Solar-radiation-based absolute calibration of optical sensors: SeaWiFS and a Daedalus 1268

The authors have developed a solar-radiation-based calibration method for the radiometric calibration of satellite sensors with a solar diffuser such as that used on SeaWiFS. A similar method using a diffuser at ground level can be used to calibrate airborne sensors such as the Daedalus 1268 sensor operated by EG&G in a helicopter. The atmospheric transmittance is measured while measurements of a solar illuminated diffuser panel are made by the instrument being calibrated. Measurements of the panel are also taken with the direct solar beam blocked. The difference gives the signal due to the attenuated solar beam. The major advantage of this method is that the source for the calibration, the Sun, is the same source used in measurements. Results of calibrations of SeaWiFS and a Daedalus scanner are presented