The Decrease in Effective Photocurrents Due to Saddle Points in Electrostatic Potentials near Differentially Charged Spacecraft

Mandell, M. J.; Katz, Ira; Schnuelle, G. W.; Steen, Paul; Roche, J. C.

doi:10.1109/tns.1978.4329530

Cited by 41 publications

(21 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Here, J ph is an average photoemission rate for normally incident sunlight [17], and J e corresponds to a worst case plasma given in [43]. If α = 0, then the photoelectric current, including reflection, at the relevant frequency, is given by…”

Section: Competition With Ambient Electron Currentmentioning

confidence: 99%

See 1 more Smart Citation

Aspects of Spacecraft Charging in Sunlight

Lai

Tautz

2006

IEEE Trans. Plasma Sci.

View full text Add to dashboard Cite

Abstract-This paper is an overview of spacecraft charging in sunlight. The daylight photoelectron flux emitted from spacecraft surfaces normally exceeds the ambient electron flux. As a result, charging of spacecraft surfaces to positive voltage is expected to occur in sunlight. Indeed, spacecraft are often observed to charge to low positive voltages in sunlight. However, spacecraft can charge to high-level (kiloelectronvolts) negative voltages in sunlight. Why do spacecraft charge negatively in sunlight? One chief reason concerns differential charging between the sunlit and dark sides. For a satellite with dielectric surfaces, an electric field builds up on the shaded surfaces and then wraps around to the sunlit side to form a potential barrier that suppresses the photoemission. A monopole-dipole (for zero spin) or monopole-quadrupole model (for fast spin) describes the differential charging potential distribution due to blocked photoelectrons. It is shown that these cases are similar to a more general multipole potential field in that the surface node potentials satisfy an approximate linear relation. These cases are all driven by the shade side charging so that the onset for charging is approximately the same in sunlight or eclipse if conduction currents through the spacecraft can be neglected. If conduction currents are important, potential barriers can develop on the dark side, leading to suppression of the secondary emission currents and modification of charging onset. The results were briefly compared with observations. Another important reason for negative charging concerns reflectance. Highly reflective mirrors generate substantially reduced photoemission so that current balance can be achieved without barrier formation. The onset for charging in this case depends strongly on the reflectivity. The critical temperature for charging of surface materials under space substorm conditions with different ratios of photoemission current to electron ambient current, corresponding to varying satellite surface reflectivity values, was calculated. Numerical results, which show that with substantially reduced photoemission, highly reflective surfaces charge in sunlight with the critical temperature for onset decreasing with increasing reflectivity, are presented.

show abstract

Section: Competition With Ambient Electron Currentmentioning

confidence: 99%

“…In (19), the first term J o · dA relates to the area perpendicular to the solar radiation and is straightforward. In the third term, i.e., (1 − R), the reflectivity R is represented by the rough fit given in (17). The second term Y is more complex.…”

Section: Competition With Ambient Electron Currentmentioning

confidence: 99%

Aspects of Spacecraft Charging in Sunlight

Lai

Tautz

2006

IEEE Trans. Plasma Sci.

View full text Add to dashboard Cite

show abstract

“…It is clear that additional processes are at work, since first order calculations of the ambient, secondary, and photocurrents produce net postive currents to a magnetospheric satellite. Direct evidence from measured particle spectra, and inferred evidence from modeling efforts, suggest that the formation of potential barriers around the satellite suppress photoemission when the electron environment is sufficiently intense (Whipple, 1976a,b;Oeaen et al, 1981;Mandell et al, 1978). Generally, a given environment is expected to charge a satellite about an order of magnitude more in eclipse than in sunlight.…”

Section: Introductionmentioning

confidence: 99%

The importance of accurate secondary electron yields in modeling spacecraft charging

Katz¹,

Mandell²,

Jongeward³

et al. 1986

J. Geophys. Res.

Self Cite

View full text Add to dashboard Cite

Spacecraft charging has commonly been attributed to electrons with several kilovolts of energy impinging upon spacecraft surfaces. Recent experimental evidence from the SCATHA satellite has shown that charging correlates well with electrons of energies greater than 30 keV. In this paper it is shown that the SCATHA observations are consistent with the model of charging in which a satellite is immersed in a Maxwellian plasma, particle collection is orbit limited, and dominant surface effects are the emission of secondary and backscattered electrons. The energy dependence of the secondary yield for multikilovolt incident electrons determines the charging threshold. In the past, inadequate representations of the secondary yield have led experimenters to question the validity of the charging model. The accuracy of the secondary electron yield formulation based on electron stopping power, such as the one in NASA Charging Analyzer Program (NASCAP), gives good agreement with the SCATHA results. A Maxwellian representation of the magnetospheric plasma is justified by choosing effective temperatures and densities that minimize the error in calculating charging current densities.

show abstract

“…But we might still expect that the potentials outside the satellite would be approximately Laplacian and that a p otential b arrier w ould form t o s uppress p hotoemission. C omputer s imulations w ith m ore complex satellite models have indicated the occurrence of this effect [Mandell, et al, 1978;Rubin, etal, 1979].…”

Section: Non-ideal Charging and Comparison With Lanl Datamentioning

confidence: 99%

Analytic Models for Sunlight Charging of a Rapidly Spinning Satellite

Tautz¹

2003

View full text Add to dashboard Cite

The Decrease in Effective Photocurrents Due to Saddle Points in Electrostatic Potentials near Differentially Charged Spacecraft

Cited by 41 publications

References 3 publications

Aspects of Spacecraft Charging in Sunlight

Aspects of Spacecraft Charging in Sunlight

The importance of accurate secondary electron yields in modeling spacecraft charging

Analytic Models for Sunlight Charging of a Rapidly Spinning Satellite

Contact Info

Product

Resources

About