Intercomparison of laboratory radiance calibration standards

Several standards for radiometric calibration were measured repeatedly with a spectroradiometer in order to understand how they compared in accuracy and stability. The tested radiance standards included a NIST 1000 W bulb and Spectralon panel, two calibrated and stabilized integrating spheres, and a cavity blackbody. Results indicate good agreement between the blackbody and 1000 W bulb/Spectralon panel. If these two radiance sources are assumed to be correct, then the integrating spheres did not conform to their manufacturer-reported radiances in several regions of the spectrum. More measurements are underway to investigate the discrepancy. INTRODUCTION The radiometric calibration of AVIRIS (Airborne Visible/InfraRed Imaging Spectrometer) is a process which is constantly being refined. For the past several years, an Optronics 1000 W NISTtraceable bulb and 12 in. Labsphere Spectralon panel (Figure 1) have been used to provide a radiometric standard for laboratory and runway calibrations of the instrument (Chrien et al., 1995). As specified by NIST, the lamp is positioned 50 cm from the panel.