Spacecraft Charging Effects Research Articles

Charging effects on Rosetta dust measurements

ABSTRACT Dust particles released from comet 67P/Churyumov-Gerasimenko collect electrostatic charges. Their motion is influenced by the electric fields induced by the flow of the solar wind and by the charging of the Rosetta spacecraft itself. Dust grains with sufficiently low tensile strength might even be destroyed en route from the nucleus to Rosetta. A simple model of the plasma environment is discussed here to enable simultaneously following the charging and the dynamics of dust particles as a function of the heliocentric distance of the comet, the distance between Rosetta and the nucleus, the asymmetry in gas production between the northern and southern hemispheres of the nucleus, the amplitude and timing of ultraviolet flares, and the possible outbursts intermittently increasing the production rate of the comet. The electrostatic disruption, and the combination of attractive and repulsive forces between the dust grains and Rosetta might significantly alter the conclusions about the size and spatial distributions of dust grains released from 67P/Churyumov-Gerasimenko. These calculations are presented to help assess the effects of dust and spacecraft charging in the analysis and interpretation of dust measurements by Rosetta.

Precision electron measurements in the solar wind at 1 au from NASA’s Wind spacecraft

Context. The non-equilibrium characteristics of electron velocity distribution functions (eVDFs) in the solar wind are key to understanding the overall plasma thermodynamics as well as the origin of the solar wind. More generally, they are important in understanding heat conduction and energy transport in all weakly collisional plasmas. Solar wind electrons are not in local thermodynamic equilibrium, and their multicomponent eVDFs develop various non-thermal characteristics, such as velocity drifts in the proton frame and temperature anisotropies as well as suprathermal tails and heat fluxes along the local magnetic field direction. Aims. This work aims to characterize precisely and systematically the nonthermal characteristics of the eVDF in the solar wind at 1 au using data from the Wind spacecraft. Methods. We present a comprehensive statistical analysis of solar wind electrons at 1 au using the electron analyzers of the 3D-Plasma instrument on board Wind. This work uses a sophisticated algorithm developed to analyze and characterize separately the three populations – core, halo and strahl – of the eVDF up to super-halo energies (2 keV). This algorithm calibrates these electron measurements with independent electron parameters obtained from the quasi-thermal noise around the electron plasma frequency measured by Wind’s Thermal Noise Receiver (TNR). The code determines the respective set of total electron, core, halo, and strahl parameters through non-linear least-square fits to the measured eVDF, properly taking into account spacecraft charging and other instrumental effects, such as the incomplete sampling of the eVDF by particle detectors. Results. We use four years, approximately 280 000 independent measurements, of core, halo, and strahl electron parameters to investigate the statistical properties of these different populations in the slow and fast solar wind. We discuss the distributions of their respective densities, drift velocities, temperature, and temperature anisotropies as functions of solar wind speed. We also show distributions with solar wind speed of the total density, temperature, temperature anisotropy, and heat flux of the total eVDF, as well as those of the proton temperature, proton-to-electron temperature ratio, proton-β and electron-β. Intercorrelations between some of these parameters are also discussed. Conclusions. The present data set represents the largest, high-precision collection of electron measurements in the pristine solar wind at 1 au. It provides a new wealth of information on electron microphysics. Its large volume will enable future statistical studies of parameter combinations and their dependences under different plasma conditions.

CubeSat measurements of thermospheric plasma: spacecraft charging effects on a plasma analyzer

Spacecraft charging affects the accuracy of in-situ plasma measurements in space. We investigate the impact of spacecraft charging on upper thermospheric plasma measurements captured by a 2U CubeSat called Phoenix. Using the Spacecraft Plasma Interactions Software (SPIS), we simulate dayside surface potentials of − 0.6 V, and nightside potentials of − 0.2 V. We also observe this charging mechanism in the distribution function captured by the Ion and Neutral Mass Spectrometer (INMS) on-board Phoenix. Whilst negative charging in the dense ionosphere is known, the diurnal variation in density and temperature has resulted in dayside potentials that are smaller than at night. We apply charging corrections in accordance with Liouville’s theorem and employ a least-squares fitting routine to extract the plasma density, bulk speed, and temperature. Our routine returns densities that are within an order of magnitude of the benchmarks above, but they carry errors of at least 20%. All bulk speeds are greater than the expected range of 60–120 m/s and this could be due to insufficient charging corrections. Our parameterised ion temperatures are lower than our empirical benchmark but are in-line with other in-situ measurements. Temperatures are always improved when spacecraft charging corrections are applied. We mostly attribute the shortcomings of the findings to the ram-only capture mode of the INMS. Future work will improve the fitting routine and continue to cross-check with other in-flight data.

The Twin-Probe Method: Improving Langmuir Probe Measurements on Small Spacecraft

The Langmuir probe (LP) is generally accepted as an effective and relatively simple <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ</i> space plasma instrument (plasma density, electron temperature, and spacecraft potential). As LPs transition to small spacecraft, their implementation encounters new technical challenges. For example, a negative charge is induced on the spacecraft while positively biasing an LP due to the small surface area ratios (spacecraft surface area to probe surface area ≪ 1000). This results in a varying spacecraft potential that degrades the accuracy of electron temperature and electron density measurements, reducing the LP’s effectiveness as a diagnostic tool. To mitigate the effects of this spacecraft charging, the twin-probe method (TPM) was developed. The TPM corrects LP measurements with tracked spacecraft potentials, measured by a separate high-impedance probe. By accounting for the changes in the spacecraft potential, the LP sweeps can be reconstructed to provide more accurate measurements of the ambient plasma’s properties. Here, we detail the TPM and present laboratory experiments that study its effectiveness and summarize constraints. Through these experiments, we found that it is possible to correct for spacecraft charging effects that can cause deviations in temperature and density as large as 20% and 136%, respectively. Furthermore, we will demonstrate a clear correlation between area ratio, spacecraft charging, and the negative impact on temperature and density measurement accuracy.

The Multi-needle Langmuir Probe Instrument for QB50 Mission: Case Studies of Ex-Alta 1 and Hoopoe Satellites

The QB50 mission is a satellite constellation designed to carry out measurements at between 200–380 km altitude in the ionosphere. The multi-needle Langmuir probe (m-NLP) instrument has been mounted on board eleven QB50 satellites in order to characterize ambient plasma. The distinct feature of this instrument is its capability of measuring the plasma density at high spatial resolution without the need to know the electron temperature or the spacecraft potential. While the instrument has been deployed on many sounding rockets, the QB50 satellites offer the opportunity to demonstrate the operation of the instrument in low-earth orbit (LEO). This paper provides a brief review of the m-NLP instrument specifically designed for the QB50 mission and the case studies of the instrument’s performance on board the Ex-Alta 1 and Hoopoe satellites. The system has also been functionally verified in a plasma chamber at the European Space Research and Technology Center (ESTEC). Although the QB50 mission’s scientific goals have not been reached yet and some uncertainties still remain, there are some optimistic in-orbit preliminary results which could be helpful for the system improvement in future campaigns. Particularly, the electron emitter as part of the m-NLP science unit has demonstrated its capability in the plasma chamber and in orbit to mitigate spacecraft charging effects.

Simulations of the Spacecraft Charging and Wake Effects in the Solar Wind

航天器充电和尾迹效应会对周围等离子体造成扰动，影响测量装置结果的准确性.利用SPIS （Spacecraft Plasma Interaction Software）分别模拟了航天器与太阳风的相互作用，考察了光电效应以及航天器尺度对表面充电情况和尾迹效应的影响.结果表明：太阳风环境下，等离子体密度稀薄，电子电流比光电子电流小得多，航天器表面为正电势，航天器后部有清晰的尾迹结构，尾迹带负电；光电效应可改变尾迹结构，与无光电效应相比，光电效应使得航天器尾迹尺度变大；由于太阳风定向运动动能大于航天器表面势能，航天器的尾迹结构与其几何尺寸有关，航天器尺寸越大，尾迹尺度越大.

Internal Charge Estimates for Satellites in Low Earth Orbit and Space Environment Attribution

Space assets are continuously bathed by charged particles making their components susceptible to the effects of spacecraft charging. While their orbits are not embedded within the radiation belts, low earth orbiting assets with high inclinations do pass through the horns of these belts during each polar crossing, transiting through potentially dangerous charged particle populations many times per day. Occasionally, these low altitude horns include significant populations of energetic ~1 MeV electrons, which can penetrate typical spacecraft shielding and accumulate within dielectric materials and on ungrounded conductors, a process known as internal charging. The National Oceanic and Atmospheric Administration Polar Operational Environmental Satellites (POES) have experienced on-orbit anomalies in the boost voltage regulator (BVR) that is suspected to be associated with the accumulation and discharge of ~800 keV electrons. We have used observations from the Medium Energy Proton and Electron Detector (MEPED) instrument and a first principles model of charge accumulation [11] to develop estimates of electron internal charge (IC) accumulation over the lifetime of each POES and Metop spacecraft for a range of typical discharge time constants. With the advantage afforded by a larger database of anomalies, we are able to show that these BVR anomalies are generally not attributable in a simple way to the accumulation and subsequent discharge from >800 keV nor a higher fluence of lower energy >300 keV electrons. To the best of our knowledge, this paper presents the first long-term estimates of IC for spacecraft in highly inclined low earth orbits.

The effects of spacecraft charging and outgassing on the LADEE ion measurements

AbstractAbnormal ion signals can be usually seen in the Lunar Atmosphere and Dust Environment Explorer (LADEE) mission, including a suddenly enhanced current observed by the Lunar Dust Experiment (LDEX) near the sunlight‐shadow boundary and an unexpected water ion measured by the neutral mass spectrometer (NMS), with their magnitudes insensitive to the convection electric field of solar wind but dependent on the SW density and the elapsed time of LADEE mission. By analyzing both the LDEX measurements and the NMS measurements, we find that the current enhancement can be caused by a negatively charged spacecraft in the shadow region while the significant water ions should be some artificial ions from spacecraft outgassing. The artificial water ions show a peak near 8:00 LT that may be related to a sunlight‐controlled surface outgassing. In addition, the H2O flux can be enhanced near the end of the mission when the spacecraft has a lower altitude. It is found that the H2O enhancement is actually caused by an exosphere‐contributed return flux, rather than a real water exosphere.

Study of the spacecraft potential under active control and plasma density estimates during the MMS commissioning phase

AbstractEach spacecraft of the recently launched magnetospheric multiscale MMS mission is equipped with Active Spacecraft Potential Control (ASPOC) instruments, which control the spacecraft potential in order to reduce spacecraft charging effects. ASPOC typically reduces the spacecraft potential to a few volts. On several occasions during the commissioning phase of the mission, the ASPOC instruments were operating only on one spacecraft at a time. Taking advantage of such intervals, we derive photoelectron curves and also perform reconstructions of the uncontrolled spacecraft potential for the spacecraft with active control and estimate the electron plasma density during those periods. We also establish the criteria under which our methods can be applied.

The Space Weather Threat to Situational Awareness, Communications, and Positioning Systems

A recent space weather headline has cast doubt in the minds of some as to whether space weather is the source of spacecraft anomalies, and thus, whether it is important in the design and operation of critical situational awareness, communications, and positioning systems. In this paper, we reiterate the evidence for the importance of space weather, its role in producing spacecraft and ground anomalies, and the threat it poses to critical systems. In addition, we report new studies broken down by anomaly types and suggest the sources of the anomalies (surface charging or interior charging). Finally, we suggest spacecraft charging and ground effects mitigation strategies for design and operations of systems critical to our modern civilization.

Ionosphere plasma electron parameters from radio frequency sweeping impedance probe measurements

AbstractIn this work we will describe the technique of using an RF sweeping impedance probe (SIP) to measure the AC impedance of an electrically short monopole immersed in a plasma. We analyze the SIP measurements which are taken from the payload of the Storms sounding rocket, launched from Wallops Island, Virginia, in 2007. The scientific objective of the Storms mission was to concentrate on whether density irregularities observed in midlatitude spread F could arise from ionospheric coupling to terrestrial weather. As such, independent measurements of the electron density profile are crucial. Since the inherent nature of the SIP technique makes it relatively insensitive to errors introduced through spacecraft charging, probe contamination, and other DC effects, it is an ideal instrument to employ under disturbed plasma conditions. The instrument measures both the magnitude and phase of the AC impedance from 100 kHz to 20 MHz in 128 frequency steps, performing 45,776 sweeps over the entire flight. From these measurements we infer both the absolute electron density ne and the electron neutral collision frequencies νen throughout the flight trajectory. The SIP data can be approximately analyzed using a fluid formulation and thin sheath approximation particularly at altitudes below 200 km, which allows us to match the measurements to quasi‐static analytical formulas. At about 265 km on the upleg, the magnitude data transitioned to a highly damped response with increasing altitude. The phase data, on the other hand, continued to indicate increased plasma density and reduced collisionality as expected. For a large portion of the flight, the payload of the Storms mission exhibited an uncontrolled coning motion, making the local magnetic field orientation with respect to the dipole difficult to decipher. Despite these difficulties, we were able to obtain robust estimates of the electron density profile, using the phase information from each sweep. In addition, the electron neutral collision frequency obtained from matching to phase data alone was on the correct order of magnitude with respect to Naval Research Laboratory Mass Spectrometer Incoherent Scatter‐Extended model values in the ionosphere between 100 km and 150 km.

Electron Energy-Dependent Charging Effects of Multilayered Dielectric Materials

Measurements of the charge distribution in electron-bombarded, thin-film, and multilayer dielectric samples showed that charging of multilayered materials evolves with time and is highly dependent on incident energy; this is driven by electron penetration depth, electron emission, and material conductivity. Based on the net surface potential's dependence on beam current, electron range, electron emission, and conductivity, measurements of the surface potential, displacement current, and beam energy allow the charge distribution to be inferred. To take these measurements, a thin-film disordered SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> structure with a conductive middle layer was charged using 200-eV and 5-keV electron beams with regular 15-s pulses at 1-500 nA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Results show that there are two basic charging scenarios, which are consistent with simple charging models; these are analyzed using independent determinations of the material's electron range, yields, and conductivity. Large negative net surface potentials led to electrostatic breakdown and large visible arcs, which have been observed to lead to detrimental spacecraft charging effects.

How to Really Measure Low Energy Electrons in Space

There is little argument in the space plasma physics community that in-situ, low energy electron measurements are technically challenging. The primary obstacle has been the effects of spacecraft charging on the measured three-dimensional electron velocity space distribution. A successful spacecraft charging correction algorithm used with the three-dimensional electron instrument aboard the Ulysses spacecraft has clarified the role of spacecraft and instrument parameters in the eventual reconstruction of low energy electron distributions. Suggestions for instrument and spacecraft modifications that can minimize spacecraft charging effects are presented in this paper. The emphasis is on designs that lend themselves to robust correction algorithms.

Book review [review of "Guide to Mitigating Spacecraft Charging Effects" (Garrett, H.B. and Whittlesey, A.C.; 2012)

This is the first time that I have faced the topic described by the title of this book. As a consequence, my reading of this well written text has been guided more by my own curiosity on a new field related to EMC than by the wish to deepen my knowledge of the subject.

Commercial Space Tourism and Space Weather: An Update

Commercial Space Tourism and Space Weather: An Update

Deep Dielectric Charging of Spacecraft Polymers by Energetic Protons

The majority of research in the field of spacecraft charging concentrates on electron charging effects with little discussion of charging by protons. For spacecraft orbiting in the traditional LEO and GEO environments, this emphasis on electrons is appropriate since energetic electrons are the dominant species. However, for spacecraft in orbits within the inner radiation belts, or for interplanetary and lunar space probes, proton charging effects may also be of concern. To examine bulk spacecraft charging effects in these environments, several typical highly insulating spacecraft polymers were exposed to energetic protons with energies from 1 to 10 MeV to simulate protons from the solar wind and from solar energetic proton events. Results indicate that effects in proton-charged dielectrics are distinctly different than those observed due to electron charging. In most cases, the positive surface potential continued to increase for periods on the order of minutes to a day, followed by long-time-scale decay at rates similar to those observed for electron charging. All samples charged to positive potentials, with substantially lower magnitudes than for equivalent electron fluence. Possible explanations for the different behavior of the measured surface potentials from proton irradiation are discussed; these are related to the evolving internal charge distribution from energy-dependent electron and proton transport, electron emission, charge migration due to dark current and radiation-induced conductivity, and electron capture by embedded protons.

Plasma ESD Qualification Test Procedure of Alcatel Alenia Space Solar Array

The detrimental effects of spacecraft charging are well known, particularly when the charging leads to arcing on solar array and, consequently, to permanent power loss. Motivated by these concerns, Alcatel Alenia Space has undertaken several test campaigns to qualify solar array design and to investigate margins. This paper describes the state-of-the-art Alcatel Alenia Space solar array electrostatic discharge laboratory test setup and procedure. The primary discharges are created using a plasma source and negative polarization of the sample rear side. The required power to feed the arc can be delivered by a solar array simulator with low-capacitance power sources. The test sample is fully representative of a flight model

Solar wind electron temperature and density measurements on the Solar Orbiter with thermal noise spectroscopy

The measurement of the solar wind electron temperature in the unexplored region between 1 and 45 R s is of prime importance for understanding the solar wind acceleration. Solar Orbiter’s location, combined with the fact that the spacecraft will nearly co-rotate with the sun on some portions of its orbit, will furnish observations placing constraints on solar wind models. We discuss the implementation of the plasma thermal noise analysis for the Solar Orbiter, in order to get accurate measurements of the total electron density and electron temperature and to correct the spacecraft charging effects which affect the electron analyzers.

Study of Interspacecraft Coulomb Forces and Implications for Formation Flying

In the course of exploiting spacecraft formations for use in separated interferometry (or other missions), it is possible that the separation distance between vehicles will be on the order of 10 m. The effects of spacecraft charging on the dynamics of very closely spaced formations are investigated. For certain high-Earth orbits, the ambient plasma conditions will conspire to produce significant spacecraft charging in an environment with a plasma Debye length of more than 100 m. For such conditions, it is shown that the potential exists to develop disruptive interspacecraft Coulomb forces and torques, with magnitude comparable to candidate formation-keeping thrusters over distances of tens of meters. Because of the unexpectedly large interaction forces, the concept of purposely charging spacecraft to affect formation-keeping Coulomb forces is also explored. Analytic methods are developed that show the existence of static equilibrium formations in Earth orbit using only inter-vehicle coulomb forces for one-, two-, and three-dimensional formations. Such Coulomb formations would be free of the risk of plume contamination due to thrusters firing in close proximity. Figures of merit for the proposed Coulomb control system are calculated in a manner analogous to traditional propulsion systems, and it is shown that required forces can be created with milliwatts of power, can be controlled on a millisecond timescale, and imply specific impulses that can be as high as 1013 seconds.

Effects of spacecraft potential on three‐dimensional electron measurements in the solar wind

Using the three‐dimensional, low‐energy electron spectrometer aboard the Ulysses spacecraft, we have measured the gyrotropicity of electron distributions in the solar wind. In order to make these observations, we have developed a new technique for correcting spacecraft charging effects in three‐dimensional, low‐energy particle measurements. Comparisons of ion and electron number and current densities, and the alignment of electron temperature anisotropies with the local magnetic field, are presented as evidence of the improvement in the accuracy of the electron moments resulting from the spacecraft charging corrections. The implications of our charging correction technique go beyond simple scalar corrections to the Ulysses measurements. We discuss the effects of our charging correction upon the measurements of temporal and radial gradients in a plasma environment and for two‐dimensionally obtained low‐energy particle data.