The MMX rover: performing in situ surface investigations on Phobos

A compact Raman spectrometer [1] was developed for in-situ science on Phobos with the IDEFIX rover [2], which will be launched as part of JAXA’s Martian Moon eXploration (MMX) mission in 2026. The MMX mission is dedicated to study the two Martian moons, Phobos and Deimos, with the aim of better understanding their origin and evolution [3, 4]. Orbital observations with the main MMX spacecraft and in-situ science on Phobos with the IDEFIX rover will be complemented by returning samples (>10 g) from the surface of Phobos back to Earth. The rover is expected to land between late 2028 and early 2029, in conjunction with the rehearsal for the first landing of the main spacecraft.Figure 1. left: RAX flight model (FM) during thermal vacuum testing at DLR. Right: RAX development model (DM) combined locomotion test with MMX demonstration rover in DLR testbed during a Raman measurement.The RAman spectrometer for MMX (RAX) contributes directly to the high level mission objectives by characterizing the mineral composition of the Phobos surface in-situ, providing ground truth. While different mineral phases can be associated with different formation scenarios (e.g. captured asteroid or major impact) and surface alteration processes on Phobos, the mineralogical information obtained with RAX can also help inform decisions about sampling with the main spacecraft and be compared with data obtained from the returned samples and in-situ data from the surface of Mars. The rover's mobility allows measurements to be taken from multiple positions along the rover's traverse, allowing local variations in composition to be studied. RAX measures down to the ground below the rover. RAX is extremely compact, with a mass of only 1.5 kg and a volume of about 1 dm³. The optical design of RAX was driven by 1) the tight volume and mass constraints available of the small MMX rover and 2) optimizing the collection and detection capabilities of the Raman signal from a sample at several centimeters distance below the rover’s body. Raman excitation (λ = 532 nm, typical optical power on sample 20 mW) is provided by a separate laser module based on the Raman Laser Spectrometer (RLS) laser developed for the Rosalind Franklin rover of the ExoMars mission [5]. The laser emission is transmitted to the RAX Spectrometer Module via a multimode optical fiber with a core diameter of 50 µm. To focus the laser on the Phobos surface below the rover, the spectrometer is equipped with an opto-mechanical autofocus subsystem. It allows fine-tuning of the focus position at a working distance of about 8 cm, within a range of 13 mm and an accuracy of 50 µm. The RAX instrument covers a spectral range of 535 to 680 nm, corresponding to a Raman shift of approximately 90 to 4000 cm−1 and therefore enabling the identification of water-bearing minerals. The spectral resolution across the entire spectral range is about 10 cm−1. To demonstrate the functionality of the RAX instrument after launch and to monitor its performance, a Verification Target (VT) is part of the payload. The VT is a 13 mm diameter pellet made of deuterated polyethylene terephthalate (PET) and was developed and space-qualified specifically for this mission [6]. The VT is placed in the field of view of the RAX instrument and can be measured during the cruise until the rover separates from the MMX spacecraft for landing on Phobos.For a Raman measurement on Phobos, the rover’s locomotion system is needed for the main height adjustment: the rover will gradually lower its body height until the RAX instrument is within its working range. After autofocusing, RAX will measure what is exposed beneath the rover from a footprint of 50 µm. Visual context is provided by the rover’s cameras. To improved data acquisition, Raman data will be collected during Phobos nights.Representing a collaborative effort, RAX is a joint contribution from the German Aerospace Center (DLR), Instituto Nacional de Técnica Aerospacial (INTA), and JAXA. Delivered to the MMX Phobos Rover in August 2022, the RAX flight model was successfully integrated into the IDEFIX rover in October 2022. The flight model of the rover has been delivered to JAXA/MELCO where it is currently being integrated into the main spacecraft for further qualification and functional testing. Operational sequences, e.g. defining the interaction between locomotion and science instruments, are currently being prepared. RAX scientific measurements are being prepared with laboratory studies using the RAX development model. AcknowledgementsMMX is a JAXA mission with contributions from NASA, CNES and DLR. The MMX IDEFIX rover is provided by CNES and DLR. The RAX instrument is a joint development from DLR-OS, INTA/UVa, and JAXA/UTo. The authors thank their respective national funding frameworks including DLR’s Programmatik Raumfahrt and PID2022-142490OB-C31 funded by MCIN/AEI/10.13039/501100011033 and are grateful to the MMX, IDEFIX rover and RAX instrument teams who made this work possible.

Introduction:  The JAXA Martian Moons Exploration (MMX) mission [1] will deploy the French-German IDEFIX rover (Fig. 1) to the surface of Phobos [2]. The IDEFIX rover will attempt wheeled-locomotion on a low-gravity surface for the first time thus providing a unique opportunity to study the surface properties of Phobos and the behaviour of regolith on small-bodies.     Figure 1 (left) The MMX IDEFIX rover (image credit: JAXA). (right) A WheelCam (image credit: CNES)The WheelCams:  The IDEFIX rover includes two WheelCams, placed on the underside of the rover and each aimed at a different rover wheel [3]. The WheelCam image sensors are panchromatic and consist of a 2048 by 2048 array. The optics provide a field of view of 32.5° and a pixel resolution of approximately 100 μm at the centre of the image. The WheelCams are also equipped with LEDs to illuminate the scene; white LEDs to be used while driving, and three colour LEDs (590, 720 and 880 nm) to allow for multispectral imaging. The WheelCams can be operated in both an imaging and a movie mode. Typical movie frame rates are expected to be 1 image per mm moved for the front WheelCam, 1 image per cm moved for the rear WheelCam (the anticipated rover speed is ~0.1-4 mm/s).Science Objectives of the WheelCams: The WheelCam images will be used to characterize the general grain properties of the regolith (size distribution, morphological parameters [3]), within the limits of the resolution. The WheelCam images will also be used to determine the adhesive properties of regolith particles stuck to the rover wheels and the depth of the wheel sinkage, which is closely linked to the load bearing strength [4] and friction angle of the regolith [5].  The linear and angular velocities of the wheel will be calculated from the WheelCam images in order to provide measurements of the traction and slippage of the wheel. In addition to providing important information about the performance of the locomotion, this also provides the shearing characteristics of the regolith [6,7]. Topographical reconstruction of the rover tracks, talus and tailings behind the wheels [8] will provide additional constraints on the physical properties of the regolith.  Finally, using the coloured LEDs it will be possible to study the mineralogical composition of the regolith from reflectance and albedo measurements, and to asses space weathering by comparing inside and outside of the rover tracks.Preparing for the WheelCam analyses: In anticipation of the MMX mission, we have developed the MMX WheelCam testbed (Fig. 2, [9]) that recreates the scene that the WheelCams will observe during the mission (Fig. 3). The main objective of the testbed is to develop the image processing tools for the WheelCams. The testbed is instrumented with multiple sensors allowing measurements to be made of the sinkage of the wheel into the soil, and the slippage (essentially the loss of traction) of the wheel. The testbed also includes the MMX rover wheel, camera baffles, the LEDs and blackout panels to perform trials in representative lighting conditions.  Figure 2. Two different views of the MMX WheelCam testbed at ISAE-SUPAERO.Figure 3. WheelCam approximate field of views, as generated by the WheelCam testbed. (left) Front WheelCam perspective. (right) Rear WheelCam perspective.We also perform Discrete Element Method simulations [10] in order to understand the influence of the low gravity environment on sinking and driving behaviour (Fig. 4; [11, 12]]. This is essential to ensure an accurate determination of the regolith properties from the wheel – surface interactions.Figure 4. Snapshot from a rolling simulation where gravity is 0.006 m/s2 and the rotational velocity is 0.65 rad/s [11,12].Conclusions: This presentation will discuss the expected science return from the MMX IDEFIX rover WheelCams and provide a status of the preparatory activities and image processing pipelines under development.Acknowledgments: We acknowledge CNES funding.

Incident angle dependence of backscattered light by regolith layers

The surface properties and electrical behavior of carbon-based materials can be effectively modified by energetic ion irradiation. In the present study, graphene oxide (GO) and cyclic olefin copolymer foils (COC, Topas 112 and 011, respectively) were irradiated with 1 MeV Au ions using a 3 MV Tandetron accelerator at fluences of 1 × 1014, 1 × 1015, and 2.5 × 1015 cm-2. The irradiation induced systematic modifications in surface chemistry, morphology, wettability, and electrical properties. Composition changes were investigated using Rutherford backscattering spectrometry (RBS) and elastic recoil detection analysis (ERDA), while surface morphology and roughness were characterized by atomic force microscopy (AFM). This revealed a clear fluence-dependent evolution of nanoscale topography. The vibrational characteristics were assessed through Raman spectroscopy, and the chemical composition of the surface layers was analyzed by X-ray photoelectron spectroscopy (XPS). The surface wettability was evaluated by static contact angle measurements, and surface free energy was determined using the Owens-Wendt-Rabel-Kaelble (OWRK) method. These measurements showed a consistent decrease in water contact angle and an increase in surface free energy with increasing ion fluence in the COC substrates, whereas GO exhibited a distinct response. Electrical characterization demonstrated a pronounced fluence-dependent decrease in sheet resistivity in polymers. The results show that 1 MeV Au ion irradiation enables systematic and fluence-dependent modification of both surface and electrical properties.

Surface and bulk characterization of an ultrafine South African coal fly ash with reference to polymer applications

NASA MESSENGER mission: a tool to study Mercury beyond its operative life

The large uniaxial magnetic anisotropy energy (∼ 6.6 MJ m) of Fe–Pt alloys makes their nanostructured forms attractive for potential use as nanoscale magnetic bits in ultrahigh-density information storage devices or as fillers to create new types of magnetocomposites. The high magnetic anisotropy and coercivity arise from the chemically ordered face-centered-tetragonal (fct) L10 phase, which is sensitive to both chemical composition and the size of the nanoparticles. Control over particle size and dispersity 13] is essential to form ordered arrays of nanoparticles, and preserve these features against agglomeration during high-temperature annealing (e.g., 550 °C) treatments used to obtain the L10 phase. Therefore, it is crucial to develop protocols to produce FePt nanoparticles with control over composition, particle size, and dispersity, and thermal stability for exploiting their assemblies for data-storage media applications. The synthesis technique described here is a promising approach to realize all these features simultaneously. Prior works have demonstrated FePt nanoparticles synthesis with either excellent size control or chemical compositional control but not both. Thermal decomposition of Fe(CO)5 vapor, and reduction of Pt(acac)2, produces monodisperse nanoparticles with tunable sizes in the 2–15 nm range. But, the chemical composition of the nanoparticle is different from the initial molar ratio of the metal precursors due to different precursor decomposition rates. Size control is further complicated by the strong influence of parameters such as Ar gas flow rate, heating rate, and temperature. For example, a Fe(CO)5/Pt(acac)2 ratio of two yields Fe-deficient (Fe44Pt56) 9 nm nanoparticles or Fe-rich (Fe53Pt47) 6 nm nanoparticles, depending on the heating rate. In contrast, coreduction of FeCl2 and Pt(acac)2 results in nanoparticles with chemical compositions within 2 % of the initial molar ratio of the metal precursors, but the particle size is constrained to a limited range of approximately 3–5 nm. Neither of these two synthesis routes is easily amenable to coating the nanoparticles with a protective shell of a thermally stable material (e.g., silica or titania) that could prevent particle shape and size changes during postsynthesis annealing for obtaining the L10 phase. Although a Fe3O4 shell can be formed [15] by the thermal decomposition method, the shell degrades at temperatures less than 600 °C and destroys the nanoparticle structure and shape. Techniques to coat a silica shell on clusters of magnetic nanoparticles that have been presynthesized using a separate processing method have been demonstrated, but these techniques are not well suited for creating organized assemblies of well-separated nanoparticles for recording media applications. Here, we report the room-temperature synthesis of monodisperse FePt nanoparticles with tunable particle size over an extended range of 4–20 nm and excellent compositional control using microemulsions. We further use the same microemulsion to enhance the nanoparticle thermal stability by forming a 2 nm thick silica shell, which is also used for functionalization with organosilanes. Organized assemblies formed from the molecularly capped core/shell particles exhibit high coercivity Hc ∼ 850 mT due to L10 ordering in the particles upon annealing to 650 °C, without any observable changes to the overall nanoparticle size and shape. Synthesis and integration of high-coercivity nanomagnets of controlled shape, size, composition, surface chemistry, and stability, with molecularly engineered surfaces and matrices (e.g., polymers and biomaterials) open up new possibilities for realizing novel flexible memory devices and magnetocomposites. K2PtCl4 and FeCl3 were reduced simultaneously with N2H4, in reverse micellar microemulsions composed of nanoscopic water droplets stabilized by nonionic surfactant molecules, brij 56 or brij 52, in iso-octane. Scheme 1 illustrates the partiC O M M U N IC A IO N S

In this paper, a 3D convex shape model of (175706) 1996 FG3, which consists of 2040 triangle facets and 1022 vertices, is derived from the known lightcurves. The best-fit orientation of the asteroid's spin axis is determined to be $\lambda =237.7^\circ$ and $\beta=-83.8^{\circ}$ considering the observation uncertainties, and its rotation period is $\sim$ 3.5935 h . Using the derived shape model, we adopt the so-called advanced thermophysical model (ATPM) to fit three published sets of mid-infrared observations of 1996 FG3 \citep{Wolters2011,Walsh2012}, so as to evaluate its surface properties. Assuming the primary and the secondary bear identical shape, albedo, thermal inertia and surface roughness, the best-fit parameters are obtained from the observations. The geometric albedo and effective diameter of the asteroid are reckoned to be $p_{\rm v}=0.045\pm0.002$, $D_{\rm eff}=1.69^{+0.05}_{-0.02}$ km. The diameters of the primary and secondary are determined to be $D_{1}=1.63^{+0.04}_{-0.03}$ km and $D_{2}=0.45^{+0.04}_{-0.03}$ km, respectively. The surface thermal inertia $\Gamma$ is derived to be a low value of $80\pm40\rm Jm^{-2}s^{-0.5}K^{-1}$ with a roughness fraction $f_{\rm R}$ of $0.8^{+0.2}_{-0.4}$. This indicates that the primary possibly has a regolith layer on its surface, which is likely to be covered by a mixture of dust, fragmentary rocky debris and sand. The minimum regolith depth is estimated to be $5\sim20\rm mm$ from the simulations of subsurface temperature distribution, indicating that 1996 FG3 could be a very suitable target for a sample return mission.

Characterization of surface and bulk properties of α-Tocopherol blended and γ irradiated UHMWPE sandwich nanocomposites

This thesis was aimed at investigating the physical-chemical properties and the behaviour in physiological environment of two classes of bioceramics: calcium silicate-based dental cements and alumina-based femoral heads for hip joint prostheses. The material characterization was performed using spectroscopic techniques such as that allow to obtain information on the molecular structure of the species and phases present in the analyzed samples. Raman, infrared and fluorescence spectroscopy was principally used. Calcium silicate cements, such as MTA (Mineral Trioxide Aggregate), are hydraulic materials that can set in presence of water: this characteristic makes them suitable for oral surgery and in particular as root-end filling materials. With the aim to improve the properties of commercial MTA cements, several MTA-based experimental formulations have been tested with regard to bioactivity (i.e. apatite forming ability) upon ageing in simulated body fluids. The formation of a bone-like apatite layer may support the integration in bone tissue and represents an essential requirement for osteoconduction and osteoinduction. The spectroscopic studies demonstrated that the experimental materials under study had a good bioactivity and were able to remineralize demineralized dentin. . Bioceramics thanks to their excellent mechanical properties and chemical resistance, are widely used as alternative to polymer (UHMWPE) and metal alloys (Cr-Co) for hip-joint prostesis. In order to investigate the in vivo wear mechanisms of three different generations of commercial bioceramics femoral heads (Biolox®, Biolox® forte, and Biolox® delta), fluorescence and Raman spectroscopy were used to investigate the surface properties and residual stresses of retrieved implants. Spectroscopic results suggested different wear mechanisms in the three sets of retrievals. Since Biolox® delta is a relatively recent material, the Raman results on its retrievals has been reported for the first time allowing to validate the in vitro ageing protocols proposed in the literature to simulate the effects of the in vivo wear.

Many industrial processes involve the modification of surfaces. The semiconductor and microelectronics industries are extremely reliant upon surface processing [1], but other applications include solar cells, MEMS and microfluidics, thermal barrier coatings, and fuel cells. Optical measurements are commonly used to indirectly quantify the surface and bulk properties of materials. Unlike direct imaging methods, in which the local surface topography is visualized, indirect methods provide information on surface and bulk properties which are averaged over the entire area being sampled. Typically, a beam of light is directed at the surface to be measured, and the light interacts with the surface to produce the reflected or diffracted light that is then measured by a photodetector. One advantage of indirect measurement techniques is that they are non-invasive, and therefore can be used in extreme or harsh processing environments such as vacuum chambers and reaction vessels by passing the light through windows. These in situ optical sensors have been used for process control of film thickness and chemical composition. However, many more microscopic and nanoscale surface properties can be measured and potentially controlled using optical sensors. The barriers include the difficulty of modeling the optical response, the difficulty of inverting these relationships to robustly infer surface properties, and the practicality of including windows on the chamber to enable optical access. However, to create precise nanostructures in a high-throughput manufacturing setting, real-time measurement and control will be required, and optical sensors are expected to play a significant role.

The effect of UV and thermally induced oxidation on the surface and structural properties of CVD diamond layers with different grain sizes

Frequently, passive dry deposition collectors are used to sample atmospheric dust deposition. However, there exists a multitude of different instruments with different, usually not well-characterized sampling efficiencies. As a result, the acquired data might be considerably biased with respect to their size representativity, and as a consequence, also composition. In this study, individual particle analysis by automated scanning electron microscopy coupled with energy-dispersive X-ray was used to characterize different, commonly used passive samplers with respect size-resolved chemical and physical properties of mineral dust aerosol particles. In addition, computational fluid dynamics simulations were conducted to predict the deposition of particles on to different passive samplers and thereby to achieve deposition velocities from a theoretical point of view. Scanning electron microscopy (SEM) calculated deposition rate measurements made using different passive samplers show a disagreement among the samplers. Modified Wilson and Cooke (MWAC) and Big Spring Number Eight (BSNE) - both horizontal flux samplers - collect considerably more material than Flat plate and the Sigma-2, which are vertical flux samplers. The collection efficiency of MWAC increases for large particles in comparison to Sigma-2 with increasing wind speed, while such an increase is less observed in the case of BSNE. A positive correlation is found between deposition rate and PM10 concentration measurements by an optical particle spectrometer. The results indicate that a BSNE and Sigma-2 can be good options for PM10 measurement, whereas MWAC and Flat plate samplers are not a suitable choice. A negative correlation was observed in between dust deposition rate and wind speed. Deposition velocities calculated from different classical deposition models do not agree with deposition velocities estimated using computational fluid dynamics simulations (CFD). The deposition velocity estimated from CFD was often higher than the values derived from classical deposition velocity models. Moreover, the modeled deposition velocity ratios between different samplers do not agree with the observations. Results also show that mineral dust is found to be the dominating mineral particle type during this campaign, comprising of different classes of classes of silicates, quartz-like, calcite-like, dolomite-like and gypsum-like particles. In addition, the analysis clearly indicates that the composition of dust aerosol particles remains largely unaffected by the sampler type. By using the relative abundance of the particle groups, size-resolved complex refractive index of dust particles is calculated. It is found that average refractive index is mainly wavelength dependent. The calculated real part of refractive index varied in between 1.71 and 1.53 for wavelengths ranging from 370 to 950 nm. Likewise, the imaginary part of refractive index is calculated for iron oxide particles and is varied in between 3.28*10-4 to 7.11*10-5 for wavelengths in the range of 250-1640 nm. Additionally, the refractive index values have shown a slight decrease with particle size. In the study, the potential for buffering of dust aerosol particles on the acid mobilization of iron particles is also analyzed. From analysis, it is found that the buffering potential depends on the environmental conditions and time. Moreover, by analyzing the ratio of sulfate mass to the total mass of dust of individual particles with the particle sizes, the mixing state of sulfate particles in the total dust particles were investigated. The analysis indicates that the finer dust particles were associated with higher content of sulfur, while the coarse dust particles corresponds to lower sulfur contents revealing only fine mode sulfate is internally mixed with mineral dust aerosol particles. Overall, the results show that passive sampling techniques coupled with an automated single particle analysis could be a good option to assess physical and chemical properties of atmospheric mineral dust particles.

Particle replication in nonwetting templates (PRINT) is a continuous, roll-to-roll, high-resolution molding technology which allows the design and synthesis of precisely defined micro- and nanoparticles. This technology adapts the lithographic techniques from the microelectronics industry and marries these with the roll-to-roll processes from the photographic film industry to enable researchers to have unprecedented control over particle size, shape, chemical composition, cargo, modulus, and surface properties. In addition, PRINT is a GMP-compliant (GMP=good manufacturing practice) platform amenable for particle fabrication on a large scale. Herein, we describe some of our most recent work involving the PRINT technology for application in the biomedical and material sciences.

Reactive sites on the surface of polycyclic aromatic hydrocarbon clusters: A numerical study