1,2,2,1,1- 1Swedish Institute of Space Physics, Kiruna, Sweden (futaana@irf.se)
- 2Swedish Institute of Space Physics, Uppsala, Sweden
- 3KTH Royal Institute of Technology
- 4Luleå University of Technology
The 3DVI (3-D Velocity of Ions) sensors that are under development for the ESA M7 candidate M-MATISSE mission are designed to address two fundamental questions about the Martian plasma environment:
- How are thermal ions accelerated beyond escape velocity in the ionosphere?
- How is ion escape controlled? Is it source-limited or energy-limited?
To answer these questions, precise measurements of ion bulk parameters in the upper ionosphere, where the initial acceleration processes are ongoing, shall be conducted. Our dedicated low-energy ion sensor will regularly measure the ionospheric thermal ions for the first time at Mars.
Building upon the success of ASPERA-3 on Mars Express as well as other Mars missions, M-MATISSE's 3DVI measurements will provide insights into the Martian upper atmosphere. The simultaneous measurements from two spacecraft with full plasma suites onboard will address energy transfers from the solar wind to the ionosphere. This will allow us to monitor the ionospheric ions in detail, shedding light on the thermosphere-ionosphere coupling that governs the first acceleration of ionospheric ions, which eventually escape to space.
3DVI instrument is based on the well-established techniques of RPA (Retarding Potential Analyzer) and IDM (Ion Drift Meter). The instrument consists of two sensor heads, RPA and IDM. Both have fields-of-view of 45° (half cone), with their boresight directions pointing to the ram direction of the spacecraft. The RPA head is to determine the velocity distribution function along the line of sight by using retarding potential in front of the cathode plate. The IDM head determines the incoming ion directions (i.e., two angles) by measuring the current differences between the prepared cathodes of the sensor. The measurement principle has been used in various space missions since 60–70s, but 3DVI is optimized for the Martian upper ionosphere environment.
In this talk, we will present the scientific background for the 3DVI instrument and report its current design and development status.
How to cite: Futaana, Y., Shimoyama, M., Karlsson, S., Puccio, W., Berglund, M., Wecker, M., Eriksson, A., Andrews, D., Barabash, S., Holmstrom, M., Kim, K., Malatinszky, A., Menpara, N., Ohlsson, D., and Williamson, H.: How do ionospheric ions get escape energy at Mars? M-MATISSE/3DVI science and instrument, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–12 Sep 2025, EPSC-DPS2025-906, https://doi.org/10.5194/epsc-dps2025-906, 2025.
