Sea level change is strongly linked to the state of the polar ice sheets. Hence, an evaluation of sea level change is only possible if the processes that influence ice sheet mass balance are sufficiently well-known. On global to regional scales, climate models are valuable tools to investigate ice sheet evolution. Locally, field measurements provide data for the validation of model results. However, ground truth measurements are sparse due to the harsh environmental conditions and high logistical effort associated with field campaigns in polar regions. Spaceborne sensors operating in the microwave frequency region are independent of solar radiation and cloud cover and are hence well-suited to observe the polar regions on intermediate spatial scales. The interaction between polar firn and microwave radiation is influenced by a large variety of physical properties of the firn and is a complex process. As a consequence, great care needs to be taken when interpreting satellite data. In our present work, we use firn microstructure measurements and microwave data to examine the interaction between microstructure and microwave radiation. We will investigate the impact of microstructure variability on the microwave signal. In this way, we will improve the accuracy of snow accumulation rate estimates, which constitute the gain term in the mass balance of the polar ice sheets.