Mars Reconnaissance Orbiter's Mars Color Imager (MARCI): A New Workflow for Processing Its Image Data

Abstract

Earth-based monitoring of Mars has a long history, with researchers searching for any changes to its fuzzy, rusty colored disk. Viking Orbiter 1 and 2 presented the first orbital monitoring, orbiting Mars for a few years and providing well resolved observations of changing ice and frost, weather patterns, and other features not visible from Earth-based observatories. A gap in coverage lasted more than 20 years, and NASA returned to Mars in 1997, with the Mars Global Surveyor (MGS). MGS lived up to its name and provided the first in a series of globe-spanning observations from different spacecraft that, to this day, provide better-than-daily coverage of Mars from aerocentric orbits.Aboard MGS was the Mars Orbiter Camera, and its wide-angle camera (MOC-WA; Malin et al., 1991) in high spatial summing modes allowed it to take blue and red images of swaths of Mars with a cadence slightly better than every two hours. Those swaths built a nearly global view, every Mars day, at an approximately consistent time (early afternoon) and consistent pixel scales of ∼6.5 km/pix. Four years after MGS's science mission began, ESA's Mars Express (MEx) arrived, providing images with its engineering VIsual monitoring Camera (VIC; Ormston et al., 2011;Sánchez-Lavega et al., 2018) and science High-Resolution Stereo Camera (HRSC;Jaumann et al., 2007). VIC is a low-resolution RGB (red-green-blue) camera and takes images at apoapsis, and HRSC is a blue, green, far-red, and near-IR (∼1 μm) camera. ISRO's Mars Orbiter Mission (MOM) has the Mars Color Camera (MCC; Arya et al., 2015), an RGB camera similar to VIC which, can take full-disk images at apoapsis,

Mars Global Surveyor's Mars Orbiter Camera (MOC) Wide‐Angle Images (1999–2006): 2. Data Investigation Into North Polar Hood Formation, Broad Brightness Changes in Acidalia, and Seasonal Frost in Hellas

“…The MOC‐WA global map data set is not widely used today. It is hoped that this work, demonstrating MOC‐WA's utility for new analyses, and the companion work (Robbins, 2023a) that discusses the data processing, will show that useful information can still be gleaned from these older generation data. Combined with MARCI, they present an almost uninterrupted view of Mars from orbit spanning 1999 through the present day, nearly a quarter‐century.…”

“…The companion work to this (Robbins, 2023a) presents details of a thorough reprocessing of the MOC‐WA image data for those images in spatial summing modes 8, 10, 13, and 27 that returned approximately pole‐to‐pole‐spanning views (spatial summing modes are effectively on‐craft binning of the data). In that work, the data were processed with an average photometric correction, had additional empirical flat‐fields applied, and were rendered at 9 pix/deg (≈6,586 m/pix at the center of the projection).…”

“…(2006); this is by no means an exhaustive list, it is meant to show several examples of use of the temporal nature of this data set. Thus, there does exist a sizable body of work that has used the global map data, though no work that is publicly available processed the complete data set as in the Robbins (2023a) companion work, and extremely few peer‐reviewed papers make use of the entire, global map, color time series.…”

Mars Global Surveyor’s Mars Orbiter Camera (MOC) Wide‐Angle Images (1999–2006): 1. Data Processing

“…Due to the several weeks of overlap (Figure 1), MARCI can be used as a direct comparison with MOC‐WA. Therefore, MARCI data were obtained for Mars Year 28 for L s = 105–121.8°, two average mosaics were constructed following a similar procedure (Robbins, 2022), and three‐color RGB composites using indigo, green, and orange/yellow were made (red MARCI data were not taken during this period). The comparisons are shown in Figure 2, which shows good agreement between MOC‐WA and MARCI, and it illustrates the superior sharpness of MARCI even at the reduced pixel scale for a journal article.…”