Polarimetric PALSAR System Model Assessment and Calibration

Abstract

Abstract-Polarimetric PALSAR system parameters are assessed using data sets collected over various calibration sites. The data collected over the Amazonian forest permits validating the zero Faraday rotation hypotheses near the equator. The analysis of the Amazonian forest data and the response of the corner reflectors deployed during the PALSAR acquisitions lead to the conclusion that the antenna is highly isolated (better than -35 dB). Theses results are confirmed using data collected over the Sweden and Ottawa calibration sites. The 5-m height trihedrals deployed in the Sweden calibration site by the Chalmers University of technology permits accurate measurement of antenna parameters, and detection of 2-3 degree Faraday rotation during day acquisition, whereas no Faraday rotation was noted during night acquisition. Small Faraday rotation angles (2-3 degree) have been measured using acquisitions over the DLR Oberpfaffenhofen and the Ottawa calibration sites. The presence of small but still significant Faraday rotation (2-3 degree) induces a CR return at the crosspolarization HV and VH that should not be interpreted as the actual antenna cross-talk. PALSAR antenna is highly isolated (better than -35 dB), and diagonal antenna distortion matrices (with zero cross-talk terms) can be used for accurate calibration of PALSAR polarimetric data.

Calibration and Validation of Polarimetric ALOS2-PALSAR2

“…Using CR deployed in the Amazonian rainforests, Touzi and Shimada [6] showed that the PALSAR antenna is highly isolated (−37 dB isolation) [9,10]. The thorough investigation they conducted in [6] using PALSAR data collected over various calibration sites (with CRs), in Japan (JAXA, Sweden (Chalmers University), Germany (DLR), and Canada (CCRS), in addition to the ones collected over the Amazonian rainforests, led to the following conclusions:…”

“…The use of various calibration sites led to confusion that arose at the 2006 ALOS Calibration/Validation meeting regarding the actual PALSAR antenna isolation. The presence of Faraday rotation in addition to the uncertainty regarding the actual isolation of the PALSAR antenna, led to mixed conclusions regarding the actual isolation of the H-V PALSAR antenna [8,9,11].…”

“…Like L-band JERS-1 SAR and ALOS PALSAR, PALSAR-2 measurements might be affected by Faraday rotation. In the past, the use of corner reflector (CR) measurements in the presence of Faraday rotation led to mixed conclusions regarding the actual isolation of the ALOS-PALSAR antenna [7][8][9]. PALSAR antenna measurements using CR deployed in Germany and Australia led to the conclusion that the PALSAR antenna is not highly isolated (−23 dB isolation) [7,8].…”

“…PALSAR antenna measurements using CR deployed in Germany and Australia led to the conclusion that the PALSAR antenna is not highly isolated (−23 dB isolation) [7,8]. However, the use of the CR measurements collected in the Amazonian rainforests, at low Faraday rotation conditions, led to the conclusion that PALSAR antenna is highly isolated, with a cross-talk lower than −37 dB [3,5,6,9,10].…”

Soil Moisture Retrieval Using Polarimetric SAR Data and Experimental Observations in an Arid Environment

“…Most studies use dual polarization SAR data and very rarely use full polarimetric SAR data. Generally, C-and X-band SAR data are used by researchers for soil moisture retrieval [6][7][8][9], and some of them used the L-band due to less sensor availability [10][11][12][13][14][15][16]. Generally, the physical backscatter models for soil moisture retrieval are based on theoretical scattering models, and approaches to the semi-empirical model involve extending or modifying empirical observations.…”