In situ science on Phobos with the Raman spectrometer for MMX (RAX): preliminary design and feasibility of Raman meausrements

Mineralogy is the key to understanding the origin of Phobos and its position in the evolution of the Solar System. In situ Raman spectroscopy on Phobos is an important tool to achieve the scientifc objectives of the Martian Moons eXploration (MMX) mission, and maximize the scientifc merit of the sample return by characterizing the mineral composition and heterogeneity of the surface of Phobos. Conducting in situ Raman spectroscopy in the harsh environment of Phobos requires a very sensitive, compact, lightweight, and robust instrument that can be carried by the compact MMX rover. In this context, the Raman spectrometer for MMX (i.e., RAX) is currently under development via international collaboration between teams from Japan, Germany, and Spain. To demonstrate the capability of a compact Raman system such as RAX, we built an instrument that reproduces the optical performance of the fight model using commercial of-the-shelf parts. Using this performance model, we measured mineral samples relevant to Phobos and Mars, such as anhydrous silicates, carbonates, and hydrous minerals. Our measurements indicate that such minerals can be accurately identifed using a RAX-like Raman spectrometer. We demonstrated a spectral resolution of approximately 10 cm−1, high enough to resolve the strongest olivine Raman bands at ~820 and ~850 cm−1, with highly sensitive Raman peak measurements (e.g., signal-to-noise ratios up to 100). These results strongly suggest that the RAX instrument will be capable of determining the minerals expected on the surface of Phobos, adding valuable information to address the question of the moon’s origin, heterogeneity, and circum-Mars material transport

RAX-A compact instrument for Raman Spectroscopy aboard the Phobos rover of the MMX mission

The JAXA "Martian Moon Exploration" (MMX) mission to Phobos will include a small rover (see presentation S. Ulamec) which carries the Raman Spectrometer for MMX "RAX". The instrument is compact and lightweight yet sensitive enough to allow precision measurements of the mineralogical composition of Phobos' surface material. Here we describe the preliminary system design of the RAX spectrometer and its performance goals. It consists of an external compact laser source, fiber coupled to a spectrometer and a focusing unit as well as ancillary systems. The laser source for the spectrometer has been developed by INTA/Universidad de Valladolid for the Raman Laser Spectrometer (RLS) onboard ESAs Exomars Rover. The highly miniaturised RAX Spectrometer module (RSM) is a new development by DLR which contains a multi-objective optical system and space qualified detector and is optimized for size and performance. The focusing unit from JAXA/University of Tokyo provides finely resolved open-loop focusing over a 15 mm stroke. The entire RSM has a mass of less than 1.4 kg and a volume of only 81 x 98 x 125 mm³. RAX will be operated with the rover in-the-loop. Thus automated focusing, measurement and in-situ data processing will allow autonomous Raman spectra measurements of regolith to be taken at various sites of interest on Phobos (see presentation S. Routley). These measurements will be validated against measurements on Earth and Raman-spectra libraries. An in-flight verification is used for instrument calibration after launch. The data obtained will be compared with the Raman spectra from the ExoMars2020 mission on the Martian surface and thus support determining the origin of Phobos

Towards Martian Moons Exploration: micro-Raman and VIS-MIR reflection spectroscopy of the Phobos surface simulants

The Japan Aerospace Exploration Agency (JAXA)’ Martian Moons eXploration (MMX) remote sensing, robotic and sample return mission, scheduled to be launched in 2024 and to return in 2029, will have a strong focus on studying Phobos, including close-up surface analysis and collecting samples for Earth return. A rover, provided by CNES and DLR, will be deployed to Phobos. Its payload includes the Raman spectrometer (RAX) for in-situ characterization of the surface composition. Characterization of payload instrumentation by measurements of planetary simulants is a crucial test for performance and prediction of scientific yield. Controversial conclusions on similarity of infrared reflection and imaging of Phobos to those of low-albedo asteroids imply that combined optical spectroscopy studies will prepare a set of possible clues shortly before the MMX mission. Different Phobos simulants were selected and have been used for Raman and broad range (visible-to-mid-infrared) reflection spectroscopy in order to provide critical parameters on detectivity of mineral phases in the sample matrix as well as to compare the close-up spectroscopy with the known remote sensing of Phobos surface by previous Earth-based observatories and planetary missions

The Raman Spectrometer for Mmx Mission (rax) to Study PHOBOS

Phobos and Deimos are the targets of the coming Martian Moons eXploration mission (MMX) led by JAXA, which will fly to the Martian system and return samples from Phobos with the main goal of determining the origin and evolution of these objects [1, 2]. The characterization of the mineral composition of Phobos' surface is a crucial measurement to achieve the mission goal [3]. The RAman spectrometer for MMX, RAX, on-board the mission rover will provide in situ measurements to characterize igneous phases, secondary minerals, volatiles, and organic species of the surface material at grain scale. RAX was developed together by DLR, INTA/UVA, and JAXA/UTo [4]. RAX was already delivered to CNES and integrated in the MMX rover. MMX rover will be delivered to JAXA this summer. The scientific results of instrument may also be used to support the landing site characterization, and sample return selection