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The Concordiasi campaign aimed to improve satellite data assimilation at high latitudes and, particularly, the assimilation of the Infrared Atmospheric Sounding Interferometer (IASI) radiances over Antarctica. This study focuses on the IASI data retrieval using a 1-D variational data assimilation system, which was carried out at the Concordia station and within the framework of Concordiasi. The study period lasted from November 20 to December 12, 2009. Radiosonde measurements are utilized to validate temperature and water vapor retrieved profiles. Baseline Surface Radiation Network data and manned measurements in Concordia are used to verify skin temperature retrievals and derive information about cloudy conditions. This study assesses the impact of several parameters on the retrieved profile quality. In particular, the background error specification is crucial. The background error covariance matrix is optimally tuned to provide the best possible retrievals, modifying the shape of these covariances for stratospheric temperatures, computing and maximizing the degree of freedom for signal (DFS). The DFS characterizes how the assimilation system uses the observation to pull the signal from the background. For the study period, the humidity and temperature retrieved profiles are optimally improved compared with background profiles, with the largest reduction in error for the skin temperature.