Dust deposition on the decks of the Mars Exploration Rovers: 10 years of dust dynamics on the Panoramic Camera calibration targets

Abstract

The Panoramic Cameras on NASA's Mars Exploration Rovers have each returned more than 17,000 images of their calibration targets. In order to make optimal use of this data set for reflectance calibration, a correction must be made for the presence of air fall 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 data set. 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 (Martian solar day) per unit atmospheric optical depth. We expect this procedure to lead to improved reflectance‐calibration of the Panoramic Camera data set. In addition, it is easily adapted to similar data sets from other missions in order to deliver improved reflectance calibration as well as data on dust reflectance properties and deposition and removal history.

The Mars Science Laboratory Curiosity rover Mastcam instruments: Preflight and in‐flight calibration, validation, and data archiving

“…The model treats single-scattering events in full detail and uses a two-stream formalism [e.g., Zdunkowski et al, 2007] to treat multiple-scattering events. The dust model and procedure follows very closely the one described in full detail in Kinch et al [2015], the only difference is that we here do not distinguish between diffuse sky irradiance and solar (directional) irradiance; rather, all irradiance is assumed to come from the direction of the Sun. The utility of this model for analysis of dusty caltarget surfaces was demonstrated by Johnson et al [2006] in laboratory studies.…”

“…The utility of this model for analysis of dusty caltarget surfaces was demonstrated by Johnson et al [2006] in laboratory studies. A similar, but simpler, two-stream scattering model is currently used for dust correction on the Mars Exploration Rovers' Pancam [Kinch et al, 2007], but work is ongoing to employ this more sophisticated model on that mission as well [Kinch et al, 2015]. Preliminary work on employing this dust model for the MSL Mastcam was presented in Kinch et al [2013].…”

Climate Forcing of Ripple Migration and Crest Alignment in the Last 400 kyr in Meridiani Planum, Mars

“…However, many aspects of seasonal wind activity may be inferred from other instruments. Pancam images (Bell et al, ) of the rover deck obtained over a period of 5 MY indicated that there was a repeating pattern of dust deposition during late northern winter and early spring, peaking at L s = ~45°, and a slightly less regular peak in deposition during late southern winter and early spring, peaking at L s = ~225° (Kinch et al, ). During the periods leading up to these depositional peaks, winds were weak enough to prevent settled dust from being reentrained.…”

An Instrument Anomaly in the Mars Exploration Rover Pancam 1,009‐nm Filter (R7): Characterization, Simulation, Correction, and Preliminary Verification

“…Several previous works point out anomalies in R7 images relative to other filters of the Pancam system. In a study of dust deposition on the Pancam radiometric calibration target (Kinch et al, ), it was found that derived dust albedo values showed a dramatic upturn at the longest wavelength (Figure 8 and section 4.1.2 of Kinch et al, ). The authors also find that the ratio between direct and diffuse illumination showed a dramatic downturn at the longest wavelength (Figure 10 and section 4.2.2 of Kinch et al, ).…”

“…The authors also find that the ratio between direct and diffuse illumination showed a dramatic downturn at the longest wavelength (Figure 10 and section 4.2.2 of Kinch et al, ). The authors hypothesize that these observations are caused at least partly by an instrumental artifact and mention under “future work” that this issue is in need of further characterization (section 5.4 of Kinch et al, ).…”