Thesis (M.S.)--University of Wisconsin--Madison, 1984. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 105-110).

Thesis (M.S.)--University of Wisconsin--Madison, 1964. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. 49-55.

Thesis (M.S.)--University of Wisconsin--Madison. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 68-69).

Thesis (Ph. D.)--University of Wisconsin, 1965. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliography.

Thèse--Faculté des sciences de Paris, 1865.

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 October 24, 2007) Includes bibliographical references (p. 95-98).

Thesis (MScEng)--University of Stellenbosch, 2008. / Bibliography. Also available via the Internet.

Orientador: Ernesto Vieira Neto / Banca: Rodolpho Vilhena de Moraes / Banca: Décio Cardozo Mourão / Resumo: Devido ao grande avanço da tecnologia espacial o número de satélites irregulares conhecidos vem aumentando rapidamente nos últimos anos. O estudo das perturbações que agem sobre estes satélites contribui para explicar a origem e estabilidade da órbita destes corpos celestes. Uma dessas perturbações é a ressonância de evecção que se caracteriza por ser um fenômeno no qual o pericentro da órbita do satélite fica preso na direção do corpo perturbador. Outra perturbação no movimento desses satélites de altas inclinações se dá quando o argumento do pericentro circula ou libra em torno de 90º ou 270º, ou seja, a ressonância Kozai (Kozai 1962). Neste trabalho, é feito um estudo semi-analítico dos efeitos da ressonância de evecção no movimento orbital dos satélites irregulares do planeta Júpiter, utilizando a função perturbadora desenvolvida por Cuk et al. (2004) e que contém termos das ressonâncias de evecção e Kozai. O princípio da média é aplicado somente no movimento orbital do satélite. É feita uma extensa análise do comportamento dos elementos orbitais de uma partícula nas regiões habitadas pelos satélites irregulares. / Abstract: In the recent years, due to the great advance of the space technology, the number of known irregular satellites is increasing quickly. Studying the disturbances which act on these satellites may contribute to explain the origin and stability of the orbit of these satellites. One of the main disturbances is the evection resonance which is characterized by fixing the pericenter of the orbit of the satellite in the direction of the disturbing body. Another disturbance, know as Kozai resonance (Kozai 1962), acts in the movement of those satellites with high inclinations and makes the argument of pericentro circulates or librates around 90º or 270º. In this work is made a semianalytical study of the evection resonance effect in the orbital movement of the irregular satellites of the Jupiter planet. It is used the disturbing function developed by Cuk et al. (2004) which contain terms of evection and Kozai resonances. The principle of the average is only applied in the orbital movement of the satellite. It is made an extensive analysis of the behavior of the orbital elements of a particle in the regions inhabited for the irregular satellites. / Mestre

An important concern in spacecraft engineering is attitude determination control and stabilisation (ADCS) - the combination of applied mathematics, classical physics and modern technology which maintains the pointing direction of one or more axes of an Earth-orbiting satellite. This thesis is a detailed study of a particular type of ADCS which exploits the gravity-gradient effect, which is just the weak tendency for an appropriately shaped body to point naturally in preferred directions; reinforced by magnetorquing, which is the active interaction of the geomagnetic field with a switched current passing through coils in the spacecraft body. The advantages of this technology is that it is low-cost, non-consumable and has no moving parts - so constituting no limitation to the satellite's life. The thesis is a detailed study of this form of ADCS with specific application to low Earth polar-orbiting (LEO) satellites, for which it is particularly suitable. The work is also a study in attitude determination based solely on a 3-axis magneometer measurement of the geomagnetic field, which is in principle a simple way, in terms of technology, of determining the attitude of the spacecraft, and from this controlling the attitude, if mediated by an on-board computer implementing appropriate algorithms. The results are for the most part practically based on the author's involvement with two satellites over a six year period with the satellites UOSAT-1 and UOSAT-2, which were designed, built, and continue to be controlled from the University of Surrey. A practical innovation in 2-axis attitude control is described: the active 'delibration' by active damping of a gravity-gradient controlled LEO satellite in an attitude-stabilised state, using a threshold comparison algorithm. A new theory and algorithms are then developed for 3-axis attitude control, based on a complementary use of magnetorquing and gravity gradient. Subject to further development these could alter the general perception of the most effective way of controlling low Earth orbiting satellites.

The C and Ku bands that have been the backbone of satellite telephony and data networks in the past are limited in the amount of bandwidth they provide. Consequently, some broadband Internet services have started to move into the Ka band in order to utilise the bandwidth at these higher frequencies. The use of higher frequencies led to fade mitigation design considerations that had not previously been necessary, as fixed power margins had been sufficient to guarantee high availability. This thesis reviews the majority of fade mitigation techniques that are available and simulates a scenario with several combined in a hybrid scheme. The simulations were made possible by several innovative components, including a near-optimum short-term fade predictor, a procedure capable of simulating the effect of site diversity with a single time series of attenuation and a dual-channel protocol structure that is able to increase availability of control information at V band. The near-optimum short-term fade predictor is compared with several other short-term fade predictors and is shown to perform better in terms of the root-mean-square error and by the cumulative distribution of over-predictions. Also noteworthy is the fact that predictors based on fade slope perform very poorly when compared with signal processing and statistical methods of prediction. The procedure capable of producing the effects of site diversity on a single time series of attenuation is described. The results of this procedure are compared with the ITU-R model for site diversity improvement and an acceptable fit is shown. A dual-channel protocol structure capable of increasing control information availability at V band is presented and the availability of this scheme is compared to the availability of current fixed-margin C and Ku band satellite links. While the availability at V band improves via this technique, it does not improve enough to compare favourably with that found in the lower frequency bands. A software turbo decoder capable of decoding the DVB-RCS turbo code is also described in this work since this was not available through other means. The fade dynamics at V band are reviewed and compared with the ITU-R models. The fade slope model gives a good visual fit but the fade duration model is very inaccurate. Finally, the simulation results show that high availability satellite communication is possible at V band, critically, if both site diversity and frequency diversity are available to mitigate the hub and VSAT fading respectively. Signal processing and power control are also found to be complementary techniques.