Presented at the 2014 International Geoscience and Remote Sensing SymposiumA 350 Ã 350 km area near the Concordia station on the high plateau of Dome C in Antarctica has been mapped by an airborne L-band radiometer system. The area was expected to display a rather uniform brightness temperature close to the yearly mean temperature - well suited for calibration checks for spaceborne instruments like SMOS, Aquarius, and SMAP. The measured brightness temperatures shows unexpected variations like 8 K variation on an East-West profile through Concordia, and in certain cases a slope of almost 1 K per km. Comparing the measured brightness temperature map with bottom topography reveals a convincing correlation. Simulations show that variations in bedrock topography can indeed modulate the brightness temperature appropriately to explain the observed variations.