APPLICATION OF SAR RETRACKING TECHNIQUES TO CRYOSAT-2 DATA OVER WEST IBERIAN COAST AND TYRRHENIAN SEA

摘要

In the context of the ESA-funded Research &rnDevelopment project SAMOSA, a novel analytic modelrnfor mean return power of the radar altimeter echo inrnSAR mode has been developed.rnIn parallel the ESA/ESRIN Research and DevelopmentrnData Exploitation Team has developed an alternativernand independent numerical solution for SAR waveformrnmodelling. This was done essentially for the purposes ofrnthe SAMOSA model validation on ESA side forrnacceptance of the SAMOSA contract deliverables.rnSuch altimeter echo waveform retracking techniquesrnhave been devised, mainly, with the purpose of itsrnapplication in the Sentinel-3 (S-3) Ground Segmentrn(PDGS), where the SAR oceanographic products arerndestined to become operational over the oceanic coastalrnzone.rnIn the scope of quality assessment of CryoSat-2 SARrnoceanographic products, the afore-mentioned SARrnRetracking techniques have been applied over openrnocean regions.rnThe application region is twofold: an internal basin, asrnthe Tyrrhenian Sea, where moderately calm searnconditions are expected and an open ocean stretch offrnthe Western Iberian Coast where high ocean waves arernencountered, in order to assess the techniques over thernfull sea-state spectrum.rnParticular attention has been dedicated to the validationrnprocess of the results. That shall be accomplished with arncomparison of the sea state obtained from multi-missionrngrid maps in the analyzed regions at the observationrntime or with a novel and more original approach: usingrnthe SAR L1b products originate from the CryoSat-2 FullrnBit Rate (FBR) data; these can be reduced to LRMequivalentrnlevel (also known as pseudo-LRM in thernSAMOSA jargon) and retracked by means ofrnconventional altimetry retracking schemes; afterwards,rnsuch results will be compared with the results comingrnfrom L1b SAR data.rnThe results from SAR L1b are expected to match orrntheoretically over-perform the pseudo-LRM outcomes.rnThis shall allow even to quantify the benefits of thernSAR altimetry with respect the pulsewidth-limitedrnaltimetry.