Master of Science

<p>This paper will examine the initial system analysis and system level design for a wideband crosslink between two geostationary satellites. The vehicles will be similar to the Hughes Aircraft Company built IntelSat VI-A in basic configuration for the purposes of this study. The wideband crosslink will carry channelized digital cormnunications to include television signals and duplex voice signals.</p> <p>The paper itself will follow the rigorous format for systems engineering and analysis laid out by Blanchard and Fabrycky [Blanchard]. The study will begin with a Statement of the Problem and Definition of Need; a set of system requirements will bound the project; and the process will follow through preliminary design and tradeoff analysis.</p> / Master of Science

No description available.

Tsz-Shing Tam. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 84-87). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgments --- p.ii / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Literature Review --- p.6 / Chapter 3 --- System Model --- p.12 / Chapter 3.1 --- Static Architecture --- p.12 / Chapter 3.2 --- Dynamics --- p.15 / Chapter 3.3 --- Communication Paradigm --- p.16 / Chapter 3.4 --- Metric --- p.17 / Chapter 4 --- Routing Algorithms --- p.19 / Chapter 4.1 --- Minimum Hops Algorithm (MHA) --- p.20 / Chapter 4.2 --- Minimum Cost Algorithm (MCA) --- p.21 / Chapter 4.3 --- Mesh Algorithm (MA) --- p.24 / Chapter 4.3.1 --- Construction of the Set of Min-hop Paths --- p.24 / Chapter 4.3.2 --- Choosing a Path in S0 --- p.29 / Chapter 4.4 --- k-mesh Algorithm (KMA) --- p.29 / Chapter 4.4.1 --- Finding Sk --- p.30 / Chapter 4.4.2 --- Choosing a path in Sk --- p.34 / Chapter 4.5 --- Revised Mesh Algorithm (RMA) --- p.34 / Chapter 5 --- Reservation Strategies --- p.36 / Chapter 5.1 --- Introduction --- p.36 / Chapter 5.2 --- Notations --- p.38 / Chapter 5.3 --- Basic Reservation Strategy (BRS) --- p.39 / Chapter 5.4 --- Enhanced Reservation Strategy (ERS) --- p.41 / Chapter 5.5 --- Successor Reservation Strategy (SRS) --- p.43 / Chapter 6 --- Experiment --- p.45 / Chapter 6.1 --- Comparison on Routing Algorithms --- p.47 / Chapter 6.2 --- Comparison on Reservation Strategies --- p.64 / Chapter 7 --- Conclusion --- p.72 / Chapter A --- Existence of paths in Sk --- p.75 / Chapter B --- Estimation of basic reservation strategy guaranteed time --- p.79 / Chapter B.1 --- Basic reservation strategy --- p.79 / Chapter B.2 --- Estimation on Guaranteed Duration --- p.80 / Bibliography --- p.83

The study of outer radiation belt dynamics has been ongoing for over 5 decades. Outer radiation belt dropouts involve the rapid lost of electron fluxes at the main phase of a storm and subsequent recovery. The characteristics of the dropouts are many and varied. This study examines the Geosynchronous Earth Orbit (GEO) and the ionospheric responses during Stream Interface (SI) andMagnetic Cloud (MC) events, using a combination of ground based and satellite instruments. SI- and MC-driven dropout events were inspected from summary plots of the Synchronous Orbit Particle Analyser (SOPA) instruments from the year 1996 to 2007. Comprehensive studies were done on six selected events. Analysis of the data from the instruments indicate that SIs and MCs are important lost drivers with significant differences in GEO and ionospheric environment. To validate the data and test for consistent response of the events, the Superposed Epoch Analysis (SEA) technique was used. The ground based measurements also revealed how the absorption peaks in the ionosphere correlated with dropouts and geophysical activity. Ionospheric absorption during SI associated dropouts was enhanced for 5 < L < 6, while significant peaks in ionospheric absorption extended to lower L during MC driven dropouts. Wave-particle interactions and southward Interplanetary Magnetic Field (IMF-Bz) are apparent causes for the precipitation. This analysis showed that, within the confines of the selected events, SI driven dropouts were more dominant at the declining phase of the solar cycle while the MC driven dropouts were more dominant during solar maximum. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2011.

No abstract available / Thesis (PhD (Electronic Engineering))--University of Pretoria, 2007. / Electrical, Electronic and Computer Engineering / unrestricted

[pt] O objetivo deste trabalho é estender a aplicação do Método Analítico de avaliação de interferências envolvendo redes de satélites não geoestacionários a situações onde as parcelas de interferência dos diversos satélites de uma dada constelação são modeladas como variáveis aleatórias estatisticamente independentes. A análise deste tipo de situação requer o cálculo de um número muito grande de convoluções. Depois de mostrar que o cálculo direto da convolução é computacionalmente viável e que o uso de simulação de Monte Carlo requer um tempo de computação proibitivo para garantir a precisão necessária, o estudo identifica duas alternativas: utilização indireta do teorema do limite central, e integração numérica utilizando a Regra de Quadratura de Gauss. Por último, o presente trabalho apresenta dois exemplos numéricos de aplicação do Método Analítico, onde é possível observar melhorias na precisão dos resultados obtidos, em relação aos obtidos com outros métodos. / [en] The objective of this work is to extend the use of the Analytical Method for assessing the interference involving non-geostationary satellite networks to situations where the interference entries from the various satellites in a given Constellations are modeled as statistically independent random variables. The analysis of this type of situation requires a large number of convolution computations. After showing that the direct approach to numerically compute convolutions is not feasible and that the use of Monte Carlo simulation techniques require a prohibitive computer time to guarantee the necessary accuracy, the study identifies two alternatives: the indirect use of the Central Limit theorem, and numerical integration using Gauss Quadrature Rules. Finally, the present work presents two numerical example applications of the Analytical Method. The obtained results show an accuracy improvement when compared to those obtained using other methods.

Providing affordable Internet access to rural populations in large developing countries to aid economic and social progress, using various non-conventional techniques has been a topic of active research recently. The main obstacle in providing fiber-optic based terrestrial Internet links to remote villages is the cost involved in laying the cable network and disproportionately low rate of return on investment due to low density of paid users. The conventional alternative to this is providing Internet access using geostationary satellite links, which can prove commercially infeasible in predominantly cost-driven rural markets in developing economies like India or China due to high access cost per user. A low-cost derivative of the conventional satellite-based Internet access system can be developed by utilizing an aging geostationary satellite nearing the end of its active life, allowing it to enter an inclined geosynchronous orbit by limiting station keeping to only east-west maneuvers to save fuel. Eliminating the need for individual satellite receiver modules by using one centrally located earth station per village and providing last mile connectivity using Wi-Fi can further reduce the access cost per user. A Ku band system design for rural India based on this concept, using an Intelsat 906 satellite is proposed in this thesis. The path of the satellite and the tracking requirements at village stations are determined. Components required for various blocks of the system are defined. Modulation schemes, FEC, data rates, number of customers to be served, link availability and outage statistics are presented. Quantitative analysis using link budgets and ITU rain models are provided. An optimized system design and a commercial deployment model are suggested which show the system is economically feasible. / Master of Science

The ability to observe resident space objects (RSOs) is a necessary requirement for space situational awareness. While objects in a Low-Earth Orbit are easily ob- servable by ground-based sensors, diffculties arise when trying to monitor objects with larger orbits far above the Earth's surface, e.g. a Geostationary Orbit. Camera systems mounted on satellites can provide an eff ective way to observe these objects. Using a satellite with a speci c orbit relative to the RSO's orbit, one can passively observe all the objects that share the RSO's orbit over a given time without active maneuvering. An orbit can be defi ned by ve parameters: semi-major axis, eccentricity, right ascension of ascending node, inclination, and argument of perigee (a; e; ; i; !). Using these parameters, one can create an orbit that will surround the target orbit allowing the satellite in the Rock-Around Orbit (RAO) orbit to have a 360 degree view of RSOs in the target orbit. The RAO orbit can be applied to any circular or elliptical target orbit; and for any target orbit, there are many possible RAO orbits. Therefore, diff erent methods are required to narrow down the selection of RAO orbits. These methods use distance limitations, time requirements, orbit perturbations, and other factors to limit the orbit selections. The first step is to determine the range of RAO semi-major axes for any given target orbit by ensuring the RAO orbit does not exceed a prescribed maximum al- lowable distance, dmax from the target orbit. It is then necessary to determine the eccentricity range for each possible RAO semi-major axis. This is done by ensuring the RAO still does not exceed dmax but also ensuring that the RAO orbit travels inside and outside of the target orbit. This comprises one half of the rock-around motion. The final step is to determine the inclination of the RAO orbit. Only a small inclination different from that of the target orbit is required to complete the rock-around motion while the maximum inclination is found by making sure the RAO orbit does not exceed dmax. It is then important to consider orbit perturbations, since they can destroy the synchronization between the RAO and target orbit. By examining the e ffects of the linear J2 perturbations on the right ascension of ascending node and argument of perigee, the correct semi-major axis, eccentricity, and inclination can be chosen to minimize the amount of fuel required for station keeping. The optimal values can be found by finding the Delta v needed for di fferent combinations of the variables and then choosing the values that provide the minimum Delta v. For any target orbit, there are multiple RAO orbit possibilities that can provide 360 degree coverage of a target orbit. Even after eliminating some of them based on the methods already described, there are still many possibilities. The rest of the elimination process would then be based on the mission requirements which could be the range of an on-board sensor, the thruster or reaction wheel controls, or any other number of possibilities.

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: TCP; RED; satellite; PEP; STP; performance enhancing proxy; segment caching; IP-ABR; Internet; bandwidth reservation; IP-VBR; congestion avoidance; bandwidth sharing. Includes bibliographical references (p. 98-99).