Dissertations / Theses on the topic 'Occultation de la violence'
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1
Prigent, Pierre-Guillaume. "Les stratégies des pères violents en contexte de séparation parentale : contrôle coercitif, complicité institutionnelle et résistance des femmes." Thesis, Brest, 2021. http://www.theses.fr/2021BRES0102.
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Dans cette thèse, nous étudions les stratégies que les pères violents adoptent en contexte de séparation parentale. À partir d’entretiens réalisés avec une vingtaine de femmes qui se sont séparées d’un conjoint violent avec qui elles ont eu des enfants, nous identifions les tactiques employées par les agresseurs avant, pendant et après la séparation : isolement, privation de ressources, contrôle, intimidation, dévalorisation, confusion, sur-responsabilisation et violence. Ces tactiques se cumulent, se combinent et s’entremêlent dans la stratégie visant à maintenir pouvoir et contrôle sur la femme et les enfants victimes. Les réponses sociales et institutionnelles à la violence peuvent reproduire les tactiques repérées, et relever de complicité avec l’agresseur. L’espace pour l’action des victimes, réduit lors de la relation conjugale puis étendu grâce à la séparation, est de nouveau restreint par le principe de l’autorité parentale conjointe, qui implique un maintien du lien pouvant exposer à de nouvelles violences, et soumettre les victimes à un contrôle de leurs activités quotidiennes par l’agresseur. La résistance des femmes à la violence et au contrôle post-séparation et leurs tentatives de protéger les enfants sont alors considérées comme un obstacle à la coparentalité. Les droits parentaux des victimes peuvent être réduits, voire la résidence des enfants transférée chez l’agresseur. Cette analyse souligne les résistances institutionnelles à la prise en compte des violences conjugales post-séparation dans la parentalitéIn this thesis, we study the strategies that abusive fathers adopt in the context of parental separation. Based on interviews with twenty women who have separated from an abusive partner with whom they had children, we identify the tactics employed by abusers before, during and after separation: isolation, deprivation of resources, control, intimidation, devaluation, confusion, overburden of responsibility and violence. These tactics accumulate, combine and intertwine in the strategy to maintain power and control over the victimised woman and children. Social and institutional responses to violence may replicate the tactics identified, and may involve complicity with the abuser.The space for action of the victims, reduced during the relationship and then extended by the separation, is again restricted by the principle of joint parental authority, which implies maintaining the link that can expose the victims to further violence and subject them to control of their daily activities by the aggressor.Women's resistance to post-separation violence and control and their attempts to protect the children are then seen as an obstacle to co-parenting. Victims' parental rights may be curtailed or the children's residence transferred to the abuser. This analysis highlights the institutional resistance to taking post-separation domestic violence into account in parenting
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Olkin, Catherine Blair. "Stellar occultation studies of Triton's atmosphere." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/55046.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1996.Includes bibliographical references (p. 127-136).
by Catherine Blair Olkin.
Ph.D.
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Salyk, Colette Vanessa. "Stellar occultation investigations of Pluto's atmosphere." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/114110.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2003.Cataloged from PDF version of thesis. Page 21 missing from original thesis.
Includes bibliographical references (pages 27-28).
We investigate the shape of Pluto's atmosphere using data from the occultation of the V=15.7 star P131.1 by Pluto on 2002 Aug 21 (UT). We find that Pluto's atmosphere, as projected onto the sky, is noticeably non-circular. This implies an overall ellipsoidal shape, which could be an indication of high winds and/or latitudinal stratification. We decide to compare our results to those obtained from datasets of the occultation of P8 by Pluto on 1988 June 9 (UT). Previous analyses of these datasets by Millis et al. (1993) had led to the conclusion that Pluto's atmospheric shape did not deviate from that of a sphere. However, we find that the 1988 datasets do not conclusively demonstrate that this is the case. We conclude that Pluto's atmosphere is currently non-spherical and could have been non-spherical at the time of the 1988 occultation. Implications for high winds and/or latitudinal stratification present exciting possibilities to be investigated by the upcoming New Horizons mission to Pluto.
by Colette Salyk.
S.B.
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Cooray, Asantha Roshan. "Stellar occultation observations of Saturn's upper atmosphere." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/53030.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1997.Includes bibliographical references (leaves 74-79).
by Asantha Roshan Cooray.
M.S.
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Foust, Jeffrey Alan 1971. "Stellar occultation studies of Saturn's upper atmosphere." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/9528.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1999.Includes bibliographical references (p. 224-230).
The properties of Saturn's upper atmosphere are not well-known despite several spacecraft flybys. However, the region of 1-100 [mu]bar can be studied in detail by observing stellar occultations -- when the planet passes in front of a star -- from ground-based or Earth-orbiting telescopes. We use data from five such occultations: three observed in 1995 by the Faint Object Spectrograph (FOS) on the Hubble Space Telescope (HST), one observed in 1996 at the NASA Infrared Telescope Facility (IRTF) and one in 1989 observed by a different instrument at the IRTF. The data span latitudes from 52° south to 75 ° north. We fit isothermal models to each data set and also perform numerical inversions. These analyses show that temperatures in the 1-10 [mu]bar range can vary significantly as a function of season and latitude, ranging from 121 to 160 K, in accordance with radiative transfer models for the atmosphere. We also search for evidence of gravity wave saturation in Saturn's upper atmosphere, as seen in other planetary atmospheres, by analyzing the power spectra of temperature and density data and by studying the temperature lapse rate in the atmosphere. Our analysis is consistent with saturated gravity waves for all data sets, although gravity wave saturation is not the sole explanation for the spectra. We take advantage of the wavelength-resolved HST FOS data to study the composition of Saturn's upper atmosphere. We measured the difference in feature times for data taken at two wavelengths, and use the different refractivities of hydrogen and helium, as a function of wavelength to compute the relative amounts of the two elements in the planet's atmosphere. We find that the helium mass fraction is 0.26 ± 0.10, higher than that found using Voyager data, but marginally consistent with theoretical models for the evolution of Saturn's atmosphere, although the large error bars on the results make a definitive conclusion problematic.
by Jeffrey Alan Foust.
Ph.D.
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Bérard, Diane. "Etude des anneaux de Chariklo par occultation stellaire." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066128/document.
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Les occultations stellaires sont une méthode puissante pour étudier les petits corps du Système Solaire, trop faibles ou lointains pour être étudiés par d’autres techniques. Cette méthode consiste à observer le corps passant devant une étoile d’arrière plan. Le flux lumineux stellaire est alors intercepté quelques instants, ce qui permet de caractériser la forme de l’objet et d’étudier son environnement (anneau, atmosphère ou satellite). Deux anneaux denses et étroits ont été découverts en Juin 2013 pour la première fois autour du plus gros des Centaures Chariklo (corps central : 250 km de diamètre ; anneaux : 800 km). Cette thèse présente les 16 occultations par Chariklo et ses anneaux observées depuis 2013. Ces données représentent les seules observations aujourd’hui existantes de ce système planétaire. Une première étude de leur structure et de leur géométrie est détaillée dans ces travaux. Mes travaux ont également porté sur une occultation par la planète naine Haumea observée en Janvier 2017. Celle-ci nous a révélé la présence d’un anneau dense de rayon ~2281 km autour de ce corps tri-axial. Haumea est donc le deuxième corps en dehors des planètes géantes à posséder un anneau. Cette occultation permet notamment de déduire la forme, la taille (1161x852x513 km) et la densité d’Haumea. Cette seconde découverte tend à montrer que les anneaux autour des petits corps ne sont pas si rares. La publication du catalogue Gaia DR1 en 2016 a permis d’améliorer considérablement la précision de nos prédictions donc nos observations. Les prochaines années seront consacrées à scanner plus en détails les anneaux de Chariklo et d’Haumea, mais aussi à chercher des anneaux autour d’autres petits corps afin de comprendre les mécanismes de formation et d’évolution de ces systèmesStellar occultations are a very powerful tool to study small bodies of the Outer Solar System, which are usually too faint or too far away to be studied by others techniques. They occur when a body passes in front of a background star. The stellar flux will then be intercepted during several seconds/minutes. Observation of the occulted star in time allows us to study the shape and size of the occulting object and its vicinity (ring, atmosphere or satellite). For the first time, two dense and narrow rings have been discovered on June 2013 around the biggest known Centaur Chariklo (body’s diameter: 250 km and rings diameter: 800 km). My work shows the 16 observed occultations by Chariklo and/or its rings since 2013. Those data are the only one available about this planetary system today. A first study of their structure and their geometry is conducted. Another part of my work was to study an occultation by the dwarf planet Haumea recorded on January 2017. It revealed the presence of a ring of radius ~2281 km around this tri-axial body. This discovery made Haumea the second body with a ring orbiting around except the four giant planets. This occultation allows us to derive the shape, size (1161x852x513 km) and density of the main body. This second discovery tends to show that rings in small planetary systems are more common that we thought. The release of Gaia DR1 catalog in 2016 greatly improved our predictions of such occultations. In the forthcoming years, efforts will be made on detailed and localized studies of Chariklo’s and Haumea’s rings, but also on search for other small rings systems in order to better understand the origins and the evolution mechanisms of such systems
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Griggs, Erin R. "Analyses for a Modernized GNSS Radio Occultation Receiver." Thesis, University of Colorado at Boulder, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3704709.
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Global Navigation Satellite System (GNSS) radio occultation (RO) is a remote sensing technique that exploits existing navigation signals to make global, real-time observations of the Earth's atmosphere. A specialized RO receiver makes measurements of signals originating from a transmitter onboard a GNSS spacecraft near the Earth's horizon. The radio wave is altered during passage through the Earth's atmosphere. The changes in the received signals are translated to the refractivity characteristics of the intervening medium, which enable the calculation of atmospheric pressure, temperature, and humidity. Current satellite missions employing GNSS RO have provided invaluable and timely information for weather and climate applications. Existing constellations of occultation satellites, however, are aging and producing fewer quality measurements. Replacement fleets of RO satellites are imperative to sustain and improve the global coverage and operational impact achieved by the current generation of RO satellites. This dissertation describes studies that facilitate the development of next generation RO receivers and satellite constellations. Multiple research efforts were conducted that aim to improve the quantity and quality of measurements made by a future satellite-based RO collection system. These studies range in magnitude and impact, and begin with a receiver development study using ground-based occultation data. Future RO constellations and collection opportunities were simulated and autonomous occultation prediction and scheduling capabilities were implemented. Finally, a comprehensive study was conducted to characterize the stability of the GNSS atomic frequency standards. Oscillator stability for a subset of satellites in the GNSS was found to be of insufficient quality at timescales relevant to RO collections and would degrade the atmospheric profiling capabilities of an RO system utilizing these signals. Recommendations for a high-rate clock correction network are proposed, which provides significant improvement to the fractional errors in the derived refractivity, pressure, and temperature values caused by the oscillator instabilities.
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Hilbert, Bryan (Bryan Nathaniel) 1977. "Stellar occultation lightcurve modeling for elliptical occulting bodies." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/54444.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2001.Includes bibliographical references (leaf 41).
We present a new method of calculating model lightcurves for stellar occultations by the Jovian planets. We model the occulting planet as a three-dimensional body of non-zero ellipticity, and define two ellipses of intersection with the body which dictate the appearance of the lightcurve. These include the visible-limb plane ellipse, which is the observed figure of the body as seen in the sky, and the line-of-sight ellipse, which contains the line of sight to the occulted star, and is the plane in which the starlight is refracted. The observed stellar flux during the occultation is primarily dictated by the ellipticity and subsequent radius of curvature of the instantaneous ellipse in the line-of-sight plane. This new method is applied to several test cases, as well as to the Jovian occultation of HIP9369 on 10 October 1999. Lightcurves generated by this model are compared to identical situations using the method published in Hubbard et al. (1997), showing that the Hubbard model works well for low-latitude occultations, but fails at higher latitudes. In the case of the high-latitude Jovian occultation, the best-fit lightcurve, produced from this new method, yielded a half-light equatorial radius of 71,343±1.2 km with a scale height of 19.25±0.5km, and an isothermal temperature of 139K. The same data, fit using a lightcurve generated by the method described in Hubbard et al. (1997), resulted in a half-light equatorial radius of 71,819km with a scale height of 17.9km with errors comparable to the previous fit, resulting in an isothermal temperature of 129K. Lightcurves are numerically generated for an ellipsoidal planet and, for comparison, an approximation to the ellipsoidal case consisting of a sphere with radius equal to the radius of curvature of the ellipsoid at the half-light point. We find that in the case of an occultation where the line-of-sight ellipticity does not vary, that the radius of curvature approximation matches the ellipsoidal planet lightcurve to within 0.007%. For an oblique occultation however, the line-of-sight ellipticity varies, and the approximation, using only a single radius of curvature sphere, is only good to about 1%. As a result, we find that using a model such as that presented in Baum and Code (1953) to fit the lightcurve of an ellipsoidal planet can return values for half-light radius (after accounting for the distance between the center of curvature and the center of the body) which may match the local distance to the center of the ellipsoid to a fraction of a percent, while returning values of scale height which may be in error by several percent. Test cases are also then put through numerical inversions, to obtain temperature versus pressure profiles. Test cases with spherical planets return temperature profiles that match those used to create the lightcurves, while test cases with ellipsoidal planets return temperature profiles which can differ from the input temperatures by tens of degrees, assuming a constant local gravity over the course of the occultation.
by Bryan Hilbert.
S.M.
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Lange, Martin, and Christoph Jacobi. "Analysis of gravity waves from radio occultation measurements." Universitätsbibliothek Leipzig, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-217072.
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In the height range 10–30 km atmospheric gravity waves lead to periodic perturbations of the background temperature field in the order of 2-3 K, that are resolved in temperature profiles derived from radio occultation measurements. Due to the spherical symmetry assumption in the retrieval algorithm and the low horizontal resolution of the measurement damping in the amplitude and phase shift of the waves occurs leading to remarkable errors in the retrieved temperatures. The influence of the geometric wave parameters and the measurement geometry on plane gravity waves in the range 100-1000 km horizontal and 1-10 km vertical wavelength is investigated with a 2D model ranging ±1000 km around the tangent point and 10-50 km in height. The investigation shows, that with radio occultation measurements more than 90 % of the simulated waves can be resolved and more than 50% with amplitudes above 90%. But the geometrical parameters cannot be identified, since one signal can be attributed to different combinations of wave parameters and view angle. Even short waves with horizontal wavelengths below 200 km can be derived correctly in amplitude and phase if the vertical tilt is small or the view angle of the receiver satellite is in direction of the wave crestsAtmosphärische Schwerewellen führen im Höhenbereich 10-30 km zu periodischen Störungendes Hintergrundtemperaturfeldes in der Größenordnung von 2-3 K, die in Temperaturprofilen aus Radiookkultationsmessungen aufgelöst werden. Aufgrund der sphärischen Symmetrieannahme im Retrievalverfahren und durch die niedrige horizontale Auflösung des Messverfahrens werden Phasenverschiebungen und Dämpfung der Amplitude verursacht, die zu beachtlichen Fehlern bei den abgeleiteten Temperaturen führen. Der Einfluss der geometrischen Wellenparameter und der Messgeometrie auf ebene Schwerewellen im Bereich 100-1000 km horizontale und 1-10 km vertikale Wellenlänge wird untersucht mit einem 2D-Modell, dass sich auf ein Gebiet von ±1000 km um den Tangentenpunkt und von 10-50 km in der Höhe erstreckt. Die Untersuchung zeigt, dass mit Radiookkultationsmessungen mehr als 90% der simulierten Wellen aufgelöst werden und mehr als 50% mit Amplituden oberhalb von 90% der ursprünglichen. Die geometrischen Parameter können jedoch nicht aus Einzelmessungen abgeleitet werden, da ein Signal zu verschiedenen Kombinationen von Wellenparametern und Sichtwinkel zugeordnet werden kann. Auch relativ kurze Wellen mit horizontalen Wellenlängen unterhalb von 200 km können korrekt in der Amplitude und Phase aufgelöst werden, falls die Neigung des Wellenvektors gegen die vertikale gering ist oder der Sichtwinkel des Empfängersatelliten in Richtung der Wellenberge ist
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Lange, Martin, and Christoph Jacobi. "Analysis of gravity waves from radio occultation measurements." Wissenschaftliche Mitteilungen des Leipziger Instituts für Meteorologie ; 26 = Meteorologische Arbeiten aus Leipzig ; 7 (2002), S. 101-108, 2002. https://ul.qucosa.de/id/qucosa%3A15225.
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In the height range 10–30 km atmospheric gravity waves lead to periodic perturbations of the background temperature field in the order of 2-3 K, that are resolved in temperature profiles derived from radio occultation measurements. Due to the spherical symmetry assumption in
the retrieval algorithm and the low horizontal resolution of the measurement damping in the amplitude and phase shift of the waves occurs leading to remarkable errors in the retrieved temperatures. The influence of the geometric wave parameters and the measurement geometry on plane gravity waves in the range 100-1000 km horizontal and 1-10 km vertical wavelength is investigated with a 2D model ranging ±1000 km around the tangent point and 10-50 km in height. The investigation shows, that with radio occultation measurements more than 90 % of the simulated waves can be resolved and more than 50% with amplitudes above 90%. But the geometrical parameters cannot be identified, since one signal can be attributed to different combinations of wave parameters and view angle. Even short waves with horizontal wavelengths below 200 km can be derived correctly in amplitude and phase if the vertical tilt is small or the view angle of the receiver satellite is in direction of the wave crests.Atmosphärische Schwerewellen führen im Höhenbereich 10-30 km zu periodischen Störungendes Hintergrundtemperaturfeldes in der Größenordnung von 2-3 K, die in Temperaturprofilen aus Radiookkultationsmessungen aufgelöst werden. Aufgrund der sphärischen Symmetrieannahme im Retrievalverfahren und durch die niedrige horizontale Auflösung des Messverfahrens werden Phasenverschiebungen und Dämpfung der Amplitude verursacht, die zu beachtlichen Fehlern bei den abgeleiteten Temperaturen führen. Der Einfluss der geometrischen Wellenparameter und der Messgeometrie auf ebene Schwerewellen im Bereich 100-1000 km horizontale und 1-10 km vertikale Wellenlänge wird untersucht mit einem 2D-Modell, dass sich auf ein Gebiet von ±1000 km um den Tangentenpunkt und von 10-50 km in der Höhe erstreckt. Die Untersuchung zeigt, dass mit Radiookkultationsmessungen mehr als 90% der simulierten Wellen aufgelöst werden und mehr als 50% mit Amplituden oberhalb von 90% der ursprünglichen. Die geometrischen Parameter können jedoch nicht aus Einzelmessungen abgeleitet werden, da ein Signal zu verschiedenen Kombinationen von Wellenparametern und Sichtwinkel zugeordnet werden kann. Auch relativ kurze Wellen mit horizontalen Wellenlängen unterhalb von 200 km können korrekt in der Amplitude und Phase aufgelöst werden, falls die Neigung des Wellenvektors gegen die vertikale gering ist oder der Sichtwinkel des Empfängersatelliten in Richtung der Wellenberge ist.
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Safizadeh, Neda. "Detection of extrasolar planets via microlensing and occultation /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2001. http://wwwlib.umi.com/cr/ucsd/fullcit?p3001275.
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Ward, Dale Michael 1963. "Atmospheric sounding from satellite solar occultation refraction measurements." Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/282495.
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Measurements of the refractive bending of solar radiation passing through the limb of the Earth's atmosphere can be utilized to recover vertical profiles of density and temperature. These parameters obtained using the technique of solar refractive sounding could be used to improve satellite solar occultation trace species retrievals and to monitor potential trends in upper atmospheric temperatures. The solar refractive sounding method is described in detail and applied to data available from the Stratospheric Aerosol and Gas Experiment (SAGE II). The meteorological profiles derived from the SAGE II data are not consistently accurate enough for general use due to poor vertical sampling and measurement uncertainties. However, the qualitatively decent results provide optimism for future development and implementation of solar occultation refractive sounders. Better techniques for measuring solar refraction and the potential improvements in the retrievals are also discussed.
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Andreoli, Francesca. "Improvement of Jupiter's satellites ephemerides using stellar occultation observations." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/18030/.
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The inner Galilean moons orbiting Jupiter are locked into the so-called “Laplace resonance”, where the orbital periods of Ganymede, Europa and Io maintain a 4:2:1 ratio respectively. Resonant dynamics appear several times across the Solar System and determining whether the Jovian resonance is deepening or loosening would provide a direct insight into the origin and the evolution of the Solar System.
At the moment, our knowledge of the Galilean moons' dynamics is not accurate enough to establish in which direction the system is evolving. Including stellar occultation observations obtained from an orbiting spacecraft could result in a critical improvement of these estimations.
Since the spacecraft’s orbit and the stars’ position are generally very well known, every time one of the moons crosses the line-of-sight from the spacecraft to the star its position can be constrained very accurately.
The results of this thesis lay the foundations for the introduction of stellar occultation observations in the orbit determination process of planetary satellites and other celestial bodies. First, a geometrical/mathematical model of the distance between the moon’s limbs and a given star detected in its surroundings was developed and tested. Afterwards, a code to detect and archive all the stellar occultation events in a given time span was implemented. Finally, a parametric covariance analysis was performed to obtain a preliminary assessment of the improvements provided by the introduction of stellar occultation observations and investigate the influence of each variable on the orbit determination problem.
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Sallum, Stephanie E. "Pluto's atmosphere from the May 22, 2011 stellar occultation." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/114349.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 40-41).
This paper reports the observations and atmospheric fitting results from the May 22, 2011 stellar occultation by Pluto. Of the nine sites across the United States that attempted to observe the event, three obtained light curves at the predicted midtime without being clouded out. Simultaneous fitting of these three light curves utilizing a model fully detailed in Elliot and Young [1992] resulted in a best fit half-light radius of 1309 ± 25 km, a calculated temperature of 94 ± 4 K, and a calculated pressure scale height of 55 ± 2 km. These parameters, in the context of the previous occultations, reveal a trend in which Pluto's half-light radius has been increasing slightly since an initial dramatic increase between 1988 and 2002. While the pressure scale height has remained relatively constant, the temperature has decreased slightly over the recorded events. The changes in half-light radius agree with frost migration models in which Pluto's surface has a low thermal inertia [Hansen and Paige, 1996; Elliot et al., 2007], but further constraints on frost migration model parameters such as substrate and frost albedo, frost emissivity, and the supply of N2 require additional observations. The New Horizons spacecraft should encounter a dynamic atmosphere on Pluto during the scheduled fly by in 2015.
by Stephanie E. Sallum.
S.B.
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Boryczko, Marta, and Tomasz Dziendziel. "Optimisation Of Ionospheric Scintillation Model Used In Radio Occultation." Thesis, Blekinge Tekniska Högskola, Institutionen för tillämpad signalbehandling, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-11915.
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This thesis is executed in cooperation with RUAG Space AB, which specializes in highly reliable on-board satellite equipment. The thesis focuses on the effect, which disturbs the amplitude and phase of a Global Positioning System (GPS) signal, called scintillation effect. It has a substantial impact on a GPS signal, during Radio Occultation (RO). RO is a method of analysis of a refracted signal which passes through the atmosphere. RO can be used for measuring climate change and for weather forecasting. By retrieving the bending angle of a GPS signal, three basic parameters of the Earth’s atmosphere can be obtained at different heights: temperature, pressure and humidity. As the scintillation effect causes prominent errors in the bending angle calculations, it is crucial to provide possibly the most precise mathematical model, which allows to conceive proper ionospheric corrections. In this thesis, the model using Rytov approach is implemented and optimised with different optimisation functions. It is shown that the scintillation model can be optimized, which may contribute to a more accurate retrieval of the atmospheric profiles.
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Gramigna, Edoardo. "Radio Occultation experiments of Venus and Mars: similarities and differences." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/20477/.
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In the last decades Venus has not been explored as in the early days of interplanetary missions, yet today the interest has increased and different space agencies are preparing proposals for future missions. Venus provides a laboratory next door to our planet to study how rocky planets can form and evolve differently from Earth, even when they start out very similar. Our neighboring planet is the perfect example of what happens in a runaway greenhouse effect, and the state of its atmosphere is interesting in its own right, as it is directly linked to the story of water on the planet and ultimately to the big question of whether life could have arisen beyond Earth. The main purpose of this thesis is the study of the atmosphere of Venus through the radio occultation experiments performed by the Venus Express Mission (VEX), sent by the European Space Agency in 2005. In the frame of this investigation comparisons between the Venus atmosphere and Mars atmosphere are shown, in order to highlight the similarities and differences between the two planets. The conclusions derived from this work can potentially improve our knowledge and highlight new scientific results about the Venus atmosphere.
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Elliott, Garrett T. "Detecting the debris of solar system formation via stellar occultation." Connect to resource, 2008. http://hdl.handle.net/1811/32191.
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Burchell, Ian Robert. "Water vapour and temperature retrievals from the EURECA occultation radiometer." Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337562.
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Palmer, Paul Ian. "Analysis of atmospheric temperature and humidity from radio occultation measurements." Thesis, University of Oxford, 1998. http://ora.ox.ac.uk/objects/uuid:9d6f02de-527a-46b4-acda-2e8723f27f50.
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Radio occultation measurements from global navigation satellite systems, such as the Global Positioning System (GPS), represent a new source of numerical weather prediction information. Conventionally, radio occultation measurements are inverted using an Abel integral transform to obtain a profile of refractivity, and subsequently pressure, on geometric height levels via the hydrostatic relation. Although accurate temperature/water vapour retrievals are possible with a background estimate of water vapour/temperature, it is not possible to retrieve these quantities simultaneously using this method. Also, using this method, refractivity retrieval errors are introduced by assuming no horizontal structure local to ray periapsis (the spherical symmetry assumption), and the method is subject to 'first-guess' errors when the hydrostatic relation is initialised. Results from an investigation into how departures from spherical symmetry affect the performance of the Abelian inverse method are presented. It is shown that realistic horizontal humidity inhomogeneities can compensate for or reinforce horizontal temperature inhomogeneities, and therefore are important to consider in both the forward and inverse modelling. Using the results from this experiment, regression coefficients are fitted in an effort to predict temperature and refractivity retrieval errors from the horizontal temperature and humidity structure local to the measurement. The largest contribution to the predicted errors is shown to be from the local parabolic component of the horizontal structure, but is found to predict only a small fraction of the total error. A non-linear optimal estimation inverse method is presented with which it is possible to retrieve simultaneously profiles of temperature, humidity and surface pressure. Using this method, the measurements are assimilated with a priori information utilising error estimates of the a priori information and the measurements. The method implemented is validated using an ensemble of numerical simulations. Real observations from the GPS/MET pilot experiment are used to retrieve profiles of temperature, humidity and surface pressure which are validated using collocated ECMWF and NMC model analyses, radiosondes, and the Abelian inversion results. Temperature and refractivity comparisons between the optimal estimate and results from the Abelian inverse method show good agreement at high latitudes for all altitudes, resolving small-scale structure not shown by the model analyses. At low latitudes there is good agreement above the tropopause, below which a temperature bias ensues between the Abelian inversion and all other correlative data. Retrieved values for water vapour and surface pressure compare well with model analyses and collocated radiosondes. Biases between the UKMO and the ECMWF model analyses are consistent with known differences between the two models at the time of the dataset.
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Baron, Richard Leigh. "Occultation astronomy and instrumentation : studies of the Uranian upper atmosphere." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/51472.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1989.Includes bibliographical references (leaves 207-208).
by Richard Leigh Baron.
Ph.D.
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Spickler, Philip Todd. "Solar infrared relative intensity data from the Halogen Occultation Experiment." W&M ScholarWorks, 1997. https://scholarworks.wm.edu/etd/1539623905.
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Solar data from the Halogen Occultation Experiment (HALOE) were analyzed to determine the center-to-limb relative intensity and the vertical temperature profile for the quiet and active Sun over wavelengths from 2.4 to 10 {dollar}\mu{dollar}m. An algorithm that incorporated a nonlinear least squares procedure was developed that modeled the HALOE instrument during data acquisition. Data obtained from limb-to-limb scans along the solar equator on days of very low activity in May 1994 were analyzed to obtain coefficients of a function describing the relative intensity from center to limb. The relative intensities produced were precise to 0.1% (2{dollar}\sigma{dollar}) from the center to 0.25 arc min from the limb. The brightness temperature from the flux and the temperature as a function of monochromatic optical depth were also calculated from the coefficients. These quantities were normalized using published central intensities and compared to a semiemperical model of the photosphere. In general, the calculated temperature quantities were in good agreement with the model predictions; however, differences occurring between 2.4 and 3 {dollar}\mu{dollar}m suggest that the central intensities used here are low.;HALOE solar data were also investigated to obtain the intensity of a sunspot relative to the photosphere. A nonlinear least squares method was used to retrieve relative intensity information for a large sunspot on August 19, 1942. at each wavelength a one-component sunspot model proved sufficient to fit the measurements to the digitization level of the instrument. Sunspot/photosphere intensity ratios were calculated at each wavelength with an uncertainty of 2%. Compared with previous measurements at shorter wavelengths from 0.387 to 2.35 {dollar}\mu{dollar}m, the data exhibit the same general trend of larger ratios with increasing wavelengths; however, a larger than anticipated gap exists between the previous value at 2.35 {dollar}\mu{dollar}m and the HALOE ratio value at 2.45 {dollar}\mu{dollar}m. The photospheric and sunspot temperatures were calculated at each wavelength and show slight decreases with increasing wavelength. A steep drop exhibited by the previous measurements between 1.67 and 2.35 {dollar}\mu{dollar}m is not supported by HALOE values. Consideration of terrestrial atmospheric effects in the previous data could explain this discrepancy.
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Bhattacharya, Yajnavalkya. "Analysis of a solar occultation experiment from the space shuttle Columbia." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0030/MQ27334.pdf.
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Livings, David. "Evaluation of Stratospheric Water Vapour Analyses Using a Solar Occultation Instrument." Thesis, University of Reading, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520099.
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Bosh, Amanda Sachie. "Stellar occultation studies of Saturn's rings with the Hubble Space Telescope." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/35368.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1994.Includes bibliographical references (p. 157-162).
by Amanda Sachie Bosh.
Ph.D.
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Min, Rui. "Reconnaissance de visage robuste aux occultations." Thesis, Paris, ENST, 2013. http://www.theses.fr/2013ENST0020/document.
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La reconnaissance faciale est une technologie importante en vision par ordinateur, avec un rôle central en biométrie, interface homme-machine, contrôle d’accès, indexation multimédia, etc. L’occultation partielle, qui change complétement l’apparence d’une partie du visage, ne provoque pas uniquement une dégradation des performances en reconnaissance faciale, mai peut aussi avoir des conséquences en termes de sécurité. Dans cette thèse, nous concentrons sur le problème des occultations en reconnaissance faciale en environnements non contrôlés. Nous proposons une séquence qui consiste à analyser de manière explicite les occultations et à fiabiliser la reconnaissance faciale soumises à diverses occultations. Nous montrons dans cette thèse que l’approche proposée est plus efficace que les méthodes de l’état de l’art opérant sans traitement explicite dédié aux occultations. Nous identifions deux nouveaux types d’occultations, à savoir éparses et dynamiques. Des solutions sont introduites pour gérer ces problèmes d’occultation nouvellement identifiés dans un contexte de vidéo surveillance avancé. Récemment, le nouveau capteur Kinect a été utilisé avec succès dans de nombreuses applications en vision par ordinateur. Nous introduisons ce nouveau capteur dans le contexte de la reconnaissance faciale, en particulier en présence d’occultations, et démontrons son efficacité par rapport aux caméras traditionnelles. Finalement, nous proposons deux approches basées 2D et 3D permettant d’améliorer les techniques de base en reconnaissance de visages. L’amélioration des méthodes de base peut alors générer un impact positif sur les résultats de reconnaissance en présence d’occultationsFace recognition is an important technology in computer vision, which often acts as an essential component in biometrics systems, HCI systems, access control systems, multimedia indexing applications, etc. Partial occlusion, which significantly changes the appearance of part of a face, cannot only cause large performance deterioration of face recognition, but also can cause severe security issues. In this thesis, we focus on the occlusion problem in automatic face recognition in non-controlled environments. Toward this goal, we propose a framework that consists of applying explicit occlusion analysis and processing to improve face recognition under different occlusion conditions. We demonstrate in this thesis that the proposed framework is more efficient than the methods based on non-explicit occlusion treatments from the literature. We identify two new types of facial occlusions, namely the sparse occlusion and dynamic occlusion. Solutions are presented to handle the identified occlusion problems in more advanced surveillance context. Recently, the emerging Kinect sensor has been successfully applied in many computer vision fields. We introduce this new sensor in the context of face recognition, particularly in presence of occlusions, and demonstrate its efficiency compared with traditional 2D cameras. Finally, we propose two approaches based on 2D and 3D to improve the baseline face recognition techniques. Improving the baseline methods can also have the positive impact on the recognition results when partial occlusion occurs
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Rönnberg, Sjödin Oskar, and David Ahlsin. "Development of Simulation Tool and New Tracking Algorithms for Radio Occultation Receivers." Thesis, Linköpings universitet, Kommunikationssystem, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-75424.
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When a radio signal traverses the atmosphere it will be delayed by not only thedistance between transmitter and receiver, but also the atmosphere. Given knowl-edge of the characteristics of the sent signal the effect of the atmosphere can beobtained from the received signal. This concept is called radio occultation. Radiooccultation can provide high accuracy profiles of temperature, pressure and watervapour troughout the atmosphere.This report aims to present the work and results from a thesis performed atRUAG Space in Göteborg. The purpose of the thesis was to implement a simulatorwhich with high accuracy could generate a signal as it would have been receivedhad it propagated through the atmosphere.We will show that the generated signal passes the requirements that have beenset.När en radiovåg passerar genom atmosfären kommer den att fördröjas, inte bara avavståndet mellan sändare och mottagare utan också av atmosfären. Givet kunskapom karaktäristiken hos den sända signalen kan atmosfärens effekt erhållas från denmottagna signalen. Detta koncept kallas för radio-ockultation. Radio-ockultationkan med hög noggrannhet ge profiler för temperatur, tryck och vattenånga genomatmosfären.Denna rapport ämnar presentera det jobb och de resultat som uppnåtts genomett examensarbete genomfört på RUAG Space i Göteborg. Examensarbetets syftevar att implementera en simulator som med hög noggrannhet kan generera ensignal så som den hade sett ut då den propagerat genom atmosfären.Vi kommer att visa att den genererade signalen uppnår de krav som ställts.
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Sievert, Thomas. "GNSS Radio Occultation Inversion Methods and Reflection Observations in the Lower Troposphere." Licentiate thesis, Blekinge Tekniska Högskola, Institutionen för matematik och naturvetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-17484.
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GNSS Radio Occultation (GNSS-RO) is an opportunistic Earth sensing technique where GNSS signals passing through the atmosphere are received in low Earth orbit and processed to extract meteorological parameters. As signals are received along an orbit, the measured Doppler shift is transformed to a bending angle profile (commonly referred to as bending angle retrieval), which, in turn, is inverted to a refractivity profile. Thanks to its high vertical resolution and SI traceability, GNSS-RO is an important complement to other Earth sensing endeavors. In the lower troposphere, GNSS-RO measurements often get degraded and biased due to sharp refractive gradients and other complex structures. The main objective of this thesis is to explore contemporary retrieval methods such as phase matching and full spectrum inversion to improve their performance in these conditions. To avoid the bias caused by the standard inversion, we attempt to derive additional information from the amplitude output of the examined retrieval operators. While simulations indicate that such information could be found, it is not immediately straightforward how to achieve this with real measurements. The approach chosen is to examine reflected signal components and their effect on the amplitude output.
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Davé, Pratik K. (Pratik Kamlesh). "Using a co-located GNSS radio occultation payload for microwave radiometer calibration." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/93798.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 55-58).
This study presents a new method of calibrating an orbital cross-track scanning microwave radiometer using a co-located radio occultation (RO) instrument with Global Navigation Satellite Systems (GNSS). The radiometer and RO receiver periodically observe the same volume of atmosphere near the earth's limb, allowing for overlapping, or collocated, measurements that can be used to calibrate the radiometer. This method leverages the benefits of both remote sensing techniques to strengthen the science returned with the goal of achieving dense geospatial sampling and highly accurate calibration. Performance analyses show that the technique is particularly well-suited for implementation on a low-cost CubeSat hosting both radiometer and RO receiver systems on the same spacecraft. We describe a validation platform for this calibration method, the Microwave Radiometer Technology Acceleration (MiRaTA) CubeSat, currently in development by MIT Lincoln Laboratory and MIT Space Systems Laboratory for the NASA Earth Science Technology Office. MiRaTA will fly a multi-band radiometer and the Compact TEC/Atmosphere GPS Sensor (CTAGS) in 2016. We investigate the effect of system design parameters such as hardware specifications and operational concepts on the performance of this co-located remote sensing method.
by Pratik K. Dave.
S.M.
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van, Cleef Garrett Warren. "Zonal winds between 25 and 120 km retrieved from solar occultation spectra /." The Ohio State University, 1989. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487672631600168.
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Singleton, Cynthia Shaw. "Investigation of arctic ozone loss using solar occultation and microwave limb sounding instruments." Diss., Connect to online resource, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3239417.
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Chamberlain, Dawn Marie. "A numerical method for calculating occultation light curves from an arbitrary atmospheric model." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/91324.
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Siu, Ho Chit. "A discrete forward-modeling method for characterizing occultation lightcurves of tenuous planetary atmospheres." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98677.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 108-110).
We present a discrete numerical approach for forward-modeling lightcurves from stellar occultations by planetary atmospheres. Our discrete approach provides a way to arbitrarily set atmospheric properties at any radius from the occulting body, giving it flexibility for applying models of vertical variation in atmospheric conditions. The method is used to examine trends in lightcurve characteristics resulting from changes in the atmosphere of the occulting body. We find that for Pluto-like atmospheres, temperature and pressure variations affect the characteristics of the lightcurve much more than the gas composition. We also find that the half-light radius is more sensitive to atmospheric changes than either the minimum normalized flux or the slope at half-light. Temperature is found to be the most easily-constrained atmospheric parameter, as the gradients for changes in lightcurve characteristics are much more aligned with the temperature axis of the atmospheric parameter space than any other axis. Trends in lightcurve characteristics were examined in and around the parameter space occupied by the atmospheric conditions predicted for Pluto based on the 2011 and 2013 occultation events. Our error analysis method produced uncertainty values consistent with the reported uncertainties for half-light radius. This kind of lightcurve characterization is potentially useful for constraining the level of precision required in measuring given lightcurve characteristics in order to provide certain uncertainty bounds on the atmospheric conditions of the occulting body.
by Ho Chit Siu.
S.M.
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Capalbo, Fernando. "Composition et température de l'haute atmosphère de Titan à partir des occultations stellaires et solaires mesurées par Cassini-spectrographe d'imagerie ultraviolet." Thesis, Paris Est, 2013. http://www.theses.fr/2013PEST1101/document.
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Ce projet de thèse porte sur l'étude de la haute atmosphère de Titan à partir de mesures en laboratoire de sections efficaces d'absorption et de l'analyse des données de Cassini-UVIS.La caractérisation de l'instrument et des observations effectuées par UVIS était nécessaire. Les données provenant des canaux ultraviolet lointain (FUV) et ultraviolet extrême (EUV) d'UVIS ont été analysées et corrigées des effets instrumentaux. A partir de l'analyse de huit occultations solaires dans l'EUV, les profils de densité volumique de N2 et CH4 ont été déterminés par une méthode d'inversion avec régularisation. Les températures ont ensuite été obtenues à partir des profils de N2 en supposant une haute atmosphère isotherme. Les occultations stellaires dans le FUV ont été modélisés et une technique de détermination des densités caractérisée. La possibilité de détection de différentes molécules (dont certaines n'avaient jamais été observés par cette technique avant) a été analysée. Puis, en utilisant l'algorithme de minimisation de Levenberg–Marquardt, les profils de densité de colonne pour différents hydrocarbures et de profondeurs optiques pour les aérosols ont été obtenus à partir de données simulés. Les densités de colonne ont été inversées avec une procédure de régularisation afin d'obtenir des profils de densité volumique pour les hydrocarbures et des profils d'extinction pour les aérosols. La procédure a finalement été appliquée à deux occultations stellaires mesurées par UVIS. Les hydrocarbures étudiés sont CH4, C2H2, HCN, C2H4, C4H2, HC3N et C6H6.Les profils issus des occultations stellaires et solaires ont été obtenus pour différentes dates et des différents lieux. Les profils et les températures dérivés ont donc été analysés en fonction des variables géographiques et temporelles : latitude, longitude, date d'observation, etc. La variabilité atmosphérique est discutée à la lumière de ces résultats.Le benzène (C6H6), une molécule détectée dans l'atmosphère de Titan, est particulièrement importante car elle est considéré comme intermédiaire entre le gaz et la formation des particules solides. Des mesures de l'absorption du benzène dans le domaine ultraviolet, à des températures qui couvrent une gamme de température allant de l'ambiante à 215 K, ont été réalisées dans différentes installations internationales. A partir de ces mesures, la section efficace d'absorption du benzène a été déterminée et analysée en termes des transitions observées et en fonction de la température de mesure. Ces résultats ont été utilisés dans le calcul d'abondance de C6H6 dans la thermosphère de Titan comme indiqué dans les paragraphes précédents.En résumé, l'analyse des observations UVIS présentées contribuent à la caractérisation de la haute atmosphère à travers des profils de N2, de températures thermosphériques et des profils de différents hydrocarbures et nitrile. Ces données d'observation aideront à contraindre les modèles photochimiques. Les profils d'abondance donnés en fonction de différentes coordonnées géographiques et temporelles pourront être utilisés pour étudier plus avant la variabilité atmosphérique. Les résultats de ce travail aideront donc à la compréhension de la composition et la dynamique de l'haute atmosphère de Titan. Cette connaissance, combinée avec des informations sur la basse atmosphère et la surface de Titan, aidera à comprendre l'évolution de molécules organiques dans ce corps céleste abiotique voisin.Les résultats de ce travail aideront donc à la compréhension de la composition et la dynamique de la haute atmosphère de Titan. Cette connaissance, combinée avec des informations sur la basse atmosphère et la surface de Titan, aidera à comprendre l'évolution de molécules organiques dans ce corps céleste abiotique voisinThis PhD project focuses on the study of the upper atmosphere of Titan from the analysis of Cassini-UVIS data and laboratory measurements of absorption cross sections.A characterization of the UVIS instrument and observations was necessary. Data from the Far UltraViolet (FUV) and Extreme UltraViolet (EUV) channels of UVIS were analyzed and corrected for instrument effects. From the analysis of 8 solar occultations in EUV, N2 and CH4 number density profiles were derived with an inversion regularization method. Temperatures were obtained from the N2 profiles assuming an isothermal upper atmosphere. Stellar occultations in FUV were modeled and a density retrieval technique characterized. The possibility of detection for different molecules (some of them not detected by this technique before) was analyzed. Then, using a Levenberg-Marquardt minimization algorithm, column density profiles for different hydrocarbons and nitriles, and optical depth of aerosols were obtained from simulated data. The column densities and optical depth were inverted with a regularization method to obtain number density profiles for the molecules and extinction profiles for the aerosols. The procedure was finally applied to 2 stellar occultations measured by UVIS. The species studied are CH4, C2H2, HCN, C2H4, C4H2, C6H6, HC3N, CH3, and aerosols (AER). The profiles from the stellar and solar occultations were obtained for different times and locations. The temperatures derived were analyzed as a function of geographical and temporal variables---latitude, longitude, date of observation, etc.---without a clear correlation with any of them, although a trend of decreasing temperature towards the poles could be observed. The globally averaged temperature obtained is (144 +/- 2) K. Atmospheric variability was discussed on the light of these results.Benzene (C6H6) is an important molecule detected in Titan's atmosphere because it is thought to be intermediate between the gas and solid particle formation. Measurements of absorption in the ultraviolet by benzene gas, at temperatures covering the range from room temperature to 215 K, were performed in different international facilities. From them, benzene absorption cross sections were derived and analyzed in terms on the transitions observed. No significant variation with measurement temperature was observed. Implications of this results for the identification of benzene in Titan's thermosphere by UVIS were discussed. The absorption cross sections were used in the derivation of C6H6 abundances in Titan's thermosphere commented above.In summary the analysis of UVIS observations presented contribute to the characterization of the upper atmosphere through N2 density profiles, thermospheric temperatures, density profiles of minor species and extinction profiles from aerosols. This observational data will help to constrain and contrast photochemical models. The abundance profiles and temperatures given for different geographical and temporal coordinates can be used to further study the atmospheric variability. As a whole, the results of this work are expected to help in the understanding of Titan's upper atmospheric composition and dynamics. This knowledge, combined with information about Titan's lower atmosphere and surface, will help to understand the evolution of organic molecules in this neighboring abiotic celestial body
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Holzschuh, Marcelo Leandro [UNESP]. "Recuperação de perfis atmosféricos a partir de ocultação GPS: fundamentos, implementação e análise de resultados." Universidade Estadual Paulista (UNESP), 2007. http://hdl.handle.net/11449/86793.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
A ocultação, um fenômeno pelo qual um corpo celeste deixa de ser visto em razão da sobreposição de um outro, começou a ser usada para estudar a atmosfera de outros planetas há vários anos. Com o advento dos satélites artificiais GPS (Global Positioning System), em conjunto com os satélites LEO (Low Earth Orbiting), surge a Rádio Ocultação GPS (ROGPS), abrindo-se novas perspectivas para as pesquisas sobre o clima e previsão de tempo. Na RO GPS, os sinais que são enviados pelo satélite GPS e recebidos no satélite LEO sofrem os efeitos da troposfera e da ionosfera ao atravessarem a atmosfera terrestre, afetando a fase e a amplitude das ondas dos sinais envolvidos. A propagação do sinal sofre refração formando uma linha curva entre o satélite transmissor e o receptor, o que permite calcular diferentes índices de refratividade, os quais carregam informações da composição da atmosfera terrestre. A partir de perfis desses índices de refratividade é possível extrair perfis de temperatura, umidade e pressão atmosférica na troposfera, além da distribuição na densidade de elétrons na ionosfera terrestre. Vários trabalhos foram realizados para verificar a qualidade dos perfis atmosféricos obtidos com o emprego do satélite CHAMP (Challenging Minisatellite Payload of Geophysical Research and Application), um satélite LEO, em diversas regiões do globo. Nesse trabalho, objetiva-se investigar e implementar a técnica de ocultação GPS, bem como avaliar a qualidade de perfis de temperatura obtidos com o satélite CHAMP sobre a América do Sul, comparando-os com perfis de radiossondas e perfis provenientes da condição inicial do modelo de Previsão Numérica de Tempo (PNT). A implementação da recuperação de um perfil da atmosfera foi realizada utilizando o código C/A para o cálculo do ângulo de curvatura e o parâmetro de impacto, cujos valores aproximados foram 0,043° e 6381 km, respectivamente.
The occultation, phenomenon in which a celestial body in not seen because of the superposition of another one, started being used several years ago to study the atmosphere of other planets. With the advent of GPS (Global Positioning System) satellites, together with the LEO (Low Earth Orbit) satellites, the GPS Radio Occultation (GPS-RO) arises, in order to obtain new perspectives in studies related to climate and weather forecast. In GPS-RO, the signals sent by the GPS satellite and received by the LEO satellite are disturbed by the ionosphere and troposphere while cross the terrestrial atmosphere, this affects the phase and the amplitude from the involved signals. The signals propagation is affected by refraction, this generates a bending angle between the transmitter and receiver satellites, allowing computing different refractivity index, which carry information about the terrestrial atmosphere composition. Using these profiles of refractivity index is possible to extract profiles of temperature, humidity, atmospheric pressure in the troposphere, and to obtain the electronic density distribution in terrestrial ionosphere. Several works were realized to verify the quality of atmospheric profiles obtained using the CHAMP (Challenging Minisatellite Payload of Geophysical Research and Application) satellite, LEO satellite, in several regions of the globe. In this research the goal is to investigate and implement the GPS occultation technique, and additionally to evaluate the quality of the temperature profiles obtained by CHAMP satellite over the South of America, comparing them with the RSO (Radiosonde) profiles and with the profiles obtained by the initial condition of Numeric Weather Prediction (NWP) model.
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raynaud, Elisabeth. "Etude de la haute atmosphère polaire de Jupiter par occultation stellaire et spectroimagerie infrarouge." Phd thesis, Université Paris-Diderot - Paris VII, 2003. http://tel.archives-ouvertes.fr/tel-00006438.
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Cette thèse vise à mieux connaître la structure thermique de la haute atmosphère jovienne dans les régions polaires . Pour cela, deux points sont abordés : la caractérisation des ondes de gravité stratosphériques, et les variations de température dans l'ionosphère. L'étude d'occultations stellaires a permis d'obtenir des profils de température à haute altitude pour les deux hémisphères. Ces profils confirment l'augmentation de température stratosphérique lorsqu'on se rapproche des pôles. L'analyse temps-échelle de ces profils de température a permis de détecter des ondes de gravité, et d'en caractériser certains modes. Cette thèse développe également des méthodes d'étude, caractérise les limites de chaque méthode, et définit des stratégies d'observations pour la détection d'ondes de gravité. L'analyse de données du spectro-imageur BEAR portant sur les raies d'émission de H3+ dans l'infrarouge proche a ensuite permis de mettre en évidence des variations latitudinales et longitudinales de la température ionosphériques dans la zone aurorale, et de les relier aux variations d'abondance de H3+. Les avancées dans les deux domaines permettent de quantifier l'apport énergétique du déferlement d'ondes de gravité d'une part, et des précipitations aurorales d'autre part, au bilan thermique des thermosphères des planètes géantes.
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Ge, Shengjie. "GPS radio occultation and the role of atmospheric pressure on spaceborne gravity estimation over Antarctica." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1149070384.
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Primavera, Asia, and Melania Pugliese. "A ray-tracing method for in-situ radio occultation experiments: analysis of MAVEN’s ROSE data." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2022.
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Interplanetary exploration has grown during the last years and one of the most popular destination has been Mars planet. A lot of processes occurring in Mars’ atmosphere and on its surface are still unknown. Therefore, the radio occultation technique is used to study the structure of the planet’s atmosphere, consisting in reconstructing the path of the radio signal transmitted by the spacecraft when it travels inside the atmosphere. The goal of this thesis is to test the ray-tracing method for in-situ occultations in order to prove its reliability, suitability, and its uniqueness compared to other methods. This is demonstrated by pursuing an analysis of some in-situ occultations performed by MAVEN mission in 2017. The entire work is done on MATLAB, with the help of the NASA Navigation and Ancillary Information Facility SPICE toolkit. As part of this investigation, the obtained atmospheric profiles are compared with those already available in literature, in order to demonstrate the validity of the algorithm.
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Rosich, Garrett Kyle. "Evaluation of GLO: a Solar Occultation Instrument for Measuring Atmospheric Trace Species on CubeSat Missions." Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/78013.
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CubeSats provide an inexpensive means for space-based research. However, optimal mission design depends on minimizing payload size and power. This thesis investigates the GLO (GFCR (Gas Filter Correlation Radiometry) Limb Occultation) prototype, a new small-form-factor design that enables sub-kilometer resolution of the vertical profile of atmospheric trace species to determine radiative influences. This technology improves SWAP (Size, Weight, And Power) over heritage SOFIE and HALOE instruments and provides a cost-effective alternative for solar occultation limb monitoring.
A python script was developed to analyze solar intensity through GLO telescope channels. Non-uniform aerosol images used a peak intensity algorithm compared to the edge detection function designed for GFCR channels. Scaling corrections were made for beam splitter inaccuracy and SNR was characterized for frame collection. Different cameras were tested to weigh accuracy versus cost of a camera baffle. Using the Langley plot method, solar intensity versus changes in the solar zenith angle were measured for extrapolation of optical depths. AERONET, a network of ground-based sun photometers measuring atmospheric aerosols, was used for aerosol optical depth validation. Spectral Calculator transmission data allowed for GFCR vacuum channel comparison, gas cell spectral analysis, and gas cell to vacuum channel optical depth examination. Ground testing provided promising results with the low-cost prototype. It will be further evaluated through a balloon flight demonstration using a flight-ready GLO instrument. Additionally, analysis for the DUSTIE mission is planned and simulated using STK and Matlab. This includes CubeSat bus selection, orbit analysis for occultation occurrences, power budgeting, and communication capabilities.Master of Science
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Holzschuh, Marcelo Leandro. "Recuperação de perfis atmosféricos a partir de ocultação GPS : fundamentos, implementação e análise de resultados /." Presidente Prudente : [s.n.], 2007. http://hdl.handle.net/11449/86793.
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Resumo: A ocultação, um fenômeno pelo qual um corpo celeste deixa de ser visto em razão da sobreposição de um outro, começou a ser usada para estudar a atmosfera de outros planetas há vários anos. Com o advento dos satélites artificiais GPS (Global Positioning System), em conjunto com os satélites LEO (Low Earth Orbiting), surge a Rádio Ocultação GPS (ROGPS), abrindo-se novas perspectivas para as pesquisas sobre o clima e previsão de tempo. Na RO GPS, os sinais que são enviados pelo satélite GPS e recebidos no satélite LEO sofrem os efeitos da troposfera e da ionosfera ao atravessarem a atmosfera terrestre, afetando a fase e a amplitude das ondas dos sinais envolvidos. A propagação do sinal sofre refração formando uma linha curva entre o satélite transmissor e o receptor, o que permite calcular diferentes índices de refratividade, os quais carregam informações da composição da atmosfera terrestre. A partir de perfis desses índices de refratividade é possível extrair perfis de temperatura, umidade e pressão atmosférica na troposfera, além da distribuição na densidade de elétrons na ionosfera terrestre. Vários trabalhos foram realizados para verificar a qualidade dos perfis atmosféricos obtidos com o emprego do satélite CHAMP (Challenging Minisatellite Payload of Geophysical Research and Application), um satélite LEO, em diversas regiões do globo. Nesse trabalho, objetiva-se investigar e implementar a técnica de ocultação GPS, bem como avaliar a qualidade de perfis de temperatura obtidos com o satélite CHAMP sobre a América do Sul, comparando-os com perfis de radiossondas e perfis provenientes da condição inicial do modelo de Previsão Numérica de Tempo (PNT). A implementação da recuperação de um perfil da atmosfera foi realizada utilizando o código C/A para o cálculo do ângulo de curvatura e o parâmetro de impacto, cujos valores aproximados foram 0,043° e 6381 km, respectivamente.Abstract: The occultation, phenomenon in which a celestial body in not seen because of the superposition of another one, started being used several years ago to study the atmosphere of other planets. With the advent of GPS (Global Positioning System) satellites, together with the LEO (Low Earth Orbit) satellites, the GPS Radio Occultation (GPS-RO) arises, in order to obtain new perspectives in studies related to climate and weather forecast. In GPS-RO, the signals sent by the GPS satellite and received by the LEO satellite are disturbed by the ionosphere and troposphere while cross the terrestrial atmosphere, this affects the phase and the amplitude from the involved signals. The signals propagation is affected by refraction, this generates a bending angle between the transmitter and receiver satellites, allowing computing different refractivity index, which carry information about the terrestrial atmosphere composition. Using these profiles of refractivity index is possible to extract profiles of temperature, humidity, atmospheric pressure in the troposphere, and to obtain the electronic density distribution in terrestrial ionosphere. Several works were realized to verify the quality of atmospheric profiles obtained using the CHAMP (Challenging Minisatellite Payload of Geophysical Research and Application) satellite, LEO satellite, in several regions of the globe. In this research the goal is to investigate and implement the GPS occultation technique, and additionally to evaluate the quality of the temperature profiles obtained by CHAMP satellite over the South of America, comparing them with the RSO (Radiosonde) profiles and with the profiles obtained by the initial condition of Numeric Weather Prediction (NWP) model.
Orientador: João Francisco Galera Monico
Coorientador: Luiz Fernando Sapucci
Banca: Hisao Takahashi
Banca: José Tadeu Garcia Tommaselli
Mestre
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Siddiqui, Hannana. "Violence against minority women : tackling domestic violence, forced marriage and 'honour' based violence." Thesis, University of Warwick, 2014. http://wrap.warwick.ac.uk/64295/.
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This commentary outlines how my published works have contributed to knowledge on violence against black and minority ethnic (BME) or minority women in the UK, particularly in relation to domestic violence, forced marriage and so called 'honour' based violence (HBV). They help to define and enhance our understanding of these issues. In addition, they have critiqued multiculturalism and influenced, advocated and developed the former Home Office Minister, Mike O'Brien's concept of 'mature multiculturalism' (Parliamentary Debates, 1999; also cited in Home Office, 2000:10), and utilised the theoretical framework of intersectionality (Crenshaw, 1989 and 1991) to address these problems. I have also located my works within the framework of violence against women and girls (VAWG), secularism, equalities and human rights. My publications have reflected upon and influenced policy, practice and research, and as such, contributed to documenting the history and achievements of black feminism.
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Harrington, Joseph. "Planetary infrared observations : the occultation of 28 Sagittarii by Saturn and the dynamics of Jupiter's atmosphere." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/57957.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1995.Includes bibliographical references (p. 219-222).
by Joseph Harrington.
Ph.D.
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Belloul, Bachir. "Methode de mesure des parametres atmospheriques par occultation de signaux satellites du systeme de positionnement gps." Paris 6, 1996. http://www.theses.fr/1996PA066468.
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Le systeme de positionnement gps offre une opportunite unique en termes de mesure de parametres atmospheriques comme l'indice de refraction ou la temperature dans le domaine d'altitudes situe entre sol et la stratopause. La mesure s'effectue en occultation lorsque l'un des satellites du gps se couche (ou se leve) derriere la terre par rapport a un recepteur monte sur un satellite en orbite basse. Les signaux radio emis par le satellite gps traversent alors l'atmosphere et sont ralentis, en meme temps qu'ils sont courbes par les changements des proprietes refractives du milieu. En associant cette mesure au deplacement du recepteur autour de son orbite, on obtient alors un profil dont chaque point sera le resultat d'une integration horizontale le long de la trajectoire du signal. Ce travail consiste a etudier cette methode de mesure sous tous ses aspects. On se penchera notamment sur le bilan des erreurs instrumentales mais aussi sur les erreurs liees a la nature du milieu traverse. Les etapes de l'inversion des profils de retard de phase en profils d'indice de refraction et de temperature seront developpees. On presentera finalement les resultats d'analyses de validation faites a partir de mesures obtenues par l'experience gps-meteorology (gps/met). Les profils de temperature restitues a partir de cette experience sont compares a des profils mesures in situ par radiosondage haute resolution et par lidar. Une etude quantitative par comparaison avec les analyses du modele ecmwf ont ete realisees. Cette etude montre que la moyenne des ecarts en temperature reste inferieure a 0. 5k sur le domaine 12-25km et que c'est dans l'hemisphere nord, ou la distribution spatiale de radiosondages est la plus dense, que les ecarts en temperature sont les plus faibles. On montre aussi que cette methode peut constituer un outil efficace pour l'etude du champ ondulatoire global de la stratosphere
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Brammer, Sara K. Berkel LaVerne A. "Domestic violence offenders' opinions of intimate partner violence." Diss., UMK access, 2006.
Find full textAbstract:
Thesis (Ph.D.)--School of Education. University of Missouri--Kansas City, 2006."A dissertation in counseling psychology." Advisor: LaVerne Berkel. Typescript. Vita. Title from "catalog record" of the print edition Description based on contents viewed Jan. 26, 2007. Includes bibliographical references (leaves 112-134 ). Online version of the print edition.
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Gregory, Linda Ellen. "An etiology of domestic violence and non-violence." Thesis, Gregory, Linda Ellen (2003) An etiology of domestic violence and non-violence. PhD thesis, Murdoch University, 2003. https://researchrepository.murdoch.edu.au/id/eprint/51307/.
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This thesis research has examined what male social workers believe to be the causes of domestic violence and, more importantly, what they believe causes non-violence between partners. The research was a qualitative study of interviews with men, mostly social workers, who worked with both perpetrators and victims of domestic violence. The aims of the research are to provide some answers as to why, despite the attention given to domestic violence and the provision of DV treatment programs by social workers and counsellors, in both public and private sectors, the problem remains intractable.
Twenty men who worked in the area of domestic violence were interviewed, individually, with a series of twenty five questions. Two leaders of a local men's group were also interviewed. The main discussion topics for all these men were their views on the causes of domestic violence and then, more positively, what they felt were the reasons why most men, including themselves, were physically non-violent.
Investigating what these men feel causes domestic violence and nonviolence may provide an insight into what brings most men in our society to be physically non-violent to their partners. Hopefully, this information can be used to implement factors into families and society to work towards non-violence.
The interviewees' definitions of domestic violence were discussed, and what causes it. What causes non-violence, and scripting was positioned by them as the major factor in both. Within traditional Western male scripting lies males' sense of entitlement to privileged positions in their families and society. A question about violence surfaced. What is the purpose of violence? For the purpose of this research violence is defined as person or persons insisting on getting what they want, as a result of their claim to have the right to have it.
Male entitlement to privileges was identified by five of the men as being problematical and a central cause of domestic violence. The other fifteen interviewees, as well as the two men from the men's groups, accepted but appeared to discount the issue on varying levels. Whilst five men saw the existence of male privilege as a significant problem that needs changing, ten of the others saw the existence of it, but defined it as normal, and therefore by implication, believe it will be maintained, or that it can not be changed.
One of the underpinning dynamics revealed in this research is that the issue of male privilege is apparent to some and invisible to others, in the context of domestic violence this is going to be a problem.
In dealing with domestic violence we have to not simply invest in putting more social workers in the DV area; they need to be properly and adequately trained, and adequately committed to a treatment model which foregrounds male privilege [and does not present men as victims.] We need public investment in DV counselling, training and accreditation. We need to address the issue of male privilege in the whole of society and to focus on creating equality of power in relationships between men and women.
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Bellucci, Aurélie. "Analyse d'occultations solaires et stellaires par Titan observées par l'instrument Cassini/VIMS." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2008. http://tel.archives-ouvertes.fr/tel-00347235.
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L'observation d'occultations du Soleil et d'étoiles par Titan permet d'étudier l'atmosphère épaisse de ce satellite de Saturne du point de vue de sa composition en gaz et en aérosols. Le principe de ces observations, réalisées par le spectro-imageur visible/infrarouge VIMS de la sonde Cassini, est de mesurer la transmission du flux solaire ou stellaire à travers l'atmosphère de Titan. Les données sont constituées de courbes de lumière à différentes longueurs d'onde et de spectres infrarouges pour différentes altitudes de visée. L'étude des courbes de lumière montre qu'il s'agit d'occultations par absorption et non par réfraction différentielle comme c'est le cas pour les occultations observées depuis la Terre. La baisse de signal observée est donc due à l'absorption du flux lumineux par le gaz et les aérosols de l'atmosphère.Les spectres en transmission présentent des bandes d'absorption du méthane à 1,2, 1,4, 1,7, 2,3 et 3,3 µm et du monoxyde de carbone à 4,7 µm. Un code de transfert radiatif en géométrie sphérique et utilisant la méthode de calcul raie par raie a été développé afin de modéliser les bandes observées. L'étude du méthane est centrée principalement sur la bande à 2,3 µm. Au-dessus de 200 km, nos données sont compatibles avec une abondance uniforme de 1,4 - 1,6% telle que mesurée par d'autres instruments. En dessous de 200 km, un effet systématique mal compris empêche une mesure fiable. La molécule de CO est détectée en dessous de 180 km. Une abondance de 33±10 ppm est mesurée entre 70 et 130 km d'altitude. En dessous de 500 km environ, une absorption supplémentaire, centrée sur 3,4 µm se superpose à la bande du méthane à 3,3 µm. Cette bande caractérise la vibration des liaisons C - H au sein de longues chaînes aliphatiques rattachées à de larges molécules organiques qui composent les aérosols.
L'absorption des aérosols fixe le niveau de continu des spectres étudiés. Celle-ci est plus forte aux courtes longueurs d'onde et augmente lorsque l'altitude décroît. Un code d'inversion du continu a été développé afin de déterminer les profils de densité des aérosols et de modéliser leur transmission. L'hypothèse de départ est que les aérosols sont des agrégats fractals composés de sphères de 0,05 µm de rayon dont les propriétés optiques sont celles des tholins de Khare et al. (1984). Les modèles de transmission obtenus révèlent que seuls les agrégats comportant plus de 1 000 sphères sont compatibles avec les observations. De plus, l'absence des deux absorptions caractéristiques à 3 et 4,6 µm dans nos données soulignent les différences significatives entre les tholins et les aérosols réels. Les profils de densité des aérosols indiquent une augmentation exponentielle en dessous de 450 km, caractérisée par une échelle de hauteur de l'ordre de 60 km pour les données de l'occultation solaire (71°S) et de l'ordre de 50 km pour celle de l'occultation de Gamma Crucis (24°N). L'écart constaté est peut-être attribuable à la différence de latitude entre ces deux observations. Enfin, les données de l'occultation rasante d'Antarès comportent de
nombreuses variations de flux rapides et intenses (« spikes ») : elles sont attribuées à des ondes de gravité se propageant dans l'atmosphère de Titan.
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Matusov, E., and Paul W. Sullivan. "Pedagogical violence." Springer, 2019. http://hdl.handle.net/10454/17533.
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YesIn this paper, we consider the phenomenon of “pedagogical violence” — infliction of physical, social, emotional, or psychological pains, or threat of such pains that is either the means for or non-accidental by-products of education used on a systematic basis. Pedagogical violence is often used for promoting certain desired learning in students. Alternatively, it can emerge as a violent reaction in students and teachers to particular educational settings directed against other students or teachers. In this paper, we review some of the debates and controversial issues around pedagogical violence, and we use a variety of illustrative examples to explore in more detail what pedagogical violence means in particular contexts. We argue that pedagogical violence is a natural consequence of alienated instrumental education. We will look at teachers’ desire to avoid physical and psychosocial pedagogical violence. We specifically consider diverse forms of psychosocial pedagogical violence and its issues such as: summative assessment, epistemological pedagogical violence, students’ ambivalence around pedagogical violence, rehabilitating/avoiding pedagogical violence through a carnival. We finish with a reflection about what can be done to minimize pedagogical violence. Our analysis heavily relies on the Bakhtinian theoretical framework of critical ontological dialogism.
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Muller, Doyle Sylvia M. "Workplace violence." Instructions for remote access. Click here to access this electronic resource. Access available to Kutztown University faculty, staff, and students only, 1999. http://www.kutztown.edu/library/services/remote_access.asp.
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Thesis (M.P.A.)--Kutztown University of Pennsylvania, 1999.Source: Masters Abstracts International, Volume: 45-06, page: 2953. Typescript. Abstract precedes thesis as preliminary leaves i-iii. Includes bibliographical references (178).
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Faber, Antonia [Verfasser]. "Gravity wave analysis with GPS radio occultation data from FORMOSAT-3 / COSMIC / Antonia Faber. Deutsches GeoForschungsZentrum GFZ." Potsdam : Deutsches GeoForschungsZentrum GFZ, 2013. http://d-nb.info/1038685354/34.
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Zalucha, Angela M. (Angela Marie). "Analysis of light curves from the 2003 Nov 14 occultation by Titan of TYC 1343-1855-1." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/42065.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2007.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 17-18).
We observed a stellar occultation by Titan on 2003 November 14 from La Palma Observatory using ULTRACAM with three Sloan filters: u', g', and i' (358, 487, and 758 nm, respectively). The occultation probed latitudes 2°S and 1°N during immersion and emersion, respectively. A prominent central flash was present in only the i' filter, indicating wavelength-dependent atmospheric extinction. We inverted the light curves to obtain six lower-limit temperature profiles between 335 and 485 km (0.04 and 0.003 mb) altitude. The i' profiles agreed with the temperature measured by the Huygens Atmospheric Structure Instrument [Fulchignoni, M., and 43 colleagues, 2005. Nature 438, 785-791] above 415 km (0.01 mb). The profiles obtained from different wavelength filters systematically diverge as altitude decreases, which implies significant extinction in the light curves. Applying an extinction model [Elliot, J.L., Young, L.A., 1992. Astron. J. 103, 991-1015] gave the altitudes of line of sight optical depth equal to unity: 396 ± 7 km and 401 ± 20 km (u' immersion and emersion); 354 ± 7 km and 387 ± 7 km (g' immersion and emersion); and 336 ± 5 km and 318 ± 4 km (i' immersion and emersion). Further analysis showed that the optical depth follows a power law in wavelength with index 1.3 ± 0.2. We present a new method for determining temperature from scintillation spikes in the occulting body's atmosphere. Temperatures derived with this method are equal to or warmer than those measured by the Huygens Atmospheric Structure Instrument. Using the highly structured, three-peaked central flash, we confirmed the shape of Titan's middle atmosphere using a model originally derived for a previous Titan occultation [Hubbard, W.B., and 45 colleagues, 1993. Astron. Astrophys. 269, 541-563].
by Angela M. Zalucha.
S.M.
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Ludwig, Barbosa Vinícius. "Effects of Small-Scale Ionospheric Irregularities on GNSS Radio Occultation Signals : Evaluations Using Multiple Phase Screen Simulator." Licentiate thesis, Blekinge Tekniska Högskola, Institutionen för matematik och naturvetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-18907.
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Radio Occultation (RO) is a remote sensing technique which uses Global Navigation Satellite System (GNSS) signals tracked by a Low-Earth Orbit (LEO) satellite to sound the earth's atmosphere both in low (troposphere, stratosphere) and high (ionosphere) altitudes. GNSS-RO provides global coverage and SI traceable measurements of atmospheric data with high-vertical resolution. Refractivity, dry temperature, pressure and water vapour profiles retrieved from RO measurements have a relevant contribution in Numerical Weather Prediction (NWP) systems and in climate-monitoring. Due to the partial propagation through the ionosphere, a systematic bias is added to the lower atmospheric data product. Most of this contribution is removed by a linear combination of data for two frequencies. In climatology studies, one can apply a second-order correction - so called κ-correction - which relies on a priori information on the conditions in the ionosphere. However, both approaches do not remove high-order terms in the error due to horizontal gradient and earth's geomagnetic fields. The remaining residual ionospheric error (RIE) and its systematic bias in RO atmospheric data is a well-known issue and its mitigation is an open research topic. In this licentiate dissertation, the residual ionospheric error after the standard correction is evaluated with computational simulations using a wave optics propagator (WOP). Multiple Phase Screen (MPS) method is used to simulate occultation events in different ionospheric scenarios, e.g. quiet and disturbed conditions. Electron density profiles (EDP) assumed in simulations are either defined by analytical equations or measurements. The disturbed cases are modelled as small-scale irregularities within F-region in two different ways: as sinusoidal fluctuations; and by using a more complex approach, where the irregularities follow a single-slope power-law that yields moderate to strong scintillation in the signal amplitude. Possible errors in MPS simulations assuming long segment of orbit and ionosphere are also evaluated. The results obtained with the sinusoidal disturbances show minor influence in the RIE after the standard correction, with the major part of the error due to the F-region peak. The implementation of the single-slope power-law is validated and the fluctuations obtained in simulation show good agreement to the ones observed in RO measurements. Finally, an alternative to overcome limitations in MPS simulations considering occultations with long segment of orbit and ionosphere is introduced and validated. The small-scale irregularities modelled in F-region with the power-law can be added in simulations of a large dataset subjected to κ-correction, in order to evaluate the RIE bending angle and the consequences in atmospheric parameters, e.g. temperature.NRPF-3, Rymdstyrelsen, 241/15