Дисертації з теми "Ionosphere system"
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Rosenqvist, Lisa. "Energy Transfer and Conversion in the Magnetosphere-Ionosphere System." Doctoral thesis, Uppsala University, Department of Astronomy and Space Physics, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8716.
Повний текст джерелаMagnetized planets, such as Earth, are strongly influenced by the solar wind. The Sun is very dynamic, releasing varying amounts of energy, resulting in a fluctuating energy and momentum exchange between the solar wind and planetary magnetospheres. The efficiency of this coupling is thought to be controlled by magnetic reconnection occurring at the boundary between solar wind and planetary magnetic fields. One of the main tasks in space physics research is to increase the understanding of this coupling between the Sun and other solar system bodies. Perhaps the most important aspect regards the transfer of energy from the solar wind to the terrestrial magnetosphere as this is the main source for driving plasma processes in the magnetosphere-ionosphere system. This may also have a direct practical influence on our life here on Earth as it is responsible for Space Weather effects. In this thesis I investigate both the global scale of the varying solar-terrestrial coupling and local phenomena in more detail. I use mainly the European Space Agency Cluster mission which provide unprecedented three-dimensional observations via its formation of four identical spacecraft. The Cluster data are complimented with observations from a broad range of instruments both onboard spacecraft and from groundbased magnetometers and radars.
A period of very strong solar driving in late October 2003 is investigated. We show that some of the strongest substorms in the history of magnetic recordings were triggered by pressure pulses impacting a quasi-stable magnetosphere. We make for the first time direct estimates of the local energy flow into the magnetotail using Cluster measurements. Observational estimates suggest a good energy balance between the magnetosphere-ionosphere system while empirical proxies seem to suffer from over/under estimations during such extreme conditions.
Another period of extreme interplanetary conditions give rise to accelerated flows along the magnetopause which could account for an enhanced energy coupling between the solar wind and the magnetosphere. We discuss whether such conditions could explain the simultaneous observation of a large auroral spiral across the polar cap.
Contrary to extreme conditions the energy conversion across the dayside magnetopause has been estimated during an extended period of steady interplanetary conditions. A new method to determine the rate at which reconnection occurs is described that utilizes the magnitude of the local energy conversion from Cluster. The observations show a varying reconnection rate which support the previous interpretation that reconnection is continuous but its rate is modulated.
Finally, we compare local energy estimates from Cluster with a global magnetohydrodynamic simulation. The results show that the observations are reliably reproduced by the model and may be used to validate and scale global magnetohydrodynamic models.
Gane, Stuart Carlos. "Continuous pulsation dynamics in the high-latitude magnetosphere-ionosphere system." Thesis, University of Leicester, 2011. http://hdl.handle.net/2381/9695.
Повний текст джерелаNakata, Hiroyuki. "The standing toroidal mode oscillations in the magnetosphere-ionosphere system." 京都大学 (Kyoto University), 2000. http://hdl.handle.net/2433/157196.
Повний текст джерела本文データは平成22年度国立国会図書館の学位論文(博士)のデジタル化実施により作成された画像ファイルを基にpdf変換したものである
Kyoto University (京都大学)
0048
新制・課程博士
博士(理学)
甲第8164号
理博第2186号
新制||理||1156(附属図書館)
UT51-2000-F68
京都大学大学院理学研究科地球惑星科学専攻
(主査)教授 藤田 茂, 教授 荒木 徹, 助教授 町田 忍
学位規則第4条第1項該当
Brown, Neil E. "Sequential phased estimation of ionospheric path delays for improved ambiguity resolution over long GPS baselines /." Connect to thesis, 2006. http://eprints.unimelb.edu.au/archive/00003170.
Повний текст джерелаMoses, Jack. "NAVSTAR Global Positioning System Applications for Worldwide Ionospheric Monitoring." International Foundation for Telemetering, 1992. http://hdl.handle.net/10150/611941.
Повний текст джерелаThe ionosphere is a critical link in the earth's environment for space-based navigation, communications and surveillance systems. Signals sent down by the GPS satellites can provide an excellent means of studying the complex physical and chemical processes that take place there. GPS uses two frequencies to ascertain signal delays passing through the ionosphere. These are measured as errors and used to correct position solutions. Since this process is a means of measuring columns of Total Electron Content (TEC), multiple top-soundings from the GPS constellation could provide significant detail of the ionospheric pattern and possibly lead to enhancement of predictions for selectable areas and sites. This paper addresses transforming the GPS propagation delays (errors) into TEC and providing TEC contours on a PC-style workstation in real and integrated time and discusses a worldwide ionospheric network monitoring system.
Clark, Paul Derrick John. "A robust MFSK transmission system for aeromobile HF radio channels." Thesis, University of Hull, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310321.
Повний текст джерелаBotai, Ondego Joel. "Ionospheric total electron content variability and its influence in radio astronomy." Thesis, Rhodes University, 2006. http://hdl.handle.net/10962/d1005258.
Повний текст джерелаHabarulema, John Bosco. "A feasibility study into total electron content prediction using neural networks." Thesis, Rhodes University, 2008. http://hdl.handle.net/10962/d1005251.
Повний текст джерелаWyllie, Scott John, and scott wyllie@rmit edu au. "Modelling the Temporal Variation of the Ionosphere in a Network-RTK Environment." RMIT University. Mathematical and Geospatial Sciences, 2007. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080617.161323.
Повний текст джерелаTetewsky, Avram Ross Jeff Soltz Arnold Vaughn Norman Anszperger Jan O'Brien Chris Graham Dave Craig Doug Lozow Jeff. "Making sense of inter-signal corrections : accounting for GPS satellite calibration parameters in legacy and modernized ionosphere correction algorithms /." [Eugene, Ore. : Gibbons Media & Research], 2009. http://www.insidegnss.com/auto/julyaug09-tetewsky-final.pdf.
Повний текст джерела"July/August 2009." Web site title: Making Sense of GPS Inter-Signal Corrections : Satellite Calibration Parameters in Legacy and Modernized Ionosphere Correction Algorithms.
PAIVA, JOSE ANTONIO GODINHO. "EFFECT OF THE IONOSPHERE OF LOW LATITUDES IN GPS - SBAS (GLOBAL SYSTEM POSITIONING - SPACE BASED AUGMENTATION SYSTEM)." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2004. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=5863@1.
Повний текст джерелаA ionosfera de baixas latitudes tem características que poderiam causar problemas à operação do GPS/SBAS. Entre elas se encontra a anomalia equatorial, cuja densidade eletrônica pode apresentar intensos gradientes horizontais (e, portanto, no índice de refração do meio). Estes gradientes podem ser intensos o suficiente para introduzir erros nas previsões resultantes do GPS/SBAS. Para avaliar este problema, foi desenvolvido um programa de simulação em computador que integra modelos para: (i) a previsão das posições dos satélites da constelação GPS; (ii) a evolução temporal e espacial da densidade eletrônica da ionosfera equatorial; e (iii) uma rede de estações de referência de posições fornecidas para analisar os efeitos da anomalia equatorial sobre os erros causados pela ionosfera nos sinais dos satélites GPS recebidos pelas estações. Em cada passo da simulação, diversos procedimentos são realizados. Estes procedimentos são repetidos um grande número de vezes e, ao final da simulação, estatísticas dos erros são apresentadas. Este programa de simulação em computador foi utilizado para analisar a influência do número de estações de referência, assim como de suas localizações, nos erros de posicionamento de aeronaves.
The low-latitude ionosphere has some features that could cause problems even to the joint GPS/SBAS operation. Among them, one finds the equatorial anomaly, whose electronic density - and thus its refractive index - can present intense horizontal gradients. These gradients can be intense enough to induce errors in the predictions by the GPS/SBAS. To analyze this problem, a computer simulation program has been developed. This program integrates models for: (i) forecasting the satellite orbital positions of the GPS constellation; (ii) the temporal and spatial evolution of the electronic density of the low-latitude ionosphere; and (iii) a given network of reference stations to analyze the effects of the equatorial anomaly on the GPS satellite signals received by the stations and users. In each step of the simulation, several procedures are performed. These procedures are repeated several times and, at the end of the simulation, error statistics are presented. This computer simulation program has been used to analyze the influence of the equatorial anomaly and of the number and layout of reference stations upon the errors in aircraft positions provided by the GPS/SBAS.
Smith, Andrew M. "Global navigation satellite system (GNSS) signal simulator : an analysis of the effects of the local environment and atmosphere on receiver positioning." Thesis, University of Bath, 2007. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.512261.
Повний текст джерелаKinrade, Joe. "Ionospheric imaging and scintillation monitoring in the Antarctic and Arctic." Thesis, University of Bath, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619217.
Повний текст джерелаPalmer, David J. "Topside sounding on a microsatellite." Thesis, University of Surrey, 1997. http://epubs.surrey.ac.uk/844211/.
Повний текст джерелаScoffield, Hannah Clare. "Ultra low frequency waves in the magentosphere-ionosphere system : a joint space- and ground-based investigation." Thesis, University of Leicester, 2005. http://hdl.handle.net/2381/30692.
Повний текст джерелаQahwash, Murad M. "High frequency communication system modeling and performance enhancement, employing novel adaptive DSP techniques." Doctoral diss., University of Central Florida, 2002. http://digital.library.ucf.edu/cdm/ref/collection/RTD/id/1383.
Повний текст джерелаHigh Frequency (HF) communication has been shown to be a useful communication technique from the very beginning of World War I and it accelerated during World War 11. This is attributed to its simplicity, ability to provide near globe connectivity at low power without repeaters, moderate cost, and ease of proliferation [I]. In fact, the HF communication system utilizes the ionosphere [2][3][4] to refract the skywave signals to a distant receiver. This ionospheric channel has some disadvantages. First, it is a non-stationary channel as the HF frequency propagation is a function of the sun spot activities, solar winds, and diurnal variations of the ionization level [5]. Second, the channel produces distortion in both signal amplitude and phase. As the different ionospheric layers move up or down, independent Doppler shifts on each propagation mode are introduced. Multipath fading [6] caused by multiple refractions of the signal fiom the ionosphere with or without ground reflection causes performance degradation in the HF system. Some techniques have been developed to improve HF performance [I]. One example is Space-Diversity [7], which uses more than one antenna at distant spaces to combine the received signal. Angle-of-Arrival Diversity that takes advantage of the fact that different modes have different arrival angles at the receiver, and so, highly directional antenna for example, can be used to improve the system performance. Another method of improving HF performance is to use different frequencies to transmit and receive messages. This method is known as Frequency diversity. Using timediversity, one can add a degree of redundancy to the transmitted message through the use of different types of coding, interleaving, etc. In the military standard, MIL-STD- 1 88- 1 1 OA [8], a convolutional encoder [9][10] followed by interleaver [Ill-[14] was used to scramble and transmit the data in different bit rates. In the presence of multipath fading [ 1 51, a training sequence is transmitted in an interleaved fashion with the data symbols with a 50% duty cycle. This has the disadvantage of losing half the bandwidth. At present, the recent advances of the Digital Signal Processing (DSP) [16][17] make it possible to reduce the bit-error-rate BEY and increase the transmission bit rate [18] through the usage of adaptive equalization [ 191-[2 11 which will be the focus of this dissertation. Equalizers such as, Transversal Equalizer [ 1 61, Blind Equalizer [22], Training waveform Equalizer [23], and Minimum Mean Square Error (MMSE) [20] Adaptive Equalizer have been applied into various communication systems. This proposal work will be to initially apply some of the previous developed equalizer to the HF channel specifically. Thereafter, new adaptive channel equalization [24],[25] will be developed to compensate for transmission channel impairments due to bandwidth limitations, multipath propagation, and rayleigh fading [2 11 conditions in mobile environments. A new technique for frequency offset prediction has been developed and finally, a new approach for MIL-STD- 1 88- 1 1 0A high frequency single-tone modem employing orthogonal Walsh-PN codes has been implemented.
Ph.D.
Doctorate;
Department of Electrical and Computer Engineering
Engineering and Computer Science
Electrical Engineering and Computer Science
198 p.
xviii, 198 leaves, bound : ill., (some col.) ; 28 cm.
Opperman, B. D. L. "Reconstructing ionospheric TEC over South Africa using signals from a regional GPS network." Thesis, Rhodes University, 2008. http://hdl.handle.net/10962/d1005273.
Повний текст джерелаHong, Chang-Ki. "Efficient differential code bias and ionosphere modeling and their impact on the network-based GPS positioning." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1190083730.
Повний текст джерелаCombrink, Adriaan Zacharias Albertus. "Detection of atmospheric water vapour using the Global Positioning System / A.Z.A. Combrink." Thesis, North-West University, 2003. http://hdl.handle.net/10394/184.
Повний текст джерелаThesis (M.Sc. (Physics))--North-West University, Potchefstroom Campus, 2004.
Giday, Nigussie Mezgebe. "Optimizing MIDAS III over South Africa." Thesis, Rhodes University, 2014. http://hdl.handle.net/10962/d1011277.
Повний текст джерелаKatamzi, Zama Thobeka. "Verification of Ionospheric tomography using MIDAS over Grahamstown, South Africa." Thesis, Rhodes University, 2008. http://hdl.handle.net/10962/d1005283.
Повний текст джерелаDal, Poz William Rodrigo [UNESP]. "Investigações preliminares sobre a influência do clima espacial no posicionamento relativo com GNSS." Universidade Estadual Paulista (UNESP), 2010. http://hdl.handle.net/11449/100251.
Повний текст джерелаCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
O erro devido à ionosfera nas observáveis GNSS (Global Navigation Satellite System) é diretamente proporcional à densidade de elétrons presente na ionosfera e inversamente proporcional a frequência do sinal. Da mesma forma que no posicionamento por ponto, os resultados obtidos no posicionamento relativo são afetados pelo efeito sistemático da ionosfera, que é uma das maiores fontes de erro no posicionamento com GNSS. Mesmo considerando que parte dos erros devido à ionosfera é cancelada na dupla diferenciação, a ionosfera pode causar fortes impactos no posicionamento relativo. O problema principal neste método de posicionamento é a variação espacial na densidade de elétrons, que pode ocorrer em função de vários fatores, tais como hora local, variação sazonal, localização do usuário, ciclo solar e atividade geomagnética. Dependendo das condições do clima espacial, que é controlado pelo Sol, a atividade geomagnética pode ser alterada de forma significativa, dando origem a uma tempestade geomagnética. Nesta pesquisa foram avaliados os efeitos da ionosfera no posicionamento relativo, com observações GNSS da fase da onda portadora (L1), nas regiões ionosféricas de latitude média e alta e na região equatorial. Nas duas primeiras regiões foram analisados os efeitos da ionosfera em períodos de irregularidades, decorrentes de tempestades geomagnéticas. Na região equatorial, que engloba o Brasil, foram analisados os efeitos da ionosfera em função da variação diária e sazonal. No processamento dos dados GNSS foi utilizado o GPSeq, que processa os dados na forma recursiva e fornece os Resíduos Preditos da Dupla Diferença da Fase (RPDDF)...
The error caused by ionosphere on GNSS (Global Navigation Satellite System) is directly proportional to the density of electrons from ionosphere and inversely proportional to the frequency squared of the signal GNSS. As in the case of point positioning, results in relative positioning are affected by systematic effect from ionosphere, which is one of major error sources in the GNSS positioning. Although some errors caused by ionosphere are canceled in double difference, strong impacts may be caused by ionosphere on the relative positioning. In this positioning the main problem is the spatial variation in electron density that can occur due local time, seasonal variation, user location, solar cycle, geomagnetic activity, etc. Depending on the conditions of space weather, in which is controlled by the Sun, the geomagnetic activity can be changed inducing geomagnetic storms. In this research the effects from ionosphere has been evaluated in GNSS relative positioning using L1 carrier phase observations, at the three regions of the ionosphere: middle and high latitudes and equatorial region. In regions of middle and high latitudes have been analyzed the effects from ionosphere in irregularities periods, caused by geomagnetic storms. In the equatorial region, including Brazil, have been analyzed the effects from ionosphere according daily and seasonal variation. In the processing GNSS data has been used GPSeq software. This software processes the data in a recursive form and provides the Predicted Residual of Carrier Phase Double Difference (PRCPDD) ... (Complete abstract click electronic access below)
Dal, Poz William Rodrigo. "Investigações preliminares sobre a influência do clima espacial no posicionamento relativo com GNSS /." Presidente Prudente : [s.n.], 2010. http://hdl.handle.net/11449/100251.
Повний текст джерелаBanca: João Francisco Galera Monico
Banca: Edvaldo Simões da Fonseca Junior
Banca: Cláudia Pereira Krueger
Banca: Moisés Ferreira Costa
Resumo: O erro devido à ionosfera nas observáveis GNSS (Global Navigation Satellite System) é diretamente proporcional à densidade de elétrons presente na ionosfera e inversamente proporcional a frequência do sinal. Da mesma forma que no posicionamento por ponto, os resultados obtidos no posicionamento relativo são afetados pelo efeito sistemático da ionosfera, que é uma das maiores fontes de erro no posicionamento com GNSS. Mesmo considerando que parte dos erros devido à ionosfera é cancelada na dupla diferenciação, a ionosfera pode causar fortes impactos no posicionamento relativo. O problema principal neste método de posicionamento é a variação espacial na densidade de elétrons, que pode ocorrer em função de vários fatores, tais como hora local, variação sazonal, localização do usuário, ciclo solar e atividade geomagnética. Dependendo das condições do clima espacial, que é controlado pelo Sol, a atividade geomagnética pode ser alterada de forma significativa, dando origem a uma tempestade geomagnética. Nesta pesquisa foram avaliados os efeitos da ionosfera no posicionamento relativo, com observações GNSS da fase da onda portadora (L1), nas regiões ionosféricas de latitude média e alta e na região equatorial. Nas duas primeiras regiões foram analisados os efeitos da ionosfera em períodos de irregularidades, decorrentes de tempestades geomagnéticas. Na região equatorial, que engloba o Brasil, foram analisados os efeitos da ionosfera em função da variação diária e sazonal. No processamento dos dados GNSS foi utilizado o GPSeq, que processa os dados na forma recursiva e fornece os Resíduos Preditos da Dupla Diferença da Fase (RPDDF) ... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The error caused by ionosphere on GNSS (Global Navigation Satellite System) is directly proportional to the density of electrons from ionosphere and inversely proportional to the frequency squared of the signal GNSS. As in the case of point positioning, results in relative positioning are affected by systematic effect from ionosphere, which is one of major error sources in the GNSS positioning. Although some errors caused by ionosphere are canceled in double difference, strong impacts may be caused by ionosphere on the relative positioning. In this positioning the main problem is the spatial variation in electron density that can occur due local time, seasonal variation, user location, solar cycle, geomagnetic activity, etc. Depending on the conditions of space weather, in which is controlled by the Sun, the geomagnetic activity can be changed inducing geomagnetic storms. In this research the effects from ionosphere has been evaluated in GNSS relative positioning using L1 carrier phase observations, at the three regions of the ionosphere: middle and high latitudes and equatorial region. In regions of middle and high latitudes have been analyzed the effects from ionosphere in irregularities periods, caused by geomagnetic storms. In the equatorial region, including Brazil, have been analyzed the effects from ionosphere according daily and seasonal variation. In the processing GNSS data has been used GPSeq software. This software processes the data in a recursive form and provides the Predicted Residual of Carrier Phase Double Difference (PRCPDD) ... (Complete abstract click electronic access below)
Doutor
Enander, Filip. "Feasibility study of data transmission via HF link from a small UAV platform." Thesis, Uppsala universitet, Signaler och System, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-323777.
Повний текст джерелаPraveen, Vikram. "Event Driven GPS Data Collection System for Studying Ionospheric Scintillation." Miami University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=miami1323894410.
Повний текст джерелаWei, Xing. "Optimization of Strongly Nonlinear Dynamical Systems Using a Modified Genetic Algorithm With Micro-Movement (MGAM)." DigitalCommons@USU, 2009. https://digitalcommons.usu.edu/etd/450.
Повний текст джерелаTeixeira, Filho Carlos Augusto. "Analysis of the effects of ionospheric sampling of reflection points near-path for high-frequency single-site-location direction finding systems." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA245950.
Повний текст джерелаThesis Advisor(s): Adler, Richard W. Second Reader: Jauregui, Stephen. "December 1990." Description based on title screen as viewed on March 30, 2010. DTIC Descriptor(s): Ionosphere, Parameters, Electron Density, Ionospheric Disturbances, Theses, Estimates, Sampling, Value, Measurement, Paths. DTIC Identifier(s): Ionospheric Disturbances, Radio Direction Finders, Atmospheric Refraction, Theses. Author(s) subject terms: Single-Site-Location, Direction-Finding, High-Frequency, Estimation, Sampling. Includes bibliographical references (p. 57-58). Also available in print.
Knight, Mark Frederick. "Ionospheric scintillation effects on global positioning system receivers." Title page, contents and abstract only, 2000. http://web4.library.adelaide.edu.au/theses/09PH/09phk698.pdf.
Повний текст джерелаPark, Jihye. "IONOSPHERIC MONITORING BY THE GLOBAL NAVIGATION SATELLITE SYSTEM (GNSS)." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1339715308.
Повний текст джерелаBoryczko, 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.
Повний текст джерелаLunt, Nicholas. "The use of the global positioning system for ionospheric studies." Thesis, Aberystwyth University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415006.
Повний текст джерелаAtilaw, Tsige Yared. "Characterization of the Multipath Environment of Ionospheric Scintillation Receivers." Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/16475.
Повний текст джерелаGlobal Navigation Satellite Systems (GNSS) are used to provide information on position, time and velocity all over the world at any time of the day. Currently there are four operational GNSS and one of them is GPS (Global Positioning System) that is developed and maintained by U.S Department of Defence (DoD), which is widely used and accessible all over the world. The accuracy of the output or even the availability of the navigation system depends on current space weather conditions, which can cause random fluctuations of the phase and amplitude of the received signal, called scintillation. Interference of GNSS signals that are reflected and refracted from stationary objects on the ground, with signals that travel along a direct path via the ionosphere to the antenna, cause errors in the measured amplitude and phase. These errors are known as multipath errors and can lead to cycle slip and loss of lock on the satellite or degradation in the accuracy of position determination. High elevation cut off angles used for filtering GNSS signals, usually 15-30°, can reduce non-ionospheric interference due to multipath signals coming from the horizon. Since a fixed-elevation threshold does not take into consideration the surrounding physical environment of each GPS station, it can result in a significant loss of valuable data. Alternatively, if the fixed-elevation threshold is not high enough we run the risk of including multipath data in the analysis. In this project we characterized the multipath environment of the GPS Ionospheric Scintillation and TEC (Total Electron Content) Monitor (GISTM) receivers installed by SANSA (South African National Space Agency) at Gough Island (40:34oS and 9:88° W), Marion Island (46:87° S and 37:86° E), Hermanus (34:42° S and19:22° E) and SANAE IV (71:73° S and 2:2° W) by plotting azimuth-elevation maps of scintillation indices averaged over one year. The azimuth-elevation maps were used to identify objects that regularly scatter signals and cause high scintillation resulting from multipath effects. After identifying the multipath area from the azimuth-elevation map, an azimuth-dependent elevation threshold was developed using the MATLAB curve fitting tool. Using this method we are able to reduce the multi-path errors without losing important data. Using the azimuth-dependent elevation threshold typically gives 5 to 28% more useful data than using a 20° fixed-elevation threshold.
Aragón, Àngel Angela. "Contributions to ionospheric electron density retrieval." Doctoral thesis, Universitat Politècnica de Catalunya, 2010. http://hdl.handle.net/10803/77897.
Повний текст джерелаLa transformada d’Abel és una tècnica emprada freqüentment en radio ocultacions (RO) que, en el context ionosfèric, permet deduir densitats electròniques a partir de dades de STEC (Slant Total Electron Content) derivats a partir d’observacions de la fase portadora. Aquesta tècnica està basada en mesures precises en doble freqüència de fase portadora (banda L) d’un receptor GPS a bord d’un satèl·lit d’òrbita baixa (Low Earth Orbit-LEO-) rastrejant un satèl·lit GPS darrere del limb de la terra. En combinar les dites mesures amb la informació de posicions i velocitats dels satèl·lits GPS i LEO, és possible deduir el canvi en el camí del senyal degut a la presència de l’atmosfera i, conseqüentment, convertir-lo en angles de curvatura (bending angles). A partir d’ells, informació sobre l’índex de refracció vertical pot ser obtinguda mitjançant tècniques d’inversió i transformar-lo en perfils verticals de densitat electrònica i/o perfils d’atmosfera neutra. Una de les hipòtesis bàsiques de la inversió clàssica és suposar que el camp de densitats electròniques té simetria esfèrica en el veïnatge d’una ocultació. Tanmateix, a la pràctica, la petjada d’una ocultació generalment cobreix regions de milers de quilòmetres que pot presentar variabilitat ionosfèrica important; per la qual cosa, la hipòtesi de simetria esfèrica no pot ser garantida. De fet, les inhomogeneitats de la densitat electrònica en la direcció vertical per a una ocultació donada són una de les principals causes d’error quan es fa servir la inversió d’Abel. Per a corregir l’error a causa de la hipòtesi de simetria esfèrica, s’introdueix el concepte de separabilitat. Això implica que la densitat electrònica pot ser expressada com una combinació de dades de Vertical Total Electron Content (VTEC) derivats externament, els quals assumeixen la dependència horitzontal de la densitat, i una funció de forma, la qual alhora assumeix la dependència en altura que és comuna a totes les observacions per a una ocultació donada. Cal notar que l’espessor de capa roman constant a prop de la regió de l’ocultació a causa de la hipòtesi de separabilitat en comptes de la densitat, tal i com succeiria en el cas de fer servir simetria esfèrica. Aquesta tècnica fou aplicada amb èxit a la combinació lineal de fases de GPS L1 i L2, LI=L1-2, la qual proporciona un observable lliure de geometria que depèn només del retard ionosfèric, l’ambigüitat de fase, biases instrumentals i wind-up. Els resultats presenten una millora del 40% en RMS en comparar freqüències del pic de la capa F2 amb dades de ionosonda respecte la inversió clàssica d’Abel. No obstant, la potencial influència de la diferència de camins òptics entre L1 i L2 fou menyspreada. Aquesta tesi doctoral mostra que això no és pas un problema per a la inversió a altures ionosfèriques. Una alternativa per a la inversió de perfils que evita aquesta desavantatge és emprar la curvatura del senyal com a dada principal. La implementació de la separabilitat per a angles de curvatura no és immediata i ha estat un dels objectius d’aquesta tesi. En aquest sentit, el principi de la separabilitat ha esta aplicat als angles de curvatura de L1 en comptes de la combinació LI com en treballs anterior. A més, treballant amb angles de curvatura, la separabilitat pot ser també traslladada a l’obtenció de perfils troposfèrics. Varies aproximacions per a obtenir la contribució de les parts altes de la ionosfera han estat també estudiades, apart del fet de prescindir simplement d’aquesta contribució. S’ha fet servir un model climatològic, una extrapolació exponencial i el fet de considera les implicacions d’usar separabilitat. També s’ha proposat una manera pera obtenir funcions de mapeo (mapping functions) deduïdes a partir de perfils RO. Tanmateix, treballant només amb dades derivades únicament de RO, s’està menyspreant sistemàticament la contribució de la protonosfera al TEC. Amb la proposta inicial de funció de mapeo només tenim en compte la contribució ionosfèrica. La solució ideal per a aplicacions de dades de terra GNSS seria fer servir un model de dues capes, una per a modelar la ionosfera i una altra per la protonosfera, o alternativament, si es volgués alta resolució tomogràfica, combinar observacions RO i amb elevació positiva de LEOs amb dades de terra. S’ha provat que modelant amb dues capes, els resultats obtinguts amb l’anàlisi de dades RO han pogut estar validats. La conclusió més important és que la proporció entre la contribució ionosfèrica i protonosfèrica és el paràmetre que explica la localització de les altures efectives.
The Abel transform is a frequently used radio occultation (RO) inversion technique which, in the ionospheric context, allows retrieving electron densities as a function of height from STEC (Slant Total Electron Content) measurements derived from carrier phase observations. The GPS RO technique is based on precise carrier dual-frequency phase measurements (L-band) of a GPS receiver onboard a Low Earth Orbit satellite (LEO) tracking a rising or setting GPS satellite behind the limb of the earth. When combining such measurements with the information from the positions and velocities of GPS and LEO satellites, it is possible to derive the phase path change due to the atmosphere during an occultation event which subsequently can be converted into bending angles. From these, information about the vertical refraction index can be obtained by means of inversion techniques, which can then be converted into ionospheric vertical electron density profiles and/or neutral atmospheric profiles. One of the basic assumptions in the classical approach is to assume the spherical symmetry of the electron density field in the vicinity of an occultation. However, in practice, the footprint of an occultation generally covers wide regions of thousands of kilometres in length that may show significant ionospheric variability; therefore this hypothesis cannot be guaranteed. Indeed, inhomogeneous electron density in the horizontal direction for a given occultation is believed to be one of the main sources of error when using the Abel inversion. In order to correct the error due to the spherical symmetry assumption, the separability concept is introduced and applied. This implies that the electron density can be expressed by a combination of externally derived Vertical Total Electron Content (VTEC) data, which assumes the horizontal dependency, and a shape function, which in turn assumes the height dependency that is common to all the observations for a given occultation. Note that the slab thickness remains constant near the occultation due to the separability hypothesis instead of the density as is the case of the spherical symmetry. This technique was successfully applied to the linear combination of the GPS carrier phases L1 and L2, , LI= L1-2 which is a geometric free observable that depends only on the ionospheric delay, phase ambiguity, instrumental bias and wind-up. The result was an improvement of about 40% in RMS when comparing frequencies of the F2 layer peak with ionosonde data and the classical Abel inversion. The main advantage of such developed technique is its simple computation. Nevertheless, the potential influence of the different signal paths between L1 and L2 was neglected. Regarding this aspect, this Ph.D. dissertation shows that is not a problem for inversion at ionospheric heights. An alternative to inverting the profile, which overcomes this disadvantage, is to use the bending angle of the signal as the main input data. The implementation of separability when using the bending angle is not immediate and was, actually, one of the goals of this thesis. In this sense, the separability approach has been applied to measured L1 bending angle, instead of LI combination as reported in previous work. Additionally, this approach could also be translated to tropospheric profile retrievals. Several approaches to account for the upper ionospheric contribution have been also tackled, apart from the fact of neglecting such contribution: a climatological model, an exponential extrapolation and condisering the nature of the separability concept. it has been proposed a way to obtain mapping functions derived from RO profiles. Such mapping functions can be easily derived from usual ionospheric parameters. For the contribution of this part of the ionosphere, it has been shown that it is capable to account for the total electron content (TEC). However, by working solely with RO derived data, we are systematically neglecting the contribution of the protonosphere to the total electron content. With the initial proposed mapping function based on the analysis of effective heights derived from RO, only the ionospheric contribution is accounted for. The ideal solution for ground-based GNSS data applications would be to use a two-layer model, one to model the ionosphere and another one for the protonosphere, or alternatively, if we are looking for high tomographic resolution, to combine RO and topside LEO observations with ground data. It has been shown that by modelling in such way, the results that were obtained with RO data analysis can be validated. The most important conclusion is that the ratio between ionospheric and protonospheric contribution is the driver for the location of the effective heights.
Komjathy, Attila. "Global ionospheric total electron content mapping using the global positioning system." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq29468.pdf.
Повний текст джерелаKomjathy, A. "Global ionospheric total electron content mapping using the global positioning system." Thesis, University of New Brunswick, 1997. http://hdl.handle.net/1882/925.
Повний текст джерелаWang, Joseph Jiong. "Electrodynamic interactions between charged space systems and the ionospheric plasma environment." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/13895.
Повний текст джерелаMeggs, Robert W. "Mapping of ionospheric total electron content using global navigation satellite systems." Thesis, University of Bath, 2005. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.410922.
Повний текст джерелаBuyukpapuscu, Suleyman Olcay. "System Identification With Particular Interest On The High Frequency Radar Under Ionospheric Disturbances." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608166/index.pdf.
Повний текст джерелаPaulson, Malin. "Testing and qualification of the boom system on the Spinning QUad Ionospheric Deployer." Thesis, KTH, Rymd- och plasmafysik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-53612.
Повний текст джерелаBeach, Theodore L. "Ionospheric propagation delay errors for space-based users of the global positioning system." Ohio University / OhioLINK, 1988. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1182779533.
Повний текст джерелаTyalimpi, Vumile Mike. "Properties of traveling ionospheric disturbances (TIDs) over the Western Cape, South Africa." Thesis, Rhodes University, 2015. http://hdl.handle.net/10962/d1017901.
Повний текст джерелаKASSABIAN, NAZELIE. "Design of pilot channel tracking loop Systems for high sensitivity Galileo receivers." Doctoral thesis, Politecnico di Torino, 2014. http://hdl.handle.net/11583/2546138.
Повний текст джерелаKasturi, Prajwal M. "Determination of Ionospheric Current Systems by Measuring the Phase Shift on Amateur Satellite Frequencies." DigitalCommons@USU, 2013. http://digitalcommons.usu.edu/etd/1521.
Повний текст джерелаBougioukos, Georgios Theodoros Adler Richard William. "The design and evaluation transmit and receive antennas for an ionospheric communications probe system : B, Sloping-vee beams." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School; Available from the National Technical Information Service, 1992. http://handle.dtic.mil/100.2/ADA261866.
Повний текст джерелаBougioukos, Georgios Theodoros. "The design and evaluation transmit and receive antennas for an ionospheric communications probe system : B, Sloping-vee beams." Thesis, Monterey, California. Naval Postgraduate School, 1992. http://hdl.handle.net/10945/38502.
Повний текст джерелаPaparini, Claudia. "Improvement of ionospheric corrections applied to the European Geostationary Navigation Overlay System (EGNOS) for applications to terrestrial positioning." Doctoral thesis, Università degli studi di Trieste, 2014. http://hdl.handle.net/10077/10122.
Повний текст джерелаL’attività di Ricerca svolta durante il ‘Corso di Dottorato in Ingegneria Civile e Ambientale ha riguardato l’attività in collaborazione con il Prof. Radicella presso il Telecommunications/ICT for Development Laboratory (T/ICT4D), the Abdus Salam International Centre of Theoretical Physics, Miramare, e il periodo formativo di tre mesi all’estero presso l’EGNOS Project Office (EPO), sede dell’European Space Agency (ESA) a Toulouse (Francia), sotto la supervisione di Dott. Stefan Schlueter dell’ EPO. Il lavoro svolto, che consiste nello studio dell’effetto della ionosfera sul segnale satellitare di EGNOS (European Geostationary Navigation Overlay System e del conseguente degrado del calcolo della posizione plano altimetrica che ne deriva, si intende come un contributo per l’ottimizzazione di uno dei servizi forniti da EGNOS denominato EGNOS Open Service, ovvero del primo servizio reso disponibile agli utenti a partire dal 2009. Le caratteristiche del servizio EGNOS Open Service sono presentate in un documento ufficiale chiamato EGNOS SDD-OS dell’Agenzia Spaziale Europea. Il suo obiettivo principale è di aumentare l’accuratezza nel posizionamento correggendo i differenti errori che influenzano il segnale GPS a singola frequenza: gli errori di orologio e di orbita dei satelliti e gli errori legati al ritardo di propagazione del segnale in ionosfera. Altre tipologie di errori, come quelli legati alla propagazione del segnale in troposfera e gli errori da multipath, essendo dovuti a effetti locali non possono essere corrette dai sistemi SBASs (Satellite Based Augmentation System). Lo scopo del documento è di suggerire le tecniche e linee guida per i produttori di ricevitori satellitari e di mettere in evidenza l’importanza del posizionamento e delle prestazioni temporali attualmente disponibili per utenti equipaggiati con strumentazione in grado di ricevere sia il segnale di trasmissione GPS in modalità Standard Positioning Service, con utilizzo della sola frequenza L1, sia il segnale fornito da EGNOS. L’importanza di questo lavoro risiede nel fatto che l’EGNOS OS, essendo un Open Service, può facilmente essere usato da differenti utenze, in una vasta gamma di settori quali la navigazione stradale, l’agricoltura di precisione e le applicazioni personali su palmari. Il lavoro svolto quest’anno s’inserisce pertanto in uno degli obiettivi proposti dall’EGNOS SDD OS. L’aspetto fondamentale riguarda i dati ionosferici forniti da EGNOS tramite i messaggi navigazionali MT 18 e MT26. E’ ormai noto come la precisione nel calcolo del posizionamento, che si ottiene mediante un sistema GNSS a singola frequenza, sia dipendente da vari fattori tra i quali quello dominante è legato alla propagazione del segnale in ionosfera. Sebbene i sistemi SBAS, (del quale EGNOS è la componente Europea) abbiano consentito di ridurre notevolmente gli effetti legati a quest'ultima tipologia di errore, anch'essi soffrono di una forte riduzione di prestazioni in condizioni di grande variabilità ionosferica, come quelle legate a alle basse latitudini o alla presenza di tempeste geomagnetiche. Per questo motivo è importante valutare a livello quantitativo le prestazioni di EGNOS in termini di range delay e di posizionamento tramite un adeguato confronto dei dati trattati con software dedicati, come quelli utilizzati dalla scrivente durante i mesi trascorsi all’EPO. Il dato principale fornito da EGNOS consiste nella correzione ionosferica in punti ionosferici di griglia (IGPs). A causa della presenza di punti IGP “non monitorati” in alcune zone dell’area di copertura del sistema (ECAC, European Civil Aviation Conference), non e' possibile calcolare in modo appropriato il ritardo ionosferico nei corrispondenti punti ionosferici (IPPs) in accordo con la tecnica di interpolazione prevista nel documento ufficiale dell’EGNOS, RTCA Do 229C-D Minimal Operational Performance Standard for GPS/WAAS. Questo incide ovviamente sulle prestazioni globali del sistema EGNOS che, in condizioni nominali, presenta una disponibilità massima di punti ionosferici di griglia (IGPs) monitorati nelle zone centrali dell’area ECAC. In questo contesto, il lavoro svoltosi all’EPO si è' diviso in 3 fasi principali: 1. Sono state considerate le possibili aree di miglioramento delle prestazioni del sistema; per queste aree sono state proposte diverse soluzioni di implementazione. Ognuna di queste soluzioni è stata scelta con l’obiettivo di migliorare la disponibilità dell’EGNOS OS e allo stesso tempo di soddisfare le richieste di accuratezza specificate nel documento. 2. Una volta identificate le possibili aree di miglioramento e di studio, sono state valutate le prestazioni associate a ciascuna soluzione proposta, usando un prototipo di ricevitore GNSS. L’utilizzo di un ricevitore/software è motivato dal fatto che questo permette grande flessibilità quando si testano le differenti opzioni. 3. Infine, sulla base della valutazione delle prestazioni ottenute, sono state considerate e discusse le soluzioni in ciascuna area analizzata. Nella prima fase della ricerca è stato studiato una strategia di calcolo per ovviare alla mancanza dei dati di EGNOS ed estendere la disponibilità per i dati di griglia, in particolare nella parte sud della zona ECAC: e’ stato effettuato uno studio delle mappe globali, in particolare quelle fornite dall’International GNSS Service (IGS) e dal CODE, dell’Università di Berna, eseguendo un confronto fra i ritardi ionosferici verticali e quelli obliqui (slant). Lo scopo di questa analisi e' stato quello di determinare il ritardo ionosferico e correggerne l'influenza in un settore critico dell'area ECAC, come quello delle regioni meridionali, a causa dell'assenza dei dati di correzione ionosferica EGNOS. L’obiettivo principale di questa fase è stato quello di confrontare il TEC verticale estratto dai dati EGNOS con quello ottenuto utilizzando le mappe globali di CODE in tutta la zona d’interesse, e infine l'utilizzo dei valori di correzione dei punti di griglia del CODE in sostituzione dei valori mancanti nei punti di griglia non monitorati da EGNOS. L’analisi è stata eseguita per gli anni 2012 e 2013 in giorni caratterizzati sia da condizioni di quiete che da condizioni di tempeste geomagnetiche, in un’area di copertura [40°W, 40°E ] in longitudine e [20°N, 60°N] in latitudine, in modo da valutare quantitativamente in che misura le mappe globali riproducano le condizioni regionali descritte dalla griglia di EGNOS in termini di gradiente spaziale di TEC (sia in longitudine che latitudine). Nella seconda fase della ricerca sono stati calcolati i valori di TEC verticale e obliquo e le coordinate dei punti IPP. In seguito sono stati calcolati i diversi contributi agli IPP ( in termini di TEC) con l’algoritmo di interpolazione bilineare a quattro punti. Sono stati considerati i valori del TEC negli IGPs: - di EGNOS - di CODE - di una griglia sintetica ottenuta sostituendo i dati di CODE nei punti di griglia non monitorati da EGNOS. Utilizzando le diverse correzioni ionosferiche sono stati ricalcolati i valori dei relativi pseudoranges da utilizzare per il calcolo della posizione con correzione WADGPS. I nuovi valori pseudorange così calcolati sono stati inseriti all'interno dei files rinex di diverse stazioni di riferimento, operanti nella parte sud dell’area ECAC. Con l'utilizzo di diversi software utilizzati all’EGNOS Project Office, sono stati valutati gli errori di posizionamento per i diversi modelli di TEC assunti al fine di valutare l’attendibilità delle precisioni planimetriche e altimetriche ottenute. Si è' deciso di usare software di posizionamento flessibili per le varie esigenze che simulassero i ricevitori, in modo da poter applicare le varie correzioni in modo sistematico. Lo scopo dell'attivita' di ricerca svolta, è quello di permettere l’estensione della disponibilità dei dati EGNOS nei valori di griglia in caso di condizioni “non monitorate” del sistema, attraverso lo studio degli effetti dell’impatto ionosferico su EGNOS.
XXV Ciclo
1984
Locubiche-Serra, Sergi. "Robust Carrier Tracking Techniques for GNSS Receivers affected by Ionospheric Scintillation." Doctoral thesis, Universitat Autònoma de Barcelona, 2019. http://hdl.handle.net/10803/668304.
Повний текст джерелаGlobal Navigation Satellite Systems (GNSS) have become an indispensable tool in different areas in our modern society for positioning purposes using radio-frequency ranging signals. Some application examples are the positioning and navigation in ground, maritime and aviation environments, as well as their use in agriculture, surveying and precise timing and synchronization in communication systems and finances. The tracking stage is one of the core tasks within a GNSS receiver to keep aligned with the satellites and, to date, most receivers equip conventional tracking techniques with ease of implementation that suffice to operate in environments with favorable working conditions. However, in the recent years, the success of GNSS in open-sky environments has led to the emergence of applications that expand toward scenarios with harsher conditions, such as urban canyons and soft-indoor environments. The trend is to provide user mobile terminals such as smartphones with positioning capabilities in scenarios where receivers face new technological challenges owing to the abounding propagation impairments. In this sense, the so-called ionospheric scintillation is one of the issues degrading the performance of GNSS receivers, particularly in equatorial regions and at high latitudes. It introduces rapid carrier phase and signal power variations, and has a detrimental effect particularly onto the tracking stage. The objective of this thesis is to design and develop new techniques for the robust tracking of GNSS signals affected by ionospheric scintillation disturbances. The presented approach is based on the use of Kalman filtering techniques, and the main contributions of the thesis are three. First, the analysis of ionospheric scintillation and the tracking of carrier dynamics despite the presence of the former. We design a Kalman filter with a hybrid formulation that allows the robust monitoring of both contributions separately. This arises from carrying out a detailed analysis of ionospheric scintillation which concludes that scintillation phase variations can be characterized through autoregressive processes, and thus be dealt with within the Kalman filter in a natural manner. Second, the design of adaptive Kalman filter-based techniques that allow self-adjusting their loop bandwidth to the actual scintillation conditions, which are rather time-varying in practice. This part includes a scintillation detector, a real-time estimator of the autoregressive model parameters, and an implementation to address the problem of non-linear signal amplitude attenuation introduced by scintillation itself. The goodness of the proposed techniques is later validated by carrying out an extensive simulation campaign using both synthetic data and real scintillation time series, and the outperformance region with respect to conventional tracking techniques is quantified. Third, a novel method for the derivation of expressions for the termed Bayesian Cramér-Rao bound (BCRB), which allow characterizing the behavior of Kalman filters in a closed-form manner, thus becoming a contribution to the literature of practical usefulness to design Kalman filters for any kind of application.
Perros, Sotirios Georgios. "The design and evaluation of transmit and receive antennas for an ionospheric communications probe system: A. Multiband Dipole Antenna." Thesis, Monterey, California. Naval Postgraduate School, 1992. http://hdl.handle.net/10945/23621.
Повний текст джерелаThis thesis reports the design, performance evaluation and construction of a transmitting antenna for an HF communications probe system. A short range ionospheric communication link between Monterey, CA, (transmit site) and San Diego, CA, (receive site) was established to test the software and hardware of this probe system. The Multiband Dipole Antenna was selected as the more practical antenna for this link, using less real estate and support structure than other alternatives. The antenna was constructed and installed at the NPS beach site where the ground constants were measured accurately. Numerical Electromagnetics Code (NEC) analysis and measurements show that the antenna operates with low input VSWR ( < 1.5), is insensitive to electrical ground characteristics and has excellent radiation patterns for short range ionospheric communication links. Based on the observed signal strengths at San Diego, the antenna appears to be performing very well.
Van, de Heyde Valentino Patrick. "An Investigation of magnetic storm effects on total electron content over South Africa for selected periods in solar cycles 23 and 24." Thesis, University of the Western Cape, 2012. http://hdl.handle.net/11394/3997.
Повний текст джерелаThe development of regional ionospheric Total Electron Content (TEC) models has contributed to understanding the behavior of ionospheric parameters and the coupling of the ionosphere to space weather activities on both local and global scales. In the past several decades, the International Global Navigation Satellite Systems Service (GNSS) networks of dual frequency receiver data have been applied to develop global and regional models of ionospheric TEC. These models were mainly developed in the Northern Hemisphere where there are dense network of ground based GPS receivers for regional data coverage. Such efforts have been historically rare over the African region, and have only recently begun. This thesis reports the investigation of the effect of mid-latitude magnetic storms on TEC over South Africa for portions of Solar Cycles 23 and 24. The MAGIC package was used to estimate TEC over South Africa during Post Solar Maximum, Solar Minimum, and Post Solar Minimum periods. It is found that TEC is largely determined by the diurnal cycle of solar forcing and subsequent relaxation, but effects due to storms can be determined
García, Rigo Alberto. "Contributions to ionospheric determination with global positioning system: solar flare detection and prediction of global maps of total electron content." Doctoral thesis, Universitat Politècnica de Catalunya, 2012. http://hdl.handle.net/10803/119769.
Повний текст джерела