Development of the CMDM flight model instrument for MMX has been completed!

The Circum-Martian Dust Monitor (CMDM) will be one of the 13 instruments onboard the Martian Moon eXploration (MMX) spacecraft, and is tasked with investigating the dust environment surrounding Mars. Theoretical predications suggest that dust particles originating from the two moons, Phobos and Deimos, have been ejected to circle in a ring or torus shape around Mars. The CMDM will directly detect the dust particles that form the Martian dust rings, or determine an upper limit on the dust abundance, and obtain observational data that will help constrain models of how the dust reaccumulates in the orbits of the Martian moons.

The CMDM-S FM (CMDM flight model sensor unit). The CMDM-S is a simple sensor consisting of a piezoelectric element attacked to a polyimide film. It is approximately 1.4m long, 0.9m wide, and has an area of 1m2, but the weight is only 270g! The unusual shape is to avoid other equipment on the MMX spacecraft, but it can detect dust particles wherever they collide on its surface.

The basic design for the CMDM began in March 2019 at the development manufacturer, Meisei Electric. After the design review, the engineering model (EM) was manufactured and the various development tests were performed. The resulting flight model (FM) then passed both the Post Qualification test Review (PQR) and Pre-Shipment Review (PSR) by February 2024, which confirmed that development was now complete. The CMDM was then transported to the spacecraft system manufacturer, Mitsubishi Electric Corporation, at Kamakura Works in March 2024, where the instrument was officially handed over after a post-transport functionality check.

CMDM-E FM (CMDM flight model electronics unit). The CMDM-E is the device that samples and measures the waveform of the signals generated by the collision of dust particles output from the CMDM-S. Since the signals from the dust particles are very weak, and their frequency is low, the CMDM-E has an event recognition function to distinguish these from other signals (noise).

The CMDM is now assembled into the MMX spacecraft’s return module, and will be used during the spacecraft system integration tests.

Figure: Schematic of the MMX spacecraft, showing the configuration of the instruments. For the location of CMDM, see the “From -X” view.  

CMDM Principal Investigator (PI) Kobayashi Masanori
Planetary Exploration Research Center, Chiba Institute of Technology

The CMDM is an observational instrument to confirm the presence of the Martian dust ring. The instrument is a new type of dust observation device with a large sensing area that can also investigate seasonal changes in the abundance of Martian dust particles. There were many challenges during development, but the development did progress smoothly thanks to the efforts of the Meisei Electric engineers. We hope that when MMX reaches Mars, the CMDM will make the world’s first detection of the Martian dust ring!

Meisei Electric (Manufacturer for CMDM) Tsukuda Mariko
System Development Group, Technology Department, Space Defense Division, Meisei Electric (at time of appointment)

The CMDM has many new elements as part its sensor, so we spent a lot of time working on establishing the manufacturing process and considering the test conditions. We also devised ways to identify detected events, such as adding a ranking function [to indicate the certainty of a genuine dust collision signal]. We received a lot of support and cooperation from everyone involved in the development, including Professor Kobayashi and the JAXA staff, which allowed us to successfully complete the FM handover. Thank you, everyone!