The SuperCam Instrument Suite on the Mars 2020 Rover: Science Objectives and Mast-Unit Description

On the NASA 2020 rover mission to Jezero crater, the remote determination of the texture, mineralogy and chemistry of rocks is essential to quickly and thoroughly characterize an area and to optimize the selection of samples for return to Earth. As part of the Perseverance payload, SuperCam is a suite of five techniques that provide critical and complementary observations via Laser-Induced Breakdown Spectroscopy (LIBS), Time-Resolved Raman and Luminescence (TRR/L), visible and near-infrared spectroscopy (VISIR), high-resolution color imaging (RMI), and acoustic recording (MIC). SuperCam operates at remote distances, primarily 2-7 m, while providing data at sub-mm to mm scales. We report on SuperCam's science objectives in the context of the Mars 2020 mission goals and ways the different techniques can address these questions. The instrument is made up of three separate subsystems: the Mast Unit is designed and built in France; the Body Unit is provided by the United States; the calibration target holder is contributed by Spain, and the targets themselves by the entire science team. This publication focuses on the design, development, and tests of the Mast Unit; companion papers describe the other units. The goal of this work is to provide an understanding of the technical choices made, the constraints that were imposed, and ultimately the validated performance of the flight model as it leaves Earth, and it will serve as the foundation for Mars operations and future processing of the data.In France was provided by the Centre National d'Etudes Spatiales (CNES). Human resources were provided in part by the Centre National de la Recherche Scientifique (CNRS) and universities. Funding was provided in the US by NASA's Mars Exploration Program. Some funding of data analyses at Los Alamos National Laboratory (LANL) was provided by laboratory-directed research and development funds

Time-resolved Raman and luminescence spectroscopies for Mars exploration

En 2021, le rover Mars 2020 de la NASA déploiera l’instrument SuperCam dans le cratère Jezero sur Mars. Cet instrument franco-américain multi-techniques d'analyse à distance sera équipé notamment d’un LIBS (analyse chimique) et d’un spectromètre Raman et de luminescence résolu en temps (analyse minéralogique). Après étude de paramètres environnementaux ainsi que de facteurs intrinsèques à l’échantillon cible, la spectroscopie Raman résolue en temps s’avère très puissante et permet la réalisation de spectres Raman dépourvus de signaux parasites (e.g. luminescence) pour de nombreux minéraux (carbonates, phosphates, silicates) parfois non analysables en Raman conventionnel. Une base de données de spectres Raman résolu en temps a ainsi été élaborée. Les effets de tirs laser LIBS sur la structure et la signature Raman de nombreux minéraux ont été étudiés sur la base d’expériences et de modélisations thermiques simples. Les résultats montrent un effet majeur (vitrification voire transition de phase) pour des minéraux opaques à fort coefficient d'absorption optique alors que les effets sont minimes, voire non détectables, pour des phases plus transparentes. Ces résultats sont discutés en termes de contraintes opérationnelles pour les instruments du rover Mars2020. L’étude de la luminescence des terres rares dans des apatites synthétiques dopées et naturelles montre que la luminescence est un outil pertinent de détection de ces éléments. En revanche, l’étude des temps de décroissance met en évidence des phénomènes complexes de transferts d’énergie entre centres émetteurs et limite l’utilisation de ces temps de décroissance pour une éventuelle quantification des terres rares.In 2021, the NASA Mars 2020 rover will deploy the SuperCam instrument in the Jezero crater on Mars. This franco-american multi-tool instrument for remote analysis will be equiped with LIBS (chemical analysis) and with a time-resolved Raman and luminescence spectrometer (mineralogical analysis). After investigating various environmental parameters as well as intrinsic factors from the target sample, time-resolved Raman spectroscopy appears as a powerful tool to obtain high-quality Raman spectra free of parasitic signal (e.g. luminescence) for many mineral phases (carbonates, phosphates, silicates), even in the case of minerals hardly analysable with conventional Raman. A database of time-resolved Raman spectra has been elaborated. The effects of LIBS laser shots on the mineral structure and Raman fingerprint have been studied experimentally and through simple thermal modeling. Results show a major structural effect (vitrification and/or phase transition) in the case of opaque minerals with high optical absportion coefficient whereas the effects are minimal, or even non detectable, for more transparent and less absorbing minerals. Implications of these results for the operation of the Mars 2020 instruments are discussed. The study of Rare-Earth Elements (REE) luminescence in synthetic doped and natural apatites shows that luminescence is powerful to detect and characterize REEs. However, due to strong transfer energy among emission centers, the possible use of luminescence lifetime appears to be impossible to quantify REE in natural apatites

Reconstructing the 3D shape of sulfate unit outcrops (Gale crater, Mars) using ChemCam's Remote Micro Imager onboard the Curiosity rover.

International audienceGale crater on Mars records a large section of sedimentary rocks, mainly represented by the 5-kmthicksequence of Mount Sharp (Aeolis Mons). The lower part of this sequence has been explored bythe Curiosity rover of the Mars Science Laboratory (MSL) mission, revealing lacustrine to fluvialdepositional sequences [e.g., 1] bearing clay minerals [2]. Orbital observations highlighted thepresence of clay minerals at the base of Mt Sharp but also hint at a major wet to dry environmentalchange with clay-bearing rocks giving way to several hundred of meters of sulfate-bearing strata [3,4]. Orbital data coupled with rover-based observations revealed that the sulfate-bearing unit recordcoincides with a major change of depositional environment followed by alternation of wetter anddrier conditions rather than a monotonous aridification during the Hesperian epoch [5].Before Curiosity reached this part of Gale crater, those observations were supported using longdistanceimaging capabilities of the Remote Micro-Imager (RMI) sub-system of the ChemCaminstrument [6]. With a focal length of 700 mm, the RMI telescope complements the color Mastcamimagers with higher spatial resolution views of sedimentary structures and textures of rocksoutcropping several hundred meters up to a few kilometers away from the rover (a ~60 km-recordobservation having recently been achieved, [7]). This capacity is therefore used by the MSL teamboth to plan future guidance of the rover and to observe geologic features from a distance. Theselong-distance observations pointed at the sulfate-bearing unit reveal the presence of sub-metricscalecross-stratifications and deflation surfaces as well as diagenetic features (e.g., “satin spar”;Fig. 1). While their size allows for long-range remote observation (i.e., several hundred meters awayusing imagers onboard the rover, Mastcam and RMI), the resulting images lacks depth due to thedistance. Yet, such 3D information can be critical in characterizing and understanding thesedimentary processes behind the setting of these structures.To improve our observations, we are conducting an imaging experiment to reconstruct the 3D shapeof the sulfate-bearing unit outcrops with Structure-from-Motion photogrammetry using ChemCam’sRMI frames. This method is usually performed on close-range geologic features observed with otherimagers onboard the rover (MAHLI, Mastcam, Navcam, [8]), but such an approach had never beenapplied to long-distance RMI frames. Here, we apply photogrammetric treatment to specific sets ofrepeated long-distance observations on the sulfate-bearing unit. To cope with the high distance ofthe target, we use a several-hundred meters “virtual baseline” represented by successive positionsof the rover along its traverse. Figure 1 shows one of the two long-distance (1x12) RMI mosaics(ccam04947, taken on Sol 2947, cf. Fig. 2) which served as input in the stereoscopic test. Thismosaic illustrates an outcrop of the sulfate-bearing unit situated ~650 meters away from the roverat that time (Fig. 2). A second similar mosaic pointed at the same target was taken on Sol 2962(2x16 RMI mosaic, ccam04962) after the rover drove about 200 meters southeastwards (Fig. 2).able to reconstruct the shape of the outcrop. The resulting 3D model presented in Figure 3 revealsthe actual 3D shape of the imaged outcrop situated several hundred meters away from the rover, aswell as displaying with improved accuracy the spatial distribution of the sedimentary and/ordiagenetic structures. The use of this technique to produce long-distance 3D models will have criticalimplication in helping to assess and to characterize the depositional conditions related to the sulfatebearingunit, a key objective of the Curiosity rover. The use of these models could also serve to helpplanning the upcoming exploration of this interval by designating high-interest targets. We also lookforward to applying this method to long-distance color images obtained with the more advancedcolor RMI subsystem of the SuperCam instrument onboard the Perseverance rover currentlyoperating in Jezero crater [9, 10]

Long-Distance 3D Reconstructions Using Photogrammetry with Curiosity's ChemCam Remote Micro-Imager in Gale Crater (Mars)

International audienceThe Mars Science Laboratory rover Curiosity landed in Gale crater (Mars) in August 2012. It has since been studying the lower part of the 5 km-high sedimentary pile that composes Gale's central mound, Aeolis Mons. To assess the sedimentary record, the MSL team mainly uses a suite of imagers onboard the rover, providing various pixel sizes and fields of view from close to longrange observations. For this latter, we notably use the Remote Micro Imager (RMI), a subsystem of the ChemCam instrument that acts as 700 mm-focal length telescope, providing the smallest angular pixel size of the set of cameras on the Remote Sensing Mast. The RMI allows observations of remote outcrops up to a few kilometers away from the rover. As retrieving 3D information is critical to characterize the structures of the sedimentary deposits, we describe in this work an experiment aiming at computing for the first time with RMI Digital Outcrop Models of these distant outcrops. We show that Structure-from-Motion photogrammetry can successfully be applied to suitable sets of individual RMI frames to reconstruct the 3D shape and relief of these distant outcrops. These results show that a dedicated set of observations can be envisaged to characterize the most interesting geological features surrounding the rover

Time-resolved Raman and luminescence spectroscopy of synthetic REE-doped hydroxylapatites and natural apatites

International audienceUsing continuous and time-resolved spectroscopy, we investigate Raman and luminescence signals from synthetic hydroxylapatites doped with trivalent REE including Dy 3+ , Eu 3+ , Nd 3+ , and Sm 3+ , as well as REE in natural apatites, with laser excitations at 532 nm and 785 nm. We demonstrate that time-resolved spectroscopy is an extremely efficient method to tone down the luminescence from Raman spectra or, alternatively, to investigate the luminescence signal without the interference from the Raman contribution. Time-resolved luminescence spectroscopy is found to be a powerful technique for generating specific high-quality luminescence spectra for the REE emission activators in apatites by using appropriate combinations of delay and gate width for the time synchronization of the laser pulse and ICCD detector. This allows for the unambiguous detection and identification of the activators by avoiding the overlapping of various emission signals in the luminescence spectra. This is particularly useful in the case of natural samples, which often have several activators for luminescence. In the case of synthetic REE-doped apatites, a quenching process for luminescence due to activator concentration is seen for Eu 3+ and Sm 3+ , i.e. the higher the concentration, the shorter the luminescence decay time. The interpretation of luminescence decay time in natural apatites is promising but more complex because of energy transfers between the various luminescence activators present in the crystal lattice. Luminescence is a powerful technique for detecting the presence of REE in apatites down to ppm levels, though quantifying the concentration is still a challenge

Pulsed laser-induced heating of mineral phases: Implications for Laser-Induced Breakdown Spectroscopy combined with Raman spectroscopy

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IMPLICATIONS OF THE LOCAL TOPOGRAPHY OF THE MARKER BAND CONTACT, GALE CRATER

International audienceSatellite-based investigations of Mt. Sharp stratigraphy in Gale Crater show a unit with distinctive tonal and erosional expression that can be traced in extended outcrops at several locations along the mountain’s southern, western, and northern margins [1, 2, 3]. Slopes measured on the exposed outcrop suggested a radial deposition pattern in the construction of Mt. Sharp, with important implications for formation mechanisms and spatial extent of mountain construction (2). Alternatively, the slopes have been proposed to be due to differential compaction of initially nearhorizontal layers [4]. The distinct character of the unit, referred to as the Marker Bed (now labelled the Marker Band), has motivated various theories for its origin (recently summarized in [3]), ranging from better induration due to arid depositional setting, to its being a volcanic ash.By Sol 3351, the Curiosity rover approached an area with multiple exposures, now known as Marker Band valley (Fig. 1), which enabled the first close observations of the Marker Band. Observations of the Marker Band and several associated units continue and are presented in multiple 2023 LPSC abstracts. Our report is based on examination of over 20 Curiosity ChemCam Long Distance Remote Micro Images and Mastcam images

IMPLICATIONS OF THE LOCAL TOPOGRAPHY OF THE MARKER BAND CONTACT, GALE CRATER

International audienceSatellite-based investigations of Mt. Sharp stratigraphy in Gale Crater show a unit with distinctive tonal and erosional expression that can be traced in extended outcrops at several locations along the mountain’s southern, western, and northern margins [1, 2, 3]. Slopes measured on the exposed outcrop suggested a radial deposition pattern in the construction of Mt. Sharp, with important implications for formation mechanisms and spatial extent of mountain construction (2). Alternatively, the slopes have been proposed to be due to differential compaction of initially nearhorizontal layers [4]. The distinct character of the unit, referred to as the Marker Bed (now labelled the Marker Band), has motivated various theories for its origin (recently summarized in [3]), ranging from better induration due to arid depositional setting, to its being a volcanic ash.By Sol 3351, the Curiosity rover approached an area with multiple exposures, now known as Marker Band valley (Fig. 1), which enabled the first close observations of the Marker Band. Observations of the Marker Band and several associated units continue and are presented in multiple 2023 LPSC abstracts. Our report is based on examination of over 20 Curiosity ChemCam Long Distance Remote Micro Images and Mastcam images

The SuperCam Instrument Suite on the NASA Mars 2020 Rover: Body Unit and Combined System Tests

TheSuperCaminstrumentsuiteprovidestheMars2020rover,Perseverance,with a number of versatile remote-sensing techniques that can be used at long distance as well as within the robotic-arm workspace. These include laser-induced breakdown spectroscopy (LIBS), remote time-resolved Raman and luminescence spectroscopies, and visible and in- frared (VISIR; separately referred to as VIS and IR) reflectance spectroscopy. A remote micro-imager (RMI) provides high-resolution color context imaging, and a microphone can be used as a stand-alone tool for environmental studies or to determine physical properties of rocks and soils from shock waves of laser-produced plasmas. SuperCam is built in three parts: The mast unit (MU), consisting of the laser, telescope, RMI, IR spectrometer, and associated electronics, is described in a companion paper. The on-board calibration targets are described in another companion paper. Here we describe SuperCam’s body unit (BU) and testing of the integrated instrument.The BU, mounted inside the rover body, receives light from the MU via a 5.8 m opti- cal fiber. The light is split into three wavelength bands by a demultiplexer, and is routed via fiber bundles to three optical spectrometers, two of which (UV and violet; 245–340 and 385–465 nm) are crossed Czerny-Turner reflection spectrometers, nearly identical to their counterparts on ChemCam. The third is a high-efficiency transmission spectrometer contain- ing an optical intensifier capable of gating exposures to 100 ns or longer, with variable delay times relative to the laser pulse. This spectrometer covers 535–853 nm (105–7070 cm−1 Ra- man shift relative to the 532 nm green laser beam) with 12 cm−1 full-width at half-maximum peak resolution in the Raman fingerprint region. The BU electronics boards interface with the rover and control the instrument, returning data to the rover. Thermal systems maintain a warm temperature during cruise to Mars to avoid contamination on the optics, and cool the detectors during operations on Mars.Results obtained with the integrated instrument demonstrate its capabilities for LIBS, for which a library of 332 standards was developed. Examples of Raman and VISIR spec- troscopy are shown, demonstrating clear mineral identification with both techniques. Lumi- nescence spectra demonstrate the utility of having both spectral and temporal dimensions. Finally, RMI and microphone tests on the rover demonstrate the capabilities of these sub- systems as well