Artykuły w czasopismach na temat „Constellations”
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Deccia, Carlos M. A., David N. Wiese i Robert S. Nerem. "Using a Multiobjective Genetic Algorithm to Design Satellite Constellations for Recovering Earth System Mass Change". Remote Sensing 14, nr 14 (11.07.2022): 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, i Jinling Wang. "New Characteristics of Geometric Dilution of Precision (GDOP) for Multi-GNSS Constellations". Journal of Navigation 67, nr 6 (15.07.2014): 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 i Yasheng Zhang. "Deployment of Constellation with Different Inclinations Using the Nodal Precession and Thrust". Sensors 24, nr 2 (19.01.2024): 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 i 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 (30.09.2023): 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 i 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, nr 2 (30.12.2022): 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 i Chaoming Yun. "Low-Orbit Large-Scale Communication Satellite Constellation Configuration Performance Assessment". International Journal of Aerospace Engineering 2022 (11.03.2022): 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, i Christofer Laurell. "Tracing brand constellations in social media: the case of Fashion Week Stockholm". Journal of Fashion Marketing and Management: An International Journal 22, nr 1 (12.03.2018): 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, nr 3 (sierpień 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 i Luliang Jia. "Jamming Analysis between Non-Cooperative Mega-Constellations Based on Satellite Network Capacity". Electronics 13, nr 12 (14.06.2024): 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 i Honglei Yang. "Optimal Walker Constellation Design of LEO-Based Global Navigation and Augmentation System". Remote Sensing 12, nr 11 (6.06.2020): 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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Huang, Feijiang, Xiaochun Lu, Guangcan Liu, Liping Sun, Wang Sheng i Yingde Wang. "Improvement and Simulation of an Autonomous Time Synchronization Algorithm for a Layered Satellite Constellation". Mathematical Problems in Engineering 2013 (2013): 1–7. http://dx.doi.org/10.1155/2013/136301.
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Autonomous time synchronization for satellite constellations is a key technology to establish a constellation system time without the use of a ground station. The characteristics of satellite visibility time for layered satellite constellations containing geostationary earth orbit (GEO), inclined geosynchronous orbit (IGSO), and medium earth orbit (MEO) satellites are simulated by establishing a visible satellite model. Based on the satellite visible simulation results for a layered constellation, this study investigates the autonomous time synchronization algorithm that corresponds to the layered constellation structure, analyzes the main error of the time synchronization algorithm, and proposes methods to improve the characteristics of satellite movement in the constellation. This study uses an improved two-way time synchronization algorithm for autonomous time synchronization in the GEO-MEO satellite layer of a layered satellite constellation. The simulation results show that in a condition with simulation errors, the time synchronization precision of this improved algorithm can be controlled within 5 ns and used in high-precision autonomous time synchronization between layered satellite constellations.
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Swarsana, I. Putu, Gusti Ayu Ketut Suandewi i Ni Nyoman Kasih. "Karya Tari Sky Maps". Jurnal Igel : Journal Of Dance 4, nr 2 (30.08.2024): 54–62. http://dx.doi.org/10.59997/jijod.v4i2.3170.
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Sky Maps is a contemporary dance work inspired by constellations. A constellation is a collection of stars connected into a pattern in the sky. In addition to predicting luck, the uses of constellations include, among others, as a sign for planting time, and also used as navigation or directions for fishermen at sea. Constellations can also be used to determine the cardinal directions in each direction east, south, west, north have their own constellations. The constellations consist of the Scorpio constellation, the Kite constellation, the hunter constellation, and the thunder constellation. This work focuses on the shape of each constellation transformed into dance movements according to the imagination of the stylist with his creativity. The process of creating Sky Maps uses the method of Alma M. Hawkins in her book Creating Through Dance translated by Y. Sumandiyo Hadi into the book Creating Through Dance, which mentions three important stages in the formation of dance works, namely, the exploration stage, the experimental stage (improvisation), and the forming stage. The Sky Maps dance work is danced by eight male dancers who are packaged into a contemporary dance form with a duration of approximately 14 minutes. The Sky Maps dance work uses MIDI (Musical Instrument Digital Interface) music in which there are several electronic music instruments to support the atmosphere in this dance work. This work uses fantasy makeup with clothing that uses a white jumpsuit (strait full body) with a combination of navy blue and uses reflective strips (scothlite) which are arranged in such a way in one dancer's outfit. The effect of the reflector strip (scothlite) itself reflects light when illuminated and will emit light when in the dark. Besides having a uniqueness that lies in the idea and concept, another uniqueness also lies in the movement called Nyiku Lintang.
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Markiewicz, Tomasz G. "An Energy Efficient QAM Modulation with Multidimensional Signal Constellation". International Journal of Electronics and Telecommunications 62, nr 2 (1.06.2016): 159–65. http://dx.doi.org/10.1515/eletel-2016-0022.
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Abstract Packing constellations points in higher dimensions, the concept of multidimensional modulation exploits the idea drawn from geometry for searching dense sphere packings in a given dimension, utilising it to minimise the average energy of the underlying constellations. The following work analyses the impact of spherical shaping of the constellations bound instead of the traditional, hyper-cubical bound. Balanced constellation schemes are obtained with the N-dimensional simplex merging algorithm. The performance of constellations of dimensions 2, 4 and 6 is compared to the performance of QAM modulations of equivalent throughputs in the sense of bits transmitted per complex (two-dimensional) symbols. The considered constellations give an approximately 0:7 dB to 1 dB gain in terms of BER over a standard QAM modulation.
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Curzi, Giacomo, Dario Modenini i Paolo Tortora. "Large Constellations of Small Satellites: A Survey of Near Future Challenges and Missions". Aerospace 7, nr 9 (7.09.2020): 133. http://dx.doi.org/10.3390/aerospace7090133.
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Constellations of satellites are being proposed in large numbers; most of them are expected to be in orbit within the next decade. They will provide communication to unserved and underserved communities, enable global monitoring of Earth and enhance space observation. Mostly enabled by technology miniaturization, satellite constellations require a coordinated effort to face the technological limits in spacecraft operations and space traffic. At the moment in fact, no cost-effective infrastructure is available to withstand coordinated flight of large fleets of satellites. In order for large constellations to be sustainable, there is the need to efficiently integrate and use them in the current space framework. This review paper provides an overview of the available experience in constellation operations and statistical trends about upcoming constellations at the moment of writing. It highlights also the tools most often proposed in the analyzed works to overcome constellation management issues, such as applications of machine learning/artificial intelligence and resource/infrastructure sharing. As such, it is intended to be a useful resource for both identifying emerging trends in satellite constellations, and enabling technologies still requiring substantial development efforts.
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Kurtik, Gennady. "The Healing Goddess Gula as an Astral Goddess and Her Connection with the She-Goat and the Dog Constellations". Voprosy istorii estestvoznaniia i tekhniki 43, nr 1 (2022): 23. http://dx.doi.org/10.31857/s020596060019225-9.
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Gula the healing goddess is one of the best-known goddesses of Ancient Mesopotamia. The earliest mentions of Gula date back to the first half of the 3rd millennium BC. In the 2nd millennium BC the worship of Gula became widespread in Mesopotamia. Later on Gula becomes an astral goddess; she is associated with Lyra, one of the brightest constellations in the northern sky. This article discusses the astral aspects of the goddess Gula as a constellation and her connection with the Goat and the Dog constellations, located respectively in the modern Lyra and Hercules. The complicated mythological relationships that existed between Gula and these constellations changed with time. Gula was regarded as the goddess of the Goat constellation while the Dog was Gula’s sacred animal. The article reviews the main characteristics of Gula and the two above-mentioned constellations, reconstructed from cuneiform sources pertaining to different types and periods, particularly astral epithets associated with Gula and images on the glyptics and boundary stones (kudurru). The figures of the Gula, the Goat, and the Dog constellations are reconstructed. It is shown that, at the end of the 3rd millennium BC, of these three constellations only the Goat and the Dog were identified in the Mesopotamian sky. Gula acquired astral significance not before the second half of the 2nd millennium BC.
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Pajić, Marko, Mladen Veinović i Vladimir Orlić. "Complex signal constellations in cumulantsbased AMC: Statistics and performance". Telfor Journal 13, nr 2 (2021): 63–68. http://dx.doi.org/10.5937/telfor2102063p.
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In this paper various complex signal constellations are considered in the context of Automatic Modulation Classification (AMC) based on a higher-order normalized cumulants value. Most of the constellations have been addressed so far with fourth-order cumulants as AMC features only. The goal of this paper is to provide comparable values of sixth-order cumulants' statistics for complex signal constellations as well, while resolving ambiguity in constellation shapes addressed at the same time and directing towards the criterion for estimation of expected classification performance.
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Jordanova, L., L. Laskov i D. Dobrev. "Constellation and Mapping Optimization of APSK Modulations used in DVB-S2". Engineering, Technology & Applied Science Research 4, nr 5 (11.10.2014): 690–95. http://dx.doi.org/10.48084/etasr.496.
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This article represents the algorithms of APSK constellation and mapping optimization. The dependencies of the symbol error probability Ps on the parameters of the 16APSK and 32APSK constellations are examined and several options that satisfy the requirements to the minimum value of Ps are selected. Mapping optimization is carried out for the selected APSK constellations. BER characteristics of the satellite DVB-S2 channels are represented when using optimized and standard 16APSK and 32APSK constellations and a comparative analysis of the results achieved is made.
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Li, Feifei, Min Hu, Bin Che, Huaibin Yang i Yuancang Cheng. "Analysis of Initial Deployment Strategy for Low-Orbit Large-Scale Constellations". International Journal of Aerospace Engineering 2022 (8.11.2022): 1–10. http://dx.doi.org/10.1155/2022/5299611.
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With the development of commercial space technology, low-orbit large-scale satellite constellation has shown great development potential in communication services and military applications due to its advantages of low delay, strong signal, high coverage rate, fast communication rate, and low cost of mass production. It has become an urgent problem in the field of satellite constellations to study the perturbation evolution law of low-orbit large-scale constellation initialization and orbit maintenance, and how to maintain and control the deployment and initialization of low-orbit satellite constellations efficiently, economically, and stably. In this paper, the satellite motion law, constellation configuration evolution characteristics, and constellation initialization control strategy are analyzed considering the perturbation of earth’s nonspherical gravity and atmospheric drag under the orbit deviation of satellite orbit elements. Firstly, MonteCarlo simulation was used to simulate the deviation of satellite initial orbit elements, and the evolution law of ascending ascension point and phase angle of different constellations was analyzed and, secondly, establish the initialization phase constellation deployment and the ascending node right ascension deployment of mathematical equations, using Starlink constellation (V1.0-L3, 8) satellite TLE data; initialization of Leo constellation orbit plane is analyzed, by considering the orbit bias satellite simulation data; the same orbital plane satellite initialization phase deployment method is analyzed; finally, this paper provides some suggestions for the future deployment and maintenance control strategy of low-orbit constellation.
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Bielicki, Damian M. "Legal Aspects of Satellite Constellations". Air and Space Law 45, Issue 3 (1.06.2020): 245–64. http://dx.doi.org/10.54648/aila2020038.
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In recent years a few entrepreneurs proposed launching into space large fleets of satellites, consisting of hundreds of satellites, often referred to as ‘constellations’. Their role is to provide satellite services to the largest possible number of users on Earth. This article provides a review of key legal issues associated with satellite constellations, including responsibility and liability for potential damages caused by satellites being a part of a constellation, insurance, registration of space objects, allocation of radio frequencies and orbital slots, and space debris. satellite constellations, space law, space insurance, liability, space debris
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Ren, Shuyi, Xiaohua Yang, Ronglan Wang, Siqing Liu i Xiaojing Sun. "The Interaction between the LEO Satellite Constellation and the Space Debris Environment". Applied Sciences 11, nr 20 (13.10.2021): 9490. http://dx.doi.org/10.3390/app11209490.
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The wide application of satellite constellations in the field of space-based global communications and remote sensing has led to a substantial increase in small-satellite launch plans, a sharp increase in the density of space objects in low-Earth orbit (LEO), and a reduction in available orbit and frequency resources. This will further aggravate the trend of deterioration of the space debris environment. Taking the Starlink constellation as an example, this paper describes the influence of the constellation from the environmental debris flux of the satellite, the evaluation of the number of evasion maneuvers, the change of risk level, the success rate of post mission disposal (PMD) and the growth rate of space objects. The simulation results show that the collision risk of the Starlink constellation is related to the orbital parameters, and the higher success rate of post-mission disposal (PMD) can reduce the collision risk of the constellation. The large constellations increases the growth rate of space objects, and even if all the satellites are disposed of after the mission, the impact of constellations on the space environment can not be offset.
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Tian, Ke, Mayu Urata, Mamoru Endo, Katsuhiro Mouri, Takami Yasuda i Jien Kato. "Real-World Oriented Smartphone AR Supported Learning System Based on Planetarium Contents for Seasonal Constellation Observation". Applied Sciences 9, nr 17 (26.08.2019): 3508. http://dx.doi.org/10.3390/app9173508.
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A popular astronomical concept covered by projection learning programs in the planetarium is seasonal constellation. However, a planetarium’s learning environment is limited to virtual scenes, where learners can observe seasonal constellations, but there is a significant difference between reality and the learners’ imagination regarding constellations. It is important to create a real-world oriented observation learning environment for observing seasonal constellations. Augmented reality has proved to be a powerful tool for astronomical observation learning. In this paper, augmented reality (AR) contents and 2D contents are used to develop a smartphone-based learning system called the Real-World Oriented Smartphone AR Learning System (R-WOSARLS) for seasonal constellation observation, which is based on the planetarium contents of the planetarium of the Nagoya City Science Museum, for seasonal constellation learning. Two experiments were conducted to evaluate the usefulness, usability, and learner satisfaction of our system in university and junior high school, respectively. The results show that R-WOSARLS is an effective learning tool for constellation observation and learning, and it enhances learners’ motivation to pursue seasonal constellation learning. Moreover, R-WOSARLS could be a teaching tool not only to help students learn more than with traditional instruction, but also to stimulate their interest in astronomical phenomena outside of school.
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Meng, Qian, Yuan Zhuang i Shengying Li. "Implementation and Performance Analysis of Constellation Dynamic Selection in Multi-Constellation RAIM". Micromachines 13, nr 9 (2.09.2022): 1455. http://dx.doi.org/10.3390/mi13091455.
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Global navigation satellite system (GNSS) plays a crucial role in many fields, such as aerospace and transportation. Integrity is the measure of trust used in GNSS positioning especially in safety-critical applications. Advanced receiver autonomous integrity monitoring (ARAIM), taking full advantage of multi-constellation GNSS, shows huge potential to provide vertical navigation in civil aviation en route navigation and terminal approaches. However, the multi-constellation ARAIM also greatly exposes computational complexity and potential performance hazards in fault modes determination and fault-tolerant positioning. From the perspective of integrity risk control, rather than the pursuit of better positioning accuracy blindly for safety-critical applications, the concept of constellation dynamic selection is proposed and implemented in ARAIM and the performance analysis is discussed in this paper. Only the best two constellations which have the best vertical geometry performance are involved in ARAIM calculation anytime anywhere. The proposed method shows superiority in both integrity availability and computational complexity in both simulations and actual GNSS signal experiments. While the computational complexity is less than 10% of that using four constellations, 100% availability under LPV-200 criteria can be achieved in worldwide coverage experiment. The proposed method also overcomes the shortcomings of ARAIM with two fixed constellations and shows good robustness under depleted scenarios. Furthermore, the statistics results from observation stations proved the applicability and generality of the proposed method under current developing GNSS constellations.
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Winkelried, Jack, Christopher Ruf i Scott Gleason. "Spatial and Temporal Sampling Properties of a Large GNSS-R Satellite Constellation". Remote Sensing 15, nr 2 (5.01.2023): 333. http://dx.doi.org/10.3390/rs15020333.
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Using large constellations of smallsats, mission designers can improve sampling density and coverage. We develop performance metrics that characterize key sampling properties for applications in numerical weather prediction and optimize orbit design parameters of the constellation with respect to those metrics. Orbits are defined by a set of Keplerian elements, and the relationship between those elements and the spatial and temporal coverage metrics are examined in order to maximize global and zonal (latitude-dependent) coverage. Additional optimization is performed by dividing a constellation into multiple orbit planes. An iterative method can be applied to this design process to compare the performance of current and previous designs. The main objective of this work is the design of optimized configurations of satellites in low Earth orbiting constellations to maximize the spatial and temporal sampling and coverage provided by its sensors. The key innovations developed are a new cost function which measures the temporal sampling properties of a satellite constellation, and the use of it together with existing cost functions for spatial sampling to design satellite constellations that optimize performance with respect to both performance metrics.
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Forney, G. D. "Multidimensional constellations. II. Voronoi constellations". IEEE Journal on Selected Areas in Communications 7, nr 6 (1989): 941–58. http://dx.doi.org/10.1109/49.29616.
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Zhang, Jingrui, Yifan Cai, Chenbao Xue, Zhirun Xue i Han Cai. "LEO Mega Constellations: Review of Development, Impact, Surveillance, and Governance". Space: Science & Technology 2022 (30.07.2022): 1–17. http://dx.doi.org/10.34133/2022/9865174.
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The rapid development of Low Earth Orbit (LEO) mega constellations has significantly contributed to several aspects of human scientific progress, such as communication, navigation, and remote sensing. However, unrestrained deployment of constellations has also strained orbital resources and increased spacecraft congestion in LEO, which seriously affects the safety of in-orbit operations of many space assets. For the long-term and sustainable development of space activities in LEO regions, space environment stability must be maintained using more rational surveillance and governance mechanisms. This review contributes to the research gap and facilitates the development of LEO mega constellations. First, the current development of typical LEO mega constellations is reviewed, followed by the analysis of the impact of LEO mega constellations in terms of astronomical observation, spacecraft safety in orbit, and space environment evolution. Then, two main solutions to conduct the challenges raised by LEO mage constellations are elaborated: one is to ensure the safety operation of spacecraft using space surveillance infrastructures and space situational awareness technologies, and the other is to accelerate the deorbit of constellation satellites at the end of life based on postmission disposal and active removal methods. Finally, the future development and potential research directions of LEO mega constellations are prospected.
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Qin, Junxiang, Xuan Li, Xiaotian Ma, Xiye Guo i Jun Yang. "Cross-Domain Fusion Constellation Design of Communication, Navigation and Remote Sensing". Applied Sciences 13, nr 5 (28.02.2023): 3113. http://dx.doi.org/10.3390/app13053113.
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Low earth orbit (LEO) mega-constellations have once again triggered a wave of space-based system construction. On the one hand, LEO communication, LEO navigation, LEO remote sensing constellations and so on are proposed. On the other hand, with the continuous development of software-defined satellite and intelligent satellite technology, space-based systems are developing in the direction of multi-function, integration and cross-domain integration. The whole space-based system is no longer the traditional working mode of a single functional constellation, but a genral cross-domain fusion constellation (CDFC) system for complex tasks. Like the terrestrial global Internet, the space-based system will serve as a global infrastructure for integrating communication, navigation and remote sensing, that is, the intelligent space-based system, to provide services for the global demand. The traditional method of designing constellation for a certain type of function is no longer applicable to this type of constellation design. To solve this problem, this paper proposes a design and optimization method of cross-domain fusion constellation of communication, navigation and remote sensing based on reverse design. The paper optimizes the CDFC through resource coverage. Through experiments, we prove that the number of satellites in the CDFC can be reduced by 30.60% compared with the independent and combined constellations in each domain, and the coverage and service performance of the constellation can be improved. The cost can be reduced by 18.31% compared with the combined constellation. When the same number of satellites is used, the resource coverage of the cross-domain fusion constellation is increased by at least eight times.
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Zhang, Lei, i Bo Xu. "A Universe Light House — Candidate Architectures of the Libration Point Satellite Navigation System". Journal of Navigation 67, nr 5 (12.03.2014): 737–52. http://dx.doi.org/10.1017/s0373463314000137.
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In view of the shortcomings of existing satellite navigation systems in deep-space performance, candidate architectures which utilise libration point orbits in the Earth-Moon system are proposed to create an autonomous satellite navigation system for lunar missions. Three candidate constellations are systematically studied in order to achieve continuous global coverage for lunar orbits: the Earth-Moon L1,2 two-satellite constellation, the Earth-Moon L2,4,5 three-satellite constellation and the Earth-Moon L1,2,4,5 four-satellite constellation. After a thorough search for possible configurations, the latter two constellations are found to be the simplest feasible architectures for lunar navigation. Finally, an autonomous orbit determination simulation is performed to verify the autonomy of the system and two optimal configurations are obtained in a comprehensive consideration of coverage and autonomous orbit determination performance.
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Minchinton, Mark. "Constellations". Creative Approaches to Research 2, nr 2 (2009): 1–6. http://dx.doi.org/10.3316/car0202001.
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Coulehan, Jack. "Constellations". Annals of Internal Medicine 171, nr 10 (19.11.2019): 770. http://dx.doi.org/10.7326/m19-0934.
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Oury, Jean, i Danielle Sivadon. "Constellations". Chimères 79, nr 1 (2013): 124. http://dx.doi.org/10.3917/chime.079.0124.
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Treanor, Brian. "Constellations". American Catholic Philosophical Quarterly 80, nr 3 (2006): 369–92. http://dx.doi.org/10.5840/acpq20068036.
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SALTER, MARY JO. "CONSTELLATIONS". Yale Review 97, nr 1 (styczeń 2009): 31–32. http://dx.doi.org/10.1111/j.1467-9736.2009.00467.x.
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Petty, Audrey. "Constellations". Callaloo 19, nr 2 (1996): 415–21. http://dx.doi.org/10.1353/cal.1996.0058.
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Bell, Celia. "Constellations". Sewanee Review 126, nr 1 (2018): 59–68. http://dx.doi.org/10.1353/sew.2018.0007.
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Iwamura. "Constellations of Power, Constellations of Hope". Journal of Feminist Studies in Religion 31, nr 1 (2015): 131. http://dx.doi.org/10.2979/jfemistudreli.31.1.131.
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Matricciani, Emilio. "Geocentric Spherical Surfaces Emulating the Geostationary Orbit at Any Latitude with Zenith Links". Future Internet 12, nr 1 (18.01.2020): 16. http://dx.doi.org/10.3390/fi12010016.
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According to altitude, the orbits of satellites constellations can be divided into geostationary Earth orbit (GEO), medium Earth orbit (MEO), and low Earth orbit (LEO) constellations. We propose to use a Walker star constellation with polar orbits, at any altitude, to emulate the geostationary orbit with zenith paths at any latitude. Any transmitter/receiver will be linked to a satellite as if the site were at the equator and the satellite at the local zenith. This constellation design can have most of the advantages of the current GEO, MEO, and LEO constellations, without having most of their drawbacks. Doppler phenomena are largely minimized because the connected satellite is always seen almost at the local zenith. The extra free-space loss, due to the fixed pointing of all antennas, is at most 6 dBs when the satellite enters or leaves the service area. The connections among satellites are easy because the positions in the orbital plane and in adjacent planes are constant, although with variable distances. No steering antennas are required. The tropospheric propagation fading and scintillations are minimized. Our aim is to put forth the theoretical ideas about this design, to which we refer to as the geostationary surface (GeoSurf) constellation.
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Paolantonio, Santiago, i Beatriz Garcia. "Uranometría Argentina and the constellation boundaries". Proceedings of the International Astronomical Union 13, S349 (grudzień 2018): 505–9. http://dx.doi.org/10.1017/s1743921319000681.
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AbstractThe astronomical community accepts the division of the celestial sphere into 88 constellations, according to what was established by the IAU. In the first Assembly of 1922 the use of Latin names for constellations and their abbreviations was resolved. The pending issue of the limits of the constellations was discussed in the next meeting and Eugène Delporte had the responsibility for the complete theoretical demarcation. For his work, Delporte took into account what was done half a century earlier in the famous work Uranometría Argentina, published in 1877 and 1879, under the supervition of Benjamin Gould. In ths presentation we discusse the situation at the moment when the constellation boundaries were proposed using arcs of RA circles and parallels of declination, choosing them in such a way that they did not deviate too much from those used in the most important celestial atlas of the time, and minimizing the changes of which constellations stars would belong to.
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Mulsow, Martin. "Qu’est-ce qu’une constellation philosophique? Propositions pour une analyse des réseaux intellectuels". Annales. Histoire, Sciences Sociales 64, nr 1 (luty 2009): 79–109. http://dx.doi.org/10.1017/s0395264900028584.
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RésuméL’analyse des constellations philosophiques se concentre sur les relations « épaisses » entre les personnes, les théories, les problèmes et les documents. Elle est fondée sur l’idée que seule l’analyse de ces relations, et pas des éléments pris séparément, peut rendre compte des accomplissements philosophiques et des développements des personnes, des idées et des théories. Cet article essaie d’établir l’analyse de constellations, mise au point par Dieter Henrich pour son étude des débuts de l’idéalisme allemand, comme méthode générale pertinente pour d’autres périodes de l’histoire de la philosophie. Il engage alors un dialogue avec d’autres méthodes dans les sciences humaines, comme celles proposées par Foucault, Elias, Chartier, Collins, etc. Il fournit quelques exemples de constellations philosophiques, du cercle de Comenius auXVIIesiècle à une « crypto-constellation » de penseurs clandestins duXVIIIesiècle.
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Wang, Sixin, Xiaomei Tang, Jingyuan Li, Xinming Huang, Jiyang Liu i Jian Liu. "Navigation Resource Allocation Algorithm for LEO Constellations Based on Dynamic Programming". Remote Sensing 16, nr 12 (19.06.2024): 2231. http://dx.doi.org/10.3390/rs16122231.
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Navigation resource allocation for low-earth-orbit (LEO) constellations refers to the optimal allocation of navigational assets when the number and allocation of satellites in the LEO constellation have been determined. LEO constellations can not only transmit navigation enhancement signals but also enable space-based monitoring (SBM) for real-time assessment of GNSS signal quality. However, proximity in the frequencies of LEO navigation signals and SBM can lead to significant interference, necessitating isolated transmission and reception. This separation requires that SBM and navigation signal transmission be carried out by different satellites within the constellation, thus demanding a strategic allocation of satellite resources. Given the vast number of satellites and their rapid movement, the visibility among LEO, medium-earth-orbit (MEO), and geostationary orbit (GEO) satellites is highly dynamic, presenting substantial challenges in resource allocation due to the computational intensity involved. Therefore, this paper proposes an optimal allocation algorithm for LEO constellation navigation resources based on dynamic programming. In this algorithm, a network model for the allocation of navigation resources in LEO constellations is initially established. Under the constraints of visibility time windows and onboard transmission and reception isolation, the objective is set to minimize the number of LEO satellites used while achieving effective navigation signal transmission and SBM. The constraints of resource allocation and the mathematical expression of the optimization objective are derived. A dynamic programming approach is then employed to determine the optimal resource allocation scheme. Analytical results demonstrate that compared to Greedy and Divide-and-Conquer algorithms, this algorithm achieves the highest resource utilization rate and the lowest computational complexity, making it highly valuable for future resource allocation in LEO constellations.
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Kurtik, Gennady E. "On the origin of the 12 zodiac constellation system in ancient Mesopotamia". Journal for the History of Astronomy 52, nr 1 (luty 2021): 53–66. http://dx.doi.org/10.1177/0021828620980544.
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This article pursues two main goals: (1) to reconstruct the history of the 12 zodiac constellation system in the astronomy of ancient Mesopotamia; (2) to reveal traces of this system directly in cuneiform texts. Among the most important circumstances led to appearance of this system: (1) development of ideas about the band of zodiac constellations, including—according to MUL.APIN—the total of 18 (or 17) constellations; (2) usage of the schematic year, containing 12 months, 30 days each, and (3) development of ideas about mathematical or uniform zodiac, subdivided into 12 equal parts, 30° each. A sequence of the so-called Normal stars singled out in the zodiacal band is an additional important source shedding light on the history of the Mesopotamian zodiac. The designations of Normal stars adopted in Astronomical diaries and other texts indicate that the system of 18 constellations was used in Mesopotamia until the end of cuneiform civilization. This means that in the second half of the first millennium BC the system of 18 constellations, adopted in MUL.APIN, and the system of 12 zodiacal constellations, borrowed from Babylonians by Greek astronomers, were used in parallel. It is also shown in the article that the system of 12 zodiac constellations was used in magical and astrological text BRM 4.20, dated back approximately to the last third of the fourth century BC.
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Xu, Xiaohua, Yi Han, Jia Luo, Jens Wickert i Milad Asgarimehr. "Seeking Optimal GNSS Radio Occultation Constellations Using Evolutionary Algorithms". Remote Sensing 11, nr 5 (8.03.2019): 571. http://dx.doi.org/10.3390/rs11050571.
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Given the great achievements of the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) mission in providing huge amount of GPS radio occultation (RO) data for weather forecasting, climate research, and ionosphere monitoring, further Global Navigation Satellite System (GNSS) RO missions are being followingly planned. Higher spatial and also temporal sampling rates of RO observations, achievable with higher number of GNSS/receiver satellites or optimization of the Low Earth Orbit (LEO) constellation, are being studied by high number of researches. The objective of this study is to design GNSS RO missions which provide multi-GNSS RO events (ROEs) with the optimal performance over the globe. The navigation signals from GPS, GLONASS, BDS, Galileo, and QZSS are exploited and two constellation patterns, the 2D-lattice flower constellation (2D-LFC) and the 3D-lattice flower constellation (3D-LFC), are used to develop the LEO constellations. To be more specific, two evolutionary algorithms, including the genetic algorithm (GA) and the particle swarm optimization (PSO) algorithm, are used for searching the optimal constellation parameters. The fitness function of the evolutionary algorithms takes into account the spatio-temporal sampling rate. The optimal RO constellations are obtained for which consisting of 6–12 LEO satellites. The optimality of the LEO constellations is evaluated in terms of the number of global ROEs observed during 24 h and the coefficient value of variation (COV) representing the uniformity of the point-to-point distributions of ROEs. It is found that for a certain number of LEO satellites, the PSO algorithm generally performs better than the GA, and the optimal 2D-LFC generally outperforms the optimal 3D-LFC with respect to the uniformity of the spatial and temporal distributions of ROEs.
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Li, Xin, Xingxing Li, Fujian Ma, Yongqiang Yuan, Keke Zhang, Feng Zhou i Xiaohong Zhang. "Improved PPP Ambiguity Resolution with the Assistance of Multiple LEO Constellations and Signals". Remote Sensing 11, nr 4 (17.02.2019): 408. http://dx.doi.org/10.3390/rs11040408.
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The fusion of low earth orbit (LEO) constellation and Global Navigation Satellite Systems (GNSS) can increase the number of visible satellites and optimize spatial geometry, which is expected to improve the performance of precise point positioning (PPP) ambiguity resolution (AR). In addition, the multi-frequency signals of LEO satellites can bring a variety of observation combinations, which is potential to further improve the efficiency of PPP AR. In this contribution, multi-frequency PPP AR was achieved with the augmentation of different LEO constellations. Three types of LEO constellations were designed with 60, 192, and 288 satellites. Moreover, the corresponding observation data were simulated with the GNSS observations over the ground stations. The LEO constellations were designed to transmit navigation signals on three frequencies: L1, L2, and L5 at 1575.42, 1227.6, and 1176.45 MHz, respectively, which are consistent with the GPS signals. For PPP AR, the uncalibrated phase delay (UPD) products of GNSS and LEO were estimated first. Furthermore, the quality of UPD products was also analyzed. The research findings show that the performance of estimated LEO UPD is comparable to that of GNSS UPD. Based on the UPD products, LEO-augmented multi-GNSS PPP AR can be achieved. Numerous results show that the performance of single-system and multi-GNSS PPP AR can be significantly improved by introducing the LEO constellations. The augmentation performance is more remarkable in the case of increasing LEO satellites. The time to first fix (TTFF) of the GREC fixed solution can be shortened from 7.1 to 4.8, 1.1, and 0.7 min, by introducing observations of 60-, 192-, and 288-LEO constellations, respectively. The positioning accuracy of multi-GNSS fixed solutions is also improved by about 60%, 80%, and 90% with the augmentation of 60-, 192-, and 288-LEO constellations, respectively. Compared to the dual-frequency solutions, the triple-frequency LEO-augmented PPP fixed solution presents a better performance. The TTFF of GREC fixed solutions is shortened to 33 s with the augmentation of 288-LEO constellation under the triple-frequency environment. It is worth indicating that the 288-satellite LEO-only PPP AR was conducted in dual-frequency and triple-frequency modes, respectively. The averaged TTFFs of both modes are 71.8 s and 55.2 s, respectively. It indicates that LEO constellation with 288 satellites is capable of achieving high-precision positioning independently and shows an even better performance than GNSS-only solutions.
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Adair, Kathleen E., Kelly R. Ylitalo, Jeffrey S. Forsse, LesLee K. Funderburk i Rodney G. Bowden. "Metabolic Constellations, Clusters, and Renal Function: Findings from the 2013–2018 National Health and Nutrition Examination Surveys". Life 11, nr 9 (30.08.2021): 904. http://dx.doi.org/10.3390/life11090904.
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Metabolic syndrome (MetS) is associated with decreased renal function and chronic kidney disease (CKD). To date, no research regarding the sixteen possible constellations resulting in the diagnosis of MetS has been elucidated. The purpose of this study is to report renal function in sixteen metabolic constellations grouped into four metabolic clusters. Individuals (n = 2767; representing 86,652,073 individuals) from the 2013–2018 National Health and Nutrition Examination Surveys who met the criteria for MetS were included. Sixteen possible constellations of three or more risk factors were analyzed for renal function. Four metabolic clusters representing MetS with hyperglycemia (Cluster I), MetS with hypertension (Cluster II), MetS with hyperglycemia and hypertension (Cluster III), or MetS with normoglycemia and normotension (Cluster IV) were assessed for renal function and CKD status. Cluster III had the highest odds of CKD (OR = 2.57, 95% CL = 1.79, 3.68). Clusters II and III had the lowest renal function and were not different from one another (87.82 and 87.28 mL/min/1.73 m2, p = 0.71). The constellation with the lowest renal function consisted of hypertension, high triglycerides, and a large waist circumference (82.86 mL/min/1.73 m2), whereas the constellation with the highest renal function consisted of hyperglycemia, low HDL, and a large waist circumference (107.46 mL/min/1.73 m2). The sixteen constellations of MetS do not have the same effects on renal function. More research is needed to understand the relationship between the various iterations of MetS and renal function.
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Simpson, H. Austin. "Regulating Science Fiction: the Regulatory Deficiencies in a Rapidly Growing Commercial Space Industry". Journal of Air Law and Commerce 87, nr 4 (2022): 759. http://dx.doi.org/10.25172/jalc.87.4.4.
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a. This Comment explores the deficiencies of the legal framework governing commercial space with the advent of satellite mega-constellations. The scope and size of these so-called constellations are completely unlike anything the space industry has contemplated since the first rocket was launched into orbit. Moreover, these constellations are an extremely new phenomenon—the prime movers in the industry are just beginning to create these massive man-made wonders in space. As such, the legal framework was designed around space operations that are much smaller in scope. That framework has struggled to keep pace with the rapidly growing commercial space industry generally and the constellation industry specifically. This Comment begins by explaining some of the pressing concerns regarding space exploration and specifically addresses the growing concerns roused by the addition of tens of thousands of small satellites primarily within Earth’s lower orbit. It then lays out the relevant regulatory framework. It discusses how that framework has operated in the past, how it has been applied to commercial satellite constellations so far, and how it has changed over the past few years. Finally, this Comment discusses the reality of satellite constellation regulation—that it is being largely self-regulated by the industry. It analyzes the benefits and negative aspects of that reality, and it concludes with a proposal on how to move forward with space regulation such that the continued viability of space exploration and the protection of relevant stakeholders will be assured well into the future.
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Khramov, D. O., i O. L. Volosheniuk. "Analysis of the state of the art and the trends in the development of the target characteristics of orbital constellations of small agriculture-oriented Earth re-mote sensing spacecraft". Technical mechanics 2023, nr 4 (14.12.2023): 31–39. http://dx.doi.org/10.15407/itm2023.04.031.
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The goal of this paper is to assess the existing capabilities of orbital constellations of agriculture-oriented Earth remote sensing spacecraft and the prospects for their development in the nearest future. The paper analyzes the state of the art and the trends in the development of modern orbital constellations of private companies’ small Earth remote sensing satellites used in solving agricultural problems. Important sources of information in the space industry, such as NewSpace Index, Gunter's Space Page, and WMO OSCAR, were analyzed. 52 constellations of spacecraft for optical multispectral and hyperspectral, thermal, and microwave (radar) imaging are considered. It is shown that they provide a survey frequency of several times a day. The minimum spatial resolution of optoelectronic surveillance sensors is 1 m (in the panchromatic channel). This allows one to solve problems at an intrafield level, quasi-continuously monitor the plant condition, and use spectral patterns and texture features in solving applied agricultural problems. All the constellations of radar satellites use the X-band, except for the radars of the Spacety constellation (China), which use the C-band. It is shown that the number of constellations of small remote sensing spacecraft in the period 2021–2025 is to be increased by more than three times compared to the period 2016–2020. The number of countries developing constellations of Earth remote sensing satellites has increased significantly. The leading countries and companies in the number and size of constellations are the United States and China and Planet (USA) and Chang Guang Satellite Technology Corporation (China), respectively. Private developers are particularly interested in thermal infrared imaging and hyperspectral optical imaging data. A new line in the private space industry, which is expected to facilitate the solution of agricultural problems, is the deployment of constellations of small meteorological satellites.
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Li, Xingxing, Hongbo Lv, Fujian Ma, Xin Li, Jinghui Liu i Zihao Jiang. "GNSS RTK Positioning Augmented with Large LEO Constellation". Remote Sensing 11, nr 3 (22.01.2019): 228. http://dx.doi.org/10.3390/rs11030228.
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It is widely known that in real-time kinematic (RTK) solution, the convergence and ambiguity-fixed speeds are critical requirements to achieve centimeter-level positioning, especially in medium-to-long baselines. Recently, the current status of the global navigation satellite systems (GNSS) can be improved by employing low earth orbit (LEO) satellites. In this study, an initial assessment is applied for LEO constellations augmented GNSS RTK positioning, where four designed LEO constellations with different satellite numbers, as well as the nominal GPS constellation, are simulated and adopted for analysis. In terms of aforementioned constellations solutions, the statistical results of a 68.7-km baseline show that when introducing 60, 96, 192, and 288 polar-orbiting LEO constellations, the RTK convergence time can be shortened from 4.94 to 2.73, 1.47, 0.92, and 0.73 min, respectively. In addition, the average time to first fix (TTFF) can be decreased from 7.28 to 3.33, 2.38, 1.22, and 0.87 min, respectively. Meanwhile, further improvements could be satisfied in several elements such as corresponding fixing ratio, number of visible satellites, position dilution of precision (PDOP) and baseline solution precision. Furthermore, the performance of the combined GPS/LEO RTK is evaluated over various-length baselines, based on convergence time and TTFF. The research findings show that the medium-to-long baseline schemes confirm that LEO satellites do helpfully obtain faster convergence and fixing, especially in the case of long baselines, using large LEO constellations, subsequently, the average TTFF for long baselines has a substantial shortened about 90%, in other words from 12 to 2 min approximately by combining with the larger LEO constellation of 192 or 288 satellites. It is interesting to denote that similar improvements can be observed from the convergence time.
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Bucur, Doina. "The network signature of constellation line figures". PLOS ONE 17, nr 7 (28.07.2022): e0272270. http://dx.doi.org/10.1371/journal.pone.0272270.
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In traditional astronomies across the world, groups of stars in the night sky were linked into constellations—symbolic representations rich in meaning and with practical roles. In some sky cultures, constellations are represented as line (or connect-the-dot) figures, which are spatial networks drawn over the fixed background of stars. We analyse 1802 line figures from 56 sky cultures spanning all continents, in terms of their network, spatial, and brightness features, and ask what associations exist between these visual features and culture type or sky region. First, an embedded map of constellations is learnt, to show clusters of line figures. We then form the network of constellations (as linked by their similarity), to study how similar cultures are by computing their assortativity (or homophily) over the network. Finally, we measure the diversity (or entropy) index for the set of constellations drawn per sky region. Our results show distinct types of line figures, and that many folk astronomies with oral traditions have widespread similarities in constellation design, which do not align with cultural ancestry. In a minority of sky regions, certain line designs appear universal, but this is not the norm: in the majority of sky regions, the line geometries are diverse.
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Ren, Jing, Dan Sun, Deng Pan, Mingtao Li i Jianhua Zheng. "Cost-Efficient LEO Navigation Augmentation Constellation Design under a Constrained Deployment Approach". International Journal of Aerospace Engineering 2021 (4.09.2021): 1–18. http://dx.doi.org/10.1155/2021/5042650.
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The advantages of the Low Earth Orbit (LEO) satellite include low-latency communications, shorter positioning time, higher positioning accuracy, and lower launching, building, and maintenance costs. Thus, the introduction of LEO satellite constellation as a regional navigation augmentation system for the current navigation constellations is studied in this paper. To achieve the navigation performance requirement with the least system cost, a synthetic approach is presented to design and deploy a cost-efficient LEO navigation augmentation constellation over 108 key cities. To achieve lower construction costs, the constellation is designed to be deployed by constrained piggyback launches, which brings additional complexity to the constellation design. Two optimization models with discrete and continuous performance indices are established. They are solved by the genetic algorithm and differential evolution algorithm, and both Walker and Flower constellations are adopted. Results for 77 and 70 satellites are obtained. During the construction phase, a synthesis procedure containing five impulses is proposed by utilizing natural drift under J 2 perturbation. This work presents a method for designing the optimal LEO navigation constellation under a constraint deployment approach with the lowest construction cost and a strategy to deploy the constellation economically.
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Zhodzishskiy, A. I., S. K. Zhidkova i D. N. Nagornykh. "Construction of a Unified Ground-based Control Complex for a Multi-satellite ERS Constellation". Rocket-Space Device Engineering and Information Systems 7, nr 4 (2020): 14–21. http://dx.doi.org/10.30894/issn2409-0239.2020.7.4.14.21.
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Taking into account the increasing number of spacecraft the further development of the Russian ground-based control systems (GCS) for Earth remote sensing spacecraft requires new approaches to solving the problems of increasing the efficiency and global control of these spacecraft. The paper considers the possibility of creating a unified ERS GCS (ERS UGCS), including the existing ERS GCS and providing control capabilities for promising, newly created ERS SC. As part of the ERS UGCS, a single control center should be created that provides modeling, planning, analysis and control of future and existing spacecraft constellations and ground-based facilities. Using international experience in managing multi-satellite constellations and implementing our own experience in creating special software for the control centers, for new spacecraft constellations, it is proposed to automate the tasks of a typical regular control cycle, automate periodic maintenance operations of the spacecraft and localize emergency situations. With the aim of automating control processes, the creation of a digital mathematical model of the orbital constellation and ground-based facilities is also proposed for Russian remote sensing constellations. A model that takes into account and describes the spatio-temporal position of the spacecraft constellations, the location of the GCS, ground based data receiving processing and distribution complexes, multifunctional relay stations (MFRS), their technical condition, composition and performance should form the basis for the implementation of end-to-end planning of the main control operations and the targeted use of multi-satellite constellations.
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Lucia, Brandon, Brad Denby, Zachary Manchester, Harsh Desai, Emily Ruppel i Alexei Colin. "Computational Nanosatellite Constellations". GetMobile: Mobile Computing and Communications 25, nr 1 (15.06.2021): 16–23. http://dx.doi.org/10.1145/3471440.3471446.
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As rocket launch cadences increase, access to space rises dramatically - setting the stage for the next space industry surge. New, smaller, and less expensive satellites - now "nanosatellites" - can be deployed en masse to form constellations of hundreds, thousands, or even tens of thousands of devices [27, 40, 41, 16, 17, 18, 43]. A constellation of nanosatellites equipped with sensors (e.g., visual or hyperspectral cameras, particle detectors, or magnetometers) and radios provides a first-time opportunity for orbital swarm sensing to synthesize data from the unique vantage point of low-Earth orbit (LEO).