[P-PS04] Mercury Science and Exploration

[PPS04-05] Magnetic field measurement by BepiColombo MIO MGF during cruising and prospects for the observations at Mercury

*Ayako Matsuoka¹, Wolfgang Baumjohann², Werner Magnes², Hans-Ulrich Auster³, Daniel Schmid², David Fischer², Yasuhito Narita³, Rumi Nakamura², Manabu Shinohara⁴, Yoshimasa Tanaka⁵, Akiko Fujimoto⁶, Masaki Matsushima⁷, Kazuhiro Yamamoto⁸ (1.Kyoto University, 2.The Space Research Institute, OeAW, 3.Technical University of Braunschweig, 4.Kagoshima National College of Technology, 5.National Institute of Polar Research, 6.Kyushu Institute of Technology, 7.Institute of Science Tokyo, 8.Nagoya University)

Keywords:magnetometer, Mercury, BepiColombo

By BepiColombo mission we aim to understand the essential properties of the Herman intrinsic magnetic field and physical process occurring in the Herman magnetosphere. To achieve our aims, we installed a dual magnetometer on Mercury Magnetospheric Orbiter (MMO, MIO), outboard (MGF-O) and inboard (MGF-I) magnetometers, which are developed by European and Japanese groups, respectively. One of the purposes of dual magnetometer is the redundancy, in addition to the separation of the artificial magnetic signal from the natural signal. The two magnetometers are operated independently for the complete redundancy, while the onboard software for the data processing and the output data format are exactly same. Since the telemetry budget for the MIO MGF is strictly limited, the onboard software pre-processes the data (e.g., fitting to the spin-period sinusoidal variation and definition of the least-significant-bit according to the field intensity) and effectively compresses the data before transmitting to the Earth.
BepiColombo was launched in October 2018 and is now cruising in the interplanetary space. It will be inserted into the orbit around Mercury in November 2026 after flybys with the Earth, Venus, and Mercury. The MGF-O and MGF-I sensors are placed at the tip and in the middle, respectively, of the 5m long MAST deployed from the MIO spacecraft. During the cruising, the MAST is stored in a container, and the two sensors are located nearby the surface of the spacecraft. Although the magnetic noise radiated from the MIO spacecraft is well restrained, the sensors are considerably interfered by the components on MIO. Moreover, since MIO, MPO (Mercury Planetary Orbiter) and a transfer module (MTM) are stacked during the cruising, MGF sensors suffer strong magnetic noise from MPO and MTM as well. Nevertheless both MGF-O and MGF-I are operated and measure the magnetic fields at flyby events. Some of the interference noise emerge as the difference between MGF-O and MGF-I data, and can be distinguished also by the comparison with the magnetic field data from MPO. The MGF team is making much efforts to evaluate and remove the interference noise so that we could identify natural phenomena in the space around planets.
In parallel, we are currently examining methods and specifications for processing and archiving the magnetic field data from MIO MGF.
In this talk we overview the operation of and data from MIO MGF during the crcuising period, and discuss the perspectives about the observation in the orbits around Mercury.