Temperature and emissivity separation from calibrated data of the Digital Airborne Imaging Spectrometer

The Digital Airborne Imaging Spectrometer (DAIS), with six thermal infrared channels in the 8–14 μm window, was flown over the Barrax test site, Spain, in the framework of the DAIS Experiment in the summer of 1998. Atmospheric correction of the DAIS thermal channels was performed by means of local radiosonde measurements and a radiative transfer model. Ground measurements of temperature and emissivity for six selected spots (two bare soils, two water bodies, and two vegetated fields) were conducted with the objective of providing calibration and validation targets. Three targets were used for a linear ground calibration of the DAIS thermal channels. With the ground-calibrated images, surface temperatures and channel emissivities were retrieved using a temperature–emissivity separation algorithm. We applied the Adjusted Normalized Emissivity Method (ANEM) in which an initial maximum emissivity was assumed for each surface type according to ground emissivity measurements. The other three targets were used to test the accuracy of the ground calibration and the ANEM method. The derived temperatures and channel emissivities were mostly within ±0.005 and ±1°C of the measured values, respectively. Such results are comparable to other methods for temperature and emissivity separation.