Search

Spacecraft charging is a well‐known effect that occurs when a spacecraft is located in a charged environment such as plasma. In this process, the surface of the spacecraft acquires an electrostatic potential through the accumulation and emission of positive and negative charges. In addition to causing severe electrostatic discharges, it also significantly affects low‐energy particle measurements performed by instruments onboard the spacecraft as it causes a change in energy and a distortion of the Field Of View (FOV) of the instrument by modifying the trajectory of measured particles. Spacecraft charging is therefore an important aspect to consider for Jovian plasma Dynamics and Composition analyzer (JDC), an instrument which aims to perform cold plasma measurements around the Galilean moons onboard JUpiter ICy moons Explorer (JUICE). In this study we use SPIS to perform simulations to study the FOV distortion of JDC for positive ions caused by spacecraft charging in two environments of the JUICE mission: the ionosphere of Ganymede and the Jovian magnetosphere. We show that the resulting distortion of the instrument FOV is highly space dependent and varies in shape and intensity from a pixel to another. However, we show that in both environments the complexity of the interactions between measured positive ions and the spacecraft can be decomposed and described as a superposition of a finite number of elementary interactions (i.e., modes). We show that each mode is caused by a specific element of the spacecraft and leads to a characteristic distortion of the instrument FOV. This study constitutes a first step toward necessary spacecraft potential corrections of the measurements performed by JDC. Key Points: The spacecraft potential affects charged particle measurements by distorting the instrument field of viewInteractions between JUpiter ICy moons Explorer spacecraft and Jovian plasma Dynamics and Composition analyzer positive ion measurements are simulatedThe spacecraft potential causes complex and highly geometry dependent distortions, especially for particles with low energy [ABSTRACT FROM AUTHOR]

Jovian magnetospheric plasma irradiates the surface of Ganymede and is postulated to be the primary agent that changes the surface brightness of Ganymede, leading to asymmetries between polar and equatorial regions as well as between the trailing and leading hemispheres. As impinging ions sputter surface constituents as neutrals, ion precipitation patterns can be remotely imaged using the Energetic Neutral Atoms (ENA) measurement technique. Here we calculate the expected sputtered ENA flux from the surface of Ganymede to help interpret future observations by ENA instruments, particularly the Jovian Neutrals Analyzer (JNA) onboard the JUpiter ICy moon Explorer (JUICE) spacecraft. We use sputtering models developed based on laboratory experiments to calculate sputtered fluxes of H2O, O2, and H2. The input ion population used in this study is the result of test particle simulations using electric and magnetic fields from a hybrid simulation of Ganymede's environment. This population includes a thermal component (H+ and O+ from 10 eV to 10 keV) and an energetic component (H+, O++, and S+++ from 10 keV to 10 MeV). We find a global ENA sputtering rate from Ganymede of 1.42 × 1027 s-1, with contributions from H2, O2, and H2O of 34%, 17%, and 49% respectively. We also calculate the energy distribution of sputtered Energetic Neutral Atoms (ENAs), give an estimate of a typical JNA count rate at Ganymede, and investigate latitudinal variations of sputtered fluxes along a simulated orbit track of the JUICE spacecraft. Our results demonstrate the capability of the JNA sensor to remotely map ion precipitation at Ganymede. Plain Language Summary Particles trapped by Jupiter's magnetic field interact with Jupiter's moons. Ganymede, the largest of those moons, lacks a dense atmosphere to protect its surface from these energetic Jovian particles, but Ganymede's magnetic field is strong enough to influence their trajectory: charged particles are deflected away from equatorial regions to polar regions, resulting in uneven particle precipitation patterns at the surface of Ganymede. When ions hit the surface of Ganymede, they eject particles from the surface, in a process referred to as sputtering. Those particles are mostly neutral and therefore unaffected by Ganymede's magnetic fields, so we can image where ions hit the surface of Ganymede by measuring ejected neutral particles. The Jovian Neutrals Analyzer (JNA) will fly onboard the JUpiter ICy moon Explorer (JUICE) spacecraft and will measure sputtered neutrals in the vicinity of Ganymede. To help interpret the data to be collected by JNA, we used models derived from laboratory experiments to simulate what JNA will observe at Ganymede. Our results show that JNA will be able to show us where ions hit the surface of Ganymede, which is important as uneven ion precipitation is thought to explain why Ganymede's poles are brighter than its equatorial regions. [ABSTRACT FROM AUTHOR]

The general-purpose PreAmplifier–DIscriminator application-specific integrated circuit (ASIC) chip, PADI, was originally designed to be used as front-end electronics (FEE) for reading out the timing resistive plate chambers in the time-of-flight (TOF) wall of the compressed baryonic matter (CBM) experiment of the future Facility for Antiproton and Ion Research (FAIR) facility in Darmstadt, Germany. Here, we present the last models of this 0.18-μm CMOS technology—PADI-X, PADI-XI, and PADI-XII—as well as their key features and test results. While the PADI series was originally developed for high-energy physics experiments carried out at ground facilities, it turned out that PADI is also suitable for space experiments and PADI-X was selected for one sensor of the European Space Agency, JUpiter ICy moons Explore (JUICE) mission. Currently, the most recent model of the series, PADI-XII, has been tuned for space applications and the prototype batch is currently under production. [ABSTRACT FROM AUTHOR]

The ESA-JAXA BepiColombo mission to Mercury will provide simultaneous measurements from two spacecraft, offering an unprecedented opportunity to investigate magnetospheric and exospheric particle dynamics at Mercury as well as their interactions with solar wind, solar radiation, and interplanetary dust. The particle instrument suite SERENA (Search for Exospheric Refilling and Emitted Natural Abundances) is flying in space on-board the BepiColombo Mercury Planetary Orbiter (MPO) and is the only instrument for ion and neutral particle detection aboard the MPO. It comprises four independent sensors: ELENA for neutral particle flow detection, Strofio for neutral gas detection, PICAM for planetary ions observations, and MIPA, mostly for solar wind ion measurements. SERENA is managed by a System Control Unit located inside the ELENA box. In the present paper the scientific goals of this suite are described, and then the four units are detailed, as well as their major features and calibration results. Finally, the SERENA operational activities are shown during the orbital path around Mercury, with also some reference to the activities planned during the long cruise phase. [ABSTRACT FROM AUTHOR]

The Advanced Small Analyzer for Neutrals (ASAN) is a compact mass resolving energetic neutral atom analyzer flown on the Yutu-2 rover of the Chinese Chang’E-4 mission to the Moon. ASAN measures energetic neutral atoms in the energy range from 10 eV to 10 keV with typically 30% energy resolution. The field-of-view is a single angular pixel of 37° × 30° pointing at lunar surface. Energetic neutral atoms enter the instrument through a charge particle deflection system and are then ionized on a diamond-like carbon conversion surface. Positive ions from the conversion surface are energy analyzed using an electrostatic analyzer and their velocity is subsequently determined in a time-of-flight section using ceramic channel electron multipliers as detectors. The obtained mass resolution m/ Δ m is about 2, comfortably separating neutral hydrogen, helium, and the oxygen-group (≥16 amu). A full energy spectrum for energetic neutral atoms is obtained in 3 seconds. Switching the charged particle deflection system off, ASAN also directly measures positive ions with similar performance as for energetic neutral atoms. Including electronics the instrument weighs 970 g and consumes 3.4 W. [ABSTRACT FROM AUTHOR]

Recapturing the recoiling daughters from radioactive decay can be a simple way to diversify beam availability at rare isotope beam facilities. In the decay and recapture ion trapping (DRIT) technique, a parent species is stored in an ion trap and left to decay, and the daughter ions are recaptured by the trap and become available for use. We successfully demonstrated the technique using the electron beam ion trap (EBIT) at the TITAN facility. A pure cloud of 30Mg ions was stored in the EBIT for about one half-life and sent to a Penning trap mass spectrometer, which confirmed the production of 30Al daughter ions. Systematic measurements and simulations suggest high recapture efficiencies of the recoil ion and little influence of the recoiling energy in the observed losses. With the secondary beam, we also performed precision mass measurements of the parent 30Mg8+ and the daughter 30Al11+ ions. Our results agree with the literature and improve its precision. The success of this experiment shows that EBITs can produce high-quality beams through the DRIT technique. [ABSTRACT FROM AUTHOR]

We report on the measurements of the secondary electron yield of chemical-vapor-deposited diamond upon the reflection of primary H+, D+, H2+, C+, O+, and O2+ ions in an energy range of 50–1000 eV per atom at a 60° angle of incidence to the surface normal. Depending on the species and energy, a secondary electron yield between 0.1 and 2 was observed and remained unchanged over weeks without further periodic reconditioning of the surface and in spite of the moderate vacuum environment of 10-7 mbar. Semiempirical fit functions were found with a dependence on the inverse velocity and the square root of the atomic number of the projectiles. [ABSTRACT FROM AUTHOR]

Velocity distribution functions (VDFs) are a key to understanding the interplay between particles and waves in a plasma. Any deviation from an isotropic Maxwellian distribution may be unstable and result in wave generation. Using data from the ion mass spectrometer IMA (Ion Mass Analyzer) and the magnetometer (MAG) onboard Venus Express, we study proton distributions in the plasma environment of Venus. We focus on the temperature anisotropy, that is, the ratio between the proton temperature perpendicular (T⊥) and parallel (T‖) to the background magnetic field. We calculate average values of T⊥ and T‖ for different spatial areas around Venus. In addition we present spatial maps of the average of the two temperatures and of their average ratio. Our results show that the proton distributions in the solar wind are quite isotropic, while at the bow shock stronger perpendicular than parallel heating makes the downstream VDFs slightly anisotropic (T⊥/T‖ > 1) and possibly unstable to generation of proton cyclotron waves or mirror mode waves. Both wave modes have previously been observed in Venus's magnetosheath. The perpendicular heating is strongest in the near‐subsolar magnetosheath (T⊥/T‖≈3/2), which is also where mirror mode waves are most frequently observed. We believe that the mirror mode waves observed here are indeed generated by the anisotropy. In the magnetotail we observe planetary protons with largely isotropic VDFs, originating from Venus's ionosphere. Key Points: We present maps of the perpendicular and parallel proton temperatures and their ratio in the plasma environment around VenusThe largest perpendicular temperature anisotropy with a median temperature ratio of about 3/2 is found in the near‐subsolar magnetosheathThe region with the largest observed temperature anisotropy coincides with observations of proton cyclotron and mirror mode waves [ABSTRACT FROM AUTHOR]

Aims. Cometary ions are constantly produced in the coma, and once produced they are accelerated and eventually escape the coma. We describe and interpret the dynamics of the cometary ion flow, of an intermediate active comet, very close to the nucleus and in the terminator plane. Methods. We analysed in situ ion and magnetic field measurements, and characterise the velocity distribution functions (mostly using plasma moments). We propose a statistical approach over a period of one month. Results. On average, two populations were observed, separated in phase space. The motion of the first is governed by its interaction with the solar wind farther upstream, while the second one is accelerated in the inner coma and displays characteristics compatible with an ambipolar electric field. Both populations display a consistent anti-sunward velocity component. Conclusions. Cometary ions born in different regions of the coma are seen close to the nucleus of comet 67P/Churyumov- Gerasimenko with distinct motions governed in one case by the solar wind electric field and in the other case by the position relative to the nucleus. A consistent anti-sunward component is observed for all cometary ions. An asymmetry is found in the average cometary ion density in a solar wind electric field reference frame, with higher density in the negative (south) electric field hemisphere. There is no corresponding signature in the average magnetic field strength. [ABSTRACT FROM AUTHOR]