DOMEX 2004: an experimental campaign at Dome-C Antarctica for the calibration of space-borne low-frequency microwave radiometers G. Macelloni (1) , P. Pampaloni (1) , M. Brogioni (1) , A. Cagnati (3) , M. Drinkwater (2) (1) IFAC-CNR Via Panciatichi 64 – 50127 Firenze, Italy Email:G.Macelloni@ifac.cnr.it (2) ESA- ESTEC Postbus 299, 2200 AG Noordwijk, The Netherlands Email: Mark.Drinkwater@esa.int (3) CVA-ARABBAVia Pradat n. 5, 32020 Arabba di Livinallongo (BL) Italy Email: acagnati@arpa.veneto.it Abstract Satellite data are the most suitable tools for monitoring time and spatial variations of snow covered areas. At present, our knowledge of the microwave emission from the ice sheet at the lower frequencies is limited by the lack of satellite sensors and by our inadequate knowledge of the physical effects governing emission. On other hand, in addition to the interest related to climatic changes, and to glaciological and hydrological applications, there is growing interest, on the part of the remote sensing community, in using the Antarctic area, and in particular the plateau where the DOME-C base is located, for calibrating and validating data of satellite-borne microwave and optical radiometers. This is because the size, structure, spatial homogeneity and thermal stability of this area. With a view to the launching of the new low frequency space-borne sensor an experiment was carried out at Dome-C under support of ESA. In this paper, the preparatory activities, the experimental campaign in Antarctica and the results obtained are presented. Keywords: SMOS, Microwave Radiometer, Antarctic. 1. INTRODUCTION Antarctica is one of the most interesting and challenging natural laboratories on Earth, and plays a fundamental role in hydrological and meteorological cycles. Because of its high albedo, high thermal emissivity, and low thermal conductivity, snow strongly influences the overlying atmosphere and thus, the polar and global climate. Satellite data are one of the most suitable tools for monitoring the temporal and spatial variations in extensive snow-covered areas. Moreover, the quality of these data is a key issue that can be dealt only with the pre-launch calibration of the instruments, together with a comprehensive follow-up of post-launch calibration and validation experiments, which can be performed with extremely stable natural targets. For example, a method for calibrating space-borne radiometers by using the Ocean surface as cold reference target was indicated in [1]. On the other hand, compared to many other natural scenarios, the Antarctic plateau, appears to be particularly suited to this purpose, thanks to its size, structure, spatial homogeneity and thermal stability. Microwave data of this region at frequencies ranging from 6.8 GHz up to about 90 GHz have been and are still being collected by means of the SMMR, SSM/I and AMSR-E satellite sensors and the results have been reported in several papers ([2]-[5]). However, a significant lack of information exists at the lower frequencies, which are the most interesting for investigating deeper layers of ice. For this reason, and in view of the launching of L- band space-borne radiometers (i.e. SMOS, Hydros, Aquarious), an experiment for measuring emission at C- and L bands was planned for the 2004/2005 Austral summer. The experiment, which was supported by ESA within the framework of the SMOS programme and by the Italian National Project in Antarctica, included radiometric measurements from a tower at different incidence and azimuth angles and snow measurements, using conventional methods