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# Measuring and modelling the impact of the ionosphere on space based synthetic aperture radars

Mannix, Christopher Robert (2016)
Ph.D. thesis, University of Birmingham.

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## Abstract

Synthetic aperture radar (SAR) is a technique widely used in applications that require all-weather imaging. The ionosphere affects the operation of these radars, with those operating at L-band (1-2 GHz) and below at risk of being seriously compromised by the ionosphere. A method of using Global Positioning System (GPS) data to synthesize the impact of the ionosphere on SAR systems has been presented. The technique was used to assess the viability of using a signal phase correction derived from a reference location in a SAR image to correct ionospheric effects across the image. A dataset of SAR images and GPS measurements collected simultaneously on Ascension Island were used to test two techniques for deriving ionospheric strength of turbulence (C$$_k$$L) from SAR images – one using measurements of trihedral corner reflectors (CR) and the other measurements of natural clutter. The CR C$$_k$$L values showed a correlation of 0.69 with GPS estimates of C$$_k$$L, whilst the clutter measurements showed a correlation of up to 0.91 with the CR values. Finally, a study of using the effects of intensity scintillation on SAR images to measure the S$$_4$$ index was performed. The study was not able to reproduce previous results, but produced significant practical conclusions.

Type of Work: Ph.D. thesis. Cannon, Paul S. Colleges (2008 onwards) > College of Engineering & Physical Sciences School of Engineering, Department of Electronic, Electrical and Systems Engineering Publication arising from thesis: Mannix, C. R., D. P. Belcher, P. S. Cannon, and M. J. Angling (2016), Using GNSS signals as a proxy for SAR signals: Correcting ionospheric defocusing, Radio Sci., 51, 60–70. http://dx.doi.org/10.1002/2015RS005822 SAR, Synthetic Aperture Radar, Ionosphere, GNSS, Space Weather, GPS, Scintillation, Radar QC PhysicsTK Electrical engineering. Electronics Nuclear engineering University of Birmingham 6869
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