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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
271

Ultra low frequency (ULF) waves observed at mid to low latitudes during daytime using low Earth orbit (LEO) satellite and ground-based data.

Ndiitwani, Dzivhuluwani Christopher. January 2011 (has links)
The launch of German geoscience satellite CHAMP inspired the increased interest in the study of ultra low frequency waves. In this work data from low Earth orbiting (LEO) German CHAMP satellite and South African ground-based magnetometer data were used to study geomagnetic pulsations, in particular continuous pulsations, Pc3, with periods in the range 10-45 seconds. Both Fast Fourier Transform (FFT) and Maximum Entropy Spectral Analysis (MESA) were used as analysis techniques to compute and compare spectra. We simulated a Pc3 oscillation using a sinusoidal function in order to test and establish appropriate parameters to use on the application of these analysis techniques. In this study the region chosen for a low latitude geomagnetic pulsations study excludes high current regions such as polar regions where field aligned currents occur. The structure of low-latitude pulsations was studied by comparing satellite and ground magnetic field measurements. The magnetic field measurements observed in the topside ionosphere by CHAMP were compared to Hermanus data for times when CHAMP crossed the ground station L-shell. The data were analysed for Pc3 pulsation activity using the MESA method to visualise field line resonance (FLR) in the vector magnetometer data. A number of discrete frequency oscillations for the fast mode wave were observed, one of which drives FLR at characteristic latitude as detected by both ground and satellite measurements. The toroidal mode frequency on CHAMP experiences a Doppler shift due to the rapid motion across the resonance region. Polarization hodograms in the resonance region show the expected 900 rotation of the field line resonant magnetic field components. We present first time ob- servations of toroidal standing Alfv´en mode oscillation with clearly L-dependent frequencies in the inner magnetosphere for L < 3. Our observations show FLR frequency continuously increasing as a function of decreasing latitude down to L = 1.6 and then decrease as a result of the larger plasma density of the upper ionosphere. The L-dependent frequency oscillations were observed in the presence of broadband compressional wave spectra. Our observation confirms the well-known magnetohydrodynamic (MHD) wave theoretical prediction of a compressional wave being the driver of the field line resonance, and that the Pc3 pulsations do not have a source with the same frequency structure. Keywords: ULF waves, Fast Fourier Transform, Maximum Entropy Spectral Analysis, CHAMP satellite, Geomagnetic pulsations, Pc3, Alfv´en wave, Field line resonance. / Thesis (Ph.D.)-University of KwaZulu-Natal, Westville, 2011.
272

An analysis of the circularization of elliptic satllite orbits caused by atmospheric drag

Cowley, John Rosette 12 1900 (has links)
No description available.
273

Data transmission via satellites for aircraft malfunction detection and prediction

Fontaine, Bernard Alain 05 1900 (has links)
No description available.
274

Interplatform links /

Purvinskis, Robert Andrew Janis. Unknown Date (has links)
Thesis (MEng(Telecommunications))--University of South Australia, 2003.
275

Doppler compensation for LEO satellite communication systems /

Ah-Thew, George Patrick. January 1998 (has links)
Thesis (Ph.D.) -- McMaster University, 1998. / Includes bibliographical references (p. 251-271). Also available via World Wide Web.
276

Control of a satellite based photovoltaic array for optimum power draw

Cooper, Sean. January 2008 (has links)
Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: photovoltaic; solar satellite; optimize; dc-dc. Includes bibliographical references (leaves 51).
277

Theory, design and implementation of a digital receiver for the Advanced Communications Technology Satellite (ACTS) beacons /

Sylvester, William R., January 1992 (has links)
Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / 1 ill. in back pocket. Vita. Abstract. Includes bibliographical references (leaves 224-228). Also available via the Internet.
278

Study of slant path attenuation ratios derived from a dual-polarized radar /

Pollard, Kimberley Jeanne, January 1990 (has links)
Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 130-133). Also available via the Internet.
279

L'U.I.T. [Union internationale des télécommunications] et les télécommunications par satellites /

Garmier, Jacques. January 1975 (has links)
Thèse--Sc. pol.--Genève, 1973. / Bibliogr. p. 311-323. Index.
280

Recalage d'images multi-sources : application au recalage d'une image spot et d'une carte /

Roux, Michel, January 1993 (has links)
Th. doct.--Signal et images--Paris--ENST, 1992. / Bibliogr. 167-181. Résumé en français et en anglais.

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