Arctic sea ice has undergone drastic change in recent years, emphasizing the critical role of satellite remote sensing to monitor Arctic change with a frequent coverage over large regions. Optical and multispectral sensors require clear sky and sufficient solar lighting. Microwave radiometers measure ice concentration, the fraction of ice-covered area over the total area, but cannot accurately detect different sea-ice classes. The satellite scatterometer, defined as a stable and accurate radar, is emerging as a versatile sensor for Earth observations and providing new capabilities for sea-ice classification and melt detection regardless of cloud cover and darkness.