High Resolution Stereo Camera Research Articles

Pixel-level Terrain Processing of the Martian Surface from Moderate Resolution Images of Tianwen-1

The moderate-resolution camera (MoRIC) of the Tianwen-1 orbiter, China’s first Mars exploration mission, is a frame-imaging scheme color camera. However, generating a precise digital elevation model (DEM) from these images faces challenges due to the presence of featureless and repetitive regions on the Martian surface. Traditional photogrammetric methods often struggle to achieve pixel-level resolution in these areas. To address this, we employ a shape from shading (SFS) algorithm that leverages shading patterns to reconstruct fine-scale terrain details, optimizing photogrammetric initial DEM. This paper presents a novel global bisection search algorithm, based on the Pearson correlation coefficient to determine the smoothing parameter, a crucial element in the SFS process. Comparisons with higher-resolution data from the Mars Express high-resolution stereo camera and Mars Reconnaissance Orbiter CTX images validate our approach, highlighting the potential of SFS to significantly enhance the scientific value of Tianwen-1 MoRIC data by generating high-resolution, three-dimensional maps of Mars.

A global colour mosaic of Mars from Mars Express HRSC high altitude observations

The ever-changing transparency of the Martian atmosphere hinders the determination of absolute surface colour from spacecraft images. While individual high-resolution images from low orbit reveal numerous colour details of the geology, the colour variation between images caused by scattering off atmospheric dust can easily be of greater magnitude. The construction of contiguous large-scale mosaics has thus required a strategy to suppress the influence of scattering, often a form of high-pass filtering, which limits their ability to convey colour variation information over distances greater than the dimensions of single images. Here we use a dedicated high altitude observation campaign with the Mars Express High Resolution Stereo Camera (HRSC) (Neukum and Jaumann, 2004; Jaumann et al., 2007), applying a novel iterative method to construct a globally self-consistent colour model. We apply the model to colour-reference a high-altitude mosaic incorporating long-range colour variation information. Using only the relative colour information internal to individual images, the influence of absolute image to image colour changes caused by scattering is minimised, while the model enables colour variations across image boundaries to be self-consistently reconstructed. The resulting mosaic shows a level of colour detail comparable to single images, while maintaining continuity of colour features over much greater distances, thereby increasing the utility of HRSC colour images in the tracing and analysis of martian surface structures.

High-frequency nonlinear vibration analysis through low-frequency stereo-camera systems

This paper describes a new methodology that expands the capabilities of low-frame, high-resolution stereo-camera systems in studying the dynamic behavior of components in the presence of nonlinear phenomena. A new downsampling technique called the Smoothed Harmonics Analysis (SHA) is proposed. This technique addresses the limitations due to the low-frame rate cameras for the study of high-frequency periodic steady-state nonlinear oscillations. SHA enables accurate reconstruction of downsampled signals, thus opening up numerous potential applications. The feasibility of this technique is demonstrated by analyzing the motion of a beam with nonlinear behavior. The nonlinearity is caused by intermittent contact while the beam is subjected to harmonic excitation.

Phobos photometric properties from Mars Express HRSC observations

Aims. This study aims to analyze Phobos’ photometric properties using Mars Express mission observations to support the Martian Moons exploration mission (MMX) devoted to the investigation of the Martian system and to the return of Phobos samples. Methods. We analyzed resolved images of Phobos acquired between 2004 and 2022 by the High Resolution Stereo Camera (HRSC) on board the Mars Express spacecraft at a resolution ranging from ~30 m px−1 to 330 m px−1. We used data acquired with the blue, green, red, and IR filters of HRSC and the panchromatic data of the Super Resolution Channel (SRC). The SRC data are unique because they cover small phase angles (0.2–10°), permitting the investigation of the Phobos opposition effect. We simulated illumination and geometric conditions for the different observations using the Marx Express and the camera spice kernels provided by the HRSC team. We performed photometric analysis using the Hapke model for both integrated and disk-resolved data. Results. The Phobos phase function is characterized by a strong opposition effect due to shadow hiding, with an amplitude and a half-width of the opposition surge of 2.28±0.03 and 0.0573±0.0001, respectively. Overall, the surface of Phobos is dark, with a geometric albedo of 6.8% in the green filter and backscattering. Its single-scattering albedo (SSA) value (7.2% in the green filter) is much higher than what has been found for primitive asteroids and cometary nuclei and is close to the values reported in the literature for Ceres. We also found a surface porosity of 87%, indicating the presence of a thick dust mantle or of fractal aggregates on the top surface. The SSA maps revealed high reflectance variability, with the blue unit area in the northeast Stickney rim being up to 65% brighter than average, while the Stickney floor is among the darkest regions, with reflectance 10 to 20% lower than average. Photometric modeling of the regions of interest selected in the red and blue units indicates that red unit terrains have a stronger opposition effect and a smaller SSA value than the blue ones, but they have similar porosity and backscattering properties. Conclusions. The HRSC data provide a unique investigation of the Phobos phase function and opposition surge, which is valuable information for the MMX observational planning. The Phobos opposition surge, surface porosity, phase integral, and spectral slope are very similar to the values observed for the comet 67P and for Jupiter family comets in general. Based on these similarities, we formulate a hypothesis that the Mars satellites might be the results of a binary or bilobated comet captured by Mars.

Analysis of faults and pit chains in Noctis Labyrinthus: Implications for early extension and possible magmatic plumbing

Noctis Labyrinthus has been a region of disputed origin due to its complexity and poor understanding of how various processes and mechanisms may have combined to form it. The surface is an integrated record of intensive tectonic activity expressed by a multiple extended sets of dip-slip faults oriented in different directions, and thought to have acted on this region over its history. These faults are always coalescent to pits and pit chains displaying a complicated geological history in the region. To understand this geological history, we mapped the surface features in Noctis Labyrinthus using the High-Resolution Stereo Camera (HRSC) onboard Mars Express ND2 nadir channel basemaps, and we adapted the Digital Terrain Map (DTM) from the Mission Experiment Gridded Data Record (MEGDR) of Mars Orbiter Laser Altimeter (MOLA) onboard Mars Global Surveyor (MGS) for the topography. We have investigated the spatial distribution and trend of fault systems, the pit chains' morphology, and the correlation between these two types of features. Our results show three fault systems: i) NS and NNE-SSW, ii) EW and ENE-WSW, and iii) NNW-SSE and NW. The analysis of the faults trending, cross-cutting correlation and the superimposition led to identify multiple intersections between these faults that have been alongside with the reactivations of some inherited faults. We interpreted the first system of fault to be related to coeval lateral extension, generated by regional stress tensor, which is probably related to the slight bending of Valles Marineris within two phases of bidirectional extension. The second system of faults has been generated by the radial oblate stress tensor related to the formation of the small shield volcanoes in Syria Planum. However, the third system is likely related to the external driving process, probably in the Tharsis province. We classified pits in four evolutionary stages based on their morphometric attributes. We believe that the formation of the pit chains in Noctis Labyrinthus is related to a surface collapse after a pressure drop related to the magma chamber deflation associated with Syria Planum volcanic province. We propose a deformational model based on early extension and magmatic plumbing as driving processes for the formation of Noctis Labyrinthus.

A High‐Resolution Digital Terrain Model Mosaic of the Mars 2020 Perseverance Rover Landing Site at Jezero Crater

AbstractWe demonstrate the capabilities of a published MADNet monocular height estimation network in producing a refined digital terrain model (DTM) mosaic at 50 cm/pixel resolution for the Mars 2020 Perseverance rover landing site in Jezero crater on Mars. Our approach utilizes the publicly available Mars 2020 Terrain Relative Navigation (TRN) High‐Resolution Imaging Science Experiment (HiRISE) Digital Terrain Model (DTM) mosaic, which was originally created by the United States Geological Survey (USGS) Astrogeology Science Centre. Our resultant HiRISE MADNet DTM mosaic is strictly matched with the original HiRISE TRN DTM and orthoimage mosaics. These mosaics are themselves co‐aligned with the USGS TRN Context Camera (CTX) based DTM and orthoimage mosaics, as well as the ESA/DLR/FUB (European Space Agency/German Aerospace Center/Free University Berlin) High Resolution Stereo Camera (HRSC) level 5 DTM and orthoimage mosaics. In this paper, we provide a brief description of the technical details, and present both visual and quantitative assessments of the refined MADNet HiRISE Jezero DTM mosaic product. This DTM product is now publicly available at http://dx.doi.org/10.17169/refubium-38359.

Characterization of aqueous alteration and formation of salty exposures at Ius Chasma, Mars

Intriguing outcrops in Ius Chasma provide a window into past aqueous processes in Valles Marineris, Mars. Hydrous sulfate minerals are abundant throughout this region, but one area in Ius Chasma includes phyllosilicates, opal, and additional materials with unusual spectral features. This study at Geryon Montes, an east-west horst that divides Ius Chasma into a northern and southern canyon, exploits recent advances in image calibration and feature extraction techniques for analysis of hyperspectral images acquired by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). Specifically, a unique spectral “doublet” feature with absorptions at 2.21–2.23 and 2.26–2.28 μm is isolated at the border of phyllosilicate-bearing and sulfate-bearing regions in Ius Chasma and surveyed to characterize outcrops that may represent a changing climate on Mars. We document and map three distinct forms of this “doublet” material in relation to phyllosilicates and opal. Analyses of compositional maps derived from CRISM overlain on High Resolution Stereo Camera (HRSC) and High Resolution Imaging Science Experiment (HiRISE) imagery has revealed the presence of these hydrated outcrops along the wall rocks below a breach in the Geryon Montes, bordering a canyon containing abundant hydrated sulfates. Our investigation supports formation of these unique alteration phases through acid alteration of ancient smectites in the wall rock as the sulfate brine overflowed the south canyon of Ius Chasma at the breach in Geryon Montes and penetrated the deeper northern canyon.

Dendritic ridges in Antoniadi basin, Mars: Fluvial or volcanic landforms?

Antoniadi basin displays dark-toned dendritic ridges previously interpreted as inverted fluvial channels. Detailed observations of these dark-toned ridges as well as the geological units in the central region of Antoniadi basin are provided emphasizing images from the Colour and Stereo Surface Imaging System (CaSSIS), the High Resolution Stereo Camera (HRSC) and the High Resolution Imaging Science Experiment (HiRISE) instruments. Results show that the dark-toned ridges are part of the most recent geological unit as they overlie, and thus postdate all plains of the central Antoniadi basin, which is Early Amazonian based on its crater size-frequency distribution. Our observations of the dark-toned ridges are not consistent with inverted fluvial channels: they do not widen in the expected downstream direction, they display a rubbly texture and lack layering at high resolution, and have lobes with local levees in place of channel heads. In addition, the branched ridges are more mafic in composition and display a relatively higher thermal inertia than their surroundings. This suite of characteristics is better explained by volcanic flows developed as distributary channels rather than fluvial tributary channels. The occurrence of dikes in the east and west of the studied region supports that these flows were formed by lava, perhaps a'a like flows as suggested by the rubbly texture, but with an unusually high degree of digitation. Alternatively, such a geometry could be explained by the emplacement of the lava along pre-existing fluvial valleys, but neither the underlying topography, nor two nearby older craters, exhibit signs of fluvial erosion.

The radiometric environment for Mars limb observations by the Mars Sample Return Earth Return Orbiter

After launching from the martian surface via the Mars Ascent Vehicle (MAV), the MAV and the Orbiting Sample (OS) capsule containing the samples collected on Mars by the Perseverance rover are to be identified by the Narrow Angle Camera (NAC) on the Earth Return Orbiter (ERO) spacecraft in order to determine the exact orbit of the capsule before rendezvous. To ensure detection of the OS, noise and straylight contributions to the NAC must be well characterized. Here, we assess the radiometric environment at Mars likely to be encountered by the NAC—from the surface through the middle atmosphere—using the High Resolution Stereo Camera (HRSC) onboard Mars Express (MEx) and the Mars Climate Sounder (MCS) onboard the Mars Reconnaissance Orbiter (MRO). The results show that the radiance values in general tend to increase as phase angle increases, as the season progresses from Ls = 60° to Ls = 230°, and as altitude decreases. We compare HRSC and MCS profiles where observing conditions were similar and find good agreement. At specific latitudes, high-altitude aerosols are present in 1–5% of observations and significantly increase the worst-case radiance contribution above 50 km. We construct envelope profiles from the maximum radiances at 5 km intervals from 0 to 90 km that provide important input for straylight calculations of the NAC and for the validation of models that may be used as input for straylight calculations.

Resolving Ambiguities in SHARAD Data Analysis Using High-Resolution Digital Terrain Models

The SHAllow RADar (SHARAD) onboard Mars Reconnaissance Orbiter (MRO) is a 20 MHz Synthetic Aperture Radar (SAR) that probes the first hundreds of meters of the Martian subsurface. In order to interpret the detection of subsurface interfaces with ground penetrating radars, simulations using Digital Terrain Models (DTM) are necessary. This methodology paper focuses on the analysis of the first tens of meters of the Martian subsurface with SHARAD, comparing the use of different high-resolution DTMs for radar simulation, namely, from the High-Resolution Stereo Camera (HRSC) onboard the Mars Express and from the Context Camera (CTX) onboard MRO. The region of Terra Cimmeria was chosen as a demonstration area. It is a highly cratered southern midlatitude region, where, as will be discussed, the higher resolution of the aforementioned terrain models is mandatory to describe the surface at an acceptable level of detail for shallow subsurface radar interpretation. With a DTM corrected by photoclinometry using CTX imagery, we show that a reflector that was visible on SHARAD data but not on the simulation made with an HRSC DTM is, in fact, a surface echo that was not reproduced by the HRSC surface model. We also show that, unlike laser altimetry DTMs, optical DTMs are prone to artifacts that can make radar analysis more complicated for some scenarios. Reciprocally, we show that the comparison between radar and its corresponding simulated data is a way of assessing a DTM’s quality, which is especially useful in missions where ground control points are lacking, unlike Martian observations.

Assessment of Morphology and Degradation of Craters in and Around Gale Crater, Mars Using High Resolution Stereo Camera (HRSC) Images

Assessment of Morphology and Degradation of Craters in and Around Gale Crater, Mars Using High Resolution Stereo Camera (HRSC) Images

Topographical analysis of a candidate subglacial water region in Ultimi Scopuli, Mars

Radar signals of the MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) instrument at the base of the South Polar Layered Deposits (SPLD) in the region known as Ultimi Scopuli, on Mars, have been interpreted as reflections from putative subglacial standing bodies of liquid water. The interpretation of the MARSIS radar signals is not unique and different explanations have been proposed for the anomalous bright radar reflection observed in Ultimi Scopuli, including the presence of CO2 deposits within the ice, or clays and metal-bearing minerals. We analysed the surface topography of Ultimi Scopuli with Digital Elevations Models (DEMs) derived from MOLA (Mars Orbiter Laser Altimeter), photogrammetric processing of the High-Resolution Stereo Camera (HRSC) images and SHARAD radargrams. In each case, we found an anomalous flat and smooth area in correspondence to the potential subglacial water zone, indicating a condition of hydrostatic equilibrium of the ice, similar to the surface observations found above large terrestrial subglacial lakes. We found that the surface topography, in addition to MARSIS radar sounder signals, are compatible with the presence of subglacial standing bodies of liquid water at the base of Ultimi Scopuli.

Assessing slope uncertainties of martian Digital Elevation Models from numerical propagation of errors on synthetic geological surfaces

Digital Elevation Models (DEM) are widely used in planetary sciences, including for the specific case of Mars. DEMs allow us to extract topography parameters necessary in geomorphological studies. However, DEMs are not free from vertical errors, which yields uncertainties in calculations of parameters such as local slopes. In addition, slope maps computed from DEMs often display slope patterns which are not spatially correlated with the original images. We suspect such slope patterns to originate from DEM vertical errors. To investigate this question, we propose a fully numerical method to provide a quantitative analysis of slope errors based on DEM error propagation using synthetic models. We find that the addition of vertical errors following a normal distribution (random noise) leads to the occurrence of slope patterns comparable to those in observed data. Results are similar for the two models of spatially correlated errors. We also provide estimations of slope errors for four martian cameras: HiRISE (High Resolution Imaging Science Experiment), CaSSIS (Colour and Stereo Surface Imaging System), HRSC (High Resolution Stereo Camera) and MOC (Martian Orbiter Camera). These estimations aim to be used as first order uncertainty constraints on local slopes for geomorphological studies.

Shadow method retrievals of the atmospheric optical depth above Gale crater on Mars using HRSC images

The ‘Shadow Method’ is a tool to estimate the Atmospheric Optical Depth (AOD) on Mars from the brightness of shadows. This method is derived from the equations of radiative transfer, but there are several important simplifications that together invoke errors of several tens of percent. Work by us and by others show that these errors are largely systematic and can be minimized by adding an empirical ‘Correction-Factor’ to the equations. To quantify this factor, we compared shadow method retrievals from orbiter images with in-situ measurements by the Curiosity rover. We analysed a set of seven images that was taken by DLR's High Resolution Stereo Camera (HRSC) on-board ESA's orbiter Mars Express. The images were taken in seven channels: NIR, red, green, blue, and in three panchromatic stereo channels S1, Nadir, and S2. All these images show Gale crater and the exploration site of the Curiosity rover therein. Comparing the rover measurement of the AOD with shadow method retrievals from 5 close-by regions yielded the following correction factors: 0.53 ± 0.03 for Nadir, 0.60 ± 0.04 for S1, 0.62 ± 0.03 for S2, 0.66 ± 0.03 for NIR, 0.64 ± 0.03 for Red, 0.55 ± 0.03 for Green, and 0.57 ± 0.03 for Blue.We analysed 71 regions with varying altitudes between −4.6 km to +3.8 km and found that, on an average, the AOD decreases with increasing altitude. The available channels yielded the following averages of atmospheric optical depth before applying the correction factor: Nadir: 0.47; S1: 0.46; S2: 0.52; Red: 0.49; Green: 0.53; Blue: 0.57 and NIR: 0.44 while after applying the correction factor we obtain Nadir: 0.89; S1: 0.77; S2: 0.84; Red: 0.77; Green: 0.96; Blue: 1.0 and NIR: 0.67. The Curiosity rover, at an altitude of −4.87 km, measured a ground-truth AOD of 0.88.The shadowed and sunlit comparison regions that were used for this work range in altitudes from −4.6 km to +3.8 km. The AOD decreases with altitude and the decrease yields the following scale heights: S1: 12.5 + 0.48/−0.35 km; nadir: 11.1 + 0.53/−0.33 km; S2: 14.3 + 0.48/−0.44 km; NIR: 11.1 + 0.56/−0.47 km; red: 14.3 + 0.52/−0.49 km; green: 15.6 + 0.62/−0.59 km; blue: 14.3 + 0.44/−0.42 km. For this area and around that time of day, the Mars Climate Database predicts a pressure scale height of 11.6–12.2 km, which agrees well with the scale heights that we derived for Nadir, S1 and NIR. One region (number 42) contained a cloud with an optical depth of up to 0.6—0.8; i.e., around one third of the total AOD of 1.9 ± 0.01 measured for this area. Region 29 showed the highest AOD of our sample.

Four-dimensional algorithm for studying geological features on mars using high-resolution stereo camera

In this work is developed a new four-dimensional algorithm for studying geological features on Mars using a high-resolution stereo camera. The 4-D B-spline model has been implemented to reconstruct 4-D geological features such as Mars craters. The B-spline solid algorithm is implemented to simultaneously trace tag craters in sequences of high-resolution stereo camera slices by completely identifying B-spline surfaces which ally themselves with attached pixels. The study shows that B-spline can identify flow patterns from larger craters to the small crater. The Marghany 4-D algorithm of great polygon pattern flows is reconstructed using a 4-D B-spline. In conclusion, integration between the Marghany 4-D B-spline algorithm and the high-resolution stereo camera shows excellent promises for implementing Marghany 4-D algorithm in remote sensing applications.

Machine learning as a tool to classify extra-terrestrial landslides: A dossier from Valles Marineris, Mars

Many researchers studied Martian landslides, and most of these studies are in the Valles Marineris (VM). Those studies are mainly morphologic analysis, estimates of landslide deposit volumes, thermal properties of the landslides, spectral analyses, and mapping and classifying landslides. But, this study created a robust landslide inventory of 682 incidents by collation of data from different sources, apart from our own mapping. This mapping was done for the completeness and accuracy of the landslide inventory. This inventory consists of 141 debris flows, 291 rock avalanches, and 250 slumps. This classification was based on the available literature, and these landslides covered Hebes, Ophir, Candor, Melas, Coprates, Ius and Tithonium chasmas. Landslides were mapped with the aid of images from Mars Reconnaissance Orbiter (MRO) Context Camera (CTX), Mars Orbiter Mission (MOM) Mars Colour Camera (MCC), and high-resolution Google Mars. Digital Elevation Model (DEM) from the Mars Express (MEX) High-Resolution Stereo Camera (HRSC), Thermal Inertia (TI) from Thermal Emission Imaging System (THEMIS), and available geological map were used to define 15 critical parameters of the landslide inventory viz., length (L), width (W), relative relief (RR), area, L/W ratio, RR/L ratio, TI of landslide (mean, minimum, maximum), and slope statistics (mean, minimum, maximum), TI of the scarp, the slope of the scarp, and geology. These 15 parameters were subjected to a multicollinearity testing, which excluded the dependent variable TI (mean). Further, the rest of the variables were analyzed using multiple discriminant analysis (MDA), where the parameters RR/L, L/W, and RR showed higher canonical discriminant function coefficients of 1.245, 0.461 and 0.159, respectively, suggesting that these are the parameters that primarily discriminates the landslides. The classification of landslides was evaluated using a 10-fold cross-validation method using different machine learning algorithms. The five models that provided the best results are simple logistic, logistic regression, meta-classifier, multi-layer perceptron, and Sequential Minimal Optimization (SMO). Of these, simple logistics has the maximum classification accuracy of 81.09%. Thus, this study demonstrates the potential of using machine learning models to classify extra-terrestrial landslides, especially the long-runout landslides that are characteristics of other planets and satellites.

Integrated Photogrammetric and Photoclinometric Processing of Multiple HRSC Images for Pixelwise 3-D Mapping on Mars

Images from the high-resolution stereo camera (HRSC) is an important data source for retrieving 3-D information of the Martian surface. Photogrammetry has been widely applied to HRSC images to generate digital elevation models (DEMs). However, in circumstances of insufficient textures or severe atmospheric influences on Mars, photogrammetry may fail to generate DEMs of favorable quality. Besides, photogrammetry is not able to recover pixelwise geometrical information. Meanwhile, photoclinometry is a promising method to retrieve pixelwise 3-D information from image intensities. Few works in the past have explored the appropriate use of photoclinometry for HRSC data. This article presents an innovative approach of integrating photogrammetry and photoclinometry for pixelwise 3-D mapping of the Martian surface using multiple HRSC images. First, an effective photogrammetric strategy is developed to process multiple HRSC images. For images influenced by haze or aerosol problems, an automatic object-based matching algorithm is formulated to compensate for obvious flaws on the disparity map. Second, multiview photoclinometry considering atmospheric effect is developed to refine the photogrammetric DEM to pixel resolution. Qualitative and quantitative validations are conducted using two representative sets of HRSC images and compared with the reference data. The results show that the generated DEMs have good geometric consistency with the reference data, but offer subtle topographic details conforming to the original images. The proposed method provides a promising solution to exploit the HRSC images for 3-D mapping of the Martian surface with better resolution and coverage, which is of significance for future Mars exploration missions and scientific research.

Generation of Large-Scale Orthophoto Mosaics Using MEX HRSC Images for the Candidate Landing Regions of China’s First Mars Mission

Planetary mapping products play a significant role in landing site selection, surface operations, and scientific investigations. This paper describes the techniques and processes used to create geometrically controlled image mosaics for the candidate landing regions of China’s first Mars exploration mission (i.e., Tianwen-1) using Mars Express (MEX) High-Resolution Stereo Camera (HRSC) images. In order to deal with the extremely complex situations due to large data volumes (hundreds of images), various imaging conditions (e.g., 5–80° incidence angles), and long time spans (>10 years), we developed corresponding methods and in-house software for the photogrammetric processing of MEX HRSC images. According to the characteristics of planetary images and multi-line pushbroom imaging, we optimized the algorithms of establishing control network, eliminating blunders, setting weights and processing abnormal images. The generated MEX HRSC image mosaics with a resolution of 12.5 m delivered a high relative accuracy (<1 pixel). Compared with the existing Mars global image mosaics, the generated image mosaics exhibit significantly better spatial resolution. The techniques and methods that we developed to solve the complicated photogrammetric processing problems can also be applied to produce global or large-scale Mars mapping products using existing and new returned orbital images.

The geography of Oxia Planum

ABSTRACT We present the geography of Oxia Planum, the landing site for the ExoMars 2022 mission. This map provides the planetary science community with a framework to understand this, until recently, unexplored area. The map comprises (1) a mosaic of the panchromatic Context Camera (CTX) Digital Elevation Models (DEM) and Ortho Rectified Images (ORI) controlled to the High Resolution Stereo Camera (HRSC) multiorbit Digital Elevation Models (DEM) and (2) a mosaic of Colour and Stereo Surface Imaging System (CaSSIS) synthetic colour data products, registered to the CTX ORI mosaic. We define a grid of exploration quadrangles (quads) and an informal group of geographic regions to describe Oxia Planum. These regions bridge the scale gap between features observed on large areas (∼100s km2) and the local geography (10s km2) relevant to the Rosalind Franklin rover’s operations in Oxia Planum.

Evaluating Stereo Digital Terrain Model Quality at Mars Rover Landing Sites with HRSC, CTX, and HiRISE Images

We have used high-resolution digital terrain models (DTMs) of two rover landing sites based on mosaicked images from the High-Resolution Imaging Science Experiment (HiRISE) camera as a reference to evaluate DTMs based on High-Resolution Stereo Camera (HRSC) and Context Camera (CTX) images. The Next-Generation Automatic Terrain Extraction (NGATE) matcher in the SOCET SET and GXP® commercial photogrammetric systems produces DTMs with good (small) horizontal resolution but large vertical error. Somewhat surprisingly, results for NGATE are terrain dependent, with poorer resolution and smaller errors on smoother surfaces. Multiple approaches to smoothing the NGATE DTMs give similar tradeoffs between resolution and error; a 5 × 5 lowpass filter is near optimal in terms of both combined resolution-error performance and local slope estimation. Smoothing with an area-based matcher, the standard processing for U.S. Geological Survey planetary DTMs, yields similar errors to the 5 × 5 filter at slightly worse resolution. DTMs from the HRSC team processing pipeline fall within this same trade space but are less sensitive to terrain roughness. DTMs produced with the Ames Stereo Pipeline also fall in this space at resolutions intermediate between NGATE and the team pipeline. Considered individually, resolution and error each varied by approximately a factor of 2. Matching errors were 0.2–0.5 pixels but most results fell in the 0.2–0.3 pixel range that has been stated as a rule of thumb in multiple prior studies. Horizontal resolutions of 10–20 image pixels were found, consistently greater than the 3–5 pixel spacing generally used for stereo DTM production. Resolution and precision were inversely correlated; their product varied by ≤20% (4–5 pixels squared). Refinement of the stereo DTM by photoclinometry can yield quantitative improvement in resolution (more than a factor of 2), provided that albedo variations over distances smaller than the stereo DTM resolution are not too severe. We offer specific guidance for both producers and users of planetary stereo DTMs, based on our results.