Assessing the Sensitivity of the High Resolution Stereo Camera (HRSC) Colour Channels onboard Mars Express for Surface Material Discrimination

Kurzfassung

The High-Resolution Stereo Camera (HRSC) onboard the Mars Express has been capturing multispectral images of Mars since 2004 [1]. In addition to its nadir and stereo-imaging capabilities, HRSC also acquires medium-resolution (~25–100 m/pixel) multispectral data in four colour channels—Blue (444.0 nm), Green (538.0 nm), Red (748.0 nm), and Near-Infrared (955.5 nm)—though not consistently across all observations. Products and mosaics derived from these channels have been widely utilized for surface characterization, particularly in geological mapping, geomorphological analysis, and investigations of seasonal, polar, and atmospheric processes (e.g., [2-4]). Despite its extensive use for morphologic and contextual analysis, HRSC multispectral data have been underutilized for mineralogical discrimination. This is largely due to the availability of more spectrally resolved hyperspectral datasets from OMEGA (also aboard Mars Express) [5] and CRISM on the Mars Reconnaissance Orbiter [6]. However, with CRISM now non-operational and OMEGA currently limited to the VNIR, there is renewed relevance in evaluating the spectral utility of HRSC. This study investigates the spectral sensitivity of HRSC’s colour channels with a goal to determine the theoretical detectability and separability of various mineral types using HRSC, thereby enhancing its value as a bridging dataset between lower-resolution hyperspectral (i.e., OMEGA) and high-resolution instruments like HiRISE [7] and CaSSIS [8].