Dust particle size and optical depth on Mars retrieved by the MSL Navigation Cameras. (arXiv:1905.01073v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Chen_Chen_H/0/1/0/all/0/1">H. Chen-Chen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Perez_Hoyos_S/0/1/0/all/0/1">S. Perez-Hoyos</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sanchez_Lavega_A/0/1/0/all/0/1">A. Sanchez-Lavega</a>

In this paper we show that Sun-viewing images obtained by the Mars Science
Laboratory (MSL) Navigation Cameras (Navcam) can be used for retrieving the
dust optical depth and constrain the aerosol physical properties at Gale Crater
by evaluating the sky brightness as a function of the scattering angle. We have
used 65 Sun-pointing images covering a period of almost three Martian years,
from MSL mission sol 21 to sol 1646 (MY 31 to 33). Radiometric calibration and
geometric reduction were performed on MSL Navcam raw image data records to
provide the observed sky radiance as a function of the scattering angle for the
near-Sun region (scattering angle from 4{deg} to 30{deg}). These curves were
fitted with a multiple scattering radiative transfer model for a plane-parallel
Martian atmosphere model using the discrete ordinates method. Modelled sky
brightness curves were generated as a function of two parameters: the aerosol
particle size distribution effective radius and the dust column optical depth
at the surface. A retrieval scheme was implemented for deriving the parameters
that generated the best fitting curve under a least-square error criterion. The
obtained results present a good agreement with previous work, showing the
seasonal dependence of both dust column optical depth and the effectiveparticle
radius.

In this paper we show that Sun-viewing images obtained by the Mars Science
Laboratory (MSL) Navigation Cameras (Navcam) can be used for retrieving the
dust optical depth and constrain the aerosol physical properties at Gale Crater
by evaluating the sky brightness as a function of the scattering angle. We have
used 65 Sun-pointing images covering a period of almost three Martian years,
from MSL mission sol 21 to sol 1646 (MY 31 to 33). Radiometric calibration and
geometric reduction were performed on MSL Navcam raw image data records to
provide the observed sky radiance as a function of the scattering angle for the
near-Sun region (scattering angle from 4{deg} to 30{deg}). These curves were
fitted with a multiple scattering radiative transfer model for a plane-parallel
Martian atmosphere model using the discrete ordinates method. Modelled sky
brightness curves were generated as a function of two parameters: the aerosol
particle size distribution effective radius and the dust column optical depth
at the surface. A retrieval scheme was implemented for deriving the parameters
that generated the best fitting curve under a least-square error criterion. The
obtained results present a good agreement with previous work, showing the
seasonal dependence of both dust column optical depth and the effectiveparticle
radius.

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