Intercomparison of sensor calibration techniques for the Advanced Solid State Array Spectroradiometer (ASAS) as a performance validation tool

The Advanced Solid-state Array Spectroradiometer (ASAS), an airborne hyperspectral off-nadir pointable pushbroom imager, has participated in a variety of remote sensing field campaigns and has historically been calibrated using a radiative transfer technique. Recent campaigns have provided several candidate calibration target image sites that can and have been used to validate instrument radiometric performance. Limitations in the sensor's CCD sensitivity and integrating sphere source existence provide a less than satisfactory calibration in the blue and near-IR wavelength bands and a vicarious calibration of these bands is under consideration. This paper will compare 'at sensor radiance' retrieved from a target of known spectral radiance using detector gains derived from laboratory calibration to radiances retrieved using detector gains derived from a well characterized ground calibration site. Physical reasons for the discrepancies and problems will be offered and discussed along with arguments for a combined vicarious and laboratory radiative transfer calibration.