Absolute calibration of Sentinel-3A and Jason-3 altimeters with sea-surface and transponder techniques in west Crete, GreeceAbsolute calibration of Sentinel-3A and Jason-3 altimeters with sea-surface and transponder techniques in west Crete, Greece Πλήρης Δημοσίευση σε Συνέδριο Conference Full Paper 2022-07-192018enThis work has been supported and funded by the EU and ESA (ESA Contracts No. 4000117101/16/I/BG and 400122240/17/I-BG). The operational work for Jason-3 transponder Cal/Val has been supported by CNES.This work presents the latest absolute and relative calibrations for the altimeters of the Sentinel-3A and Jason-3 at the Permanent Facility for Altimeter Calibration in west Crete, Greece. Results have been determined at first with the transponder at the CDN1 Cal/Val site on the mountains of west Crete using the ascending Sentinel-3A Pass No. 14 and the descending Jason-3 Pass No.18. Then, sea-surface calibration has been carried out with the descending Sentinel-3A Pass No. 335 and the ascending Jason-3 Pass No.109 based on the Cal/Val facility on Gavdos island. For Sentinel-3A results have been established for cycles 3–27 using Level 2 (Level 0 for transponder) and Non-Time Critical data. For Jason-3, cycles 5–80 and the S-GDR-D data have been worked with the transponder calibration, while for the results with sea-surface calibration, cycles 1–80 with the I-GDR-D data have been implemented. Sentinel-3A produces biases of the order of a few mm either with the transponder (+2.7 mm) or with the sea-surface calibration (7.3 mm and −4.4 mm). The altimeter of Jason-3 presents a range bias at +22.7 mm (No.18) with the transponder and −36.7 mm for the bias in sea-surface height, respectively. Finally, comparison of sea-surface heights observed by Sentinel-3A relative to Jason-3 demonstrates a difference of +4 cm within a period of ±3 days about 20 km south of Gavdos.http://creativecommons.org/licenses/by/4.0/41–47International Review Workshop on Satellite Altimetry Calibration/Validation Activities and ApplicationsFiducial Reference Measurements for Altimetry Mertikas Stylianos Μερτικας Στυλιανος Donlon Craig Femenias Pierre Mavrocordatos Constantin Galanakis Demitris Guinle Thierry Boy Francois Tripolitsiotis Achilleas Τριπολιτσιωτης Αχιλλεας Frantzis Xenofon Φραντζης Ξενοφων Tziavos, Ilias N Vergos, Georgios S Springer Nature Calibration Jason-3 Sea-surface Sentinel-3A Transponder Validation