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Anderson, Jason Lionel. "Autonomous Satellite Operations For CubeSat Satellites." DigitalCommons@CalPoly, 2010. https://digitalcommons.calpoly.edu/theses/256.
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In the world of educational satellites, student teams manually conduct operations daily, sending commands and collecting downlinked data. Educational satellites typically travel in a Low Earth Orbit allowing line of sight communication for approximately thirty minutes each day. This is manageable for student teams as the required manpower is minimal. The international Global Educational Network for Satellite Operations (GENSO), however, promises satellite contact upwards of sixteen hours per day by connecting earth stations all over the world through the Internet. This dramatic increase in satellite communication time is unreasonable for student teams to conduct manual operations and alternatives must be explored. This thesis first introduces a framework for developing different Artificial Intelligences to conduct autonomous satellite operations for CubeSat satellites. Three different implementations are then compared using Cal Poly's CP6 CubeSat and the University of Tokyo's XI-IV CubeSat to determine which method is most effective.
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Appleby, Graham M. "Satellite laser ranging and the ETALON Geodetic satellites." Thesis, Aston University, 1996. http://publications.aston.ac.uk/13270/.
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The technique of Satellite Laser Ranging is today a mature, important tool with applications in many area of geodynamics, geodesy and satellite dynamics. A global network of some 40 stations regularly obtains range observations with sub-cm precision to more than twelve orbiting spacecraft. At such levels of precision it is important to minimise potential sources of range bias in the observations, and part of the thesis is a study of subtle effects caused by the extended nature of the arrays of retro-reflectors on the satellites. We develop models that give a precise correction of the range measurements to the centres of mass of the geodetic satellites Lageos and Etalon, appropriate to a variety of different ranging systems, and use the Etalon values, which were not determined during pre-launch tests, in an extended orbital analysis. We have fitted continuous 2.5 year orbits to range observations of the Etalons from the global network of stations, and analysed the results by mapping the range residuals from these orbits into equivalent corrections to orbital elements over short time intervals. From these residuals we have detected and studied large un-modelled along-track accelerations associated with periods during which the satellites are undergoing eclipse by the Earth's shadow. We also find that the eccentricity residuals are significantly different for the two satellites, with Etalon-2 undergoing a year-long eccentricity anomaly similar in character to that experienced at intervals by Lageos-1. The nodal residuals show that the satellites define a very stable reference frame for Earth rotation determination, with very little drift-off during the 2.5 year period. We show that an analysis of more than about eight years of tracking data would be required to derive a significant value for 2. The reference frame defined by the station coordinates derived from the analyses shows very good agreement with that of ITRF93.
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SYED, ANEES. "COLLISON PREDICTION AND AVOIDANCE OF SATELLITES IN FORMATION." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1100034591.
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Cheng, Cheng. "GNSS Multipath and Interference Mitigation Using Bayesian Methods." Thesis, Toulouse, ISAE, 2015. http://www.theses.fr/2015ESAE0011.
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Les récepteurs GNSS sont utilisés pour estimer la position et la vitesse d’un véhicule à partir de signauxtransmis par des satellites. L’estimation est habituellement réalisée en plusieurs étapes. Lesparamètres des signaux qui concernent le délai de propagation, la phase et la fréquence Dopplerde la porteuse, sont estimés et exploités pour estimer des mesures de pseudo-distances et de delta-distances.Ces mesures sont ensuite utilisées comme observation de la position et de la vitesse parl’algorithme de navigation qui délivre l’état du véhicule. En environnement GNSS dégradé les signauxémis par les satellites GPS peuvent subir des réflexions, des réfractions, et suivre ainsi deschemins multiples, communément connus sous le nom de multi-trajets. Ces signaux induisent desdéformations du signal à différents niveaux dans les récepteurs. En particulier il en résulte une distorsiondes fonctions de corrélation et des fonctions de discrimination, ce qui conduit à des erreursdans les estimées de pseudo-distances et de delta-distances et, en conséquence, à une erreur depositionnement. Bénéficiant d’un état de l’art des approches développées pour l’atténuation deseffets des interférences, de nouvelles techniques sont proposées dans cette thèse afin de réduirel’impact des MT sur les performances des récepteurs, et d’améliorer ainsi la précision de positionnementGPSGlobal Navigation Satellite Systems (GNSS) receivers calculate the user position, velocity and timeby using the signals received from a set of navigation satellites. In constricted environments, suchas urban canyons or other intensive obstruction scenarios, the signal transmitted by the satelliteis subject to reflection or diffraction and can follow different paths, commonly known as multipath(MP) interferences, before arriving at the antenna of the GNSS receiver. The MP interferencesaffect the signal processing results at different stages in the receiver. For instance, MP signals modifythe correlation and discriminator functions and can introduce errors in pseudo-range (PR) andcarrier phase measurements, resulting finally in GNSS-based positioning errors. Therefore the MPinterference can be considered as a dominant error source in these complex situations. This thesisinvestigates MP mitigation techniques based on signal processing methods at different stages ofthe GNSS receiver. By analyzing and comparing the state-of-the-art MP mitigation approaches, innovativeMP mitigation techniques are proposed in order to reduce the impact of MP interferenceson the GNSS receiver, and to improve the positioning accuracy based on GNSS
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Morimoto, Todd A., Thomas E. Nowitzky, and Steven A. Grippando. "OPERATING A LIGHTWEIGHT, EXPENSIVE LOW EARTH ORBITING SATELLITE." International Foundation for Telemetering, 1994. http://hdl.handle.net/10150/608842.
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International Telemetering Conference Proceedings / October 17-20, 1994 / Town & Country Hotel and Conference Center, San Diego, CaliforniaAn increasing number of satellite users and manufacturers are looking to lightweight, inexpensive satellites as substitutes to traditional large, expensive satellites with multiple payloads. Neither the Department of Defense nor the commercial sector can bear the financial or reputational consequences associated with massive program failures. With the low cost and weight of these new satellites, users can achieve mission success without great risk. One example of this new class of inexpensive spacecraft is the RADCAL (RADar CALibration) satellite. Detachment 2, Space & Missile Systems Center at Sunnyvale, CA operates the satellite. RADCAL is a 200-pound polar orbiting satellite with an average altitude of 450 miles. It is primarily used by 77 worldwide radars to calibrate their systems to within five meter accuracy. Also flying on board RADCAL is a communication payload for remote field users with small radios. The RADCAL program has satisfied all mission requirements. However, with the limited size and cost come certain challenges, both in the satellite and on the ground. Pre-launch testing was not as comprehensive as with more expensive programs; anomalies have arisen that require extensive workarounds. Data management is not a straightforward task, and it is sometimes difficult and inexact to track satellite performance. These challenges are presented with their solutions in the following discussion; this paper addresses the functional, operational, and testing aspects associated with the RADCAL satellite.
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Pelletier, Claude. "Méthodologie de détection des feux de forêt à partir d'images satellitaires NOAA /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2001. http://theses.uqac.ca.
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Hutzell, William T. "The variations in the geometric albedo of Titan." Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/28054.
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Paffett, John. "VHF band interference measurement, analysis and avoidance." Thesis, University of Surrey, 2000. http://epubs.surrey.ac.uk/2105/.
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Rohozen, Amy N. "Stars and Satellites." Kent State University Honors College / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ksuhonors1462107958.
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Bazard, Jean-Pierre. "Le régime juridique de la télévision par satellites." Poitiers, 1998. http://www.theses.fr/1998POIT3010.
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Les emissions de television relayees par satellites posent le probleme juridique de la liberte d'information et de la souverainete des etats. Toutes les reglementations internationales (et nationales) interdisant ou limitant la libre reception directe des emissions de television par satellites se sont revelees inefficaces. On constate, ainsi, un mouvement mondial propice a la liberte de receptiondirecte appuye par le droit europeen qui met en echec les regles des institutions internationales. La revendication de la souverainete etatique reste symbolique. La television satellitaire est favorable aux etats s'ils savent l'utiliser et s'y adapter. Les preoccupations economiques ont mis en arriere plan la question de l'interdiction de la reception directe. Cependant, il faut souligner que la liberte de reception est violee des qu'il y a cablodistribution des emissions de television satellitaire. Un nouvel ordre juridique de la television par satellites s'elabore. Il se construit grace a de nouvelles actrices comme les organisations europeennes et mondiale du commerce. Les etats doivent s'interroger sur la commercialisation mondiale des services audiovisuels qui permettrait, malgre sesinconvenients, une plus grande liberte de reception. Egalement, les acteurs prives, tels que certains exploitants de satellites, font pression pour exiger une libre reception totale. En revanche, le role des organisations internationales initiales s'estompe quelque peu. Le nouvel ordre juridique se caracterise par un droit conventionnel au plan technique et par la naissance d'une coutume internationale quant a la liberte de diffusion et de reception des emissions. Il faut rechercher l'equilibre audiovisuel entre les etats ou que ces derniers considerent que la diffusion globale des emissions de television par satellites tend vers un equilibrage satisfaisant. Alors, les etats ont tendance a accepter plus volontiers la reception directe. Les problemes juridiques poses par la television satellitaire apparaissent bien minimes compares a ceux que creeront les autoroutes de l'information.
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Hayes, Christopher. "Analyzing the performance of new TCP extensions over satellite links." Ohio : Ohio University, 1997. http://www.ohiolink.edu/etd/view.cgi?ohiou1177439390.
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Ruiz-de-Azua, Ortega Joan Adrià. "Contribution to the development of autonomous satellite communications networks : the internet of satellites." Doctoral thesis, Universitat Politècnica de Catalunya, 2020. http://hdl.handle.net/10803/671780.
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The space is experiencing a revolution due to the em ergence of satellite services to satisfy environmental, socio-econom ic, and geo-political demands. Earth Observation satellite systems have become dependable resources for climate monitoring,
modern agriculture, and other applications. The 5G incursion in the aerospace domain has promoted the satellites as promising platforms to achieve global coverage, and cope the limitations of ground facilities. These demands can be
summarized in two system requirements: (1) increase of data transfer capacity, and (2) decrease of end-to-end
com m unications latency. Distributed Satellite Systems have emerged as an effective solution of m ultiple satellites operating simultaneouslyto satisfycommon requirements. Federated Satellite Systems are serious candidates to exploit the potential of distributed architectures by establishing opportunistic collaborations among satellites to share unallocated resources. These collaborations, called federations, allows to conceive the space as a cloud in which satellites leverage from other resources to improve their performance. The successive investigations have been centered on developing novel federation technologies. However, multiple design aspects are still open fields of study, such as the development of communications capabilities to establish these federations. This dissertation contributes to fill this gap bydefining mechanisms to deploy a network infrastructure for this purpose. A networked environment in which satellites are able to establish sporadically, and opportunisticallyfederations has been discussed. This context is called the Internet of Satellites paradigm, and prometes the temporal deployment of inter-satellite networks, composed of heterogeneous satellites. This feature---with satellite motion--poses a challenge on the definition of end-to-end communications routes composed of intermediate satellites. Areview of current routing protocols from other satellite networks is conducted to identify the ideal protocol for these dynam ic networks. The outcome remarks the need to combine capabilities from different domains to achieve the desired performance. Among them, the capabilityto predict future inter-satellite links becomes crucial to mitigate the fragmentation of the network. With this prem ise in mind, this dissertation presents a predictive protocol that perform s the estimation of these inter-satellite contacts in a distributed manner. This new satellite capability may support the routing protocol by allowing the estimation of future routes as a sequence of satellite contacts over time. The research presented in this dissertation also tackles other questions that remained unanswered: How can satellites be aware of the available resources offered by other satellites? What are the necessary mechanisms to deploy a federation? A software stack with two protocols to deal with this technology gap has been developed. The Opportunistic Service Availability Dissem ination Protocol allows notifying the services that are available in a satellite, while the Federation Deploym ent Control Protocol form alizes the rules to establish and m anage a federation. The application of these protocols considerably enhancded the capabilityof the satellite system to download data, becom ing thus enablers of future satellite m issions. The achieved perform anee has motivated the developm ent of a dedicated system. 11 has been named Federated Satellite Systems Experiment payload, and includes a communications device to create inter-satellite links. This system has been verified in a stratospheric balloon campaign, and integrated in a CubeSat miss ion. This dissertation discusses the results of the campaign, which emphasize the benefits and viabilityof this implementation. We expect that the contributions of this dissertation mayencourage to keep investigating on this inter-satellite communications for satellite federations.L'espai esta experimentant! una revolució degut a l'aparició de serveis per satèl·lit que satisfan les noves demandes ambientals, socials i geo-polítiques. Els sistemes de satèl·lits per observar la Terra han esdevingut recursos essencials per el control del clima, !'agricultura moderna, i altres aplicacions. L'entrada del 5G en el sector aeroespacial ha promogut els satèl·lits com plataformes per aconseguir una cobertura global. Aquestes necessitats poden ser classificades en dos requeriments de sistema: (1) L'augment de la capacitat per transferir dades, i (2) la reducció de la latència en les comunicacions d'extrem-a-extrem. Els sistemes distribuïts de satèl·lits han esdevingut una solució efectiva amb múltiples satèl·lits essent operats simultàniament per satisfer uns requeriments comuns. Els sistemes federats de satèl·lits són candidats prometedors per explotar el potencial de les arquitectures distribuïdes mitjançant col·laboracions oportunistiques entre satèl·lits per compartir recursos. Aquestes col·laboracions, anomenades federacions, permeten concebre l'espai com un entorn on els satèl·lits poden beneficiar-se dels recursos d'altres per millorar el seu funcionament. Les investigacions s'han central en desenvolupar noves tecnologies per aquestes federacions. No obstant, molts aspectes de disseny encara són punts oberts de recerca, com ara el desenvolupament de protocols de comunicació per establir aquestes federacions. Aquesta tesina contribueix definint mecanismes que permeten desplegar una infraestructura en xarxa per establir federacions. A més a més, es discuteix sobre aquest context interconnectat on els satèl·lits poden establir esporàdicament i oportunísticament les federacions. Aquest escenari s'ha anomenat la Internet dels Satèl·lits, i promou els desplegament temporal de xarxes entre satèl·lits heterogenis. Aquesta característica, amb el moviment dels satèl·lits, suposa un repte en la definició de rutes entre extrems formades per satèl·lits intermitjos. Una revisió de protocols d'enrutament actuals d'altres xarxes de satèl·lits s'ha realitzat per identificar el protocol ideal per aquest tipus de xarxa dinàmica. El resultat remarca la necessitat de combinar capacitats de diferents dom in is per aconseguir el funcionament desitjat. Entre aquestes, la capacitat de preveure futurs enllaços entre satèl·lits esdevé crucial per mitigar la fragmentació de la xarxa. Amb aquesta premissa, aquesta tesina presenta un protocol predictiu que estima aquests contactes entre satèl·lits de forma distribuïda. Aquesta nova capacitat pot complementar el protocol d'enrutament mitjançant l'estimació de futures rutes com seqüències of contactes de satèl·lits a través del temps. La recerca presentada en aquesta tesina també respon altres preguntes que no s'havien res post encara: Com els satèl·lits poden descobrir els recursos disponibles en la xarxa? Quins són els mecanismes necessaris per establir i mantenir una federació? Una pila de protocols per cobrir aquesta necessitat tecnològica ha sigut desenvolupat. El protocol de dispersió de la disponibilitat de serveis oportunístics permet notificar els serveis disponibles en un satèl·lit, mentre que el protocol desplegament i control de federacions s'encarrega d'establir i gestionar les federacions. L'aplicació d'aquests protocols considerablement van realçar la capacita! del sistema de satèl·lit per descarregar dades, esdevenint així potenciadors de futures missions. Aquests resultats han motivat el desenvolupament d'un sistema dedica!, que inclou un dispositiu de comunicacions per crear enllaços entre satèl·lit. Aquest sistema ha estat verifica! en una campanya de globus estratosfèrics, i ha sigut integral en una missió de CubeSats. Aquesta dissertació presenta els resultats de la campanya, els quals emfasitzen els profits i viabilitat d'aquesta implementació.
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Grungxu, Lungile Leonard. "Aspect of a hardware-in-the-loop integrated test system." Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/53292.
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Thesis (MScEng)--University of Stellenbosch, 2003.ENGLISH ABSTRACT: A multiprocessor hardware-in-the-Ioop operating system was developed for the Integrated Test System (ITS) and is aimed at implementing the ITS as a space emulation vehicle. The thesis contains a study of satellite orbits, Kepler elements, geomagnetic fields and communication protocol between the processors. The system structure consists of an orbit generator, a core-operating system and is presented with a study of the satellite sensors. In implementing the orbit propagator, there was a need to pay special attention to the Halving algorithm, the Newton Raphson method and the True Solution. These algorithms were used to calculate the true anomaly angle as a function of eccentric anomaly. The communications protocol was tested and all the errors, with their solutions, have been discussed. A concept of a geomagnetic field emulator has also been included in the hardware-in-theloop operating system. The evaluation of those aspects of the system and the conclusion are presented together with recommendations.
AFRIKAANSE OPSOMMING: 'n multiprosesseerder Hardeware in die lus bedryfstelsel is ontwikkel vir 'n Geintegreerde Toets Stelsel (ITS) en poog om die ITS te implementeer as 'n ruimte emulasie stelsel. Die tesis behels die studie van sateliet wentelbane, Kepler wentelbaan elemente, geomagnetiese velde en kommunikasie protokolle tussen die prosesseerders. Die stelsel struktuur betaal uit 'n wentelbaan propageerder, 'n kern bedryfstelsel en 'n studie van satelliet instrumentasie. As 'n deel van die implementering van die wentelbaan propageerder is die halveer algoritme, Newton-Raphson algoritme en die ware oplossing as numeriese oplossings ondersoek. Die kommunikasie protokol is getoets en foute ondersoek en word bespreek. 'n konsep vir 'n Geomagnetiese veld emulasie word die hardeware in die lus stelsel ingesluit. Die stelsel word ge-ewalueer en die gevolgtrekkings en aanbevelings gemaak.
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Gremont, Boris Christian. "Fade countermeasure modelling for Ka band digital satellite links." Thesis, Coventry University, 1997. http://curve.coventry.ac.uk/open/items/d85e8a85-635c-d024-3737-d1205f235596/1.
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This thesis investigates the modelling of fade countermeasures (FCMs) for the design of geostationary Ka band digital satellite communication systems. The analysis focuses on a typical low-power low-rate very small aperture terminal application using adaptive forward error correction as a way of counteracting the high level of detected dynamic atmospheric fading. The management and performance of such systems is conditioned greatly by the ability of practical controllers at detecting the actual level of total signal attenuation. At 20 or 30 GHz, rain attenuation and tropospheric scintillation are the two major propagation effects of interest. Part of the solution relies on the consideration and integration of their random and dynamic nature in the design process. The finite response time of practical countermeasure systems is a source of performance degradation which can be minimised by the implementation of predictive control strategies. This is the focal point of this thesis. A novel on-line short-term predictor matched to the Ka band fading process is proposed. While the rain attenuation component is efficiently predicted, tropospheric scintillation is the source of the estimation error. To take this into account, a statistical model, based on an extension of the global fading model for rain and scintillation, is then developed so that long term performance of predictive countermeasures can be drawn. Two possible ways to compensate for scintillation-induced prediction errors, namely the fixed and variable detection margin approaches, are proposed, analysed and then compared. This is achieved by calculating the FCM utilisation factor, as well as the throughput and bit error rate performance of a typical Ka band system in the presence of dynamic fading within the context of predictive fade countermeasure control operations. In the last part of this thesis, the inclusion of instantaneous frequency scaling in the design of efficient FCM control schemes is investigated. This is applicable to systems using fade detection at a base frequency. In particular, a new statistical model, accounting for the impact of the stochastic temporal variations of rain drop size distribution on rain attenuation, is presented. This thesis further confirms that countermeasure systems are technologically viable. The consideration of more specific design problems does not change the overall validity of this statement. In this thesis, it is shown that a predictive FCM technique, based on readily available punctured convolutional codes, with their relatively modest coding gain, is sufficient to provide high link availability and user data throughput on a low-power low-rate in-bound VSAT link.
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Fay, Leon. "Equalizers for communications satellites." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45992.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.Includes bibliographical references (p. 57).
This thesis investigates equalization for advanced protected satellite communications systems in development at MIT Lincoln Laboratory. Equalizers facilitate high data rate communication by correcting dispersion in the transmitter and receiver signal chains. An automated calibration procedure for finding optimal equalizers was developed. Repeated testing addressed questions about noise amplification, filter complexity requirements, and narrow band performance degradation. After examining various architectures, it was determined that the FIR filter was the best equalizer structure given the nature of the channel. The basic calibration procedure was also extended for use at high RF frequencies by using a spectrum analyzer as a tuned receiver.
by Leon Fay.
M.Eng.
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Losik, Len. "A PC WORKSTATION FOR SPACECRAFT FACTORY INTEGRATION & TEST." International Foundation for Telemetering, 1997. http://hdl.handle.net/10150/609742.
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International Telemetering Conference Proceedings / October 27-30, 1997 / Riviera Hotel and Convention Center, Las Vegas, NevadaPC technology has progressed to the point that it can very effectively support commercial geostationary spacecraft design, manufacture, test, launch, ground station, and on-orbit mission control activities. Many of the manufacturers that provide VME spacecraft test hardware and software are now providing the same functions and performance for the PC. A PC workstation equipped with single and multiple Pentium processors and Windows NT software can support single and multiple uplinks/downlinks and provide client/server capabilities that perform traditional UNIX client/server operations. Such a PC workstation can provide the functionality, features, and performance necessary for commercial spacecraft board-level test, unit-level test, subsystem-level test, spacecraft bus and payload integration, and ground station monitoring and control, as well as on-orbit mission control activities.
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Amier, Zine-Eddine. "On some transportation problems involving tethered satellite systems." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66256.
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Devasthale, Abhay, Karl-Göran Karlsson, Johannes Quaas, and Hartmut Graßl. "Correcting orbital drift signal in the time series of AVHRR derived convective cloud fraction using rotated empirical orthogonal function." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-177609.
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The Advanced Very High Resolution Radiometer (AVHRR) instruments onboard the series of National Oceanic and Atmospheric Administration (NOAA) satellites offer the longest available meteorological data records from space. These satellites have drifted in orbit resulting in shifts in the local time sampling during the life span of the sensors onboard. Depending upon the amplitude of the diurnal cycle of the geophysical parameters derived, orbital drift
may cause spurious trends in their time series. We investigate
tropical deep convective clouds, which show pronounced diurnal
cycle amplitude, to estimate an upper bound of the impact of orbital drift on their time series. We carry out a rotated empirical orthogonal function analysis (REOF) and show that the REOFs are useful in delineating orbital drift signal and, more importantly, in subtracting this signal in the time series of convective cloud amount. These results will help facilitate the derivation of homogenized data series of
cloud amount from NOAA satellite sensors and ultimately
analyzing trends from them. However, we suggest detailed
comparison of various methods and rigorous testing thereof
applying final orbital drift corrections.
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Van, Daalen Corné E. "Strategies for the control of a satellite with thruster misalignment /." Link to the online version, 2006. http://hdl.handle.net/10019/281.
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Bordi, John Joseph. "The precise range and range-rate equipment (PRARE) and its application to precise orbit determination /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
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Demarest, Peter. "Strategies for the maintenance of satellite ground tracks /." Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3008311.
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Borgsmiller, Scott A. "Effects of atmospheric scintillation in K[a]-band satellite communications." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/14982.
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Alouini, Mohamed-Slim. "Impact of the atmosphere on K [subscript a]-Band satellite communication systems." Thesis, Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/15364.
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Laguë, Mark. "Une approche multi résolutions pour la cartographie des terres humides en région nordique à l'aide d'images satellitaires." [S.l. : s.n.], 2006.
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GOICOCHEA, JUAN MARTIN OTALORA. "AN ANALYTICAL METHOD TO DETERMINE THE STATISTICAL BEHAVIOR OF THE INTERFERENCE GENERATED BY SATELLITE NETWORKS THAT USE NON-GEOSTATIONARY SATELLITES: EXTENDING THE METHOD TO REPEATED-TRACK SATELLITES." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2000. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=7527@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOEste trabalho apresenta uma descrição teórica e a implementação de um método analítico para o cálculo das estatísticas das interferências produzidas por redes não- GSO em elementos de outras redes não-GSO, de redes GSO ou do Serviço Fixo Terrestre. O método é baseado na função densidade de probabilidade da posição de um satélite (satélite de referência) da rede não-GSO, a partir da qual é possível determinar a função densidade de probabilidade da interferência produzida por esta rede no elemento interferido. O método foi anteriormente desenvolvido para a análise de interferências envolvendo em satélites de trajetória não-repetitiva [2]. O objetivo deste trabalho é estender a aplicação do método para o caso de satélites de trajetória repetitiva, através de um procedimento alternativo onde a posição do satélite de referência é representada pela sua anomalia media e pela longitude do nó de ascensão. Verificou-se que este novo procedimento, desenvolvido para aplicação ao caso de satélites de trajetória repetitiva, é também aplicável ao caso de redes que utilizam satélites de trajetória não-repetitiva. Vários exemplos são apresentados para ilustrar a aplicação do procedimento desenvolvido a situações de interesse prático.
This work presents the theoretical description and implementation of an analytical method for the evaluation of the statistical behavior of the interference produced or received by elements of a non-GSO network. This method is based on the knowledge of the probability density function of the position of one of the satellites of the non-GSO constellation (reference satellite). This probability density function can be used to determine the probability density function of the interference produced (or received) by this network. This method was previously developed for the interference analysis that involve non-repeated track satellites [2]. This work has extended the method to the case of repeated track satellites by using an alternative procedure where the reference satellite position is expressed in terms of its mean anomaly and the longitude of its ascending node. It was verified that this new procedure, developed for the case of repeated track satellites is also applicable to the case of non-repeated track satellites networks. Several examples are presented to illustrate the application of the developed procedure in situations of practical interest.
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Kolar-Znika, Lorena. "Study of the organisation and the transcriptional activity of mouse major satellites." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066156/document.
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Dans les cellules de souris, l'hétérochromatine péricentromérique, caractérisée par les répétitions des satellites majeurs et une signature épigénétique spécifique, la triméthylation de l'histone H3 sur la lysine 9 (H3K9me3), est organisée en structures nucléaires particulières appelées chromocentres. Cette région est transcriptionnellement active, produisant des ARN non-codants. Pour caractériser le profil transcriptionnel des satellites majeurs, nous avons utilisé des oligonucléotides LNA séquence spécifiques, pour des expériences de northern blot. Nous avons mis en évidence un profil de transcription complexe, révélé avec les sondes conçues pour cibler les deux brins des répétitions des satellites majeurs. Ce profil est modulé en réponse au choc thermique, condition dans laquelle un court ARN transcrit par l'ARN polymérase III, est surexprimé. Cependant, des problèmes de spécificité inhérents à l'utilisation de ces sondes LNA, ne nous ont pas permis de confirmer que les transcrits détectés ont pour origine les satellites majeurs. La seconde partie de ce travail a consisté en l'étude de l'impact de la modification ciblée de H3K9me3 aux satellites majeurs par une protéine TALE fusionnée à l'histone déméthylase mJMJD2D. Nous avons montré que le signal H3K9me3 est aboli dans les cellules transfectées avec cette protéine TALE. La déméthylation provoque des changements morphologiques des chromocentres, tels que l'augmentation de la taille des foci de satellites majeurs, accompagnés par la diminution de leur nombre, suggérant la fusion de plusieurs chromocentresIn mouse cells, pericentromeric heterochromatin, characterized by major satellite repeats and a specific epigenetic signature, the trimethylation of the histone H3 at lysine 9 (H3K9me3) is organised in particular nuclear structures called chromocenters. This region is actively transcribed, producing non-coding RNA. To investigate the transcriptional profile of major satellites, we made used of the sequence specific LNA modified oligonucleotides in northern blot experiments. We have shown that a complex transcriptional pattern is revealed with the probes designed to target both strands of the major satellite repeat. This pattern is modified in response to heat shock, in which we reveal that a short, RNA polymerase III-transcribed RNA is overexpressed. However, specificity problems encountered with the use of these LNA probes inabled us to confirm with certainty the major satellite origin of the detected transcripts. The second part of this work consisted in the studying of the impact of the targeted modification of the H3K9me3 at the major satellites by a TALE protein fused to a histone demethylase, mJMJD2D. We have shown that the H3K9me3 signal is abolished in the cells transfected with this TALE protein. The demethylation triggers morphological changes of the chromocenters such as the increase of the major satellite foci size, that are accompanied by the decrease in the foci number, suggesting the merging of several chromocenters
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Salazar, Kardozo Alexandros. "A High-Level Framework for the Autonomous Refueling of Satellite Constellations." Thesis, Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14534.
Full textAbstract:
Satellite constellations are an increasingly attractive option for many commercial and military applications. They provide a robust and distributed method of accomplishing the goals of expensive monolithic satellites. Among the many challenges that satellite constellations engender (challenges in control, coordination, disposal, and other areas), refueling is of particular interest because of the many methods one can use to refuel a constellation and the lifetime implications on the satellites.
The present work presents a methodology for carrying out peer-to-peer refueling maneuvers within a constellation. Peer-to-peer (P2P) refueling can be of great value both in cases where a satellite unexpectedly consumes more fuel than it was alloted, and as part of a mixed refueling strategy that will include an outside tanker bringing fuel to the constellation. Without considering mixed-refueling, we formulate the peer-to-peer refueling problem as an assignment problem that seeks to guarantee that all satellites will have the fuel they need to be functional until the next refueling, while concurrently minimizing the cost in fuel that the refueling maneuvers entail. The assignment problem is then solved via auctions, which, by virtue of their distributed nature, can easily and effectively be implemented on a constellation without jeopardizing any robustness properties.
Taking as a given that the P2P assignment problem has been solved, and that it has produced some matching among fuel deficient and fuel sufficient satellites, we then seek to sequence those prescribed maneuvers in the most effective manner. The idea is that while a constellation can be expected to have some redundancy, enough satellites leaving their assigned orbital slots will eventually make it impossible for the constellation to function. To tackle this problem, we define a wide class of operability conditions, and present three algorithms that intelligently schedule the maneuvers. We then briefly show how combining the matching and scheduling problems yields a complete methodology for organizing P2P satellite refueling operations.
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Lainey, V. "Théorie dynamique des satellites galiléens." Phd thesis, Observatoire de Paris, 2002. http://tel.archives-ouvertes.fr/tel-00418650.
Full textAbstract:
Nous avons élaboré une nouvelle théorie dynamique des satellites galiléens ajustée aux observations. Un programme numérique a été développé afin de pouvoir simuler le mouvement des satellites. Nous avons ainsi évalué une grande quantité de perturbations généralement négligées, et ainsi grandement amélioré la modélisation du système. La solution numérique a ensuite été ajustée à plusieurs types d'observations (photographiques, CCD et phénomènes mutuels) entre les années 1891 et 2002. Un total de plus de 2000 observations a été utilisé, dont les observations des campagnes PHEMU de 1985 et 1991. Une analyse en fréquence a finalement été effectuée dans la perspective d'obtenir une représentation sous forme analytique du système. Une méthode de filtrage pour séparer les courtes périodes des longues périodes a été développée pour résoudre des difficultés techniques (longueur d'échantillonnage, longues périodes solaires).
Notre théorie a aujourd'hui une fidélité de représentation de quelques dizaines de kilomètres sur un siècle, et reste définie sur plus de 1500 ans.
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Coleman, Matthew Grant, and coleman@mso anu edu au. "Tidal Structure in Galactic Satellites." The Australian National University. Research School of Astronomy and Astrophysics, 2005. http://thesis.anu.edu.au./public/adt-ANU20050602.112738.
Full textAbstract:
The dynamical histories of three Galactic satellite systems have been investigated. These include the Fornax and Sculptor dwarf spheroidal galaxies, and the globular cluster Omega Centauri. Wide-field CCD photometry was obtained for these objects in two colours, V and I, covering a total sky area of 30 square degrees. These data were used to construct a colour-magnitude diagram for each system, which then provided a filter to select probable member stars. This technique reduced contamination from foreground stars, allowing a comprehensive examination of the poorly-known outer regions of these three Galactic satellites.¶
An initial analysis of the central region of Fornax was made using the deep photometric data provided by Stetson et al. The analysis revealed a shell-like feature located approximately 1.5 core radii southeast from the centre of the dwarf galaxy, with an integrated luminosity of M_V ~ -4. The colour-magnitude data for this shell indicate it to be dominated by stars with an age ~2 Gyr.¶
The complete analysis of Fornax utilised two colour data covering a 3.2 deg times 3.2 deg area on the sky. The colour-magnitude selection technique revealed a second shell-like feature situated 1.3 deg northwest from the Fornax centre, approximately 30' beyond the nominal tidal radius at this position angle. This feature displays an integrated luminosity of M_V ~ -7. The alignment of this second shell is parallel to the original shell, and both are situated on the minor axis. Additionally, a statistical analysis of the extra-tidal region of Fornax revealed two large, faint surface brightness structures located on the minor axis. These structures, combined with the two shells, present strong evidence for shell structure in Fornax. This is the first such structure observed in a dwarf galaxy, and implies that Fornax has experienced a merger event in the recent past.¶
The photometric survey of Sculptor was complete to the depth of the horizontal branch stars. The red horizontal branch stars were found to be significantly more concentrated than the blue horizontal branch stars. An analysis of the distribution of red giant branch-selected stars revealed no significant extra-tidal structure. To further test this result, spectra at far red wavelengths were obtained for over 700 candidate red giant stars over the 10 sq deg region using the 2dF instrument on the Anglo-Australian Telescope. Radial velocities and metallicities for these stars were measured using Ca ii triplet lines, providing additional constraints to select Sculptor members beyond the nominal tidal radius. The distribution of the 179 probable Sculptor members indicated a lack of extra-tidal stars. These results support, at most, a mild level of interaction between this system and the Galaxy. An upper mass limit for extra-tidal material was measured to be 10% of the Sculptor luminous mass.¶
The analysis of Omega Centauri was similar to that of Sculptor. V and I band photometry was obtained to search for the tidal tails proposed by a previous study. As noted by others, dust correction was found to remove these structures. Spectra covering the region 370-450 nm were obtained for approximately 4000 candidate cluster members, and radial velocities were used to distinguish members from field stars. A total of 24 probable members of Omega Cen were found in the extra-tidal regions. Hence, if Omega Cen does possess tidal tails, they comprise at most 1% of the cluster mass.
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Hardacre, S. "Control of colocated geostationary satellites." Thesis, Cranfield University, 1996. http://hdl.handle.net/1826/1806.
Full textAbstract:
Control of the inter-satellite distances within a cluster of colocated satellites located in the same GEO window is examined with regards to the close approaches between pairs of satellites. Firstly, the orbital evolution and station keeping control of a single GEO satellite is examined and a new IBM PC based software program capable of performing both these functions autonomously from initial values of the orbital position and date is detailed and validated.
Cluster design ideas are then examined in detail and the propagation software is used to generate data for a cluster of four satellites. Two test cases are examined to quantify the frequency of close approaches between individual satellite pairs, each test case using a different orbital element separation strategy but the same station keeping control scheme. The results of the study are then compared with previous research and discussions are presented on the advantages of each method. Finally, a cluster geometry correction manoeuvre, based on Hill's equations of relative motion, is presented which requires only those thrusters used by typical station keeping.
This manoeuvre is integrated into the computer software and the two test cases noted previously are again propagated and the close approach results analysed to demonstrate the reduction in the number of close approaches below 5 km.
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Kulessa, Andrew Stephen. "Our Galaxy and its satellites." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386167.
Full text
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Kingsbury, Ryan W. "Optical communications for small satellites." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/101444.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2015.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 115-124).
Small satellites, particularly CubeSats, have become popular platforms for a wide variety of scientific, commercial and military remote sensing applications. Inexpensive commercial o the shelf (COTS) hardware and relatively low launch costs make these platforms candidates for deployment in large constellations that can offer unprecedented temporal and geospatial sampling of the entire planet. However, productivity for both individual and constellations of CubeSats in low earth orbit (LEO) is limited by the capabilities of the communications subsystem. Generally, these constraints stem from limited available electrical power, low-gain antennas and the general scarcity of available radio spectrum. In this thesis, we assess the ability of free space optical communication (lasercom) to address these limitations, identify key technology developments that enable its application in small satellites, and develop a functional prototype that demonstrates predicted performance. We first establish design goals for a lasercom payload archi- tecture that offers performance improvements (joules-per-bit) over radio-frequency (RF) solutions, yet is compatible with the severe size, weight and power (SWaP) constraints common to CubeSats. The key design goal is direct LEO-to-ground downlink capability with data rates exceeding 10 Mbps, an order of magnitude better than COTS radio solutions available today, within typical CubeSat SWaP constraints on the space terminal, and with similar COTS and low-complexity constraints on the ground terminal. After defining the goals for this architecture, we identify gaps in previous implementations that limit their performance: the lack of compact, power-efficient optical transmitters and the need for pointing capability on small satellites to be as much as a factor of ten better than what is commonly achieved today. One approach is to address these shortcomings using low-cost COTS components that are compatible with CubeSat budgets and development schedules. In design trade studies we identify potential solutions for the transmitter and pointing implementation gaps. Two distinct transmitter architectures, one based on a high-power laser diode and another using an optical amplifier, are considered. Analysis shows that both configurations meet system requirements, however, the optical amplifier offers better scalability to higher data rates. To address platform pointing limitations, we dene a staged control framework incorporating a COTS optical steering mechanism that is used to manage pointing errors from the coarse stage (host satellite body-pointing). A variety of ne steering solutions are considered, and microelectromechanical systems (MEMS) tip-tilt mirrors are selected due to their advantage in size, weight and power. We experimentally validate the designs resulting from the trade studies for these key subsystems. We construct a prototype transmitter using a modified COTS fiber amplifier and a directly-modulated seed laser capable of producing a 200mW average power, pulse position modulated optical output. This prototype is used to confirm power consumption predictions, modulation rate scalability (10 Mbps to 100 Mbps), and peak transmit power (e.g., 24.6W for PPM-128). The transmitter optical output, along with a simple loopback receiver, is used to validate the sensitivity of the avalanche photodiode receiver used for the ground receiver in the flight experiment configuration. The MEMS fine steering mechanisms, which are not rated for space use, are characterized using a purpose-built test apparatus. Characterization experiments of the MEMS devices focused on ensuring repeatable behavior (+/-0:11 mrad, 3-[sigma]) over the expected operating temperature range on the spacecraft (0°C to 40°C). Finally, we provide an assessment of the work that remains to move from the prototype to flight model and into on-orbit operations. Space terminal packaging and integration needs, as well as host spacecraft interface requirements are detailed. We also describe the remaining ground station integration tasks and operational procedures. Having developed a pragmatic COTS-based lasercom architecture for CubeSats, and having addressed the need for a compact laser transmitter and optical ne steering mechanisms with both analysis and experimental validation, this thesis has set the stage for the practical use of lasercom techniques in resource-constrained CubeSats which can yield order-of-magnitude enhancements in communications link eciency relative to existing RF technologies currently in use.
by Ryan W. Kingsbury.
Ph. D.
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Yeung, Michael C. (Michael Chi-Hang). "Phase projection using three satellites." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/40538.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.Includes bibliographical references (p. 92-95).
This study seeks to investigate various techniques used in Interferometric Synthetic Aperture Radar (InSAR) during the phase unwrapping process and the noise filtering step. In particular, as intuition would follow, we establish that the advantage of using three satellites over using just two in noise reduction means that using three satellites should be the way to go in all future work. In addition, this thesis does some in-depth investigation into the effectiveness of the following phase unwrapping methods: weighted least-squares phase unwrapping, branch-cut, and MAP dynamic programming phase unwrapping. The weighted least-squares unwrapping utilizes residues, which are points of inconsistencies on the interferogram, as a guide to assign weights when doing the weighting before the actual unwrapping step. Results show that weighted least square unwrapping fares the best in terms of mean RMS height error. We also introduce the notion of 2-D and 3-D Projection in our search for a simple, elegant solution to further reduce noise during our InSAR post-processing steps. 2-D Projection is shown to be a special case of 3-D Projection, and both require the presence of at least 3 satellites. Projection in general reduces noise in the system by utilizing the information provided by the configuration of the satellites to reduce the set of allowed phase points, thereby improving the robustness of the system to noise. Our results show that, for almost all cases, whether in the extremely small baseline distance or non-integer baseline ratios, using 3-D Projection gives much better results. Results are entirely simulation based, using the engineering tool MATLAB Version 7.0 developed by Mathworks. Root-mean-square errors will be used as the metric for comparison for most cases.
by Michael C. Yeung.
S.M.
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Coleman, Matthew Grant. "Tidal structure in Galactic satellites /." View thesis entry in Australian Digital Theses, 2004. http://thesis.anu.edu.au/public/adt-ANU20050602.112738/index.html.
Full text
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Douglas, Dennis Michael. "Shadow Imaging of Geosynchronous Satellites." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/332833.
Full textAbstract:
Geosynchronous (GEO) satellites are essential for modern communication networks. If communication to a GEO satellite is lost and a malfunction occurs upon orbit insertion such as a solar panel not deploying there is no direct way to observe it from Earth. Due to the GEO orbit distance of ~36,000 km from Earth's surface, the Rayleigh criteria dictates that a 14 m telescope is required to conventionally image a satellite with spatial resolution down to 1 m using visible light. Furthermore, a telescope larger than 30 m is required under ideal conditions to obtain spatial resolution down to 0.4 m. This dissertation evaluates a method for obtaining high spatial resolution images of GEO satellites from an Earth based system by measuring the irradiance distribution on the ground resulting from the occultation of the satellite passing in front of a star. The representative size of a GEO satellite combined with the orbital distance results in the ground shadow being consistent with a Fresnel diffraction pattern when observed at visible wavelengths. A measurement of the ground shadow irradiance is used as an amplitude constraint in a Gerchberg-Saxton phase retrieval algorithm that produces a reconstruction of the satellite's 2D transmission function which is analogous to a reverse contrast image of the satellite. The advantage of shadow imaging is that a terrestrial based redundant set of linearly distributed inexpensive small telescopes, each coupled to high speed detectors, is a more effective resolved imaging system for GEO satellites than a very large telescope under ideal conditions. Modeling and simulation efforts indicate sub-meter spatial resolution can be readily achieved using collection apertures of less than 1 meter in diameter. A mathematical basis is established for the treatment of the physical phenomena involved in the shadow imaging process. This includes the source star brightness and angular extent, and the diffraction of starlight from the satellite. Atmospheric effects including signal attenuation, refraction/dispersion, and turbulence are also applied to the model. The light collection and physical measurement process using highly sensitive geiger-mode avalanche photo-diode (GM-APD) detectors is described in detail. A simulation of the end-to-end shadow imaging process is constructed and then utilized to quantify the spatial resolution limits based on source star, environmental, observational, collection, measurement, and image reconstruction parameters.
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Lainey, Valéry. "Théorie dynamique des satellites Galiléens." Observatoire de Paris (1667-....), 2002. http://www.theses.fr/2002OBSP0104.
Full textAbstract:
Nous avons élaboré une nouvelle théorie dynamique des satellites galiléens ajustée aux observations. Un programme numérique a été développé afin de pouvoir simuler le mouvement des satellites. Nous avons ainsi évalué une grande quantité de perturbations généralement négligées, et ainsi grandement amélioré la modélisation du système. La solution numérique a ensuite été ajustée à plusieurs types d’observations (photographiques, CCD et phénomènes mutuels) entre les années 1891 et 2002. Un total de plus de 2000 observations a été utilisé, dont les observations des campagnes PHEMU de 1985 et 1991. Une analyse de fréquence a finalement été effectuée dans la perspective d’obtenir une représentation sous forme analytique du mouvement des satellites. Une méthode de filtrage pour séparer les courtes périodes des longues périodes a été développée pour résoudre des difficultés techniques (longueur d’échantillonnage, longues périodes solaires). Notre théorie a aujourd’hui une fidélité de représentation de quelques dizaines de kilomètres sur un siècle, et reste définie sur plus de 1500 ansWe have developed a new dynamical theory of the Galilean system based on historical observations. A numerical code has been made for simulating the motion of the satellites where many of the usually neglected perturbations have been quantified, thus considerably improving the modeling of the system. The numerical solution has been fitted to several kind of observations (photographic, CCD and mutual phenomena) taken between 1891 and 2002. More than 2000 observations have been used, including the PHEMU campaign of 1985 and 1991. A frequency analysis was finally used as a way of obtaining a theory with an analytical form of the motion of the satellites. A digital filtering treatment for removing the short periods from the long ones has been developed, hence solving some technical problems such as the length of the sample and the long solar periods. Our theory has an accuracy of a few tens of kilometers over one century and remains valid for more than 1500 years
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Cantillo, Juan. "Codage multi-couches pour systèmes de communication par satellites." Phd thesis, Paris, ENST, 2008. https://pastel.hal.science/pastel-00005209.
Full textAbstract:
Cette thèse aborde les problèmes liés à la fiabilité des transmissions satellitaires depuis la perspective de l'optimisation multi-couches. S'agissant d'un aspect crucial des communications satellitaires ayant des implications à presque tous les niveaux de la communication, le contrôle des erreurs est sans doute l'une des thématiques satellite où les techniques multi-couche peuvent jouer un rôle important. La première partie de ce travail s'intéresse à la stratégie de contrôle des erreurs des satellites DVB de première génération, où sont identifiées des redondances liées à une gestion inefficace du problème par le décodeur canal et les couches d'adaptation. Une solution basée sur une approche multi-couche réduisant ces inefficacités est alors proposée. Ensuite, nous nous consacrons au standard satellite DVB de nouvelle génération et à la définition de GSE, sa nouvelle couche d'adaptation pour IP. Nous montrons comment GSE intègre de nombreux concepts multi-couches, parmi lesquels ceux liés à une gestion des erreurs basée sur les considérations de la première partie de ce travail. La troisième et dernière partie de ce travail présente HERACLES. Ce nouveau mécanisme multi-couches permet d'apporter des capacités accrues de correction d'erreurs et de synchronisation paquets à tout système de communications digitales sans consommation supplémentaire de bande. HERACLES a été entièrement développé dans cette thèse et a fait l'objet de deux brevets récents. Les résultats globaux de ce travail montrent les possibilités offertes par l'approche multi-couchesau problème du contrôle des erreurs, et ouvrent d'excellentes perspectives de déploiement dans les réseaux futursThis thesis addresses the error control problem for satellite links from the perspective of cross-layer design. At the crossroads of qos-related constraints, devices complexity and efficient spectrum use, error control is indeed a key aspect of wireless communications - particularly crucial in the satellite context - where cross-layer enhancements can play an important role. After a thorough introduction to cross-layer design, the first part of this work focuses specifically on the error control strategy of early DVB satellites, where redundancies between the channel decoder and the adaptation layers are set to light in order to propose a joint bandwidth-efficient error control policy. The focus then moves to second-generation DVB satellites and the definition of the novel, IP-centric and cross-layer friendly GSE encapsulation protocol, where results from the aforementioned study were successfully applied. Finally, a whole new cross-layer framework called HERACLES is introduced, offering efficient and overhead-free error correction capabilities for almost any layer of a protocol stack and being patented at the moment of writing these words. The results of the overall work show the strengths of an integrated approach to error control, and open the way for innovative cross-layer mechanisms to be deployed in next-generation communications networks
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Cantillo, Juan. "Codage multi-couches pour systèmes de communication par satellites." Phd thesis, Télécom ParisTech, 2008. http://pastel.archives-ouvertes.fr/pastel-00005209.
Full textAbstract:
Les architectures satellitaires actuelles pour distribution de services interactifs IP et la connectivité large bande sont basées sur les principes en couches du modèle de référence OSI. Il ne fait aucun doute que l'approche classique basée sur la résolution de problèmes spécifiques à chaque couche dans le cadre du modèle de référence a été très fructueuse jusqu'à aujourd'hui. De nombreux protocoles ont été adaptés aux environnements satellite, et les couches physiques actuelles opèrent près de leurs limites théoriques de performance grâce à l'état très avancé des techniques de modulation et de codage. Cependant, les caractéristiques uniques des transmissions par satellite font que de nombreux et importants problèmes tels que la transparence de la mobilité, le respect des niveaux de services négociés ou la fiabilisation à grande échelle des communications point à multipoint n'ont pas encore trouvé de solutions satisfaisantes dans le cadre de l'approche traditionnelle en couches. L'approche modulaire n'appréhende que moyennement les interactions complexes qui existent entre les couches ainsi que celles avec le médium sans fil, et de ce fait le design actuel fait apparaître des redondances et inefficacités affectant les performances globales. De nombreux chercheurs ont donc commencé à aborder ces différents problèmes de manière holistique, en mettant l'accent sur les avantages potentiels d'une collaboration entre couches au-delà du modèle de référence. La flexibilité résultant d'échanges accrus entre les différentes couches offre en effet de riches possibilités d'optimisation globales, favorisant une meilleure intégration des satellites dans un environnement réseau de plus en plus hétérogène. Cette "optimisation multi-couches" apparaît aujourd'hui comme un domaine de recherche très prometteur pour les communications satellitaires et sans fil en général. Elle se caractérise par une approche pluridisciplinaire mêlant différents aspects de la théorie de l'information, du design de protocoles réseau et du traitement du signal avancé. Force est de constater que de nombreuses techniques multi-couches récemment proposées ont commencé à traiter avec succès quelques uns des problèmes énumérés auparavant, ce qui explique que nombreux protocoles, standards et systèmes de nouvelle génération ont déjà commencé à intégrer ces principes de facto. Cette thèse aborde les problèmes liés à la fiabilité des transmissions satellitaires depuis la perspective de l'optimisation multi-couches. S'agissant d'un aspect crucial des communications satellitaires ayant des implications à presque tous les niveaux de la communication - tels que la qualité de service, la complexité des terminaux ou l'utilisation du spectre - le contrôle des erreurs est sans doute l'une des thématiques satellite où les techniques multi-couche peuvent jouer un rôle important. Après une introduction dédiée aux techniques multi couche en général, la première partie de ce travail s'intéresse à la stratégie de contrôle des erreurs des satellites DVB de première génération, où sont identifiées des redondances liées à une gestion inefficace du problème par le décodeur canal et les couches d'adaptation. Une solution basée sur une approche multi-couche réduisant ces inefficacités et améliorant l'utilisation des ressources est alors proposée. Dans un deuxième temps, nous nous consacrons au standard satellite DVB de nouvelle génération et à la définition de GSE, sa nouvelle couche d'adaptation pour IP. Nous montrons comment GSE intègre de nombreux concepts multi-couches, parmi lesquels ceux liés à une gestion des erreurs basée sur les considérations de la première partie de ce travail. La troisième et dernière partie de ce travail présente HERACLES. Ce nouveau mécanisme multi-couches permet d'apporter des capacités accrues de correction d'erreurs et de synchronisation paquets à tout système de communication par paquets sans consommation supplémentaire de bande. HERACLES a été entièrement développé dans le cadre de cette thèse et a fait l'objet de deux brevets récents. Les résultats globaux de ce travail montrent les possibilités offertes par l'approche multi-couches au problème du contrôle des erreurs, et ouvrent d'excellentes perspectives de déploiement dans les réseaux futurs.
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Stewart, Abbie Marie. "A guide to the establishment of a university satellite program." Diss., Rolla, Mo. : University of Missouri-Rolla, 2007. http://scholarsmine.umr.edu/thesis/pdf/THESISfinal_09007dcc8031d8ef.pdf.
Full textAbstract:
Thesis (M.S.)--University of Missouri--Rolla, 2007.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed May 16, 2007) Includes bibliographical references (p. 96-97).
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Maillard, Adrien. "Flexible Scheduling for Agile Earth Observing Satellites." Thesis, Toulouse, ISAE, 2015. http://www.theses.fr/2015ESAE0024/document.
Full textAbstract:
Les satellites d’observation de la Terre sont des senseurs qui acquièrent des données, les compressent et les mémorisent à bord, puis les vident vers le sol. Des incertitudes rendent la planification des activités au sol de plus en plus discutable car la planification est alors pessimiste et les plans largement sous-optimaux. Cette thèse détaille la conception d'une planification mixte qui permet de profiter de la réalisation des paramètres incertains à bord tout en préservant la prévisibilité de l'exécution pour les opérateurs au sol. Notre première contribution concerne le problème de planification des vidages. Un mécanisme de planification flexible a été conçu dans lequel seules les acquisitions de haute priorité sont planifiées de manière pessimiste. A bord, un algorithme adapte le plan en fonction des volumes réels, en s'assurant que le vidage des acquisitions de haute priorité est toujours garanti, et insère des nouveaux vidages si possible. Notre deuxième contribution concerne le problème de planification des acquisitions. Au sol, des contraintes contribuent à éliminer du plan de nombreuses acquisitions qui auraient pu être réalisées car les niveaux de ressources à bord sont souvent plus hauts que ceux prévus par ces contraintes. Dans un nouveau mécanisme de décision, le sol produit des plans conditionnels dans lesquels la réalisation des acquisitions de basse priorité est conditionnée par des niveaux d'énergie requis. Comparées à d'autres mécanismes de planification, ces deux approches flexibles permettent d'éviter le gaspillage des ressources et de réaliser plus d'acquisitions et de vidages tout en conservant de la prévisibilitéEarth-observation satellites are space sensors which acquire data, compress and record it on board, and then download it to the ground. Some uncertainties make planning and scheduling satellite activities offline on the ground more and more arguable as worst-case assumptions are made about uncertain parameters and plans are suboptimal. This dissertation details our efforts at designing a flexible decision-making scheme that allows to profit from the realization of uncertain parameters on board while keeping a fair level of predictability on the ground. Our first contribution concerns the data download problem. A flexible decision-making mechanism has been designed where only high-priority acquisition downloads are scheduled with worst-case assumptions. Other acquisition downloads are scheduled with expected parameters and conditioned by resource availability. The plan is then adapted on board. Our second contribution concerns the acquisition planning problem. A lot of acquisitions that could have been done are eliminated when planning because of worst-case assumptions. In a new decision-making scheme, these high-level constraints are removed for low-priority acquisitions. Observation plans produced on the ground are conditional plans involving conditions for triggering low-priority acquisitions. Compared with pure ground and pure onboard methods, these two approaches avoid wastage of resource and allow more acquisitions to be executed and downloaded to the ground while keeping a fair level of predictability on the ground
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Ronnet, Thomas. "Origin and formation of the regular satellites around planets." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0331/document.
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Les travaux réalisés au cours de cette thèse s'intéressent à l'origine et à la formation des satellites naturels réguliers de Mars et Jupiter qui sont les cibles de futures missions d'exploration spatiale dédiées à leur caractérisation. Le cas controversé de l'origine de Phobos et Deimos, les lunes de Mars, est adressé et il est montré que leur formation à la suite d'un impact géant permettrait de réconcilier leurs propriétés orbitales et physiques. Concernant les satellites galiléens orbitant Jupiter, il est montré que dans le contexte classiquement utilisé de leur formation, la croissance des lunes a certainement procédé par l'accrétion de grains de poussières, un processus appelé "pebble accretion", plutôt que par celle de corps plus grands comme il est typiquement considéré. Des propriétés intéressantes, ainsi que d'autres plus problématiques, de la croissance des lunes galiléennes par "pebble accretion" sont dérivées. Dans un second temps, le transport de solides nécessaires à l'assemblage des lunes galiléennes dans le disque circum-jovien est étudié dans le contexte des récentes théories de formation des planètes géantes. Nous montrons que la vision classique selon laquelle le gaz accrété par Jupiter transporte assez de solides pour former ses lunes est probablement erronée. Il est proposé que, aidée par la formation de Saturne, Jupiter a pu capturer dans son disque assez de planétésimaux pour assembler les satellites galiléens. Contrairement aux précédents scénarios, le cadre proposé prédit que des analogues aux satellites galiléens ne se forment pas autour de toutes les planètes géantesThis thesis aims at better understanding the origin and formation of the martian moons, Phobos and Deimos, and the major jovian satellites known as the galilean moons, each of these systems being the target of future space exploration missions dedicated to their characterization. We address the puzzling origin of Phobos and Deimos and show that their formation following a giant impact could allow to account for both their orbital and physical properties. As regards the galilean moons, we argue that their growth would likely proceed through the accretion of small dust grains, a process known as pebble accretion, rather than through the accretion of larger satellitesimals within the typical framework assumed for their formation. We derive some interesting properties as well as some drawbacks of pebble accretion in the galilean system. Then, the delivery of solid material from the protoplanetary disk to the circum-jovian disk is investigated in light of recent developments of the theory of giant planets' formation. It is shown that the classic view that the gas accreted by Jupiter transports enough solids to build many galilean-like satellites is likely to be erroneous and some other mechanism must have taken place to account for the presence of the massive galilean moons. It is proposed that, with the help of Saturn's formation, Jupiter could have captured within its disk enough planetesimals on initially heliocentric orbits to build the galilean moons. Unlike previous scenarios, the proposed framework predicts that the presence of galilean analogues would not be ubiquitous around extrasolar giant planets
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Noyelles, Benoît. "Effets des marées sur la dynamique des satellites de Jupiter et de Saturne." Observatoire de Paris (1667-....), 2005. https://theses.hal.science/tel-01958562.
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Les effets de marée induisent une accélération séculaire des satellites planétaires. Dans le cas des satellites de Jupiter et de Saturne, de telles accélérations n'ont pas encore été détectées avec une fiabilité suffisante, mais tant les progrès de la modélisation dynamique que l'amélioration des observations astrométriques laissent espérer une détection prochaine pour J-1 Io et S-3 Téthys. Ce travail aborde les deux thèmes. L'objectif principal est de mieux modéliser les mouvements et mieux comprendre les résonances. Cette thèse apporte ainsi une contribution à l'étude de l'histoire dynamique du système des satellites Galiléens en examinant les conséquences de l'inégalité de De Haerdtl 7:3 entre Ganymède et Callisto. Il est démontré que cette inégalité est responsable d'une couche chaotique, traversée récemment par le système. Cette couche chaotique, causée par plusieurs recouvrements de résonances, est mise en évidence par la technique de l'analyse en fréquences, et les arguments responsables du chaos par diffusion de Chirikov sont clairement identifiés. Ainsi, il apparaît que l'inégalité de De Haerdtl doit maintenant être prise en compte dans l'étude de la formation de la résonance laplacienne. Par ailleurs ce travail, en tant que première approche de la signature observationnelle des effets de marée, rend également compte des réductions d'observations de phénomènes mutuels de satellites de Saturne réalisées en 1995 ainsi que des observations et réductions de phénomènes de satellites de Jupiter que nous avons réalisées en 2003. Ces réductions contribuent également à l'amélioration des modèlesTidal effects induce a secular acceleration of planetary satellites. Such accelerations have not been detected yet with enough reliability for Jovian and Saturnian satellites, but we can hope a close detection for J-1 Io and S-3 Thetys thanks to the progress of dynamical modelisation and the improvement of astrometric observations. This work deals with the two topics. The main purpose is to improve the modelisation of motions and our understanding of resonances. This thesis also contributes to the study of the dynamical history of the Galilean satellites while studying the consequences of De Haerdtl’s inequality 7:3 between Ganymede and Callisto. It is shown that this inequality induces a stochastic layer recently crossed by the system. Thanks to a frequency analysis, it is proved that this chaos is in fact Chirikov diffusion induced by overlaps of several resonances, which are clearly identified. This result leads to the conclusion that De Haerdtl’s inequality has to be taken into account in every study on the formation of the laplacian resonance between Io, Europa and Ganymede. Moreover this work, as a first approach of the observational signature of tidal effects, deals with reduction of mutual events which occurred in 1995 in the Saturnian system and with observation and reduction of mutual events of Galilean satellites of the last PHEMU campaign, in 2003. This reductions contribute to the improvement of ephemerides
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Kostallari, Enis. "Microcirculation et croissance musculaire : rôle des péricytes dans la niche des cellules satellites musculaires." Thesis, Paris Est, 2014. http://www.theses.fr/2014PEST0065.
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Les microvaisseaux musculaires sont souvent considérés comme une source de nutriments et d'oxygène pour le muscle en croissance et ils semblent être conservés de façon stéréotypée. L'unité microvasculaire du muscle sain et adulte est composée de 6 à 8 capillaires. Dans Gitiaux, et al. (2013) nous montrons que l'organisation et la taille de l'unité microvasculaire sont strictement similaires chez l'homme et la souris. Dans le muscle squelettique adulte, la majorité des cellules satellites sont proches des péricytes et certaines d'entre elles semblent pouvoir établir des contacts directs temporaires avec les péricytes. In vitro, les cellules endothéliales induisent l'activation et la prolifération des cellules satellites en sécrétant de l'Angpt-2 et du PDGF-BB, alors que les péricytes induisent la quiescence et la différenciation des cellules satellites, par l'Angpt-1 et l'IGF-1 respectivement. Ces effets ont été confirmés in vivo, en utilisant les modèles murin Tg:NG2Cre/+::R26RiDTR, Tg:NG2Cre/+::IGF1del/+ et Tg:TNAPCreERT2/+::Angpt1del/+, dans lesquels il existe une hypotrophie musculaire et une activation des cellules satellites. Tous ces résultats soutiennent le dogme que « des cellules souches soutiennent d'autre cellules souches »Muscle microvasculature is often considered solely as a source of nutrients and oxygen for growing muscle cells and seems to be stereotypically conserved between human and mouse. The adult normal muscle microvascular unit is formed of 6–8 capillaries. In Gitiaux, et al. (2013) we show that microvascular unit organization and size are strikingly similar in human and small animals. In the adult skeletal muscle, the majority of satellite cells are close neighbors of pericytes and some of them are probably able to establish temporary direct contacts with pericytes. During post-natal development, in human and mice, pericytes and satellite cells become progressively closer. In vitro, endothelial cells induce satellite cell activation and proliferation through Angpt-2 and PDGF-BB, while pericytes induce quiescence through Angpt-1 and differentiation of satellite cells through IGF-1. These effects are confirmed by in vivo experiments using Tg:NG2Cre/+::R26RiDTR, Tg:NG2Cre/+::IGF1del/+ and Tg:TNAPCreERT2/+::Angpt1del/+ mice, which exhibit muscle hypotrophy and satellite cell activation. All these results support the emerging concept that “stem cells support other stem cells”
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García, Berumen Armando. "Apport des techniques multi-niveaux dans une architecture de satellites géostationnaires DVB-S2/RCS." Evry, Institut national des télécommunications, 2008. http://www.theses.fr/2008TELE0025.
Full textAbstract:
On se dirige depuis plusieurs années vers l'intégration de divers services sur un seul et même réseau de télécommunications : c'est le service « triple-play ». Les satellites, par leur couverture, permettent de l'offrir dans les zones sans couverture par les réseaux terrestres. Par ailleurs, la norme DVB a évolué, on a ouvert le canal de retour (RCS) pour permettre des services interactifs, on y gère la bande passante de façon dynamique et, pour la gestion adaptative de la couche physique, des techniques dites F. M. T. (« fade modulation techniques ») ont été proposées pour maintenir un taux d'erreurs bas, tout en optimisant la bande passante en minimisant les données de F. E. C. Et en exploitant les modulations présentant les plus grands débits lorsque c'est possible. Depuis quelques années, les techniques dites multi-niveaux ont été généralisées à divers environnements, et divers types de services, elles ont été testées et utilisées dans les réseaux ad-hoc, par exemple, avec un certain succès pour transporter divers services, multimédia et TCP en particulier. Dans cette situation, il était intéressant d'évaluer l'apport des techniques multi-niveaux dans les architectures satellites DVB-S2/RCS en présence de techniques « F. M. T. ». C'est l'objet de cette thèse. Ce travail a été démarré dans le contexte d'une collaboration avec Astrium pour le CNES. Dans la première partie, nous proposons un algorithme multi-niveau pour le transport de la voix sur IP dans ces réseaux. Cet algorithme fait intervenir la couche transport et la couche MAC. L'intégration de cet algorithme dans l'architecture puis ses performances sont étudiées, et particulièrement son comportement en présence de trafic concurrent. Dans la deuxième partie, en vue du travail proposé dans la troisième, on évalue l'influence du délai de transmission sur le comportement de TFRC, et particulièrement dans la façon dont il partage la bande avec TCP. On constate que le comportement est assez variable selon la valeur du délai de transmission, et que les différences sont essentiellement dues à la différence de convergence des mécanismes de contrôle de congestion vers la pleine estimation de la bande qui leur est disponible. Dans la troisième partie, nous présentons un algorithme multi-niveau d'affectation de la bande passante pour un lien sur lequel transitent à la fois du trafic multimédia et du trafic de données. Chaque service a une bande passante garantie de manière paramétrable et l'algorithme récupère la bande inutilisée d'un autre trafic, soit qu'il n'ait pas besoin d'émettre, soit qu'il n'ait pas encore convergé vers la pleine utilisation de sa bande passante, pour la répartir au mieux entre les connexions qui saturent déjà la bande qui leur est réservéeFor past several years, we are moving towards the integration of various services on a single and common telecommunication network: known as "triple-play". The satellite systems, with the coverage characteristic, are able to offer this service in the zones which cannot be covered by the terrestrial networks. On the other hand, the DVB standards have been evolved, the return channel (RCS) was opened to allow interactive services. We have the possibility to manage the bandwidth in a dynamic way, and to manage the physical layer adaptively. Techniques known as FMT (Fade Mitigation Techniques) have been proposed to maintain low error rate and to optimize the bandwidth by minimizing the FEC data and exploiting the modulations to achieve high throughputs. For several years, the cross-layer techniques have been generalized in various environments and also in various types of services. They have been tested and used in ad-hoc networks. These techniques have reached a certain level of success to transport various services, particularly multimedia and TCP. With the evolution of DVB standards and the emergence of cross-layer approach, it is becoming more and more interesting to analyze and evaluate the contributions of these techniques in satellite architectures such as DVB-S2/RCS in the presence of FMT techniques. This is the purpose of this work. This study started with a project for the CNES in collaboration with Astrium. This thesis is organized in three main parts. In the first part, we have developed a cross-layer algorithm for transporting the voice over IP in satellite networks. The cross-layer algorithm is based on the interaction between the transport and the MAC layers. The integration of the proposed algorithm on the architecture compliant with DVB standards is carried out. To prove the efficiency of our algorithm, a performance evaluation is performed with particular attention to the behaviour in the presence of cross-traffic. In the second part, to prepare for the work proposed in the third part, we have analyzed the impact of the transmission delay over the TFRC behaviour; in particular, we have analyzed the way in which it shares bandwidth with TCP. It is inferred from the analysis that behaviour of TRFC varies according to the transmission delay. We have also found that the difference between TFRC and TCP are primarily due to its different convergence time of the congestion control mechanism towards the full occupation of the available bandwidth. In the third part, we have presented a cross-layer algorithm to allocate the bandwidth over a satellite link, which is shared at the same time by both multimedia and data traffic. In a parametric way, the mechanism assigns a guaranteed bandwidth for each connection. The algorithm is able to recover the unused bandwidth from other traffic, which either does not have anything to send or, yet not fully converged occupying the whole bandwidth. The bandwidth recovered is shared among the connections that have already saturated their reserved bandwidth
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Score, Robert H. "An examination of XM satellite subscriber's perceptions of satellite radio compared to traditional AM/FM radio." Instructions for remote access. Click here to access this electronic resource. Access available to Kutztown University faculty, staff, and students only, 2002. http://www.kutztown.edu/library/services/remote_access.asp.
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Thesis (M.S.)--Kutztown University of Pennsylvania, 2002.Source: Masters Abstracts International, Volume: 45-06, page: 2720. Typescript. Abstract precedes thesis as preliminary leaves 1-2. Includes bibliographical references (leaves 34-35).
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Carnochan, Stuart. "Orbit and altimetric corrections for the ERS satellites through analysis of single and dual satellite crossovers." Thesis, Aston University, 1996. http://publications.aston.ac.uk/14262/.
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Due to the failure of PRARE the orbital accuracy of ERS-1 is typically 10-15 cm radially as compared to 3-4cm for TOPEX/Poseidon. To gain the most from these simultaneous datasets it is necessary to improve the orbital accuracy of ERS-1 so that it is commensurate with that of TOPEX/Poseidon. For the integration of these two datasets it is also necessary to determine the altimeter and sea state biases for each of the satellites. Several models for the sea state bias of ERS-1 are considered by analysis of the ERS-1 single satellite crossovers. The model adopted consists of the sea state bias as a percentage of the significant wave height, namely 5.95%. The removal of ERS-1 orbit error and recovery of an ERS-1 - TOPEX/Poseidon relative bias are both achieved by analysis of dual crossover residuals. The gravitational field based radial orbit error is modelled by a finite Fourier expansion series with the dominant frequencies determined by analysis of the JGM-2 co-variance matrix. Periodic and secular terms to model the errors due to atmospheric density, solar radiation pressure and initial state vector mis-modelling are also solved for. Validation of the dataset unification consists of comparing the mean sea surface topographies and annual variabilities derived from both the corrected and uncorrected ERS-1 orbits with those derived from TOPEX/Poseidon. The global and regional geographically fixed/variable orbit errors are also analysed pre and post correction, and a significant reduction is noted. Finally the use of dual/single satellite crossovers and repeat pass data, for the calibration of ERS-2 with respect to ERS-1 and TOPEX/Poseidon is shown by calculating the ERS-1/2 sea state and relative biases.
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Crockett, Derick A. "Geosynchronous Earth Orbit/Low Earth Orbit Space Object Inspection and Debris Disposal: A Preliminary Analysis Using a Carrier Satellite With Deployable Small Satellites." DigitalCommons@USU, 2013. https://digitalcommons.usu.edu/etd/1749.
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Detailed observations of geosynchronous satellites from earth are very limited. To better inspect these high altitude satellites, the use of small, refuelable satellites is proposed. The small satellites are stationed on a carrier platform in an orbit near the population of geosynchronous satellites. A carrier platform equipped with deployable, refuelable SmallSats is a viable option to inspect geosynchronous satellites. The propellant requirement to transfer to a targeted geosynchronous satellite, perform a proximity inspection mission, and transfer back to the carrier platform in a nearby orbit is determined. Convex optimization and traditional optimization techniques are explored, determining minimum propellant trajectories. Propellant is measured by the total required change in velocity, delta-v. The trajectories were modeled in a relative reference frame using the Clohessy-Wiltshire equations. Mass estimations for the carrier platform and the SmallSat were determined by using the rocket equation. The mass estimates were compared to the mass of a single, non-refuelable satellite performing the same geosynchronous satellite inspection missions. From the minimum delta-v trajectories and the mass analysis, it is determined that using refuelable SmallSats and a carrier platform in a nearby orbit can be more effcient than using a single non-refuelable satellite to perform multiple geosynchronous satellite inspections.
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Zaheer, Muhammad. "Kinematic orbit determination of low Earth orbiting satellites, using satellite-to-satellite tracking data and comparison of results with different propagators." Thesis, KTH, Geodesi och geoinformatik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-142627.
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The GPS data from Challenging Mini-satellite Payload (CHAMP) is used for its orbit determination for the epoch day of January 1st 2002. The orbit of CHAMP is computed from the GPS data and ionospheric effects are removed by frequency combination. Further, the orbits of CHAMP for the same epoch day are computed using the satellite tool kit (STK) employing simplified general perturbations (SGP4) and a high precision orbit propagator (HPOP). Results from both techniques (GPS computed orbit and STK computed orbit) are compared. Furthermore, orbits computed using GPS data are also compared with jet propulsion laboratory’s published CHAMP spacecraft orbit and we have found that root mean square difference in ECEF position X component is below 0.01km other than some spikes at poles. The standard deviation of the difference in ECEF position X coordinate is 11.7m. The accuracy of our computed satellite positions (using GPS data) is about 12 metres for other than polar areas. However there are some occasional spikes, especially at poles, having maximum errors (about 0.055 km).
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Stelianos, Haralambos. "The use of commercial Low Earth Orbit satellite systems to support DoD communications." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1996. http://handle.dtic.mil/100.2/ADA326969.
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Thesis (M.S. in Electrical Engineering) Naval Postgraduate School, December 1996."December 1996." Thesis advisor(s): Tri T. Ha and Vicente Garcia. Includes bibliographical references (p. 95-97). Also available online.
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Marandi, Said Rashed. "On some aspects of dynamics, modelling, and attitude analysis of satellites." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/29019.
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The thesis identifies several limitations in the modelling and attitude stability analysis of two classes of spacecraft: rigid and flexible satellites. Attractive methods
are proposed which promise to have far reaching consequences in spacecraft dynamics. These alternatives, developed based on techniques of differential equations,
classical mechanics, and differential topology, are indicated below.
(a) An Alternate Transition from the Lagrangian of a Satellite to Equations of Motion
The classical procedure requires the Lagrangian to be expressed in terms of the corresponding generalized coordinates of the problem. This requirement significantly
complicates the derivation of the equations of motion through an introduction
of a set of librational generalized coordinates, which is strictly not a part of the dynamical system. Using the Lagrangian in the natural variables (angular velocity, direction cosines, and vibrational coordinates), one develops a procedure for derivation of equations of motion without an a priori choice of rotational generalized coordinates. For the case of a satellite with two flexible plate-type appendages, for example, the approach reduced the formulation time to one-third.
(b) Synthesis and Depiction of Rotational Motion of Satellites and Robots
The rotational coordinates in use for numerical prediction of orientation of a satellite are either singular or redundant. Furthermore, they lack a convenient visual interpretation. A new set of coordinates is proposed and an associated representation is developed which avoids these limitations. The procedure is applied to represent and integrate numerically the librational response of the flexible satellite mentioned in (a).
(c) Resolution of Attitude Stability of Delp Satellites
The development here tackles a long outstanding problem in the area of attitude stability of satellites. The resolution of this problem through normalization of the Hamiltonian leads to a better appreciation of stability associated with the class of gravity gradient structures such as the proposed Space Station.Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate