Mission

JAXA's Martian Moons eXploration (MMX) Mission

The MMX spacecraft will travel to Mars and survey the red planet's two moons, Phobos and Deimos. The spacecraft will explore both moons and collect a sample from Phobos and bring that sample back to Earth. The MMX mission is currently in development, with launch planned for 2024, Mars system arrival in 2025, Mars system departure in 2028, and the Phobos sample arriving at Earth in 2029.

JAXA MMX website screenshot
Artist Rendering of MMX in space

MMX Exploring the Martian Moons. Artist's concept of the MMX spacecraft studying Phobos and Deimos, the moons of Mars.
Credit: JAXA

The JAXA MMX website contains the latest details of the mission.

The MEGANE Instrument

MEGANE is one instrument of the science payload of the MMX mission. For details on the full MMX instrument suite, visit the MMX science instrument website.

MEGANE is a gamma-ray and neutron spectrometer that builds on heritage from the MESSENGER GRS, and will utilize many aspects of the Psyche GRS that is currently in development for NASA's Psyche mission. The MEGANE GRS uses a high-purity germanium detector to provide state-of-the-art performance and sensitivity for the gamma-ray measurements. To operate, the germanium sensor is cooled to the cryogenic temperature of 90 K. The GRS sensor is surrounded by a plastic scintillator (called the anticoincidence shield) that both reduces background signals and provides measurements of high-energy neutrons. The MEGANE neutron spectrometer (NS) uses the same type of 3He neutron sensors used on NASA's Lunar Prospector mission to measure thermal and epithermal neutrons. The MEGANE readout electronics (known as the Data Processing Unit, or DPU) consolidates all the GRS and NS functions into a single unit, providing an efficient means to limit the instrument's overall mass. During operations, MEGANE's GRS and NS can operate independently, and the combined results from both the GRS and NS will be used to determine the chemical composition of Phobos.

Instrument Diagram

The MEGANE GRS uses aspects of the MESSENGER and Psyche gamma-ray instruments. The cryostat contains the germanium crystal, and is surrounded by the anticoincidence shield (ACS). Light signals created by the ACS are detected by the photomultiplier tube (PMT). (Credit: APL)

Instrument Diagram

The MEGANE NS uses 3He gas proportional sensors. One sensor is covered by a layer of cadium that blocks thermal neutrons causing that sensor to only measure epithermal (or medium energy) neutrons. The other sensor measures both thermal (or low-energy) and epithermal neutrons. (Credit: APL)