SMAP (Soil Moisture Active Passive) is created to measure soil moisture every 2-3 days over a three-year period. This permmision changes around the world. It's necesarry to observe over time scales ranging from major storms and repeat measurements of changes over the seasons. SMAP measures how much water is in the top layer of soil, if the ground is frozen, if not it measures amount of water between rocks, organic particles and minerals. Using SMAP is impossible to measure the ice.