Temperature and emissivity extracted from airborne multi-channel data in the ReSeDA experiment

Surface temperatures and emissivities were recovered from thermal infrared data of the Digital Airborne Imaging Spectrometer (DAIS) acquired over the ReSeDA site. Pre-processing of the DAIS thermal data included ground calibration using in situ measurements in two reference fields and atmospheric correction with nearby atmospheric radiosonde data. An adjusted normalised emissivity method was used, with the initial emissivity selected for each surface according to local measurements. Results were compared with ground measurements for several validation fields. The same comparison was made for the non-calibrated DAIS data. In all cases, the re-calibrated data yielded more reasonable results, showing the need for calibration measurements for the DAIS thermal channels. For the re-calibrated data, the retrieved temperatures were in good agreement with ground data. Some disagreement was found for the emissivities, with spectral variations not expected from the ground measurements. Such discrepancies could be due to errors still present in the re-calibration procedure and sensor stability.