We present an investigation of the dust distribution in the Saturn’s rings based on hypervelocity dust impacts observed by the Cosmic Dust Analyzer (CDA) and the Radio and Plasma Wave Science (RPWS) instrument on board the Cassini spacecraft. The dust impacts create spiky signals in the electric field waveforms that are used to determine profiles of impact count rate, dust mass, and evaluated wave power spectral density (PSD) during the ring crossings. Information about the dust composition and velocity is extracted from the available CDA data. The calculated profiles of the ring crossings are then employed to determine the width of the rings and their displacement from the equatorial plane as a function of radial distance from Saturn center in the range from 2.46 to 5.85 Rs. This dependence shows a significant enhancement of the dust density within the Janus/Epimetheus ring region at 2.46 — 2.56 Rs and at the Enceladus orbit at 3.95 Rs. The resolved dust impact rate and PSD profiles show a good agreement in the width and displacement of the investigated rings. Relations are found between the PSDs and the number of dust impact signals, and their amplitudes present in the waveform. Our results show that the calculated PSDs have strong dependence on the relative velocity between dust and spacecraft. The observed one order PSD variation at a fixed radial distance for a constant relative dust-spacecraft velocity is probably related to the variability of the dust population in the examined Janus/Epimetheus ring.

Dust grain impacting the spacecraft body can be either partly or totally evaporated and ionized as well as a small part of spacecraft material. A cloud of charged particles (impact cloud) generated by such impact can consequently influence the spacecraft potential and/or measurements of on-board scientific instruments. Electric field instruments are sensitive to these disturbances and typically register signals generated by dust impacts as short transient pulses. This method is commonly used for the detection of dust grains even without dedicated dust detectors. The presented study is focused on the influence of the ambient environment on dust detection for various designs of electric field instruments (probes/antennas) operating in the monopole and dipole configurations. An ambient plasma influences the spacecraft potential, which is crucial for charge separation and consequent propagation of the impact cloud. The plasma and solitary waves also affect dust detection by the presence of other pulses in the measured data. It is important to understand these effects to compare results obtained by various spacecraft in different environments.

Solar activity significantly influences the Earth's magnetosphere and ionosphere, causing current systems and space weather effects. The interaction between rapidly changing magnetic field and the Earth’s conductivity induces an electric field at the surface producing Geomagnetically Induced Currents (GICs) within critical human infrastructure, posing a risk of damage to power lines.GICs strongly depend on the ground conductivity. Sweden has large spatial variations and complexity in the underlying ground conductivity structure across the country. In order to better understand GICs and for the identification of the worst-case scenarios for Swedish power transmission lines, 3D simulations are essential.We present results from our GIC simulations, computed using our own 3D FDTD framework employing a Swedish ground conductivity model in high resolution. Compared to previous simulations of the Swedish power grid, ours is High Performance (runs on parallel GPUs), more flexible, and we can simulate the GICs in the time domain, instead of only the frequency domain as has been done before in simplistic approaches. This enables us to study GICs caused by much more realistic ionospheric source currents.

This study investigates pulses detected by the electric field instrument, ICE (Instrument Champ Electrique) onboard the DEMETER spacecraft. Using an automated identification algorithm, we identified 1,000 short pulses recorded in 2005 and 2010. The spatial distribution of these signals, primarily localized over South America and near the South Atlantic Anomaly (SAA), contradicts the initial assumption that they are generated by dust impacts. The absence of temporal and seasonal variations eliminates other potential sources, such as earthquakes and lightning. Our analysis suggests that energetic electrons are the most plausible explanation for these pulses, supported by the strong spatial correlation between the detected electric field spikes and high‐energy electron fluxes observed by the IDP (Instrument for the Detection of Particle) instrument onboard DEMETER. The equal distribution of pulse polarities and the detection of similar pulses in magnetic field observations further support this conclusion. These findings highlight the importance of carefully evaluating and interpreting pulses attributed to dust impacts, contributing to more accurate interpretations and a better understanding of dust impact signals in various space environments.

Electric field instruments can detect dust impacts on a spacecraft body as transient pulses in the measured electric field. Our study investigates these transient (millisecond) pulses detected by the Langmuir Probe and Waves (LPW) instrument onboard the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft. We present a statistical analysis of 360,000 medium frequency burst electric field waveforms recorded in 2015; the study aims to identify and analyze the characteristics of these transient pulses. An automatic routine is used to detect waveforms with rapid fluctuations in the electric field data; this comprises over 12,000 events in the dipole and nearly 5,000 in the monopole configurations. Our findings reveal that most of the pulses in monopole configuration are likely the result of interference rather than dust impacts. Our analysis mainly focuses on dipole observations, which predominantly consist of bipolar events typically associated with dust impacts. These events are mainly detected in the Martian ionosphere, where the spacecraft is negatively charged. Fewer events are recorded when the spacecraft is positively charged, with a maximum at an altitude of 1200 km. The low detection rate of dust impact signals outside the ionosphere suggests that the planet is the most probable source of these dust particles. However, the physical processes by which dust grains are lifted from the surface of the planet to high altitudes are not clear, and thus a possibility that the signals observed might not be generated by dust impacts remains for further investigations.

Hypervelocity (>1 km/s) dust grains orbiting in the inner heliosphere can collide with a spacecraft and create a plasma cloud that changes electrical conditions in the surrounding plasma. These changes can be detected by the onboard radio and plasma wave receivers acting as efficient dust impact detectors. Estimated dust impact rates depend on the observation time window and they are commonly extrapolated. Our study presents the RPW/TDS Maximum Amplitudes (MAMP) data that continuously monitors signals from up to four RPW antenna configurations (monopole or dipole, and HF Search Coil) onboard the Solar Orbiter satellite. The signal is sampled in the high cadence (2.091 Msps) and stored in a buffer as the absolute maximum amplitude. MAMP values are then provided with a cadence between 32 and 128 sps, giving us a time resolution between 8 and 31 ms. Individual dust impacts detected by the onboard algorithm evaluating 62ms-long waveform snapshots every second are compared with the MAMP observations and show a very good match. After corrections for the high amplitude plasma waves or non-standard operational modes, and together with the TDS Statistics, the MAMP observations are used for the individual dust impact identification and corrected impact rates during the entire Solar Orbiter mission.

Solar Orbiter is equipped with electrical antennas performing fast measurements of the surrounding electric field. The antennas register high-velocity dust impacts through the electrical signatures of impact ionization. Although the basic principle of the detection has been known for decades, the understanding of the underlying process is not complete, due to the unique mechanical and electrical design of each spacecraft and the variability of the process. We present a study of electrical signatures of dust impacts on Solar Orbiter's body, as measured with the Radio and Plasma Waves electrical suite. A large proportion of the signatures present double-peak electrical waveforms in addition to the fast pre-spike due to electron motion, which are systematically observed for the first time. We believe this is due to Solar Orbiter's unique antenna design and a high temporal resolution of the measurements. The double peaks are explained as being due to two distinct processes. Qualitative and quantitative features of both peaks are described. The process for producing the primary peak has been studied extensively before, and the process for producing the secondary peak has been proposed before (Pantellini et al., 2012a) for Solar Terrestrial Relations Observatory (STEREO), although the corresponding delay of 100–300 µs between the primary and the secondary peak has not been observed until now. Based on this study, we conclude that the primary peak's amplitude is the better measure of the impact-produced charge, for which we find a typical value of around 8 pC. Therefore, the primary peak should be used to derive the impact-generated charge rather than the maximum. The observed asymmetry between the primary peaks measured with individual antennas is quantitatively explained as electrostatic induction. A relationship between the amplitude of the primary and the secondary peak is found to be non-linear, and the relation is partially explained with a model for electrical interaction through the antennas' photoelectron sheath.

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.

This study investigates short (millisecond) pulses detected by the Langmuir Probe and Waves instrument on board the Mars Atmosphere and Volatile Evolution spacecraft. We present a statistical analysis of 360,000 medium-frequency burst electric field waveforms recorded in 2015; the study aims to identify and analyze the characteristics of these transient pulses. An automatic routine is used to detect waveforms with rapid fluctuations in the electric field data; this comprises over 12,000 events in the dipole and nearly 5000 in the monopole configurations. Our findings reveal that most of the pulses in monopole configuration are likely the result of interference rather than dust impacts. Our analysis mainly focuses on dipole observations, which predominantly consist of bipolar events typically associated with dust impacts. These events are mainly detected in the Martian ionosphere, where the spacecraft is negatively charged. Fewer events are recorded when the spacecraft is positively charged, with a maximum at an altitude of 1200 km. The low detection rate of dust impact signals outside the ionosphere suggests that the planet is the most probable source of these dust particles. However, the physical processes by which dust grains are lifted from the surface of the planet to high altitudes are not clear, and thus a possibility that the signals observed might not be generated by dust impacts remains for further investigation.

Dust grain impacting the spacecraft body can be either partly or totally evaporated and ionized as well as a small part of spacecraft material. A cloud of charged particles (impact cloud) generated by such impact can consequently influence the spacecraft potential and/or measurements of on-board scientific instruments. Electric field antennas are sensitive to these disturbances and typically register signals generated by dust impacts as short transient pulses. This method is commonly used for the detection of dust grains even without dedicated dust detectors. Expanding impact clouds can also influence measurements of other scientific instruments such as magnetometers and particle detectors.The presented study is focused on the understanding of the generation and consequent expansion of impact cloud after dust impacts on Solar Orbiter. The Time Domain Sampler (TDS), a subsystem of the Radio and Plasma Wave (RPW) instrument, is used for the detection of individual dust impacts. Three channels of short electric field waveforms (typically 62.5 ms) provide us with information about the influence of expanding particles on three electric antennas. We have analyzed more than 2000 waveform snapshots with dust impacts in various operation modes (monopole and dipole antenna configurations) of RPW/TDS. Additional information about particles generated by dust impact is provided by the Electron Analyser System (EAS), one of the Solar Wind Analyser (SWA) suite instrument.

We discuss a suite of instruments cable of carrying out the next generation of in situ cosmic dust measurements from the heliosphere into interstellar space in support of the Interstellar Probe mission concept.A Dust Analyzer should be considered as the highest priority for its coverage of both compositional and dynamical information of the bulk of interstellar dust (ISD) and interplanetary dust particle (IDP) populations, essential to address the major science questions.A PVDF Dust Counter and Plasma Wave Antenna instrument could additionally provide critical improvement through the detection of larger, rarer dust populations, to constraining the mass density of ISD as well as providing additional directionality coverage.A Neutral Mass Spectrometer bridges the measurement gap between microscopic dust grains and gas species, potentially relevant for understanding the nature and interactions of the very local interstellar medium and our heliosphere.The Dust Analyzer, PVDF Dust Counter, and Plasma Wave Antenna instruments can be calibrated using dust accelerator facilities (University of Colorado, USA, see Shu et al., 2012; and Universität Stuttgart, Germany) with ISD-relevant materials at realistic mass and speed ranges.

Comet Interceptor is the ESA F1 space mission aiming to explore a comet very likely entering the inner Solar System for the first time, or to encounter an interstellar object originating at another star, scheduled for launch in 2029 together with the ESA L-class Ariel spacecraft. Following the mission adoption in June 2022, the spacecraft and scientific payload development have advanced to the Phase C. In our contribution we present the status of development of the Low-energy electron spectrometer (LEES) that is a part of the Dust-Fields-Plasma multi-instrument suite deployed at the main spacecraft A (DFP-A).The DFP-A/LEES sensor will determine the thermal and suprathermal electron densities, temperatures, and the velocity distribution functions of the local plasma environment of both the solar wind and coma. It will also measure the local properties of negatively charged ions and dust, and detect photoelectrons resulting from neutral-plasma interactions in order to infer the magnetic connectivity between the cometary environment and the spacecraft. The LEES measurements are needed to understand the ionization sources of the cometary neutral gas as well as to infer the plasma boundaries of the induced magnetosphere of the comet. The electron spectrometer is a further miniaturized version of the top-hat analyser inherited from the Stereo, Maven and BepiColombo missions. We present the overall design, simulation of the spacecraft electromagnetic and particle environment influence to the LEES measurements and the intermediate results of testing of the LEES components to survive a potential harsh dust environment during the comet flyby.

We report the first laboratory experiment dealing with the interaction of a cosmic dust simulant with positrons emitted from a 22 Na radioisotope. Measurements of a charge of micrometer SiO 2 dust grains with an accuracy of one elementary charge e revealed +1 e steps due to positron annihilation inside the grain. The observed average rate of these charging events agrees well with prediction of a model based on the continuous slowing down approximation of energetic of positrons inside the grain. Less frequent charge steps larger than +1 e were attributed to emission of secondary electrons during positron slowing down. The determined coefficient of secondary electron emission is approximately inversely proportional to the grain radius. The experimental results led us to the formulation of a possible scenario of interstellar dark clouds charging.

Dust impact on the spacecraft body can result in short pulses in the measured electric field. Our study is focused on these pulses detected by the Langmuir Probe and Waves (LPW) instrument onboard the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft. LPW detects electric field signals in dipole and monopole configurations using two long identical stacer booms. Out of all the modes, we use the medium frequency burst mode, the data covers 62.5 milliseconds using 4096 measured points which gives us a sampling frequency of 66.67 kHz. We present a preliminary statistical analysis over the year 2015 (360000 waveforms) and the analysis is focused on distinguishing dust impact signatures from solitary structures. To reliably distinguish solitary waves from dust impact signals by an automatic code is a challenging task as the solitary wave signatures in the electric field data can be similar to the transient pulses generated by dust impacts. Therefore, we choose two different parameters to classify two groups of events: the ratio of rising and decay times and the ratio of positive and negative peaks of the pulse. In total, we find approximately 10000 events which compose both solitary waves and the most probable dust impacts. We discuss signals generated by dust impacts and solitary waves for different operation modes of electric field probes, spacecraft potentials, and distance of probes to the spacecraft surface.

This article presents the results of automatic detection of dust impact signals observed by the Solar Orbiter – Radio and Plasma Waves instrument. A sharp and characteristic electric field signal is observed by the Radio and Plasma Waves instrument when a dust particle impacts the spacecraft at high velocity. In this way, ∼ 5–20 dust impacts are daily detected as the Solar Orbiter travels through the interplanetary medium. The dust distribution in the inner solar system is largely uncharted and statistical studies of the detected dust impacts will enhance our understanding of the role of dust in the solar system. It is however challenging to automatically detect and separate dust signals from the plural of other signal shapes for two main reasons. Firstly, since the spacecraft charging causes variable shapes of the impact signals, and secondly because electromagnetic waves (such as solitary waves) may induce resembling electric field signals. In this article, we propose a novel machine learning-based framework for detection of dust impacts. We consider two different supervised machine learning approaches: the support vector machine classifier and the convolutional neural network classifier. Furthermore, we compare the performance of the machine learning classifiers to the currently used on-board classification algorithm and analyze 2 years of Radio and Plasma Waves instrument data. Overall, we conclude that detection of dust impact signals is a suitable task for supervised machine learning techniques. The convolutional neural network achieves the highest performance with 96 % ± 1 % overall classification accuracy and 94 % ± 2 % dust detection precision, a significant improvement to the currently used on-board classifier with 85 % overall classification accuracy and 75 % dust detection precision. In addition, both the support vector machine and the convolutional neural network classifiers detect more dust particles (on average) than the on-board classification algorithm, with 16 % ± 1 % and 18 % ± 8 % detection enhancement, respectively. The proposed convolutional neural network classifier (or similar tools) should therefore be considered for post-processing of the electric field signals observed by the Solar Orbiter.

Enceladus, an icy moon of Saturn, possesses an internal water ocean and jets expelling ocean material into space. Cassini investigations indicated that the subsurface ocean could be a habitable environment having a complex interaction with the rocky core. Further investigation of the composition of the plume formed by the jets is necessary to fully understand the ocean, its potential habitability, and what it tells us about Enceladus’s origin. Moonraker has been proposed as an ESA M-class mission designed to orbit Saturn and perform multiple flybys of Enceladus, focusing on traversals of the plume. The proposed Moonraker mission consists of an ESA-provided platform with strong heritage from JUICE and Mars Sample Return and carrying a suite of instruments dedicated to plume and surface analysis. The nominal Moonraker mission has a duration of ∼13.5 yr. It includes a 23-flyby segment with 189 days allocated for the science phase and can be expanded with additional segments if resources allow. The mission concept consists of investigating (i) the habitability conditions of present-day Enceladus and its internal ocean, (ii) the mechanisms at play for the communication between the internal ocean and the surface of the South Polar Terrain, and (iii) the formation conditions of the moon. Moonraker, thanks to state-of-the-art instruments representing a significant improvement over Cassini's payload, would quantify the abundance of key species in the plume, isotopic ratios, and the physical parameters of the plume and the surface. Such a mission would pave the way for a possible future landed mission.

Hypervelocity dust impacting the spacecraft body can be either partly or totally destroyed and evaporated and then creates a cloud of charged particles. Electrons and ions generated by such impacts can consequently influence the spacecraft potential and/or measurements of on-board scientific instruments. Electric field instruments are sensitive to these disturbances and typically register signals generated by dust impacts as short pulses. Once they are distinguished from other signals, they can be used for the detection of dust grains by spacecraft (even without dedicated dust detectors). Solar Orbiter is equipped with the RPW (Radio and Plasma Wave) instrument including three electric field antennas allowing such detection. The time domain sampler (TDS) subsystem of RPW provides typically short electric field waveforms (62.5 ms) sampled at a rate of 262.1 kHz We have analyzed individual electric field waveforms of dust impacts detected by Solar Orbiter RPW/TDS and sorted into different categories (typical dust impact, impacts with the complex response, misinterpreted events, and suspicious events). Typical dust impacts are compared with an expected signal based on a model of dust impacts. The reliability of dust detection (fraction of misinterpreted and suspicious events) is evaluated with respect to the distance from the Sun.

Cassini spacecraft investigated the Saturn environment more than 13 years. In course of this long period, the RPWS (Radio Plasma Wave Science) experiment not only mapped electric fields in the Saturn’s magnetosphere but also registered a large number of sharp spiky signals caused by hypervelocity dust impacts within Saturn rings. We have identified more than 140 000 such waveforms recorded by electric antennas with 10 or 80 kHz cadence in a close proximity of the ring mid-plane (up to 0.2 Rs). Among them, shapes and amplitudes of more than 100 000 non-saturated impacts were corrected on the Cassini WBR (Wide Band Receiver) transfer function. Our laboratory experiment with the 1:20 reduced model of Cassini positioned in the test chamber of the dust accelerator allowed us to determine dependences of the signal shape and amplitude on the dust parameters (velocity and mass) and spacecraft potential. We apply these results on calculations of the mass and size distributions of dust particles detected by the electric field antennas within the Saturn ring system. The core of the paper is devoted to relation between dust characteristics (determined from impact signals and local plasma parameters) and ring mass profiles at distances ranging from 2 to 60 Rs from the surface.

Dust in the interstellar space is illuminated by cosmic radiation that consists of photons of different wavelengths and energetic charged particles. Whereas the photoemission is rather well understood, charging of dust grains due to interaction of with energetic charged particles was not experimentally studied in detail so far. We report the first laboratory experiment dealing with the interaction of a cosmic dust simulant with energetic charged particles emitted from a radioisotope. Measurements of the charge of micrometer silicate dust grains with an accuracy of one elementary charge revealed several processes leading to the dust charging. The observed average rate of charging events agrees well with prediction of a model based on the continuous slowing down approximation of energetic particles inside the grain. Charge steps larger than one elementary charge were attributed to emission of secondary electrons excited by the primary particle slowing down. The determined yield of secondary electron emission is approximately inversely proportional to the grain radius. The experimental results led us to the formulation of a possible scenario of interstellar dark clouds charging.