COSMO-SkyMed: Image quality achievements

COSMO-SkyMed is the Italian Remote Sensing program which foresees the utilization of a constellation of four SAR Satellites in Low Earth Orbit, dedicated to the management, control and exploitation of Earth resources for civil and defense applications. The Program is completely funded by the Italian Government, mainly through the Italian Ministry of Research (MIUR) and the Ministry of Defense (I-AD). Thales Alenia Space Italia is responsible for the design, development and verification of the complete constellation. The complete constellation has been deployed in orbit (June 2007, December 2007, November 2008, and October 2010), the commissioning and the operative qualification (at satellite and constellation levels) with the achievement of full performance has been completed, too. From the very early days of the mission images were generated as nominal products by both the operational systems and the calibration&validation (CALVAL) facility. The data takes and level 1 products were analyzed to serve the main goal of the commissioning phase: the provision of calibrated and verified SAR products to the defense, civil institutional, commercial and scientific user community. The results of the statistical and individual product analysis added up in some instrument parameter adjustment and processing parameter optimization steps; these were performed in the a few ground segment processor releases of which the last took place at the conclusion of the operative qualification. From there on, all data takes and SAR products from spotlight (ES), stripmap (HIMAGE), alternating polarization (PP) and scansar (WR and HR) modes are considered as “operational” in terms of commanding, processing, product format and performance. This paper presents the different product types and the achieved product performance parameters. While product characterization and calibration measurements started early, the final SAR verification had to wait for the complete verification of all input products (specifically the orbit and attitude data) and the finalization of the overall SAR system performance and verification. Thus more than thousands “operational” products of all modes and variants have been used for final verification of basic characteristics like format, saturation degree, scene location and extent. A subset of specific acquisitions over calibration sites were processed to various product variants and analyzed with respect to point target responses and radiometry. These measurements confirmed the very excellent COSMO-SkyMed product performance in terms of: · focusing quality and resolution: since the overall SAR system performance and stability are outstanding, some margins in the spotlight azimuth beam steering sequence and processing have been invested in an improved IRF performance. This yields ratios to spatial resolution in azimuth and ground range, over an access region [20° .. 60°], better than 1m · sensitivity: the NEσ° is always better than the specified value (-22dB) for all the operation modes as well as the ambiguity to signal ratios · radiometry: the calibration effort, the pointing accuracy and the operational pattern correction and normalization result in products with a radiometric accuracy better than 1 dB.