抄録
The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) launched in December 1999, is a high-spatial-resolution multispectral imager with 14 bands from the visible and near-infrared (VNIR) to the thermal infrared (TIR) regions. In the present paper, the brightness temperatures at five TIR bands derived from the onboard calibration (OBC) are verified based on two vicarious calibration (VC) experiments at Lake Kasumigaura, Japan, on 16 May 2000 and 16 March 2001. In each experiment, the bulk and skin temperatures of a selected area on the lake were measured at the satellite overpass time, and the atmospheric profiles for pressure, temperature, andmoisture were also measured by two radiosondes launched before and after that time. These parameters are used for radiative transfer computations using MODTRAN 3.7, and then the top of the atmosphere (TOA) brightness temperature and its error bar are predicted for each band. On the other hand, the ASTER data for the both experiments are calibrated using the radiometric calibration coefficients (RCCs) of version 1.02 that apply the gain coefficients determined from the long-term calibration on 12 March 2000. As a result, the difference of the TOA brightness temperature between OBC and VC shows to be within 0.6 K for all bands in the both experiments. This allows us to estimate that the RCCs of version 1.02 satisfy the absolute-temperature-accuracy requirement (within 1 K for the range from 270 to 340 K) for the ASTER data used.
