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We have characterized spacecraft charging events in low Earth orbit (LEO) polar regions with the Active Monitor Box of Electrostatic Risk (AMBER) instrument onboard the Joint Altimetry Satellite Oceanography Network—3 (Jason-3) ocean topography mission for the first time for this spacecraft. AMBER data, taken at an altitude of 1336 km, over the period January 2017–March 2020, with measurements recorded close to the current solar minimum have been analyzed, using systematic filtering of ions spectrograms with selected threshold energies and time windows to detect negative spacecraft charging events; 109 spacecraft charging events were found. The events are examined visually and characterized by their spatial and temporal location, duration, and intensity (e.g., spacecraft potential). At the Jason-3 altitude (1336 km), the ion signature predominately lasts under 30 s in conjunction with auroral inverted V crossings, while intense fluxes of electrons corresponding to the encounter of the discrete auroral region last between 30 s and 1 min. Most of the detected spacecraft charging events show charging levels between −30 and −1000 V. The spacecraft charging events are located in the magnetic local time (MLT) sector 17h–05h, predominately before midnight. The distribution is equal between the northern and southern hemispheres. We found a high correlation between the charging time profile and that of the auroral electron average energy and energy flux along the satellite path. Overall statistics over three years as well as different event morphologies, electron spectra, and comparisons to worst case electron flux spectral distributions are presented and discussed. [ABSTRACT FROM AUTHOR]

The objective of the European Space Agency validation of internal charging tools using the realistic electron environmental facility (REEF) project is to assess the performance of internal charging tools against experimental measurements made at the REEF facility at the University of Surrey. REEF uses an intense strontium-90 beta-emitting radioactive source to simulate the space environment. This project is complemented by parallel experiments to derive material parameters, conducted by ONERA. We report results from REEF with four different types of dielectric material and compare these results to predictions from the DICTAT, MCICT, and NUMIT internal charging simulation tools. The materials under investigation are Cirlex, PEEK, FR4, and Neoflon (FEP). We find that in many cases, the computer codes struggle to recreate REEF results, which raises significant questions over the validity of internal charging mitigation analyses. We show the advantages and disadvantages of each model and suggest what features could be added in order to improve the fidelity of their predictions. [ABSTRACT FROM AUTHOR]

Although spacecraft charging in low Earth orbit is generally regarded as insignificant because the cold dense ionospheric plasma prevents the development of strong potential differences, scientific satellites (e.g., Centre National d'Études Spatiales TARANIS satellite) carry very sensitive instruments, the measurements by which may be impacted by the charging of the spacecraft. In order to assess the effect of the spacecraft charging on the measurements, simulations will be performed using the Spacecraft Plasma Interaction System (SPIS) software. Different numerical schemes are implemented in the SPIS, but none is perfectly fit to perform very low-noise simulations for satellites in ionospheric plasma within an admissible computation time. In this paper, a coupling between the Poisson-Boltzmann approximation and the particle-in-cell schema is proposed. This results in having the advantages of the analytic methods in terms of statistical noise and computational resources without suffering from some of their limitations. [ABSTRACT FROM AUTHOR]

A new model of dielectric conductivities has been implemented in SPIS-IC. It allows modeling the time-dependent behavior of the charge transport and the electric potential inside payload components under realistic radiation environments in space. The simulation results have been compared to experiments on four validation cases going from simple 1-D geometry to more complex 3-D components such as a d-type connector. The comparison shows a good agreement in most of the cases, and the discrepancies are explained in certain cases. Finally, the results have been analyzed in term of discharge probability and severity. This study also shows the great importance of time-dependent modeling of the radiation-induced conductivity. [ABSTRACT FROM PUBLISHER]

The simulation of the impact of small-scale components on the electrostatic charging of a spacecraft requires the implementation of new multiscale numerical schemes. For instance, resolving the solar array interconnects is needed to accurately simulate the current collection by a satellite with electric propulsion. We here present an implementation of the nonlinear patch method in the Spacecraft Plasma Interaction Software (SPIS) simulation code. This method allows for local mesh refinements by embedding a local patch in a relatively coarse mesh and iteratively solving on the different meshes. The nonlinear patch method and its SPIS implementation are detailed, and numerical simulations are provided, showing the flexibility and the efficiency of the proposed method. A simulation of a complete geostationary telecom satellite with detailed solar array interconnect is proposed. [ABSTRACT FROM PUBLISHER]

High-velocity impacts of micrometeoroids and debris are proven causes of solar arrays power loss. Many studies have been carried out in this domain with relatively large size particles, in the range of 1 mm, causing obviously large damages, but with a small probability of occurrence. This paper deals with the occurrence of secondary arcing triggered on solar panel rear face cables with defects (lack of dielectric envelope) by smaller particles, in the range of 20– 80~\mu \textm (20 to 5 km/s), that is, with a probability of impact of several hundred of impacts by \textm^2 and by year both in low earth and geostationary orbits. Plasmas produced by high-velocity impacts on metallic (aluminum) and dielectric (Kapton) surfaces are characterized with a Langmuir triple probe (temperature, density, floating potential, and escape velocity). Secondary arcing tests on rear-side cables with cracks under high-velocity impacts are achieved using a solar array simulator with realistic in flight electrical conditions (120 \textV^-1 to 3 A). Secondary arcing tests and plasma characterization are also carried out with laser impacts (0.2 J YAG laser) and compared with high-velocity impacts. [ABSTRACT FROM PUBLISHER]

Space environment exposure may create cracks on solar panel backside wires. In terms of the wiring design of the solar array backside, environmental constraints applied on each wire are identical. Thus, the probability of two adjacent wires having cracks facing each other is very high. This configuration presents a risk of secondary arc occurrence, which can lead to a destructive process such as arc tracking. In order to determine in which conditions electrostatic discharges (ESDs) can lead to an arc, we have carried out an experimental study on solar panel backside-like samples. We have tested different types of wires presenting artificial mechanical cracks or space simulation aging cracks, set on a solar panel backside coupon. The wires are connected to a secondary arc test setup including a solar array simulator (SAS) set to different current values. As both direct and inverted potential gradient (IPG) charging are theoretically possible on geostationary orbit and low earth orbit, we have carried out, in the JONAS vacuum chamber (ONERA facility), both charging types. Direct charging was achieved with an electron gun and IPG with a plasma source. Results are presented for the two types of charging, different types of wires, and different SAS current values. They show that, in direct charging conditions, ESD propagates along the wires but the plasma density is too weak to provoke an arc. In IPG situation, ESDs are able to trigger different arc types, such as nonsustain arc, temporary sustain arc, and permanent sustain arc, depending on SAS current values. [ABSTRACT FROM PUBLISHER]

Polymers are widely used on spacecraft for different specific functions such as thermal and electrical insulation, mechanical support, and adhesion. These polymers are highly sensitive to radiation encountered in space. Their electric properties are especially significantly altered leading to a very specific behavior in terms of charge transport and discharge processes. Different dedicated facilities have been developed at ONERA, with Centre National d’Etudes Spatiales support, for the characterization of space used materials in representative conditions. Thanks to the use of these different facilities, it has indeed been demonstrated that radiation-induced conductivity of space polymers strongly affects the charging surface potential and depends on several parameters (radiation dose rate, total radiation dose, temperature, and on the induced electric field) through complex physical mechanisms that are described in this paper. The sensitivity of polymers on these different parameters strongly depends on the polymer trap distribution and molecular configuration. Experimental and numerical results are presented in this paper, coupled with the different experimental techniques developed and applied to this work. [ABSTRACT FROM PUBLISHER]

Electrostatic discharges (ESDs) on solar cells are a possible cause of dramatic consequences such as secondary arcs responsible for definitive power losses. To cope with these significant implications, different approaches are followed such as design rules reducing voltage between the adjacent cells, conductive layers, or grouting to try to reduce discharges triggering. However, ESDs on solar cells cannot be completely avoided and having a good knowledge of their characteristics is essential for prevention, prediction, and modeling. In this paper, we describe how the plasma emitted during an ESD on a solar cell can be analyzed with dynamic tools such as triple probes and time-resolved optical spectroscopy. These techniques are used to obtain the results on plasma density and electron temperature that can be compared with outputs from ESD and flashover propagation models. While time-resolved optical spectroscopy is used on a single point (the point where optical fiber is focused on), triple probe is also used for spatial measurements. With this technique, electron density is measured at several distances from the discharge point providing both temporal and spatial information. In a second time, the optical signature measured by optical spectroscopy is correlated with scanning electron microscope observations showing the existence of two kinds of triple points at cell’s edge. These two kinds of discharges have different optical signatures showing either elements from the active junction or from the substrate and rear electrode. These discharges are also distinguished by microscopic observations and images of cell’s edges confirm the previous results. These results show the importance of the silver back electrode and also of the eventual presence of covering glue on the position of the discharge. They provide information for models but let us also imagine the possible mitigation methods. [ABSTRACT FROM PUBLISHER]

Version 5.1 of Spacecraft Plasma Interaction Software (SPIS) has been recently released and is freely available for download to the whole community. It is the outcome of European Space Agency studies, SPIS-Geostationary Earth Orbit (GEO) and SPIS-SCI, and several contributions from the Spacecraft Plasma Interaction Network in Europe community members. It also relies on a Centre national d’études spatiales-sponsored activity to identify user needs of the industry for charging analysis. SPIS is now used in a much wider scope of applications than initially expected, from mission definition to in-flight scientific measurements analysis. The first version of a new modernized generation SPIS 5.1 aims to address these new issues and challenges in spacecraft surface interaction modeling, including spacecraft charging of commercial missions in Medium Earth Orbit/GEO. For this, SPIS 5.1 offers a simplified user interface and introduces new state-of-the-art software technologies. [ABSTRACT FROM PUBLISHER]

Since the last version, the numerical core and the user interface of Spacecraft Plasma Interaction Software (SPIS) have been significantly improved to achieve two objectives: 1) to make SPIS more user friendly and robust for industrial use and 2) to extend the multiscale capabilities and the precision of the solvers in order to model a large range of scientific missions. The new numerical algorithm and modeling capabilities are presented in detail. This new version permits modeling of time variations of the plasma environment, spinning spacecraft, semitransparent grids, secondary emission from 1-D thin elements (e.g., wires or booms), 2-D thin elements (for example, solar arrays), the effect of $v\times B$ electric field, particle detectors, and Langmuir probes onboard spacecraft. [ABSTRACT FROM PUBLISHER]

We have performed arcing tests on an aged grouted solar cell coupon provided by Kyutu Institute of technology (Japan) under New Energy and Industrial Development Organization (Japan) grant. Aging is simulated by electrons, protons, and UV irradiations combined with thermal cycling, corresponding to 10 years in the geostationary orbit. Arcing tests are performed with a European standard setup implemented with two different flashover simulators. Instead of using a large capacitance corresponding to the missing solar panel surface, we have implemented two more realistic devices: 1) a 2.4- \textm^2 Kapton surface charged in an inverted potential gradient mode, which releases an average flashover current of 6-A peak at 200 \mu \texts and 2) RLC circuit, deduced from the European Etude et Modelisation des Arcs sur Generateur Solaire study (large flashover on an 8- \textm^2 solar array panel). This circuit is connected between the solar array simulator (SAS) line and the surrounding environment with a ring-shape electrode, which releases an adaptable flashover current of 5-A peak during 600 \mu \texts (average values). The results present the occurrence of different arc types versus current/voltage SAS values. A comparison is made with other tests, on a similar coupon, performed by U.S. and Japanese laboratories and also with comparable coupons without grouting. [ABSTRACT FROM PUBLISHER]

When a primary discharge occurs on a solar array, it is important to understand what would be the maximum flashover expansion. This value would then be representative of in-flight scenarios on full panel size. This paper presents the results of the experimental campaign performed in the frame of the European Space Agency EMAGS3 project “Flash-over evaluation on large solar panels” and where we measure flashovers in different conditions on a real-solar panel. This experimental campaign is conducted in the large vacuum chamber of Industrieanlagen-Betriebsgesellschaft mbH (IABG) (Germany) on a solar panel of 4\,\times\,2 m provided by Astrium-Germany and organized in 52 linear strings of silicon cells covered by Cerium doped borosilicate glass (CMX) coverglasses (CG). During the test, several parameters are studied such as inverted potential gradient (IPG) obtained in plasma or in electrons and test of flashover expansion over a gap between panels by addition of a small panel. The main difficulty is in the evaluation of the value and homogeneity of the initial potential gradient to be able to determine the initial stored charge. The development of a model of flashover expansion has contributed significantly to the comprehension of the results and the assessment of the initial stored charge. During the first step (IPG by electrons at room temperature) \sim200 electrostatic discharges (ESDs) are recorded of which 12 discharge >75\% of the theoretical stored charge in the CG. In IPG by plasma at room temperature, \sim100 ESDs are recorded, 12 discharging >75\% of the theoretical stored charge including two that discharged the panel completely. With this test campaign we demonstrate that, even if the probability is not very high, an ESD on a solar panel could lead a flashover to expand and neutralize the complete surface of an 8-m^2 panel. In addition, we see that the flashover can continue across a gap of 10 cm. [ABSTRACT FROM PUBLISHER]

Dedicated experiments have been developed at ONERA to characterize the charging and relaxation behavior of irradiated space polymers. Postirradiation analyses have been performed through potential kelvin probe and leakage or displacement current measurements. We have been able to demonstrate that polymers are submitted, after irradiation, to electron emission from their surface during the relaxation phase. This electron emission presents very low kinetics and can be intense enough to contribute at significant level to the surface potential drop of these materials. A parametric study has been performed to confirm electron relaxation emission and get a better understanding of the underlying steering mechanisms. This emission process is strongly dependent on the energy of the incident electrons used during irradiation and nature of the irradiated material. We present here the experimental results on electron emission from Kapton and Teflon and discuss the different physical mechanisms that could account for this process. The influence of charge double layer and injected radiation dose could especially explain electron emission from the surface through bulk diffusion and energy release by electron–hole recombination process. [ABSTRACT FROM PUBLISHER]

Teflon Fluorinated Ethylene Propylene (FEP), used as thermal blankets on satellites, has a specific electrical behavior under space ionizing environment. Charging behaviors of this dielectric material, under electron beam irradiation, is of special interest for future spacecraft needs. Hence, ground experimental parameters have been adjusted in order to distinguish between the different physical mechanisms that steers FEP charging potential. The effect of incident electron spectrum, electric field, and dose rate has been investigated through surface potential measurements during and after the irradiation process. The experimental results especially reveal that charging potential evolution as a function of time is not strongly dependent upon the electron spectrum and the electric field but varies noticeably with dose rate. These results have been analyzed in the light of a physical model that takes into account ionization, trapping/detrapping, and recombination mechanisms for negative and positive charges. [ABSTRACT FROM PUBLISHER]

This paper describes the results analysis obtained during the experimental campaign conducted in the frame of the ESA EMAGS3 project “Flash-over (FO) evaluation on large solar panels.” A numerical model has been developed in order to better understand the characteristics of the so-called FO phenomenon. The experimental results, presented in detail in a companion paper, are analyzed in correlation with the present FO model. A basic model based on the assumption of a plasma bubble expansion in vacuum has been developed to model the FO propagation. The model holds on a two-dimensional Cartesian mesh representing the surface of the solar panel. On this mesh, the electrical potential evolution and the current collection are computed supposing that the bubble velocity is constant, the current extracted from the plasma bubble is space-charge limited, the secondary emission is the only source of electrons from the cover-glasses and its potential evolution is only due to the current collection. The inputs of the model are the potential topology before the ESD, the ESD triggering position, and the solar array characteristics (dimensions and cover-glasses capacitance). The outputs of the model are the time evolution of the total FO current, the potential map, and the current collection map on the solar array. The results comparison between the model and the experiments shows a very good agreement in the cases where the potential topology before the ESD is well known. It is especially true when using IPG by plasma because the potential profile is relatively uniform. In that case the comparison with numerical results is concluding. In the case of IPG by electron guns, the potential map before the ESD is relatively hard to obtain. In this case, the agreement between the model and the experimental result is obtained only for a limited number of cases. The detailed comparison between model results and experimental data is shown and analyzed in this paper. It appears clearly that the plasma bubble extends at the acoustic velocity of the ions generated at the cathode spot level. As a result, ESDs generated on solar cells junction or interconnects do not have the same dynamics. [ABSTRACT FROM PUBLISHER]

The high radiation dose received by space used polymers may greatly alter their electric properties. This effect could, for instance, reduce significantly radiation-induced conductivity (RIC) leading to high charging risks that were not predicted from pristine sample. For an optimized qualification and prediction, it is therefore highly important to characterize the charging properties of polymers and their evolution as a function of the received dose. This paper aimed at studying aging of electric properties of four different polymers (Teflon FEP, Kapton, polyepoxy DP 490 adhesive, and silicon QS1123 adhesive) at high dose level (10^5 and 10^6~Gy). We have been able to demonstrate that aging could lead to the reduction of RIC on some polymers (for polyepoxy and silicone adhesives, and FEP) or inversely to the increase of RIC on others (e.g., Kapton). Ionization effect must, however, be considered in the analysis of the results. Relaxation processes could drastically affect the charging profile and macroscopic electric properties. [ABSTRACT FROM PUBLISHER]

Flashover corresponds to the differential charging neutralization of dielectric parts on satellite surfaces when an electrostatic discharge (ESD) is triggered. In solar panels, it is supposed to have effects on solar cells aging and secondary arc occurrence. Laboratory experiments show that flashover propagation sometimes involves the whole charged surface, but is generally partial in terms of charge amount and covered surface. An assumption is made that these charged dielectric surfaces are never plain due to many discontinuities as for solar panels, intercell gaps, inserts, and so on. To establish which parameters monitor or stop flashover propagation, we study neutralization ratio of the flashover on 1-m^2 charged surfaces. We test and modified Kapton surfaces with different types of discontinuities added on the surface as dielectric sheathed and unsheathed wires. We also test a 1-m^2 solar panel coupon and compare results with Kapton surface. Based on this coupon, different electrical network architectures for solar cell strings are tested (parallel, series, and interlaced circuit) to verify if they have an effect on flashover characteristics and to determine the way the replacement current circulates in the solar cell strings. These tests are performed in the JONAS facility, which is a 9-m^3 vacuum chamber equipped with two electron guns and several measurement devices as surface potential probe and transient current probes. The sample under test is biased at a negative high voltage and charged with electrons to be in an inverted potential gradient situation to trigger ESDs. In Kapton film tests, ESDs are triggered on a six solar cells coupon set in the center of the Kapton surface. Results show 2-D surface voltage before and after flashover correlated to neutralized charges and solar cell strings replacement current. Effect or noneffect of surface topology on neutralization ratio and flashover propagation is shown for the Kapton film and the solar panel coupon. [ABSTRACT FROM PUBLISHER]

Surface and internal charging of dielectric materials is a potential cause of surface discharges and satellite anomalies, due to the fluctuating irradiation levels induced by space environment. Understanding conduction mechanisms and reducing charging levels are therefore important industrial issues for satellite designers and manufacturers. Surface potential measurements under irradiation and after charging (potential decay) are the most significant laboratory tests to qualify and understand the charging and discharging behavior of insulating materials. We present here experimental results obtained using the SIRENE facility at ONERA. Kapton and Teflon FEP films respond differently when subjected to a 20 keV charging electron beam combined with a 400keV ionizing electron beam. The physics underlying these experimental results is discussed. A simple numerical model has been developed. It is shown that different combinations of mobility, trapping and recombination may explain the results on both materials. The complex behavior observed on Teflon FEP may be attributed to the progressive deep trapping of the negative charge, enhancing holes recombination. [ABSTRACT FROM PUBLISHER]

While it demonstrated its capability to simulate many common situations, Spacecraft Plasma Interaction Software (SPIS) open source code lacked the possibility to model more challenging situations. The major cases of interest were identified as related to either multitimescale or multiphysical situations. Two major improvements were brought to SPIS code to answer these needs. The first one was an implicit circuit solver with an automatic determination of time steps. The implemented Newton-type algorithm makes use of a predictor for the plasma current variations when surface potentials change. The second major development was a multiphysical model for electrons. The approach consisted in using equilibrium or dynamical electron models in two different zones and connecting these zones at their boundary through a Child–Langmuir (CL)-type condition. Fulfilling this condition dynamically determines the location of the boundary and the electron current to be injected from the dense thermal zone to the space-charge zone. These new features were then used to simulate validation and application cases. The first one consisted in modeling a charging situation in GEO, which had been modeled with NASA charging analyzer (NASCAP) codes and published. Concerning the multiphysical model of electrons, the loop controlling the CL condition was first tested on elementary cases, exhibiting a good qualitative and quantitative behavior. It was then applied to the modeling of a ground experiment performed in JONAS plasma tank at the Office National d'Etudes et Recherches Aérospatiales, i.e., the expansion of the flashover generated by an electrostatic discharge over a precharged solar array coupon, leading to its neutralization. [ABSTRACT FROM PUBLISHER]

A physical flashover (FO) simulator has been developed by ONERA/DESP and CNES. The objective of this simulator is to represent the missing cells when testing small coupons in the laboratory. The aim of this paper is to present the results of a parametric study which has been performed on a sample constituted by a solar-array coupon made of six cells and a simulator constituted of a large surface of metallized polymeric film. Experiments were performed in the ONERA/DESP facility called JONAS which is a 9-\m^3 vacuum chamber equipped with a plasma source and a 10-keV electron gun. Electrostatic discharges (ESDs) occur in the inverted potential gradient (IPG) configuration obtained either by electrons or by plasma. The FO was characterized by measuring the neutralization current on the different surfaces with current probes. Therefore, we could get charge quantity, duration, and velocity. The surface potential of the coupon and the polymeric film were monitored before and after ESD by a potential probe, giving a good correlation with the amount of charges participating to the discharge. In order to determine what the limits of the FO are and what parameters can monitor it, we have studied different configurations: 1) electron or plasma IPG charging; 2) surfaces from 0.5 to 14 \m^2; 3) geometries—cylinder, ring, rectangular, and discontinuous surface; 4) primary arc locations—cell edge or interconnectors; and 5) absolute satellite capacitance values—between 300 pF and 300 nF. Analysis of the results is given for these configurations. [ABSTRACT FROM PUBLISHER]

Two spacecraft charging software tools, the Spacecraft Plasma Interaction Software and the Multi-Utility Spacecraft Charging Analysis Tool, have been compared in the situation of a wake generated by an object immersed in dense drifting plasma. Each model takes account of the particle dynamics, the space charge effect on the electric field, and the currents collected by the object. The cross-comparison resulted in a good agreement between the two codes and with previous experiments conducted on the same configuration. In particular, a highly negative voltage imposed to the object rear side allows the collection of drifting ions at this location. The nontrivial shape of the current density map was correctly simulated by the two codes. Future works may allow to reach a better quantitative agreement. [ABSTRACT FROM PUBLISHER]

Primary electrostatic discharges (ESD) and secondary arcs on spacecraft solar panels are simulated experimentally by introducing a needle trigger and investigated with a time-resolved emission spectroscopy method. The total spectral domain investigated ranges from 220 to 750 nm. An innovative active method has been developed in order to initiate ESD at a controllable time and location on triple-junction solar cells. It permits one to detect important steps of the discharge evolution, in particular the transition between primary ESDs and secondary arcs. In this experimental setup, the discharge begins on the triple-junction solar cell absorber, with gallium and germanium being detected from the very beginning. That indicates that the obtained ESDs are triggered on the solar cell edge close to the cover glass. The transition between primary ESDs and secondary arcs is accompanied by molecular material vaporization. It is thought that the glue or the underlying polyimide is evaporated mainly during secondary arcs, sometimes during primary ESDs. Once the secondary arcing is triggered, the complete edge of the solar cell assembly is impacted. That confirms that ESDs may significantly damage the solar cell assemblies. [ABSTRACT FROM PUBLISHER]

Cumulative electrostatic discharges (ESDs) on spacecraft solar cells result in the degradation of their performances. In this paper, silicon solar cells arc tested in inverted voltage gradient situation obtained in plasma. ENDs occurring on the cells are detected by both electrical and optical signatures. To be representative of flight ESDs. the test setup must avoid unwanted coupling with ground arcs. The degradation is then evaluated by measuring live current-voltage characteristic of the cell in darkness. The equivalent shunt resistance allows quantifying this degradation, which can he attributed to material deposition in the cell edge or to local cell carbonization due to arcing. Visual inspection of the cells allows us to correlate END location and local degradation of the cell. the important parameter for solar cell degradation is the amount of energy dissipated during the discharge. A model of the plasma expansion from the cathode spot is compared to measurement. This model explains the current rise during the first phase of the discharge, which is the value for normal ESDs and coupling with ground ESDs. [ABSTRACT FROM AUTHOR]

A good representativeness of the test setup used for the qualification of solar arrays is fundamental. We know now that the fiashover current involved in the electrostatic discharge is related with the total dielectric surface neutralized during the electrostatic discharge. This paper presents experiments on samples of different sizes, performed in a large vacuum chamber, JONAS, installed in ONERA/DESP, Toulouse, France. The samples are tested in the inverted voltage gradient configuration obtained with electrons. We observed that secondary arcs obtained on a large sample (i.e., with a long fiashover) had much longer durations than those on a small sample, i.e., the flashover is a critical parameter for secondary arc initiation and sustainment. [ABSTRACT FROM AUTHOR]

In this paper, recent improvements in the modeling capabilities of the Spacecraft Plasma Interaction Software (SPIS) code are presented. New developments still in progress are also reported. They should in particular allow modeling of fast dynamical phenomena, including processes as challenging as the second part of ESDs, i.e., the vacuum arc and its related flashover plasma expansion. The first, electronic, part of ESDs is already modeled. The range of SPIS application domains and studies is reviewed. An interesting study case, the assessment of charging at multiple-scale levels, is presented here in more detail. Charging in geostationary-Earth-orbit conditions is simulated from the spacecraft scale down to a solar-cell-gap (hence, decameters to millimeter) scale. This self-consistent computation shows that macroscopic inverted-voltage-gradient (IVG) cases may differ at microscopic scales close to a solar-cell gap, due to the local blocking of secondary emission by the small-scale electric-field configuration. We consider this effect as the likely origin of the different ESD triggering thresholds, depending whether IVG is obtained by electrons or plasma. [ABSTRACT FROM AUTHOR]

ONERA plasma tank JONAS is populated of drifting Ar+ argon ions representative of Low Earth Orbit environment, produced by a Kaufman source, and slow ions created by charge exchange with the background pressure of argon. When testing a mock-up or space equipment in this tank, it is often important to determine the drifting and slow ion densities in various locations. The orbital and radial motion models are compared to experimental current-voltage measurements and to numerical results. In the range of parameters used in this paper, the radial motion model is more adapted than the orbital-motion-limited model to determine slow ion density. Nevertheless, the number of measurements is necessarily limited and discriminating between fast and slow ions is not easy. A complementary approach consists in performing a numerical simulation of the plasma dynamics in the tank. Provided the modeled physics is validated, and the modeling is calibrated through measurements, this approach supplies fast and slow ion densities everywhere with an acceptable factor of uncertainty. This approach has been followed by characterizing in detail a given plasma configuration in JONAS and modeling it with Spacecraft Plasma Interaction Software open source code. The mock-up was a simple plate. We measured the plasma characteristics through numerous current-voltage sweeps and current space profiles at given probe potential. The modeling was based on fast ion beam measurements close to the source and the residual pressure. [ABSTRACT FROM AUTHOR]

Charges accumulate on the spacecraft surface through various processes such as conduction, irradiation, ionization, and polarization. These charges can affect the space system operations via an electric current flowing in the structure or a locally generated electric field. This paper is focused on the analysis of electron behavior in polymeric films such as polymethylmetaacrylate and Teflon subjected to an electron irradiation. The charge distribution is detected during and after the irradiation in situ by pulsed electroacoustic method. Surface-potential and surface-current measurements are also performed to get further information on the charge displacement with time. [ABSTRACT FROM AUTHOR]

The article provides information on the tenth Spacecraft Charging Technology Conference held in Biarritz.