Measurement of ionospheric Faraday rotation in simulated and real spaceborne SAR data

Abstract

The influence of the atmosphere on a frequencymodulated
electromagnetic wave traversing the ionosphere is becoming increasingly important for recent and upcoming lowfrequency
and wide-bandwidth spaceborne synthetic aperture radar (SAR) systems. The ionized ionosphere induces Faraday
rotation (FR) at these frequencies that affects radar polarimetry and causes signal path delays resulting in a reduced range resolution.
The work at hand introduces a simulation model of SAR
signals passing through the atmosphere, including both frequencydependent FR and path delays. Based on simulation results from this model [proven with real Advanced Land Observing Satellite Phased Array L-band Synthetic Aperture Radar (PALSAR) data], estimation of FR in quad-polarized SAR data using the given approach is shown for raw, range-compressed, and focused radar images. Path delays and signal chirp bandwidth effects are considered.
Investigations discuss the suitability of raw and compressed
data versus combination of total electron content maps with the Earth’s magnetic field for FR estimation and deduced from a large number of analyzed PALSAR data sets.