46,526 Hits in 3.9 sec

Line and Plane Cover Numbers Revisited [article]

Therese Biedl, Stefan Felsner, Henk Meijer, Alexander Wolff
2019 arXiv   pre-print
When edges are also required to be covered, the corresponding numbers ρ^1_d(G) and ρ^2_3(G) are called the (strong) line cover number and the (strong) plane cover number.  ...  For a given graph G, the minimum such number (over all drawings in dimension d ∈{2,3}) is called the d-dimensional weak line cover number and denoted by π^1_d(G).  ...  We thank the organizers and other participants, in particular Will Evans, Sylvain Lazard, Pavel Valtr, Sue Whitesides, and Steve Wismath.  ... 
arXiv:1908.07647v1 fatcat:cx3c4e2wd5expissu44xevs4mq

Optimal Satellite LEO Constellation Design Based on Global Coverage in One Revisit Time

Peng Zong, Saeid Kohani
2019 International Journal of Aerospace Engineering  
For example, six satellites in the constellation cover the whole Earth within one revisit time and all the data are collected by two Earth stations for keeping continuous coverage.  ...  This paper presents a globe coverage of constellation satellite in one revisit and the regional coverage at defined latitude.  ...  In order to completely cover the ground in a revisit, designers can use the charts, tables, and figure provided in this report to choose number of satellites in the constellation and inclinations, further  ... 
doi:10.1155/2019/4373749 fatcat:xtrhjcxvv5ebxjwq2xaayopdga

Satellite Constellation Orbit Design Optimization with Combined Genetic Algorithm and Semianalytical Approach

Tania Savitri, Youngjoo Kim, Sujang Jo, Hyochoong Bang
2017 International Journal of Aerospace Engineering  
This paper focuses on maximizing the percent coverage and minimizing the revisit time for a small satellite constellation with limited coverage.  ...  A multiobjective optimization study is conducted in this study with percent coverage and revisit time as the two main parameters to analyze the performance of the constellation.  ...  Red line: ground track of sat #1, pink line: ground track of sat #2, and blue line: ground track of sat #3. Red star: area covered by sat #1 and blue triangle: area covered by sat #3.  ... 
doi:10.1155/2017/1235692 fatcat:mwpoksv6yjdo3lrx2kgnxqh3ya

A New Constellation Configuration Scheme for Communicating Architecture in Cislunar Space

Ming Xu, Jinlong Wang, Shengli Liu, Shijie Xu
2013 Mathematical Problems in Engineering  
The revisiting intervals between the successive revisits on specified points by the constellation are demonstrated both on the geographical maps of the Earth and the Moon, with a consideration of equatorial  ...  inclinations with respect to the Earth-Moon orbital plane.  ...  This constellation is weak in covering some longitude lines located near 150 ∘ W and 150 ∘ E. The discontinuous communications are interrupted by some intervals less than 2 hours.  ... 
doi:10.1155/2013/864950 fatcat:b7ai2wdzxbhufp7db6xftqo7ru

Potential of a SAR Small-Satellite Constellation for Rapid Monitoring of Flood Extent

Natsumi Kitajima, Rie Seto, Dai Yamazaki, Xudong Zhou, Wenchao Ma, Shinjiro Kanae
2021 Remote Sensing  
Constellations of small satellites equipped with synthetic aperture radar (SAR) payloads can realize observations in short time intervals independently from daylight and weather conditions and this technology  ...  In this study, we propose an unprecedented method for investigating how flood extents would be temporally and spatially observed with a SAR small-satellite constellation and for evaluating that observation  ...  time, and maximum revisit time when the number of satellites (T) is given.  ... 
doi:10.3390/rs13101959 fatcat:6wnwsnx5uvcuvo37t74gry4qvi

Design of Satellite Orbits & Constellations for Global Coverage

Pengfei Zeng, Yun Liang, Yao Wang, Li Huang, Feng Huang, Yilei Lin, Jiawei Wu, Shu Li, Zhijia Chen
2018 DEStech Transactions on Computer Science and Engineering  
Based on GEO, LEO and Molniya satellite, we designed a mixed constellation to implement it and made simulations to evaluate its function.  ...  To make this system real, we need to provide reliable communication method for global, especially Arctic and Equator area where has varied weather and complex environment.  ...  The number of LEO orbital planes and the number of satellites on a single orbit are designed as follows.  ... 
doi:10.12783/dtcse/icmsie2017/18672 fatcat:7mta74lkrzc3bhknyalj2z7g4m

Airborne GNSS-R: A key enabling technology for environmental monitoring

Adrian Perez-Portero, Joan FRANCESC Munoz-MARTIN, Hyuk Park, Adriano Camps
2021 IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing  
In this work, the potential of using hosted GNSS-R payloads on commercial aircraft is explored as an alternative and cost-effective means to achieve a very high resolution and a very low revisit time for  ...  LEO constellations of small satellites have the same coverage with improved spatial resolution and revisit times by using data fusion techniques.  ...  It is clear from Fig. 5 that a higher percentage of land is covered by planes, but more accurate data is required to obtain this number. B.  ... 
doi:10.1109/jstars.2021.3076003 fatcat:7lw4isvmzbdb7ok7vzgamyxwvi

ANZ volume 43 issue 1 Cover and Back matter

2001 ANZIAM journal (Print)  
The paper should be of a non-absorbent quality so that the ink does not spread and produce fuzzy lines.  ...  Biswas and T. S. Santhanam, "Coherent states of para-Bose oscillators", J. Austral. Math. Soc. Sen 5 22(1980)210-217. [3] E. M. Casling, "Slender planing surfaces", Ph. D.  ... 
doi:10.1017/s1446181100011354 fatcat:dr3ipo4gcjhwnetb5qqoxroowe

A Semi-Analytical Method for Calculating Revisit Time for Satellite Constellations with Discontinuous Coverage [article]

Nicholas H. Crisp, Sabrina Livadiotti, Peter C.E. Roberts
2018 arXiv   pre-print
This paper presents a unique approach to the problem of calculating revisit time metrics for different satellite orbits, sensor geometries, and constellation configurations with application to early lifecycle  ...  Using the developed method, extensive plots of maximum revisit time are presented for varying altitude, inclination, target latitudes, sensor capabilities, and constellation configuration, providing valuable  ...  Acknowledgements This work was supported by the Doctoral Training Partnership (DTP) between The University of Manchester and the UK Engineering and Physical Sciences Research Council (EPSRC) under grant  ... 
arXiv:1807.02021v1 fatcat:v324vgpazzcdpeb2rzdv4kc6di

How can we distinguish transient pulsars from SETI beacons? [article]

James Benford
2010 arXiv   pre-print
Bandwidth, pulse width and frequency may be distinguishing features. Such transients could be evidence of civilizations slightly higher than ourselves on the Kardashev scale.  ...  They all cover the same fraction of the sky, the galactic disk, but have very different dwell and revisit times.  ...  A Beacon builder choosing values of θ and a sky fraction F to illuminate gives lines of constant duty cycle ratio (dwell time/revisit time, τ d /τ r ) for the Beacon observer.  ... 
arXiv:1003.5938v2 fatcat:yhyh74m63ncpfipdanumdy7jqi

Multi-Agent Coverage in Urban Environments [article]

Shivang Patel and Senthil Hariharan and Pranav Dhulipala and Ming C Lin and Dinesh Manocha and Huan Xu and Michael Otte
2020 arXiv   pre-print
We study multi-agent coverage algorithms for autonomous monitoring and patrol in urban environments.  ...  density, high density] x [short buildings, tall buildings], and for team sizes ranging from 2 to 25 agents.  ...  Covered (%) Number of Visits Number of Agents Number of visits Ave.  ... 
arXiv:2008.07436v1 fatcat:x5y3ujshzzfczdsmavbj7q7dy4

Joint PAZ & TanDEM-X Mission Interferometric Experiments: Interoperability and Products

Alberto Alonso-Gonzalez, Nuria Gimeno Martinez, Irena Hajnsek, Patricia Cifuentes Revenga, Maria Jose Gonzalez-Bonilla, Christo Grigorov, Achim Roth, Ursula Marschalk, Nuria Casal Vazquez, Juan Manuel Cuerda Munoz, Marcos Garcia Rodriguez
2021 IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing  
The geometric accuracy and the interferometric performance when combining both sensors are investigated, considering different acquisition parameters and land cover types.  ...  Since both platforms are almost identical and they were launched in the same orbital plane, comparable images of the same area under the same geometry may be regularly acquired by both systems.  ...  be captured (e.g monitoring agricultural phenological changes, changes due to snow cover, any kind of deformation studies and many more).  ... 
doi:10.1109/jstars.2021.3084401 fatcat:ik4mofnw3vg35agbxvlox4z5cq

Optimization of Reconfigurable Satellite Constellations Using Simulated Annealing and Genetic Algorithm

Sung Paek, Sangtae Kim, Olivier de Weck
2019 Sensors  
Ongoing research on observation scheduling and constellation management will extend the ReCon applications to radar imaging and radio occultation beyond visible wavelengths and nearby spectrums.  ...  Two heuristic methods, simulated annealing (SA) and genetic algorithm (GA), are widely used for discrete combinatorial problems and therefore used in this study to benchmark against a gradient-based method  ...  and GOM revisit time (to a lesser extent) decrease when the number of planes decreases and the number of satellites per plane increases  ... 
doi:10.3390/s19040765 fatcat:cxxnjoyyxbd5de34fqvmixfitm

ANZ volume 25 issue 4 Cover and Back matter

1984 The Journal of the Australian Mathematical Society Series B Applied Mathematics  
Casling, "Slender planing surfaces". Ph. D. Thesis. University of Adelaide. 1978. [5] R. H. Day. "Adaptive processes and economic theory", in Adaptive economic models (eds. R. H. Day and T.  ...  The paper should be of a non-absorbent quality so that the ink does not spread and produce fuzzy lines.  ... 
doi:10.1017/s0334270000004173 fatcat:3qayejiwtnburdaoj5vvkz375u

Intersecting and 2-intersecting hypergraphs with maximal covering number: the Erdős-Lovász theme revisited [article]

János Barát
2020 arXiv   pre-print
Erdős and Lovász noticed that an r-uniform intersecting hypergraph H with maximal covering number, that is τ(H)=r, must have at least 8/3r-3 edges.  ...  In a related question, we try to find 2-intersecting r-uniform hypergraphs with maximal covering number, that is τ(H)=r-1.  ...  Acknowledgement We thank Máté Bárány for stimulating discussions and writing the covering number calculator for us.  ... 
arXiv:2011.04444v1 fatcat:5e7zspszwvgmroltpuwwh6y6ya
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