Development of the IREM flight model for MMX is complete!

Included in the 13 instruments onboard the Martian Moons eXploration (MMX) spacecraft is the Interplanetary Radiation Environment Monitor (IREM). IREM will acquire the energy spectrum (level of radiation at different energies) of high-energy solar particles; data which will help establish methods for evaluating the exposure dose to potentially dangerous radiation that would be experienced by a human crew visiting the Martian system. 

In particular, IREM will measure the energy spectrum of high-energy proton events (SPEs) with energy between 15 – 300 MeV that are generated during solar flares, and also obtain a count of any proton with energies of above 300 MeV. IREM uses a sensor configuration that combines a silicon sensor and a moderator (which slows the protons to increase detection efficiency) to detect not only SPEs but also the energy spectrum of nuclides (the nucleus of atoms) that form the galactic cosmic rays (GCR), and the linear energy transfer (LET), which is a measure of the biological consequences of radiation exposure.  

Group photo as the IREM Flight model is officially handed over. From left: Miyazaki Eiji, Aida Mari, Hirose Takayuki (JAXA IREM), Iso Takumi, Horiguchi Kazuhiro (Meisei Electric), Nagamine Kenta (JAXA MMX Project)

The basic design for IREM began in March 2020 at Meisei Electric, the development manufacturer. After undergoing the design review, the construction of the engineering model (EM), and a number of development tests, the Post Qualification test Review (PQR) and Pre-Ship Review (PSR) were passed, and the development of the flight model (FM) was completed in March 2024. That same month, IREM was transported to the Mitsubishi Electric Corporation Kamakura Works where the spacecraft is being constructed. After functionality confirmed after transportation, IREM was officially handed over to JAXA.

The next step for IREM will be assembly into the MMX Spacecraft’s return module, and participate in the system integration tests for the spacecraft.

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

IREM Principal Investigator (PI) Miyazaki Eiji
Senior Researcher, Research Unit 1, JAXA Research and Development Directorate

Looking back, we faced many challenges in the development of IREM. Of these, the radiation irradiation test was particularly tough! We needed to use the irradiation test facility, and I spent many anxious days as time passed without any certainty as to whether we could find a time that fit with the development schedule. Fortunately, we were able to obtain two irradiation test opportunities during the 2023 fiscal year, and could fully demonstrate the performance of IREM. We are grateful to Meisei Electric and the Irradiation Test Facility for their efforts that have allowed to confidently send the instrument to the spacecraft system! IREM would also not have been completed without the efforts of the IREM development team members, Mr Hirose Takayuki, Dr Aida Mari and Mr Matsumoto Haruhisa. I’d like to take this opportunity to say thank you! We are confident that the observations with IREM will yield many results for both science and engineering – we are looking forward to it!

Equipment Development Lead Aida Mari
Research and Development Team, Research Unit 1, JAXA Research and Development Directorate

It was deeply moving to see the completed IREM Flight Model and to be able to celebrate this day. The development of IREM has been in full-swing since around 2020, and has passed through various phases such as design consideration, technology construction, and space environment testing. In each case, we re-learned what our predecessors had taught us: development equipment is not a straightforward process! No matter how well we were able to prove the performance on paper, there were always unexpected faults lurking when the development of equipment was put into operation and tested. At times, we felt overwhelmed by the unexpected issues, and each development stage seemed to be a series of difficulties and setbacks. But every time that happened, we held discussions to solve the problem, visited the manufacturers many times to get technical support, and became acutely aware of the challenges involved in creating equipment that can be used in an environment in space. Even when the situation felt like one bad thing after another, we are determined to improve the situation and move forward.

The JAXA IREM team were able to celebrate this day thanks to the help of everyone at Meisei Electric, who took care of everything from the technical studies to the manufacturing process, as well as the research institutes and the companies that provided our irradiation test equipment, and to the JAXA members who worked with us since the beginning of IREM. I once again realised the vast scale of spacecraft development and the importance of team work. Future tasks still lie ahead, such as installing IREM on the MMX spacecraft, conducting the ground tests with the whole spacecraft system, and constructing the equipment used in operation. We will face each issue before us with determination, and work at our best!

Meisei Electric (Manufacturer for IREM) Iso Takumi
System Development Group, Technology Department, Space Defense Division, Meisei Electric

I would like to thank the many people for their help in developing IREM. IREM has a high performance and multi-functional specifications compared to any previous space environment measurement equipment that we have developed, due to the large number of sensors and a wider measurement range. Adjustments, verification and calibration of each function in IREM required a lot of effort! Calibration requires the instrument to be actually irradiated with proton or heavy ion beams, but there are few facilities in Japan or overseas. We are very grateful to the National Institutes for Quantum and Radiological Science and Technology, the Tohoku University Cyclotron and Radioisotope Center, and the East Japan Heavy Particle Center, School of Medicine, Yamagata University, for providing valuable machine time. After overcoming many hurdles, we are extremely pleased that the handover and rendezvous are now successfully complete. While there are many more hurdles still to complete, such as ground testing of the complete MMX spacecraft, we are excited for the successful launch and being able to receive the data from IREM on the ground.

More information:

Yamagata University Press release (in Japanese): 東日本重粒子センターが火星衛星探査機搭載機器開発に貢献 ~株式会社ファムサイエンスと共同研究開始、宇宙航空研究開発機構(JAXA)も参加~(2023/11/2)