Radiometric cross comparison of eMAS, AirMSPI, and AVIRIS sensors over Railroad Valley

Remote sensing instruments, both aircraft and on-orbit platforms, undergo extensive laboratory calibrations to determine their geometric, spectral, and radiometric responses. Further validation of the latter is frequently made using in-flight Earth observations and sensor cross comparisons. The FIREX-AQ campaign provided such an opportunity when the ER-2 aircraft overflew Railroad Valley on 13 and 15 August 2019. This allowed the instruments to conduct a vicarious calibration, where surface observations are used to compute the at-sensor radiances. The laboratory and vicarious calibrations of the Enhanced MODIS Airborne Simulator (eMAS), the Airborne Multiangle SpectroPolarimetric Imager (AirMSPI), and the “Classic” Airborne Visible/Infrared Imaging Spectrometer (AVIRIS-C) sensors are presented here. Radiometric differences in their vicarious calibrations have been attributed to differences in the input solar spectral irradiance models, and surface reflectance datasets. Agreement is within the required 5 % uncertainty for the visible bands, but differences on the order of 10 % are shown for the SWIR bands, due to differences in these inputs.