Publication Date:
2015-04-01
Description:
The Panoramic Cameras on NASA's Mars Exploration Rovers have each returned more than 17000 images of their calibration targets. In order to make optimal use of this dataset for reflectance calibration, a correction must be made for the presence of airfall dust. Here we present an improved dust correction procedure based on a two-layer scattering model and we present a dust reflectance spectrum derived from long-term trends in the dataset. The dust on the calibration targets appears brighter than dusty areas of the Martian surface. We derive detailed histories of dust deposition and removal revealing two distinct environments: At the Spirit landing site half the year is dominated by dust deposition, the other half by dust removal, usually in brief, sharp events. At the Opportunity landing site the Martian year has a semiannual dust cycle with dust removal happening gradually throughout two removal seasons each year. The highest observed optical depth of settled dust on the calibration target is 1.5 on Spirit and 1.1 on Opportunity (at 601 nm). We derive a general prediction for dust deposition rates of 0.004 +/− 0.001 in units of surface optical depth deposited per sol per unit atmospheric optical depth. We expect this procedure to lead to improved reflectance-calibration of the Panoramic Camera dataset. In addition it is easily adapted to similar datasets from other missions in order to deliver improved reflectance calibration as well as data on dust reflectance properties and deposition and removal history.
Electronic ISSN:
2333-5084
Topics:
Geosciences
,
Physics
Permalink
