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Full-Text Articles in Physical Sciences and Mathematics
Radiometric Analysis Of Daytime Satellite Detection, Katherine B. Lilevjen
Radiometric Analysis Of Daytime Satellite Detection, Katherine B. Lilevjen
Theses and Dissertations
A radiometric model for daylight satellite detection is developed and used to evaluate the effects of various parameters on signal-to-noise ratio (SNR). Detection of reflected sunlight from a low-earth orbit, diffuse, planar satellite by a single-pixel infrared photovoltaic detector is considered. Noise considered includes photon noise from the background and signal, as well as thermal noise. Parameters considered include atmospheric conditions, optical parameters, and detector parameters. The Phillips Laboratory Expert-assisted User System, an atmospheric modeling tool that employs the MODTRAN and FASCODE transmission codes, is used to model wavelength-dependent atmospheric transmission and background radiance. The SNR is found to increase …
Modeling E & F Region Ionospheric Response To X-Ray Solar Flares, Annette M. Parsons
Modeling E & F Region Ionospheric Response To X-Ray Solar Flares, Annette M. Parsons
Theses and Dissertations
This research takes an existing ionospheric model and modifies it to include the effects of solar flare activity. Solar flares are a localized explosive release of magnetic energy that appears as a sudden, short-lived brightening in the sun’s chromosphere. This additional energy is deposited in the earth’s ionosphere, temporarily changing its properties, which can affect military communications. Studying the effects of moderate solar flares will improve our understanding of the ionosphere’s response, leading to better operational models. Modification of the model is accomplished by adding a flare irradiance model to represent solar irradiance changes due to a flare. The irradiance …
A Climatological Study Of Equatorial Gps Data And The Effects On Ionospheric Scintillation, Katharine A. Wicker
A Climatological Study Of Equatorial Gps Data And The Effects On Ionospheric Scintillation, Katharine A. Wicker
Theses and Dissertations
Ionospheric scintillation is detrimental to radio signals, especially those from the global positioning system. Such scintillation is caused when a signal permeates the ionosphere through plasma bubbles. The signal’s phase and amplitude can be altered, and a receiver on the ground can lose lock on the GPS signal. Measured using a zero to one index known as S4, scintillation severity is based upon season, solar cycle, time of day, location and frequency. The most severe scintillation occurs at the equatorial anomaly, or fifteen degrees north and south of the equator. Seven years of data from fifteen different locations around the …
Comparison Of Ray Tracing Through Ionospheric Models, Shayne C. Aune
Comparison Of Ray Tracing Through Ionospheric Models, Shayne C. Aune
Theses and Dissertations
A comparison of ray tracing predictions for transionospheric electromagnetic wave refraction and group delays through ionospheric models is presented. Impacted applications include over-the-horizon RADAR, high frequency communications, direction finding, and satellite communications. The ionospheric models used are version 2.1 of Utah State University's Global Assimilation of Ionospheric Measurements (USU GAIM) model and the 2001 version of the International Reference Ionosphere (IRI) model. In order to provide ray tracing results applicable to satellite communications for satellites at geosynchronous orbit (GEO), a third ionospheric model is used to extend the sub-2000-km USU GAIM and IRI ionospheric specifications to 36540 km in altitude. …