The importance of satellite altimetry in monitoring the complex ocean-atmosphere system led to the approval of the
Sentinel-3 ocean topography mission. This mission is scheduled to be launched in 2013. It will incorporate new
instruments and measuring modes that are expected to provide high-accuracy measurements for the determination of sea
level as well as ocean and land color, sea and land surface temperature with improved spatial and temporal coverage.
Nevertheless, satellite altimeter measurements, as in also the case for Sentinel-3, of homogenous quality and reliability
have to be maintained over longer periods of time. Hence, the Sentinel-3 altimetry observations, such as sea-surface
heights and sea-level anomaly fields, need to be continuously and independently connected in a common, reliable but
also long-term manner. This can be achieved by satellite calibration using dedicated research infrastructures. A
permanent calibration facility for satellite altimeters has been operating in Gavdos island, Greece as of 2004. This
facility has already been successfully and continuously determined the OSTM/Jason-2 altimeter bias. This work presents
the plans and actions to be performed to calibrate the altimeter of Sentinel-3, using the existing Gavdos Cal/Val facility,
as well as the newly developed microwave transponder.