In order to be useful for scientific analysis, the raw magnetic field data delivered by the BepiColombo Planetary Magnetometer must first be cleaned from stray magnetic fields originating from the spacecraft itself. This is especially important during the cruise phase, when the magnetic field instrument is still in the stowed position, close to various artificial magnetic field sources. The method we employ to remove these disturbances is a further development of the Maximum Variance Gradiometer technique already in use for cleaning the magnetic field data measured by the GeoKompsat-2A geostationary satellite. The main improvement over the above mentioned technique is the use of an intermediate non-orthogonal reference system which allows for decoupling of multiple disturbances. Here we describe the method and present the results of its application to the last Mercury flyby.

On 10 August 2021, the Mercury-bound BepiColombo spacecraft performed its second fly-by of Venus and provided a short-lived observation of its induced magnetosphere. Here we report results recorded by the Mass Spectrum Analyzer on board Mio, which reveal the presence of cold O+ and C+ with an average total flux of similar to 4 +/- 1 x 10(4) cm(-2) s(-1) at a distance of about six planetary radii in a region that has never been explored before. The ratio of escaping C+ to O+ is at most 0.31 +/- 0.2, implying that, in addition to atomic O+ ions, CO group ions or water group ions may be a source of the observed O+. Simultaneous magnetometer observations suggest that these planetary ions were in the magnetosheath flank in the vicinity of the magnetic pileup boundary downstream. These results have important implications regarding the evolution of Venus's atmosphere and, in particular, the evolution of water on the surface of the planet.

We estimate the global impact of storms on the global structure and dynamics of the night side plasma sheet from observations by the NASA mission Time History of Events and Macroscale Interactions during Substorms (THEMIS). We focus on an intense storm occurring in December 2015 triggered by interplanetary coronal mass ejections (ICMEs). It starts with a storm sudden commencement (SSC) phase (SYM-H similar to +50 nT) followed by a growth phase (SYM-H similar to-188 nT at the minimum) and then a long recovery phase lasting several days. We investigate THEMIS observations when the spacecraft were located in the midnight sector of the plasma sheet at distances typically between 8 and 13 Earth's radii. It is found that the plasma sheet has been globally compressed up to a value of about similar to> 4 nPa during the SSC and main phases, that is, 8 times larger than its value during the quiet phase before the event. This compression occurs during periods of high dynamic pressure in the ICME (20 nPa) about one order of magnitude larger than its value in the pristine solar wind. We infer a global increase of the lobe magnetic field from 30 to 100 nT, confirmed by THEMIS data just outside the plasma sheet. During the SSC and main phases, the plasma sheet is found thinner by a factor of 2 relative to its thickness at quiet times, while the Tsyganenko T96 magnetic field model shows very stretched magnetic field lines from inner magnetospheric regions toward the night side. During the recovery phase, whereas the interplanetary pressure has dropped off, the plasma sheet tends to gradually recover its quiet phase characteristics (pressure, thickness, magnetic configuration, etc.) during a long recovery phase of several days.

On 2022 February 15–16, multiple spacecraft measured one of the most intense solar energetic particle (SEP) events observed so far in Solar Cycle 25. This study provides an overview of interesting observations made by multiple spacecraft during this event. Parker Solar Probe (PSP) and BepiColombo were close to each other at 0.34–0.37 au (a radial separation of ∼0.03 au) as they were impacted by the flank of the associated coronal mass ejection (CME). At about 100° in the retrograde direction and 1.5 au away from the Sun, the radiation detector on board the Curiosity surface rover observed the largest ground-level enhancement on Mars since surface measurements began. At intermediate distances (0.7–1.0 au), the presence of stream interaction regions (SIRs) during the SEP arrival time provides additional complexities regarding the analysis of the distinct contributions of CME-driven versus SIR-driven events in observations by spacecraft such as Solar Orbiter and STEREO-A, and by near-Earth spacecraft like ACE, SOHO, and WIND. The proximity of PSP and BepiColombo also enables us to directly compare their measurements and perform cross-calibration for the energetic particle instruments on board the two spacecraft. Our analysis indicates that energetic proton measurements from BepiColombo and PSP are in reasonable agreement with each other to within a factor of ∼1.35. Finally, this study introduces the various ongoing efforts that will collectively improve our understanding of this impactful, widespread SEP event.

ESA’s Comet Interceptor mission is a low budget, fast track mission to a dynamically new comet (DNC). As a DNC enters the inner solar system for the first time, it is expected to feature strong activity and to display a fluid-scale plasma environment, rather than the kinetic-scale environment encountered at weakly active objects such as 67P. In situ characterization of this plasma environment is therefore one of the main mission objectives and is the object of the Dust-Fields-Plasma instrument, a suite of sensors for the measurement of the dust, the plasma populations, and the magnetic and electric fields and waves, with the field sensors being mounted on booms, all within strict mass, power, and budget constraints. In this context a sensor has been developed that harbors a fluxgate magnetometer at the center of a hollow spherical Langmuir probe. Precautions have been taken to minimize the possible interference between both, while at the same time being very lightweight. An engineering model has been built, tested and characterized in detail. Together with a companion Langmuir probe and an additional magnetometer in gradiometer configuration, the probe-magnetometer combination (COMPLIMENT + FGM) provides data regarding magnetic and electric fields and waves, total ion and electron densities and electron temperature, as well as the ambient nanodust population. It also offers reference data for the other sensors, such as magnetic field direction, spacecraft potential and total plasma density at high cadence, and integrated EUV flux.

We analyze data from multiple flybys by the Solar Orbiter, BepiColombo, and Parker Solar Probe (PSP) missions to study the interaction between Venus' plasma environment and the solar wind forming the induced magnetosphere. Through examination of magnetic field and plasma density signatures we characterize the spatial extent and dynamics of Venus' magnetotail, focusing mainly on boundary crossings. Notably, we observe significant differences in boundary crossing location and appearance between flybys, highlighting the dynamic nature of Venus' magnetotail. In particular, during Solar Orbiter's third flyby, extreme solar wind conditions led to significant variations in the magnetosheath plasma density and magnetic field properties, but the increased dynamic pressure did not compress the magnetotail. Instead, it is possible that the increased EUV flux at this time rather caused it to expand in size. Key findings also include the identification of several far downstream bow shock (BS), or bow wave, crossings to at least 60 RV ${\mathrm{R}}_{V}$ (1 RV ${\mathrm{R}}_{V}$ = 6,052 km is the radius of Venus), and the induced magnetospheric boundary to at least similar to ${\sim} $ 20 RV ${\mathrm{R}}_{V}$. These crossings provide insight into the extent of the induced magnetosphere. Pre-existing models from Venus Express were only constrained to within similar to ${\sim} $ 5 RV ${\mathrm{R}}_{V}$ of the planet, and we provide modifications to better fit the far-downstream crossings. The new model BS is now significantly closer to the central tail than previously suggested, by about 10 RV ${\mathrm{R}}_{V}$ at 60 RV ${\mathrm{R}}_{V}$ downstream. We studied data from the missions Solar Orbiter, BepiColombo, and Parker Solar Probe to understand Venus' magnetotail. We focused on how Venus' magnetic environment interacts with the solar wind to create its magnetosphere. By looking at magnetic fields and plasma density, we figured out the size and movement of Venus' magnetotail, and found where its boundaries are. We noticed that these boundaries change a lot between missions, showing that Venus' magnetotail is very dynamic. Our main discoveries include finding boundary crossings like the bow shock 60 times Venus' radius downstream, and the magnetospheric boundary about 20 times Venus' radius downstream. This helps us understand how far the magnetosphere extends and improve our models of its shape. We also saw that the solar wind affects the magnetotail: during one mission, even though the solar wind was strong, it didn't squish the magnetotail; instead, it made it bigger because of increased solar radiation. Venus' magnetotail is observed during nine spacecraft flybys revealing a dynamic structure reaching at least 60 RV downstream An improved bow shock model is presented for the deep tail region The pre-existing model of the induced magnetospheric boundary is valid downstream to at least 20 RV

Here we describe the novel, multi-point Comet Interceptor mission. It is dedicated to the exploration of a little-processed long-period comet, possibly entering the inner Solar System for the first time, or to encounter an interstellar object originating at another star. The objectives of the mission are to address the following questions: What are the surface composition, shape, morphology, and structure of the target object? What is the composition of the gas and dust in the coma, its connection to the nucleus, and the nature of its interaction with the solar wind? The mission was proposed to the European Space Agency in 2018, and formally adopted by the agency in June 2022, for launch in 2029 together with the Ariel mission. Comet Interceptor will take advantage of the opportunity presented by ESA’s F-Class call for fast, flexible, low-cost missions to which it was proposed. The call required a launch to a halo orbit around the Sun-Earth L2 point. The mission can take advantage of this placement to wait for the discovery of a suitable comet reachable with its minimum V capability of 600 ms^-1 . Comet Interceptor will be unique in encountering and studying, at a nominal closest approach distance of 1000 km, a comet that represents a near-pristine sample of material from the formation of the Solar System. It will also add a capability that no previous cometary mission has had, which is to deploy two sub-probes – B1, provided by the Japanese space agency, JAXA, and B2 – that will follow different trajectories through the coma. While the main probe passes at a nominal 1000 km distance, probes B1 and B2 will follow different chords through the coma at distances of 850 km and 400 km, respectively. The result will be unique, simultaneous, spatially resolved information of the 3-dimensional properties of the target comet and its interaction with the space environment. We present the mission’s science background leading to these objectives, as well as an overview of the scientific instruments, mission design, and schedule.

The magnetic orientation of coronal mass ejections (CMEs) is of great importance to understand their space weather effects. Although many evidences suggest that CMEs can undergo significant rotation during the early phases of evolution in the solar corona, there are few reports that CMEs rotate in the interplanetary space. In this work, we use multi-spacecraft observations and a numerical simulation starting from the lower corona close to the solar surface to understand the CME event on 2021 December 4, with an emphatic investigation of its rotation. This event is observed as a partial halo CME from the back side of the Sun by coronagraphs, and reaches the BepiColombo spacecraft and the MAVEN/Tianwen-1 as a magnetic flux rope-like structure. The simulation discloses that in the solar corona the CME is approximately a translational motion, while the interplanetary propagation process evidences a gradual change of axis orientation of the CME's flux rope-like structure. It is also found that the downside and the right flank of the CME moves with the fast solar wind, and the upside does in the slow-speed stream. The different parts of the CME with different speeds generate the nonidentical displacements of its magnetic structure, resulting in the rotation of the CME in the interplanetary space. Furthermore, at the right flank of the CME exists a corotating interaction region (CIR), which makes the orientation of the CME alter, and also deviates from its route due to the CME. These results provide new insight on interpreting CMEs' dynamics and structures during their travelling through the heliosphere.

The magnetic orientation of coronal mass ejections (CMEs) is of great importance to understand their space weather effects. Although plenty of evidence suggests that CMEs can undergo significant rotation during the early phases of evolution in the solar corona, there are few reports that CMEs rotate in the interplanetary space. In this work, we use multispacecraft observations and a numerical simulation starting from the lower corona close to the solar surface to understand the CME event on 2021 December 4, with an emphatic investigation of its rotation. This event is observed as a partial halo CME from the back side of the Sun by coronagraphs and reaches the BepiColombo spacecraft and the Mars Atmosphere and Volatile EvolutioN/Tianwen-1 as a magnetic flux-rope-like structure. The simulation discloses that in the solar corona the CME is approximately a translational motion, while the interplanetary propagation process evidences a gradual change of axis orientation of the CME's flux-rope-like structure. It is also found that the downside and the right flank of the CME moves with the fast solar wind, and the upside does in the slow-speed stream. The different parts of the CME with different speeds generate the nonidentical displacements of its magnetic structure, resulting in the rotation of the CME in the interplanetary space. Furthermore, at the right flank of the CME exists a corotating interaction region, which makes the orientation of the CME alter and also deviates from its route due to the CME. These results provide new insight into interpreting CMEs' dynamics and structures during their traveling through the heliosphere.

The main goal of ESA’s F-1 class Comet Interceptor mission is to characterise, for the first time, a long period comet; preferably a dynamically-new or an interstellar object. The main spacecraft, will have its trajectory outside of the inner coma, whereas two sub-spacecrafts will be targeted inside the inner coma, closer to the nucleus. The flyby of such a comet will offer unique multipoint measurement opportunity to study the comet's dusty and ionised environment in ways exceeding that of the previous cometary missions, including Rosetta. The Dust Field and Plasma (DFP) instruments located on both the main spacecraft A and on the sub-spacecraft B2, is a combined experiment dedicated to the in situ, multi-point study of the multi-phased ionized and dusty environment in the coma of the target and its interaction with the surrounding space environment and the Sun. The DFP instruments will be present in different configurations on the Comet Interceptor spacecraft A and B2. To enable the measurements on spacecraft A, the DFP is composed of 5 sensors; Fluxgate magnetometer DFP-FGM-A, Plasma instrument with nanodust and E-field measurements capabilities DFP-COMPLIMENT, Electron spectrometer DFP-LEES, Ion and energetic neutrals spectrometer DFP-SCIENA and Dust detector DFP-DISC. On board of spacecraft B2 the DFP is composed of 2 sensors: Fluxgate magnetometer DFP-FGM-B2 and Cometary dust detector DFP-DISC. The DFP instrument will measure magnetic field, the electric field, plasma parameters (density, temperature, speed), the distribution functions of electrons, ions and energetic neutrals, spacecraft potential, mass, number and spatial density of cometary dust particles and the dust impacts. The full set of DFP sensors will allow to model the comet plasma environment and its interaction with the solar wind. It will also allow to describe the complex physical processes including wave particle interaction in dusty cometary plasma.

A comet flyby, like the one planned for ESA’s Comet Interceptor mission, places stringent requirements on spacecraft resources. To plan the time line of in situ plasma and neutral gas observations during the flyby, the size of the comet magnetosphere and neutral coma must be estimated well. For given solar irradiance and solar wind conditions, comet composition, and neutral gas expansion speed, the size of gas coma and magnetosphere during the flyby can be estimated from the gas production rate and the flyby geometry. Combined with flyby velocity, the time spent in these regions can be inferred and a data acquisition plan can be elaborated for each instrument, compatible with the limited data storage capacity. The sizes of magnetosphere and gas coma are found from a statistical analysis based on the probability distributions of gas production rate, flyby velocity, and solar wind conditions. The size of the magnetosphere as measured by bow shock standoff distance is 105–106 km near 1au in the unlikely case of a Halley-type target comet, down to a nonexistent bow shock for targets with low activity. This translates into durations up to 103–104 seconds. These estimates can be narrowed down when a target is identified far from the Sun, and even more so as its activity can be predicted more reliably closer to the Sun. Plasma and neutral gas instruments on the Comet Interceptor main spacecraft can monitor the entire flyby by using an adaptive data acquisition strategy in the context of a record-and-playback scenario. For probes released from the main spacecraft, the inter-satellite communication link limits the data return. For a slow flyby of an active comet, the probes may not yet be released during the inbound bow shock crossing.

Aims. We derive electron density and temperature from observations obtained by the Mercury Electron Analyzer on board Mio during the cruise phase of BepiColombo while the spacecraft is in a stacked configuration. Methods. In order to remove the secondary electron emission contribution, we first fit the core electron population of the solar wind with a Maxwellian distribution. We then subtract the resulting distribution from the complete electron spectrum, and suppress the residual count rates observed at low energies. Hence, our corrected count rates consist of the sum of the fitted Maxwellian core electron population with a contribution at higher energies. We finally estimate the electron density and temperature from the corrected count rates using a classical integration method. We illustrate the results of our derivation for two case studies, including the second Venus flyby of BepiColombo when the Solar Orbiter spacecraft was located nearby, and for a statistical study using observations obtained to date for distances to the Sun ranging from 0.3 to 0.9 AU. Results. When compared either to measurements of Solar Orbiter or to measurements obtained by HELIOS and Parker Solar Probe, our method leads to a good estimation of the electron density and temperature. Hence, despite the strong limitations arising from the stacked configuration of BepiColombo during its cruise phase, we illustrate how we can retrieve reasonable estimates for the electron density and temperature for timescales from days down to several seconds.

Exploiting the Alfvénic structures of the solar wind is an established method for calibrating spaceborne magnetometers. However, not every statistical property of Alfvén waves follows a uniform distribution, so calibration accuracy in certain sensor directions may be significantly affected by the choice of the data set used. This work examines the statistical properties of Alfvénic disturbances and other structures of the solar wind in a wide range of spatial and temporal scales using data from the current BepiColombo mission, now in the inner solar system, the lunar and Earth-bound satellites of the THEMIS and ARTEMIS missions, and the Earth-bound MMS mission. The influence of the data selection on calibration is characterized and quantified. We benefit from the fact that the magnetometers of the above-mentioned missions have been partially calibrated by independent methods, using the spacecraft spin or alternative observations of the total magnetic field.

A nanolander (CALICUT) with a total mass of about 10 kg was proposed in response to the CNSA (China National Space Administration) Announcement of Op-portunity (AO) for an Asteroid Exploration Mission (AEM) by a joint European-Chinese team to operate on an active asteroid in the main belt. CALICUT is a further development of the MASCOT lander that flew on the HAYABUSA2 mission to asteroid Ryugu. The nanolander was designed with mobility and autonomy capabilities. It will be able to operate for at least 6 weeks to measure the physical, morphological and compositional properties of the target. The data can be used to derive answers to scientific questions, such as what drives activity on active asteroids, and identify similarities and differences between inactive asteroids and classical comets. CALICUT carries a payload of four scientific instruments with a total mass of about 2 kg to provide unique measurements that can only be done directly on the surface.

Context. A solar eruption on 17 April 2021 produced a widespread Solar Energetic Particle (SEP) event that was observed by five longitudinally well-separated observers in the inner heliosphere at heliocentric distances of 0.42 to 1 au: BepiColombo, Parker Solar Probe, Solar Orbiter, STEREO A, and near-Earth spacecraft. The event produced relativistic electrons and protons. It was associated with a long-lasting solar hard X-ray flare and a medium fast Coronal Mass Ejection (CME) with a speed of 880 km/s driving a shock, an EUV wave as well as long-lasting radio burst activity showing four distinct type III burst. Methods. A multi-spacecraft analysis of remote-sensing and in-situ observations is applied to attribute the SEP observations at the different locations to the various potential source regions at the Sun. An ENLIL simulation is used to characterize the interplanetary state and its role for the energetic particle transport. The magnetic connection between each spacecraft and the Sun is determined. Based on a reconstruction of the coronal shock front we determine the times when the shock establishes magnetic connections with the different observers. Radio observations are used to characterize the directivity of the four main injection episodes, which are then employed in a 2D SEP transport simulation. Results. Timing analysis of the inferred SEP solar injection suggests different source processes being important for the electron and the proton event. Comparison among the characteristics and timing of the potential particle sources, such as the CME-driven shock or the flare, suggests a stronger shock contribution for the proton event and a more likely flare-related source of the electron event. Conclusions. We find that in this event an important ingredient for the wide SEP spread was the wide longitudinal range of about 110 degrees covered by distinct SEP injections.

Context. The first BepiColombo Mercury flyby offered the unique opportunity to simultaneously characterize the plasma and the magnetic field properties of the solar wind in the vicinity of the innermost planet of the Solar System (0.4 AU). Aims. In this study, we use plasma observations by SERENA/PICAM and magnetic field measurements by MPO-MAG to characterize the source with intermittent features (with a timescale of a few minutes) at ion energies above 1 keV observed in the solar wind upstream of Mercury. Methods. The solar wind properties have been investigated by means of low-resolution magnetic field (1 s) and plasma (64 s) data. The minimum variance analysis and the Lundquist force-free model have been used. Results. The combined analyses demonstrate that the intermittent ion features observed by PICAM at energies above 1 keV can be associated with the passage of an interplanetary magnetic flux rope. We also validate our findings by means of Solar Orbiter observations at a larger distance (0.6 AU). Conclusions. The core of an interplanetary magnetic flux rope, hitting BepiColombo during its first Mercury flyby, produced high-energy (> -pagination1 keV) intermittent-like particle acceleration clearly distinct from the background solar wind, while at the edges of this interplanetary structure compressional low-energy fluctuations have also been observed.

Despite the growing importance of planetary Space Weather forecasting and radiation protection for science and robotic exploration and the need for accurate Space Weather monitoring and predictions, only a limited number of spacecraft have dedicated instrumentation for this purpose. However, every spacecraft (planetary or astronomical) has hundreds of housekeeping sensors distributed across the spacecraft, some of which can be useful to detect radiation hazards produced by solar particle events. In particular, energetic particles that impact detectors and subsystems on a spacecraft can be identified by certain housekeeping sensors, such as the Error Detection and Correction (EDAC) memory counters, and their effects can be assessed. These counters typically have a sudden large increase in a short time in their error counts that generally match the arrival of energetic particles to the spacecraft. We investigate these engineering datasets for scientific purposes and perform a feasibility study of solar energetic particle event detections using EDAC counters from seven European Space Agency Solar System missions: Venus Express, Mars Express, ExoMars-Trace Gas Orbiter, Rosetta, BepiColombo, Solar Orbiter, and Gaia. Six cases studies, in which the same event was observed by different missions at different locations in the inner Solar System are analyzed. The results of this study show how engineering sensors, for example, EDAC counters, can be used to infer information about the solar particle environment at each spacecraft location. Therefore, we demonstrate the potential of the various EDAC to provide a network of solar particle detections at locations where no scientific observations of this kind are available.

Context. Magnetic holes are ubiquitous structures in the solar wind and in planetary magnetosheaths. They consist of a strong depression of the magnetic field strength, most likely in pressure balance through increased plasma pressure, which is convected with the plasma flow. These structures are created through a plasma temperature anisotropy, where the perpendicular temperature (with respect to the magnetic field) is greater than the parallel temperature. The occurrence rate of these magnetic holes between Earth and Mercury can give us information about how the solar wind conditions develop on their way from the Sun to the outer Solar System. They also give information about basic plasma processes such as diffusion of magnetic structures. Aims. In this study we investigate the occurrence, size, and depth of magnetic holes during the cruise phase of BepiColombo and compare them with earlier studies. Methods. The BepiColombo magnetometer data were used to find the magnetic holes. We determined the size in seconds, the depth with respect to the background field, and the rotation angle of the background field across the structure. Minimum variance analysis delivers the polarization state of the magnetic holes. A direct comparison is made to the results obtained from the MESSENGER cruise phase. Results. We find an almost constant occurrence rate for magnetic holes between Mercury and Earth. The size of the holes is determined by the plasma conditions at the location where they are created and they grow in size, due to diffusion, as they move outwards in the Solar System. The greater the rotation of the background magnetic field across the structure, the larger the minimum size of the magnetic hole is.

Plasma and magnetic field observations by BepiColombo during its 2nd Venus flyby in August 10, 2021 have been examined and compared with the newly developed global hybrid simulation LatHyS for the Venusian environment. The LatHyS-Venus simulation was first validated by a comparison with Venus Express observations obtained during average solar wind conditions, before it was applied to the BepiColombo flyby using as inputs solar wind parameters measured upstream of Venus by Solar Orbiter. The simulation confirms that BepiColombo passed through the stagnation region of Venus, which supports the results obtained by data analysis. In addition, we have sampled the plasma parameters along the BepiColombo trajectory and constructed the energy spectrum for two species, i.e., protons of both solar wind and planetary origins, and planetary oxygen ions, and discussed the possible effects due to the limited field of views of the plasma instruments onboard BepiColombo. The most intense observational features are properly captured in the LatHyS-Venus simulation, which show that the model is a powerful tool for interpreting and understanding in-situ data obtained from the instruments with a limited field of views. The estimated ion escape for protons and oxygen ions at Venus during the BepiColombo flyby is of the order of ∼1024 ions/s, which is the same order of magnitude compared to the estimation from Venus Express observations at the solar minimum.