| dc.description.abstract | Dust aerosols in the Martian atmosphere play a fundamental role in determining the behavior of atmospheric circulations at all spatial scales and are well-known as a tracer of boundary layer dynamics. Vertical variations in atmospheric dust mixing ratios have recently been detected at Gale Crater, Mars, by the Mars Science Laboratory (MSL) rover, Curiosity, and have been interpreted in terms of the height of the planetary boundary layer (PBL) and local to mesoscale mixing processes. These variations have been observed though the use of a simplified radiative transfer analysis that utilizes Navigation Camera (Navcam) images of distant features to discern the near-surface dust mixing ratio along a defined line-of-sight. However, the simplified methods of radiative transfer established possess substantial weakness within the principal assumptions.
In order to assure that landed spacecraft for both present and future operations possess the robust capability of determining line-of-sight atmospheric optical depth, a three-dimensional radiative transfer model was developed to produce simulated atmospheric data that enabled the simplified methodology for measuring dust content to be evaluated and validated while limiting the number of required free parameters. In this model, the radiative transfer equation (RTE) was integrated over a line-of-sight in an arbitrary atmosphere that is a set of spherical shells and is horizontally homogeneous except for the existence of an idealized crater with allowed in-crater versus out-of-crater differences. The first-order scattering contribution to the RTE was calculated analytically. However, the multiple-scattering contribution was more complex and utilized numerous runs of the Discrete-Ordinate-Method Radiative Transfer (DISORT) numerical algorithm which characterized the diffuse radiation field as a function along the arbitrary Navcam line-of-sight. This work tests the simplified method under a variety of geometries and over the range of relevant wavelengths in order to identify the existence of specified limitations that could alter and/or further develop the previously established observations within Gale Crater. | en |
