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Estimation of path delays, TEC and faraday rotation from SAR data


Jehle, M. Estimation of path delays, TEC and faraday rotation from SAR data. 2009, University of Zurich, Faculty of Science.

Abstract

Spaceborne synthetic aperture radar (SAR) systems are used to measure
geo- and biophysical parameters of the Earth’s surface, e.g. for agriculture, forestry
and land subsidence investigations. Recently launched and upcoming spaceborne SAR
satellites continue the trend of measuring these parameters on a global scale from space
with continually higher accuracies. Larger frequency modulated chirp bandwidths and increased
spatial resolution allow for new and additional information with higher geometric
resolution. One dares to hope that in the near future space borne radar remote sensing
will be the able to contribute to monitoring for earthquake precursors. The use of large
bandwidths, however, causes signal degradation within the ionosphere. Under high solar
activity conditions and at low carrier signal frequency, ionosphere-induced path delays
and Faraday rotation (FR) become significant for SAR applications. The influence of the
troposphere becomes relevant given geolocation accuracy requirements of less than 1 m as
obtained e.g. with TerraSAR-X by the German Aerospace Center (DLR).
By means of an in-depth analysis from radar signal propagation through the atmosphere
and within a standard SAR system model, this dissertation shows possibilities for
measuring, extracting and correcting propagation effects of the two layers most relevant
to accurate spaceborne SAR measurement: the troposphere and ionosphere. In order
to test and crosscheck both measurements and models, data obtained from TerraSAR-X
along with differential GPS position measurements of corner reflectors (CR) at different
altitudes were processed for the tropospheric investigations. Measured data from the
Japanese Phased Array L-band Synthetic Aperture Radar (PALSAR), onboard the Advanced
Land Observing Satellite (ALOS), and simulated data from a potential P-band
system were used to examine and simulate the ionospheric effects and to establish space
borne methods for the extraction of ionospheric total electron content (TEC) and FR from
SAR data. Concluding propositions evaluate possible SAR sensor and signal modifications
to facilitate corrections.

Abstract

Spaceborne synthetic aperture radar (SAR) systems are used to measure
geo- and biophysical parameters of the Earth’s surface, e.g. for agriculture, forestry
and land subsidence investigations. Recently launched and upcoming spaceborne SAR
satellites continue the trend of measuring these parameters on a global scale from space
with continually higher accuracies. Larger frequency modulated chirp bandwidths and increased
spatial resolution allow for new and additional information with higher geometric
resolution. One dares to hope that in the near future space borne radar remote sensing
will be the able to contribute to monitoring for earthquake precursors. The use of large
bandwidths, however, causes signal degradation within the ionosphere. Under high solar
activity conditions and at low carrier signal frequency, ionosphere-induced path delays
and Faraday rotation (FR) become significant for SAR applications. The influence of the
troposphere becomes relevant given geolocation accuracy requirements of less than 1 m as
obtained e.g. with TerraSAR-X by the German Aerospace Center (DLR).
By means of an in-depth analysis from radar signal propagation through the atmosphere
and within a standard SAR system model, this dissertation shows possibilities for
measuring, extracting and correcting propagation effects of the two layers most relevant
to accurate spaceborne SAR measurement: the troposphere and ionosphere. In order
to test and crosscheck both measurements and models, data obtained from TerraSAR-X
along with differential GPS position measurements of corner reflectors (CR) at different
altitudes were processed for the tropospheric investigations. Measured data from the
Japanese Phased Array L-band Synthetic Aperture Radar (PALSAR), onboard the Advanced
Land Observing Satellite (ALOS), and simulated data from a potential P-band
system were used to examine and simulate the ionospheric effects and to establish space
borne methods for the extraction of ionospheric total electron content (TEC) and FR from
SAR data. Concluding propositions evaluate possible SAR sensor and signal modifications
to facilitate corrections.

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Additional indexing

Item Type:Dissertation
Referees:Schaepman M, Geiger A, Weibel R, Meier E, Small D
Communities & Collections:07 Faculty of Science > Institute of Geography
Dewey Decimal Classification:910 Geography & travel
Language:English
Date:2009
Deposited On:19 Feb 2010 09:34
Last Modified:05 Apr 2016 13:56
Number of Pages:120

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