Thesis (MScIng)--University of Stellenbosch, 2005. / Bibliography. Also available via the Internet.

Thesis (M.S.C.I.T.)--Regis University, Denver, Colo., 2006. / Title from PDF title page (viewed on May 24, 2006). Includes bibliographical references.

Thesis (M.S.)--Rochester Institute of Technology, 2007. / Typescript. Includes bibliographical references (leaves 145-149).

Texte remanié de: Doctoral diss.--Austin--University of Texas, 1992. Titre de soutenance : Privatizing space-derived data : a case study of the effects of the Land remote-sensing commercialization act of 1984 on the academic geography community. / Notes bibliogr. Bibliogr. p.287-314. Index.

Th.--Lett.--Paris--Ecole des hautes études en sciences sociales, 1988.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 199-209). Also available via the Internet.

Η παρούσα διπλωματική εργασία πραγματεύεται την μελέτη και κατασκευή του συστήματος τροφοδοσίας του UPSat, ενός δορυφόρου τύπου Cubesat. Η εργασία αυτή εκπονήθηκε στο Εργαστήριο Ηλεκτρομηχανικής Μετατροπής Ενέργειας του Τμήματος Ηλεκτρολόγων Μηχανικών και Τεχνολογίας Υπολογιστών της Πολυτεχνικής Σχολής του Πανεπιστημίου Πατρών. Σκοπός είναι η μελέτη και η κατασκευή των βασικών διατάξεων του συστήματος τροφοδοσίας ώστε να καλύπτονται οι ενεργειακές απαιτήσεις όλων των υποσυστημάτων του δορυφόρου. Αρχικά μελετώνται οι συνθήκες που θα πρέπει να αντιμετωπίσει ο δορυφόρος κατά την αποστολή του. Παρουσιάζονται τα βασικότερα υποσυστήματα του δορυφόρου και οι διαθέσιμες επιλογές τροχιάς, ενώ με βάση στοιχεία προηγούμενων αποστολών επιλέγεται η τοπολογία του συστήματος και γίνεται ο ισολογισμός ισχύος. Στη συνέχεια γίνεται η ανάλυση των τροφοδοτικών που θα κατασκευαστούν, η επιλογή των κατάλληλων τοπολογιών και ο υπολογισμός των απαραίτητων στοιχείων των μετατροπέων. Ακολουθεί η προσομοίωση των κυκλωμάτων με κατάλληλο λογισμικό, το πρόγραμμα PSpice, ώστε τα αποτελέσματά τους να συγκριθούν με τα θεωρητικά αλλά και με αυτά της τελικής κατασκευής. Το επόμενο βήμα είναι η κατασκευή των κυκλωμάτων. Παρουσιάζονται τα τεχνικά χαρακτηριστικά των βασικών εξαρτημάτων και γίνεται η ανάλυση του προγράμματος του μικροελεγκτή για την παραγωγή παλμών. Επιπρόσθετα γίνεται αναφορά και στις διατάξεις μετρήσεων και ελέγχου του συστήματος. Τέλος δίνονται οι μετρήσεις και τα παλμογραφήματα που προέκυψαν από τις διατάξεις για την εξαγωγή συμπερασμάτων. / This diploma thesis deals with the design and construction of the Power Supply System of UPSat, a satellite based on the Cubesat standard. The work was conducted at the Laboratory of Electromechanical Energy Conversion of the Department of Electrical and Computer Engineering of Engineering School of University of Patras. The aim is to design and construct the main circuits of the Power Supply Unit, in order to cover all the energy required by the subsystems of the satellite. Initially, the conditions to be faced by the satellite during the mission are taken into consideration. The basic subsystems of the satellite and the orbit options are presented and based on data from previous missions, the topology of the whole system is selected. Then follows the theoretical analysis of the power supply unit to be built, choosing the appropriate topologies followed by the calculation of all the necessary components. The next step is to simulate all the circuits with the appropriate software, in this case the PSpice program, in order to compare the results with the theoretical but also with those of the final construction. Following, begins the construction of the circuits. Technical characteristics of the basic components are presented and also the analysis of the program of the microcontroller that generates a pulse for a mosfet. In addition, there is the analysis of the measurements and control circuitry. Finally oscilloscope graphs and measurements, occurred from the experiments transacted after the finalization of the construction, are adduced.

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.

Thesis (MScEng)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: This study investigates the theory of precision satellite orbit propagation and satellite lifetime prediction and lead to the development of two necessary software tools for analysis in these fields. Precision propagation was achieved through the implementation of Cowell's method of special perturbations, considering perturbations due to a 70x70 asymmetrical gravity field, atmospheric drag, Luni-Solar attraction and Solar radiation pressure. The satellite's perturbed equations of motion were integrated utilizing a seveneighth order Runge-Kutta-Fehlberg numerical integration procedure, limiting error propagation by employing adaptive step size control. The MSlS-90 atmospheric density model, providing for diurnal and semi-annual variations, was employed to determine atmospheric density. Care was taken in the precision modelling of the motion of the 12000 equator and equinox. Propagation results for this test case proved to be superior to the SGP4 propagator and a commercial package. The long-term effects of Earth oblateness and atmospheric drag on a satellite's orbital elements were investigated and applied to the orbit decay prediction problem. Orbit decay was predicted by integrating the rates of change of the orbital elements due to Earth oblateness and atmospheric drag. A semi-analytical technique involving Runge-Kutta and Gauss-Legendre quadrature was employed in the solution process. Relevant software was developed to implement the decay theory. Optimum drag coefficients, estimated from drag analysis using precision propagation, were used in decay prediction. Two test cases of observed decayed satellites were used to evaluate the theory. Results for both test cases indicated that the theory fitted observational data well within acceptable limits. / AFRIKAANSE OPSOMMING: 'n Ondersoek is gedoen oor die teorie van presiesie satelliet-wentelbaan vooruitskatting en satelliet-wentelbaanleeftyd afskatting en het gelei tot die ontwikkeling van twee analiseprogramme vir gebruik in hierdie vakgebiede. Presiesie vooruitskatting is bereik deur die gebruik van Cowell se metode van spesiale perturbasies, wat die invloed van 'n nie-simmetriese 70x070 gravitasieveld, atmosferiese sleur, Son-Maan aantrekkingskragte en druk van sonradiasie, in ag neem. Die satelliet se versteurde bewegingsvergelykings is numeries ge-ïntegreer deur gebruik te maak van die sewe-agste orde Runge-Kutta- Fehlberg metode wat fout-voortplanting inhibeer deur gebruik te maak van 'n aanpasbare integrasiestaplengte. Die MSIS-90 atmosferies model, wat voorsiening maak vir dag-nag en half-jaarlikse atmosferiese variasies, is gebruik vir die berekening van atmosferiese digtheid. Sorg is gedra by die presiesie modellering van die beweging van die J2000 ekwator en ekwinokse. Resultate vir hierdie toetsgeval toon meer voortreflik te wees as die SPG4 - en 'n kommersieël-beskikbare vooruitskatter. Die langtermyn effekte van aard-afplatting en atmosferiese sleur op wentelbaanleeftyd is ondersoek en toegepas op die wentelbaanverval-afskattingsprobleem. Wentelbaanverval is bereken deur die integrasie van die tydsafgeleides van die wentelbaanelement onder invloed van aard-afplatting en atmosferiese sleur. Vir die doel is 'n semi-analitiese tegniek, wat gebruik maak van Gauss-Legendre kwadratuur en Runge-Kutta numeriese integrasie, gebruik gemaak. Nodige rekenaar programmatuur is ontwi kkeI om die vervalteorie te implimenteer. Optimale sleur-koëffisiënte is afgeskat deur van presiesie wentelbaananalise gebruik te maak. Twee gevallestudies van bekende vervalde satelliete is gebruik om die vervalteorie te evalueer. Resultate vir beide gevallestudies toon aan dat eksperimentele resultate werklike vervaltye binne aanvaarbare limiete navolg.

Made available in DSpace on 2014-06-11T19:30:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-08-14Bitstream added on 2014-06-13T18:40:51Z : No. of bitstreams: 1 000732470.pdf: 8779217 bytes, checksum: 636afeee108114a23f86e8666c463685 (MD5) / Muitos estudos sobre os satélites irregulares dos planetasgigantes têm sido publicados, especialmente motivados pelo exponencial aumento no número de objetos conhecidos proporcionado pela era observacional do CCD. Características peculiares, como órbitas altamente excêntricaseinclinadas,bem como distantes dos planetas, são incompatíveis com o modelo deformação local através deacreção de matéria do disco circumplanetário, de modoque apenas acaptura gravitacional explica a existência detal classe. No problema restrito de três corpos, capturasgravitacionais são de caráter temporário, de modo quefaz-se necessário um mecanismo não trivialde captura compatível com a existência desses objetos. Muitas têm sido propostas, mas as origens dos satélites irregulares de Júpiter, oplaneta com maior número de objetos da referidaclasse, ainda permanece indeterminada. Estudando o mecanismo de captura de asteroides binários,sob o cenário do problemade 4 corpos, consideram Sol eJúpiter como objetosprimários, obtivemos uma distribuição orbital de objetos capturados bastante semelhante à distribuição observada para os satélites irregular jovianos. O referido estudo também nos permitiucompreender as características intrínsecasmais relevantes do mecanismo.As evidencias nos permitem propor uma nova teoria consistente comas origens dos satélites irregulares,vinculada às origens da família Hilda de asteroides dos cinturão principal / Irregularsatellites of the giant planets have been largely studied since the CCD observational era exponentially increased the number of known objects of such class. Peculiar features of these objects,suchas highly inclined and eccentric orbits, and alsotheir distancefrom the planet are strong signaturesof non locally formed objects. Since gravitational captures underthe three-body theories are temporary, a non trivialcapture mechanism is necessary to explain their origin. Many theories about the origins of suchobjects have beenproposed, but the origins of irregular satellites of Jupiter,in particular, still remain undetermined, and Jupiter is the planet with the larger population ofsuch objects. Here we presentefforts devoted to the comprehension of binary-asteroid capture mechanism. We obtained a comparable orbital distribution of captured objects to the distribution of known objects. Furthermore, many relevant features of the mechanism were elucidated. The evidences lead us to propose a consistent theory for the origins ofirregularJovian satellites constrained tothe origin of Hilda family’s of asteroid