Xavier Domingo (isardSAT, Spain); Mònica Roca (isardSAT, Spain); Pablo Garcia (isardSAT, Spain)

The calibration of the radiometer must be carried out measuring ground targets of known brightness temperature. Such targets are required to be radiometrically homogeneous in space over areas many times larger than the radiometer footprint and also over time. In this way, several areas have been identified as suitable for the instrument calibration: the Dome C in Antarctica or the Amazon forest, the proposed team has already performed radiometer brightness temperature (AMRS-E and SMOS) monitoring over the Salar de Uyuni (in the framework of the ESA SMOS Cal/Val Announcement of Opportunities ID 6317). Here we propose to monitor brightness temperature and sigma-0 over the Etosha Salt pan (18°47′07″S 16°15′50″E) in Namibia. The Etosha salt pan, similarly to the Salar de Uyuni, is a large, flat and radiometrically homogeneous area. Its extent is around 4800 km2 (100 x 48 km) and its emissivity is high and rather homogeneous except when flooded (exceptionally after a heavy rain). Therefore it provides a perfect calibration site for the altimeter sigma-0 and the radiometers brightness temperature.
In this work we will present the results from continuous monitoring and cross-validation with instruments measuring at the same frequencies performed during the whole mission duration.
We will also explore synergies between sigma-0 and reflectivity.