Thematic group: PEPS
Scientific Leader: Vincent Génot
Main OSU: Observatoire de Paris

Description / Background

NASA’s Magnetospheric Multiscale (MMS) mission was launched in March 2015. The mission concept consists of 4 identical, comprehensive and state-of-the-art instrumentation sets to study the process of magnetic reconnection in the near-Earth environment: a collision-less plasma. The mission profile comprises 3 main orbital phases (Figure 1) to explore the key regions of the terrestrial magnetosphere: the dayside and flank magnetopause, as well as the near- and mid-tail regions on the nightside (between 10 and 30 Earth radii).

Orbit of the MMS spacecraft in the terrestrial magnetosphere during the different phases of the mission.

Scientific Objectives

The prime improvement of the MMS mission resides in the extremely high temporal resolution of the experiments, and in particular that of the particle instruments (30 ms and 150 ms to measure the electron and ion distribution functions, respectively). This was the main advancement at stake since past missions (with typically 100 times lower resolutions) had shown the necessity for such higher resolutions in order to resolve the details of boundaries and the dynamics of processes that take place in the magnetosphere. In addition, the inter-spacecraft separations can be varied over the course of the mission, and all the way down to 7 km in order to study the smallest scales in the plasma. Such measurement capabilities constitute a major lead forward in our ability to study and understand the key physical mechanisms that control the dynamics of collisionless astrophysical plasmas such as magnetic reconnection, in the first place, but also wave-particle interactions, turbulence, current sheet instabilities… The processes at hand are universal (they are relevant to solar eruptions, coronal heating, and astrophysical plasma accelerations among others), and so are the numerous results obtained thus far.

Involvement of IRAP

IRAP has early been involved in the MMS mission, with the provision and calibration of the set of detectors (micro-channel plates; MCP) for the ion instruments of the FPI (Fast Plasma Investigation) consortium, under the responsibility of the Goddard Space Flight Center (NASA) and in collaboration with JAXA (Japan). A total of 32 sets of detectors (with 8 measurement heads per satellite) is onboard the four spacecraft and all function nominally.

The group at IRAP working on MMS is since 2015 very involved in the data calibration phase and in the support to the scientific exploitation of the dataset, which relies on two key aspects: (i) multipoint data analysis methods (with heritage from Cluster and THEMIS), nad (ii) the development of modeling and numerical simulations, which are both indispensable tools for the interpretation for MMS observations. MMS data analysis has been extremely fruitful since launch, with numerous publications involving IRAP.


MMS is a NASA mission, with a number of instrumental and scientific partnerships with other national space agencies, with in particular CNES in France or JAXA in Japan in the context of the FPI instrument suite.