Abstract
The calibration standard of the spectral radiance that provides the reflected radiance on the standard panel derived from the standard lamp is easy to use and maintain for field radiometer users. The reflected radiance of this calibration standard is, however, not directly calibrated by a blackbody but calculated from the bi-directional reflectance factor of the standard panel and the irradiance of the standard lamp with regulated DC power supply. Thus, the reflected radiance of the calibration standard may not always have enough accuracy for the radiometric calibration of field radiometer, even if the standard lamp and the standard panel are well calibrated. The validations for the reflected radiance of the calibration standard were therefore conducted by the National Space Development Agency of Japan (NASDA) calibration standard, which has been directly calibrated by the blackbody, and by the solar-based calibration method at Ivanpah Playa and Railroad Valley, NV, USA. Since, these validations showed large difference in reflected radiance, the practical calibration standard of spectral radiance was obtained only for practical use of field radiometer calibration by calculating the reflected radiance of this calibration standard from the NASDA calibration standard. After the calibration, field radiometers from seven organizations were calibrated by measuring the common radiance of this practical calibration standard.
