P23B-2140
UV Opacity at Gale Crater from MSL/REMS Measurements

Tuesday, 15 December 2015
Poster Hall (Moscone South)
Álvaro Vicente-Retortillo1, German Martinez2, Nilton O Renno2, Mark T Lemmon3, Emily L Mason4 and Manuel de la Torre-Juárez5, (1)Complutense University of Madrid, Madrid, Spain, (2)University of Michigan Ann Arbor, Ann Arbor, MI, United States, (3)Texas A & M University, College Station, TX, United States, (4)Texas A & M University College Station, College Station, TX, United States, (5)Jet Propulsion Laboratory, Pasadena, CA, United States
Abstract:
We use the UV photodiode output currents (TELRDR products) measured by the REMS Ultraviolet Sensor to calculate UV opacities at Gale crater during the first 804 sols of the MSL mission. We propose a novel technique to calculate the atmospheric opacity that is not sensitive to the degradation of the sensor due to the deposition of dust on it. We estimate the diffuse and total radiation signals by analyzing the events in which the direct solar beam was temporarily blocked by the masthead or by the mast of the rover. Then we use a radiative transfer model based on the Monte-Carlo method to obtain the UV opacity from those measurements.

We compare the UV opacities with the opacities derived from Mastcam observations at 880 nm. Both opacities follow a similar seasonal trend, with the UV opacity showing values generally lower than those at 880 nm. The difference between both opacities varies over the year, with the minimum difference occurring when both opacities show their annual lowest values (Ls ~ 130º). The temporal variation of this difference may be attributed to changes in the dust size distribution.

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