ALOS PALSAR Products Verification

Abstract

ALOS, an enhanced successor of the Japanese Earth Resources Satellite 1 (JERS-1), was launched from JAXA’s Tanegashima Space Center in January 2006. ALOS operates from a sun-synchronous orbit at 691 km, with a 46-day recurrence cycle carrying a payload of three remote sensing instruments: the Panchromatic Remote Sensing Instrument for Stereo Mapping (PRISM) , the Advanced Visible and Near-Infrared Radiometer type 2 (AVNIR-2) and the polarimetric Phased Array L-band Synthetic Aperture Radar (PALSAR). The PALSAR sensor has the capacity to operate with a wide range of off-nadir angles and resolutions in a single-, dual-, and quad-pol mode. An important contribution to the ALOS mission is the verification of PALSAR products to be distributed by the European ADEN node using the PALSAR processor developed by JAXA. Under contract to ESA/ESRIN the Microwaves and Radar Institute at the German Aerospace Center (DLR) Oberpfaffenhofen and its partners BAE Systems Advanced Technology Centre and CREASO GmbH developed a quality assessment tool (CALIX) for the verification of standard ALOS PALSAR products and also provided support for the verification for the ALOS PALSAR data quality. In addition, a set of corner reflectors and transponders have been deployed at the DLR test site Oberpfaffenhofen throughout the whole commissioning phase to allow an accurate measure of the basic product quality parameters. The quality assessment features of the CALIX software include a product reader, antenna pattern estimation, point target analysis, distributed target analysis, geometric analysis and polarimetric analysis. Results obtained with CALIX on a set of products acquired over the DLR test site will be presented in this paper. Since PALSAR is the first fully polarimetric spaceborne L-band sensor, propagation effects are important new issues to be addressed. The main challenge is to assess the influence of the ionosphere on the polarisation. Different approaches for estimating the Faraday rotation angle have been applied and the results are here compared.