How to find the best samples on a moon: Building relationships and solving engineering challenges in France

CNES and JAXA members gathered together at the IAS in France. (Credit: Philippe Lier)

(Article by Dr Sarah Crites, International Top Young Fellow at ISAS)

With major contributions from both France’s Centre National d’Etudes Spatiales (CNES) and the United States’ NASA, the Martian Moons eXploration mission is a model for international cooperation in space science. The French space agency are not only developing a key remote sensing instrument to map the moons of Mars, but are also contributing expertise in flight dynamics to plan the mission’s complex orbiting and landing manoeuvres and investigating the possibility of a rover to explore the surface of Phobos.

On October 30th, representatives from JAXA and CNES gathered in Paris to deepen this cooperation by holding a joint review of the status of the Martian Moons eXploration mission and plans for the smooth integration of the French and Japanese team members. The joint review was followed up by a technical meeting held at the Institute Astrophysique Spatial (IAS) in Orsay and at CNES headquarters in Toulouse, to discuss the CNES rover study as well as ongoing mission and instrument design details.

The acousto-optical tunable filter (AOTF): a key part of the spectrometer being designed by CNES.

The joint review gave the JAXA representatives, including MMX study team leader Yasuhiro Kawakatsu, JAXA/ISAS Research Director Masaki Fujimoto, and the JAXA International Affairs team, the opportunity to learn about the design of MacrOmega, the near infrared hyperspectral imager being contributed by CNES, and to see the world-class instrument test and calibration facilities at the Institute Astrophysique Spatial (IAS), where MacrOmega will be built. In return, Kawakatsu presented an overview of the mission and provided detailed insights into the mission development process for the CNES and IAS representatives.

With the MMX team spread across the world, an important portion of the review was dedicated to discussing how to smoothly conduct joint development and operations throughout the mission. This challenging international coordination task will be made easier by the experience developed through JAXA’s Hayabusa2 mission, which carries the MASCOT lander, developed by the German Space Agency DLR in partnership with CNES.

The scientists and engineers of MMX immediately put into action the enhanced spirit of cooperation developed during the joint review by tackling key engineering questions together during the technical portion of the meeting. The scientific question at the heart of the technical topics being discussed was this: The main goal of the MMX mission is to bring back samples from the surface of one of the moons of Mars, and to determine their origin from these samples; but how will we know if those samples are representative of the whole surface?

Putting the samples in context is one of the major goals of the MacrOmega near infrared imaging spectrometer, designed by IAS and supported by CNES. MacrOmega will map the global mineralogy of Phobos or Deimos to help select representative landing sites for sample collection. During the meeting on October 31, the MacrOmega team described the parameters needed for high-quality global mapping (for example, measurements must be made when lighting conditions are favorable) and the CNES and JAXA flight dynamics experts compared calculations for what orbital trajectories could accomplish these goals. The flight dynamics teams agreed that nearly the entire surface of Phobos could be mapped by MacrOmega with just a few weeks of observations–but the best season and time of day for observations still have to be considered to create the best observation plan possible.

Everyone is fascinated by the instrument demonstration at IAS

MacrOmega’s global measurements will be made at a spatial resolution of about 20 meters, whereas the samples collected will be sand-like regolith particles at most a few cm in size. This raises a second question: how can we bridge the gap between sample and orbital measurement scales? During the meeting, the Japanese and French team members of MacrOmega discussed the challenges and feasibility of making measurements while the spacecraft descends to the surface of the moon, in order to directly link the orbital measurements to the samples on the ground. The MacrOmega and flight dynamics teams are continuing to study this operation concept, which would require additional lenses to keep the ground in focus as the spacecraft lands, as well as a well-controlled descent path and close coordination with the spacecraft design team.

Another complication arises when we consider that MacrOmega and the other remote sensing instruments will link the samples collected to global measurements, but with only one or two landings, how can we characterize lateral variations in geology from boulder to boulder or crater to crater? One possible way to address this question is a rover to explore the local geology of the surface of Phobos or Deimos. This concept is currently under study at CNES, and the exciting idea of building the first rover to drive on another planet’s moon has inspired a diverse group of CNES mechanical and electrical engineers, thermal designers, and regolith scientists to join the project. The CNES team has been conducting an ongoing study of the feasibility of exploring one of the moons with a rover, given the challenging low gravity, extreme temperatures, and unknown regolith environment. The CNES team presented some preliminary study results and discussed design details with the MMX study team leader and system team during the meeting on November 2.

The intimate involvement of both CNES and NASA in contributing scientific and engineering expertise to the mission opens up new worlds of possibilities and discoveries just beginning to be explored by the international Martian Moons eXploration mission team. The opportunities offered by this pathfinder mission are inspiring early-career scientists from all over the world to come to Japan to participate in the next frontier of space exploration. With the number of international researchers increasing every year, the MMX mission team is a microcosm of the rapidly internationalizing spirit of ISAS as a whole, and will provide valuable insights for bringing together international teams to enable equally ambitious and groundbreaking missions in the future.