9:30 AM - 9:45 AM
[PEM16-09] Development of the calibration method for the radiation instruments onboard Mercury explorer BepiColombo and its application to the inner heliosphere exploration
Plasma originating from coronal mass ejections (CMEs) and solar energetic particles (SEPs) harm satellites and ground infrastructure when they reach the Earth. Therefore, there is a great demand, not only academically but also socially, for understanding the propagation process of these particles in the inner heliosphere. However, due to the large difference in gravitational potentials, there have been a few direct observations by spacecraft in the inner solar system. In recent years, due to the development of orbital engineering, several spacecraft such as the Mercury probe BepiColombo and the solar probe Parker Solar Probe have been deployed to the inner heliosphere at the same time. These spacecraft not only fill in the observation gaps in the heliosphere but also provide an excellent opportunity to investigate the radial and radial evolution of solar ejecta through multi-point observations (Hadid et al., 2021).
In this study, we are calibrating data from the "Solar Particle Monitor (SPM)," a radiation maintenance instrument onboard the Mercury spacecraft BepiColombo. Although the SPM is not a scientific instrument, it can observe particles in a higher energy band than other particle detectors. SPM is not a scientific instrument, but it is suitable for observing phenomena related to high-energy particles such as galactic cosmic rays because it can observe higher energy bands than other particle detectors. However, the data that can be obtained are the lost energy and counts that particles leave behind when they pass through the detector, so it is necessary to calculate the physical information of the original particles backward by simulation to use them for analysis. We built a simple model of the SPM using the radiation simulation tool "Geant4" and defined an Al box outside the SPM model to reproduce the radiation shielding effect from the structure of the spacecraft. Next, to confirm the validity of the model, the environment during BepiColombo's earth swing-by through the earth radiation belt was reproduced in the simulation, and the model counts were compared with the actual measurements. Since the Dst index on the day of the earth swing-by remained around 0 nT and the environment was relatively calm, it can be approximated that the radiation environment is similar even if the orbits are different and the L values are the same. Therefore, the simulation used the measured data of the same L-value as BepiColombo from the radiation data acquired by the Arase satellite on the same day to reproduce the surrounding environment. Based on the results of this simulation, the thickness of the Al box for reproducing the shielding effect in each direction was determined to minimize the difference between the measured and modeled counts. Finally, we applied the method of Park et al. (2021) to derive the inverse matrix connecting the observed particle energy spectrum and the incident energy spectrum and established a method to recover the original particle information from the SPM data. In the presentation, we will also discuss the application of this method to the analysis of the Forush Decrease, a phenomenon in which CME emissions shield galactic cosmic rays.
This study suggests the possibility of applying this method to scientific applications of maintenance equipment commonly installed on spacecraft. If this method is widely applied, it is expected not only to expand the range of scientific results of spacecraft without dedicated instruments but also to expand the solar observation network deployed in the heliosphere.
In this study, we are calibrating data from the "Solar Particle Monitor (SPM)," a radiation maintenance instrument onboard the Mercury spacecraft BepiColombo. Although the SPM is not a scientific instrument, it can observe particles in a higher energy band than other particle detectors. SPM is not a scientific instrument, but it is suitable for observing phenomena related to high-energy particles such as galactic cosmic rays because it can observe higher energy bands than other particle detectors. However, the data that can be obtained are the lost energy and counts that particles leave behind when they pass through the detector, so it is necessary to calculate the physical information of the original particles backward by simulation to use them for analysis. We built a simple model of the SPM using the radiation simulation tool "Geant4" and defined an Al box outside the SPM model to reproduce the radiation shielding effect from the structure of the spacecraft. Next, to confirm the validity of the model, the environment during BepiColombo's earth swing-by through the earth radiation belt was reproduced in the simulation, and the model counts were compared with the actual measurements. Since the Dst index on the day of the earth swing-by remained around 0 nT and the environment was relatively calm, it can be approximated that the radiation environment is similar even if the orbits are different and the L values are the same. Therefore, the simulation used the measured data of the same L-value as BepiColombo from the radiation data acquired by the Arase satellite on the same day to reproduce the surrounding environment. Based on the results of this simulation, the thickness of the Al box for reproducing the shielding effect in each direction was determined to minimize the difference between the measured and modeled counts. Finally, we applied the method of Park et al. (2021) to derive the inverse matrix connecting the observed particle energy spectrum and the incident energy spectrum and established a method to recover the original particle information from the SPM data. In the presentation, we will also discuss the application of this method to the analysis of the Forush Decrease, a phenomenon in which CME emissions shield galactic cosmic rays.
This study suggests the possibility of applying this method to scientific applications of maintenance equipment commonly installed on spacecraft. If this method is widely applied, it is expected not only to expand the range of scientific results of spacecraft without dedicated instruments but also to expand the solar observation network deployed in the heliosphere.