TP7

BepiColombo was launched on 20 October 2018 from the European spaceport Kourou in French Guyana and is now on route to Mercury to unveil Mercury’s secrets. BepiColombo with its state of the art and very comprehensive payload will perform measurements to increase our knowledge on the fundamental questions about Mercury’s evolution, composition, interior, magnetosphere, and exosphere. BepiColombo is a joint project between the European Space Agency (ESA) and the Japanese Aerospace Exploration Agency (JAXA) and consists of two orbiters, the Mercury Planetary Orbiter (MPO) and the Mercury Magnetospheric Orbiter (Mio). 

On its way BepiColombo will travel 18 times around the Sun until the spacecraft will be put into an polar orbit around Mercury. During its long way through the inner solar system, BepiColombo will perform nine flybys (one at Earth, two at Venus and six at Mercury). However, since the spacecraft is in a stacked configuration during the flybys only some of the instruments on both spacecraft will perform scientific observations. In addition there are plenty of opportunities for further science operations (testing Einstein’s theory during solar conjunctions, listening to gamma ray bursts, or investigation of the solar environment).

A status of the mission and instruments, science operations plans during cruise, and first results of measurements taken in the first three years since launch will be given.

How to cite: Benkhoff, J.: Cruise and flyby operations of BepiColombo – first results and planned activities, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-360, https://doi.org/10.5194/epsc2021-360, 2021.

BepiColombo is a joint mission of the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) to the planet Mercury, that was launched in October 2018 and it is due to arrive at Mercury in late 2025. It consists of two spacecraft, the Mercury Planetary Orbiter (MPO) built by ESA, and the Mercury Magnetospheric Orbiter (MMO) built by JAXA, as well as a Mercury Transfer Module (MTM) for propulsion built by ESA. The cruise phase to Mercury will last ~7 years and constitutes an exceptional opportunity for studying the evolution of the solar wind, solar transients, as well as for planetary science and planetary space weather. Some important aspects to consider during the cruise are the close distances to the Sun that BepiColombo will face, the near half-solar activity cycle that will cover, as well as the several flybys to Earth, Venus and Mercury that will perform. So far, BepiColombo has accomplished a flyby to Earth in April 2020 and a flyby to Venus in October 2020, with a second flyby to Venus programmed for August 2021 and the first Mercury flyby in October 2021.

This work focuses on the flyby to Earth, and in particular, on the radiation belt observations performed by several instruments onboard BepiColombo. The flyby occurred on 10 April 2020 under relatively steady solar wind conditions. BepiColombo crossed the outer radiation belt on the terrestrial dawn side when moving from the day side to the night side. It skimmed the inner radiation belt on the night side sector after dawn, and then crossed again the outer belt at night (behind the dusk terminator region). Two instruments onboard the MPO spacecraft were able to take measurements of the belts: the BepiColombo Radiation Monitor (BERM) and the Solar Intensity X-Ray and Particle Spectrometer (SIXS). In this work, we report the particle species, radiation and energies observed by these two instruments, as well as we perform a cross-calibration of their detections, which is an important activity in preparation for joint-observations of the Hermean environment. Moreover, using magnetic field observations from MPO-MAG, we also investigate the trajectory of the particles within the radiation belts. This work is complemented with data from other missions that give us the state of the terrestrial system and frame our observations into the right context. It includes data from Cluster-II, Themis, and Arase/ERG missions.

How to cite: Sanchez-Cano, B., Vainio, R., Pinto, M., Oleynik, P., Nakamura, R., Moissl, R., Miyoshi, Y., Marques, A., Lehtolainen, A., Korpela, S., Kilpua, E., Johnson, R., Huovelin, J., Heyner, D., Hajdas, W., Grande, M., Gonçalves, P., Esko, E., and Dandouras, I.: The terrestrial radiation belts as seen by BepiColombo during its flyby to Earth, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-200, https://doi.org/10.5194/epsc2021-200, 2021.

At the beginning of September 2020 ACE and BepiColombo spent several hours in an interesting magnetically connected configuration, while at the end of the same month Parker Solar Probe (PSP) and BepiColombo were radially aligned. Being PSP orbiting near 0.1 AU, BepiColombo near 0.6 AU, and ACE at 1 AU, these geometries are of particular interest for investigating the evolution of solar wind properties at different heliocentric distances by observing the same solar wind plasma parcels. 

In this contribution we use magnetic field observations from pairs of spacecraft to characterize both the topology of the magnetic field at different heliocentric distances (scalings and high-order statistics) and how it evolves when moving from near-Sun to far-Sun locations. We observe a breakdown of the statistical self-similar nature of the solar wind plasma due to an increase of the intermittency level when moving away from the Sun. These results support previous evidences on the radial dependence of solar wind scaling behavior and can open a novel framework for modeling magnetic field topological changes across the Heliosphere.

How to cite: Alberti, T., Milillo, A., Heyner, D., and Hadid, L. Z.: The solar wind between 0.1 and 1 AU: Parker Solar Probe - BepiColombo radial alignment and BepiColombo - ACE magnetic alignment, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-66, https://doi.org/10.5194/epsc2021-66, 2021.

Despite a long history of Venus observations, we still miss information about the spectral and solar phase angle dependences of the Venus dayside. Recently, the Venus atmosphere was found to undergo temporal variations [1-3]. But variability of scattering properties of the Venus disk is not yet quantified, and only a long-term average is known [4-6]. In Aug-Sep 2020 we performed a unique Venus dayside campaign (Fig. 1) by 3 spacecraft and 6 ground-based telescopes over a broad spectral range (45-1700 nm) (Fig. 2). During the cruise to Mercury, BepiColombo’s UV spectrometer PHEBUS conducted Venus faraway observations; at the same time, the UV camera on board Akatsuki Venus orbiter and Earth-bound telescope facilities obtained Venus data (Fig. 2). The campaign was successful, and we acquired data from three locations simultaneously. In this presentation, we will introduce the campaign and its latest analysis results. We plan for more campaigns in future to observe Venus dayside from various solar phase angle locations.

Fig 1. Relative locations of BepiColombo (blue), Akatsuki Venus orbiter (black), and the direction to the Earth (green arrow), when the Venus dayside observation campaign was conducted (28 Aug - 2 Sep 2020). The +X is assigned to the Sun. The grey curve shows the trajectory of BepiColombo in Aug-Nov 2020 (top). The enlarged plot in the bottom shows the trajectory of Akatsuki around  Venus on 28 Aug – 2 Sep. Red dots indicate the locations of BepiColombo and Akatsuki at 28 Aug 04:30 UT (BepiColombo is at 0.3 AU distance from Venus, and Akatsuki is at 0.34 million km distance) (Image credit: [7]).

Fig 2. Facilities participated the Venus dayside observation campaign in Aug-Sep 2020. From top left to clockwise: BepiColombo, Akatsuki, CAHA (3.5, 2.2, 1.23), STELLA, Perek telescope, T100, and Hisaki. (Image credit: ESA, JAXA, CAHA, STELLA, T100, Pereks telescope)

How to cite: Lee, Y. J. and the Venus Dayside Observation team: Venus dayside observation campaign performed by multiple space missions and ground-based facilities, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-637, https://doi.org/10.5194/epsc2021-637, 2021.

ISA (Italian Spring Accelerometer) is a high sensitivity, relative, mass-spring accelerometer. It flies as scientific payload on-board  the Mercury Planetary Orbiter (MPO), module of BepiColombo ESA mission to Mercury. The accelerometer is sensitive to any acceleration, greater than 2*10^-8 ms^-2Hz^-1/2, that changes  the spacecraft motion from a pure free fall: the, so called, Non Gravitational Perturbations (NGP). ISA data will be added, at Mercury, to the orbit determination estimation in order to help reconstructing the orbit and to make the MPO an a-posteriori free-fall satellite.

After the first commissioning phase, performed in between November 2018 - August 2019, and that allowed to verify the functionality of the instrument itself, the first direct verification of the correct behaviour of the system was carried out during the BepiColombo Earth Flyby. Indeed,  the spacecraft crossed the planet Earth shadow during the flyby and the direct Solar Radiation Pressure (SRP), the main contribution of NGP accelerations, dropped suddenly, marking a clear leap (gap)  in the gathered data. The scientific team compared, on the base of the satellite surface exposition and radiative characteristics, the observed “drop” in the acceleration, once removed  the on-board disturbances and inertial accelerations due to spacecraft rotations. In the talk, other ISA data recorded during the Earth Flyby are reported and expected signals for the upcoming Venus#2 Flyby and Mercury #1 Flyby are presented.  

How to cite: Santoli, F., Fiorenza, E., Lefevre, C., Lucchesi, D. M., Lucente, M., Magnafico, C., Peron, R., and De Filippis, U.: The high sensitivity accelerometer ISA during the BepiColombo spacecraft Earth flyby: data analysis, lessons learned, and expected signals for the next, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-755, https://doi.org/10.5194/epsc2021-755, 2021.

The Space environment is known to be populated by highly energetic particles. These particles originate from three main sources: (1) Galactic Cosmic Rays (GCRs), a low flux of protons (90%), heavy ions, and to some extent electrons, with energies up to 10²¹ eV, arriving from outside of the Solar System; (2) Solar Energetic Particles (SEPs), sporadic and unpredictable bursts of electrons, protons, and heavy ions, travelling much faster than the Space plasma, accelerated in Solar Flares and Coronal Mass Ejections; and (3) planetary trapped particles, a dynamic population of protons and electrons trapped around planetary magnetospheres first discovered at Earth by Van Allen. Solar activity is responsible for transient and long-term variation of the radiation environment. During periods of low activity, the GCR flux increases as a result of the lower heliospheric modulation exerted on charged particle from outside the solar system and the probability of SEP events decreases; vice-versa, during high activity, GCR fluxes decrease, and the probability of SEP events increases. Extreme Solar Events also affect the Earth’s magnetosphere and the radiation belts which can lead to ground-level enhancements. These three components of radiation in space combine into a hazardous environment for both manned and unmanned missions and are responsible for several processes in planetary bodies. Therefore, it is important to monitor and comprehend the dynamics of energetic particles in space. 

BepiColombo is the first mission of the European Space Agency to the Hermean System. It was launched in 2018 and will enter Mercury’s orbit in 2025 with the first flyby to Mercury planned for 2021. It is composed of two Spacecraft, ESA’s Mercury Planetary Orbiter (MPO) and JAXA’s Mercury Magnetospheric Orbiter (MMO). Both Spacecraft carry a rich suite of scientific instruments to study the planet geology, exosphere, and magnetosphere. In particular, the MPO spacecraft carries the BepiColombo Radiation Monitor (BERM), which is capable of measuring electrons with energies from ~100 keV to ~10 MeV, protons with energies from 1 MeV to ~200 MeV, and heavy ions with a Linear Energy Transfer from 1 to 50 MeV/mg/cm². While BERM is part of the mission housekeeping, it will provide valuable scientific data of the energetic particle population in interplanetary space and at Mercury. Because BERM is in operation during most of the cruise phase, it is able to detect and characterize SEP events. In fact, two events were already registered and will be included in a multi-spacecraft analysis.  

BERM is based on standard silicon stack detectors such as the SREM and the MFS. It consists of a single telescope stack with 11 Silicon detectors interleaved by aluminum and tantalum absorbers. Particle species and energies are determined by  charged particle track signals registered in the Si stack. Because of the limited bandwidth, particle events are processed in-flight before being sent to Earth. Particles are then assigned to 18 channels, five corresponding to electrons, eight to protons, and five to heavy ions. In this work, we will present the response of the 18 detector channels obtained by comparing Geant4 simulations with the BERM beam calibration data. The response functions are validated using measurements made during of the BepiColombo Earth flyby and during the cruise phase. Special focus is given  to the synergies between BERM and the Solar intensity X-ray and particle Spectrometer (SIXS) instrument signals. The latter measures electrons from ~50 keV to ~3 MeV and protons from ~1 to ~30 MeV. The availability of two instruments with overlapping energy ranges allows to validate and cross-calibrate their data, namely during Earth flyby at the radiation belts, and to maximize the scientific output of the mission. In fact, lessons learned during this joint analysis are expected to set the basis for a similar collaboration between the RADiation hard Electron Monitor (RADEM) and the Particle Environment Package (PEP) instruments aboard the future JUICE mission.

How to cite: Pinto, M., Gonçalves, P., Cardoso, C., Sanchez-Cano, B., Moissl, R., Vainio, R., Oleynik, P., Huovelin, J., Korpela, S., Lehtolainen, A., Grande, M., and Marques, A.: The BepiColombo Radiation Monitor, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-204, https://doi.org/10.5194/epsc2021-204, 2021.

The induced magnetosphere of Venus is created by the interaction of the solar wind and embedded interplanetary magnetic field with the exosphere and ionosphere of Venus. Solar Orbiter entered Venus’s magnetotail far downstream, > 70 Venus radii, of the planet and exited the magnetosphere over the north pole. This offered a unique view of the system over distances that were only flown through once by three other missions before, Mariner 10, Galileo and Bepi-Colombo. The large-scale structure and activity of the induced magnetosphere is studied as well as the high-frequency plasma waves both in the magnetosphere and in a limited region upstream of the planet where interaction with Venus’s exosphere is expected.  It is shown that Venus’s magnetotail is very active during the Solar Orbiter flyby. Structures such as flux ropes, and reconnection sites are encountered as well as a strongly overdraping of the magnetic field downstream of the bow shock and planet. High-frequency plasma waves (up to 6 times the local proton cyclotron frequency) are observed in the magnetotail, which are identified as Doppler-shifted proton cyclotron waves, whereas in the upstream solar wind these waves appear just below the proton cyclotron frequency (as expected) but are very patchy. The bow shock is quasi perpendicular, however, expected mirror mode activity is not found directly behind it; instead there is strong cyclotron wave power. This is most-likely caused by the relatively low plasma-beta  behind the bow shock. Much further downstream in the magnetosheath mirror mode of magnetic hole structures are identified. This presentation will take place after the second Venus flyby by Solar Orbiter and BepiColombo and Solar Orbiter on 9 and 10 August, respectively.

How to cite: Volwerk, M. and the Solar Orbiter Venus 1 MAG Team: Solar Orbiter’s first Venus Flyby: MAG observations of structures and waves associated with the induced Venusian magnetosphere, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-15, https://doi.org/10.5194/epsc2021-15, 2021.

On December 27, 2020, Solar Orbiter completed its first gravity assist manoeuvre of Venus. While this flyby was performed to provide the spacecraft with sufficient velocity to get closer to the Sun and observe its poles from progressively higher inclinations, the Radio and Plasma Wave (RPW) consortium, along with other operational in-situ instruments, had the opportunity to perform high cadence measurements and study the plasma properties in the induced magnetosphere of Venus. In this work we present an overview of the in situ observations performed by RPW, inside the induced magnetosphere of Venus, during this first encounter of Solar Orbiter.
These data allowed conclusive identification of various waves at low and higher frequencies than previously observed and detailed investigation regarding the structure of the induced magnetosphere of Venus. Furthermore, noting that prior studies were mainly focused on the magnetosheath region and could only reach 10-12 Venus radii (RV) down the tail, the particular orbit geometry of Solar Orbiter’s VGAM1, allowed the first investigation of the nature of the plasma waves continuously from the bow-shock to the magnetosheath, extending to ∼ 70 R V in the far distant tail region.

How to cite: Hadid, L. and the Solar Orbiter's RPW, MAG and EPD teams: Solar Orbiter’s first Venus flyby: observations from the Radio andPlasma Wave instrument, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-300, https://doi.org/10.5194/epsc2021-300, 2021.

On April 19th 2020 a CME was detected by Solar Orbiter at a heliocentric distance of 0.8 AU and was also observed in-situ on April 20th by both Wind and BepiColombo. During this time, BepiColombo had just completed a flyby of the Earth and therefore the longitudinal separation between BepiColombo and Wind was just 1.4°. The total longitudinal separation of Solar Orbiter and both spacecraft near the Earth was less than 5°, providing an excellent opportunity for a radial alignment study of the CME. We use the in-situ observations of the magnetic field at Solar Orbiter with those at Wind and BepiColombo to analyse the large-scale properties of the CME and compare results to those predicted using remote observations at STEREO-A, providing a global picture of the CME as it propagated from the Sun to 1 AU.

How to cite: Davies, E., Möstl, C., Owens, M., Weiss, A., Amerstorfer, T., Hinterreiter, J., Bauer, M., Bailey, R., Reiss, M., Forsyth, R., Horbury, T., O'Brien, H., Evans, V., Angelini, V., Heyner, D., Richter, I., Auster, H.-U., Magnes, W., Baumjohann, W., and Fischer, D. and the RAL Space STEREO HI Team: In-Situ Multi-Spacecraft and Remote Imaging Observations of the First CME Detected by Solar Orbiter and BepiColombo, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-533, https://doi.org/10.5194/epsc2021-533, 2021.

Cometary meteoroid streams (also referred to as trails) exist along the orbits of comets, forming fine structures of the interplanetary dust cloud. The streams consist predominantly of the largest cometary particles (with sizes of approximately (100 micrometer to 1 cm) which are ejected at low speeds and remain very close to the comet orbit for several revolutions around the Sun. 

The Interplanetary Meteoroid Environment for eXploration (IMEX) dust streams in space model (Soja et al., Astronomy & Astrophysics, 2015) is a universal model that simulates recently created cometary dust streams in the inner solar system, developed under ESA contract. IMEX is a physical model for dust dynamics and follows the orbital evolution of the streams of 420 comets. Particles are emitted when the comet is in the inner solar system, taking into account comet apparitions between the years 1700 and 2080. The dust ejection is described by an emission model, dust production rate and mass distribution covering the mass range from 10^-8 kg to 10^-2 kg (approximately corresponding to 100 micrometer to 1 cm particles). The dust production is calculated from the comet's absolute magnitude, the observed water production rate and dust-to-gas ratio. For each emitted particle, the trajectory is integrated individually including solar gravity, planetary perturbations as well as solar radiation pressure and 
Poynting-Robertson drag. The model calculates dust number density, flux and  velocity.

We apply the IMEX model to study comet stream traverses by the Ulysses spacecraft. Ulysses was launched in 1990 and, after a Jupiter swing-by in 1992, became the first interplanetary spacecraft orbiting the Sun on a highly inclined  trajectory with an inclination of 80 degrees. The spacecraft was equipped with an impact ionization dust detector which provided the longest  data set of continuous in situ dust measurements in interplanetary space existing to date, covering 17 years  from 1990 to 2007. In addition to the interplanetary dust complex, several dust populations were investigated with the Ulysses dust instrument in the past: interstellar dust sweeping through our solar system, streams of approximately 10 nanometer-sized dust particles emanating from Jupiter's volcanically active moon Io, as well as sub-micrometer-sized particles driven away from the Sun by solar radiation pressure (so-called beta particles). Here we study the detection conditions for cometary meteoroid streams with the dust detector on board the Ulysses spacecraft and present first results from our attempt to identify cometary stream particles in the measured dust data set. 

Acknowledgements: The IMEX Dust Streams in Space model was developed under ESA funding (contract 4000106316/12/NL/AF - IMEX).

How to cite: Krüger, H., Strub, P., and Grün, E.: Ulysses spacecraft data revisited: Detection of cometary meteoroid streams by following in situ dust impacts, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-68, https://doi.org/10.5194/epsc2021-68, 2021.

JUICE - JUpiter ICy moons Explorer - is the first large mission in the ESA Cosmic Vision 2015-2025 programme. The mission was selected in May 2012, and is now (May 2021) in the final stages of its integration and testing campaigns. Following its arrival at Jupiter in July 2031, JUICE will spend 4.2 years making detailed observations of Jupiter and three of the Galilean moons, Ganymede, Callisto and Europa.  We present here the plan of activities to be carried out during the interplanetary cruise phase.

1. Trajectory during the cruise phase

The mission will be launched from Kourou with an Ariane 5. The baseline launch window is between 26 August – 15 September 2022, with a backup launch slot in August 2023. The interplanetary transfer sequence relies on gravity assist manoeuvres with Venus, Earth and the Moon. The Jupiter orbit insertion will be performed in July 2031. The cruise phase officially starts after the end of the near-Earth commissioning (launch + 3 months) and ends six months before the Jupiter orbit insertion, when the nominal science mission begins.

The list of planetary gravity assists is given in Table 1:

2. Spacecraft and mission constraints during the cruise phase

The main limitations during the cruise phase are:

• Priority of operations in support of navigation and spacecraft safety, especially in the preparation of gravity assist manoeuvres, in particular the world premiere of Lunar-Earth gravity assist
• The thermal design of the spacecraft which imposes, for heliocentric distances lower than 1.34 AU, restricted pointing capabilities and limitations in the number of instruments that can operate simultaneously.
• Quiet Cruise baseline: Reduced number of ground contacts (one ground station pass per week except for planetary flybys).
• Operational constraint to minimize the use of the mass memory during Cruise to preserve unit lifetime, limiting the possibility to operate the instruments and store their data.
• Budgetary restrictions that result in small operation teams during this phase.

The baseline operations of the instruments are two one-week checkouts per year. It is expected that at least some of the observations will take place during the planetary flybys, with different possibilities still under study. The requests for operating the payload beyond this baseline will be carefully analyzed and agreed on a best-effort basis. The next section gives example of possible observations.

3. Potential scientific investigations to be performed during the cruise phase

Instrument operations during the cruise phase are always useful: they allow calibrating instruments in known environments (e.g. solar wind, Earth’s magnetosphere), checking possible interferences between instruments, they provide scientific results (sometimes not expected and outstanding, resulting in high standard publications) and attract public attention. During the long cruise phase of the JUICE mission, a number of scientific opportunities have been identified, beyond the obvious case of the planetary flybys. They include: solar wind campaigns, neutral atoms imaging in the heliosphere, measurement of Jovian escaping relativistic electrons, measurements of interplanetary dust, test of the general relativity around solar conjunctions, observation of the cosmological radio background, and an asteroid flyby (to be further studied).

4. JUICE teams activities during the cruise phase

The JUICE teams (mission operation center, science operations center, instrument teams, science working team, working groups, project scientist and mission manager) will be busy with numerous activities. A non-exhaustive list is given below:

• Spacecraft navigation and operations in the inner solar system, including planetary flybys and payload checkouts;
• Decision about an asteroid flyby (shortly after launch);
• Analysis of the cruise data, instrument calibration, scientific analysis, publication and archive;
• Refinement and agreement (three years before Jupiter orbit insertion) on the trajectory within the Jupiter system;
• Preparation of the science planning of the nominal mission and of the science analysis of the future data;
• Studying and preparing the coordination with ground-based and space observatories;
• Publication of a special issue with mission, instruments and science articles;
• Recruitment of guest investigators and of potentially additional interdisciplinary scientists;
• Continue the fruitful collaboration with the NASA Clipper teams.
• Conclusions

The JUICE cruise phase, despite its long duration (9 years), will be busy with many activities, with the goal of being fully ready to start the scientific observations from early 2031 onwards.

Figures

Figure 1: Evolution of distances (in AU) between the Sun, the Earth, Jupiter and JUICE as a function of time.

Figure 2: Overall cruise projected in the ecliptic frame

Figure 3: Lunar-Earth flyby in 2023

Figure 4: Illustration of the 300 km lunar flyby in 2023. The lunar and Earth disks are dark due the Sun position.

How to cite: Witasse, O., Altobelli, N., Andres, R., Atzei, A., Boutonnet, A., Budnik, F., Dietz, A., Erd, C., Evill, R., Lorente, R., Munoz, C., Pinzan, G., Scharmberg, C., Suarez, A., Tanco, I., Torelli, F., Torn, B., and Vallat, C. and the JUICE Science Working Team: JUICE (Jupiter Icy Moon Explorer): Plans for the cruise phase, Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-358, https://doi.org/10.5194/epsc2021-358, 2021.