Identifying Thermal Properties of Ground Surface Derived by SAR and Laboratory Measurements

The Synthetic Aperture Radar (SAR) data provide great potential for ground surface mapping under canopy vegetation. The SAR observations regardless time and atmospheric condition are superior for mapping under torrid zones such as Indonesia. The ground surface parameters including surface roughness, moisture, and dielectric constant could be derived by SAR backscattering data. However, estimating thermal properties of ground surface based on SAR remote sensing is complicated because of sensor operation in microwave region. Meanwhile, the thermal properties of ground surface are crucial for estimating surface temperature originated from natural or anthropogenic sources such volcanic activity, urban area, forest fire, or steam spots. To identify the thermal signature from the SAR data, we performed laboratory experiments by incorporating thermal property of materials to be derived from SAR parameters. The experiments were performed by heating ground surface materials including altered rocks from geothermal field and peats from dense vegetation field. We measured moisture, electric potential, magnetic susceptibility, and permeability of the samples with variation of temperature. The measured temperature was controlled by thermal camera FLIR C2 and ground thermometer FLUKE 52 up to 250°C. According to the measurement, we identified that the moisture and electric potential of materials are decrease significantly at temperature more than 100°C. An interesting phenomenon could be reported that the magnetic susceptibility and permeability response to the altered rock and peat samples temperature similarly. The increasing temperature leads to decrease magnetic susceptibility and permeability in general. The mineral and organic content of the rocks and peats controlled their magnetic properties. The laboratory measurement results were then compared to the magnetic permeability derived-SAR backscattering data at a steam field of geothermal system.