01 Nov 2023
 | 01 Nov 2023
Status: this preprint is open for discussion and under review for Atmospheric Measurement Techniques (AMT).

Polarization upgrade of specMACS: calibration and characterization of the 2D RGB polarization resolving cameras

Anna Weber, Tobias Kölling, Veronika Pörtge, Andreas Baumgartner, Clemens Rammeloo, Tobias Zinner, and Bernhard Mayer

Abstract. The spectrometer of the Munich Aerosol Cloud Scanner (specMACS) is a high spatial resolution hyperspectral and polarized imaging system. It is operated in a nadir-looking perspective aboard the German High Altitude and LOng range research aircraft (HALO) and is mainly used for the remote sensing of clouds. In 2019, its two hyperspectral line-cameras which are sensitive to the wavelength range between 400 and 2500 nm were complemented by two 2D RGB polarization resolving cameras. The polarization resolving cameras have a large field of view and allow for multi-angle polarimetric imaging with high angular and spatial resolution. This paper introduces the polarization resolving cameras and provides a full characterization and calibration of them. We performed a geometric calibration and georeferencing of the two cameras. In addition, a radiometric calibration using laboratory calibration measurements was carried out. The radiometric calibration includes the characterization of dark signal, linearity, and noise as well as the measurement of the spectral response functions, a polarization calibration, vignetting correction, and absolute radiometric calibration. With the calibration, georeferenced absolute calibrated Stokes vectors rotated into the scattering plane can be computed from raw data. We validated the calibration results by comparing observations of the sunglint, which is a known target, with radiative transfer simulations of the sunglint.

Anna Weber et al.

Status: open (until 06 Dec 2023)

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Anna Weber et al.

Anna Weber et al.


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Short summary
In this work, we introduce the 2D RGB polarization resolving cameras of the airborne hyperspectral and polarized imaging system specMACS. A full characterization and calibration of the cameras including a geometric calibration as well as a radiometric characterization is provided allowing for the computation of absolute calibrated, georeferenced Stokes vectors rotated into the scattering plane. We validate the calibration by comparing sunglint measurements to radiative transfer simulations.