Olivier Laurain (OCA/Geoazur, France); Michel Calzas (DT-INSU, France); Christine Drezen (DT-INSU, France); Lionel Fichen (DT-INSU, France); Antoine Guillot (DT-INSU, France); Gérald Dibarboure (CNES, France); Thierry Guinle (CNES, France); Nicolas Picot (CNES, France); Philippe Schaeffer (CLS, France)

Initially developed for monitoring the performance of TOPEX/Poseidon and follow-on Jason legacy satellite altimeters, the Corsica geodetic facilities that are located both at Senetosa Cape and near Ajaccio have been developed to calibrate successive satellite altimeters in an absolute sense. In anticipation of SWOT, a first phase of extension of the reference surfaces of the Corsica site was carried out in June 2021 (378 nautical miles) and the second in May 2022 (508 nautical miles). The measurements were carried out simultaneously using the instruments developed by DT-INSU as part of FOAM project (CalNaGeo and Cyclopée), which showed very good consistency (a few mm on average and ~20 mm standard deviation). GNSS processing using different software (track, MIT, differential mode / GINS, CNES, iPPP mode) and using the GPS and Galileo constellations jointly or separately have been analyzed. The high degree of consistency, both at processing level and at instrumental level, demonstrates the great maturity acquired thanks to the synergy of the FOAM group. We will present in details, the different phases of processing and preliminary results of the resulting reference surface local (“Mean Sea Surface”) covering the SWOT swath of pass #001 (60km along-track and 50km across-track)
Preliminary Calibration and Validation results of both KaRIn and nadir altimeters will be also presented.