Airborne Multiangle SpectroPolarimeteric Imager (AirMSPI): Calibration and Comparison with Collocated Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) Data
Tuesday, 16 December 2014
The Airborne Multiangle SpectroPolarimetric Imager (AirMSPI) is a pushbroom multiangle spectropolarimetric camera with spectral bands near 355, 380, 445, 470, 555, 660, 865, and 935 nm. Flying on NASAs's high-altitude ER-2 aircraft since 2010, AirMSPI uses dual photoelastic modulator (PEM)-based technology to provide accurate measurements of the Stokes linear polarization parameters Q and U in the 470, 660, and 865 nm bands, providing unique observing capabilities for aerosol, cloud, and surface studies. We describe the methodologies used for radiometric and polarimetric calibration and characterization of the AirMSPI instrument, which make use of a combination of laboratory and vicarious techniques. A 1.65 m integrating sphere and overflights of Ivanpah Playa, NV are used for radiometric calibration. Radiometric cross-comparisons with the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS), also flying on the ER-2, are used to validate the radiometric scale. For polarimetric calibration, a well-calibrated Polarization State Generator is used to provide known polarimetric inputs. A high-extinction rotating wiregrid polarizer is used to derive polarimetric calibration coefficients for each pixel, and the results are then validated using partially polarized light generated using tilted glass plates. Examples of collocated multiangular, polarimetric imagery from AirMSPI and hyperspectral imagery from AVIRIS will be shown, presenting new opportunities for atmosphere and surface remote sensing.