SCATHA survey of high‐level spacecraft charging in sunlight

Mullen, E.G.; Gussenhoven, M. S.; Hardy, D. A.; Aggson, T. A.; Ledley, B. G.; Whipple, E. C.

doi:10.1029/ja091ia02p01474

Cited by 134 publications

(78 citation statements)

References 19 publications

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“…Surprisingly, high-level negative voltage (negative kilovolts) charging of spacecraft surfaces is sometimes observed in daylight [13]- [15]. How can high-level negative potential charging occur on spacecraft surfaces in spite of the dominant photoelectron current?…”

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confidence: 99%

Aspects of Spacecraft Charging in Sunlight

Lai

Tautz

2006

IEEE Trans. Plasma Sci.

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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.

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confidence: 99%

Aspects of Spacecraft Charging in Sunlight

Lai

Tautz

2006

IEEE Trans. Plasma Sci.

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“…The first reports of high level spacecraft charging were those for Applications Technology Satellite (ATS) 5 [Deforest, 1972]. Similar events were subsequently noted on ATS 6 and P78-2 (SCATHA) [Olsen and Purvis, 1983;Mullen et al 1986].…”

Section: Spacecraft Chargingmentioning

confidence: 76%

Spacecraft‐generated ions

Olsen¹,

Norwood²

1991

J. Geophys. Res.

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Electrostatic analyzer measurements of ions on the SCATHA satellite show evidence of locally generated ions. These measurements come during periods of large negative charging (~-100 to -10,000 V) at or near geosynchronous altitude. Ions are observed at energies below the satellite potential, which, in the absence of scattering, must have been generated on or near the satellite surface. Differential charging measurements from the Surface Satellite Potential Monitor indicated that there were surfaces with the proper magnitude of differential charging to provide a source for the observed ions. Application of the Sigmund-Thompson theories on sputtering show that ambient 10-to100-keV O+ on glass should provide a yield of 0.5 to 1.0 particles per incident ion. Roughly 2-4% of this yield is ionized. This is sufficient to explain the flux levels observed. Particle tracking using the NASA Charging Analyzer Program (NASCAP) showed that the energies measured provided a sweep of trajectories along the satellite surface, but no specific source was identified.

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“…Instead, plasma parameters must be measured experimentally. The particle detectors on the ATS 17,18,19 and SCATHA 20 spacecraft have measured plasma variations between 5-10 eV and 50-80 eV approximately, for 50 complete days at 1 to 10 minute resolution from 1969 through 1980, bracketing one solar cycle.…”

Section: Geo Plasma Environmentmentioning

confidence: 99%

Study of Interspacecraft Coulomb Forces and Implications for Formation Flying

King

Parker

Deshmukh

et al. 2003

Journal of Propulsion and Power

105

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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 ten meters. This paper investigates the effects of spacecraft charging on the dynamics of very closely spaced formations. 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, this paper shows the potential t o develop disruptive inter-spacecraft Coulomb forces and torques with magnitude comparable to candidate formation-keeping thrusters over distances of tens of meters. Owing to the unexpectedly large interaction forces, the paper also explores the concept of purposely charging spacecraft to affect formation-keeping Coulomb forces. Analytic methods are developed that show the existence of static equilibrium formations in Earth orbit using only inter-vehicle Coulomb forces for onetwo -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 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 time scale, and imply specific impulse that can be as high as 10 13 seconds.

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SCATHA survey of high‐level spacecraft charging in sunlight

Cited by 134 publications

References 19 publications

Aspects of Spacecraft Charging in Sunlight

Aspects of Spacecraft Charging in Sunlight

Spacecraft‐generated ions

Study of Interspacecraft Coulomb Forces and Implications for Formation Flying

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