Comparison of surface reflectance measurements from three ASD FieldSpec FR spectroradiometers and one ASD FieldSpec VNIR spectroradiometer

The Remote Sensing Group (RSG) of the Optical Sciences Center at the University of Arizona uses reflectance-based vicarious calibration techniques that rely on groundbased test sites to calibrate a variety of sensors. This method requires accurate surface reflectance of the test site to be measured at the same time as sensor overflight. Atmospheric measurements are also made to characterize scattering by aerosols and molecules. The results of these ground-based measurements are put into a radiative transfer code to predict the at sensor radiance. The result is compared to the output from the sensor to give the radiometric calibration. To measure the surface reflectance properties of various ground-based test sites, the RSG makes use of Analytical Spectral Devices (ASD) FieldSpec spectroradiometers that cover the 350-2500nm range. The accuracy and repeatability of these instruments are critical to the success of this method because errors in the vicarious calibrations are proportional to errors in the retrieved reflectance. Three different full range (FR) Analytical Spectral Devices and one visible and near infrared (VNIR) Analytical Spectral Device are compared in tests that include those done under well-controlled environmental conditions.