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29 January 2002 Vicarious calibration and validation in the thermal region
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A vicarious calibration was performed for the thermal channels of the airborne DAIS imaging spectrometer during ESA campaigns in Barrax (Spain) in 1998, 1999 and 2000. Ground measurements of temperature were collected in different fields coincidentally with the flights to provide calibration and validation targets for the thermal channels of DAIS. Two calibration targets were selected (water and bare soil) to cover the range of expected surface temperatures in the area. Targets were very homogeneous thus facilitating the acquisition of ground measurements comparable to the remote measurements of DAIS. The derived two-point, linear calibration equations operate on at-sensor radiances and are used to obtain calibrated DAIS data from the original data. Calibrated at-sensor radiances were validated using ground measurements for several fields (other than those used for the calibration). For the present study the validation was made for the two flight lines of June 3, 1999. The comparison of DAIS-derived and ground- measured values was made in terms of both the surface temperature and emissivity. For the processing of the DAIS data, an adjusted normalized emissivity method was used where the input emissivities were selected for each surface according to the field measurements. With this procedure we could derive the six channel emissivities plus the surface temperature for each target. The accuracy of these estimates depends on the selected input emissivity and notably on the atmospheric correction of the DAIS thermal channels. For the Barrax site, the atmospheric correction was calculated with local radiosonde measurements and the MODTRAN 4 code. The results of the validation indicate that surface temperatures and channel emissivities could agree with ground measurements within +/- 1 degree(s)C and +/- 0.01 respectively.
© (2002) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Rudolf Richter, Cesar Coll, Vicent Caselles, E. Rubio, and E. Valor "Vicarious calibration and validation in the thermal region", Proc. SPIE 4538, Optics in Atmospheric Propagation and Adaptive Systems IV, (29 January 2002);

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