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| Titel |
Analytic models for a spherical satellite charging in sunlight at any spin rate |
| VerfasserIn |
M. Tautz, S. T. Lai |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 24, no. 10 ; Nr. 24, no. 10 (2006-10-20), S.2599-2610 |
| Datensatznummer |
250015653
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| Publikation (Nr.) |
 copernicus.org/angeo-24-2599-2006.pdf |
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| Zusammenfassung |
| We present analytic models for the steady state potential
distributions surrounding a spinning, dielectric-coated, spherical
spacecraft charging in sunlight. The sun direction is assumed to lie in the
satellite bellyband plane, perpendicular to the spin axes. The models are
based on a multipole expansion of Laplacian potentials external to the
spacecraft surface. The combination of monopole potentials along with the
dipole or quadrupole contributions produce potential barriers which form at
the satellite surface. These barriers can block escaping photoelectrons and
lead to current balance, allowing sunlight charging to high negative levels.
In a previous treatment, analytic models were limited to fast spin relative
to differential charging rates so that the solutions had azimuthal symmetry
around the spin axes. By introducing an associated Legendre term into the
potential expansion, the azimuthal symmetry is removed, and the models can
be developed to encompass any spin rate. The analysis turns up three
functions of spin rate which are only known at the spin limits, but the
characteristics of the charging of a rotating sphere can be explored using
approximate forms which represent the basic trends. For finite spin, the
sunlit side charges less (negatively) than the shade side which is in
contrast to the fast spin case, where these two potentials are equal. Also,
for finite spin, differential charging develops perpendicular to the sun and
spin axis directions, due to the transverse motion. This transverse charging
occurs at all finite spin rates, disappearing only at the zero and infinite
spin limits. There is a correlated lag angle between the direction of
maximum sheath radius and the sun line. Plots are given to illustrate the
potential distributions representing barrier dominated sunlight charging of
a spinning dielectric coated spherical satellite. |
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