| ABSTRACT
With the SAR
sensor PALSAR on board the Advanced Land Observing Satellite,
the first spaceborne fully polarimetric L-band SAR instrument has been
launched into orbit. For L-band, Faraday rotation can reach
significant values degrading the quality of the received SAR
data. Therefore, the estimation and correction of Faraday rotation
effects is a prerequisite for data quality and continuity.
Vertical
total electron content (TEC) values available from Global Ionosphere
Maps are generated on a daily basis at the Center for Orbit
Determination in Europe, using data from about 150 GPS sites of
the International GNSS service and other institutions. However,
the spatial resolution of these maps is very low comprising a grid
spacing of only 2.5° (lat) and 5° (lon). Also the
overall accuracy is limited and is generally considered to be within 5
x 1016 e-/m2. In the course of
developing methods for
estimating Faraday rotation, datasets were found that demonstrated the
utility of SAR data to measure ionospheric events with unprecedented
precision and spatial resolution. With a priori knowledge of the
satellite pointing geometry and local geomagnetic field, the
contribution of TEC to the Faraday rotation can be estimated with ~50-m
spatial resolution and a standard deviation
of about 1 TECU (1016
e-/m2). Therefore, L-band SAR data has
high potential to significantly contribute to the study of small scale
ionospheric turbulences.
We will demonstrate localized ionospheric
effects within the 15x60-km frame size of a given PALSAR image, as
well as more regional effects over the course of hundreds of
kilometers in a swath.
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