Correction to: Radiometric Calibration Targets for the Mastcam-Z Camera on the Mars 2020 Rover Mission

Abstract

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The Mastcam‐Z Radiometric Calibration Targets on NASA's Perseverance Rover: Derived Irradiance Time‐Series, Dust Deposition, and Performance Over the First 350 Sols on Mars

“…As studied by Buz et al (2019) and by Kinch et al (2020) in the pre-flight tests, at the typical emission angle of 58 𝐴𝐴 • all the color and grayscale materials of the cal-targets (though to a lesser extent for the white patches) show a strong forward scattering peak with incidence angles >45°. The smaller number of observations on Mars with the Sun opposite to the camera (high azimuth) reduced the impact of the forward scattering, which in some cases ( 𝐴𝐴 𝐴𝐴≥ 50 • ) was quite significant.…”

“…The Mastcam-Z Calibration Targets (Kinch et al, 2020), or cal-targets, are a pair of physical devices mounted on the Perseverance rover deck (Figure 1) and primarily used to assist in the conversion of Mastcam-Z images from units of radiance to reflectance (I/F). They were designed and assembled at the Niels Bohr Institute of the University of Copenhagen.…”

“…The following equation is used to convert radiance images into IOF (Kinch et al, 2020): 𝐴𝐴 𝐴𝐴𝐴𝐴IOF is the reflectance of the cal-target materials, which is known from laboratory spectra. The ratio between 𝐴𝐴 𝐴𝐴𝐴𝐴IOF and 𝐴𝐴 𝐴𝐴𝐴𝐴RAD in Equation 1 is equal to the inverse of the irradiance 𝐴𝐴 𝐴𝐴 .…”

“…Simultaneously, the corresponding values of reflectance of the clean spots under the same illumination geometry as the observation were computed. These reflectances were known from laboratory measurements of the eight color and grayscale samples at different geometries across the visible and near infrared spectrum (400-2,500 nm), (Buz et al, 2019;Kinch et al, 2020).…”

“…In addition, 12 narrow-band filters (six for each sensor, or "eye") span visible and near-infrared wavelengths from 440 to 1,022 nm. In order to correctly calibrate Mastcam-Z images to units of reflectance, the camera relies on a set of calibration targets (Kinch et al, 2020), or cal-targets, fixed on the deck of the rover. During the first 350 sols on Mars, the cal-targets were the most imaged objects by Mastcam-Z.…”