An important contribution to the ALOS mission is the verification and validation of PALSAR products distributed by the European ADEN node. Under a contract with ESA/ESRIN, the Institute has to assess ALOS/PALSAR data quality during the commissioning phase of the instrument and to provide a set of algorithms for quality control throughout the mission lifetime.
Software tools to be developed and implemented include point target analysis, distributed target analysis, geometric analysis, antenna pattern estimation, polarimetric analysis and the estimation and analysis of propagation effects. The framework for this tool set is the in-house developed CALIX software, which is our standard calibration and verification environment also being used within the IOCS for TerraSAR-X.During calibration and verification campaigns, active and passive calibrators (transponders, dihedral and trihedral reflectors) will be deployed as external references, providing well-defined point target responses for product quality assessment.
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, known as Faraday rotation. This effect depends on the Total Electron Content (TEC) in the ionospheric layer below the ALOS spacecraft and is proportional to the wavelength squared. Being negligible for X-band sensors, Faraday rotation is significant in L-band and can reach up to 100° with a pronounced diurnal variation and a strong dependence on solar activity during the 11-year solar cycle.
After the successful launch JAXA is currently performing early functional check-outs. First acquisitions over our Pol-InSAR and calibration test sites are envisaged for April and the detailed planning of the campaigns has started. First results are expected in summer 2006. The PALSAR product verification activity for ESA will be finished early 2007.