304 resultados para geostationary orbit
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On November 26 th, 2005, Rhea, one of Saturn's moons, is found by Cassini spacecraft approximately at 5.105 km from Saturn. Observations in situ reveal that electrons are depleted in the moon's vicinity. However, Rhea is considered massive enough to retain a thin atmosphere. Assumption was that the atmosphere of Rhea was not composed exclusively of gas, its likely contains solid material that can absorb magnetospheric particles. According to Jones et al. (2008), these particles were in a speci c position so that at the moment of observation the electrons could not be detected. In opposition to this idea there is a group, Tiscareno et al. 2010, Cornell University Library, that underwent intensive search for any material that might be orbiting Rhea using Cassini images, however the could not identify any. Second recommendation made by American researchers and other countries, and accepted by the National Board of Research the Cassini Equinox Mission will continue in orbit around Saturn until 2016.The probe will perform several maneuvers with high inclination to delve into the main ring system, and then enter in Saturn's atmosphere and collide with planet. This research is of great importance because until today no rings were found orbiting satellites. The goal of this work is to analyze the orbital evolution of a set of particles around Rhea disturbance of Saturn, J2 e J4 and check results by the numerical simulations and the possibility of a stable ring orbiting Rhea.
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Pós-graduação em Agronomia (Energia na Agricultura) - FCA
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Pós-graduação em Engenharia Mecânica - FEG
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The aim of the present study was to analyze the etiology, type and treatment employed in the orbito-zygomatic fractures (OZ). Also, postoperative complications are described and correlated with the type of treatment used. Fifty patients with OZ fractures were evaluated. Orbital fractures in which the zygomatic bone was not involved were excluded. Epidemiologic data and characteristics of treatment such as the type of material used for osteosynthesis, number of anatomical sites on which rigid internal fixation (RIF) was applied, surgical approaches and associated complications were recorded. The main causes of trauma were motorcycle and bicycle accidents, constituting 52% of the sample. The osteosynthesis system used was the 2.0 mm, except in four patients in whom the 1.5mm system was used for fixation at the infra-orbital rim. A total of 18% of the patients required reconstruction of the internal orbit and in all cases titanium mesh was used. 46% of the patients received RIF in three anatomical sites, most in the fronto-zygomatic suture, infra-orbital rim and zygomatic-maxillary buttress. The most frequent complication was paresthesia of the infra-orbital nerve (34 patients, 68%). Other findings were also discussed with the intent of better understanding the treatment of the OZ fractures.
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The objective of this project was to monitor the satellites of the Global Positioning System (GPS) from a fixed point on Earth and to verify the rate of recurrence respect to their rotation and displacement. A topographic GPS signal receiver connected to a personal computer was used to recorded, for five days, the displacement of the satellites. This work was based on the fact that many literature references state that satellites complete one orbit around the Earth every 12 hours, then, it is assumed that the satellite would be seen twice in a day from the same fixed point on Earth.Although, this does not occur, as thise time interval correspond to 12 hours sidereal time and not solar time. In addition, this study was carried out in order toconfirm and update the information related to the number of satellites in operation today, found to be 31. In that sense, some references concerning the space segment of this system were defined in details.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Resonance capture is studied numerically in the three-body problem for arbitrary inclinations. Massless particles are set to drift from outside the 1: 5 resonance with a Jupiter-mass planet thereby encountering the web of the planet's diverse mean motion resonances. Randomly constructed samples explore parameter space for inclinations from 0 to 180 degrees with 5 degrees increments totalling nearly 6 x 10(5) numerical simulations. 30 resonances internal and external to the planet's location are monitored. We find that retrograde resonances are unexpectedly more efficient at capture than prograde resonances and that resonance order is not necessarily a good indicator of capture efficiency at arbitrary inclination. Capture probability drops significantly at moderate sample eccentricity for initial inclinations in the range [10 degrees,110 degrees]. Orbit inversion is possible for initially circular orbits with inclinations in the range [60 degrees,130 degrees]. Capture in the 1:1 co-orbital resonance occurs with great likelihood at large retrograde inclinations. The planet's orbital eccentricity, if larger than 0.1, reduces the capture probabilities through the action of the eccentric Kozai-Lidov mechanism. A capture asymmetry appears between inner and outer resonances as prograde orbits are preferentially trapped in inner resonances. The relative capture efficiency of retrograde resonance suggests that the dynamical lifetimes of Damocloids and Centaurs on retrograde orbits must be significantly larger than those on prograde orbits implying that the recently identified asteroids in retrograde resonance, 2006 BZ8, 2008 SO218, 2009 QY6 and 1999 LE31 may be among the oldest small bodies that wander between the outer giant planets.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)