrin, and Sergey Somov. "Guidance, navigation and attitude control of mini-satellites in a low earth orbit constellation for areal survey." Cybernetics and Physics, Volume 12, 2023, Number 2 (September 30, 2023): 145–51. http://dx.doi.org/10.35470/2226-4116-2023-12-2-145-151.

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The problems of guidance, navigation and attitude control in a constellation of mini-observation satellites are considered. The developed methods and algorithms for scanning areal survey performed by these constellations in the low sun-synchronous orbits are presented. The most important new results are methods for coordinated angular guidance of satellites in the constellation’s orbital planes and the comparison results for sequences of the areal space surveys.
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Putraga, Hariyadi, Arwin Juli Rakhmadi Butar-Butar, Muhammad Hidayat, and Muhammad Dimas Firdaus. "THE STUDY OF ARABIC CONSTELLATION FROM THE BOOK SUWAR AL-KAWAKIB AL-THABITA USING STELLARIUM SOFTWARE." Journal of Islam and Science 9, no. 2 (December 30, 2022): 111–18. http://dx.doi.org/10.24252/jis.v9i2.31526.

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The constellations originating from Arab civilization were still very little known and studied. Al-Ṣūfi's book, al-Kawākib al-Thābitah, contains the record of coordinates, approximate magnitudes, and star details with graphs. This study examines the difference of stars in the sample constellation, compares the visual appearance of the illustrations on the Stellarium software, and studies the differences between the western constellations and the Arabic constellations. The result shows some differences between the constellations of the almagest and al-Kawākib al-Thābitah in the number of stars in the sample constellations, differences in illustrations from the orientalized figures, and the star magnitude in al-Ṣūfi's work that similar to Ptolemy's works. Al-Sufi identified a total of 134 additional stars, 65 stars located in the Northern constellations, 41 stars in the Zodiac constellation, and 28 stars in the Southern constellations. His observations showed that the magnitude values of 520 stars out of a total of 1022 stars were identical between al-Sufi and Ptolemy. Stellarium provides an excellent visual presentation of the Arabic constellations according to Al-Sufi's book that shows position, illustration, and mapping in the night sky.
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Sun, Tianyu, Min Hu, and Chaoming Yun. "Low-Orbit Large-Scale Communication Satellite Constellation Configuration Performance Assessment." International Journal of Aerospace Engineering 2022 (March 11, 2022): 1–8. http://dx.doi.org/10.1155/2022/4918912.

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A constellation configuration performance evaluation method is proposed for the performance evaluation of the low-orbit large-scale communication satellite constellations. The practicality and feasibility analysis of the constellation configuration is mainly studied from the constellation coverage performance. Based on the consideration of the coverage performance of the LEO satellite constellation, four simulation models are established for the single coverage rate, observation elevation angle, number of visible satellites under different observation elevation angles, and coverage efficiency of the constellation. A population distribution density function is established according to the characteristics of population distribution to find the average minimum observation elevation angle and the average number of visible satellites under the population distribution. The evaluation method is applied to three typical low-orbit large-scale communication satellite constellations, Telesat, OneWeb, and Starlink, to derive the coverage performance index values of each constellation and to compare and analyze the characteristics of the three constellations. The results show that the evaluation method can evaluate the configuration performance of different types of LEO large-scale constellations and provide a basis and reference for the optimal design and evaluation of future LEO large-scale constellation configurations.
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Geissinger, Andrea, and Christofer Laurell. "Tracing brand constellations in social media: the case of Fashion Week Stockholm." Journal of Fashion Marketing and Management: An International Journal 22, no. 1 (March 12, 2018): 35–48. http://dx.doi.org/10.1108/jfmm-12-2016-0115.

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PurposeThe purpose of this paper is to explore the effects of fashion weeks on brand constellations of participating fashion companies in social media.Design/methodology/approachThe study analyses how brand constellations take form for seven Swedish fashion companies before, during and after Fashion Week Stockholm. In total, 3,449 user-generated contents referring to the sampled brands were collected and analysed.FindingsOn average, brand constellations of participating companies are increasingly incorporating other participating brands as a result of the fashion week. Based on the presented results, four brand constellation outcomes for participating fashion companies are identified: brand constellation amplification, concentration, division and dilution.Research limitations/implicationsAs this paper is focussed on the Swedish market, additional results from fashion weeks taking place in other cities would be beneficial to verify the four brand constellation outcomes.Practical implicationsThe results question the resilience of professionally curated brand constellations due to the emergence of user-driven constellations that also shape the position of fashion brands. Therefore, this development can potentially have a considerable impact on often carefully orchestrated brand positioning strategies executed by fashion companies.Social implicationsDigitally fuelled interdependences of brand constellations by professionals and consumers attest to the dilution of borders between consumers and producers.Originality/valueThis paper contributes to the field of fashion marketing and management by identifying four different brand constellation outcomes in social media for participating fashion companies as a result of fashion weeks and how to managerially handle these respective outcomes.
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Kurtik, Gennady E. "muluz3, mul dGula, and the Early History of Mesopotamian Constellations." Journal for the History of Astronomy 50, no. 3 (August 2019): 339–59. http://dx.doi.org/10.1177/0021828619853676.

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This article is devoted to cuneiform sources shedding light on history of Mesopotamian constellations muluz3 (“The Goat”) located in the area of modern Lyra, mul d Gula, a goddess connected with muluz3, and mulur.gi7 (“The Dog”) located in Hercules. In the eyes of ancient Mesopotamians, these constellations were bound by complex relationships that were changing in course of time. Gula was the goddess of the Goat constellation, and the Dog was a sacred animal of Gula. In the Neo-Assyrian period, Gula’s anthropomorphic image was considered to be a figure of the constellation muluz3, while figures of other constellations with animal names always corresponded to their names. It is shown in the article that originally (at the end of the third and the beginning of the second millennium b.c.) there were only two constellations (muluz3 and mulur.gi7) out of three mentioned above singled out in the Mesopotamian sky. The goddess Gula became associated with the constellation muluz3 only in the second half of the second millennium b.c.
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Zhang, Yunfan, Chi Han, Feihuang Chu, Wei Xiong, and Luliang Jia. "Jamming Analysis between Non-Cooperative Mega-Constellations Based on Satellite Network Capacity." Electronics 13, no. 12 (June 14, 2024): 2330. http://dx.doi.org/10.3390/electronics13122330.

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Due to the openness of inter-satellite links (ISLs) in mega-constellations, the threat posed by jamming from non-cooperative constellations is becoming increasingly significant. Most of the existing approaches focus on the up/down link capacity between satellites and ground stations, which differs greatly from the situation whereby ISLs are subjected to non-cooperative jamming. Therefore, this work investigates the transmission rates of ISLs under jamming from non-cooperative mega-constellations. Based on this, a novel satellite network capacity calculation method is proposed to evaluate the mega-constellation network capacity when the transmission rates change dynamically. The simulation results show that the satellite number, jamming power and inclination of non-cooperative constellations have a significant influence on the network capacity. The optimal jamming efficiency occurs when the constellation inclinations are close.
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Guan, Meiqian, Tianhe Xu, Fan Gao, Wenfeng Nie, and Honglei Yang. "Optimal Walker Constellation Design of LEO-Based Global Navigation and Augmentation System." Remote Sensing 12, no. 11 (June 6, 2020): 1845. http://dx.doi.org/10.3390/rs12111845.

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Low Earth orbit (LEO) satellites located at altitudes of 500 km~1500 km can carry much stronger signals and move faster than medium Earth orbit (MEO) satellites at about a 20,000 km altitude. Taking advantage of these features, LEO satellites promise to make contributions to navigation and positioning where global navigation satellite system (GNSS) signals are blocked as well as the rapid convergence of precise point positioning (PPP). In this paper, LEO-based optimal global navigation and augmentation constellations are designed by a non-dominated sorting genetic algorithm III (NSGA-III) and genetic algorithm (GA), respectively. Additionally, a LEO augmentation constellation with GNSS satellites included is designed using the NSGA-III. For global navigation constellations, the results demonstrate that the optimal constellations with a near-polar Walker configuration need 264, 240, 210, 210, 200, 190 and 180 satellites with altitudes of 900, 1000, 1100, 1200, 1300, 1400 and 1500 km, respectively. For global augmentation constellations at an altitude of 900 km, for instance, 72, 91, and 108 satellites are required in order to achieve a global average of four, five and six visible satellites for an elevation angle above 7 degrees with one Walker constellation. To achieve a more even coverage, a hybrid constellation with two Walker constellations is also presented. On this basis, the GDOPs (geometric dilution of precision) of the GNSS with and without an LEO constellation are compared. In addition, we prove that the computation efficiency of the constellation design can be considerably improved by using master–slave parallel computing.
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Dissertations / Theses on the topic "Constellations"

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Morris, Neil Gerald. "Working memory constellations." Thesis, Durham University, 1986. http://etheses.dur.ac.uk/7057/.

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Evidence is presented that supports the view that most models of short-term memory cannot account for the flexibility of the primary memory system. It is argued that the working memory model outlined by Baddeley and Hitch (1974) is, however, a potentially adequate model. Working memory, in this thesis, is depicted as a system that assembles 'constellations' consisting of the central executive and one or more sub-systems. This view suggests a formulation that is considerably more complex than the 1974 model. The empirical studies examine the role of the visuo-spatial scratch pad in the formation and maintenance of working memory constellations. It is concluded from these studies that the scratch pad is independent of the articulatory loop but is usually coupled to the central executive except during maintenance rehearsal. Furthermore, it can be used concurrently with the articulatory loop to process spatial aspects of highly verbal tasks. However a constellation consisting of the executive, the loop and the scratch pad is vulnerable to a wider range of interference effects than a simpler constellation. Paivio (1971) suggested that 'dual coding' leads to better memory performance, however, this is only the case when no distractors are present. The final two chapters present some speculations on how working memory research might proceed in the future. It is concluded that the current trend towards collecting convergent evidence and the emphasis on testing theory in applied situations should give us insights into memory that were not available to Ebbinghaus and other early memory researchers.
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Ferentinos, Andrew (Andrew George Phillip). "Constellations and anti-corridors." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/72812.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Architecture, 2012.
Page 77 blank. Cataloged from PDF version of thesis.
Includes bibliographical references (p. 67-69).
To perceive the many stars in the sky, corridic logic would force one to view one star at a time, one after the other in a linear order. An anti-corridic logic, on the other hand, is non-linear and permits constellations to emerge: many stars can be perceived at once and the imagination can link them into any desired figure. The space of corridors is linear: rooms are perceived and passed in a fixed sequence of one space following another. The space of anti-corridors is non-linear: rooms are dispersed into a field. Many spaces can be perceived at once and one can pass through them in any order. Desired constellations can emerge. Airports and intermodal hubs typically follow corridic logic. An airport/intermodal hub that is anti-corridic disperses all spaces into a field of options whereby individuals with different itineraries can perceive and move through a field of spatial choices resulting in ideally perceived and desired spatial constellations. This thesis proposes a prototype for an anti-corridic airport/ intermodal hub.
by Andrew Ferentinos.
S.M.
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Wood, Lloyd. "Internetworking with satellite constellations." Thesis, University of Surrey, 2001. http://epubs.surrey.ac.uk/704760/.

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The development and growth of the Internet during the past thirty years has led to demand for and development of Internet services everywhere and over every possible communications medium. This includes the medium of satellite communications. During those same three decades, the growth in use of satellite communications to provide a widely-available wireless communications infrastructure has led to the development of broadband satellite communications using satellite constellation networks. These two technological trends have intersected. Here, we examine networking and internetworking issues affecting satellite networking in complex satellite constellation networks, and determine what is needed in order to support services based on the TCP/IP suite well in satellite constellations. We analyse constellation network topology. Its movement and effects on end-to-end delays experienced by network traffic travelling across the constellation are examined in detail. Analysis of the impact of cross-seam links upon delays experienced by traffic across star constellations shows that the use of cross-seam links is worthwhile. We examine the effects of multi-path routing within the constellation upon TCP communication, and demonstrate the performance advantages of an intelligent flowbased approach to routing in the constellation network. The desirability of implementing IP routing functionality in the space segment of the constellation is shown. The use of IP routing, to enable good support for IP QoS and IP multicast, is shown to be possible. We present an approach to implementing IP multicast within the constellation, evaluating use of a core-based tree algorithm, and outline an architecture permitting IP routing of IP traffic in an ATM-based satellite constellation network, using MPLS. Finally, we present and demonstrate the advantages of a novel method of managing path delay between ground terminals across a rosette constellation with intersatellite links, by using controlled handover to manage surface diversity to provide classes of service to network traffic.
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Galai, Yoav. "Transnational constellations of the past." Thesis, University of St Andrews, 2017. http://hdl.handle.net/10023/12200.

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This dissertation interrogates the political use of the past in global politics, with a focus on Israel/Palestine. Collective memory is mostly theorised in IR as determinant of national identities. Similarly, in the field of Memory Studies, collective memory is mostly confined to “Methodological Nationalism.” My main argument is that while national narratives purport to be stand-alone stories of the past, or monological narratives, they are in fact in constant negotiation with other stories of that past, they are dialogical. Furthermore, their dynamic transcends the boundaries of the nation state and of transnational institutional politics. To encapsulate these cross-narrative intertextual relationships into a framework that would enable productive analysis, I suggest the re-articulation of the dialogical relationships as transnational constellations, which focus first and foremost on the narratives themselves.
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Huckert, Chantal. "Constellations textiles : la leçon Maya." Paris, EHESS, 1992. http://www.theses.fr/1991EHES0319.

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L'objectif de ce travail est d'analyser et interpreter les figures textiles mayas (c'est a dire, les representations de certains decors textiles), de l'epoque classique. Ayant-disparu physiquement, les tissus existent sous la forme de representations sur les monuments et les ceramiques. L'interet est de connaitre la fonction et la signification de leurs decors en tant qu'ils font partie de la representation dans son ensemble. J'ai choisi des exemples qui me permettent d'etudier les figures textiles dans un contexte epigraphique. La these comprend six chapitres organises conformement au reperage et a la classification des figures. Chaque chapitre est centre sur des figures repetees selon un patron specifique. Dans chacun des chapitres j'examine le cas des figures qu'il comprend et les materiaux iconographiques, stela, linteau, ceramique, qui leur sont rattaches. J'analyse ces representations en tant que plan et tableau et je signale les donnees historiques. Par consequent je puis lire ou rapporter les figures aux entites divines, aux toponymes et aux rituels, indiques dans l'iconographie et l'epigraphie correspondantes. Dans la conclusion a chaque fin de chapitre je reprends les resultats des enquetes specifiques et ebauche ce qui constituera un lexique de figures textiles. Une conclusion commune aux six chapitres preconise l'etude particuliere de chaque site de provenance
This work takes as its central objective the interpretation and analysis of mayan textiles figures (that is, representations of various patterns of textiles), of the classic epoch. Not having survived as actual fabrics, the textiles appear primarily in the form of monumental and ceramic representations. My interest is to know what are the function and the meaning of the textiles figures within the representation as a whole. Have selected examples which permit me to study the figures within an epigraphic context. The dissertation comprises six chapters which are organized according to the location and classification of the figures. Each chapter focuses on designs repeated in a specific pattern. In each one examine the case of the respective figures and the iconographic materials-stela, lintel, ceramic, which pertain to them. Analysed these representations as a plan, as a picture and as an object having historical significance. Consequently am able to read or reference the figures in terms of their relationship to the divines entities, toponymes and rituals, indicated in the iconography and epigraphy to which they correspond. In the conclusion of each chapter review the results of these specific studies and then outline what will constitute a lexicon of textiles figures. A comprehensive conclusion of the six chapters recommend the particular study of each site of provenance
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Shah, Naresh Harkishan. "Automated station-keeping for satellite constellations." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10514.

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Toh, Dorothy. "The changing constellations of audit quality." Thesis, London School of Economics and Political Science (University of London), 2016. http://etheses.lse.ac.uk/3426/.

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This thesis examines the emergence and rise of audit quality as an object of concern from the post-war period onwards, as manifested in the discourse of regulators, practitioners and academics primarily in the US and the UK. By drawing upon Burchell et al’s (1985) notions of the arena and the constellation, this thesis seeks to investigate the changing nature of the audit quality ‘problem’ and in so doing, reconceptualises the constellation as being dynamic in nature. It puts forward the notions of the emergent constellation, when an altogether new arena becomes formulated through the emergence of a new event or object and the reformation constellation, when an existing field of operations becomes further delineated or differentiated into more distinct arenas. Central to this dynamism is the notion of linkages, and the precise nature of the linking work entailed, which connect together disparate ideas and attach these to the audit quality discourse. Together, this thesis aims to contribute to our understanding of audit quality, the interrelationship between the three arenas of regulation, practice and academia, and of accounting change. Ultimately, this thesis will show that audit quality, a topic of profound and resilient interest, should be understood primarily, and merely, as a basis through which very particular sets of historically contingent concerns and practices are articulated, and that efforts to measure and improve audit quality are fraught with difficulties. Indeed, the attempts to do so play a role in shifting the conceptualisation of the audit quality problem and are consequently, and in this sense, susceptible to continual failure. An alternate interpretation of the importance and meaning of this rise of audit quality, beyond and irrespective of the large scale failures and crises, is an alignment with the trend of economization in society.
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Hanusse, Nicolas. "Cartes, constellations et groupes : questions algorithmiques." Bordeaux 1, 1997. http://www.theses.fr/1997BOR10646.

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Lobjet de cette etude est la constellation. La carte en est un eminent representant. Un des objectifs de notre travail est de mettre en avant le caractere representatif d'une carte et de montrer qu'une carte est un objet unificateur de domaines varies : combinatoire, theorie de surfaces de riemann, theorie des groupes, theorie de galois. Nous nous sommes attaches a l'etude et au developpement d'algorithmes pour la manipulation et la visualisation des constellations. Les principaux problemes abordes sont les suivants : la generation cartographique, l'action du groupe de tresses sur les constellations, composition et decomposition de constellations et algorithmes de dessins automatiques de cartes.
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Becker, Tanja. "Moduli spaces of (G,h)-constellations." Nantes, 2011. http://www.theses.fr/2011NANT2073.

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Nous construisons l'espace de modules M(X) des (G; h)constellations stables sur X pour un groupe réductif G qui agit sur un schéma ane X sur C et pour une fonction de Hilbert h: IrrG ! N0. Cet espace de modules est une généralisation commune du schéma de Hilbert invariant d'après Alexeev et Brion [AB05] et de l'espace de modules des Gconstellations stables pour un groupe ni G introduit par Craw et Ishii [CI04]. Notre construction d'un morphisme M(X) ! X//G fait de cet espace de modules un candidat pour une résolution des singularités du quotient X//G. De plus, nous déterminons le schéma de Hilbert invariant de la bre en zéro de l'application moment d'une action de Sl2 sur (C2)6. C'est un des premiers exemples d'un schéma de Hilbert invariant avec multiplicités. Ceci nous amène à décrire une façon générale de procéder pour eectuer de tels calculs. En outre, nous démontrons que notre schéma de Hilbert invariant est lisse et connexe : Cet exemple est donc une résolution des singularités de la réduction symplectique de l'action
Given a reductive group G acting on an a#ne scheme X over C and a Hilbert function h: IrrG ! N0, we construct the moduli space M#(X) of ##stable (G; h)#constellations on X, which is a common generalisation of the invariant Hilbert scheme after Alexeev and Brion [AB05] and the moduli space of ##stable G#constellations for #nite groups G introduced by Craw and Ishii [CI04]. Our construction of a morphism M#(X) ! X//G makes this moduli space a candidate for a resolution of singularities of the quotient X//G. Furthermore, we determine the invariant Hilbert scheme of the zero #bre of the moment map of an action of Sl2 on (C2)#6 as one of the #rst examples of invariant Hilbert schemes with multiplicities. While doing this, we present a general procedure for the realisation of such calculations. We also consider questions of smoothness and connectedness and thereby show that our Hilbert scheme gives a resolution of singularities of the symplectic reduction of the action
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Becker, Tanja. "Espaces de modules de (G,h)-constellations." Phd thesis, Université de Nantes, 2011. http://tel.archives-ouvertes.fr/tel-00675853.

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Nous construisons l'espace de modules M_θ(X) des (G,h)-constellations θ-stables sur X pour un groupe réductif G qui agit sur un schéma affine X sur C et pour une fonction de Hilbert h: Irr G → N_0. Cet espace de modules est une généralisation commune du schéma de Hilbert invariant d'après Alexeev et Brion et de l'espace de modules des G-constellations θ-stables pour un groupe fini G introduit par Craw et Ishii. Notre construction d'un morphisme M_θ(X) → X//G fait de cet espace de modules un candidat pour une résolution des singularités du quotient X//G. De plus, nous déterminons le schéma de Hilbert invariant de la fibre en zéro de l'application moment d'une action de Sl_2 sur (C²)⁶. C'est un des premiers exemples d'un schéma de Hilbert invariant avec multiplicités. Ceci nous amène à décrire une façon générale de procéder pour effectuer de tels calculs. En outre, nous démontrons que notre schéma de Hilbert invariant est lisse et connexe : Cet exemple est donc une résolution des singularités de la réduction symplectique de l'action.
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Books on the topic "Constellations"

1

Keefer, Janice Kulyk. Constellations. Toronto: Random House, 1988.

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Rustad, Martha E. H. Constellations. Mankato, Minn: Capstone Press, 2012.

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Reuzé, Sébastien. Constellations. Bruxelles: Lettre volée, 2002.

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Reuz, Sbastien. Constellations. Bruxelles: La lettre vole, 1998.

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Kim, F. S. Constellations. New York: Children's Press, 2010.

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Dutilleux, Henri. Constellations. Paris: Maule, 2007.

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Jepaul-Raddhoa, Soolekha. Constellations. Port-Louis, Mauritius: Quad Printers, 2001.

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Sipiera, Diane M. Constellations. New York: Children's Press, 1997.

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Feehily, Fergus. Constellations. Helsinki: Academy of Fine Arts Helsinki, 2018.

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Barentine, John C. Uncharted Constellations. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-27619-9.

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Book chapters on the topic "Constellations"

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Schoone, Adrian. "Constellations." In SpringerBriefs in Arts-Based Educational Research, 39–97. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-35495-4_3.

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Bagnall, Philip M. "The Constellations." In The Star Atlas Companion, 19–472. New York, NY: Springer New York, 2012. http://dx.doi.org/10.1007/978-1-4614-0830-7_3.

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Fleeter, Rick. "Satellite Constellations." In The Logic of Microspace, 157–62. Dordrecht: Springer Netherlands, 2000. http://dx.doi.org/10.1007/978-94-011-4273-1_17.

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Michael, Eilenberg. "Frontier constellations." In Routledge Handbook of Asian Borderlands, 180–89. New York : Routledge, 2018.: Routledge, 2018. http://dx.doi.org/10.4324/9781315688978-16.

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Eilenberg, Michael. "Frontier constellations." In Routledge Handbook of Asian Borderlands, 180–89. New York : Routledge, 2018.: Routledge, 2018. http://dx.doi.org/10.4324/9781315688978-19.

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Bremer, Nadieh, and Shirley Wu. "Royal Constellations." In Data Sketches, 116–31. First edition. | Boca Raton : CRC Press, 2020. | Series: AK Peters visualization series: A K Peters/CRC Press, 2021. http://dx.doi.org/10.1201/9780429445019-11.

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Martínez-Ariño, Julia. "Actor constellations." In Urban Secularism, 38–56. Abingdon, Oxon ; New York, NY, USA : Routledge, 2021. | Series: Routledge advances in sociology: Routledge, 2020. http://dx.doi.org/10.4324/9780429320606-3.

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Lull, José, and Juan Antonio Belmonte. "Egyptian Constellations." In Handbook of Archaeoastronomy and Ethnoastronomy, 1477–87. New York, NY: Springer New York, 2014. http://dx.doi.org/10.1007/978-1-4614-6141-8_148.

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Mastorakou, Stamatina. "Greek Constellations." In Handbook of Archaeoastronomy and Ethnoastronomy, 1555–61. New York, NY: Springer New York, 2014. http://dx.doi.org/10.1007/978-1-4614-6141-8_158.

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de Almeida, Guilherme. "The Constellations." In Navigating the Night Sky, 1–17. London: Springer London, 2004. http://dx.doi.org/10.1007/978-1-85233-898-5_1.

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Conference papers on the topic "Constellations"

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Oliveira, B. M., M. S. Neves, F. P. Guiomar, M. C. R. Medeiros, and P. P. Monteiro. "Autoencoder-Optimized Geometric Constellation Shaping for Unamplified Coherent Optical Links." In CLEO: Science and Innovations. Washington, D.C.: Optica Publishing Group, 2022. http://dx.doi.org/10.1364/cleo_si.2022.sw4e.7.

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Using end-to-end deep learning, we experimentally demonstrate the optimized design of geometric constellation shaping for coherent unamplified links. A power budget gain of more than 2 dB is demonstrated for 8-ary constellations.
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Sermanoukian Molina, Iván, Lluís Montilla Rodríguez, David González Díez, Miquel Sureda Anfres, Jorge Mata Diaz, and Juan José Alins Delgado. "Mission analysis of nanosatellite constellations with OpenSatKit." In Symposium on Space Educational Activities (SSAE). Universitat Politècnica de Catalunya, 2022. http://dx.doi.org/10.5821/conference-9788419184405.006.

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CubeSat reliability is still considered an obstacle due to the sizeable fail rates generally attributed to the dead-on-arrival cases and early subsystem malfunctions. Thus, as CubeSats' primary purpose moves from technological demonstrations and university projects to missions where a significant risk of failure is not acceptable, an inexpensive method to emulate low Earth orbit constellations is being researched. The results presented have been developed in the framework of the PLATHON research project, which intends to develop a hardware-in-the-loop emulation platform for nanosatellite constellations with optical inter-satellite communication and ground-to-satellite links. Consequently, a crucial aspect of this project is to have a sufficiently precise orbital propagator with real-time manoeuvring control and graphical representation. NASA's OpenSatKit, a multi-faceted open-source platform with an inbuilt propagator known as 42, has been chosen to analyse the programme's feasibility in order to create a constellation testing bench. As an initial development of a software-in-the-loop application, the pre- processing of files has been automated; enhanced Attitude Determination and Control System manoeuvres have been added and configured through bidirectional socket interfaces, and the results format has been modified to be easily post-processed with MATLAB and Simulink
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Ji, Sijing, Di Zhou, Min Sheng, Dong Chen, Liang Liu, and Zhu Han. "Mega Satellite Constellations Analysis Regarding Handover: Can Constellation Scale Continue Growing?" In GLOBECOM 2022 - 2022 IEEE Global Communications Conference. IEEE, 2022. http://dx.doi.org/10.1109/globecom48099.2022.10001556.

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Rogers, Jen, Matthieu Poyade, and Frank Pollick. "Constellations of movement." In SIGGRAPH '17: Special Interest Group on Computer Graphics and Interactive Techniques Conference. New York, NY, USA: ACM, 2017. http://dx.doi.org/10.1145/3102163.3102168.

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Baumann, Karl, Benjamin Stokes, François Bar, and Ben Caldwell. "Designing in "constellations"." In PDC '16: The 14th Participatory Design Conference. New York, NY, USA: ACM, 2016. http://dx.doi.org/10.1145/2948076.2948083.

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Bollauf, Maiara F., and Oyvind Ytrehus. "Tiling of Constellations." In 2021 IEEE International Symposium on Information Theory (ISIT). IEEE, 2021. http://dx.doi.org/10.1109/isit45174.2021.9518129.

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Di Nisio, Nicola. "Simulating Heterogeneous Constellations." In SpaceOps 2012. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2012. http://dx.doi.org/10.2514/6.2012-1275219.

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Harris, Wayne, Rick Blake, Duncan Woods, Roger Thompson, and Johan Stjernevi. "Mission Planning for Constellations." In SpaceOps 2002 Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2002. http://dx.doi.org/10.2514/6.2002-t3-04.

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Lenzen, Christoph, Falk Mrowka, Andreas Spörl, and Rüdiger Klaehn. "Scheduling Formations and Constellations." In SpaceOps 2010 Conference: Delivering on the Dream (Hosted by NASA Marshall Space Flight Center and Organized by AIAA). Reston, Virigina: American Institute of Aeronautics and Astronautics, 2010. http://dx.doi.org/10.2514/6.2010-2002.

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Xu Wang, Rueywen Liu, Fan He, Tao Yang, and Bo Hu. "Blind identifiability of general constellations." In 2013 IEEE International Symposium on Circuits and Systems (ISCAS). IEEE, 2013. http://dx.doi.org/10.1109/iscas.2013.6572054.

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Reports on the topic "Constellations"

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BACCELLI, François, Sébastien CANDEL, Guy PERRIN, and Jean-Loup PUGET. Large Satellite Constellations: Challenges and Impact. Académie des sciences, March 2024. http://dx.doi.org/10.62686/3.

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The New Space Age (NewSpace) marks the advent of a new era in the use of space, characterized by the opening of space to new players, the use of new space technologies, new functionalities for satellites in orbit, and the development of satellite constellations, mainly in the fields of communications and Earth observation. These developments are underpinned by first-rate scientific and technological advances, as well as considerable public and private investment, in particular in the USA, China and, to a lesser extent, Europe. Fleets of small low- and medium-orbit satellites are replacing or complementing the large geostationary satellites that predominated in the previous period. Whereas space used to be reserved to a small number of states and major industrial groups, one is now witnessing the emergence of new space states, new industrial groups such as SpaceX or Amazon, and many start-ups. One also observes the emergence of companies with launching and satellite manufacturing capacities, which are also taking on the role of telecommunication operators and content producers. The most visible result of the deployment of these new space networks is the ability to provide high-speed, low-latency Internet connections to any point on the globe. Combined with Earth observation capabilities, these new communications resources also enable real-time action to be taken in any region, including those with no equipment other than terminals. In addition, these space networks are remarkably resilient compared with terrestrial networks. Geostrategic and military considerations combine with rapidly evolving business models to explain the massive investments currently being made in this domain. However, the lack of international regulation in the field is leading to a race to occupy orbits and frequencies, which has already had serious consequences for a whole range of scientific activities. These constellations have a potentially negative impact on astronomy in the visible and infrared optical domains, as well as on radio astronomy. They also raise a major problem in terms of space congestion, with an increase in the amounts of satellite debris resulting from launches or collisions between satellites, and the possibility of reaching a phase of chain reaction collisions. In addition, from an environmental point of view, the consequences of the proliferation of launches and uncontrolled re-entries into the atmosphere are equally worrying. What’s more, the lack of regulation in the field also leads to a loss of sovereignty, since these new satellite communication networks do not comply with any of the rules that states impose on terrestrial communication networks operating on their territories. A sustainable, global solution must be found to these problems, before major and potentially irreversible damage is inflicted on the planet’s environment, geostrategic balances, democracy, and science. While the Acad´emie des Sciences considers that France and Europe need to step up their scientific and industrial actions in this field in order to benefit from the remarkable advances of these new networks, and ultimately leverage the benefits of a resilient and secure communications network, the Acad´emie also recommends working in parallel to strengthen regulation of the field with the aim of assuring sustainable access to orbital and frequency resources, as well as protection for negatively impacted fields, foremost among which are astronomy and the environment.
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BACCELLI, François, Sébastien CANDEL, Guy PERRIN, and Jean-Loup PUGET. Grandes Constellations de Satellites : Enjeux et Impacts. Académie des sciences, March 2024. http://dx.doi.org/10.62686/2.

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Le nouvel âge spatial (NewSpace) marque l’avènement d’une ère nouvelle dans l’utilisation de l’espace caractérisée par une ouverture de l’espace à de nouveaux acteurs fondée sur de nouvelles technologies spatiales, par de nouvelles fonctionnalités pour les satellites mis en orbite et par le développement de constellations de satellites, principalement dans les domaines des communications et de l’observation de la Terre. Ces développements s’appuient sur des avancées scientifiques et technologiques de premier plan ainsi que sur des investissements publics et privés considérables, notamment aux États-Unis, en Chine et dans une moindre mesure en Europe. Des flottes de petits satellites en orbite basse ou moyenne viennent remplacer ou s’ajouter aux grands satellites géostationnaires qui prédominaient dans la phase précédente. Alors que l’espace était auparavant réservé à un petit nombre d’États et de grands groupes industriels, on observe actuellement l’émergence de nouveaux États spatiaux, de nouveaux groupes industriels comme SpaceX ou Amazon, ainsi que d’un grand nombre de jeunes pousses. On note l’émergence d’entreprises disposant de capacités de lancement, de fabrication de satellites et qui prennent également le rôle d’opérateurs de télécommunications et de producteurs de contenu. Le résultat le plus visible du déploiement de ces nouveaux réseaux spatiaux est de permettre des connexions Internet à haut débit et faible latence en tout point du globe terrestre. Combinés à des capacités d’observation de la Terre, ces nouveaux moyens de communications permettent aussi d’agir en temps-réel dans toute région, y compris dans celles dépourvues d’équipements autres que les terminaux. Ces réseaux spatiaux ont, de plus, de remarquables propriétés de résilience en comparaison des réseaux terrestres. Des considérations géostratégiques et militaires se combinent donc avec des modèles économiques en évolution rapide pour expliquer les investissements massifs en cours dans ce domaine. Toutefois, l’absence de régulation internationale du domaine conduit à une course pour l’occupation des orbites et des fréquences, course qui a déjà de graves conséquences sur tout un ensemble de domaines. Ces constellations auront potentiellement un impact très négatif sur l’astronomie dans le domaine optique visible et infrarouge ainsi que sur la radioastronomie. Elles posent aussi un problème majeur qui est celui de l’encombrement de l’espace avec l’augmentation du nombre des débris satellisés issus des lancements ou des collisions entre satellites et avec la possible atteinte d’une phase de collisions en chaîne. De plus, d’un point de vue environnemental, les conséquences d’une multiplication des lancements et des rentrées incontrôlées dans l’atmosphère sont, elles aussi, préoccupantes. Par ailleurs, cette absence de régulation du domaine conduit aussi à une perte de souveraineté puisque ces nouveaux réseaux de communications satellitaires n’appliquent aucune des règles que les États imposent aux réseaux de communications terrestres opérant sur leurs territoires. Une solution durable et globale doit être apportée à ces problèmes, avant que des dommages majeurs et potentiellement irréversibles soient infligés à l’environnement de la planète, aux équilibres géostratégiques, à la démocratie et à la science. Si l’Académie des sciences considère que la France et l’Europe doivent renforcer leurs actions scientifiques et industrielles dans ce domaine pour pouvoir bénéficier des avancées remarquables de ces nouveaux réseaux et disposer à terme d’un réseau de communication résilient et sécurisé, elle recommande aussi de travailler en parallèle au renforcement de la régulation du domaine dans le but de garantir un accès durable aux ressources orbitales et fréquentielles, ainsi qu’une protection des domaines négativement impactés, au premier rang desquels l’astronomie et l’environnement.
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Kusza, Kerri L., and Michael A. Paluszek. Intersatellite Links: Lower Layer Protocols for Autonomous Constellations. Fort Belvoir, VA: Defense Technical Information Center, November 2000. http://dx.doi.org/10.21236/ada451768.

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Voss, Hank D., and Jeff Dailey. EyePod-Mini: Constellations, Urban Launches and Buoy Landings. Ames (Iowa): Iowa State University. Library. Digital Press, January 2015. http://dx.doi.org/10.31274/ahac.9761.

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Melin, Alexander, K. S. Erwin, and VijaySekhar Chellaboina. Optical Dynamic Assignment for Low Earth Orbit Satellite Constellations. Fort Belvoir, VA: Defense Technical Information Center, September 2005. http://dx.doi.org/10.21236/ada439013.

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Dongarra, Jack, Thomas Sterling, Horst Simon, and Erich Strohmaier. High performance computing: Clusters, constellations, MPPs, and future directions. Office of Scientific and Technical Information (OSTI), June 2003. http://dx.doi.org/10.2172/813392.

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Ramos, Kim. Solar Power Constellations Implications for the United States Air Force. Fort Belvoir, VA: Defense Technical Information Center, April 2000. http://dx.doi.org/10.21236/ada388816.

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Santos, Michel, and Benjamin Shapiro. Improving the Coverage of Earth Targets by Maneuvering Satellite Constellations. Fort Belvoir, VA: Defense Technical Information Center, August 2007. http://dx.doi.org/10.21236/ada472910.

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Yu, Christopher C., and Daniel A. Newman. Comparison Study of Unequal Error Protection Methods for One-Dimensional Signal Constellations. Fort Belvoir, VA: Defense Technical Information Center, January 1995. http://dx.doi.org/10.21236/ada290386.

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Garrity, John, and Arndt Husar. Digital Connectivity and Low Earth Orbit Satellite: Constellations Opportunities for Asia and the Pacific. Asian Development Bank, April 2021. http://dx.doi.org/10.22617/wps210156-2.

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Satellite communication plays an important role in the global connectivity ecosystem. It connects rural and remote populations, provides backhaul connectivity to mobile cellular networks, and enables rapid communications for emergency and disaster responses. Low Earth orbit constellations may prove to be transformational to the connectivity landscape based on their global coverage and their suitability for areas not served by fiber optic cable networks. The Asian Development Bank’s developing member countries are well placed to benefit from this expansion of internet connectivity. It will be particularly valuable for small island developing states and landlocked developing countries with limited international bandwidth internet.
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