Date of Award


Document Type


Degree Name

Master of Science in Applied Physics


Department of Engineering Physics

First Advisor

Christopher G. Smithtro, PhD


Ionospheric scintillation of Global Positioning System (GPS) signals threatens navigation and military operations by degrading performance or making GPS unavailable. Scintillation is particularly active, although not limited to, a belt encircling the earth within ± 20 degrees of the geomagnetic equator. This belt also hosted roughly half of the completed U.S. military operations in the last decade. The authors examined scintillation data from Ascension Island, United Kingdom, and Ancon, Peru, in the Atlantic longitudinal sector as well as data from Parepare, Indonesia, and Marak Parak, Malaysia, in the Pacific longitudinal sector. From these data, they calculate percent probability of occurrence of scintillation at various intensities described by the S4 index. In addition, they determine Horizontal Dilution of Precision (HDOP) at one minute resolution; examine diurnal, seasonal, and solar cycle characteristics; and compare latitudinal and longitudinal data. Their findings are consistent with previous research, but unlike previous research they attempt to replace, or impute, missing S4 values to better capture the extent of scintillation. In doing so, they study data gaps, or holes, and characterize them. The scheme results in an increase in the observed fraction of scintillated satellites.

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DTIC Accession Number